Battery cell, battery device and power-consuming device

Abstract

Battery cell comprising an electrode arrangement, wherein the electrode arrangement comprises the following: a positive electrode sheet comprising a positive electrode current collection section and a positive electrode film layer, wherein the positive electrode film layer is arranged on at least one side of the positive electrode current collection section along the thickness direction of the positive electrode current collection section, wherein the positive electrode film layer comprises a positive electrode active material, wherein the positive electrode active material comprises a lithium-containing phosphate with an olivine structure;and a negative electrode sheet comprising a negative electrode tab, a negative electrode current collection section and a negative electrode film layer, wherein the negative electrode film layer is arranged on at least one side of the negative electrode current collection section along the thickness direction, the negative electrode film layer contains a negative electrode active material, wherein the negative electrode tab is connected to at least one side of the negative electrode current collection section along a first direction, ; wherein the negative electrode film layer comprises two ends opposite each other along the first direction, wherein the negative electrode film layer comprises a first region and a second region, wherein the first region comprises one of the two ends facing the negative electrode tab, wherein the ratio of the dimension of the first region along the first direction to the dimension of the negative electrode film layer along the first direction is 0.05 to 0.20, the negative electrode active material of the first region comprises artificial graphite and natural graphite, wherein the first direction is perpendicular to the thickness direction.

Description

Technical field

[0001] The present application relates to a battery cell, a battery device and a power-consuming device. State of the art

[0002] Lithium-ion batteries possess characteristics such as high capacity and long lifespan, and are therefore frequently used in electronic devices such as mobile phones, laptops, e-bikes, electric cars, electric aircraft, electric ships, and power tools. As the applications of lithium-ion batteries expand, higher demands are placed on their performance, for example, in terms of cycle life and operational reliability. Disclosure of the invention

[0003] The present application provides a battery cell, a battery device and a power-consuming device that can improve the cycle performance and operational reliability of the battery cell.

[0004] In a first aspect, the present application proposes a battery cell. The battery cell comprises an electrode arrangement, wherein the electrode arrangement includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a positive electrode current collection section and a positive electrode film layer. The positive electrode film layer is arranged on at least one side of the positive electrode current collection section along the thickness direction of the positive electrode current collection section. The positive electrode film layer comprises a positive electrode active material, wherein the positive electrode active material comprises a lithium-containing phosphate with an olivine structure. The negative electrode sheet comprises a negative electrode tab, a negative electrode current collection section, and a negative electrode film layer.The negative electrode film layer is arranged on at least one side of the negative electrode current collector section along the thickness direction and contains a negative electrode active material. The negative electrode tab is connected to at least one side of the negative electrode current collector section along a first direction. The negative electrode film layer comprises two ends opposite each other along the first direction. The negative electrode film layer comprises a first region and a second region. The first region comprises one of the two ends facing the negative electrode tab. The ratio of the dimension of the first region along the first direction to the dimension of the negative electrode film layer along the first direction is 0.05 to 0.20.The negative electrode active material of the first region comprises artificial graphite and natural graphite, with the first direction running perpendicular to the thickness direction.

[0005] As a result, in the embodiments of the present application, the battery cell has a smaller lithium plating area after cyclic charging and discharging, or there may even be no lithium plating at all, which significantly improves the operational reliability of the battery cell and can also improve the cycle performance of the battery cell.

[0006] In some embodiments, the mass fraction of natural graphite relative to the mass of the negative electrode active material in the first area is 5% to 45%, optionally 20% to 45%, which can further improve the operational reliability and cycle performance of the battery cell.

[0007] In some embodiments, the mass fraction of the artificial graphite relative to the mass of the negative electrode active material in the first area is 55% to 95%, which can further improve the operational reliability and cycle performance of the battery cell.

[0008] In some embodiments, the first region comprises a first sublayer and a second sublayer. The first sublayer is arranged on at least one side of the negative electrode current collector section, and the second sublayer is arranged on a side of the first sublayer facing away from the negative electrode current collector section. The first sublayer comprises synthetic graphite and natural graphite, and the second sublayer comprises synthetic graphite, which contributes to improved fast-charging capability.

[0009] In some embodiments, the mass fraction of the artificial graphite in the second sublayer is 30% to 70% relative to the mass of the negative electrode active material in the first area, which can further improve the operational reliability and cycle performance of the battery cell.

[0010] In some embodiments, the density of the first sublayer is greater than or equal to the density of the second sublayer when the battery cell is at 100% charge. In the embodiments of the present application, the first sublayer has a higher density, while the second sublayer has a lower density. This can improve the tortuosity in the first region, thereby improving the charging process, in particular reducing concentration polarization during fast charging and lowering the risk of lithium plating in the first region.

[0011] In some embodiments, the compaction density of the first sublayer is 1.25 g / cm³. 3 up to 1.65 g / cm³ 3 , when the battery cell is at 100% charge.

[0012] In some embodiments, the compaction density of the second sublayer is 1.1 g / cm³. 3 up to 1.5 g / cm³ 3 , when the battery cell is at 100% charge.

[0013] In some embodiments, the first sublayer comprises a lithium-containing binder, wherein the mass fraction of the lithium-containing binder is 0.1% to 3% relative to the mass of the first sublayer. The lithium in the lithium-containing binder can form a delocalized structure with a graphite material, which contributes to improving the kinetic performance, particularly at low temperatures and room temperature.

[0014] In some embodiments, the second sublayer comprises a lithium-containing binder, wherein the mass fraction of the lithium-containing binder is 0.1% to 3% relative to the mass of the second sublayer. The lithium in the lithium-containing binder can form a delocalized structure with a graphite material, which contributes to improving the kinetic performance, particularly at low temperatures and room temperature.

[0015] In some embodiments, the mass fraction of the element lithium in the lithium-containing binder is 4% to 10%.

[0016] In some embodiments, the lithium-containing binder comprises a copolymer of lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate, wherein the copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer, wherein the molar percent of the lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0017] In some embodiments, the volume-averaged particle size Dv50 of the artificial graphite in the first range is 7 µm to 15 µm.

[0018] In some embodiments, the volume-averaged particle size Dv50 of the natural graphite in the first range is 7 µm to 15 µm.

[0019] In some embodiments, the specific surface area of ​​the natural graphite in the first area is larger than the specific surface area of ​​the artificial graphite in the first area, which contributes to improving fast charging performance.

[0020] In some embodiments, the specific surface area of ​​the natural graphite in the first region is 1.5 m². 2 / g up to 4.5 m 2 / G.

[0021] In some embodiments, the specific surface area of ​​the artificial graphite in the first region is 0.7 m². 2 / g up to 3.0 m 2 / G.

[0022] In some embodiments, the ratio of the dimension of the first region along the first direction to the dimension of the negative electrode film layer along the first direction is 0.05 to 0.20, optionally 0.10 to 0.20. If the proportion of the first region is within the aforementioned range, the risk of lithium plating is lower, which can further improve the cycle performance and operational reliability of the battery cell.

[0023] In some embodiments, the electric r The electrode arrangement is a stacked structure, with the positive electrode sheet and the negative electrode sheet stacked along the thickness direction.

[0024] In some embodiments, the electrode arrangement has a stacked structure, with the negative electrode tabs connected to both sides of the negative electrode current collecting section along the first direction, and the first region comprising two ends.

[0025] In some embodiments, the electrode arrangement has a stacked structure, wherein the negative electrode tab is connected to one side of the negative electrode current collecting section along the first direction, and the first region is one of the two ends facing the negative electrode tab.

[0026] In some embodiments, the electrode arrangement has a wound structure, with the positive electrode sheet and the negative electrode sheet wound in one direction.

[0027] In some embodiments, the negative electrode tab is connected to one side of the negative electrode current collecting section along the first direction, and the first region includes two ends.

[0028] In some embodiments, the lithium plating area of ​​the negative electrode film layer after 500 cycles of cyclic charging and discharging of the battery cell is 0% to 13.5%, optionally 0% to 6%, based on the surface area of ​​the negative electrode film layer.

[0029] In some embodiments, the positive electrode sheet further comprises an insulating layer, wherein the insulating layer is arranged on the positive electrode current collector section and connected to the positive electrode film layer. The insulating layer and the first region are arranged opposite each other along the thickness direction, and the insulating layer can further reduce the risk of lithium plating.

[0030] In some embodiments, the negative electrode film layer further comprises a second region, the second region being arranged continuously with the first region. The second region comprises a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is arranged on the surface of the negative electrode current collector section and comprises a carbon-based material. The second negative electrode film layer is connected to the side of the first negative electrode film layer facing away from the negative electrode current collector section and comprises a carbon-based material. The carbon-based material in the first negative electrode film layer and the carbon-based material in the second negative electrode film layer each independently comprise graphite particles.The volume-averaged particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume-averaged particle size Dv50 of the graphite particles in the second negative electrode film layer. The graphite particles comprise synthetic graphite and a carbon coating layer. The synthetic graphite includes secondary particles, and its surface is coated with the carbon coating layer.

[0031] Therefore, the particle size in the first and second negative electrode film layers differs in the embodiments of the present application, which can improve the fast-charging performance of the battery cell. In particular, during fast charging, the overpotential of the second negative electrode film layer is typically higher, and the bottleneck during fast charging is mainly in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transport path of the lithium ions, improve fast-charging performance, and enhance lithium plating on the surface of the negative electrode sheet.

[0032] In some embodiments, the graphitization degree of the graphite particles ranges from 92.0% to 94.5%. When the graphitization degree of the graphite particles is within the aforementioned range, the graphite particles exhibit excellent conductivity, which reduces heat generation from the negative electrode sheet and the battery cell, and improves the fast-charging performance of the battery cell.

[0033] In some embodiments, the mass fraction of the carbon coating layer is 2% to 5%, based on the mass of the graphite particles. If the mass fraction of the carbon coating layer is within the aforementioned range, the internal resistance of the negative electrode sheet can be further reduced and the amount of heat generated by the battery cell can be decreased.

[0034] In some embodiments, the powder compaction density of the graphite particles at 20000 N is 1.5 g / cm³.3 up to 1.85 g / cm³ 3 If the powder compaction density of the graphite particles at 20000 N is within the range mentioned above, the energy density of the battery cell can be increased, and because the negative electrode active material can be stacked more densely in the negative electrode film layer, the contact resistance between the particles is lower, which can further reduce the resistance of the electrode sheet and thus decrease heat generation.

[0035] In some embodiments, the compaction density of the first negative electrode film layer is 1.15 g / cm³. 3 up to 1.36 g / cm³ 3 , when the battery cell is at 100% charge.

[0036] In some embodiments, the compaction density of the second negative electrode film layer is 1.15 g / cm³. 3 up to 1.36 g / cm³ 3 , when the battery cell is at 100% charge.

[0037] In some embodiments, the volume-averaged particle size Dv50 of the graphite particles in the first negative electrode film layer is 9.5 µm to 18.5 µm. If the volume-averaged particle size Dv50 of the negative electrode active material in the first negative electrode film layer is within the aforementioned range, the fast charging performance can be improved.

[0038] In some embodiments, the volume-averaged particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8 µm to 14.3 µm. If the volume-averaged particle size Dv50 of the negative electrode active material in the second negative electrode film layer is within the aforementioned range, the tortuosity of lithium ion transport can be reduced and the fast-charging performance of the battery cell improved.

[0039] In some embodiments, the first negative electrode film layer further comprises a first lithium-containing binder and the second negative electrode film layer further comprises a second lithium-containing binder, wherein the mass fraction of the first lithium-containing binder, based on the mass of the first negative electrode film layer, is less than or equal to the mass fraction of the second lithium-containing binder, based on the mass of the second negative electrode film layer.

[0040] Therefore, in the embodiments of the present application, the mass fraction of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the second lithium-containing binder provides a relatively larger number of freely moving lithium ions for the second negative electrode film layer, which can further improve the fast charging performance of the battery cell.

[0041] In some embodiments, the mass fraction of the first lithium-containing binder is 0.1% to 3% based on the mass of the first negative electrode film layer. If the mass fraction of the first lithium-containing binder is within the aforementioned range, the deintercalation / intercalation rate of the lithium ions can be increased, thereby improving the fast-charging performance of the battery cell.

[0042] In some embodiments, the mass fraction of the second lithium-containing binder, relative to the mass of the second negative electrode film layer, is 0.1% to 3%. If the mass fraction of the element lithium in the second lithium-containing binder is within the aforementioned range, the deintercalation and intercalation rate of the lithium ions is increased, thereby improving the fast-charging performance of the battery cell.

[0043] In some embodiments, the mass fraction of elemental lithium in the first lithium-containing binder is 3% to 10%. If the mass fraction of elemental lithium is within the aforementioned range, the number of lithium ions freely moving in the negative electrode film layer can be relatively large, thereby further reducing the distance over which the lithium ions diffuse to the surface of the negative electrode film layer, increasing the deintercalation and intercalation rate of the lithium ions, and improving the fast-charging performance of the battery cell.

[0044] In some embodiments, the mass fraction of elemental lithium in the second lithium-containing binder is 3% to 10%. If the mass fraction of elemental lithium is within the aforementioned range, the number of lithium ions freely moving in the negative electrode film layer can be relatively large, thereby further reducing the distance over which the lithium ions diffuse to the surface of the negative electrode film layer, increasing the deintercalation and intercalation rate of the lithium ions, and improving the fast-charging performance of the battery cell.

[0045] In some embodiments, the first lithium-containing binder comprises a copolymer of lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate, wherein the copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer, with the molar percentage of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer being 30% to 50%, 15% to 45%, 5% to 20%, and 20% to 35%, respectively. Consequently, the lithium-containing binder made from the above material can provide a certain number of lithium ions for the negative electrode film layer, which improves the fast-charging performance of the battery cell. Furthermore, it does not swell as readily during the charging and discharging process and exhibits a stable structure, thereby improving the cycle life of the negative electrode film layer during fast charging and discharging.

[0046] In some embodiments, the second lithium-containing binder comprises a copolymer of lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate, wherein the copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer, wherein the molar percent of the lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0047] Therefore, the lithium-containing binder from the above material can provide a specific number of lithium ions for the negative electrode film layer, thus improving the fast-charging performance of the battery cell. Furthermore, it does not swell as easily during charging and discharging and exhibits a stable structure, thereby improving the cycle life of the negative electrode film layer during fast charging and discharging.

[0048] In some embodiments, the one-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm². 2 up to 170 mg / 1540.25 mm 2 If the one-sided coating weight of the negative electrode film layer is within the range mentioned above, the amount of heat generated per unit area of ​​the negative electrode sheet is not too large, so that the energy density of the battery cell can be increased at the same time.

[0049] In some embodiments, the negative electrode sheet further comprises a conductive layer of the negative electrode, wherein the conductive layer of the negative electrode is located between the negative electrode film layer and the negative electrode current collection section. The conductive layer of the negative electrode can further improve the conductivity of the negative electrode sheet and reduce the heat generation of the negative electrode sheet, thereby reducing the amount of heat generated by the battery cell.

[0050] In some embodiments, the thickness of the conductive layer of the negative electrode is 0.1 µm to 2 µm. The conductive layer of the negative electrode can further improve the conductivity of the negative electrode sheet and reduce the heat generation of the negative electrode sheet, thereby reducing the amount of heat generated by the battery cell.

[0051] In some embodiments, the conductive layer of the negative electrode comprises a conductive material, and the conductive material of the negative electrode comprises one or more of superconducting carbon, conductive graphite, carbon black, carbon black, Ketjen carbon black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive material of the negative electrode in the conductive layer of the negative electrode can improve the conductivity of the conductive layer of the negative electrode, thereby improving the conductivity of the negative electrode sheet and reducing the amount of heat generated by the battery cell.

[0052] In some embodiments, the conductive layer of the negative electrode comprises a negative electrode binder, wherein the negative electrode binder comprises one or more of the following: styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan. The negative electrode binder in the conductive layer of the negative electrode can improve the bonding performance between the negative electrode current collector and the negative electrode film layer and enhance the structural stability of the negative electrode sheet.

[0053] In some embodiments, the compaction density of the positive electrode film layer is 2.50 g / cm³. 3 up to 2.80 g / cm³ 3, when the battery cell is at 100% charge. If the packing density of the positive electrode film layer is within the aforementioned range, this is advantageous for increasing the energy density of the battery cell; and because the positive electrode active material in the positive electrode film layer is relatively densely packed, and the contact resistance between the particles is low, the resistance of the electrode sheet can be further reduced, thereby decreasing heat generation.

[0054] In some embodiments, the one-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm². 2 up to 370 mg / 1540.25 mm 2If the one-sided coating weight of the positive electrode film layer is within the range mentioned above, the amount of heat generated per unit area of ​​the positive electrode sheet is not too large, so that the energy density of the battery cell can be increased at the same time.

[0055] In some embodiments, the compaction density of the positive electrode film layer is 2.55 g / cm³. 3 up to 2.70 g / cm³ 3 , when the battery cell is at 100% charge. If the packing density of the positive electrode film layer is within the aforementioned range, this is advantageous for increasing the energy density of the battery cell; and because the positive electrode active material in the positive electrode film layer is relatively densely packed, and the contact resistance between the particles is low, the resistance of the electrode sheet can be further reduced, thereby decreasing heat generation.

[0056] In some embodiments, the one-sided coating weight of the positive electrode film layer is 240 mg / 1540.25 mm². 2 up to 330 mg / 1540.25 mm 2 If the one-sided coating weight of the positive electrode film layer is within the range mentioned above, the amount of heat generated per unit area of ​​the positive electrode sheet is not too large, so that the energy density of the battery cell can be increased at the same time.

[0057] In some embodiments, the powder compaction density of the positive electrode active material at 30000 N is 2.46 g / cm³. 3 up to 2.8 g / cm³ 3If the powder compaction density of the positive electrode active material at 30000 N is within the range mentioned above, the energy density of the battery cell can be increased, and because the positive electrode active material can be stacked more densely in the positive electrode film layer, the contact resistance between the particles is lower, which can further reduce the resistance of the electrode sheet and thus decrease heat generation.

[0058] In some embodiments, the lithium-containing phosphate with an olivine structure comprises phosphate particles and a coating layer, wherein the coating layer coats the phosphate particles and contains one or more of C, Fe, Ti, Zr, Hf, Ge, and Sn. The surface coating of the phosphate particles with the coating layer can improve the conductivity of the lithium-containing phosphate with an olivine structure, reduce the powder resistance of the material, and increase the migration rate of the lithium ions, thereby reducing the amount of heat generated by the battery cell.

[0059] In some embodiments, the phosphate particles comprise a compound with the general formula of Li x1 A y1 Me a M3P 1-c X c Y z, where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3 and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5 and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A comprises one or more of Na, K and Mg, Me comprises one or more of Mn, Fe, Co and Ni, M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La and Ce, X comprises one or more of S, Si, Cl, B, C, and N, and Y comprises one or more of O and F. The phosphate particles exhibit excellent cycle stability, which has a positive effect on improving the cycle performance of the battery cell.

[0060] In some embodiments, the coating layer comprises a fast ion conductor with the general formula of Li 3-d Fe 2-d M2 d (PO x2 ) y2, where M2 comprises one or more of Ti, Zr, Hf, Ge and Sn, and 0 ≤ d ≤ 1, 0 < x2 < 5, 0 < y2 < 4. By surface coating phosphate particles with the fast ion conductor, the transport rate of lithium ions during multiple deintercalations and intercalations of lithium ions at the positive electrode can be significantly increased, the ionic conductivity of the positive electrode active material improved, and thereby the capacity per gram increased and the energy density of the corresponding battery cell further increased.

[0061] In some embodiments, the graphitization degree of the positive electrode active material is 0.15 to 0.32 and optionally 0.19 to 0.26. If the graphitization degree of the positive electrode active material is within the aforementioned range, this is advantageous for improving the conductivity of the positive electrode active material, reducing the heat generation of the positive electrode sheet, and thus the amount of heat generated by the battery cell.

[0062] In some embodiments, the mass fraction of the element carbon in the lithium-containing phosphate with olivine structure is 1% to 2%, and the specific surface area of ​​the lithium-containing phosphate with olivine structure is 5 m². 2 / g up to 18 m 2 / g, optional 7.5 m 2 / g up to 14 m 2 / G.

[0063] Therefore, in the embodiments of the present application, the material in which the above-mentioned mass fraction of the element carbon is combined with the above-mentioned specific surface area promotes the effective contact between the electrolyte solution and the lithium-containing phosphate with olivine structure, which promotes the transport of lithium ions at the phase interface.

[0064] In some embodiments, the lithium-containing phosphate with an olivine structure is in granular form, and its volume distribution particle size meets the following criteria: 1 µm ≤ Dv50 ≤ 2 µm, 0.4 µm ≤ Dv10 ≤ 0.7 µm. The particle size of the lithium-containing phosphate with an olivine structure is relatively small, resulting in a short deintercalation and intercalation pathway of lithium ions in the positive electrode active material and low heat generation. Furthermore, the particle size of the aforementioned positive electrode active material is not too small, and agglomeration is practically non-existent during processing and manufacturing, thus maintaining stable performance of the positive electrode active material.

[0065] In some embodiments, the lithium-containing phosphate with an olivine structure is in granular form and comprises secondary particles, wherein the secondary particles contain several primary particles, the average particle size of which is 200 nm to 500 nm. The average particle size of the primary particles is relatively small, resulting in a short deintercalation and intercalation path of lithium ions in the positive electrode active material and a low amount of heat generation.

[0066] In some embodiments, the positive electrode film layer further comprises one or more ternary materials, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrite. The aforementioned materials can add lithium ions to the positive electrode film layer to compensate for the irreversible lithium ion loss in the system and to increase the capacity, which in turn increases the energy density of the battery cell.

[0067] In some embodiments, the thickness of the positive electrode current collector is 10 µm to 15 µm. If the thickness of the positive electrode current collector is within the aforementioned range, the positive electrode current collector exhibits relatively excellent current conductivity and enables a higher energy density of the battery cell.

[0068] In some embodiments, the positive electrode sheet also includes a conductive layer of the positive electrode, wherein the conductive layer of the positive electrode is located between the positive electrode film layer and the positive electrode current collector. The conductive layer of the positive electrode can further improve the conductivity of the positive electrode sheet and reduce the heat generation of the positive electrode sheet, thereby reducing the amount of heat generated by the battery cell.

[0069] In some embodiments, the thickness of the conductive layer of the positive electrode is 0.1 µm to 2 µm. If the thickness of the conductive layer of the positive electrode is within the aforementioned range, the conductivity of the positive electrode sheet can be further improved and the heat generation of the positive electrode sheet reduced, thereby reducing the heat generation of the battery cell and simultaneously increasing the energy density of the battery cell.

[0070] In some embodiments, the conductive layer of the positive electrode comprises one or more positive electrode conductive elements and positive electrode binders. The positive electrode conductive element in the conductive layer of the positive electrode can improve the conductivity of the positive electrode layer, thereby improving the conductivity of the positive electrode sheet and reducing the amount of heat generated by the battery cell. The positive electrode binder in the conductive layer of the positive electrode can improve the bonding performance between the positive electrode current collector and the positive electrode film layer, thus improving the structural stability of the positive electrode sheet.

[0071] In some embodiments, the conductive medium of the positive electrode comprises one or more of superconducting carbon, conductive graphite, acetylene carbon black, carbon black, Ketjen carbon black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0072] In some embodiments, the binder of the positive electrode comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylate resin.

[0073] In some embodiments, the charging time for the battery cell from 10% to 80% charge is 5 to 10.5 minutes. The charging speed of the battery cell is faster, which further improves the fast-charging capability.

[0074] In a second aspect, the present application proposes a battery device comprising several battery cells according to any embodiment of the first aspect of the present application.

[0075] In some embodiments, the charging time for the battery device from 10% to 80% charge is 5 to 10.5 minutes. The faster charging speed of the battery device primarily contributes to improved fast-charging capability.

[0076] In a third aspect, the present application proposes a power-consuming device comprising a battery device according to any embodiment of the second aspect of the present application. Brief description of the drawings

[0077] To better illustrate the technical solutions in the embodiments of the present application, a brief description of the drawings required in these embodiments is given below. Of course, the drawings described below represent only some embodiments of the present application, and other drawings can be created by a person skilled in the art based on these drawings without any creative effort. Fig. Figure 1 is a schematic representation of the structure of a battery cell according to some embodiments of the present application, Fig. Figure 2 is a schematic exploded view of the battery cell according to some embodiments of the present application, Fig. Figure 3 is a schematic representation of the structure of an electrode arrangement of the battery cell according to some embodiments of the present application; Fig. Figure 4 is a schematic representation of the structure of a negative electrode sheet of an electrode arrangement according to some embodiments of the present application; Fig. Figure 5 is a schematic representation of the structure of a negative electrode sheet of an electrode arrangement according to some other embodiments of the present application; Fig. Figure 6 is a schematic representation of the structure of a negative electrode sheet of an electrode arrangement according to some other embodiments of the present application; Fig. Figure 7 is a schematic representation of the structure of a positive electrode sheet of an electrode arrangement according to some embodiments of the present application; Fig. Figure 8 is a schematic representation of the structure of the electrode arrangement of the battery cell according to other embodiments of the present application; Fig.Figure 9 is a schematic representation of the unfolded structure of a negative electrode sheet of an electrode arrangement according to some embodiments of the present application; Fig. Figure 10 is a schematic representation of the structure of a battery module according to some embodiments of the present application, Fig. Figure 11 is a schematic representation of the structure of a battery pack according to some embodiments of the present application, Fig. Figure 12 is a schematic representation of the structure of a power-consuming device according to some embodiments of the present application.

[0078] The drawings are not necessarily to scale. Reference symbol list:

[0079] X. Thickness direction; Y. First direction; Z. Second direction; 1. Power-consuming device; 2. Battery pack; 3. Controller; 4. Motor; 5. Housing; 5a. First housing section; 5b. Second housing section; 5c. Receiving compartment; 6. Battery module; 7. Battery cell; 10. Electrode arrangement; 111. Positive electrode tab; 112. Negative electrode tab; 12. Main body section; 13. Positive electrode sheet; 131. Positive electrode current collection section; 132. Positive electrode film layer; 133. Insulating layer; 14. Negative electrode sheet; 140. First area; 1401. First lower class; 1402. Second lower class; 141. Negative electrode current collection section; 142. Negative electrode film layer; 145. First negative electrode film layer; 146. Second negative electrode film layer; 147. Second section; 15. Separator; 20. Housing; 21. Housing body; 22. End cap; 31. Positive electrode connection; 32. Negative electrode connection. Detailed descriptions

[0080] The following section describes in detail embodiments of a battery cell, a battery device, and a power-consuming device specifically disclosed in the present application, possibly with reference to the drawings. However, an unnecessarily detailed description can be omitted. For example, a detailed description of known facts and a repeated description of essentially the same structure can be avoided. This is to prevent the following description from becoming unnecessarily lengthy, thus facilitating understanding by those skilled in the art. Furthermore, the drawings and the following description serve to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0081] The “range” disclosed in the present application is defined in terms of a lower bound and an upper bound. A given range is defined by selecting a lower bound and an upper bound. The selected lower bound and upper bound define the limits of the specific range. The ranges thus defined may or may not include the end values ​​and may be specified in any combination; that is, any lower bound can be combined with any upper bound to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, then ranges of 60 to 110 and 80 to 120 are also conceivable. Furthermore, if minimum range values ​​of 1 and 2 and maximum range values ​​of 3, 4, and 5 are listed, then all of the following ranges are conceivable: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5.In the present application, unless otherwise specified, a range of numbers "a to b" represents an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the range "0 to 5" means that all real numbers between "0 to 5" are listed therein, and "0 to 5" is simply an abbreviation for these number combinations. Furthermore, if a particular parameter is specified as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0082] Unless otherwise stated, all embodiments and optional embodiments of the present application may be combined to form a new technical solution.

[0083] Unless otherwise stated, all technical features and optional technical features of the present application may be combined to form a new technical solution.

[0084] Unless otherwise stated, all steps of the present application may be carried out sequentially or in any order, but preferably sequentially. For example, a method comprising steps (a) and (b) means that the method may include steps (a) and (b) carried out sequentially, or steps (b) and (a) carried out sequentially. Similarly, if it is mentioned that the method may further include step (c), this means that step (c) may be added in any order. For example, the method may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0085] During the charging process of the battery cell, lithium ions are deintercalated from the positive electrode sheet and migrate to the negative electrode sheet, where they accept electrons and form lithium metal. During lithium metal formation, some lithium ions cannot be intercalated into the negative electrode sheet in time, leading to the deposition and formation of lithium dendrites on its surface. These lithium dendrites can puncture the separator, causing a short circuit between the positive and negative electrodes and impairing the battery cell's operational reliability. Furthermore, the lithium dendrites occupy the space between the electrode sheets, increasing the expansion force of the battery cell and reducing its cycle life.Increasing the charging rate of the battery cell increases the risk of lithium plating in the battery cell, which further degrades the operational reliability of the battery cell and shortens the cycle life of the battery cell.

[0086] Against this background, the battery cell system in the embodiments of the present application is designed in a way that results in essentially no lithium plating or a small lithium plating area after the battery cell cycle. This leads to a significantly improved operational reliability of the battery cell and can also improve its cycle life. Battery cell

[0087] In a first aspect, the embodiments of the present application propose a battery cell.

[0088] As in the Fig.As shown in Figures 1 to 4, the battery cell 7 comprises an electrode assembly 10. The electrode assembly 10 comprises a positive electrode sheet 13 and a negative electrode sheet 14. The positive electrode sheet 13 comprises a positive electrode current collector section 131 and a positive electrode film layer 132. The positive electrode film layer 132 is arranged on at least one side of the positive electrode current collector section 131 along the thickness direction X of the positive electrode current collector section 131. The positive electrode film layer 132 comprises a positive electrode active material, wherein the positive electrode active material comprises a lithium-containing phosphate with an olivine structure. The negative electrode sheet 14 comprises a negative electrode tab 112, a negative electrode current collector section 141, and a negative electrode film layer 142.The negative electrode film layer 142 is arranged on at least one side of the negative electrode current collector section 141 along the thickness direction and contains a negative electrode active material. The negative electrode film layer 142 comprises a first region 140. The negative electrode film layer 142 has two ends opposite each other along the first direction Y. The first region 140 includes one of the two ends facing the negative electrode tab 112. The ratio of the dimension of the first region 140 along the first direction Y to the dimension of the negative electrode film layer 142 along the first direction Y is 0.05 to 0.20. The negative electrode active material of the first region 140 comprises synthetic graphite and natural graphite, with the first direction Y being perpendicular to the thickness direction X.Optionally, the electrode arrangement also includes a separator 15, wherein the separator 15 is located between the positive electrode sheet 13 and the negative electrode sheet 14.

[0089] Optionally, the negative electrode film layer 142 comprises a first region 140 and a second region 147, wherein the first region 140 and the second region 147 are arranged continuously. It can be understood that all regions of the negative electrode film layer 142 except the first region 140 are considered to be the second region.

[0090] In the embodiments of the present application, the end of the negative electrode film layer 142 refers to the end of the negative electrode film layer 142 along the first direction Y; if the first direction Y is parallel to the longitudinal direction of the negative electrode film layer 142, the end of the negative electrode film layer 142 refers to the end of the negative electrode film layer 142 along the longitudinal direction. If the first direction Y is parallel to the lateral direction of the negative electrode film layer 142, the end of the negative electrode film layer 142 refers to the end of the negative electrode film layer 142 along the lateral direction.

[0091] Since the area near the negative electrode tab 112 has a higher current density and the risk of lithium plating is greater, the embodiments of the present application reduce the risk of lithium plating in the first area 140 through a specific design of the first area 140. Specifically, the first area 140 comprises synthetic and natural graphite. The combination of synthetic and natural graphite applications contributes to expanding the diffusion channels for lithium ions, improving the charging performance of the first area 140, and reducing the risk of lithium plating.

[0092] In some embodiments, the mass fraction of natural graphite relative to the mass of the negative electrode active material in the first range is 5% to 45%, optionally 20% to 45%, for example 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or lies within a range consisting of any two of the above values. If the mass fraction of natural graphite is within the above range, this is more likely to improve fast-charging capability and further reduce the risk of lithium plating.

[0093] In some embodiments, the mass fraction of the artificial graphite relative to the mass of the negative electrode active material in the first range is 55% to 95%, for example 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or lies in a range consisting of any two of the above values.

[0094] In some embodiments, the first region 140 in the negative electrode film layer 142 can have a single-layer film structure or a double-layer film structure; the double-layer film structure is optional. For example, the first region 140 comprises a first sublayer 1401 and a second sublayer 1402, wherein the first sublayer 1401 is arranged on at least one side of the negative electrode current collector section 141 and the second sublayer 1402 is arranged on a side of the first sublayer 1401 facing away from the negative electrode current collector section 141. The double-layer arrangement helps to reduce the risk of cracking in the film layer, improve the stability of the film layer structure, and further increase the fast-charging capability.

[0095] In some embodiments, the second region 147 in the negative electrode film layer 142 can have a single-layer film structure or a double-layer film structure; the double-layer film structure is optional. For example, the second region 147 comprises a first negative electrode film layer 145 and a second negative electrode film layer 146, wherein the first negative electrode film layer 145 is arranged on at least one side of the negative electrode current collector section 141, and the second negative electrode film layer 146 is arranged on a side of the first negative electrode film layer 145 facing away from the negative electrode current collector section 141. The double-layer arrangement helps to reduce the risk of cracking in the film layer, improve the stability of the film layer structure, and further increase the fast-charging capability.

[0096] In some embodiments, the negative electrode active material of the first sublayer 1401 comprises natural and synthetic graphite. Natural graphite has a relatively large specific surface area, which is advantageous for increasing the diffusion channels for lithium ions, improving the charging performance of the first sublayer 140, and reducing the risk of lithium plating.

[0097] In some embodiments, the negative electrode active material of the second sublayer 1402 comprises synthetic graphite, which improves fast charging performance.

[0098] In some embodiments, the mass fraction of the artificial graphite in the second sublayer 1402, relative to the mass of the negative electrode active material in the first region 140, is 30% to 70%, for example 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or lies in a range consisting of any two of the above values.

[0099] In some embodiments, the compression density of the first sublayer 1401 is greater than or equal to the compression density of the second sublayer 1402 when the battery cell 7 is at a charge level of 100%.

[0100] If the first region 140 has a thicker coating, it is more prone to severe concentration polarization. In the embodiments of the present application, the first sublayer 1401 has a higher density, while the second sublayer 1402 has a lower density. This can improve the tortuosity in the first region 140, thereby improving the charging process, in particular reducing concentration polarization during fast charging and reducing the risk of lithium plating in the first region 140.

[0101] Optionally, the compaction density of the first sublayer 1401 is 1.25 g / cm³ when battery cell 7 is at 100% charge.3 up to 1.65 g / cm³ 3 , for example 1.25 g / cm² 3 , 1.3 g / cm³ 3 , 1.35 g / cm³ 3 , 1.4 g / cm³ 3 , 1.45 g / cm³ 3 , 1.5 g / cm³ 3 , 1.55 g / cm³ 3 , 1.6 g / cm³ 3 , 1.65 g / cm³ 3 or lies within a range consisting of any two of the values ​​mentioned above.

[0102] Optionally, the compaction density of the second sublayer 1402 is 1.1 g / cm³ when battery cell 7 is at 100% charge. 3 up to 1.5 g / cm³ 3 , for example 1.1 g / cm³ 3 , 1.15 g / cm³ 3 , 1.2 g / cm³ 3 , 1.25 g / cm³ 3 , 1.3 g / cm³ 3 , 1.35 g / cm³ 3 , 1.4 g / cm³ 3 , 1.45 g / cm³ 3 , 1.5 g / cm³ 3 or lies within a range consisting of any two of the above values.

[0103] In some embodiments, the first region 140 comprises a lithium-containing binder, and the mass fraction of the element lithium in the lithium-containing binder is 4% to 10%, for example 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or lies in a range consisting of any two of the above values.

[0104] The lithium in the lithium-containing binder can form a delocalized structure with a graphite material, which contributes to improved kinetic performance, particularly at low and room temperatures. Furthermore, it can improve the fast-charging performance of battery cell 7 and reduce the risk of lithium plating.

[0105] For example, the lithium-containing binder comprises a copolymer of lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate, wherein the copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer, wherein the molar percent of the lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0106] In some embodiments, the first sublayer 1401 comprises a lithium-containing binder, and the mass fraction of the lithium-containing binder, based on the mass of the first sublayer, is 0.1% to 3%, for example 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, or is in a range consisting of any two of the above values.

[0107] In some embodiments, the second sublayer 1402 comprises a lithium-containing binder, and the mass fraction of the lithium-containing binder, based on the mass of the second sublayer, is 0.1% to 3%, for example 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, or is in a range consisting of any two of the above values.

[0108] In some embodiments, the volume-averaged particle size Dv50 of the artificial graphite in the first range is 7 µm to 15 µm, for example 7 µm, 8 µm, 9 µm, 10 µm, 11 µm, 12 µm, 13 µm, 14 µm, 15 µm or lies in a range consisting of any two of the above values.

[0109] Optionally, the volume-averaged particle size Dv50 of the artificial graphite of the first sublayer 1401 is 7 µm to 15 µm, for example 7 µm, 8 µm, 9 µm, 10 µm, 11 µm, 12 µm, 13 µm, 14 µm, 15 µm or lies in a range consisting of any two of the above values.

[0110] Optionally, the volume-averaged particle size Dv50 of the artificial graphite of the second sublayer 1402 is 7 µm to 15 µm, for example 7 µm, 8 µm, 9 µm, 10 µm, 11 µm, 12 µm, 13 µm, 14 µm, 15 µm or lies in a range consisting of any two of the above values.

[0111] In some embodiments, the volume-averaged particle size Dv50 of the natural graphite in the first range is 7 µm to 15 µm, for example, 7 µm, 8 µm, 9 µm, 10 µm, 11 µm, 12 µm, 13 µm, 14 µm, 15 µm, or lies within a range consisting of any two of the above values. If the volume-averaged particle size Dv50 of the synthetic graphite is within the above range, the fast-charging capability can be improved and the risk of lithium plating reduced.

[0112] Optionally, the volume-averaged particle size Dv50 of the negative electrode active material of the second sublayer 1402 is less than or equal to the volume-averaged particle size Dv50 of the negative electrode active material of the first sublayer 1401.

[0113] During the charging process of battery cell 7, the chemical reaction zone of the negative electrode active material gradually expands from the vicinity of the separator towards the negative electrode current collector. The volume-averaged particle size Dv50 of the negative electrode active material of the second sublayer 1402 is smaller, and the solid-phase transport capability is stronger, which can improve the fast-charging capability, increase the anode potential of the second sublayer 1402, and reduce the risk of lithium plating in this area.

[0114] In some embodiments, the specific surface area of ​​the natural graphite in the first area 140 is larger than the specific surface area of ​​the artificial graphite in the first area 140, which contributes to improving fast charging performance.

[0115] In some embodiments, the specific surface area of ​​the natural graphite in the first sublayer 1401 is larger than the specific surface area of ​​the artificial graphite in the first sublayer 1401, which contributes to improving fast charging performance.

[0116] Optionally, the specific surface area of ​​the natural graphite of the first sublayer is 1401 1.5 m². 2 / g up to 4.5 m 2 / g, for example 1.5 m 2 / g, 1.6 m 2 / g, 1.7 m 2 / g, 1.8 m 2 / g, 1.9 m 2 / g, 2.0 m 2 / g, 2.1 m 2 / g, 2.2 m 2 / g, 2.3 m 2 / g, 2.4 m 2 / g, 2.5 m 2 / g, 2.6 m 2 / g, 3.0 m 2 / g, 3.5 m 2 / g, 4.0 m 2 / g, 4.5 m 2 / g or lies within a range consisting of any two of the above values.

[0117] Optionally, the specific surface area of ​​the artificial graphite of the first sublayer is 1401 0.7 m². 2 / g up to 3.0 m 2 / g, for example 0.7 m 2 / g, 0.8 m 2 / g, 0.9 m 2 / g, 1.0 m 2 / g, 1.1 m 2 / g, 1.2 m 2 / g, 1.5 m 2 / g, 1.8 m 2 / g, 2.0 m 2 / g, 2.5 m 2 / g, 3.0 m 2 / g or lies within a range consisting of any two of the above values.

[0118] Optionally, the specific surface area of ​​the artificial graphite of the second sublayer is 1402 0.7 m². 2 / g up to 3.0 m 2 / g, for example 0.7 m 2 / g, 0.8 m 2 / g, 0.9 m 2 / g, 1.0 m 2 / g, 1.1 m 2 / g, 1.2 m 2 / g, 1.5 m 2 / g, 1.8 m 2 / g, 2.0 m 2 / g, 2.5 m 2 / g, 3.0 m 2 / g or lies within a range consisting of any two of the above values.

[0119] In the embodiments of the present application, other parameters not mentioned in the first section may be identical to the parameters in the second section.

[0120] In the embodiments of the present application, the lithium plating area can be effectively reduced by a specific design of the first region. In some embodiments, the lithium plating area of ​​the negative electrode film layer, based on the surface area of ​​the negative electrode film layer, after 500 cycles of cyclic charging and discharging of the battery cell, is 0% to 13.5%, for example, 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, or lies in a range consisting of any two of the above values.

[0121] The lithium plating area is less than or equal to 13.5%. After 500 charge and discharge cycles, battery cell 7 has a smaller lithium plating area or even no lithium plating at all, which significantly improves the operational reliability of battery cell 7 and can also extend the cycle life of battery cell 7.

[0122] The upper charging voltage and the discharge cut-off voltage of the battery cell differ depending on the positive electrode active material. For example, if the phosphate material includes lithium iron phosphate, the upper charging voltage can be 3.65 V and the discharge cut-off voltage 2.0 V. If the phosphate material also includes, for example, lithium manganese iron phosphate, the upper charging voltage can be 4.3 V and the discharge cut-off voltage 2.0 V. The charging and discharging of the battery cell is explained below using the example of an upper charging voltage of 3.65 V and a discharge cut-off voltage of 2.0 V:

[0123] The battery cells are charged when the ambient temperature is at a certain level, for example, room temperature (30°C). The charging process includes the following steps:

[0124] A constant current of 5.0 C charges the battery from 0% SOC to 5% SOC; With a constant current of 5.0 C, charging from 5% SOC to 10% SOC is achieved; With a constant current of 5.0 C, charging from 10% SOC to 15% SOC is achieved; With a constant current of 5.0 C, charging from 15% SOC to 20% SOC is achieved; With a constant current of 5.0 C, charging from 20% SOC to 25% SOC is achieved; With a constant current of 5.0 C, charging from 25% SOC to 30% SOC is achieved; With a constant current of 5.0 C, charging from 30% SOC to 35% SOC is achieved; With a constant current of 5.0 C, charging from 35% SOC to 40% SOC is achieved; With a constant current of 4.6 C, it charges from 40% SOC to 45% SOC; With a constant current of 4.3 C, it charges from 45% SOC to 50% SOC; Charging with a constant current of 4.0 C from 50% SOC to 55% SOC; With a constant current of 3.7 C, it charges from 55% SOC to 60% SOC; With a constant current of 3.4 C, it charges from 60% SOC to 65% SOC; With a constant current of 3.1 C, it charges from 65% SOC to 70% SOC; With a constant current of 2.9 C, it charges from 70% SOC to 75% SOC; With a constant current of 2.7 C, it charges from 75% SOC to 80% SOC; With a constant current of 1.8 C, it charges from 80% SOC to 85% SOC; With a constant current of 1.3 C, it charges from 85% SOC to 90% SOC; With a constant current of 0.7 C, it charges from 90% SOC to 95% SOC; With a constant current of 0.33 C, it charges from 95% SOC to 98% SOC; With a constant current of 0.1 C, it charges from 98% SOC to 100% SOC.

[0125] The final voltage of the last charging step in the above charging steps is 3.65 V.

[0126] The discharge strategy is as follows: A constant current of 0.33 C is used to discharge to a final voltage of, for example, 2.0 V.

[0127] According to the cycle strategy described above, battery cell 7 is operated for 500 cycles; subsequently, battery cell 7 is charged to a state of charge (SOC) of 100% following the charging step described above. The negative electrode sheet 14 is removed. The gold color in the negative electrode sheet 14 represents the normal area, and the gray-white coloration represents the lithium plating area. After images are taken with a high-power microscope, the different areas are analyzed. Utilizing the grayscale difference, the lithium plating area is statistically analyzed to obtain the total area of ​​the lithium plating area. The ratio of the total area of ​​the lithium plating area to the surface area of ​​the negative electrode film layer yields the area fraction of the lithium plating area within the negative electrode film layer, i.e., the lithium plating area.

[0128] The electrode arrangement 10 can be a stacked electrode arrangement or a wound electrode arrangement. The differences in the construction of the electrode arrangement 10 lead to differences in the lithium plating process, which are explained in detail below. [Stacked electrode arrangement]

[0129] As in the Fig.Figures 3 to 6 show that when the electrode assembly 10 has a stacked structure, the positive electrode sheet 13 and the negative electrode sheet 14 are stacked along their thickness directions. Optionally, the lithium plating area of ​​the stacked electrode assembly 10 is less than or equal to 13.5%. The thickness directions of the electrode assembly 10, the thickness directions of the positive electrode sheet 13, and the thickness directions of the negative electrode sheet 14 are parallel. The thickness direction of the positive electrode sheet 13 is parallel to the thickness direction of the positive electrode current collector section 131. The longitudinal directions of the electrode assembly 10, the longitudinal directions of the positive electrode sheet 13, and the longitudinal directions of the negative electrode sheet 14 are parallel. The width directions of the electrode assembly 10, the width directions of the positive electrode sheet 13, and the width directions of the negative electrode sheet 14 are parallel. The [figures shown in the figures] Fig. The direction X shown in 3 to 6 indicates that the direction X runs parallel to the thickness direction of the electrode arrangement 10.

[0130] In some embodiments, the negative electrode tab 112 is connected to at least one side of the negative electrode current collecting section 141 along the first direction Y.

[0131] The negative electrode tab 112 is connected on one side of the negative electrode current collector section 141 along the first direction Y, or the negative electrode tabs 112 are connected on both sides of the negative electrode current collector section 141 along the first direction Y. The first direction Y can be parallel to the longitudinal direction of the electrode arrangement 10, or the first direction Y can be parallel to the transverse direction of the electrode arrangement 10. Optionally, the first direction Y is parallel to the longitudinal direction of the electrode arrangement 10. In the Fig.For example, in figures 3 to 6, direction Y represents the longitudinal direction of the electrode arrangement 10, and direction Z represents the lateral direction of the electrode arrangement 10. For example, the negative electrode tabs 112 on both sides of the negative electrode current collector section 141 are connected along the longitudinal direction. Alternatively, for example, the negative electrode tab 112 on one side of the negative electrode current collector section 141 is connected along the lateral direction.

[0132] In some embodiments, the first region 140 comprises one of the two ends that faces the negative electrode tab 112.

[0133] The negative electrode film layer 142 and the negative electrode current collector section 141 are arranged opposite each other along the thickness direction X. The negative electrode current collector section 141 and the negative electrode tab 112 are connected along the first direction Y, and the current can flow along the first direction Y. The current can be concentrated from the negative electrode current collector section 141 towards the negative electrode tab 112. At the end of the negative electrode film layer 142, near the negative electrode tab 112, the electrochemical polarization is greatest, which is susceptible to lithium plating.However, the lithium plating area in the first region 140 is less than or equal to 13.5%, optionally 0% to 6%, for example 13.5%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2.9%, 2.8%, 2.5%, 2.3%, 2.0%, 1.8%, 1.5%, 1.2%, 1%, 0.8%, 0.6%, 0.5%, 0.3%, 0.2%, 0.1%, or lies in a range consisting of any two of the above values. If the lithium plating area is 0, this means that the negative electrode sheet 14 has no lithium plating.

[0134] Optionally, the ratio of the dimension of the first region 140 along the first direction Y to the dimension of the negative electrode film layer 142 along the first direction Y is 0.05 to 0.20, for example 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.15, 0.18, 0.20 or lies in a range consisting of any two of the above values.

[0135] For example, in Fig.5. The negative electrode tab 112 is arranged on one side of the negative electrode current collector section 141. The first region 140 is one of the two ends facing the negative electrode tab 112. L1 specifies the dimension of the first region 140 along the first direction Y, and L0 specifies the dimension of the negative electrode film layer 142 along the first direction Y. L1 / L0 is the ratio of the dimension of the first region 140 along the first direction Y to the dimension of the negative electrode film layer 142 along the first direction Y. This ratio is 0.05 to 0.20, optionally 0.05 to 0.15, or optionally 0.05 to 0.10.

[0136] For example, there are still in Fig.6. The negative electrode tabs 112 are arranged on both sides of the negative electrode current collector section 141. The first region 140 comprises two ends. 2L2 specifies the dimension of each first region 140 along the first direction Y. 2L2 / L0 is the ratio of the dimension of the first region 140 along the first direction Y to the dimension of the negative electrode film layer 142 along the first direction Y. This ratio is 0.05 to 0.20 and optionally 0.10 to 0.20.

[0137] As in Fig. As shown in Figure 7, in some embodiments the positive electrode sheet 13 further comprises an insulating layer 133, wherein the insulating layer 133 is arranged on the positive electrode current collector section 131 and connected to the positive electrode film layer 132. The insulating layer 133 and the first region 140 are arranged opposite each other along the thickness direction.

[0138] Essentially no positive electrode active material is arranged on the insulating layer 133, which helps to increase the dimensions of the negative electrode film layer 142 beyond the positive electrode film layer 132 and thereby further reduce the risk of lithium plating of the negative electrode sheet 14. [Coiled electrode arrangement]

[0139] As in the Fig. As shown in Figures 8 to 10, if the electrode arrangement 10 has a wound structure, the positive electrode sheet 13 and the negative electrode sheet 14 are wound in one direction to form the wound structure. This structure can be cylindrical or flat; the flat structure is optional. The flat structure includes curved and straight areas, with the thickness, length, and width directions of the flat structure being pairwise perpendicular to each other.

[0140] In the electrode arrangement 10 with a wound structure, the end of the negative electrode film layer 142 near the negative electrode tab 112 is exposed to a locally higher current density due to current collection, and can lead to lithium plating. However, in the embodiments of the present application, the lithium plating area in the electrode arrangement 10 with a wound structure is less than or equal to 13.5%, optionally between 0% and 6%.

[0141] In some embodiments, the negative electrode sheet 14 further comprises a negative electrode tab 112, and the negative electrode tab 112 is connected to at least one side of the negative electrode current collector section 141 along the first direction Y, wherein the first direction Y is perpendicular to the thickness direction of the negative electrode sheet 14; the thickness direction of the negative electrode sheet 14 is parallel to the thickness direction of the positive electrode sheet 13. The first direction Y can be parallel to the longitudinal direction of the electrode arrangement 10 or parallel to the lateral direction of the electrode arrangement 10.

[0142] The negative electrode tab 112 is connected on one side of the negative electrode current collecting section 141 along the first direction Y, or the negative electrode tabs 112 are connected on both sides of the negative electrode current collecting section 141 along the first direction Y.

[0143] When the negative electrode tab 112 is connected to one side of the negative electrode current collecting section 141 along the first direction Y, the first region 140 comprises two ends.

[0144] When the negative electrode tabs 112 are connected to both sides of the negative electrode current collection section 141 along the first direction Y, the first region 140 comprises two ends.

[0145] When the negative electrode tab 112 is connected to one side of the negative electrode current collection section 141 along the first direction Y, the gap between the electrode sheets in the curved region of the coiled electrode assembly 10 is larger, the transport path of the active ions in space is longer, leading to increased polarization in the curved region and increasing the risk of lithium plating. In particular, the risk of lithium plating is greater in the portions of the negative electrode film layer 142 in the curved region that face away from the negative electrode tab 112. Typically, after the electrode assembly 10 is installed in the housing of the battery cell 7, the battery cell 7 is placed vertically in the housing to form a battery pack, with the vertical direction parallel to the first direction Y.The negative electrode tab 112 is located along the vertical direction above the first region 140. The heat dissipation capacity at the bottom of the box body is generally better than at the top, resulting in a temperature difference along the vertical direction of the negative electrode tab 14. The end facing away from the negative electrode tab 112 has a lower temperature, which increases polarization during charging and raises the risk of lithium plating. One of the two ends facing the negative electrode tab 112 is more prone to lithium plating due to the higher current density. However, in the embodiments of the present application, the first region 140 is designed with materials, etc., such that the lithium plating area is relatively small.

[0146] Optionally, the ratio of the dimension of the first region 140 along the first direction Y to the dimension of the negative electrode film layer 142 along the first direction Y is 0.05 to 0.20, for example 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.15, 0.20, or lies in a range consisting of any two of the above values. For example, in Fig. 9 The negative electrode tab 112 is arranged on one side of the negative electrode current collector section 141. 2L3 specifies the dimension of the first region 140 along the first direction Y, and L0 specifies the dimension of the negative electrode film layer 142 along the first direction Y. 2L3 / L0 is the ratio of the dimension of the first region 140 along the first direction Y to the dimension of the negative electrode film layer 142 along the first direction Y, where the ratio is 0.05 to 0.20, optionally 0.10 to 0.20. [Negative electrode sheet]

[0147] The negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector and comprising a negative electrode active material. For example, the negative electrode current collector has two surfaces that are opposite each other in its thickness direction, and the negative electrode film layer is arranged on one or both of the two opposite surfaces of the negative electrode current collector.

[0148] The following section explains the materials, structure, and other relevant parameters of the second region in the negative electrode film layer.

[0149] In some embodiments, the compaction density of the second region in the negative electrode film layer is 1.15 g / cm³. 3 up to 1.36 g / cm³ 3 , optional 1.25 g / cm² 3 up to 1.36 g / cm³ 3When the battery cell is at 100% charge, the density of the second region in the negative electrode film layer is, for example, 1.15 g / cm³. 3 , 1.18 g / cm³ 3 , 1.20 g / cm³ 3 , 1.22 g / cm³ 3 , 1.25 g / cm³ 3 , 1.28 g / cm³ 3 , 1.3 g / cm³ 3 , 1.32 g / cm³ 3 , 1.35 g / cm³ 3 , 1.36 g / cm³ 3 or lies within a range consisting of any two of the values ​​mentioned above.

[0150] If the compaction density of the second region in the negative electrode film layer is within the range mentioned above, this is advantageous for increasing the energy density of the battery cell; and because the negative electrode active material in the negative electrode film layer is relatively densely packed, and the contact resistance between the particles is low, the resistance of the electrode sheet can be further reduced, thereby decreasing heat generation.

[0151] In the embodiments of the present application, the state of charge (SOC) of 100% and the state of charge (SOC) of the battery cell are defined as follows:

[0152] The battery cell is charged at a constant charging current of 0.33C up to the upper charging limit voltage and then further charged at a constant voltage down to 0.05C, which corresponds to a 100% state of charge (SOC) of the battery cell. The battery cell is then discharged at a constant discharge rate of 0.33C down to the final voltage, which corresponds to a 70% state of charge (SOC) of the battery cell.

[0153] In the embodiments of the present application, the density of the negative electrode film layer when the battery cell is at 100% charge has a meaning known in the art and can be determined using devices and methods known in the art. The detection method, for example, is the same as the test method for the density of the positive electrode film layer.

[0154] In some embodiments, the one-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm². 2 up to 170 mg / 1540.25 mm 2 , optional 110 mg / 1540.25 mm 2 up to 150 mg / 1540.25 mm 2 For example, the one-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm². 2 , 92 mg / 1540.25 mm 2 , 95 mg / 1540.25 mm 2 , 96 mg / 1540.25 mm 2 , 100 mg / 1540.25 mm 2 , 102 mg / 1540.25 mm 2 , 104 mg / 1540.25 mm 2 , 105 mg / 1540.25 mm 2 , 108 mg / 1540.25 mm 2 , 110 mg / 1540.25 mm 2 , 112 mg / 1540.25 mm 2 , 114 mg / 1540.25 mm 2 , 115 mg / 1540.25 mm 2 , 116 mg / 1540.25 mm 2 , 118 mg / 1540.25 mm 2 , 120 mg / 1540.25 mm 2 , 122 mg / 1540.25 mm 2 , 125 mg / 1540.25 mm 2 , 128 mg / 1540.25 mm 2 , 130 mg / 1540.25 mm 2 , 132 mg / 1540.25 mm2 , 135 mg / 1540.25 mm 2 , 137 mg / 1540.25 mm 2 , 140 mg / 1540.25 mm 2 , 142 mg / 1540.25 mm 2 , 145 mg / 1540.25 mm 2 , 148 mg / 1540.25 mm 2 , 150 mg / 1540.25 mm 2 , 152 mg / 1540.25 mm 2 , 155 mg / 1540.25 mm 2 , 160 mg / 1540.25 mm 2 , 165 mg / 1540.25 mm 2 , 170 mg / 1540.25 mm 2 or lies within a range consisting of any two of the values ​​mentioned above.

[0155] If the one-sided coating weight of the negative electrode film layer is within the range mentioned above, the amount of heat generated per unit area of ​​the negative electrode sheet is not too large, so that the energy density of the battery cell can be increased at the same time.

[0156] In the embodiments of the present application, the one-sided coating weight of the negative electrode film layer has the meaning known in the art and can be determined using devices and methods known in the art, and the detection method is the same as the above test method for the one-sided coating weight of the film layer.

[0157] In some embodiments, the powder resistance of the negative electrode active material in the negative electrode film layer is 0.005 Ω·cm to 0.043 Ω·cm and optionally 0.04 Ω·cm. For example, the powder resistance of the negative electrode active material can be 0.043 Ω·cm, 0.04 Ω·cm, 0.035 Ω·cm, 0.03 Ω·cm, 0.025 Ω·cm, 0.02 Ω·cm, 0.015 Ω·cm, 0.01 Ω·cm, 0.005 Ω·cm, or a range consisting of any two of the above values.

[0158] The powder resistance of the negative electrode active material is relatively low, so the resistance of the negative electrode sheet is relatively low, resulting in less heat generation from the battery cell.

[0159] In the embodiments of the present application, the powder resistance of the negative electrode active material has a meaning known in the art and can be determined using devices and methods known in the art, and the detection method is the same as the test method for the powder resistance of the positive electrode active material.

[0160] In some embodiments, the powder compaction density of the negative electrode active material in the negative electrode film layer under a pressure of 20000 N is 1.5 g / cm³. 3 up to 1.85 g / cm³ 3 , optional 1.55 g / cm² 3 up to 1.65 g / cm³ 3For example, the powder compaction density of the negative electrode active material under a pressure of 20000 N is 1.5 g / cm³. 3 , 1.55 g / cm³ 3 , 1.6 g / cm³ 3 , 1.65 g / cm³ 3 , 1.7 g / cm³ 3 , 1.75 g / cm³ 3 , 1.8 g / cm³ 3 , 1.85 g / cm³ 3 or lies within a range consisting of any two of the values ​​mentioned above.

[0161] If the powder compaction density of the negative electrode active material at 20000 N is within the range mentioned above, the energy density of the battery cell can be increased, and because the negative electrode active material can be stacked more densely in the negative electrode film layer, the contact resistance between the particles is lower, which can further reduce the resistance of the electrode sheet and thus decrease heat generation.

[0162] In the embodiments of the present application, the powder compaction density of the material has a meaning known in the art and can be determined using methods and devices known in the art in accordance with the test standard GB / T24533-2009. As an example, a specific quantity of negative electrode active material is taken as a sample and placed in a mold with a base area of ​​1.327 cm². 2 The powder was inserted into the UTM7305 electronic pressure testing device and subjected to a pressure of 2000 kg (corresponding to 20000 N), held for 30 s, then released and held for 10 s. The powder compaction density of the negative electrode active material under a force of 20000 N was then recorded and calculated.

[0163] In some embodiments, the charging capacity per gram of negative electrode active material in the negative electrode film layer at a rate of 0.1 C is 350 mAh / g to 390 mAh / g. For example, the charging capacity per gram of negative electrode active material at a rate of 0.1 C is 350 mAh / g, 355 mAh / g, 360 mAh / g, 365 mAh / g, 370 mAh / g, 375 mAh / g, 380 mAh / g, 385 mAh / g, 390 mAh / g, or lies within a range consisting of any two of the above values.

[0164] If the charging capacity per gram of the negative electrode active material at a rate of 0.1 C is within the range mentioned above, the energy density of the battery cell is relatively high.

[0165] In the embodiments of the present application, the charging capacity per gram of the negative electrode active material at a rate of 0.1 C has a meaning known in the art and can be determined using devices and methods known in the art, and the detection method is the same as the test method for the charging capacity per gram of the positive electrode active material at a rate of 0.1 C.

[0166] In some embodiments, the negative electrode active material in the second region comprises a carbon-based material. This carbon-based material exhibits high cycle stability, thereby improving the cycle performance of the battery cell. Optionally, the mass fraction of the carbon-based material in the negative electrode active material can be greater than or equal to 80% and less than or equal to 100%.

[0167] The positive electrode active material of the present application consists mainly of a lithium-containing phosphate system with an olivine structure, while the negative electrode active material consists mainly of a carbon-based material system. The two are used in combination, resulting in a relatively excellent cycle life of the battery cell.

[0168] Optionally, the carbon-based material includes graphite particles, with a graphitization degree of 92.0% to 94.5%. For example, the graphitization degree of the graphite particles is 92.0%, 92.5%, 93%, 93.5%, 94%, or 94.5%, or lies within a range consisting of any two of the above values.

[0169] If the graphitization level of the graphite particles is within the range mentioned above, the graphite particles exhibit excellent conductivity, which reduces the heat generation of the negative electrode sheet and the heat generation of the battery cell, and improves the fast charging performance of the battery cell.

[0170] In some embodiments, the graphite particles comprise synthetic graphite and a carbon coating layer, wherein the synthetic graphite comprises secondary particles, the secondary particles comprising several primary particles, and the surface of the synthetic graphite is coated with the carbon coating layer. The carbon in the carbon coating layer consists mainly of amorphous carbon. This is a transitional carbon material with a very low degree of graphitization and crystallinity, close to an amorphous state (or without a fixed shape and periodic structural regularity). In the present application, the amorphous carbon refers to the product obtained after the carbonization of an organic carbon source.

[0171] The artificial graphite comprises secondary particles and offers more migration pathways for lithium ions, while the migration pathways in the primary particles are shorter, which can improve the lithium ion migration rate. The carbon coating layer has more end faces and defects, increasing the number of sites where lithium ions can deintercalate and intercalate. This makes the carbon coating layer more conductive, which can reduce the internal resistance of the negative electrode sheet and thus the amount of heat generated by the battery cell.

[0172] Optionally, the mass fraction of the carbon coating layer is 2% to 5%, based on the mass of the graphite particles. For example, the mass fraction of the carbon coating layer is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or lies within a range consisting of any two of the values ​​mentioned above.

[0173] If the mass fraction of the carbon coating layer is within the range mentioned above, the internal resistance of the negative electrode sheet can be further reduced and the amount of heat generated by the battery cell can be reduced.

[0174] In the embodiments of the present application, the graphite particles can be produced according to a method known in the art. For example, one production method comprises: providing artificial graphite and an organic carbon source, mixing and carbonizing the two, and forming a carbon coating layer on at least a part of the surface of the artificial graphite particles.

[0175] Optionally, the organic carbon source comprises one or more of coal tar pitch, petroleum pitch, phenolic resin, and coconut shell. Optionally, the organic carbon source also includes petroleum pitch. Optionally, the softening point of coal tar pitch and petroleum pitch is below 250 °C.

[0176] Optionally, the carbonization temperature is 700 °C to 1800 °C. Optionally, the carbonization temperature is 1000 °C to 1300 °C. If the carbonation temperature is within a suitable range, the organic carbon source can be carbonized and a coating layer containing amorphous carbon can be formed on at least part of the surface of the artificial graphite.

[0177] Optionally, the carbonation time can last from 1 hour to 6 hours.

[0178] In some embodiments, the carbon-based material may further comprise natural graphite. In particular, the carbon-based material may comprise graphite particles, or the carbon-based material may comprise graphite particles and natural graphite. Optionally, the carbon-based material consists of graphite particles.

[0179] The qualitative and quantitative determination of the individual substances or elements in the present application can be carried out using suitable equipment and methods known to those skilled in the art. The relevant methods of determination may refer to national and international testing standards as well as national and international company standards. Those skilled in the art may also adjust certain test steps / equipment parameters with regard to test accuracy in order to obtain more precise test results. A single method may be used for the qualitative or quantitative determination, or a combination of several methods may be used.

[0180] For example, the present application can combine the general rules for X-ray diffractometry JIS / K0131-1996 to perform an X-ray powder diffraction test and a qualitative analysis of the negative electrode sheet or negative electrode active material.

[0181] Artificial and natural graphites can be distinguished using SEM cross-sectional images obtained with a scanning electron microscope (SEM). The SEM cross-sectional image of natural graphite shows gaps between the scaly structures, while the SEM cross-sectional image of artificial graphite is dense and shows no obvious gaps. They can also be distinguished using their XRD spectra obtained by X-ray diffraction. The XRD spectrum of natural graphite shows a distinct 2H phase and a 3R phase, while the XRD spectrum of artificial graphite shows only the 2H phase.

[0182] In the embodiments of the present application, the negative electrode film layer in the second region comprises at least one film layer, wherein either a single film layer or at least two film layers may be present. Optionally, the negative electrode film layer comprises at least two film layers.

[0183] In the second area, where the negative electrode film layer uses a single-layer film, the negative electrode active material in the negative electrode film layer comprises a carbon-based material. When using a single-layer film, the volume-averaged particle size Dv50 of the negative electrode active material is 8.2 µm to 13.5 µm.

[0184] For example, the volume-averaged particle size Dv50 of the negative electrode active material is 8.2 µm, 8.5 µm, 8.8 µm, 9 µm, 9.2 µm, 9.5 µm, 9.8 µm, 10 µm, 10.2 µm, 10.5 µm, 10.8 µm, 11 µm, 11.2 µm, 11.5 µm, 11.8 µm, 12 µm, 12.2 µm, 12.5 µm, 12.8 µm, 13 µm, 13.2 µm or 13.5 µm, or lies in a range consisting of any two of the above values.

[0185] In the case where the negative electrode film layer comprises at least two film layers, the negative electrode active material in the negative electrode film layer comprises a carbon-based material and optionally a silicon-based material. The silicon-based material may be located in one or at least two of the at least two film layers. The negative electrode film layer may comprise two, three, four, or even more film layers.

[0186] In some embodiments, the second region in the negative electrode film layer comprises a first negative electrode film layer and a second negative electrode film layer, wherein the first negative electrode film layer is arranged on the surface of the negative electrode current collector, the carbon-based material in the first negative electrode film layer comprises graphite particles, the second negative electrode film layer is connected to the side of the first negative electrode film layer facing away from the negative electrode current collector, and the carbon-based material in the second negative electrode film layer comprises graphite particles, wherein the graphite particles in the first negative electrode film layer and the graphite particles in the second negative electrode film layer may be the same or different.

[0187] The interface between the first negative electrode film layer and the second negative electrode film layer is regular or irregular, optionally irregular.

[0188] Optionally, the carbon-based material in the first negative electrode film layer also includes natural graphite.

[0189] The negative electrode film layer comprises at least two film layers. This multilayer coating contributes to improving the fast-charging performance of the battery cell. In particular, if there is a difference between the first and second negative electrode film layers, the pore size difference of the negative electrode film layer can be increased, the tortuosity of lithium-ion transport can be reduced, and the fast-charging performance of the battery cell can be improved.

[0190] Optionally, the volume-averaged particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than or equal to the volume-averaged particle size Dv50 of the negative electrode active material in the second negative electrode film layer. Furthermore, optionally, the volume-averaged particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than the volume-averaged particle size Dv50 of the negative electrode active material in the second negative electrode film layer, which has a beneficial effect on improving the compaction density of the negative electrode film layer. If the negative electrode active material includes graphite particles, the volume-averaged particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume-averaged particle size Dv50 of the graphite particles in the second negative electrode film layer.

[0191] The particle size in the first and second negative electrode film layers differs, which can improve the fast-charging performance of the battery cell. In particular, during fast charging, the overpotential of the second negative electrode film layer is typically higher, and the bottleneck during fast charging lies mainly in this layer. In the embodiments of the present application, the particle size of the second negative electrode film layer is relatively small, which shortens the solid-phase transport path of the lithium ions, improves fast-charging performance, and reduces the problem of lithium plating on the surface of the negative electrode sheet.

[0192] Optionally, the negative electrode active material in the first negative electrode film layer is in granular form and its volume-averaged particle size Dv50 is 9.5 µm to 18.5 µm and optionally 9.5 µm to 14.6 µm. For example, the volume-averaged particle size of the negative electrode active material in the first negative electrode film layer is 9.5 µm, 10 µm, 10.5 µm, 11 µm, 11.5 µm, 12 µm, 12.5 µm, 13 µm, 13.5 µm, 14 µm, 14.5 µm, 14.6 µm, 15 µm, 15.5 µm, 16 µm, 16.5 µm, 17 µm, 17.5 µm, 18 µm, 18.5 µm, or lies in a range consisting of any two of the above values. If the first negative electrode film layer includes graphite particles, the volume-averaged particle size Dv50 of the graphite particles in the first negative electrode film layer is 9.5 µm to 18.5 µm and optionally 9.5 µm to 14.6 µm.

[0193] If the volume-averaged particle size Dv50 of the negative electrode active material in the first negative electrode film layer is within the range mentioned above, the solid-phase transport path of the lithium ions can be shortened and the fast charging performance improved; on the other hand, the material does not agglomerate as easily during the manufacturing process, which can improve the stability of the material.

[0194] Optionally, the negative electrode active material in the second negative electrode film layer is in granular form and its volume-averaged particle size Dv50 is 7.8 µm to 14.3 µm and optionally 7.8 µm to 11.3 µm. For example, the volume-averaged particle size Dv50 of the negative electrode active material is 7.8 µm, 8.0 µm, 8.2 µm, 8.5 µm, 8.8 µm, 9 µm, 9.2 µm, 9.5 µm, 9.8 µm, 10 µm, 10.2 µm, 10.5 µm, 10.8 µm, 11 µm, 11.2 µm, 11.3 µm, 11.5 µm, 11.8 µm, 12 µm, 12.2 µm, 12.5 µm, 12.8 µm, 13 µm, 13.2 µm. 13.5 µm, 13.8 µm, 14 µm, 14.1 µm, 14.3 µm, or lies within a range consisting of any two of the above values. If the second negative electrode film layer comprises graphite particles, the volume-averaged particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8 µm to 14.3 µm, and optionally 7.8 µm to 11.3 µm.

[0195] If the volume-averaged particle size Dv50 of the negative electrode active material in the second negative electrode film layer lies within the aforementioned range, the solid-phase transport path of the lithium ions can be shortened and the fast-charging performance improved; furthermore, the material does not agglomerate as easily during the manufacturing process, which can improve the material's stability; and even moreover, combining the negative electrode active material in the second negative electrode film layer and the negative electrode active material in the first negative electrode film layer within the aforementioned range of volume-averaged particle size is advantageous for creating a gradient pore difference between the second negative electrode film layer and the first negative electrode film layer, reducing the tortuosity of lithium ion transport and improving the fast-charging performance of the battery cell.

[0196] In the embodiments of the present application, the volume-averaged particle size Dv50 of the negative electrode active material has a meaning known in the art and can be determined using devices and methods known in the art, and the detection method is the same as the test method for the volume-averaged particle size Dv50 of the above-mentioned positive electrode active material.

[0197] Optionally, the bulk density of the carbon-based material in the first negative electrode film layer is less than or equal to the bulk density of the carbon-based material in the second negative electrode film layer. The bulk density can reflect the packing density of the active material in the film layer. If the bulk density of the carbon-based material in the second negative electrode film layer is greater than the bulk density of the carbon-based material in the first negative electrode film layer, the second negative electrode film layer is more densely packed, thus increasing the energy density of the battery cell. The first negative electrode film layer is relatively thinly packed and has more pores, which can improve the fast-charging performance of the battery cell.If the negative electrode active material comprises graphite particles, the bulk density of the graphite particles in the first negative electrode film layer is less than or equal to the bulk density of the graphite particles in the second negative electrode film layer.

[0198] Optionally, the bulk density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm³. 3 up to 1.21 g / cm³ 3 , for example 0.82 g / cm³ 3 , 0.85 g / cm³ 3 , 0.88 g / cm³ 3 , 0.90 g / cm³ 3 , 0.92 g / cm³ 3 , 0.95 g / cm³ 3 , 0.98 g / cm³ 3 , 1.00 g / cm² 3 , 1.05 g / cm³ 3 , 1.08 g / cm³ 3 , 1.10 g / cm³ 3 , 1.12 g / cm³ 3 , 1.15 g / cm³ 3 , 1.18 g / cm³ 3 , 1.20 g / cm³ 3 , 1.21 g / cm³ 3or lies within a range consisting of any two of the values ​​mentioned above. If the bulk density of the carbon-based material in the first negative electrode film layer is within a suitable range, the fast-charging performance of the battery cell can be improved.

[0199] Optionally, the bulk density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm³. 3 up to 1.25 g / cm³ 3 , for example 0.90 g / cm² 3 , 0.92 g / cm³ 3 , 0.95 g / cm³ 3 , 0.98 g / cm³ 3 , 1.00 g / cm² 3 , 1.05 g / cm³ 3 , 1.08 g / cm³ 3 , 1.10 g / cm³ 3 , 1.12 g / cm³ 3 , 1.15 g / cm³ 3 , 1.18 g / cm³ 3 , 1.20 g / cm³ 3 , 1.21 g / cm³ 3 , 1.22 g / cm³ 3 , 1.23 g / cm³ 3 , 1.24 g / cm³ 3 , 1.25 g / cm³ 3or lies within a range consisting of any two of the values ​​mentioned above. If the bulk density of the carbon-based material in the second negative electrode film layer is within a suitable range, the energy density of the battery cell can be increased.

[0200] In the embodiments of the present application, the bulk density of a material has a meaning known in the art and can be measured using equipment and methods known in the art. By way of example, it can be measured using a powder bulk density test device, as described in GB / T5162-2006. The test device can be the Bettersize BT-301.

[0201] Optionally, the ratio of the thickness of the second negative electrode film layer to the thickness of the first negative electrode film layer is 3:7 to 7:3 and optionally 4:6 to 6:4. For example, the ratio of the thickness of the second negative electrode film layer to the thickness of the first negative electrode film layer could be 3:7, 4:6, 5:5, 6:4, 7:3, or a range consisting of any two of the above values. By adjusting the ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer, the gradient pore difference between the upper and lower layers can be further increased, the tortuosity of lithium-ion transport reduced, and the fast-charging capability of the battery cell improved.

[0202] In some embodiments, the thickness of the first negative electrode film layer after 10 cycles of the complete charge-discharge test of the battery cell at the beginning of life (BOL) in a disassembly test at 100% state of charge (SOC) is 15 µm to 100 µm, for example 15 µm, 17 µm, 18 µm, 20 µm, 25 µm, 30 µm, 35 µm, 40 µm, 45 µm, 50 µm, 55 µm, 57 µm, 58 µm, 60 µm, 61 µm, 62 µm, 63 µm, 64 µm, 65 µm, 70 µm, 75 µm. 80 µm, 85 µm, 90 µm, 95 µm, 100 µm, or within a range consisting of any two of the above values. If the thickness of the first negative electrode film layer is within the above range, the gradient pore difference between the first and second negative electrode film layers can be increased, the tortuosity of lithium ion transport reduced, and the fast-charging capability of the battery cell improved.

[0203] In some embodiments, the thickness of the second negative electrode film layer after 10 cycles of the complete charge-discharge test of the battery cell at the beginning of life (BOL) is 15 µm to 80 µm, for example 15 µm, 17 µm, 18 µm, 20 µm, 25 µm, 30 µm, 35 µm, 40 µm, 45 µm, 50 µm, 55 µm, 57 µm, 58 µm, 60 µm, 61 µm, 62 µm, 63 µm, 64 µm, 65 µm, 70 µm, 75 µm, 80 µm, or lies in a range consisting of two of the values ​​mentioned above. If the thickness of the second negative electrode film layer is within the range mentioned above, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be increased in a controlled manner, the tortuosity of lithium ion transport can be reduced, and the fast-charging capability of the battery cell can be improved.

[0204] In the embodiments of the present application, for example, an upper charging limit voltage of the battery of 3.65 V and a discharge cut-off voltage of the battery of 2.0 V are explained:

[0205] The BOL test steps are as follows: The battery is charged at 25 °C at a rate of 0.33 C of its nominal capacity to 3.65 V. It is then charged at a constant voltage of 3.65 V to 0.05 C. After a 10-minute rest period, the battery is discharged at a rate of 0.33 C to 2.0 V. The battery is then left to rest again for 10 minutes. This charge-discharge process is defined as one cycle and is repeated 10 times. The battery is then charged at a rate of 0.33 C of its nominal capacity to 3.65 V and subsequently charged at a constant voltage of 3.65 V to 0.05 C. This corresponds to the BOL full charge state. At the BOL full charge state, the negative electrode sheet is removed. The cross-section of the central region of the negative electrode sheet in the thickness direction is examined using a tomographic scanning electron microscope.The first and second negative electrode film layers are distinguished by their interfaces. The thicknesses of both layers are measured. For example, the thicknesses of the first negative electrode film layer are measured at 10 positions, and the average value is calculated as the average thickness of the first negative electrode film layer. Similarly, the thicknesses of the second negative electrode film layer are measured at 10 positions, and the average value is calculated as the average thickness of the second negative electrode film layer.

[0206] In some embodiments, the thickness of the first negative electrode film layer after the complete charge-discharge test of the battery cell at the end of life (EOL) is 15 µm to 110 µm, for example 15 µm, 16 µm, 17 µm, 18 µm, 19 µm, 20 µm, 21 µm, 22 µm, 23 µm, 24 µm, 25 µm, 26 µm, 27 µm, 28 µm, 29 µm, 30 µm, 35 µm, 40 µm, 43 µm, 45 µm, 50 µm, 55 µm, 60 µm, 65 µm µm, 66 µm, 67 µm, 68 µm, 69 µm, 70 µm, 75 µm, 80 µm, 85 µm, 90 µm, 95 µm, 100 µm, 105 µm, 110 µm, or lies within a range consisting of any two of the above values. If the thickness of the first negative electrode film layer is within the above range, the gradient pore difference between the upper and lower layers of the first and second negative electrode film layers can be controlled and increased, reducing the tortuosity of lithium ion transport and improving the fast-charging capability of the battery cell.

[0207] In some embodiments, the thickness of the second negative electrode film layer after the complete charge-discharge test of the battery cell at the end of life (EOL) is 15 µm to 90 µm, for example 15 µm, 16 µm, 17 µm, 18 µm, 19 µm, 20 µm, 21 µm, 22 µm, 23 µm, 24 µm, 25 µm, 26 µm, 27 µm, 28 µm, 29 µm, 30 µm, 35 µm, 40 µm, 43 µm, 45 µm, 50 µm, 55 µm, 60 µm, 65 µm. 66 µm, 67 µm, 68 µm, 69 µm, 70 µm, 75 µm, 80 µm, 85 µm, 90 µm, or lies within a range consisting of any two of the above values. If the thickness of the second negative electrode film layer is within the above range, the gradient pore difference between the upper and lower layers of the first and second negative electrode film layers can be controlled and increased, reducing the tortuosity of lithium ion transport and improving the fast-charging capability of the battery cell.

[0208] In the embodiments of the present application, for example, an upper charging limit voltage of the battery of 3.65 V and a discharge cut-off voltage of the battery of 2.0 V are explained:

[0209] The steps of the complete end-of-life charge-discharge test are as follows: The battery is charged at 60°C at a rate of 0.33C to 3.65V of its nominal capacity. It is then charged at a constant voltage of 3.65V to 0.05C. After a 10-minute rest period, the battery is discharged at a rate of 0.33C to 2.0V. The battery is then left to rest again for 10 minutes. This charge-discharge process is defined as one cycle and is repeated until the battery capacity has dropped to 80% of its nominal capacity. The battery is then charged at 25°C at a constant current of 0.33C to 3.65V. At a constant voltage, it is charged at a rate of 0.05C to 3.65V. This corresponds to the end-of-life (EOL) full charge state. At the EOL full charge state, the negative electrode sheet is removed.The cross-section of the central region of the negative electrode film in the thickness direction is examined using a tomographic scanning electron microscope. The first and second negative electrode film layers are distinguished based on their interfaces. The thicknesses of both layers are measured. For example, the thicknesses of the first negative electrode film layer are measured at 10 positions, and the average value is calculated as the average thickness of the first negative electrode film layer. Similarly, the thicknesses of the second negative electrode film layer are measured at 10 positions, and the average value is calculated as the average thickness of the second negative electrode film layer.

[0210] In some embodiments, if the second region in the negative electrode film layer uses a single-layer film (unlike the double-layer film layer mentioned above), the negative electrode film layer also comprises a lithium-containing binder. Optionally, the mass fraction of the lithium-containing binder, based on the mass of the negative electrode film layer, is 0.1% to 3%. By way of example, the mass fraction of the lithium-containing binder, based on the mass of the negative electrode film layer, is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 2.5%, 3%, or lies in a range consisting of any two of the values ​​mentioned above.The lithium element in the lithium-containing binder can be present in ionic form, thereby increasing the number of lithium ions that can move freely within the negative electrode film layer, shortening the distance over which the lithium ions diffuse to the surface of the negative electrode film layer, increasing the rate of deintercalation and intercalation of lithium ions, and improving the fast-charging performance of the battery cell. Optionally, the negative electrode film layer can also include a negative electrode binder. For example, the negative electrode binder may include at least one of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0211] Optionally, the mass fraction of lithium in the lithium-containing binder is 3% to 10%. For example, the mass fraction of lithium in the lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or lies within any two of the values ​​mentioned above. The mass fraction of lithium is calculated relative to the mass of the lithium-containing binder. If the mass fraction of lithium is within the range mentioned above, the number of lithium ions freely moving within the negative electrode film layer can be relatively large. This further reduces the distance over which the lithium ions diffuse to the surface of the negative electrode film layer, increases the deintercalation and intercalation rate of the lithium ions, and improves the fast-charging performance of the battery cell.

[0212] For example, the lithium-containing binder comprises a copolymer of lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate, wherein the copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer, with the molar percentage of each of these monomers being 30% to 50%, 15% to 45%, 5% to 20%, and 20% to 35%. For instance, the molar percentage of each of these monomers is 35%, 30%, 15%, and 20%, or 40%, 20%, 10%, and 30%, or 45%, 15%, 20%, and so on.

[0213] The lithium-containing binder in the above material can provide a specific amount of lithium ions to the negative electrode film layer, thus improving the fast-charging performance of the battery cell. It does not swell as easily during charging and discharging and exhibits a stable structure, thereby improving the cycle life of the negative electrode film layer during fast charging and discharging.

[0214] In other embodiments, if the second region in the negative electrode film layer comprises at least two film layers, the second region in the negative electrode film layer also comprises a lithium-containing binder.

[0215] Optionally, the first negative electrode film layer also includes a first lithium-containing binder, and the second negative electrode film layer also includes a second lithium-containing binder, with the mass fraction of the first lithium-containing binder relative to the mass of the first negative electrode film layer being less than or equal to the mass fraction of the second lithium-containing binder relative to the mass of the second negative electrode film layer. Furthermore, optionally, the mass fraction of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than the mass fraction of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0216] The mass fraction of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the second lithium-containing binder provides the second negative electrode film layer with a relatively larger number of freely moving lithium ions, which can further improve the fast charging performance of the battery cell.

[0217] Optionally, the mass fraction of the first lithium-containing binder, relative to the mass of the first negative electrode film layer, is 0.1% to 3%. For example, the mass fraction of the first lithium-containing binder, relative to the mass of the first negative electrode film layer, is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, or lies within a range consisting of any two of the above values. The lithium element in the first lithium-containing binder can be present in ionic form, thereby increasing the number of lithium ions that can move freely within the negative electrode film layer, reducing the distance over which the lithium ions diffuse to the surface of the negative electrode film layer, increasing the rate of deintercalation and intercalation of lithium ions, and improving the fast-charging performance of the battery cell.

[0218] Optionally, the mass fraction of lithium in the first lithium-containing binder is 3% to 10%, and optionally 3% to 8%. For example, the mass fraction of lithium in the first lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or lies within any two of the values ​​mentioned above. If the mass fraction of lithium is within the range mentioned above, the number of lithium ions freely moving within the negative electrode film layer can be relatively large. This further reduces the distance over which the lithium ions diffuse to the surface of the negative electrode film layer, increases the deintercalation and intercalation rate of the lithium ions, and improves the fast-charging performance of the battery cell.

[0219] For example, the first lithium-containing binder comprises a copolymer of lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate, wherein the copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer, the molar percentage of each of these monomers being 30% to 50%, 15% to 45%, 5% to 20%, and 20% to 35%, respectively. For instance, the molar percentage of each monomer is 35%, 30%, 15%, and 20%, or 40%, 20%, 10%, and 30%, or 45%, 15%, and 20%, etc.

[0220] The lithium-containing binder in the above material can provide a specific amount of lithium ions to the negative electrode film layer, thus improving the fast-charging performance of the battery cell. It does not swell as easily during charging and discharging and exhibits a stable structure, thereby improving the cycle life of the negative electrode film layer during fast charging and discharging.

[0221] Optionally, the mass fraction of the second lithium-containing binder, relative to the mass of the second negative electrode film layer, is 0.1% to 3%. For example, the mass fraction of the second lithium-containing binder, relative to the mass of the second negative electrode film layer, is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, or lies within a range consisting of any two of the above values. The lithium element in the second lithium-containing binder can be present in ionic form, thereby increasing the number of lithium ions that can move freely within the negative electrode film layer, reducing the distance over which the lithium ions diffuse to the surface of the negative electrode film layer, increasing the rate of deintercalation and intercalation of lithium ions, and improving the fast-charging performance of the battery cell.

[0222] The first lithium-containing binder and the second lithium-containing binder can be made of the same material or of different materials.

[0223] Optionally, the mass fraction of lithium in the second lithium-containing binder is 3% to 10%, and optionally 3% to 8%. For example, the mass fraction of lithium in the second lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or lies within any two of the values ​​mentioned above. If the mass fraction of lithium is within the range mentioned above, the number of lithium ions freely moving in the negative electrode film layer can be relatively large, further reducing the distance over which the lithium ions diffuse to the surface of the negative electrode film layer, increasing the deintercalation and intercalation rate of the lithium ions, and improving the fast-charging performance of the battery cell.

[0224] For example, the second lithium-containing binder comprises a copolymer of lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate, wherein the copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer, the molar percentage of each of these monomers being 30% to 50%, 15% to 45%, 5% to 20%, and 20% to 35%, respectively. For instance, the molar percentage of each monomer is 35%, 30%, 15%, and 20%, or 40%, 20%, 10%, and 30%, or 45%, 15%, and 20%, etc.

[0225] The lithium-containing binder in the above material can provide a specific amount of lithium ions to the negative electrode film layer, thus improving the fast-charging performance of the battery cell. It does not swell as easily during charging and discharging and exhibits a stable structure, thereby improving the cycle life of the negative electrode film layer during fast charging and discharging.

[0226] In some embodiments, the first negative electrode film layer also comprises a negative electrode binder, and the second negative electrode film layer also comprises a negative electrode binder. The negative electrode binder in the first negative electrode film layer and the negative electrode binder in the second negative electrode film layer each independently comprise at least one of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0227] In some embodiments, the total content of the first lithium-containing binder and the negative electrode binder in the first negative electrode film layer is greater than the total content of the second lithium-containing binder and the negative electrode binder in the second negative electrode film layer, and the mass fraction of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than the mass fraction of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0228] In some embodiments, the negative electrode film layer optionally comprises a conductive element of the negative electrode. The embodiments of the present application do not specifically restrict the type of conductive element of the negative electrode. By way of example, the conductive element of the negative electrode may comprise at least one of superconducting carbon, conductive graphite, carbon black, carbon black, Ketjen carbon black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass fraction of the conductive element of the negative electrode is ≤ 5%, based on the total weight of the negative electrode film layer.

[0229] In some embodiments, the negative electrode film layer optionally also includes a negative electrode binder. In some embodiments, the mass fraction of the negative electrode binder is ≤ 5%, based on the total weight of the negative electrode film layer.

[0230] In some embodiments, the negative electrode film layer optionally comprises further excipients. For example, these excipients may include a thickening agent, a dispersing agent, and the like, such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor material, and the like. In some embodiments, the mass fraction of the excipients, based on the total weight of the negative electrode film layer, is ≤ 2%.

[0231] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, the metal foil can include at least one foil made of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy. The composite current collector can comprise a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. For example, the metal material in the metal material layer can include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy. For example, the polymer material base layer can include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE).

[0232] In some embodiments, the thickness of the negative electrode current collector is 4 µm to 6 µm. For example, the thickness of the negative electrode current collector is 4 µm, 4.5 µm, 5 µm, 5.5 µm, 6 µm, or lies in a range consisting of any two of the above values.

[0233] If the thickness of the negative electrode current collector is within the range mentioned above, the negative electrode current collector exhibits relatively excellent current conductivity and allows for a higher energy density of the battery cell.

[0234] In the embodiments of the present application, the thickness of the negative electrode current collector has a meaning known in the art and can be determined using devices and methods known in the art. For example, the film layer is washed off the surface of the negative electrode current collector using a solvent, and the thickness of the negative electrode current collector is measured with a high-precision micrometer.

[0235] The negative electrode film layer is typically formed by applying a negative electrode paste to the negative electrode current collector, followed by drying and cold pressing. The negative electrode paste is typically formed by dispersing and uniformly stirring the negative electrode active, an optional conductive agent, an optional binder, and other optional excipients in a solvent. The solvent may be, but is not limited to, N-methyl-2-pyrrolidone (NMP) or deionized water.

[0236] The negative electrode sheet does not exclude further additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet according to the embodiments of the present application also comprises a conductive layer of the negative electrode, which is enclosed between the negative electrode current collector and the negative electrode film layer and is arranged on the surface of the negative electrode current collector. In some other embodiments, the negative electrode sheet according to the embodiments of the present application also comprises a protective layer that covers the surface of the negative electrode film layer.

[0237] In some embodiments, the negative electrode sheet also includes a conductive layer of the negative electrode, wherein the conductive layer of the negative electrode is located between the negative electrode film layer and the negative electrode current collector. The conductive layer of the negative electrode can further improve the conductivity of the negative electrode sheet and reduce the heat generation of the negative electrode sheet, thereby reducing the amount of heat generated by the battery cell.

[0238] In some embodiments, the thickness of the conductive layer of the negative electrode is 0.1 µm to 2 µm. For example, the thickness of the conductive layer of the negative electrode can be 0.1 µm, 0.5 µm, 0.8 µm, 1 µm, 1.2 µm, 1.5 µm, 1.6 µm, 1.8 µm, 2 µm, or a range consisting of any two of the above values.

[0239] If the thickness of the conductive layer of the negative electrode is within the range mentioned above, the conductivity of the negative electrode sheet can be further improved and the heat generation of the negative electrode sheet reduced, thereby reducing the heat generation of the battery cell and simultaneously increasing the energy density of the battery cell.

[0240] In the embodiments of the present application, the thickness of the conductive layer of the negative electrode has a meaning known in the art and can be determined using devices and methods known in the art, and the above-mentioned test method for the conductive layer of the negative electrode can be used.

[0241] In some embodiments, the conductive layer of the negative electrode comprises one or more negative electrode conductive elements and negative electrode binders. The conductive element in the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode sheet and reducing the amount of heat generated by the battery cell. The negative electrode binder in the conductive layer of the negative electrode can improve the bonding performance between the negative electrode current collector and the negative electrode film layer, thereby increasing the structural stability of the negative electrode sheet.

[0242] In some embodiments, the conductive layer of the negative electrode optionally comprises further excipients. Examples of such excipients include thickening agents such as sodium carboxymethylcellulose (CMC), calcium hydroxide, etc.

[0243] Optionally, the mass fraction of the conductive material of the negative electrode in the conductive layer of the negative electrode is 20% to 40%. For example, the mass fraction of the conductive material of the negative electrode is 20%, 25%, 30%, 35%, 40%, or lies within a range consisting of any two of the values ​​mentioned above.

[0244] For example, the conductive material of the negative electrode comprises one or more of superconducting carbon, conductive graphite, acetylene carbon black, carbon black, Ketjen carbon black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0245] Optionally, the mass fraction of the binder in the conductive layer of the negative electrode is 60% to 80%. For example, it is 60%, 65%, 70%, 75%, 80%, or lies within a range consisting of any two of the values ​​mentioned above.

[0246] For example, the binder of the negative electrode comprises one or more of styrene-butadiene rubber SBR, water-soluble unsaturated resin SR-1B, aqueous acrylic resin, polyvinyl alcohol, sodium alginate and carboxymethyl chitosan.

[0247] In some embodiments, the ratio CB of the capacity per unit area of ​​the negative electrode film layer to the capacity per unit area of ​​the positive electrode film layer in the battery cell is 1.05 to 1.30 and optionally 1.07 to 1.15. For example, the ratio CB of the capacity per unit area of ​​the negative electrode film layer to the capacity per unit area of ​​the positive electrode film layer in the battery cell is 1.05, 1.07, 1.1, 1.12, 1.15, 1.18, 1.2, 1.22, 1.25, 1.28, 1.3, or lies in a range consisting of any two of the values ​​mentioned above.

[0248] If the ratio CB of the capacity per unit area of ​​the negative electrode film layer to the capacity per unit area of ​​the positive electrode film layer in the battery cell is within the range mentioned above, there are sufficient sites in the negative electrode film layer for lithium intercalation, which can reduce the risk of lithium plating and promote fast charging.

[0249] In the embodiments of the present application, the CB value has a meaning known in the art and can be determined using devices and methods known in the art. For example, the capacitance of the negative electrode film layer per unit area and the capacitance of the positive electrode film layer per unit area are calculated separately, and the ratio of the two values ​​is calculated to obtain the CB value.

[0250] In particular, it is explained with an upper charging limit voltage of the battery of 3.65 V and a discharge cut-off voltage of the battery of 2.0 V:

[0251] The capacitance of the positive electrode film layer per unit area refers to the actual available delithiation capacitance of the positive electrode active material. The test method is as follows: The battery is disassembled in a Braun glove box PRS340 / 11-119-11, the positive electrode sheet is removed, and reassembled into a CR2430 half-button cell with one positive electrode and one lithium sheet. Assuming that the area of ​​the positive electrode sheet used is a mm² 2The electrolyte solution used is a 1 mol / L LiPF6 solution with an EC / EMC / DEC ratio of 3 / 5 / 2. The assembled half-button cell is left to stand for 3 hours. The tests are performed at 25 °C, starting with a charge at 0.1 C in the voltage range of 2.0 V to 3.65 V to deintercalate the lithium, followed by a discharge at 0.05 C to 2.0 V to intercalate the lithium. After two cycles, the discharge capacity of the half-button cell is recorded as Y mAh in the second cycle. Assuming that the positive electrode sheet in the actual battery design has a length of b mm and a width of c mm, and that d areas of the positive electrode current collector are coated with the positive electrode active material, then the capacity of the positive electrode film layer per unit area is = Y / a * b * c * d.

[0252] Specifically, the capacitance of the negative electrode film layer per unit area refers to the actual available lithiation capacity of the negative electrode active material. The test method is as follows: The battery is disassembled in a Braun glove box PRS340 / 11-119-11, the negative electrode sheet is removed, and it is reassembled into a CR2430 half-button cell with one negative electrode and one lithium sheet. Assuming that the area of ​​the negative electrode sheet used is f mm² 2The electrolyte solution used is a 1 mol / L LiPF6 solution with an EC / EMC / DEC ratio of 3 / 5 / 2. The assembled half-button cell is left to stand for 3 hours. Tests are performed at 25 °C, with the cell first being discharged at 0.1 C in the voltage range of 2 V to 0 V to intercalate lithium, and then charged at 0.05 C to 2 V to deintercalate lithium. After two cycles, the discharge capacity of the half-button cell is recorded as Z mAh in the second cycle. Assuming that the negative electrode sheet in the actual battery design has a length of h mm and a width of i mm, and that d surfaces of the negative electrode current collector are coated with the negative electrode active material, then the available lithiation capacity of the negative electrode is = Z / f * h * i * d. [Positive electrode sheet]

[0253] The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer, which is arranged on at least one surface of the positive electrode current collector and comprises a positive electrode active material. For example, the positive electrode current collector has two surfaces that are opposite each other in its thickness direction, and the positive electrode film layer is arranged on one or both of the two opposite surfaces of the positive electrode current collector.

[0254] In some embodiments, the compaction density of the positive electrode film layer when the battery cell is at a state of charge (SOC) of 100% is 2.50 g / cm³. 3 up to 2.80 g / cm³ 3 , optional 2.55 g / cm² 3 up to 2.70 g / cm³ 3When the battery cell is at a state of charge (SOC) of 100%, the density of the positive electrode film layer is, for example, 2.50 g / cm³. 3 , 2.52 g / cm³ 3 , 2.55 g / cm³ 3 , 2.56 g / cm³ 3 , 2.57 g / cm³ 3 , 2.58 g / cm³ 3 , 2.60 g / cm³ 3 , 2.62 g / cm³ 3 , 2.65 g / cm³ 3 , 2.68 g / cm³ 3 , 2.70 g / cm³ 3 , 2.72 g / cm³ 3 , 2.75 g / cm³ 3 , 2.78 g / cm³ 3 , 2.80 g / cm³ 3 or lies within a range consisting of any two of the values ​​mentioned above.

[0255] If the density of the positive electrode film layer lies within the aforementioned range, this is advantageous for increasing the energy density of the battery cell. Furthermore, because the active material in the positive electrode film layer is relatively densely packed, and the contact resistance between the particles is low, the resistance of the electrode sheet can be further reduced, thereby decreasing heat generation during fast charging. By adjusting the density of the positive electrode film layer to a suitable range, the battery cell therefore exhibits both high energy density and high charging rate performance.

[0256] In some embodiments, the one-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm². 2 up to 370 mg / 1540.25 mm 2 , optional 240 mg / 1540.25 mm 2 up to 330 mg / 1540.25 mm 2For example, the coating weight of the positive electrode film layer on one side is 200 mg / 1540.25 mm². 2 , 210 mg / 1540.25 mm 2 , 220 mg / 1540.25 mm 2 , 230 mg / 1540.25 mm 2 , 240 mg / 1540.25 mm 2 , 250 mg / 1540.25 mm 2 , 260 mg / 1540.25 mm 2 , 270 mg / 1540.25 mm 2 , 280 mg / 1540.25 mm 2 , 290 mg / 1540.25 mm 2 , 300 mg / 1540.25 mm 2 , 310 mg / 1540.25 mm 2 , 320 mg / 1540.25 mm 2 , 330 mg / 1540.25 mm 2 , 340 mg / 1540.25 mm 2 , 350 mg / 1540.25 mm 2 , 360 mg / 1540.25 mm 2 , 370 mg / 1540.25 mm 2 or lies within a range consisting of any two of the values ​​mentioned above.

[0257] If the one-sided coating weight of the positive electrode film layer is within the range mentioned above, the amount of heat generated per unit area of ​​the positive electrode sheet is not too large, so that the energy density and the charging rate performance of the battery cell can be increased simultaneously.

[0258] In the embodiments of the present application, the density of the positive electrode film layer of the battery cell at a state of charge (SOC) of 100% can be determined as follows: The positive electrode sheet is removed from the battery cell at a state of charge (SOC) of 100%, and the density of the positive electrode film layer is measured. For example, the single-sided coated positive electrode sheet (in the case of a double-sided coated electrode sheet, the positive electrode film layer on one side can be wiped off first) is taken, then punched into small discs with an area of ​​S1 and weighed, and its weight is recorded as M1. Subsequently, its thickness H1 is measured. Then, the positive electrode film layer of the above-weighed positive electrode sheet is wiped off, the positive electrode current collector is weighed, its weight is recorded as M0, and its thickness H0 is measured.The one-sided coating weight of the positive electrode film layer = (the weight of the positive electrode sheet M1 - the weight of the positive electrode current collector M0) / S1, the thickness of the positive electrode film layer = the thickness of the positive electrode sheet H1 - the thickness of the positive electrode current collector H0, the compaction density of the positive electrode film layer = the one-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0259] In some embodiments, the powder resistance of the positive electrode active material is 1 Ω·cm to 27.5 Ω·cm, optionally less than or equal to 20 Ω·cm, and optionally less than or equal to 11 Ω·cm. For example, the powder resistance of the positive electrode active material can be 27.5 Ω·cm, 20 Ω·cm, 19 Ω·cm, 18 Ω·cm, 17 Ω·cm, 16 Ω·cm, 15 Ω·cm, 14 Ω·cm, 13 Ω·cm, 12 Ω·cm, 11 Ω·cm, 10 Ω·cm, 9 Ω·cm, 8 Ω·cm, 7 Ω·cm, 6 Ω·cm, 5 Ω·cm, 4 Ω·cm, 3 Ω·cm, 2 Ω·cm, 1 Ω·cm or lie in a range consisting of any two of the above values.

[0260] The powder resistance of the positive electrode active material is relatively low, so the resistance of the positive electrode sheet is relatively low, resulting in less heat generation from the battery cell.

[0261] In the embodiments of the present application, the powder resistance of the material has a meaning known in the art and can be determined using methods and devices known in the art, for example in accordance with the test standard GB / T30835-2014 with a powder resistance measuring device PRCD1100.

[0262] In some embodiments, the powder compaction density of the positive electrode active material at 30000 N is 2.46 g / cm³. 3 up to 2.8 g / cm³ 3 For example, the powder compaction density of the positive electrode active material at 30000 N is 2.46 g / cm³. 3 , 2.47 g / cm³ 3 , 2.48 g / cm³ 3 , 2.49 g / cm³ 3 , 2.5 g / cm³ 3 , 2.51 g / cm³ 3 , 2.55 g / cm³ 3 , 2.58 g / cm³ 3 , 2.60 g / cm³ 3 , 2.65 g / cm³ 3 , 2.68 g / cm³ 3 , 2.70 g / cm³ 3 , 2.72 g / cm³ 3 , 2.75 g / cm³ 3 , 2.78 g / cm³ 3 , 2.80 g / cm³ 3or lies within a range consisting of any two of the values ​​mentioned above.

[0263] If the powder compaction density of the positive electrode active material is within the range mentioned above at 30000 N, the energy density of the battery cell can be increased, and because the positive electrode active material can be stacked more densely in the positive electrode film layer, the contact resistance between the particles is lower, which can further reduce the resistance of the electrode sheet and thus decrease heat generation.

[0264] In the embodiments of the present application, the powder compaction density of the material has a meaning known in the art and can be determined using methods and devices known in the art, as in accordance with test standard GB / T24533-2009. For example, a certain quantity of positive electrode active material is taken as a sample and placed in a mold with a base area of ​​1.327 cm². 2 The powder was inserted into the UTM7305 electronic pressure testing device and subjected to a pressure of 3000 kg (corresponding to 30000 N), held for 30 s, then released and held for 10 s. The powder compaction density of the positive electrode active material under a force of 30000 N was then recorded and calculated.

[0265] In some embodiments, the charging capacity per gram of positive electrode active material at a rate of 0.1 C is 150 mAh / g to 170 mAh / g, and optionally 157 mAh / g to 170 mAh / g. For example, the charging capacity per gram of the positive electrode active material at a rate of 0.1 C is 150 mAh / g, 151 mAh / g, 152 mAh / g, 153 mAh / g, 154 mAh / g, 155 mAh / g, 156 mAh / g, 157 mAh / g, 158 mAh / g, 159 mAh / g, 160 mAh / g, 161 mAh / g, 162 mAh / g, 163 mAh / g, 164 mAh / g, 165 mAh / g, 166 mAh / g, 167 mAh / g, 168 mAh / g, 169 mAh / g, 170 mAh / g or lies within a range consisting of any two of the above values.

[0266] If the charging capacity per gram of the positive electrode active material at a rate of 0.1 C is within the range mentioned above, the energy density of the battery cell is relatively high.

[0267] In the embodiments of the present application, the capacity of the active material per gram has the meaning known in the art and can be determined using devices and methods known in the art, wherein the test method for the first coulomb efficiency and the first specific discharge capacity in Annex G of the national standard GB / T 24533-2019 can be used, wherein metallic lithium is used as the negative electrode and a sample electrode sheet containing the above material is used as the positive electrode, and the two are assembled to form a half-button cell.At 23 °C ± 2 °C, the half-button cell is charged and discharged at a rate of 0.1 C on a battery tester or other test device with equivalent performance to obtain the capacity of the half-button cell, and then the parameter of the charging capacity per gram is obtained by dividing this capacity by the mass of the active material of the electrode sheet.

[0268] In some embodiments, the mass fraction of the lithium-containing phosphate with an olivine structure in the positive electrode active material can be greater than or equal to 80% and less than or equal to 100%. The positive electrode active material in the present application can be considered a lithium-containing phosphate system with an olivine structure. If the mass fraction of the lithium-containing phosphate with an olivine structure is less than 100%, the positive electrode active material can also comprise, but is not limited to, a commonly used positive electrode active material, for example, at least one of the lithium-containing transition metal oxides.Examples of lithium-containing transition metal oxides may include, but are not limited to, at least one of the following: lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0269] Optionally, the mass fraction of the lithium-containing phosphate with olivine structure in the positive electrode active material is 100%.

[0270] In the embodiments of the present application, the lithium-containing phosphate with an olivine structure can consist of phosphate particles or of a material obtained by coating and modifying the phosphate particles. For example, the lithium-containing phosphate with an olivine structure comprises phosphate particles and a coating layer, wherein the surface of the phosphate particles is coated with the coating layer and contains one or more of C, Fe, Ti, Zr, Hf, Ge, and Sn.

[0271] By coating the surface of phosphate particles with the coating layer, the conductivity of the lithium-containing phosphate with olivine structure can be improved, the powder resistance of the material reduced, and the migration rate of the lithium ions increased, thereby improving the fast charging capability of the battery and reducing the amount of heat generated by the battery cell.

[0272] In some embodiments, the phosphate particles comprise a compound with the general formula of Li x1 A y1 Me a M b P 1-c X c Y z , where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3 and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5 and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A comprises one or more of Na, K and Mg, Me comprises one or more of Mn, Fe, Co and Ni, M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La and Ce, X comprises one or more of S, Si, Cl, B, C, and N, and Y comprises one or more of O and F. The phosphate particles exhibit excellent cycle stability, which has a positive effect on improving the cycle performance of the battery cell.

[0273] Examples of phosphate particles include one or more LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. During the charging and discharging process of a battery cell, deintercalation and intercalation, as well as the consumption of active ions such as lithium, occur, and the molar content of lithium varies depending on the state of discharge of the battery cell. When listing positive electrode active materials such as LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc., the molar content of lithium refers to the initial state of the material, i.e., the state before it is added. The positive electrode active material is used in the battery system. After the charge-discharge cycle, the molar content of lithium may change. When listing positive electrode active materials such as LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc., in the embodiments of the present application, the molar content of oxygen (O) is only a theoretical value.The release of oxygen from the lattice leads to a change in the molar content of oxygen (O), which is why the molar content of oxygen (O) varies in practice. The situations mentioned above all fall within the scope of protection of this application.

[0274] In some embodiments, the coating layer comprises a fast ion conductor with the general formula of Li 3-d Fe 2-d M26(PO x2 ) y2 , where M2 comprises one or more of Ti, Zr, Hf, Ge and Sn, and 0≤d≤1.0 <x2<5,0<y2<4.

[0275] An example of a fast ion conductor is a material with a NASICON structure and includes, for example, one or more of lithium iron titanium phosphate Li2FeTi(PO4)3, lithium iron zirconium phosphate Li2FeZr(PO4)3 and lithium iron tin phosphate Li2FeSn(PO4)3.

[0276] The fast ion conductor with NASICON structure is a material with superior ionic conductivity and features numerous three-dimensional diffusion and transport channels for lithium ions. It is characterized by high ionic conduction efficiency and structural stability during multiple deintercalations and intercalations of lithium ions. Surface coating of phosphate particles with a fast ion conductor with NASICON structure significantly increases the lithium ion transport rate during multiple deintercalations and intercalations at the positive electrode, improves the ionic conductivity of the positive electrode active material, and enhances the fast-charging capability of the battery cell. Furthermore, this can increase the capacity per gram and the energy density of the corresponding battery cell.

[0277] In some embodiments, the coating layer also comprises elemental carbon.

[0278] The elemental carbon and the fast ionic conductor can be arranged in layers. For example, the elemental carbon can be used as a separate carbon coating layer, and the fast ionic conductor as a separate fast ionic conductor layer. The surface of the phosphate particles can be coated with the carbon coating layer, and the fast ionic conductor layer is located on the surface of the carbon coating layer, i.e., on the side of the carbon coating layer facing away from the phosphate particles. Alternatively, the surface of the phosphate particles can be coated with the fast ionic conductor layer, and the carbon coating layer is located on the surface of the fast ionic conductor layer, i.e., on the side of the fast ionic conductor layer facing away from the phosphate particles.Of course, the elemental carbon and the fast ion conductor can also be arranged in the same layer.

[0279] Optionally, the surface of the fast ion conductor layer can be coated with a carbon coating layer formed by carbonizing an organic carbon source (e.g., glucose, polyethylene glycol, etc.). The carbon coating layer can partially or completely cover the surface of the ion conductor layer. By applying the carbon coating layer, the electronic conductivity of the phosphate particles can be significantly improved, compensating for their poor electronic conductivity and increasing the energy density of the battery cell.

[0280] In particular, the arrangement of the carbon coating layer enables the positive electrode active material of the present application to have the following advantages:

[0281] The carbon coating layer in the positive electrode active material of the present application provides a suitable channel for electron transport, thereby significantly increasing the electron conductivity during multiple deintercalations and intercalations of lithium, improving the electronic conductivity of the lithium-containing phosphate, improving the charging capability of the corresponding battery cell, and also increasing the energy density.

[0282] The carbon coating layer of the positive electrode active material of the present application is loose and porous, allowing the electrolyte solution to come into complete and effective contact with the lithium-containing phosphate, thus increasing the transport rate of lithium ions at the phase interface and improving the charging capability of the battery cell.

[0283] Coating the surface of the lithium-containing phosphate with a carbon coating layer can not only improve the conductivity of the lithium-containing phosphate, but also improve the structural stability of the positive electrode active material, thereby effectively reducing the iron dissolution of the positive electrode active material during long-term storage and cyclic use of the battery cell, and thus improving the cycle life of the battery cell.

[0284] The positive electrode active material of the present application uses lithium-containing phosphate as a substrate and fully exploits its advantages such as cost-effective production, high operational reliability, and excellent cycle stability, while coating layers (a fast ionic conduction layer and a carbon coating layer) are used to overcome the disadvantages of poor electronic and ionic conductivity. The battery cell produced from the positive electrode active material of the present application can exhibit improved energy density with excellent cycle performance.

[0285] In the embodiments of the present application, the element content in the positive electrode active material has a meaning known in the art and can be determined using devices and methods known in the art. For example, it is measured by inductively coupled plasma atomic emission spectroscopy (ICP-OES, instrument model: Thermo ICAP7400) with reference to EPA 6010D-2014. After the battery cell is discharged to a state of charge (SOC) of 0%, the positive electrode sheet is removed, cleaned with DMC, and dried. It is then calcined at high temperature to remove impurities. Next, 0.4 g of positive electrode active material is weighed out and mixed with 10 mL (50% concentration) of aqua regia. It is then placed on a plate at 180 °C for 30 minutes.After digestion on the plate, the volume is made up to 100 mL and the quantitative test is carried out using the standard curve method.

[0286] In some embodiments, the degree of graphitization of the positive electrode active material is 0.15 to 0.32 and optionally 0.19 to 0.26. For example, the degree of graphitization of the positive electrode active material is 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, or lies in a range consisting of any two of the above values.

[0287] If the graphitization level of the positive electrode active material is within the range mentioned above, this is advantageous in order to improve the conductivity of the positive electrode active material, reduce the heat generation of the positive electrode sheet and thus the amount of heat generated by the battery cell.

[0288] In the embodiments of the present application, the higher the degree of graphitization of the material, the lower the degree of disorder. This can be verified according to the test standard JIS / K 0131-1996 (General Rules for X-ray Diffractometry).

[0289] In some embodiments, the mass fraction of the element carbon in the lithium-containing phosphate with olivine structure is 1% to 2%, and the specific surface area of ​​the lithium-containing phosphate with olivine structure is 5 m². 2 / g up to 18 m 2 / G.

[0290] Optionally, the mass fraction of the element carbon in the lithium-containing phosphate with olivine structure is 1% to 2%, and the specific surface area of ​​the lithium-containing phosphate with olivine structure is 7.5 m². 2 / g up to 14 m 2 / g .

[0291] For example, the mass fraction of the element carbon in the lithium-containing phosphate with olivine structure is 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or lies in a range consisting of any two of the above values.

[0292] For example, the specific surface area of ​​lithium-containing phosphate with an olivine structure is 5 m². 2 / g, 6 m 2 / g, 7 m 2 / g, 8 m 2 / g, 9 m 2 / g, 10 m 2 / g, 11 m 2 / g, 12 m 2 / g, 13 m 2 / g, 14 m 2 / g, 15 m 2 / g, 16 m 2 / g, 17 m 2 / g, 18 m 2 / g or lies within a range consisting of any two of the above values.

[0293] The element carbon is primarily present in the coating layer as a carbon coating layer. This carbon coating layer is loose and porous, which increases the specific surface area of ​​the material, improves the effective contact between the electrolyte solution and the phosphate particles, and promotes the transport of lithium ions at the interface. If the mass fraction of the element carbon is within the aforementioned range, the conductivity of the lithium-containing phosphate with an olivine structure can be significantly improved. This, in turn, enhances the ionic and electronic conductivity of the lithium-containing phosphate with an olivine structure, thereby increasing the fast-charging capability and energy density of the battery cell.

[0294] In the embodiments of the present application, the specific surface area of ​​the material has a meaning known in the art and can be determined using devices and methods known in the art, for example according to the test standard GB / T 19587-2017. In this process, the positive electrode active material is used as a sample and the specific surface area is measured using a specific surface and pore size analyzer (model: Tri-Star 3020) from the American manufacturer Micromeritics.

[0295] In some embodiments, the volume distribution particle size of the positive electrode active material meets: 1 µm ≤ Dv50 ≤ 2 µm, 0.4 µm ≤ Dv10 ≤ 0.7 µm.

[0296] For example, the Dv50 value of the positive electrode active material can be 1 µm, 1.1 µm, 1.15 µm, 1.2 µm, 1.25 µm, 1.3 µm, 1.35 µm, 1.4 µm, 1.45 µm, 1.5 µm, 1.55 µm, 1.6 µm, 1.65 µm, 1.7 µm, 1.75 µm, 1.8 µm, 1.85 µm, 1.9 µm, 1.95 µm or 2 µm, or be in a range consisting of any two of the above values.

[0297] For example, the Dv10 value of the positive electrode active material can be 0.4 µm, 0.45 µm, 0.5 µm, 0.55 µm, 0.6 µm, 0.65 µm or 0.7 µm, or in a range consisting of any two of the above values.

[0298] The particle size of the positive electrode active material is relatively small, the deintercalation and intercalation pathway of lithium ions within the positive electrode active material is short, and the amount of heat generated is low. Furthermore, the particle size of the aforementioned positive electrode active material is not too small, and agglomeration is practically non-existent during the processing and manufacturing process, thus ensuring stable performance of the positive electrode active material.

[0299] In the embodiments of the present application, the volume-averaged particle size Dv50 of the material refers to the particle size corresponding to 50% of the volume distribution, and the volume-averaged particle size Dv10 refers to the particle size corresponding to 10% of the volume distribution. The particle sizes can be determined using devices and methods known in the art. For example, the positive electrode active material is used as a sample, and the Dv50 and Dv10 of the particles are measured using a Mastersizer 2000E laser particle size analyzer in accordance with test standard GB / T 19077-2016.

[0300] If the positive electrode active material includes other materials besides the lithium-containing phosphate with olivine structure, the volume distribution particle size of the positive electrode active material refers to the volume distribution particle size of all positive electrode active materials.

[0301] In some embodiments, the lithium-containing phosphate with an olivine structure is in granular form and comprises secondary particles, wherein the secondary particles comprise several primary particles, the average particle size of the primary particles being 200 nm to 500 nm. For example, the average particle size of the primary particles is 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm, 480 nm, 500 nm, or lies within a range consisting of any two of the above values.

[0302] The average particle size of the primary particles is relatively small, which means that the deintercalation and intercalation path of lithium ions in the positive electrode active material is short and the amount of heat generated is low.

[0303] In the embodiments of the present application, secondary particles refer to particles in an aggregated state formed by the aggregation of two or more primary particles. The primary and secondary particles can be easily distinguished experimentally (e.g., by taking SEM images with a scanning electron microscope). The average particle size of the primary particles can be determined from the SEM images. The SEM test parameters can be set as follows: the operating voltage (EHT) is 10.00 kV, the InLens detector is used, the working distance is 4.6 mm, and the magnification is 1000x.

[0304] In some embodiments, the positive electrode film layer further comprises one or more ternary materials, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrite. The aforementioned materials can be used as lithium replenishers, replenishing the lithium ions for the positive electrode film layer, compensating for the irreversible lithium ion loss in the system, and increasing the capacity and thus the energy density of the battery cell.

[0305] Optionally, the ternary material Li x3 A y3 Ni a3 Co b3 Mn c M3 (1-a3-b3-c3) Y3 z3, where 0 < x3 ≤ 2.1, 0 < y3 ≤ 2.1 and 0.9 ≤ x3 + y3 ≤ 2.1, 0 ≤ a3 ≤ 1, 0 ≤ b3 ≤ 1, 0 ≤ c3 ≤ 1 and 0.1 ≤ a3 + b3 + c3 ≤ 1, 1.8 ≤ z3 ≤ 3.5, A comprises one or more of Na, K and Mg, M3 comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La and Ce, and Y3 comprises one or more of O and F.

[0306] For example, the ternary material includes at least one of LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.3 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2.

[0307] In some embodiments, the mass fraction of the lithium supplement in the positive electrode film layer is 0.5% to 5%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or lies within a range consisting of any two of the values ​​mentioned above. If the mass fraction of the lithium supplement is within the range mentioned above, it can replenish lithium ions for the positive electrode film layer, compensate for the irreversible lithium ion loss in the system, and increase the capacity and thus the energy density of the battery cell.

[0308] The lithium supplement can be located in the same layer as the positive electrode active material or in a different layer. If the lithium supplement is located in a different layer than the positive electrode active material, the lithium supplement can be located in a lithium supplement layer, and the positive electrode active material can be located in the positive electrode active material layer. In other words, the positive electrode film layer comprises the lithium supplement layer and the positive electrode active material layer. The positive electrode active material layer can be located on at least one side of the positive electrode current collector, and the lithium supplement layer can be located between the positive electrode active material layer and the positive electrode current collector.Alternatively, the lithium supplement layer can be arranged on at least one side of the positive electrode current collector, and the positive electrode active material layer can be located between the lithium supplement layer and the positive electrode current collector. Optionally, the lithium supplement layer can be located between the positive electrode active material layer and the positive electrode current collector. During the cyclic charging and discharging process of the battery cell, the lithium supplement in the lithium supplement layer can be gradually released into the system to compensate for the lithium loss in the battery system.

[0309] In some embodiments, the positive electrode film layer optionally comprises a conductive element of the positive electrode. The embodiments of the present application are not subject to any particular restrictions regarding the type of conductive element of the positive electrode. By way of example, the conductive element of the positive electrode comprises at least one of superconducting carbon, conductive graphite, carbon black, carbon black, Ketjen carbon black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass fraction of the conductive element of the positive electrode is ≤ 5%, based on the mass of the positive electrode film layer.

[0310] In some embodiments, the positive electrode film layer optionally comprises a positive electrode binder. The embodiments of the present application are not subject to any particular restrictions regarding the type of positive electrode binder. By way of example, the positive electrode binder may comprise at least one of the following: polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and a fluorine-containing acrylate resin. In some embodiments, the mass fraction of the positive electrode binder is ≤ 5%, based on the mass of the positive electrode film layer.

[0311] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, the metal foil can be made of at least one material: aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy. The composite current collector can comprise a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal material of the metal layer can be aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy. For example, the polymer base layer can be polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE).

[0312] In some embodiments, the ratio of the thickness of the positive electrode current collector to the thickness of the one-sided positive electrode film layer is 0.05 to 0.3. For example, the ratio of the thickness of the positive electrode current collector to the thickness of the one-sided positive electrode film layer is 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, or lies in a range consisting of any two of the above values.

[0313] If the ratio of the thickness of the positive electrode current collector to the thickness of the one-sided positive electrode film layer is within the range mentioned above, the fast charging capability and the energy density of the battery cell can be improved.

[0314] In some embodiments, the thickness of the positive electrode current collector is 10 µm to 15 µm, optionally 12 µm to 15 µm. For example, the thickness of the positive electrode current collector is 10 µm, 10.5 µm, 11 µm, 11.5 µm, 1.2 µm, 12.5 µm, 13 µm, 13.5 µm, 14 µm, 14.5 µm, 15 µm, or lies in a range consisting of any two of the above values.

[0315] If the thickness of the positive electrode current collector is within the range mentioned above, the positive electrode current collector exhibits relatively excellent current conductivity and allows for a higher energy density of the battery cell.

[0316] In the embodiments of the present application, the thicknesses of the positive electrode film layer and the positive electrode current collector section have meanings known in the art and can be determined using devices and methods known in the art. For example, the thickness of the positive electrode sheet is measured with a high-precision micrometer, the film layer is removed from the surface of the positive electrode current collector, and the thickness of the positive electrode current collector is measured with the high-precision micrometer, wherein, in the case of single-sided coating of the positive electrode film layer, its thickness corresponds to the thickness of the positive electrode sheet minus the thickness of the positive electrode current collector, while in the case of double-sided coating, the thickness of the positive electrode film layer is (thickness of the positive electrode sheet minus thickness of the positive electrode current collector) divided by 2.

[0317] The positive electrode film layer is typically formed by applying a positive electrode paste to the positive electrode current collector, followed by drying and cold pressing. The positive electrode paste is generally formed by dispersing and uniformly stirring the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent. The solvent may be, but is not limited to, N-methyl-2-pyrrolidone (NMP).

[0318] The positive electrode sheet does not exclude further additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode sheet according to the embodiments of the present application also comprises a conductive layer of the positive electrode, which is enclosed between the positive electrode current collector and the positive electrode film layer and is arranged on the surface of the positive electrode current collector. In other embodiments, the positive electrode sheet according to the embodiments of the present application further comprises a protective layer that covers the surface of the positive electrode film layer.

[0319] In some embodiments, the positive electrode sheet also includes a conductive layer of the positive electrode, wherein the conductive layer of the positive electrode is located between the positive electrode film layer and the positive electrode current collector. The conductive layer of the positive electrode can further improve the conductivity of the positive electrode sheet and reduce the heat generation of the positive electrode sheet, thereby reducing the amount of heat generated by the battery cell.

[0320] In some embodiments, the thickness of the conductive layer of the positive electrode is 0.1 µm to 2 µm. For example, the thickness of the conductive layer of the positive electrode can be 0.1 µm, 0.5 µm, 0.8 µm, 1 µm, 1.2 µm, 1.5 µm, 1.6 µm, 1.8 µm, 2 µm, or a range consisting of any two of the above values.

[0321] If the thickness of the conductive layer of the positive electrode is within the range mentioned above, the conductivity of the positive electrode sheet can be further improved and the heat generation of the positive electrode sheet reduced, thereby reducing the heat generation of the battery cell, and at the same time increasing the energy density of the battery cell.

[0322] In the embodiments of the present application, the thickness of the conductive layer of the positive electrode has a meaning known in the art and can be determined using devices and methods known in the art. For example, a tomographic examination is carried out on the positive electrode sheet to directly measure the thickness of the conductive layer of the positive electrode.

[0323] In some embodiments, the conductive layer of the positive electrode comprises one or more of a conductive element of the positive electrode and a binder of the positive electrode.

[0324] Optionally, the mass fraction of the conductive material of the positive electrode in the conductive layer of the positive electrode is 30% to 50%. For example, the mass fraction of the conductive material of the positive electrode is 30%, 35%, 40%, 45%, 50%, or lies within a range consisting of any two of the values ​​mentioned above.

[0325] For example, the conductive material of the positive electrode comprises one or more of superconducting carbon, conductive graphite, carbon black, carbon black, Ketjen carbon black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive material of the positive electrode within the conductive layer of the positive electrode can improve the conductivity of the conductive layer of the positive electrode, thereby improving the conductivity of the positive electrode sheet and reducing the amount of heat generated by the battery cell.

[0326] Optionally, the mass fraction of the binder in the conductive layer of the positive electrode is 50% to 70%. For example, it is 50%, 60%, 65%, 70%, or lies within a range consisting of any two of the values ​​mentioned above.

[0327] For example, the positive electrode binder comprises one or more of the following: polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorine-containing acrylate resin. The positive electrode binder in the conductive layer of the positive electrode can improve the bonding performance between the positive electrode current collector and the positive electrode film layer, and enhance the structural stability of the positive electrode sheet. [Separator]

[0328] In the embodiments of the present application, the separator comprises a base film with a porous structure.

[0329] In some embodiments, the base film comprises at least one of glass fiber, nonwoven fabric, and polyolefin. The base film can be a single-layer film or a multi-layer composite film without any particular restriction. If the base film is a multi-layer composite film, the materials of each layer can be the same or different without any particular restriction.

[0330] Optionally, the polyolefin comprises at least one of polyethylene, polypropylene and polyvinylidene fluoride.

[0331] In some embodiments, the porosity of the base film is 20% to 70%, optionally 35% to 60%. For example, the porosity of the base film is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or lies within a range consisting of any two of the values ​​mentioned above.

[0332] If the porosity of the base film in the embodiments of the present application is within the above-mentioned range, the migration capability of lithium ions in the separator can be improved and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0333] In the embodiments of the present application, porosity refers to the percentage of the pore volume relative to the total volume of the separator. The porosity can be tested in accordance with standard GB / T 36363-2018 "Polyolefin separators for battery cells". It should be noted that the actual test process may employ test procedures that deviate from the standard to obtain more accurate measurements, depending on test equipment variations, measurement errors, and the need to minimize the influence of porosity measurements.

[0334] In some embodiments, the thickness of the base film is 6 µm to 12 µm, optionally 6 µm to 9 µm. For example, the thickness of the base film is 6 µm, 6.5 µm, 7 µm, 7.5 µm, 8 µm, 8.5 µm, 9 µm, 9.5 µm, 10 µm, 10.5 µm, 11 µm, 11.5 µm, 12 µm, or lies in a range consisting of any two of the above values.

[0335] If the thickness of the base film is within the range mentioned above, the migration path of the lithium ions in the base film is shorter, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation.

[0336] In the embodiments of the present application, the separator can be a base film. Optionally, the separator additionally comprises a functional layer arranged on at least one side of the base film. The functional layer can comprise inorganic particles to increase the heat resistance of the separator. Optionally, a functional layer is arranged on each side of the base film.

[0337] In some embodiments, the functional layer comprises a first functional layer and a second functional layer, wherein the first functional layer is located on one side of the base film, the first functional layer comprises first inorganic particles, the second functional layer is located on the other side of the base film, and the second functional layer comprises composite particles, wherein the composite particles comprise second inorganic particles and several non-fluoropolymer particles, wherein the second inorganic particles adhere to the surface of the non-fluoropolymer particles and / or are dispersed inside the non-fluoropolymer particles.

[0338] The first functional layer and the second functional layer exhibit good heat resistance and can increase the heat resistance of the separator.

[0339] Optionally, the first functional layer may include a binder, optionally at least one of a fluorine-containing binder or a polyacrylic binder, such as polyvinylidene fluoride.

[0340] Optionally, the first inorganic particles include one or more of silicon dioxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium dioxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. These initial inorganic particles can increase the heat resistance of the first functional layer.

[0341] In the embodiments of the present application, the thickness of the base film has a meaning known in the art and can be determined using means and devices known in the art. For example, a freshly manufactured separator can be taken as a sample, or a fully discharged battery cell (discharged to the lower limit cutoff, so that the battery's state of charge is approximately 0% SOC) can be reverse disassembled and the separator removed. The separator is dried and used as a sample. Subsequently, the separator is cut with an ion beam cutter to produce a cross-section. The thickness of the separator cross-section and its various layers is then measured using a scanning electron microscope.

[0342] The non-fluorinated polymer particles in the second functional layer are non-fluorinated polymers. For example, the non-fluorinated polymer particles comprise an acrylate copolymer. Optionally, the acrylate copolymer comprises an acrylate-acrylonitrile-acrylamide-propylene copolymer. The acrylate copolymer is characterized by excellent bonding performance and high bond stability with the base film. The molar percentage of the individual monomers in the copolymer can be any desired ratio, for example, 35%:30%:15%:20%, 40%:20%:10%:30%, 45%:15%:20%:20%, etc.

[0343] Within the composite particles, the second set of inorganic particles prevents the non-fluoropolymer particles from bonding during the high-temperature granulation process. This creates pores in the composite particles that promote lithium ion transport and improve the separator's ion conductivity. Additionally, these second set of inorganic particles increase the bulk modulus of the composite particles, making them less prone to deformation during charging and discharging. This stabilizes the separator's structure, improves the battery cell's kinetic performance, and enhances fast-charging capabilities. Optionally, the second functional layer is positioned closer to the negative electrode sheet than the first.Since the composite particles do not deform easily, the separator generally does not cause any side effects such as pressure on the negative electrode sheet, so the kinetic performance of the negative electrode sheet remains stable. Accordingly, the first functional layer is located close to the positive electrode sheet.

[0344] Optionally, the second inorganic particles comprise one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. Silicon oxide is also optionally included. These second inorganic particles can enhance the heat resistance of the second functional layer and, together with non-fluorinated polymers, form composite particles to further improve the separator's cycle stability and kinetic performance, thereby enhancing the battery cell's cycle life and fast-charging performance.

[0345] The average particle size of the second inorganic particle is 5 nm to 100 nm, optionally 10 nm to 100 nm, and optionally 5 nm to 20 nm. For example, the average particle size of the second inorganic particle could be 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, or a range consisting of any two of the above values. Having the average particle size of the second inorganic particle within the above range is advantageous for increasing the heat resistance and bulk modulus of the composite particles.

[0346] In the embodiments of the present application, the average particle size of the second inorganic particles has a meaning known in the art and can be determined using devices and methods known in the art. For example, after receiving the separator, it is dried and used as a sample. Subsequently, the separator is cut with an ion beam cutter to produce a cross-section. The particle size of the second inorganic particles in the separator is then measured with a scanning electron microscope. The particle sizes of several, for example 50, second inorganic particles are measured, and the average value is calculated as the average particle size of the second inorganic particles.

[0347] In some embodiments, the ionic conductivity of the separator is 0.3 mS / cm to 0.6 mS / cm. For example, the ionic conductivity of the separator is 0.3 mS / cm, 0.35 mS / cm, 0.4 mS / cm, 0.45 mS / cm, 0.5 mS / cm, 0.55 mS / cm, 0.6 mS / cm, or lies within a range consisting of any two of the above values.

[0348] If the ionic conductivity of the separator is within the range mentioned above, the migration capability of the lithium ions in the separator can be further improved, thereby improving the fast charging performance of the battery cell.

[0349] In the embodiments of the present application, the ionic conductivity of the separator has a meaning known in the art and can be determined using devices and methods known in the art, for example:

[0350] Production of a 2025 button cell for testing purposes: A lithium sheet is placed in a negative electrode casing of the battery within a vacuum glove box. 150 µL of electrolyte solution is added. The electrolyte solution used is a 1 mol / L LiPF6 solution with an EC / EMC / DEC ratio of 3 / 5 / 2 (mass ratio). A separator (with an area of ​​3.14 cm²) is then used. 2 and a thickness of 12 µm) is placed on the lithium sheet. A further 25 µL of electrolyte solution is added. Finally, a positive electrode sheet (the positive electrode sheet can be the one from embodiment 1) is placed on top before the cell is encapsulated. The assembled button cell is removed from the vacuum glove box and stored for 24 hours to prepare for subsequent tests.

[0351] Test: At an electrochemical workstation, measurements are taken in the frequency range of 10 -1 up to 10 6The frequency was measured in Hz to determine a separator resistance R3. The ionic conductivity σ (unit: mS / cm) is calculated using the following formula: σ=L / (Rb×S) where R b L represents the resistance of the separator, while L denotes the thickness and S the area of ​​the separator to be tested. [Electrolyte solution]

[0352] In some embodiments, the battery cell also includes an electrolyte solution.

[0353] During the charging and discharging process of the battery cell, the active ions, such as lithium ions, migrate between the positive and negative electrode sheets for intercalation and deintercalation, and the electrolyte solution takes on the task of conducting the active ions between the positive and negative electrode sheets.

[0354] In the embodiments of the present application, the conductivity of the electrolyte solution is 13 mS / cm to 20 mS / cm, optionally 15 mS / cm to 20 mS / cm. By way of example, the conductivity of the electrolyte solution at room temperature is 13 mS / cm, 13.5 mS / cm, 14 mS / cm, 14.5 mS / cm, 15 mS / cm, 15.5 mS / cm, 16 mS / cm, 16.5 mS / cm, 17 mS / cm, 17.5 mS / cm, 18 mS / cm, 18.5 mS / cm, 19 mS / cm, 19.5 mS / cm or 20 mS / cm, or lies in a range consisting of any two of the above values.

[0355] If the conductivity of the electrolyte solution at room temperature, for example 25 °C, is within the range mentioned above, the migration rate of lithium ions in the electrolyte solution is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0356] In the embodiments of the present application, the conductivity of the electrolyte solution at room temperature, for example 25 °C, is the ionic conductivity, which can be determined using devices and methods known in the art, for example by tests with reference to the industry standard HG-T 4067-2015.

[0357] In some embodiments, the viscosity of the electrolyte solution at room temperature is between 2.3 mPa·s and 3.5 mPa·s. For example, the viscosity of the electrolyte solution is 2.3 mPa·s, 2.4 mPa·s, 2.5 mPa·s, 2.6 mPa·s, 2.7 mPa·s, 2.8 mPa·s, 2.9 mPa·s, 3.0 mPa·s, 3.1 mPa·s, 3.2 mPa·s, 3.3 mPa·s, 3.4 mPa·s, 3.5 mPa·s, or lies within a range consisting of any two of the values ​​mentioned above.

[0358] If the viscosity of the electrolyte solution at room temperature, for example 25 °C, is within the range mentioned above, the migration rate of lithium ions in the electrolyte solution is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and thus improving the fast charging performance of the battery cell.

[0359] In the embodiments of the present application, the viscosity of the electrolyte solution has a meaning known in the art and can be determined using devices and methods known in the art. For example, it can be determined according to GB / T 10247-2008.

[0360] In some embodiments, the density of the electrolyte solution at room temperature, for example 25 °C, is 1.05 g / mL to 1.35 g / mL. For example, the density of the electrolyte solution is 1.05 g / mL, 1.10 g / mL, 1.15 g / mL, 1.2 g / mL, 1.25 g / mL, 1.3 g / mL, 1.35 g / mL, or lies within a range consisting of any two of the above values.

[0361] If the density of the electrolyte solution is within the range mentioned above, the migration rate of lithium ions in the electrolyte solution is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and thus improving the fast charging performance of the battery cell.

[0362] In the embodiments of the present application, the density of the electrolyte solution has a meaning known in the art and can be determined using devices and methods known in the art, for example by reference to GB / T 2013-2010 for testing.

[0363] The electrolyte solution comprises an organic solvent and an electrolyte salt. There are no particular restrictions on the types of organic solvents and electrolyte salts used, and they can be selected according to the actual requirements.

[0364] In some embodiments, the organic solvent comprises a chain-like carboxylic ester solvent, and the mass fraction of the chain-like carboxylic ester solvent, based on the mass of the electrolyte solution, is greater than or equal to 4% and less than or equal to 65%, optionally greater than or equal to 8.5% and less than or equal to 65%, optionally 25% to 60%. For example, the mass fraction of the chain-like carboxylic ester solvent is 4%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or lies within a range consisting of any two of the values ​​mentioned above.

[0365] If the mass fraction of the chain-like carboxylic acid ester solvent is within the range mentioned above, the viscosity of the electrolyte solution system is relatively low, which has a positive effect on the migration of lithium ions.

[0366] In some embodiments, the chain-like carboxylic acid ester solvent comprises a compound represented by formula I, where in Formula I, R1 comprises a hydrogen atom, a halogen atom, a C1 to C5 alkyl group or a halogenated C1 to C5 alkyl group, R2 comprises a C1 to C5 alkyl group or a halogenated C1 to C5 alkyl group.

[0367] The aforementioned chain-like carboxylic acid ester solvent exhibits high conductivity, which has a positive effect on improving the fast-charging capability of the battery cell.

[0368] Optionally, R1 comprises a hydrogen atom, a halogen atom, a C1 to C3 alkyl group, or a halogenated C1 to C3 alkyl group. Furthermore, optionally, R1 comprises a hydrogen atom, a halogen atom, a C1 to C2 alkyl group, or a halogenated C1 to C2 alkyl group.

[0369] Optionally, R2 comprises a C1 to C3 alkyl group or a halogenated C1 to C3 alkyl group. Furthermore, optionally, R2 comprises a C1 to C2 alkyl group or a halogenated C1 to C2 alkyl group.

[0370] In the embodiments described above, the halogen atom comprises one or more fluorine, chlorine, bromine, and iodine atoms. Optionally, the halogen atom comprises a fluorine atom.

[0371] In the above embodiments, the haloalkyl group comprises one or more fluoroalkyl groups, chloroalkyl groups, bromoalkyl groups, and iodoalkyl groups. Optionally, the haloalkyl group comprises a fluoroalkyl group.

[0372] For example, the chain-like carboxylic acid ester solvent comprises one or more of the compounds represented by formulas I-1 to I-8,

[0373] In some embodiments, the organic solvent also comprises a carbonate solvent.

[0374] Optionally, the carbonate solvent comprises one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The aforementioned carbonate solvent and the chain-like carboxylic acid ester solvent are used together to improve the conductivity of the electrolyte solution at room temperature, which has a positive effect on the migration of lithium ions.

[0375] Optionally, the mass fraction of the carbonate solvent in the electrolyte solution can be 25% to 60%, or optionally 25% to 42.5%. For example, the mass fraction of the carbonate solvent in the electrolyte solution could be 25%, 28%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 45%, 48%, 50%, 55%, 60%, or any combination of these values. The carbonate solvent with the mass fraction specified above can further improve the conductivity of the electrolyte solution at room temperature, which has a positive effect on the migration of lithium ions.

[0376] For example, the carbonate solvent comprises one or more of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, wherein the mass fraction of the carbonate solvent is 25% to 42.5%.

[0377] In some embodiments, the electrolyte solution also contains an additive, which may include a film-forming additive for the negative electrode, a film-forming additive for the positive electrode, and an additive that can improve certain battery performance characteristics, such as an additive that improves the battery's overcharge behavior, an additive that improves the battery's high-temperature performance, and an additive that improves the battery's low-temperature performance.

[0378] In some embodiments, the additive contains one or more carbonate additives, sulfur-containing additives, and lithium salt additives, and optionally at least two of these. The aforementioned additive can improve the performance of the interfacial films on the positive electrode side and / or the negative electrode side, which has a positive effect on improving the fast-charging performance of the battery cell and its cycle life.

[0379] In some embodiments, the mass fraction of the additive in the electrolyte solution is 1% to 10%, optionally 2% to 8%, and further optionally 3.5% to 8%. For example, the mass fraction of the additive in the electrolyte solution is 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or lies within a range consisting of any two of the values ​​mentioned above.

[0380] The additive with the above-mentioned mass fraction can effectively improve the performance of the interfacial films on the positive electrode side and / or the negative electrode side, which has a positive effect on improving the fast charging performance of the battery cell and the cycle performance.

[0381] For example, the carbonate additive comprises one or more of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0382] For example, the sulfur-containing additive includes one or more of ethylene sulfate DTD, bis(ethylene sulfate) 2-DTD, butylene sulfite BS, 1,3-propanesultone PS, ethylene sulfite ES and methylenemethanedisulfonate MMDS.

[0383] Optionally, the lithium salt additive includes one or more of lithium difluorophosphate LiPO2F2, lithium difluoro(oxalato)borate LiDFOB, lithium tetrafluoroborate LiBF4, lithium bis(oxalato)borate LiBOB.

[0384] Optionally, the mass fraction of vinylene carbonate (VC) in the electrolyte solution is 0.5% to 9%, optionally 2% to 6%.

[0385] Optionally, the mass fraction of fluoroethylene carbonate (FEC) in the electrolyte solution is 0.1% to 4%, optionally 0.5% to 3%.

[0386] Optionally, the mass fraction of vinylene carbonate VC in the electrolyte solution is 0.5% to 9% and the mass fraction of fluoroethylene carbonate FEC in the electrolyte solution is 0.1% to 4%.

[0387] Optionally, the mass fraction of vinylene carbonate VC in the electrolyte solution is 2% to 6% and the mass fraction of fluoroethylene carbonate FEC in the electrolyte solution is 0.5% to 3%.

[0388] In some embodiments, the electrolyte salt comprises a lithium salt, and the lithium salt comprises one or more fluorinated sulfonylimide salts and lithium hexafluorophosphate (LiPF6). The aforementioned lithium salt is readily dissociated, which promotes the rapid migration of lithium ions. Furthermore, the electrolyte solution system is relatively stable and does not decompose easily, which can improve the cycle life of the battery cell.

[0389] Optionally, the fluorine-containing sulfonylimide salt comprises one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium bis(trifluoromethanesulfonyl)imide LiTFSI.

[0390] Optionally, the lithium salt comprises lithium bis(fluorosulfonyl)imide LiFSI and lithium hexafluorophosphate LiPF6. The molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF6 is 0.5 mol / L to 1.0 mol / L.

[0391] For example, the molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is 0.4 mol / L to 0.5 mol / L and the molar concentration of lithium hexafluorophosphate LiPF6 is 0.7 mol / L.

[0392] For example, the molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is 0.5 mol / L and the molar concentration of lithium hexafluorophosphate LiPF6 is 0.5 mol / L.

[0393] For example, the molar concentration of lithium bis(fluorosulfonyl)imide LiFSI is 0.2 mol / L and the molar concentration of lithium hexafluorophosphate LiPF6 is 0.8 mol / L.

[0394] Optionally, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate LiPF6 is 0.2 to 1.0, optionally 0.2 to 0.5. For example, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate LiPF6 is 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or lies within a range consisting of any two of the values ​​mentioned above.

[0395] In the embodiments of the present application, the type and concentration of the inorganic components / lithium salts in the electrolyte solution have meanings known in the art and can be determined using devices and methods known in the art. For example, the inorganic components / lithium salts in the electrolyte solution can be analyzed qualitatively or quantitatively by ion chromatography in accordance with the standard JY / T020-1996 "General rules for ion chromatography analysis methods".In the embodiments of the present application, a newly prepared electrolyte solution can be taken as a sample, a free electrolyte solution from a fresh battery can be taken as a sample, or a completely discharged battery (it has been discharged to the discharge cut-off voltage, so that the state of charge of the battery is approximately 0% SOC) can be reverse disassembled and the free electrolyte solution obtained from the battery taken as a sample. The sample is analyzed using the ion chromatography analytical method.

[0396] In the embodiments of the present application, the type and content of the organic components in the electrolyte solution have meanings known in the art and can be determined using devices and methods known in the art. For example, reference can be made to GB / T9722-2006 "General rules for the gas chromatography of chemical reagents" to carry out a qualitative and quantitative analysis of organic components in the electrolyte solution by means of gas chromatography.In the embodiments of the present application, a newly prepared electrolyte solution can be taken as a sample, a free electrolyte solution from a fresh battery can be taken as a sample, or a completely discharged battery (it has been discharged to the discharge cut-off voltage, so that the state of charge of the battery is approximately 0% SOC) can be reverse disassembled and the free electrolyte solution obtained from the battery taken as a sample. The sample is analyzed using the ion chromatography analytical method.

[0397] In the embodiments of the present application, the components are classified after quantitative and qualitative analysis of all components in the electrolyte solution. The chain-like carboxylic acid ester solvents and carbonate solvents (such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate) are classified as constituents of the organic solvent. The mass fraction of the individual components is calculated based on the mass of the electrolyte solution at 100%.

[0398] The carbonate additive (such as vinylene carbonate, fluoroethylene carbonate), the sulfur-containing additive, and the lithium salt additive are classified as additives to the electrolyte solution. The mass fraction of each component is calculated based on the mass of the electrolyte solution at 100%.

[0399] In some embodiments, the battery cell meets the following conditions: 2.45 g / Ah ≤ d / A ≤ 3.5 g / Ah, optionally 2.45 g / Ah ≤ d / A ≤ 3.3 g / Ah, where d represents the mass of the electrolyte solution in the battery cell in grams and A represents the nominal capacity of the battery cell in Ah. For example, d / A can be 3.5 g / Ah, 3.3 g / Ah, 3.2 g / Ah, 3.0 g / Ah, 2.8 g / Ah, 2.5 g / Ah, 2.45 g / Ah, or a range consisting of any two of the above values.

[0400] d / A can reflect the liquid retention capacity of the electrolyte solution. If d / A is within the range mentioned above, the electrolyte solution can better wet the positive and negative electrode sheets and increase the migration rate of lithium ions in the liquid phase, which has a positive effect on the fast-charging capability of the battery cell.

[0401] In the embodiments of the present application, d / A of the battery cell is understood to be the liquid retention coefficient, which can be determined using devices and methods known in the art. For example, according to GB / T31486-2015 "Electrical performance requirements and test methods for traction batteries for electric vehicles" with an upper charging limit voltage of the battery of 3.65 V and a discharge cut-off voltage of the battery of 2.0 V, the following can be explained:

[0402] The battery cell is charged at 25 °C at 0.33 C to 3.65 V, then further charged at a constant voltage to 0.05 C. It is then discharged at a constant current of 0.33 C to 2.0 V. The discharged capacity A is used as the denominator. The battery cell is weighed as M0. The positive electrode, the negative electrode, the separator, and the electrolyte solution are disassembled, with the free electrolyte solution collected in a bag. All solid components (including, but not limited to, the positive and negative electrodes, the separator, and other mechanical components of the disassembled battery cell that contribute to M0) are dried in a drying box at 60 °C for over 4 hours. Subsequently, all components of the battery cell are weighed as M1. The difference between M0 and M1 is used as the counter.The fluid retention coefficient is equal to the value obtained by dividing the weight difference d between M0 and M1 by the capacity A.

[0403] In some embodiments, the positive electrode sheet, the separator and the negative electrode sheet can be formed into an electrode arrangement by a winding process and / or a stacking process.

[0404] Fig. 1 and Fig. Figure 2 shows schematic representations of the structure of the battery cell.

[0405] In some embodiments, the battery cell 7 can comprise a housing 20.

[0406] In some embodiments, the housing 20 of the battery cell 7 can be a hard housing, for example, a hard plastic housing, an aluminum housing, a steel housing, etc. The housing 20 of the battery cell 7 can also be a soft packaging, for example, a bag-like soft packaging. The material of the soft packaging can be plastic, for example, at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0407] The housing 20 has a hollow structure and the housing 20 can be used to encapsulate the electrode arrangement 10 and the electrolyte solution.

[0408] The method for manufacturing the battery cell 7 according to the embodiments of the present application is known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte solution can be assembled to form a battery cell 7. For example, the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly 10 by a winding process and / or a stacking process. The electrode assembly 10 is inserted into a housing 20. After drying, an electrolyte solution is injected, and after vacuum sealing, standing, formation, and calibration, a battery cell 7 is obtained.

[0409] In some embodiments, the housing 20 comprises a housing body 21 and an end cover 22, wherein the housing body 21 has an opening and the end cover 22 covers the opening.

[0410] The shape of the housing body 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 has a cylindrical structure, a cylindrical housing body can be selected; if the electrode assembly 10 has a cuboid structure, a cuboid housing body can be selected. Optionally, both the electrode assembly 10 and the housing body 21 can have a cuboid structure.

[0411] In some embodiments, the housing body 21 is made of steel. Steel has high mechanical strength and does not deform easily, which can improve the operational reliability and cycle life of the battery cell. Optionally, steel constitutes the largest proportion of material in the housing body 21.

[0412] Optionally, the thickness of the casing 21 is 0.1 mm to 0.5 mm, and optionally 0.2 mm to 0.35 mm. For example, the thickness of the casing 21 could be 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, or a range consisting of any two of the above values. If the thickness of the casing 21 is within the above range, the mechanical strength of the casing 21 is relatively high, which can improve the operational reliability and cycle life of the battery cell 7. Furthermore, the casing 21 occupies less space, and its internal volume is relatively large, which contributes to increasing the energy density of the battery cell 7.

[0413] With regard to the external shape of the electrode assembly 10, the electrode assembly 10 comprises a main body section 12, a positive electrode tab 111, and a negative electrode tab 112, wherein the positive electrode tab 111 and the negative electrode tab 112 project from the main body section 12. The positive electrode tab 111 is the portion of the positive electrode sheet that is not coated with the active material layer, and the negative electrode tab 112 is the portion of the negative electrode sheet that is not coated with the active material layer. The positive electrode tab 111 and the negative electrode tab 112 serve to conduct the current out of the main body section 12.

[0414] The positive electrode tab 111 and the negative electrode tab 112 can originate from the same side of the main body section 12 or from opposite sides.

[0415] Optionally, the number of positive electrode tabs 111 on the same side of the main body section 12 is at least one and optionally at least two. The at least two positive electrode tabs 111 can increase the current-carrying capacity of the positive electrode tabs 111.

[0416] Optionally, the number of negative electrode tabs 112 on the same side of the main body section 12 is at least one and optionally at least two. The at least two negative electrode tabs 112 can increase the current-carrying capacity of the negative electrode tabs 112.

[0417] In some embodiments, the battery cell 7 also includes a positive electrode terminal 31, and the positive electrode terminal 31 is electrically connected to the positive electrode tab 111. Optionally, the positive electrode terminal 31 and the positive electrode tab 111 are welded together, and the positive electrode terminal 31 and the positive electrode tab 111 can be connected via an adapter or without an adapter. Optionally, the positive electrode terminal 31 and the positive electrode tab 111 are not connected via an adapter; that is, the positive electrode terminal 31 and the positive electrode tab 111 are directly welded together, which can reduce the resistance at the connection and has a positive effect on reducing the overall internal resistance of the battery cell 7.

[0418] In some embodiments, the battery cell 7 also includes a negative electrode terminal 32, and the negative electrode terminal 32 is electrically connected to the negative electrode tab 112. Optionally, the negative electrode terminal 32 and the negative electrode tab 112 are welded together, and the negative electrode terminal 32 and the negative electrode tab 112 can be connected to each other via an adapter or without an adapter. Optionally, the negative electrode terminal 32 and the negative electrode tab 112 are not connected to each other via an adapter; that is, the negative electrode terminal 32 and the negative electrode tab 112 are welded directly, which reduces the resistance at the connection, thus positively reducing the overall internal resistance of the battery cell 7.

[0419] Optionally, the number of positive electrode terminals 31 on the same side of the main body section 12 is at least one, optionally at least two. The at least two positive electrode terminals 31 can increase the current-carrying capacity of the positive electrode terminals 31.

[0420] Optionally, the current passage area of ​​the positive electrode terminals 31 on one side is 150 mm². 2 up to 1000 mm 2 , optional 200 mm 2 up to 1000 mm 2 The current-carrying area of ​​the positive electrode terminals 31 on one side refers to the sum of the current-carrying areas of all positive electrode terminals 31 located on the same side of the main body section 12. The current-carrying area of ​​the positive electrode terminal 31 can be understood as the cross-sectional area of ​​the positive electrode terminal 31 that is perpendicular to the thickness direction of the end cap 22.

[0421] For example, the current-carrying area of ​​the positive electrode terminals 31 on one side can be 150 mm² 2 , 200 mm 2 , 210 mm 2 , 250 mm 2 , 280 mm 2 , 300 mm 2 , 320 mm 2 , 350 mm 2 , 380 mm 2 , 400 mm 2 , 450 mm 2 , 500 mm 2 , 550 mm 2 , 600 mm 2 , 650 mm 2 , 700 mm 2 , 750 mm 2 , 800 mm 2 , 850 mm 2 , 900 mm 2 , 950 mm 2 , 1000 mm 2 or lie within a range consisting of any two of the above values.

[0422] Optionally, the number of negative electrode terminals 32 on the same side of the main body section 12 is at least one, optionally at least two. The at least two negative electrode terminals 32 can increase the current-carrying capacity of the negative electrode terminals 32.

[0423] Optionally, the current-carrying area of ​​the negative electrode terminals is 32 mm² on one side. 2 up to 1000 mm 2 , optional 200 mm 2 up to 1000 mm 2 The current-carrying area of ​​the negative electrode terminals 32 on one side refers to the sum of the current-carrying areas of all negative electrode terminals 32 located on the same side of the main body section 12. The current-carrying area of ​​the negative electrode terminal 32 can be understood as the cross-sectional area of ​​the negative electrode terminal 32 perpendicular to the thickness direction of the end cap 22.

[0424] For example, the current-carrying area of ​​the negative electrode terminals 32 can be 150 mm² on one side. 2 , 200 mm 2 , 210 mm 2 , 250 mm 2 , 280 mm 2 , 300 mm 2 , 320 mm 2 , 350 mm 2 , 380 mm 2, 400 mm 2 , 450 mm 2 , 500 mm 2 , 550 mm 2 , 600 mm 2 , 650 mm 2 , 700 mm 2 , 750 mm 2 , 800 mm 2 , 850 mm 2 , 900 mm 2 , 950 mm 2 , 1000 mm 2 or lie within a range consisting of any two of the above values.

[0425] As in Fig. As shown in Figure 10, in some embodiments of the present application, the battery cells 7 can be assembled into a battery module 6 according to the embodiments of the present application. The number of battery cells 7 contained in the battery module 6 can be one or more, and the exact number can be adapted depending on the application and capacity of the battery module 6.

[0426] If multiple battery cells 7 are present, they can be connected in series, parallel, or in a mixed circuit, where a mixed circuit means that both series and parallel connections exist between the multiple battery cells 7. The multiple battery cells 7 can be connected directly in series, parallel, or in a mixed circuit, and the resulting assembly can be housed in a receiving section of the battery module 6. Alternatively, the multiple battery cells 7 can first be connected in series, parallel, or in a mixed circuit to form a battery module 6. Multiple battery modules 6 can then be further connected in series, parallel, or in a mixed circuit to form a complete assembly and housed in the receiving section.Optionally, the battery module 6 can also include a recording section with a recording space, and the multiple battery cells 7 are recorded in the recording space.

[0427] As in Fig. As shown in Figure 11, in some embodiments the aforementioned battery modules 6 can also be assembled into a battery pack 2. The number of battery modules 6 contained in the battery pack 2 can be adjusted depending on the application and capacity of the battery pack. The battery device can be either a single battery module 6 or a battery pack 2.

[0428] The battery pack 2 can comprise a housing 5 and several battery modules 6 arranged within the housing 5. The housing 5 comprises a first housing section 5a and a second housing section 5b. The housing 5 has a receiving space 5c. The first housing section 5a serves to cover the second housing section 5b and form an enclosed space for receiving the battery module 6. The multiple battery modules 6 can be arranged within the housing 5 in any configuration.

[0429] The first box body section 5a and the second box body section 5b overlap each other, and together they define a receiving space 5c for the battery cell. The second box body section 5b can have a hollow structure with one open side. The first box body section 5a has a plate-like structure. The first box body section 5a covers the open side of the second box body section 5b, thus forming the box body 5 with the receiving space 5c. Alternatively, the first box body section 5a and the second box body section 5b can each have a hollow structure with one open side. The open side of the first box body section 5a covers the open side of the second box body section 5b, thus forming the box body 5 with the receiving space 5c.Of course, the first box body section 5a and the second box body section 5b can have different shapes, for example the shape of a cylinder, a cuboid and the like.

[0430] To increase the tightness of the connection between the first box body section 5a and the second box body section 5b, a sealing element, such as a sealant, a sealing ring, etc., can also be provided between the first box body section 5a and the second box body section 5b.

[0431] Assuming that the first box body section 5a covers the top of the second box body section 5b, the first box body section 5a can also be referred to as the upper box cover and the second box body section 5b as the lower box body.

[0432] In some embodiments, the temperature of the external environment in which the battery pack 2 is located during the charging process of the battery pack 2 or any battery cell of which the battery pack 2 consists, from the state of charge (SOC) of 0% to 100% is 30°C.

[0433] In some embodiments, the temperature of the external environment in which the battery pack 2 is located during the charging process of the battery pack 2 or any battery cell of which the battery pack 2 consists, from the state of charge (SOC) of 10% to 80% is 30°C.

[0434] In some embodiments, the charging process of battery pack 2, or of any battery cell comprising battery pack 2, from a state of charge of 10% to 80% comprises several charging steps. The difference between the maximum state of charge of any one charging step within these multiple charging steps and the maximum state of charge in the adjacent charging step is less than or equal to the state of charge of 5%, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, or lies within a range consisting of any two of the aforementioned values.

[0435] The charging process of battery pack 2, or any individual battery cell comprising battery pack 2, from a state of charge of 10% to 40%, involves several charging steps. Each charging step can be performed at any charging rate between 5C and 10C. The charging rate for each step can be any value from 5C, 5.5C, 6C, 6.5C, 7C, 7.5C, 8C, 8.5C, 9C, 9.5C, or 10C, or any combination of these two values.

[0436] For example, the charging step of the charging process of battery pack 2 or any battery cell of which battery pack 2 consists, from 10% to 80%, can be carried out as follows: With a constant current of 5.0 C, charging from 10% SOC to 15% SOC is achieved. With a constant current of 5.0 C, charging from 15% SOC to 20% SOC is achieved. With a constant current of 5.0 C, charging from 20% SOC to 25% SOC is achieved. With a constant current of 5.0 C, charging from 25% SOC to 30% SOC is achieved. With a constant current of 5.0 C, charging from 30% SOC to 35% SOC is achieved. With a constant current of 5.0 C, charging from 35% SOC to 40% SOC is achieved. With a constant current of 4.6 C, charging from 40% SOC to 45% SOC is achieved. With a constant current of 4.3C, charging from 45% SOC to 50% SOC is achieved. With a constant current of 4.0 C, charging from 50% SOC to 55% SOC is achieved. With a constant current of 3.7 C, charging from 55% SOC to 60% SOC is achieved. With a constant current of 3.4 C, charging takes place from 60% SOC to 65% SOC. With a constant current of 3.1 C, charging from 65% SOC to 70% SOC is achieved. With a constant current of 2.9 C, charging from 70% SOC to 75% SOC is achieved. With a constant current of 2.7 C, the battery is charged from 75% SOC to 80% SOC.

[0437] In some embodiments, the charging time of the charging process of battery pack 2, or of any battery cell comprising battery pack 2, from a state of charge of 10% to 80% is less than or equal to 10.5 minutes, optionally from 5 minutes to 10.5 minutes. The temperature of the external environment of battery pack 2 at a state of charge of 10% is room temperature, for example, 30 °C. By way of example, the charging time of the charging process of battery pack 2 from a state of charge of 10% to 80% is 10.5 minutes, 10 minutes, 9.5 minutes, 9 minutes, 8.5 minutes, 8 minutes, 7.5 minutes, 7 minutes, 6.5 minutes, 6 minutes, 5.5 minutes, 5 minutes, or lies in a range consisting of any two of the above values.

[0438] In some embodiments, the volumetric energy density of the battery cell is 390 Wh / L to 500 Wh / L and optionally 410 Wh / L to 470 Wh / L. For example, the volumetric energy density of the battery cell is 390 Wh / L, 400 Wh / L, 410 Wh / L, 420 Wh / L, 430 Wh / L, 440 Wh / L, 450 Wh / L, 460 Wh / L, 470 Wh / L, 480 Wh / L, 490 Wh / L, 500 Wh / L, or lies within a range consisting of any two of the above values. The volumetric energy density of the battery cell is higher.

[0439] In the embodiments of the present application, the volume energy density of the battery cell has a meaning known in the art and can be determined using devices and methods known in the art. For example, with an upper charging limit voltage of the battery of 3.65 V and a discharge cut-off voltage of the battery of 2.0 V, the following is explained:

[0440] The battery cell is charged at 25 °C with a constant current of 0.33 C to 3.65 V, then charged with a constant voltage to 0.05 C, and finally discharged with a constant current of 0.33 C to 2.0 V. The discharge capacity A0 is recorded at this point in Ah. The length, width, and height of the battery cell are measured with calipers (usually based on the battery casing size, excluding the height of the electrode terminals and the insulating film outside the casing). The volume V0 of each battery is calculated in L. The volumetric energy density of the battery cell, VED = (A0 × discharge platform voltage) / VO, is given in Wh / L. Power-consuming device

[0441] The second aspect of the embodiments of the present application provides a power-consuming device comprising a battery device according to the embodiments of the present application, for example, a battery cell, a battery module, or a battery pack. The battery cell, battery module, or battery pack can be used as a power source for the power-consuming device or as an energy storage device for the power-consuming device. The power-consuming devices can be vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. The vehicle can be a fuel-powered vehicle, a gas-powered vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or a range-extender vehicle, etc. The spacecraft includes an aircraft, a rocket, a space transporter, and a spacecraft, etc.The term "electric toy" includes stationary or mobile electric toys such as a game console, an electric toy car, an electric toy ship, and an electric toy airplane, etc. The term "electric tool" includes metal cutting tools, grinding tools, assembly tools, and railway tools, for example, an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, a hammer drill, a concrete vibrator, and an electric planer, etc. The embodiments of the present application do not constitute any particular restrictions on the aforementioned power-consuming devices.

[0442] The power-consuming device can be equipped with a battery cell, a battery module or a battery pack, depending on its usage requirements.

[0443] Fig.Figure 12 is a schematic representation of a power-consuming device 1 as an example. The power-consuming device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the power-consuming device 1's requirements for high power and high energy density, a battery pack or battery module can be used.

[0444] Inside the power-consuming device 1, a battery pack 2 is arranged. The battery pack 2 can be located at the bottom, top, or rear of the power-consuming device 1. The battery pack 2 can be used to supply power to the power-consuming device 1. For example, the battery pack 2 can be used as an operating power source for the power-consuming device 1 and also as a drive power source for the power-consuming device 1, replacing fuel or natural gas wholly or partially to provide the drive for the power-consuming device 1.

[0445] The power-consuming device 1 can further comprise a controller 3 and a motor 4, wherein the controller 3 is used to control the battery pack 2 to supply power to the motor 4, for example to meet the work power requirements of the power-consuming device 1 when starting, navigating and driving.

[0446] Another example of a power-consuming device could be a mobile phone, a tablet, a laptop, etc. The power-consuming device typically needs to be lightweight and thin, and a battery cell can be used as its power source.

[0447] The following charging methods are available for charging the power-consuming device: With a constant current of 5.0 C, charging from 10% SOC to 15% SOC is achieved. With a constant current of 5.0 C, charging from 15% SOC to 20% SOC is achieved. With a constant current of 5.0 C, charging from 20% SOC to 25% SOC is achieved. With a constant current of 5.0 C, charging from 25% SOC to 30% SOC is achieved. With a constant current of 5.0 C, charging from 30% SOC to 35% SOC is achieved. With a constant current of 5.0 C, charging from 35% SOC to 40% SOC is achieved. With a constant current of 4.6 C, charging from 40% SOC to 45% SOC is achieved. With a constant current of 4.3C, charging from 45% SOC to 50% SOC is achieved. With a constant current of 4.0 C, it charges from 50% SOC to 55% SOC. With a constant current of 3.7 C, charging from 55% SOC to 60% SOC is achieved. With a constant current of 3.4 C, charging takes place from 60% SOC to 65% SOC. With a constant current of 3.1 C, charging from 65% SOC to 70% SOC is achieved. With a constant current of 2.9 C, charging from 70% SOC to 75% SOC is achieved. With a constant current of 2.7 C, the battery is charged from 75% SOC to 80% SOC.

[0448] In some embodiments, the charging time of the power-consuming device from a state of charge of 10% to 80% is less than or equal to 10.5 minutes, optionally from 5 minutes to 10.5 minutes. The temperature of the external environment of battery pack 2 at a state of charge of 10% is room temperature, for example, 30 °C. For example, the charging time of battery pack 2 from a state of charge of 10% to 80% may be 10.5 minutes, 10 minutes, 9.5 minutes, 9 minutes, 8.5 minutes, 8 minutes, 7.5 minutes, 7 minutes, 6.5 minutes, 6 minutes, 5.5 minutes, 5 minutes, or a range consisting of any two of the above values. Example of implementation

[0449] The following exemplary embodiments describe in more detail the content disclosed in the embodiments of the present application. These exemplary embodiments serve only as an illustration, since various modifications and changes within the scope of the content disclosed in the embodiments of the present application are obvious to the person skilled in the art. Unless otherwise stated, all proportions, percentages, and ratios given in the following exemplary embodiments refer to mass. All reagents used in the exemplary embodiments are commercially available or are synthesized by conventional methods and can be used directly without further treatment. The instruments used in the exemplary embodiments are commercially available. Exemplary embodiment 1-1 (Stacked battery cell) 1. Production of the positive electrode sheet

[0450] The positive electrode sheet comprised a positive electrode current collector, a conductive layer of the positive electrode, and a positive electrode film layer on the positive electrode current collector, the positive electrode current collector being an aluminum foil.

[0451] The conductive layer of the positive electrode on the positive electrode current collector was a 1 µm thick film layer formed by uniformly mixing the positive electrode conductive medium of superconducting carbon, the positive electrode binder of polyvinylidene fluoride (PVDF), and the solvent of N-methyl-2-pyrrolidone (NMP), applying the mixture to the surface of the current collector, and drying, with the mass fraction of the positive electrode conductive medium in the conductive layer of the positive electrode being 40% and that of the positive electrode binder being 60%.8

[0452] The positive electrode film layer comprised a film layer formed by uniformly applying the positive electrode paste (solvent: N-methyl-2-pyrrolidone, NMP) to the surface of the conductive layer of the positive electrode, drying, and cold pressing. The positive electrode film layer comprised a positive electrode active material, a binder (polyvinylidene fluoride, PVDF), and a conductive agent (acetylene carbon black) in a weight ratio of 97:2:1.

[0453] The positive electrode active material comprised lithium iron phosphate and a coating layer, wherein the surface of the lithium iron phosphate was coated with the coating layer, and the coating layer comprised lithium iron titanium phosphate (Li₂FeTi(PO₄)₃) and amorphous carbon. The Dv₅₀ value of the positive electrode active material was 1.6 µm and the Dv₁₀ value was 0.64 µm.

[0454] The one-sided coating weight of the positive electrode film layer was 300 mg / 1540.25 mm². 2 . 2. Production of the negative electrode sheet

[0455] The negative electrode sheet comprised a negative electrode current collector, a conductive layer of the negative electrode, and a negative electrode film layer on the negative electrode current collector, the negative electrode current collector being a copper foil.

[0456] The conductive layer of the negative electrode on the negative electrode current collector was a 1 µm thick film layer formed by uniformly mixing the conductive agent of the negative electrode made of superconducting carbon, the binder of the negative electrode made of styrene-butadiene rubber (SBR), the thickening agent made of sodium carboxymethylcellulose (CMC-Na), and the solvent made of water, applying the mixture to the surface of the negative electrode current collector, and drying, wherein the mass fraction of the conductive agent of the negative electrode in the conductive layer of the negative electrode was 35%, the mass fraction of the binder of the negative electrode in the conductive layer of the negative electrode was 60%, and the mass fraction of the thickening agent in the conductive layer of the negative electrode was 5%.

[0457] The negative electrode film layer comprised a film layer formed by uniformly applying the negative electrode paste (solvent: deionized water) to the surface of the conductive layer of the negative electrode, followed by drying and cold pressing.

[0458] The one-sided coating weight of the negative electrode film layer was 138 mg / 1540.25 mm². 2 .

[0459] The negative electrode film layer comprised a first region and a second region, with the length ratio of the first region to the negative electrode film layer being 0.15.

[0460] The first section comprised a first sublayer and a second sublayer. The first sublayer was located on the surface of the conductive layer of the negative electrode, and the second sublayer was located on the surface of the first sublayer. After manufacturing, the compaction density of the first sublayer at 100% state of charge (SOC) of the battery cell was 1.35 g / cm³. 3 , and the compaction density of the second sublayer was 1.28 g / cm³ 3 .

[0461] The first sublayer comprised a negative electrode active material, a conductive medium made of acetylene carbon black, a lithium-containing binder (a copolymer of lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate, wherein the molar percentages of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer were 35%:30%:15%:20%), a negative electrode binder made of styrene-butadiene rubber, and a thickening agent made of sodium carboxymethylcellulose with a mass ratio of 96.5:0.5:2.5:0.3:0.2. The mass fraction of the element lithium in the lithium-containing binder was 9%. The negative electrode active material comprised artificial graphite and natural graphite, with the volume-averaged particle size Dv50 of the artificial graphite being 11.8 µm and the volume-averaged particle size Dv50 of the natural graphite being 12 µm.

[0462] The second sublayer comprised synthetic graphite, a conductive agent made of acetylene carbon black, a lithium-containing binder (a copolymer of lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate, wherein the molar percentages of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer were 35%:30%:15%:20%), a negative electrode binder made of styrene-butadiene rubber, and a thickening agent made of sodium carboxymethylcellulose with a mass ratio of 96.5:0.5:0.5:1.5:1. The mass fraction of elemental lithium in the first lithium-containing binder was 9%; the volume-averaged particle diameter Dv50 of the synthetic graphite was 11.8 µm; the mass fraction of the lithium-containing binder in the second sublayer was 0.50%.

[0463] The second area comprised a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer was located on the surface of the conductive layer of the negative electrode, and the second negative electrode film layer was located on the surface of the first negative electrode film layer. After manufacturing the battery cell, at 100% state of charge (SOC), the compaction density of the first negative electrode film layer was 1.28 g / cm³. 3 and the compaction density of the second negative electrode film layer is 1.28 g / cm³ 3 .

[0464] The first negative electrode film layer comprised graphite particles, a conductive agent made of acetylene carbon black, a first lithium-containing binder (a copolymer of lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate, wherein the molar percent of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer was 35%:30%:15%:20%), a negative electrode binder made of styrene-butadiene rubber and a thickening agent made of sodium carboxymethylcellulose with a mass ratio of 96.5:0.5:2.5:0.3:0.2. The mass fraction of the element lithium in the first lithium-containing binder was 9%, the Dv50 value of the graphite particles was 11.8 µm, the graphite particles comprised artificial graphite and a carbon coating layer, the surface of the artificial graphite was coated with the carbon coating layer, and the mass fraction of the carbon coating layer was 3.5%.

[0465] The second negative electrode film layer comprised graphite particles, a conductive agent made of acetylene carbon black, a second lithium-containing binder (a copolymer of lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate, wherein the molar percent of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer was 35%:30%:15%:20%), a negative electrode binder made of styrene-butadiene rubber and a thickening agent made of sodium carboxymethylcellulose with a mass ratio of 96.5:0.5:0.5:1.5:1. The mass fraction of the element lithium in the second lithium-containing binder was 9%, the Dv50 value of the graphite particles was 11.8 µm, the graphite particles comprised artificial graphite and a carbon coating layer, the surface of the artificial graphite was coated with the carbon coating layer, and the mass fraction of the carbon coating layer was 3.5%. 3. Separator

[0466] The separator comprised a base film, the base film being a 7 µm thick polyethylene film layer with a porosity of 42%. 4. Preparation of the electrolyte solution

[0467] The electrolyte solution comprised an organic solvent, a lithium salt, and an additive.

[0468] The organic solvent comprised 48.5% chain-like carboxylic acid ester solvent (ethyl acetate) and 32.5% carbonate solvent (24.5% ethylene carbonate EC, 8% dimethyl carbonate); the mass fraction of each component of the organic solvent was calculated based on the mass of the electrolyte solution.

[0469] Based on the mass of the electrolyte solution, the mass fraction of the additive was 6.5%, comprising vinylene carbonate VC, fluoroethylene carbonate FEC, ethylene sulfite ES and lithium difluoro(oxalato)borate LiDFOB in a mass ratio of 5:0.5:0.5:0.5.

[0470] The lithium salt comprised 1 mol / L lithium hexafluorophosphate LiPF6.

[0471] The conductivity of the electrolyte solution at room temperature was 16.4 mS / cm. 5. Manufacturing the battery cell

[0472] The positive electrode sheet, the separator, and the negative electrode sheet were stacked sequentially. The separator was positioned between the positive and negative electrode sheets to provide insulation, thus creating an electrode assembly through a stacking process. The electrode assembly was placed in an outer packaging sleeve. After drying, the electrolyte solution was injected, and a battery cell was obtained through vacuum sealing, settling, formation, and shaping, etc. The compaction density of the positive electrode film layer at 100% state of charge (SOC) of the battery cell was 2.72 g / cm³. 3 fraud. Comparative example 1-1, embodiment 1-2 to embodiment 1-11

[0473] The battery cell was manufactured using a similar process to that described in embodiment 1-1. The difference from embodiment 1-1 was that the composition of the first sublayer, etc., was adapted, as shown in Table 1. Performance tests: 1. Battery cell cycle count to 70% SOH

[0474] At room temperature, the battery cell is charged to the final charging voltage of 3.65 V with a constant current of 1 C and then discharged to 2.0 V with a constant current of 1 C – this constitutes one charge-discharge cycle. This charge-discharge cycle is repeated until the cyclic capacity retention rate (i.e., Cn / C0 × 100%) reaches 70%, and the number of cycles is recorded. The higher the number of cycles, the better the cycle performance of the battery cell.

[0475] The test results are shown in Table 1. Table 1 The dimensional ratio of the first region to the negative electrode film layer along the longitudinal direction The first area of ​​the negative electrode sheet Battery power First lower class Second lower class Lithium plating area at 500 cycles (in %) Cycle count at 70% SOH Compaction density (in g / cm³) 3 ) Negative electrode active material Mass fraction of lithium-containing binder Artificial graphite Artificial graphite Natural graphite mass fraction D v50 / µm mass fraction D v50 / µm mass fraction D v50 / µm Comparison example 1-1 0,15 1,28 50 % 11,8 / / 2,50 % 50 % 11,8 14,5 1500 Example 1-1 0,15 1,35 30 % 11,8 20 % 12 2,50 % 50% 11,8 1.0 3500 Example 1-2 0,15 1,29 45 % 11,8 5 % 12 2,50 % 50 % 11,8 11,0 3000 Example 1-3 0,15 1,41 5 % 11,8 45 % 12 2,50 % 50 % 11,8 2,0 2130 Exemplary embodiment 1-4 0,15 1,35 30 % 11,8 20% 8 2,50 % 50 % 11,8 6,0 2960 Example 1-5 0,15 1,35 30 % 11,8 20 % 15 2,50% 50 % 11,8 7,0 2800 Example 1-6 0,15 1,35 30 % 7,0 20 % 12 2,50 % 50 % 7,0 0,5 3450 Exemplary embodiment 1-7 0,15 1,35 30 % 11,8 20 % 12 0,10 % 50 % 11,8 3,0 3120 Example 1-8 0,15 1,35 30 % 11,8 20 % 12 3,00 % 50 % 11,8 1,0 3400 Example 1-9 0,20 1,35 30 % 11,8 20 % 12 2,50 % 50 % 11,8 1,0 3480 Example 1-10 0,05 1,35 30 % 11,8 20 % 12 2,50 % 50 % 11,8 13,5 2650 Example 1-11 0,15 1,35 30 % 11,8 30 % 12 2,50 % 40 % 11,8 0,9 3380

[0476] Table 1 shows the electrode tabs on both sides of the current collector along the longitudinal direction.

[0477] The compression density refers to the compression density of the battery cell at 100% SOC.

[0478] The mass fraction of artificial graphite and the mass fraction of natural graphite are calculated based on the mass of the negative electrode active material in the first area.

[0479] In comparative example 1-1, the first region does not include natural graphite, the lithium plating area of ​​the battery cell is larger, and cycle life degradation occurs. By designing the first region in the embodiments of the present application, the first sublayer in the first region comprises both synthetic and natural graphite, which improves the fast-charging performance of the first sublayer, reduces the lithium plating area, and increases cycle life. By appropriately increasing the mass fraction of natural graphite, for example, to 5% to 45%, optionally 20% to 45%, the compaction density increases with increasing mass fraction of natural graphite, and the risk of lithium plating degradation can be further reduced, and cycle life can be improved. However, further increasing the mass fraction of natural graphite worsens cycle life.

[0480] By appropriately adjusting the distribution content of artificial graphite in the first sublayer and the second sublayer, the risk of lithium plating can be further reduced and the cycle performance improved in the embodiments of the present application.

[0481] In the embodiments of the present application, the volume-averaged particle size Dv50 of natural graphite can be appropriately adjusted, for example, with a Dv50 of 12 µm and its specific surface area of ​​2.1 m². 2 / g, the cycle performance of the battery cell is improved and the risk of lithium plating is reduced. With a relatively small Dv50, for example 8 µm, the charge capacity of the natural graphite is enhanced, where the specific surface area is relatively large, for example 4.0 m². 2The specific surface area is lower (Dv50) per gram, and more side reactions occur, resulting in relatively poorer cycle performance. With a relatively large Dv50, for example 15 µm, the specific surface area is smaller, for example 1.85 m². 2 / g, the side reactions of natural graphite are lower, the cycle performance is optimized, but the charging performance is reduced. In the embodiments of the present application, by appropriately reducing the volume-averaged particle size Dv50 of the artificial graphite, for example to 7 µm to 15 µm, optionally to 7 µm to 12 µm, the solid-state transport path is shortened, which improves the fast-charging capability and reduces the risk of lithium plating. With a volume-averaged particle size of 11.8 µm for the artificial graphite, its specific surface area is 0.9 m². 2 / g; with a volume-averaged particle size of the artificial graphite of 7 µm, its specific surface area is 2.6 m². 2 / G.

[0482] The embodiments of the present application contribute to further reducing the risk of lithium plating and improving cycle performance by appropriately increasing the mass fraction of the lithium-containing binder.

[0483] In the embodiments of the present application, the length ratio of the first region to the negative electrode film layer is 0.05 to 0.20, optionally 0.10 to 0.20. With increasing dimensions of the first region, the risk of lithium plating decreases, but the cycle life may deteriorate due to the reduction in capacity. Example 2-1 (Winded battery cell)

[0484] The battery cell was manufactured using a similar process to that described in embodiment 1-). The difference from embodiment 1-1 was that the electrode arrangement was produced by a winding process to obtain the battery cell. The negative electrode film layer comprised a first region and a second region, with the length ratio of the first region to the negative electrode film layer being 0.08. Comparative example 2-1, embodiment 2-2 to embodiment 2-7

[0485] The battery cell was manufactured using a similar process to that described in embodiment 2-1. The difference compared to embodiment 2-1 was that the composition of the first sublayer, etc., was adapted, as shown in Table 2. Table 2 Negative electrode sheet Battery power First area Lithium plating area at 500 cycles (in %) Cycle count at 70% SOH First lower class Compaction density (in g / cm³) 3 ) Negative electrode active material Mass fraction of lithium-containing binder Mass fraction of artificial graphite Natural Graphite mass fraction D v50 / µm Comparative example 2-1 1,28 50 % 2,50 % 14,0 1640 Example 2-1 1,35 20 % 30 % 12 2,50 % 0,8 3640 Example 2-2 1,29 45 % 5 %. 12 2,50 % 10,5 2980 Example 2-3 1,41 5 % 45 % 12 2,50 % 1,8 2125 Example 2-4 1,35 20 % 30 % 8 2,50 % 5,6 2950 Example 2-5 1,35 20% 30 % 15 2,50 % 6,5 2750 Example 2-6 1,35 20 % 30 % 12 0,10 % 2,8 3105 Example 2-7 1,35 20% 30 % 12 3,00 % 0,9 3350

[0486] In Table 2, the electrode tab is located on one side of the current collector.

[0487] The compression density refers to the compression density of the battery cell at 100% SOC.

[0488] The mass fraction of artificial graphite and the mass fraction of natural graphite are calculated based on the mass of the negative electrode active material in the first area.

[0489] In comparative example 2-1, the first region does not include natural graphite, the lithium plating area of ​​the battery cell is larger, and cycle life degradation occurs. By designing the first region in the embodiments of the present application, the first sublayer in the first region comprises both synthetic and natural graphite, which improves the fast-charging performance of the first sublayer, reduces the lithium plating area, and increases cycle life. By appropriately increasing the mass fraction of natural graphite, for example, to 5% to 45%, optionally 20% to 45%, the compaction density increases with increasing mass fraction of natural graphite, and the risk of lithium plating can be further reduced, and cycle life can be improved. However, further increasing the mass fraction of natural graphite worsens cycle life.

[0490] The embodiments of the present application contribute to further reducing the risk of lithium plating and improving cycle performance by appropriately increasing the mass fraction of the lithium-containing binder.

[0491] Although illustrative embodiments have been demonstrated and described, the person skilled in the art should understand that the above embodiments should not be construed as limitations of the present application and that changes, replacements and modifications to the embodiments may be made without departing from the spirit, principles and scope of the present application. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] Test standard GB / T24533-2009 [0162, 0264] X-ray diffractometry JIS / K0131-1996

[0180] Reference to GB / T5162-2006

[0200] Test standard GB / T30835-2014

[0261] Test standard GB / T 19587-2017

[0294] Standard GB / T 36363-2018 “Polyolefin separators for battery cells

[0333] Industry standard HG-T 4067-2015

[0356] GB / T 10247-2008

[0359] Reference to GB / T 2013-2010

[0362] GB / T31486-2015

[0401]

Claims

[1] Battery cell comprising an electrode arrangement, wherein the electrode arrangement comprises: a positive electrode sheet comprising a positive electrode current collection section and a positive electrode film layer, wherein the positive electrode film layer is arranged on at least one side of the positive electrode current collection section along the thickness direction of the positive electrode current collection section, wherein the positive electrode film layer comprises a positive electrode active material, wherein the positive electrode active material comprises a lithium-containing phosphate with an olivine structure;and a negative electrode sheet comprising a negative electrode tab, a negative electrode current collection section and a negative electrode film layer, wherein the negative electrode film layer is arranged on at least one side of the negative electrode current collection section along the thickness direction, the negative electrode film layer contains a negative electrode active material, wherein the negative electrode tab is connected to at least one side of the negative electrode current collection section along a first direction; wherein the negative electrode film layer comprises two ends opposite each other along the first direction, wherein the negative electrode film layer comprises a first region and a second region, wherein the first region comprises one of the two ends facing the negative electrode tab, wherein the ratio of the dimension of the first region along the first direction to the dimension of the negative electrode film layer along the first direction is 0.05 to 0.20, the negative electrode active material of the first region comprises artificial graphite and natural graphite, wherein the first direction is perpendicular to the thickness direction. [2] Battery cell according to claim 1, wherein the mass fraction of natural graphite relative to the mass of the negative electrode active material in the first region is 5% to 45%. [3] Battery cell according to claim 1 or 2, wherein the mass fraction of natural graphite relative to the mass of the negative electrode active material in the first region is 20% to 45%. [4] Battery cell according to claim 1 or 2, wherein the mass fraction of the artificial graphite relative to the mass of the negative electrode active material in the first region is 55% to 95%. [5] Battery cell according to one of claims 1 to 4, wherein the first region comprises a first sublayer and a second sublayer, wherein the first sublayer is arranged on at least one side of the negative electrode current collection section, the second sublayer is arranged on a side of the first sublayer facing away from the negative electrode current collection section, the first sublayer comprises artificial graphite and natural graphite, and the second sublayer comprises artificial graphite. [6] Battery cell according to claim 5, wherein the mass fraction of the artificial graphite in the second sublayer is 30% to 70% in relation to the mass of the negative electrode active material in the first region. [7] Battery cell according to claim 5 or 6, wherein the density of the first sublayer is greater than or equal to the density of the second sublayer when the battery cell is at a charge level of 100%. [8] Battery cell according to one of claims 5 to 7, wherein the compression density of the first sublayer is 1.25 g / cm³ 3 up to 1.65 g / cm³ 3 is the case when the battery cell is at 100% charge; and / or the compaction density of the second sublayer is 1.1 g / cm³ 3 up to 1.5 g / cm³ 3 is the value when the battery cell is at 100% charge. [9] Battery cell according to any one of claims 5 to 8, wherein the first sublayer comprises a lithium-containing binder, wherein the mass fraction of the lithium-containing binder is 0.1% to 3% based on the mass of the first sublayer; and / or the second sublayer comprises a lithium-containing binder, wherein the mass fraction of the lithium-containing binder is 0.1% to 3% based on the mass of the second sublayer. [10] Battery cell according to claim 9, wherein the mass fraction of the element lithium in the lithium-containing binder is 4% to 10%. [11] Battery cell according to claim 9 or 10, wherein the lithium-containing binder comprises a copolymer of lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate, wherein the copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer, wherein the molar percent of the lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. [12] Battery cell according to any one of claims 1 to 11, wherein the volume-averaged particle size Dv50 of the artificial graphite in the first range is 7 µm to 15 µm; and / or the volume-averaged particle size Dv50 of the natural graphite in the first range is 7 µm to 15 µm. [13] Battery cell according to any one of claims 1 to 12, wherein the specific surface area of ​​the natural graphite in the first region is larger than the specific surface area of ​​the artificial graphite in the first region. [14] Battery cell according to one of claims 1 to 13, wherein the specific surface area of ​​the natural graphite in the first region is 1.5 m² 2 / g up to 4.5 m 2 / g; and / or the specific surface area of ​​the artificial graphite in the first area is 0.7 m² 2 / g up to 3.0 m 2 / g. [15] Battery cell according to any one of claims 1 to 14, wherein the ratio of the size of the first region along the first direction to the dimension of the negative electrode film layer along the first direction is 0.10 to 0.

20. [16] Battery cell according to any one of claims 1 to 15, wherein the electrode arrangement has a stacked structure, wherein the positive electrode sheet and the negative electrode sheet are stacked along the thickness direction. [17] Battery cell according to claim 16, wherein the negative electrode tabs are connected to both sides of the negative electrode current collection section along the first direction and the first region comprises two of the ends. [18] Battery cell according to claim 16, wherein the negative electrode tab is connected to a side of the negative electrode current collection section along the first direction and the first region is one of the two ends that faces the negative electrode tab. [19] Battery cell according to any one of claims 1 to 18, wherein the electrode arrangement has a wound structure, wherein the positive electrode sheet and the negative electrode sheet are wound in one direction. [20] Battery cell according to claim 19, wherein the negative electrode tab is connected to one side of the negative electrode current collection section along the first direction and the first region comprises two of the ends. [21] Battery cell according to any one of claims 1 to 20, wherein the lithium plating area of ​​the negative electrode film layer after 500 cycles of cyclic charging and discharging of the battery cell is 0% to 13.5% based on the surface area of ​​the negative electrode film layer. [22] Battery cell according to any one of claims 1 to 21, wherein the lithium plating area of ​​the negative electrode film layer is 0% to 6%. [23] Battery cell according to one of claims 1 to 22, wherein the positive electrode sheet further comprises an insulating layer, wherein the insulating layer is arranged on the positive electrode current collection section and is connected to the positive electrode film layer, and the insulating layer and the first region are arranged opposite each other along the thickness direction. [24] Battery cell according to any one of claims 1 to 23, wherein the negative electrode film layer further comprises a second region which is arranged continuously with the first region, wherein the second region comprises: a first negative electrode film layer arranged on the surface of the negative electrode current collecting section, wherein the first negative electrode film layer comprises a carbon-based material, and a second negative electrode film layer connected to the side of the first negative electrode film layer facing away from the negative electrode current collection section, wherein the second negative electrode film layer comprises a carbon-based material, wherein the carbon-based material in the first negative electrode film layer and the carbon-based material in the second negative electrode film layer each independently comprise graphite particles, and the volume-averaged particle size Dv50 of the graphite particles in the first negative electrode film layer is larger or equal to the volume-averaged particle size Dv50 of the graphite particles in the second negative electrode film layer, the graphite particles comprise artificial graphite and a carbon coating layer, wherein the artificial graphite comprises secondary particles and the surface of the artificial graphite is coated with the carbon coating layer. [25] Battery cell according to claim 24, wherein the graphitization level of the graphite particles is 92.0% to 94.5%. [26] Battery cell according to claim 24 or 25, wherein the mass fraction of the carbon coating layer, based on the mass of the graphite particles, is 2% to 5%. [27] Battery cell according to one of claims 24 to 26, wherein the powder compaction density of the graphite particles at 20000 N is 1.5 g / cm³ 3 up to 1.85 g / cm³ 3 amounts. [28] Battery cell according to one of claims 24 to 27, wherein the compaction density of the first negative electrode film layer is 1.15 g / cm³ 3 up to 1.36 g / cm³ 3is, when the battery cell is at 100% charge, and / or the compaction density of the second negative electrode film layer is 1.15 g / cm³ 3 up to 1.36 g / cm³ 3 is the value when the battery cell is at 100% charge. [29] Battery cell according to one of claims 24 to 28, wherein the volume-averaged particle size Dv50 of the graphite particles in the first negative electrode film layer is 9.5 µm to 18.5 µm, and / or the volume-averaged particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8 µm to 14.3 µm. [30] Battery cell according to one of claims 24 to 29, wherein the first negative electrode film layer further comprises a first lithium-containing binder and the second negative electrode film layer further comprises a second lithium-containing binder, wherein the mass fraction of the first lithium-containing binder, based on the mass of the first negative electrode film layer, is less than or equal to the mass fraction of the second lithium-containing binder, based on the mass of the second negative electrode film layer. [31] Battery cell according to claim 30, wherein the mass fraction of the first lithium-containing binder, based on the mass of the first negative electrode film layer, is 0.1% to 3%, and / or the mass fraction of the second lithium-containing binder, based on the mass of the second negative electrode film layer, is 0.1% to 3%. [32] Battery cell according to claim 30 or 31, wherein the mass fraction of the element lithium in the first lithium-containing binder is 3% to 10%, and / or the mass fraction of the element lithium in the second lithium-containing binder is 3% to 10%. [33] Battery cell according to one of claims 30 to 32, wherein The first lithium-containing binder comprises a copolymer of lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate, wherein the copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer, wherein the molar percentage of the lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 30% to 50%, 15% to 45%, 5% to 20%, and 20% to 35%, respectively. The second lithium-containing binder comprises a copolymer of lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate, wherein the copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer, wherein the molar percent of the lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. [34] Battery cell according to any one of claims 1 to 33, wherein the one-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm² 2 up to 170 mg / 1540.25 mm 2 amounts. [35] Battery cell according to one of claims 1 to 34, wherein the negative electrode sheet further comprises a conductive layer of the negative electrode, wherein the conductive layer of the negative electrode is located between the negative electrode film layer and the negative electrode current collection section. [36] Battery cell according to claim 35, wherein the thickness of the conductive layer of the negative electrode is 0.1 µm to 2 µm. [37] Battery cell according to claim 35 or 36, wherein the conductive layer of the negative electrode comprises a conductive means of the negative electrode, wherein the conductive means of the negative electrode comprises one or more of superconducting carbon, conductive graphite, acetylene carbon black, carbon black, Ketjen carbon black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, and / or the conductive layer of the negative electrode comprises a binder of the negative electrode, wherein the binder of the negative electrode comprises one or more of styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate and carboxymethyl chitosan. [38] Battery cell according to any one of claims 1 to 37, wherein The compaction density of the positive electrode film layer is 2.50 g / cm³. 3 up to 2.80 g / cm³ 3 is when the battery cell is at 100% charge, and / or The one-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm². 2 up to 370 mg / 1540.25 mm 2 amounts. [39] Battery cell according to any one of claims 1 to 38, wherein The compaction density of the positive electrode film layer is 2.55 g / cm³. 3 up to 2.70 g / cm³ 3 is when the battery cell is at 100% charge, and / or The one-sided coating weight of the positive electrode film layer is 240 mg / 1540.25 mm². 2 up to 330 mg / 1540.25 mm 2 amounts. [40] Battery cell according to any one of claims 1 to 39, wherein the powder compaction density of the positive electrode active material at 30000 N is 2.46 g / cm³. 3 up to 2.8 g / cm³ 3 amounts. [41] Battery cell according to any one of claims 1 to 40, wherein the lithium-containing phosphate with olivine structure comprises: Phosphate particles and a coating layer, wherein the coating layer coats the phosphate particles and the coating layer contains one or more of C, Fe, Ti, Zr, Hf, Ge and Sn. [42] Battery cell according to claim 41, wherein the phosphate particles are a compound with the general formula of Li x1 A y1 Me a M b P 1–c X c Y zincludes, where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3 and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5 and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A includes one or more of Na, K and Mg, Me includes one or more of Mn, Fe, Co and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La and Ce, X comprises one or more of S, Si, Cl, B, C and N, and Y comprises one or more of O and F. [43] Battery cell according to claim 41 or 42, wherein the coating layer is a fast ion conductor with the general formula of Li 3-d fe 2-d M2 d (PO x2 ) y2 includes, where M2 includes one or more of Ti, Zr, Hf, Ge and Sn, 0 ≤ d ≤ 1, 0 < x2 < 5, and 0 < y2 < 4. [44] Battery cell according to one of claims 41 to 43, wherein the graphitization degree of the lithium-containing phosphate with olivine structure is 0.15 to 0.

32. [45] Battery cell according to one of claims 41 to 44, wherein the mass fraction of the element carbon in the lithium-containing phosphate with olivine structure is 1% to 2%, and the specific surface area of ​​the lithium-containing phosphate with olivine structure is 5 m² 2 / g up to 18 m 2 / g. [46] Battery cell according to one of claims 41 to 45, wherein the specific surface area of ​​the lithium-containing phosphate with olivine structure is 7.5 m² 2 / g up to 14 m 2 / g. [47] Battery cell according to any one of claims 1 to 46, wherein the lithium-containing phosphate with olivine structure is in granular form and its volume distribution particle size meets the following conditions: 1 µm ≤ Dv50 ≤ 2 µm, 0.4 µm ≤ Dv10 ≤ 0.7 µm. [48] ​​Battery cell according to any one of claims 1 to 47, wherein the lithium-containing phosphate with olivine structure is in granular form, and the lithium-containing phosphate with olivine structure comprises secondary particles, wherein the secondary particles comprise a plurality of primary particles, wherein the average particle size of the primary particles is 200 nm to 500 nm. [49] Battery cell according to one of claims 1 to 48, wherein the positive electrode sheet further comprises a conductive layer of the positive electrode, wherein the conductive layer of the positive electrode is located between the positive electrode film layer and the positive electrode current collection section. [50] Battery cell according to claim 49, wherein the thickness of the conductive layer of the positive electrode is 0.1 µm to 2 µm. [51] Battery cell according to claim 49 or 50, wherein the conductive layer of the positive electrode comprises a conductive means of the positive electrode, wherein the conductive means of the positive electrode comprises one or more of superconducting carbon, conductive graphite, acetylene carbon black, carbon black, Ketjen carbon black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, and / or the conductive layer of the positive electrode comprises a binder of the positive electrode, wherein the binder of the positive electrode comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, terpolymer of vinylidene fluoride-tetrafluoroethylene-propylene, terpolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, copolymer of tetrafluoroethylene-hexafluoropropylene, polyacrylic acid and fluorine-containing acrylate resin. [52] Battery cell according to any one of claims 1 to 51, wherein the charging time of the charging process of the battery cell from the state of charge of 10% to 80% is 5 minutes to 10.5 minutes. [53] Battery device comprising several battery cells according to any one of claims 1 to 52. [54] Battery device according to claim 53, wherein the charging time of the charging process of the battery device from the state of charge of 10% to 80% is 5 minutes to 10.5 minutes. [55] Power-consuming device comprising a battery device according to claim 53 or 54.

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