Battery cell, battery device and electric device

Abstract

The present application provides a battery cell, a battery device and an electric device. The battery cell comprises an electrode assembly; the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator; the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer arranged on at least one side of the negative electrode current collector, the negative electrode active layer comprises a negative electrode material, and the negative electrode material comprises a carbon material; the positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer arranged on at least one side of the positive electrode current collector, the positive electrode active layer comprises a positive electrode material, and the positive electrode material comprises a lithium-containing phosphate-based positive electrode material and a nickel-containing lithium transition metal oxide; the mass content of the nickel-containing lithium transition metal oxide in the positive electrode active material is 5%-50%; the mass content of Ni in the nickel-containing lithium transition metal oxide is greater than or equal to 30%; and the powder resistivity of the positive electrode material at 12 MPa is 30 Ω·cm-5000 Ω·cm.

Description

Battery cell, battery device and electric device Cross-reference to related applications This application claims priority to Chinese Patent Application No. 202411088427.1, filed on August 8, 2024, entitled “Battery cell, battery device and electric device,” and Chinese Patent Application No. 202411135902.6, filed on August 19, 2024, entitled “Battery cell, battery device and electric device,” the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery cell, a battery device and an electric device. BACKGROUND

[0002] Phosphate-based batteries are widely used in electric vehicles as power batteries due to their low cost. The phosphate-based positive electrode material has a clear cost advantage over the ternary positive electrode material. However, the energy density of the phosphate-based positive electrode material is low, and thus it is necessary to improve the energy density of the battery system while maintaining the low cost advantage. SUMMARY

[0003] The present application provides a battery cell, a battery device and an electric device, which improve the energy density and discharge power of the phosphate-based battery device.

[0004] A first aspect of the present application provides a battery cell, the battery cell comprising an electrode assembly, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet, and a separator film between the positive electrode sheet and the negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode active layer disposed on at least one side of the negative electrode current collector, the negative electrode active layer comprising a negative electrode material, the negative electrode material comprising a carbon material; the positive electrode sheet comprising a positive electrode current collector and a positive electrode active layer disposed on at least one side of the positive electrode current collector, the positive electrode active layer comprising a positive electrode active material, the positive electrode active material comprising a lithium-containing phosphate-based positive electrode material and a nickel-containing lithium transition metal oxide, the mass content of the nickel-containing lithium transition metal oxide in the positive electrode active material being 5%-50%; the mass content of Ni in the nickel-containing lithium transition metal oxide being greater than or equal to 30%; and the powder resistivity of the positive electrode material in the positive electrode active layer under 12 MPa being 30 Ω·cm-5000 Ω·cm.

[0005] In order to maintain the low cost advantage of the phosphate-based positive electrode material, the lithium-containing phosphate-based positive electrode material and the nickel-containing lithium transition metal oxide are mixed, and the mass content of the nickel-containing lithium transition metal oxide is controlled to be in the range of 5%-50%, so that the battery monomer has good volume energy density and maintains the cost advantage. However, when the mass content of the nickel-containing lithium transition metal oxide is in the range of 5%-50%, the use of the nickel-containing lithium transition metal oxide can cause the powder resistivity of the positive electrode active material to increase, resulting in a loss of discharge power performance of the battery monomer. The application further controls the internal resistance of the battery monomer by controlling the powder resistivity of the positive electrode active material to be in the range of 30-5000 Ω·cm; further controls the Ni content in the nickel-containing lithium transition metal oxide to improve the energy density of the battery monomer, so as to obtain a battery monomer with high energy density and good discharge power performance, and at the same time, the temperature rise rate during the charging process of the battery monomer can be relieved to a certain extent. Moreover, the battery monomer of the application also has the advantages of good thermal stability, high safety, long service life and low cost of the lithium-containing phosphate-based positive electrode material.

[0006] In any embodiment of the first aspect of the application, the mass content of the lithium-containing phosphate-based positive electrode material in the above positive electrode material is 50%-95%, which can be 50%-70%.

[0007] In any embodiment of the first aspect of the application, based on the total molar amount of transition metal elements in the nickel-containing lithium transition metal oxide, the molar content of Ni in the nickel-containing lithium transition metal oxide is 75%-95%.

[0008] In any embodiment of the first aspect of the application, the powder resistivity of the above positive electrode material under 12 MPa is 30 Ω·cm-2000 Ω·cm.

[0009] In any embodiment of the first aspect of the application, the powder resistivity of the above positive electrode material under 12 MPa is 30 Ω·cm-1500 Ω·cm.

[0010] In any embodiment of the first aspect of the application, the powder resistivity of the above positive electrode material under 12 MPa is 80 Ω·cm-1500 Ω·cm.

[0011] In any embodiment of the first aspect of the application, the powder resistivity of the above positive electrode material under 12 MPa is 30 Ω·cm-400 Ω·cm.

[0012] In any embodiment of the first aspect of the application, the powder resistivity of the above nickel-containing lithium transition metal oxide under 12 MPa is 100 Ω·cm-10000 Ω·cm, which can be 100 Ω·cm-5000 Ω·cm, and further can be 100-4000 Ω·cm.

[0013] In any embodiment of the first aspect of the application, the powder resistivity of the above-mentioned phosphate-based positive electrode material is 4-80 Ω·cm at 12 MPa.

[0014] In any embodiment of the first aspect of the application, the mass content of the element Ni is 1.7%-26.5%, optionally 10%-23.5%, based on the total mass of the positive electrode material.

[0015] In any embodiment of the first aspect of the application, the lithium-containing phosphate-based positive electrode material comprises a lithium iron manganese phosphate material, and the mass content of the element Fe is 4.5%-17%, optionally 4.5%-10.3%, based on the total mass of the positive electrode material.

[0016] In any embodiment of the first aspect of the application, the lithium-containing phosphate-based positive electrode material comprises a lithium iron manganese phosphate material, and the mass content of the element Mn is 3.4%-22.5%, based on the total mass of the positive electrode material.

[0017] In any embodiment of the first aspect of the application, the areal density of the above-mentioned positive electrode active layer is 200 mg / 1540.25 mm 2 -370 mg / 1540.25 mm 2 , optionally 240 mg / 1540.25 mm 2 -340 mg / 1540.25 mm 2 .

[0018] In any embodiment of the first aspect of the application, the powder compaction density of the positive electrode material is 2.5 g / cm 3 -2.8 g / cm 3 .

[0019] In any embodiment of the first aspect of the application, the above-mentioned lithium-containing phosphate-based positive electrode material comprises a lithium iron phosphate material, and the compaction density of the positive electrode active layer corresponding to the battery monomer when the battery monomer is configured to be in a 100% SOC state is 2.55 g / cm 3 -3.00 g / cm 3 .

[0020] In any embodiment of the first aspect of the application, the above-mentioned lithium-containing phosphate-based positive electrode material comprises a lithium iron manganese phosphate material, and the compaction density of the positive electrode active layer corresponding to the battery monomer when the battery monomer is configured to be in a 100% SOC state is 2.4 g / cm 3 -2.90 g / cm 3 .

[0021] In any embodiment of the first aspect of the application, the BET specific surface area of the positive electrode material is 7 m 2 / g-18m 2 / g.

[0022] In any embodiment of the first aspect of the application, the above-mentioned nickel-containing lithium transition metal oxide includes one or more of a lithium-containing nickel-cobalt-manganese oxide material, a lithium-containing nickel-cobalt-aluminum oxide material.

[0023] In any embodiment of the first aspect of the application, the above-mentioned nickel-containing lithium transition metal oxide includes a lithium-containing nickel-cobalt-manganese oxide material, and the lithium-containing nickel-cobalt-manganese oxide material contains at least one of Zr, Al, B, Fe, Ca, Sr, Ti, V, Y elements.

[0024] In any embodiment of the first aspect of the application, in the lithium-containing nickel-cobalt-manganese oxide material, one or more of Zr, Al, B, Fe elements are included, and one or more of the following characteristics are satisfied based on the lithium-containing nickel-cobalt-manganese oxide material: 1) the mass content of Zr is 1000-3000 ppm; 2) the mass content of Al is 100-1000 ppm; 3) the mass content of B is 20-300 ppm.

[0025] In any embodiment of the first aspect of the application, the above-mentioned lithium-containing phosphate-based positive electrode material includes a lithium-iron-manganese phosphate material, and the lithium-iron-manganese phosphate material contains one or more of Al, B, Ca, Cr, Cu, K, Mg, Na, P, Si, Ti, V, Zn elements.

[0026] In any embodiment of the first aspect of the application, the lithium-iron-manganese phosphate material includes one or more of Al, Ca, Na, Ti, V elements, and one or more of the following characteristics are satisfied based on the lithium-iron-manganese phosphate material: 1) the mass content of Al is 100-1000 ppm; 2) the mass content of Ca is 50-300 ppm; 3) the mass content of Na is 50-600 ppm; 4) the mass content of Ti is 100-1000 ppm; 6) the mass content of V is 1000-3000 ppm.

[0027] In any embodiment of the first aspect of the application, the above-mentioned positive electrode material contains a lithium-iron-manganese phosphate material and a nickel-cobalt-manganese oxide material, and the positive electrode material contains one or more of Al, Ca, Na, Ti, V, Zr, B elements, and the respective mass contents satisfy: Al: 0.005%-0.1%; Ca: 0.0001%-0.02%; Na: 0.005%-0.06%; Ti: 0.005%-0.15%; V: 0.0001%-0.3%; Zr: 0.005%-0.2%; B: 0.01%-0.1%.

[0028] In any implementation form of the first aspect of the application, the lithium-containing phosphate-based positive electrode material comprises a lithium iron manganese phosphate material, and a molar ratio of Mn to Fe in the lithium iron manganese phosphate material is 2:8-8:2, and is optionally 5:5-7:3.

[0029] In any implementation form of the first aspect of the application, the lithium-containing phosphate-based positive electrode material comprises a carbon-containing coating layer, and a mass content of carbon in the lithium-containing phosphate-based positive electrode material is 1%-3%.

[0030] In any implementation form of the first aspect of the application, a surface of the lithium-containing phosphate-based positive electrode material comprises an ion-conducting material, and the ion-conducting material comprises one or more of C element, Ti element, Zr element, Hf element, Ge element or Sn element.

[0031] In any implementation form of the first aspect of the application, in the positive electrode active material, a mass content of Fe element in particles with a particle size less than or equal to Dv10 is M1, a mass content of Fe element in particles with a particle size greater than or equal to Dv90 is M2, and M1 is greater than M2; and / or a mass content of Ni element in particles with a particle size less than or equal to Dv10 is M3, a mass content of Ni element in particles with a particle size greater than or equal to Dv90 is M4, and M3 is less than M4.

[0032] In any implementation form of the first aspect of the application, the positive electrode active material has one or more of the following characteristics: 1) the particles of the lithium transition metal oxide containing nickel are polycrystalline particles in a spherical or spheroidal shape, or the particles of the lithium transition metal oxide containing nickel are single-crystal particles; optionally, a volume particle size Dv50 of the single-crystal particles of the lithium transition metal oxide containing nickel is 1.5 μm-4.5 μm; optionally, a volume particle size Dv50 of the polycrystalline particles of the lithium transition metal oxide containing nickel is 7 μm-12 μm; 2) the particles of the lithium-containing phosphate-based positive electrode material are single-crystal particles.

[0033] In any implementation form of the first aspect of the application, the positive electrode tab further comprises a conductive layer, and the conductive layer is arranged between the positive electrode current collector and the positive electrode active layer.

[0034] In any implementation form of the first aspect of the application, the conductive layer comprises a binder and a conductive material, and a thickness of the conductive layer is 0.5 μm-2 μm.

[0035] In any implementation form of the first aspect of the application, a thickness of the positive electrode current collector is 9 μm-17 μm, and is preferably 10 μm-13 μm.

[0036] In any implementation form of the first aspect of the application, an area density of the negative electrode active layer is 90 mg / 1540.25 mm 2- 170 mg / 1540.25 mm 2 ; optionally 110 mg / 1540.25 mm 2 - 160 mg / 1540.25 mm 2 .

[0037] In any implementation of the first aspect of the application, the lithium-containing phosphate-based positive electrode material comprises a lithium iron phosphate material, and the battery cell is configured such that the corresponding negative electrode film layer has a compaction density of 1.04 g / cm3 3 - 1.48 g / cm3 3 ; optionally 1.23 g / cm3 3 - 1.42 g / cm3 3 .

[0038] In any implementation of the first aspect of the application, the negative electrode tab further comprises a negative electrode conductive layer, the negative electrode conductive layer being disposed between the negative electrode current collector and the negative electrode active layer, the negative electrode conductive layer having a thickness of 0.5 μm to 3 μm, optionally 1 μm to 2 μm.

[0039] In any implementation of the first aspect of the application, the negative electrode current collector has a thickness of 4 μm to 7 μm, optionally 4 μm to 5 μm.

[0040] In any implementation of the first aspect of the application, the carbon material comprises composite graphite particles, the composite graphite particles comprising: a body particle, the body particle comprising primary particles and / or secondary particles, the body particle comprising artificial graphite; and a coating layer, the coating layer being coated on a surface of the body particle, the coating layer comprising amorphous carbon.

[0041] In any implementation of the first aspect of the application, the mass content of the amorphous carbon in the coating layer is 2% to 5% based on the total mass of the composite graphite particles.

[0042] In any implementation of the first aspect of the application, the negative electrode active layer comprises: a first negative electrode active layer disposed on one side of the negative electrode current collector, the negative electrode material of the first negative electrode active layer comprising one or more of the composite graphite particles and the natural graphite, the volume average particle size Dv50 of the negative electrode material in the first negative electrode active layer being 7.5 μm to 19.5 μm, optionally 12.5 μm to 18.5 μm, and a second negative electrode active layer disposed on a side of the first negative electrode active layer away from the negative electrode current collector, the negative electrode material of the second negative electrode active layer comprising the composite graphite particles, the volume average particle size Dv50 of the negative electrode material in the second negative electrode active layer being 7.5 μm to 19.5 μm, optionally 7.5 μm to 15.5 μm.

[0043] In any implementation form of the first aspect of the application, the powder compaction density of the composite graphite particles under a pressure of 20000 N is 1.5 g / cm 3 - 1.85 g / cm 3 , optionally 1.55 g / cm 3 - 1.75 g / cm 3 .

[0044] In any implementation form of the first aspect of the application, the battery cell further comprises an electrolyte, and the conductivity of the electrolyte is 10-20 mS / cm or 12-17 mS / cm.

[0045] In any implementation form of the first aspect of the application, the electrolyte comprises lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonylimide (LiFSI).

[0046] In any implementation form of the first aspect of the application, the molar concentration ratio of the lithium bisfluorosulfonylimide and the lithium hexafluorophosphate is (2-5):10.

[0047] In any implementation form of the first aspect of the application, the battery cell comprises a shell, the electrode assembly is arranged in the shell, the positive electrode plate and the negative electrode plate are arranged in a laminated manner, the length of the shell is L1, the length of the positive electrode plate is L2, and L2 / L1 is 80%-99%, preferably L2 / L1 is 88%-99%.

[0048] In any implementation form of the first aspect of the application, the size of the shell has one or more of the following characteristics: the range of L1 is 300-950 mm; the height of the shell is 85-140 mm; the thickness of the shell is 10-20 mm.

[0049] In any implementation form of the first aspect of the application, the shell is an aluminum alloy shell, an alloy steel shell, or a titanium alloy shell.

[0050] In any implementation form of the first aspect of the application, the injection coefficient of the battery cell is 1.9 g / Ah-3.1 g / Ah, optionally 2.4 g / Ah-3.0 g / Ah.

[0051] In any implementation form of the first aspect of the application, the volumetric energy density of the battery cell is greater than or equal to 400 Wh / L, optionally 400-650 Wh / L, and optionally 500-600 Wh / L.

[0052] The second aspect of the application provides a battery device comprising the battery cell provided by any implementation form of the first aspect, and the battery device comprises a battery module, a battery pack, or an energy storage device.

[0053] The second aspect of the present application provides a power consuming device comprising the battery cell of any embodiment of the first aspect or the battery device of any embodiment of the second aspect. BRIEF DESCRIPTION OF DRAWINGS

[0054] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by the drawings without creative labor for those skilled in the art.

[0055] FIG. 1 is a schematic diagram of a battery assembly according to an embodiment of the present application.

[0056] FIG. 2 is an exploded view of a battery cell according to an embodiment of the present application.

[0057] FIG. 3 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0058] FIG. 4 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 3.

[0059] FIG. 5 is a schematic diagram of a power consuming device using the battery pack according to an embodiment of the present application as a power source.

[0060] In the drawings, the drawings are not drawn according to the actual scale.

[0061] Explanation of reference numerals:

[0062] 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 battery cell; 51 case; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0063] The embodiments of the present application will be described in further detail below with reference to the drawings and examples. The detailed description of the following examples and the drawings are used to exemplarily illustrate the principles of the present application, but cannot be used to limit the scope of the present application, i.e., the present application is not limited to the described examples.

[0064] Hereinafter, the embodiments of the battery cell, the battery device, and the power consuming device of the present application are specifically disclosed with appropriate reference to the drawings. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of matters known well, repeated descriptions of substantially the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0065] The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges can be "closed" ranges, i.e., the upper and lower limits of the range are included. The ranges can be arbitrarily combined, i.e., any upper limit can be combined with any lower limit to form a range. For example, if a range of 60-120 and a range of 80-110 are listed, it is understood that a range of 60-110 and a range of 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 are listed, and if a maximum range value of 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise indicated, a numerical range "a-b" means a range of any combination of the numbers a and b, wherein a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shorthand for listing all of those numbers. Also, when a parameter is stated to be an integer > 2, it is equivalent to disclose that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0066] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0067] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0068] All steps of the present application can be performed in sequence or randomly, preferably in sequence, unless otherwise specified. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can further comprise step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0069] The "includes" and "contains" mentioned in the present application are open-ended, unless otherwise specified. For example, the "includes" and "contains" can mean that other components not listed can also be included or contained.

[0070] If not specifically stated, the term "or" in this application is inclusive. For example, any of the following conditions satisfy the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or A and B are both true (or exist).

[0071] [Battery cell]

[0072] The application provides a battery cell, the battery cell comprising an electrode assembly, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet, and a separator film between the positive electrode sheet and the negative electrode sheet, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer arranged on at least one side of the negative electrode current collector, the negative electrode active layer comprising a negative electrode material, the negative electrode material comprising a carbon material; the positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer arranged on at least one side of the positive electrode current collector, the positive electrode material in the positive electrode active layer comprising a positive electrode material, the positive electrode material comprising a lithium-containing phosphate-based positive electrode material and a nickel-containing lithium transition metal oxide, the mass content of the nickel-containing lithium transition metal oxide in the positive electrode material being 5%-50%; the mass content of Ni in the nickel-containing lithium transition metal oxide being greater than or equal to 30%; and the powder resistivity of the positive electrode material under 12 MPa being 30 Ω·cm-5000 Ω·cm.

[0073] During the charging and discharging process of the battery cell, lithium ions are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The separator film is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent short circuiting of the positive and negative electrodes, and at the same time to allow the lithium ions to pass through.

[0074] In order to maintain the low-cost advantage of the phosphate-based positive electrode material, the application mixes the lithium-containing phosphate-based positive electrode material and the nickel-containing lithium transition metal oxide, and maintains the mass content of the nickel-containing lithium transition metal oxide in the range of 5%-50%, so that the battery cell has good volume energy density and maintains the cost advantage. However, when the mass content of the nickel-containing lithium transition metal oxide is in the range of 5%-50%, the use of the nickel-containing lithium transition metal oxide will cause the powder resistivity of the positive electrode active material to increase, resulting in a loss of the discharge power performance of the battery cell. The application further controls the powder resistivity of the positive electrode material in the range of 30-5000 Ω·cm to control the internal resistance of the battery cell and improve the discharge power performance of the battery cell; further controls the Ni content in the nickel-containing lithium transition metal oxide to improve the energy density of the battery cell, so as to obtain a battery cell with high energy density and good discharge power performance, and at the same time, to a certain extent, to alleviate the temperature rise rate during the charging process of the battery cell. Moreover, the battery cell of the application also has the advantages of good thermal stability, high safety, long service life, and low cost of the lithium-containing phosphate-based positive electrode material.

[0075] In some embodiments, the relative content of the lithium-containing phosphate-based cathode material and the nickel-containing lithium transition metal oxide in the cathode material can be jointly determined by methods including but not limited to SEM-EDS or TEM-EDS, XRD, ICP-OES, etc.

[0076] In some embodiments, the powder resistivity of the cathode material can be tested using a powder resistance tester, in the following manner:

[0077] For the cathode tab of the battery cell, the cathode tab is thoroughly cleaned with DMC (dimethyl carbonate), and the cathode tab is dried and calcined to collect the cathode material in the cathode active layer. The powder resistance tester is turned on and allowed to stabilize, a certain amount of cathode material is weighed and added to the feeding cavity and the feeding cavity depth is adjusted, the target pressure is applied according to the target pressure and the cavity area in the feeding cavity, and the powder resistivity test result at 12 MPa pressure is collected.

[0078] In some embodiments, the mass content of the lithium-containing phosphate-based cathode material in the above-mentioned cathode material is 50%-95%, and can be selected as 50%-70%. When the cathode material has the lithium-containing phosphate-based cathode material with the above-mentioned mass content, the advantages of the phosphate-based cathode material are fully played, and on the basis of reducing the battery internal resistance as much as possible, the volumetric energy density of the battery cell is improved.

[0079] With the increase of the content of Ni element, the gram capacity of the nickel-containing lithium transition metal oxide increases, and in some embodiments, based on the total molar amount of transition metal elements in the nickel-containing lithium transition metal oxide, the molar content of Ni in the nickel-containing lithium transition metal oxide is 50%-95%, which can be selected as 70%-95%, and further selected as 75%-95%. The use of the nickel-containing lithium transition metal oxide with high nickel content can further improve the gram capacity of the cathode active material, and further improve the energy density of the battery cell.

[0080] In some embodiments, the powder resistivity of the above-mentioned cathode material at 12 MPa is 30 Ω·cm-2000 Ω·cm.

[0081] In some embodiments, the powder resistivity of the above-mentioned cathode material at 12 MPa is 30 Ω·cm-1500 Ω·cm.

[0082] In some embodiments, the powder resistivity of the above-mentioned cathode material at 12 MPa is 80 Ω·cm-1500 Ω·cm, which can be selected as 140 Ω·cm-650 Ω·cm.

[0083] In some embodiments, the powder resistivity of the above-mentioned cathode material at 12 MPa is 30 Ω·cm-400 Ω·cm, which can be selected as 30 Ω·cm-120 Ω·cm.

[0084] The powder resistivity of the above is affected by the nickel content of the nickel-containing lithium transition metal oxide, the particle morphology, the mixing ratio of the lithium-containing phosphate-based positive electrode material and the nickel-containing lithium transition metal oxide, and other factors. For example, in the mixed system of the lithium-containing phosphate-based positive electrode material and the nickel-containing lithium transition metal oxide, when the content of the lithium-containing phosphate-based positive electrode material is in the range of 50% to 95%, and other influencing conditions are basically the same, as the nickel content of the nickel-containing lithium transition metal oxide increases, the powder resistivity of the nickel-containing lithium transition metal oxide decreases, and the powder resistivity of the mixed positive electrode material changes accordingly. For example, in other influencing conditions are basically the same, the same nickel-containing lithium transition metal oxide, when the nickel-containing lithium transition metal oxide is selected as a single crystal particle, the powder resistivity of the positive electrode material is higher, and as the single crystal particle grows, the powder resistivity increases, so that the powder resistivity of the positive electrode material can be 80 Ω·cm-1500 Ω·cm by selecting the single crystal form of the nickel-containing lithium transition metal oxide, but the cycle stability of the single crystal particle is better, so it is more conducive to improving the cycle performance of the battery cell; when the nickel-containing lithium transition metal oxide is selected as a polycrystalline particle, the powder resistivity of the positive electrode material can be reduced, and the powder resistivity of the positive electrode material can be 30 Ω·cm-400 Ω·cm by selecting the polycrystalline form of the nickel-containing lithium transition metal oxide, so it is more conducive to improving the discharge power of the battery cell.

[0085] In some embodiments, the powder resistivity of the nickel-containing lithium transition metal oxide at 12 MPa is 100 Ω·cm-10000 Ω·cm, which can be 100 Ω·cm-5000 Ω·cm, further 100-4000 Ω·cm, optionally 800 Ω·cm-4000 Ω·cm, optionally 800 Ω·cm-3000 Ω·cm (when the particle of the nickel-containing lithium transition metal oxide is a single crystal particle) or 100 Ω·cm-300 Ω·cm (when the particle of the nickel-containing lithium transition metal oxide is a spherical or spherical-like polycrystalline particle), further 800 Ω·cm-1800 Ω·cm (when the particle of the nickel-containing lithium transition metal oxide is a single crystal particle) or 130 Ω·cm-250 Ω·cm (when the particle of the nickel-containing lithium transition metal oxide is a spherical or spherical-like polycrystalline particle).

[0086] In some embodiments, the powder resistivity of the phosphate-based positive electrode material at 12 MPa is 4-80 Ω·cm, which can be 14 Ω·cm-45 Ω·cm.

[0087] In some embodiments, the mass content of the element Ni is 1.7%-26.5%, optionally 10%-23.5%, further optionally 14%-23.3% or 14%-19% based on the total mass of the positive electrode material. The element Ni in the positive electrode material mainly comes from the lithium transition metal oxide containing Ni, and thus the mass content of the element Ni to some extent characterizes the content of the lithium transition metal oxide containing Ni in the positive electrode material. When the content of Ni is within the above range, the specific capacity of the positive electrode material can be further improved, and thus the volumetric energy density of the battery cell can be further improved.

[0088] The element Fe in the positive electrode active layer mainly comes from the lithium-containing phosphate-based positive electrode material. In some embodiments, the lithium-containing phosphate-based positive electrode material includes a lithium iron manganese phosphate material, and the mass content of the element Fe is 4.5%-17%, optionally 4.5%-10.3%, further optionally 8%-10.3% based on the total mass of the positive electrode material. When the content of the element Fe is within the above range, the cycle stability and energy density of the battery cell can be more fully improved, and the cost can be more effectively controlled.

[0089] In some embodiments, the lithium-containing phosphate-based positive electrode material includes a lithium iron manganese phosphate material, and the mass content of the element Mn is 3.4%-22.5%, further optionally 12%-17% based on the total mass of the positive electrode material. The content of the element Mn can be adjusted by adjusting the content of the element Mn in the lithium transition metal oxide containing Ni, the content of the element Mn in the lithium-containing phosphate-based positive electrode material, and the proportion of the two materials. When the content of the element Mn is within the above range, the lithium transition metal oxide containing Ni in the battery cell has a higher specific capacity, and the lithium-containing phosphate-based positive electrode material has a higher platform voltage and cycle stability, and thus both the energy density and the cycle performance of the battery cell can be further improved as much as possible.

[0090] The elements in the above materials can be determined by the following method:

[0091] For the positive electrode tab of the battery cell, the positive electrode tab is sufficiently cleaned by DMC (dimethyl carbonate), and the positive electrode tab is dried and calcined to collect the positive electrode material in the positive electrode active layer. The positive electrode material is tested by inductively coupled plasma atomic emission spectrometry (ICP-OES).

[0092] In order to further improve the energy density of the battery cell through the active layer structure, in some embodiments, the area density of the positive electrode active layer is 200 mg / 1540.25 mm 2 -370 mg / 1540.25 mm 2 , optionally 240 mg / 1540.25 mm 2 -340 mg / 1540.25 mm2 .

[0093] The aforementioned areal density is tested by the following method:

[0094] Take a single-side coated positive electrode sheet (if it is a double-side coated electrode sheet, the positive electrode film on one side can be wiped off first), cut it into a small round piece with an area of S1, weigh it, and record it as M1, and measure its thickness H1. Then wipe off the positive electrode active layer of the aforementioned weighed positive electrode sheet, weigh the positive current collector, and record it as M0, and measure its thickness H0. The single-side coating weight of the positive electrode active layer (i.e., the areal density) = (the weight of the positive electrode sheet M1 - the weight of the positive current collector M0) / S1.

[0095] In some embodiments, if a positive electrode conductive layer is provided between the positive electrode active layer and the positive current collector, the mass of the positive electrode conductive layer can be ignored when testing the compaction density or areal density of the positive electrode active layer, because the mass of the positive electrode conductive layer is significantly lower than that of the positive electrode active layer. The same applies to the negative electrode active layer compaction density or areal density test.

[0096] In some embodiments, the powder compaction density of the positive electrode material under 30000N is 2.5g / cm 3 -2.8g / cm 3 To provide a material basis for achieving the largest possible active layer compaction density.

[0097] For the positive electrode sheet of the battery cell, the positive electrode sheet is thoroughly cleaned with DMC (dimethyl carbonate), and the positive electrode material in the positive electrode active layer is collected after the positive electrode sheet is dried and calcined. The powder compaction density of the positive electrode material under 30000N is tested.

[0098] The compaction density of the positive electrode active layer affects the stability of the electrolyte infiltration and volume expansion in the positive electrode sheet, and also affects the volume energy density of the battery cell. Generally, the larger the compaction density, the smaller the pores between the positive electrode active material particles, the worse the electrolyte infiltration, and the smaller the buffer space reserved for the expansion of the positive electrode active material, thus affecting the charging performance and cycle performance of the battery cell, but the volume energy density of the battery cell can be improved. The smaller the compaction density, the larger the pores between the positive electrode active material particles, the better the electrolyte infiltration, and the larger the buffer space reserved for the expansion of the positive electrode material, thus improving the charging performance and cycle performance of the battery cell, but leading to a decrease in the volume energy density of the battery cell.

[0099] In some embodiments, the lithium-containing phosphate-based positive electrode material includes a lithium iron phosphate material, and the battery cell is configured to have a compaction density of the positive electrode active layer corresponding to 2.55g / cm 3 -3.00g / cm 3In some embodiments, the lithium-containing phosphate-based positive electrode material includes a lithium-iron-manganese-phosphate material, and the battery cell is configured such that the compaction density of the positive electrode active layer corresponding to the battery cell when in a 100% SOC state is 2.40 g / cm 3 -2.90 g / cm 3 .

[0100] The above-mentioned "100% SOC state" refers to a state after the battery cell is charged to a voltage of 4.2 V at 25°C at a rate of 0.33C, and then charged at a constant voltage until the current is less than 0.05C.

[0101] The test method for the compaction density of the positive electrode active layer can be implemented according to the following method:

[0102] Based on the above-mentioned surface density test, the thickness of the positive electrode active layer is obtained as the thickness of the positive electrode sheet H1 minus the thickness of the positive electrode current collector H0, and the compaction density of the positive electrode active layer is obtained as the single-sided coating weight of the positive electrode active layer divided by the single-sided thickness of the positive electrode active layer.

[0103] In some embodiments, the BET specific surface area of the positive electrode material is 7 m 2 / g-18 m 2 / g. Controlling the BET specific surface area is beneficial for improving the comprehensive indicators of the cycle performance, energy density, and internal resistance of the battery cell.

[0104] The specific surface area is a meaning known in the art, and can be tested using methods known in the art. For example, for the positive electrode sheet of the battery cell, the positive electrode sheet is thoroughly cleaned using DMC (dimethyl carbonate), and the positive electrode sheet is dried and calcined to collect the positive electrode material in the positive electrode active layer. The positive electrode material can be tested using the nitrogen adsorption specific surface area analysis test method according to GB / T 19587-2017, and the BET (Brunauer Emmett Teller) method is used for calculation, wherein the nitrogen adsorption specific surface area analysis test can be performed using a Tri-Star 3020 specific surface area pore size analyzer from the American Micromeritics company.

[0105] The nickel-containing lithium transition metal oxide used in the present application can be selected from conventional positive electrode active materials of this type, such as nickel-containing lithium transition metal oxides including one or more of lithium-containing nickel-cobalt-manganese oxide materials and lithium-containing nickel-cobalt-aluminum oxide materials.

[0106] In some embodiments, the nickel-containing lithium transition metal oxide includes a lithium-containing nickel cobalt manganese oxide material containing at least one of Zr, Al, B, Fe, Ca, Sr, Ti, V, Y elements; optionally including one or more of Zr, Al, B, Fe elements. The elements in the above-mentioned material can exist in the nickel-containing lithium transition metal oxide in the form of doping or coating.

[0107] Doping Al, B, Ti, Y, Zr, Sr, etc. in the nickel-containing lithium transition metal oxide can significantly improve its electrochemical performance, structural stability and cycle performance. For example:

[0108] The Al element can form an AlO6 octahedron in the nickel-containing lithium transition metal oxide, which has a structure similar to the TMO6 octahedron (TM is a transition metal such as Ni, Co or Mn) and does not cause significant lattice distortion. The ionic radius of Al(III) is close to that of TM, so it is easy to be doped into the TM layer of the nickel-containing lithium transition metal oxide. Al doping helps to improve the chemical stability of the nickel-containing lithium transition metal oxide, reduce cation mixing, and improve its cycle performance.

[0109] B tends to exist on the surface in the nickel-containing lithium transition metal oxide because B has lower energy on the surface than in the bulk phase. The surface enrichment of B helps to stabilize the surface structure of the nickel-containing lithium transition metal oxide, reduces surface reconstruction, and thus improves the cycle stability of the material.

[0110] Ti doping can significantly improve the particle strength of the nickel-containing lithium transition metal oxide and enhance the cycle performance. After Ti replaces the transition metal element, the strong Ti-O bond formed helps to stabilize the lattice structure and prevent adverse changes in the structure during charging and discharging. In addition, Ti doping can also widen the Li ion insertion / extraction channel and improve the transmission rate of Li ions.

[0111] Y doping is beneficial to improving the cycle stability and rate performance of the nickel-containing lithium transition metal oxide. Y has a large ionic radius, which can act as a support framework after doping to inhibit surface structure phase transition and Li / Ni mixing. In addition, Y doping can also widen the Li ion transmission channel and improve the transmission rate of Li ions.

[0112] Zr doping can significantly improve the structural stability and thermal stability of the nickel-containing lithium transition metal oxide. Zr-O bond is strong, which can stabilize the lattice structure and prevent the precipitation of free oxygen. Zr doping can also expand the unit cell parameter, which is beneficial to the diffusion of Li ions. In addition, Zr doping can also reduce the irreversible capacity loss of lithium-rich NCM.

[0113] Sr doping is usually used in combination with other elements such as Zr to form a protective layer or a co-doped structure such as SrZrO3. Sr has a larger diameter and can act as a pillar to significantly expand the lattice unit parameters and the O-Li-O layer spacing, thereby improving the diffusion kinetics and rate performance of Li ions. Sr / Zr co-doping can also build a strong crystal framework to improve the structural stability and cycle performance of lithium transition metal oxides containing nickel.

[0114] Therefore, the addition of elements such as Al, B, Ti, Y, Zr, Sr, etc. can improve the electrochemical performance, structural stability, and cycle performance of lithium transition metal oxides containing nickel to varying degrees. These elements play a role by forming stable chemical bonds, widening the transmission channel, and inhibiting adverse phase changes.

[0115] In order to fully play the role of each element, in some embodiments, in the lithium-containing nickel-cobalt-manganese oxide material, and based on the lithium-containing nickel-cobalt-manganese oxide material, one or more of the following characteristics are met: 1) the mass content of Zr is 1000-3000 ppm; 2) the mass content of Al is 100-1000 ppm; 3) the mass content of B is 20-300 ppm.

[0116] The lithium-containing phosphate-based positive electrode material used in the present application can use any conventional material of this type, such as a lithium-containing phosphate-based positive electrode material including a lithium iron manganese phosphate material containing one or more of Al, B, Ca, Cr, Cu, K, Mg, Na, P, Si, Ti, V, Zn elements; optionally, the lithium iron manganese phosphate material includes one or more of Al, Ca, Na, Ti, V elements. The elements in the above-mentioned materials can exist in the lithium-containing phosphate-based positive electrode material in the form of doping or coating. Among them, the Al element can reduce the resistivity of the material, change the crystal structure, shorten the lithium ion transmission path, enhance the electrochemical performance, the Ca element can improve the structural stability of the material, improve the cycle life and rate performance of the battery monomer, the Na element and the V element can improve the electrical conductivity and cycle stability of the material, and the Ti element can change the crystal structure and improve the charge and discharge performance of the material.

[0117] In order to fully play the role of each element, based on the lithium iron manganese phosphate material, one or more of the following characteristics are met: 1) the mass content of Al is 100-1000 ppm; 2) the mass content of Ca is 50-300 ppm; 3) the mass content of Na is 50-600 ppm; 4) the mass content of Ti is 100-1000 ppm; 6) the mass content of V is 1000-3000 ppm.

[0118] In some embodiments, the positive electrode active layer contains a lithium-containing phosphate-based positive electrode material and a nickel-cobalt-manganese oxide material, the positive electrode material contains one or more of Al, Ca, Na, Ti, V, Zr, and B elements, and the mass content of each of Al, Ca, Na, Ti, V, Zr, and B in the positive electrode material satisfies: Al: 0.005%-0.1%; Ca: 0.0001%-0.02%; Na: 0.005%-0.06%; Ti: 0.005%-0.15%; V: 0.0001%-0.3%; Zr: 0.005%-0.2%; and B: 0.01%-0.1%.

[0119] In some embodiments, the lithium-containing phosphate-based positive electrode material includes a lithium iron manganese phosphate material, and the molar ratio of Mn to Fe in the lithium iron manganese phosphate material is 2:8-8:2, or 5:5-7:3. The appropriate molar ratio range of Mn to Fe helps comprehensively regulate the voltage plateau, transition metal elution, and gas generation during the cycle process of the lithium iron manganese phosphate material. The lithium iron manganese phosphate material with the above molar ratio has relatively stable cycle performance, and is beneficial to improving the energy density of the battery cell.

[0120] In order to improve the conductivity and surface stability of the lithium-containing phosphate-based positive electrode material, in some embodiments, the lithium-containing phosphate-based positive electrode material includes a carbon-containing coating layer, and the mass content of carbon in the lithium-containing phosphate-based positive electrode material is 1%-3%.

[0121] In order to improve the ion conductivity of the lithium-containing phosphate-based positive electrode material, in some embodiments, the surface of the lithium-containing phosphate-based positive electrode material includes an ion-conducting material, and the ion-conducting material includes one or more of C, Ti, Zr, Hf, Ge, and Sn elements.

[0122] In some embodiments, the specific capacity of the positive electrode active material is improved by the size grading of the material particles in the positive electrode active material. In the positive electrode material, the mass content of Fe in the particles with a particle size less than or equal to Dv10 is M1, the mass content of Fe in the particles with a particle size greater than or equal to Dv90 is M2, and M1 is greater than M2; and / or the mass content of Ni in the particles with a particle size less than or equal to Dv10 is M3, the mass content of Ni in the particles with a particle size greater than or equal to Dv90 is M4, and M3 is less than M4.

[0123] The Dv50 particle size of the particles is a well-known concept in the art, which refers to the particle size in the volume-based particle size distribution of the powder particles, reaching 50% of the cumulative volume from the small particle size side. The Dv50 particle size of the positive electrode material can be determined by a Malvern 3000 laser particle size analyzer according to the standard process and requirements of GB / T 19077.1-2016 / ISO 13320:2009 particle size distribution laser diffraction method.

[0124] By the above particle size control, the small particle size lithium-containing phosphate-based positive electrode material is combined with the large particle size nickel-containing lithium transition metal oxide, the small particle size can be filled in the gap of the large particle size, thus the compaction of the positive electrode active material can be improved; and this combination mode protects the lithium-containing phosphate-based positive electrode material, effectively reducing the crushing probability when the lithium-containing phosphate-based positive electrode material is cold-pressed under the same pressure.

[0125] In some embodiments, the energy density or cycle performance of the battery cell is improved by the particle form of the positive electrode material, and the positive electrode active material has one or more of the following characteristics:

[0126] 1) the particles of the nickel-containing lithium transition metal oxide are spherical or spheroidal polycrystalline particles, or the particles of the nickel-containing lithium transition metal oxide are single-crystal particles; 2) the particles of the lithium-containing phosphate-based positive electrode material are single-crystal particles. The specific capacity of the polycrystalline form of the nickel-containing lithium transition metal oxide is higher, so the energy density of the battery cell can be better improved. The structure of the single-crystal form of the nickel-containing lithium transition metal oxide is more stable, so the cycle performance of the battery cell can be better improved.

[0127] In some embodiments, in order to further improve the specific capacity of the nickel-containing lithium transition metal oxide, any one or more of the following particle size ranges is selected:

[0128] The volume particle size Dv50 of the polycrystalline particles of the nickel-containing lithium transition metal oxide is 1.5 μm-4.5 μm; the volume particle size Dv50 of the single-crystal particles of the nickel-containing lithium transition metal oxide is 7 μm-12 μm, which can be selected as 7 μm-10 μm.

[0129] In order to improve the rate performance of the battery cell, in some embodiments, the positive electrode sheet further comprises a conductive layer, and the conductive layer is arranged between the positive electrode current collector and the positive electrode active layer. The electronic transmission rate is improved by using the conductive layer, thereby improving the rate performance of the battery cell.

[0130] In order to improve the adhesion between the positive electrode current collector and the positive electrode active layer by using the conductive layer, in some embodiments, the conductive layer comprises a binder and a conductive material.

[0131] In some embodiments, the thickness of the conductive layer is 0.5 μm-2 μm. Thus, the purpose of improving the conductivity can be fully achieved by using the conductive layer, and the thickness of the conductive layer is avoided to be too large to affect the energy density of the battery cell.

[0132] The strength of the positive electrode current collector is related to its thickness, and generally the greater the thickness, the greater the strength, but the greater the strength, the worse the ductility, and also causes the energy density of the battery cell to decrease. During the charging and discharging cycle, the positive electrode active material expands and shrinks, and the greater the areal density of the positive electrode active layer, the more obvious the volume expansion and shrinkage of the positive electrode active layer, so the positive electrode current collector needs to have a certain strength to constrain the expansion, and also needs to have a certain ductility to adapt to the area increase caused by the expansion of the active layer. In some embodiments, the thickness of the positive electrode current collector is 9-17 μm, which can be selected as 10-13 μm. The positive electrode current collector in this thickness range has less effect on the energy density, and has good strength and ductility matching ability, thereby effectively reducing the risk of cracking of the current collector caused by the expansion of the battery cell during charging.

[0133] In some embodiments, the positive electrode current collector can use a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0134] In some embodiments, the positive electrode active layer can also optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin.

[0135] In some embodiments, the positive electrode active layer can also optionally include a conductive agent. As an example, the conductive agent can include at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0136] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methyl pyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying, cold pressing, etc., the positive electrode sheet can be obtained.

[0137] [Negative electrode sheet]

[0138] In some embodiments, in order to fully exert the capacity of the positive electrode active material, the areal density of the negative electrode active layer is 90 mg / 1540.25 mm2 - 170 mg / 1540.25 mm 2 ; optionally 110 mg / 1540.25 mm 2 - 160 mg / 1540.25 mm 2 .

[0139] In some embodiments, the corresponding compaction density of the negative electrode film layer of the battery cell is 1.04 g / cm 3 - 1.48 g / cm 3 ; optionally 1.23 g / cm 3 - 1.42 g / cm 3 The negative electrode sheet with the above compaction density has small swelling deformation and good electrolyte infiltration, thus improving the cycle performance of the battery cell.

[0140] In some embodiments, the negative electrode sheet further comprises a negative electrode conductive layer, the negative electrode conductive layer is arranged between the negative electrode current collector and the negative electrode active layer, and the thickness of the negative electrode conductive layer is 0.5 μm-3 μm, or 1 μm-2 μm. The negative electrode conductive layer improves the conductivity of the negative electrode sheet, and further improves the rate performance of the battery cell.

[0141] As with the above considerations for selecting the thickness of the positive electrode current collector, in some embodiments, the thickness of the negative electrode current collector is 4 μm-7 μm, or 4 μm-5 μm. The negative electrode current collector with the thickness in the range has less impact on the energy density, and has good strength and ductility matching ability, thus effectively reducing the risk of cracking of the current collector caused by swelling of the battery cell during charging.

[0142] In some embodiments, the above carbon material comprises composite graphite particles, the composite graphite particles comprise a body particle and a coating layer, the body particle comprises primary particles or secondary particles, and the body particle comprises artificial graphite; the coating layer is coated on the surface of the body particle, and the coating layer comprises amorphous carbon. The artificial graphite with amorphous carbon coating has a simple structure and high conductivity.

[0143] On the basis of improving the conductivity of the composite graphite particles, the specific capacity of the composite graphite particles is improved as much as possible, and in some embodiments, the mass content of the amorphous carbon in the coating layer can be selected to be 2% to 5% based on the total mass of the composite graphite particles.

[0144] In some embodiments, the negative electrode active layer has one or more layers. When the number of layers of the negative electrode active layer is multiple, the negative electrode active material with corresponding characteristics can be arranged in the negative electrode active layer of different layers according to different purposes.

[0145] In some embodiments, the negative active layer includes a first negative active layer and a second negative active layer, the first negative active layer is disposed on one side of the negative current collector, the negative material in the first negative active layer includes one or more of the composite graphite particles and the natural graphite, the second negative active layer is disposed on the side of the first negative active layer away from the negative current collector, the negative material in the second negative active layer includes the composite graphite particles. The first negative active layer is used to improve the energy density of the battery cell, and the second negative active layer is used to improve the charging rate of the battery cell.

[0146] In some embodiments, the volume average particle size Dv50 of the negative material in the first negative active layer is 7.5-19.5 μm, and optionally 12.5-18.5 μm. In some embodiments, the volume average particle size Dv50 of the negative material in the second negative active layer is 7.5-19.5 μm, and optionally 7.5-15.5 μm. The first negative active layer and the second negative active layer each use the negative material with the corresponding particle size. When the particle size of the negative material in the second negative active layer is smaller relative to the particle size of the negative material in the first negative active layer, the wettability of the negative active layer is better, and the migration path of lithium ions is short, which can improve the kinetic performance of the battery cell.

[0147] In order to maximize the contribution of the second negative active layer to the energy density of the battery cell, in some embodiments, the powder compaction density of the composite graphite particles under a pressure of 20,000 N is 1.5 g / cm 3 -1.85 g / cm 3 , or 1.55 g / cm 3 -1.75 g / cm 3 .

[0148] In some embodiments, the negative current collector can use a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base layer (such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0149] In some embodiments, the negative film layer can also optionally include a binder. As an example, the binder can be selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0150] In some embodiments, the negative electrode film layer further optionally comprises a conductive agent. As an example, the conductive agent can be selected from at least one of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0151] In some embodiments, the above-mentioned negative electrode conductive layer comprises a negative electrode binder and a negative electrode conductive material. Both the negative electrode binder and the negative electrode conductive material can be selected from the binder and the conductive agent in the above-mentioned negative electrode film layer.

[0152] In some embodiments, the negative electrode film layer further optionally comprises other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0153] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative electrode current collector, and after drying, cold pressing, and the like, a negative electrode sheet is obtained.

[0154] [Separator]

[0155] The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0156] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0157] In some embodiments, the separator comprises a porous base film and a functional layer arranged on at least one side of the porous base film. That is, the separator is a composite film. According to different functional needs, the corresponding functional layer is selected, which will not be described herein.

[0158] [Electrolyte]

[0159] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The type of the electrolyte is not particularly limited in the present application, and can be selected according to the needs. For example, the electrolyte can be liquid, gel, or all-solid-state.

[0160] In some embodiments, the above-mentioned battery cell further comprises an electrolyte, and the electrolyte comprises an electrolyte salt and a solvent.

[0161] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bis-trifluoromethanesulfonimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro oxalate borate, lithium di-oxalate borate, lithium difluoro di-oxalate phosphate, and lithium tetrafluoro oxalate phosphate.

[0162] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, methyl ethyl sulfone, and diethyl sulfone.

[0163] In some embodiments, the electrolyte solution can further optionally include an additive. As an example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0164] In some embodiments, the electrolyte solution has a conductivity of 10-20 mS / cm, and can be selected from 12-17 mS / cm. The above conductivity is a conductivity of the electrolyte solution at room temperature.

[0165] In some embodiments, the electrolyte solution includes lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonimide (LiFSI). The lithium bisfluorosulfonimide can improve the lithium ion transfer rate, thereby improving the charging rate of the battery cell, and has high-temperature stability, thus improving the high-temperature cycle performance of the battery cell.

[0166] In some embodiments, the molar concentration ratio of lithium bisfluorosulfonimide and lithium hexafluorophosphate is (2-5):10. Thus, on the basis of improving the cycle stability and charging rate of the battery cell using the above lithium salt, the excessive increase in the cost of the battery cell is controlled.

[0167] In some embodiments, the type and content of the inorganic component / lithium salt concentration in the electrolyte solution are those known in the art, and can be detected using equipment and methods known in the art, for example, the inorganic component / lithium salt concentration in the electrolyte solution can be qualitatively or quantitatively analyzed by ion chromatography according to the standard JY / T 020-1996 "General Ion Chromatography Analysis Method".

[0168] In the embodiments of the present application, the electrolyte can be taken as a sample, or the free electrolyte obtained from the battery after the battery has been discharged (discharged to the lower limit cutoff voltage so that the charged state of the battery is about 0% SOC) is taken as a sample, and the ion chromatography analysis method is used for detection.

[0169] In the embodiments of the present application, the types and contents of the organic components in the electrolyte are the meanings known in the art, and the devices and methods known in the art can be used for detection, for example, the qualitative and quantitative analysis of the organic components in the electrolyte can be performed by gas chromatography according to GB / T 9722-2006 “General rules for chemical reagents-gas chromatography”. In the embodiments of the present application, the electrolyte can be taken as a sample, or the free electrolyte obtained from the battery after the battery has been discharged (discharged to the lower limit cutoff voltage so that the charged state of the battery is about 0% SOC) is taken as a sample, and the ion chromatography analysis method is used for detection.

[0170] In some embodiments, the battery cell comprises a shell, the electrode assembly is arranged in the inner cavity of the shell, the positive electrode plate and the negative electrode plate are arranged in a laminated manner, the length of the shell is L1, the length of the positive electrode plate is L2, and L2 / L1 is 80%-99%, preferably L2 / L1 is 88%-99%, and the electrode assembly is arranged in the shell.

[0171] Thus, the volume energy density of the battery cell is further improved.

[0172] In some embodiments, the size of the shell has one or more of the following characteristics:

[0173] L1 is in the range of 300mm-950mm;

[0174] The height of the shell is 85mm-140mm;

[0175] The thickness of the shell is 10mm-20mm.

[0176] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, and polybutylene succinate, etc. can be listed.

[0177] In some embodiments, the shell is an aluminum shell or a steel shell.

[0178] In some embodiments, the injection coefficient of the battery cell is 1.9g / Ah-3.1g / Ah.

[0179] In some embodiments, the volumetric energy density of the battery cell is greater than or equal to 400 Wh / L, optionally 400 Wh / L-650 Wh / L, optionally 500-600 Wh / L.

[0180] In some embodiments, the positive electrode tab, the negative electrode tab, and the separator film can be formed into an electrode assembly by a winding process or a stacking process.

[0181] The shape of the battery cell is not particularly limited in the present application, which can be cylindrical, square, or any other shape. For example, FIG. 1 is an electrode assembly 52 of a battery cell in a square structure as an example.

[0182] In some embodiments, referring to FIG. 2, the outer package can include a shell 51 and a top cover assembly 53. The shell 51 can include a bottom plate and a side plate connected to the bottom plate, which enclose a receiving cavity. The shell 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can be arranged on the opening to close the receiving cavity. The positive electrode tab, the negative electrode tab, and the separator film can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be selected by those skilled in the art according to the specific actual needs.

[0183] The second embodiment of the present application also provides a battery device, which includes any one of the battery cells provided by the first embodiment, and the battery device includes a battery module, a battery pack, or an energy storage device.

[0184] In some embodiments, the battery device can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte.

[0185] In some embodiments, the battery cell can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more, which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0186] In the battery module, the plurality of battery cells can be arranged in sequence along the thickness direction of the battery cell. Of course, they can also be arranged in any other way. Further, the plurality of battery cells can be fixed by fasteners.

[0187] Optionally, the battery module can also include a housing having a receiving space, and the plurality of battery cells are received in the receiving space.

[0188] In some embodiments, the battery module described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0189] FIGS. 3 and 4 are a battery pack 1 as an example. Referring to FIGS. 3 and 4, the battery pack 1 can include a battery case and a plurality of battery modules 4 disposed in the battery case. The battery case includes an upper case 2 and a lower case 3, and the upper case 2 is capable of being disposed on the lower case 3 and forms an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery case in any manner.

[0190] In addition, the application also provides a power utilization device comprising the battery cell or the battery device provided by the application. The battery cell or the battery device can be used as a power supply of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0191] As the power utilization device, the battery cell, the battery module or the battery pack can be selected according to the use requirements thereof.

[0192] FIG. 5 is a power utilization device as an example. The power utilization device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the power utilization device for the battery cell, the battery pack or the battery module can be used.

[0193] [Embodiment]

[0194] Hereinafter, an embodiment of the application will be described. The embodiment described below is exemplary and is intended to explain the application only, and should not be understood as a limitation of the application. If a specific technique or condition is not mentioned in the embodiment, the technique or condition described in the literature in the art or according to the product manual is used. If the reagent or instrument used is not mentioned by the manufacturer, it is a conventional product that can be obtained by purchase.

[0195] Positive electrode tab

[0196] The positive electrode active layer comprises a positive electrode active material, a binder polyvinylidene fluoride, and a conductive agent acetylene black (mass ratio of 96.7:2.3:1.0). The thickness of the current collector aluminum foil is 13 μm. The positive electrode active layer is located on both sides of the aluminum foil. There is a positive electrode conductive layer between the positive electrode active layer and the aluminum foil. The positive electrode conductive layer is a film layer formed by uniformly mixing a positive electrode conductive agent, a positive electrode binder, and a solvent, coating on the surface of the positive electrode current collector, and drying. The thickness of the positive electrode conductive layer is 1 μm. The mass content of the positive electrode conductive agent in the positive electrode conductive layer is 50%. The mass content of the positive electrode binder in the positive electrode conductive layer is 50%. The length of the positive electrode tab is 592 mm.

[0197] Negative electrode tab

[0198] The negative active layer includes two layers, an upper layer (far from the current collector) and a lower layer (close to the current collector), the lower layer includes 96:1:2:1 of negative active material, conductive agent acetylene black, binder styrene butadiene rubber and thickening agent sodium carboxymethyl cellulose, the negative active material is composed of composite graphite particles (the composite graphite particles include artificial graphite and a carbon coating layer, the carbon coating layer is coated on the surface of the artificial graphite, the mass content of the carbon coating layer is 3.5%) and natural graphite at a mass ratio of 5:5, wherein the Dv50 of the composite graphite particles is 15.4 μm, and the powder compaction density under a pressure of 20000 N is 1.74 g / cm 3 ; the Dv50 of the natural graphite is 15.8 μm. The negative active material in the upper layer is the composite graphite particles, the Dv50 is 12.3 μm, and the powder compaction density under a pressure of 20000 N is 1.74 g / cm 3 .

[0199] The negative current collector is a copper foil of 5 μm, and there is a negative conductive layer between the copper foil and the lower film layer, the conductive primer layer is a film layer formed by uniformly mixing a negative conductive agent super-conductive carbon, a negative binder styrene butadiene rubber SBR, a thickening agent sodium carboxymethyl cellulose (CMC-Na) and a solvent water and then coating on the surface of the negative current collector and drying, the thickness is 1 μm, the mass content of the negative conductive agent in the negative conductive layer is 35%, the mass content of the negative binder in the negative conductive layer is 60%, and the mass content of the thickening agent in the negative conductive layer is 5%.

[0200] Electrolyte

[0201] The electrolyte includes organic solvent ethyl acetate EA, ethylene carbonate EC, methyl ethyl carbonate EMC (mass ratio 50:35:15), 0.9 mol / L of lithium hexafluorophosphate (LiPF6) and 0.3 mol / L of lithium bisfluorosulfonylimide LiFSI as lithium salt, 2.5% of additive vinylene carbonate VC, 1% of fluoroethylene carbonate FEC, 0.5% of 1,3-propylene sulfite PS, 0.5% of vinyl sulfite DTD and 0.5% of lithium difluorophosphate LiPO2F2. The conductivity of the electrolyte is 11 mS / cm.

[0202] Separator film

[0203] A polyethylene (PE) film coated with a nano-aluminum oxide coating is used as the separator film.

[0204] Battery cell

[0205] An electrode assembly was obtained by stacking the positive electrode sheet, the separator, and the negative electrode sheet. The electrode assembly was put into an outer packaging square aluminum case (length: 600 mm, thickness: 19 mm, height: 105 mm), and after drying, an electrolyte was injected, with an injection coefficient of 2.9. After the processes of packaging, high-temperature standing, formation, secondary injection, aging, and capacity, a battery monomer was obtained.

[0206] The lithium transition metal oxides containing nickel and the lithium-containing phosphate-based positive electrode materials used in the examples and comparative examples were all conventional materials in the art or were prepared using conventional methods. The C mass content in the lithium-containing phosphate-based positive electrode materials used in all the examples and comparative examples was 2%.

[0207] The powder resistivity in Table 1 was the powder resistivity of the material at 12 MPa. In addition to the elements in the chemical formula, the lithium transition metal oxides containing nickel in Table 1 also contained other elements M. The subscripts of Ni, Co, and Mn in the chemical formula were the data after rounding, and because the content of the other elements M was trace, these elements and their atomic numbers were not reflected in the chemical formula, and element M did not affect the battery performance. The content of the other elements M is described below. The chemical formula was LiNi 0.8 Co 0.1 Mn 0.1 O2, the content of the other elements in the lithium transition metal oxide containing nickel was as follows: the mass content of Al was 0.062%, the mass content of B was 0.0037%, the mass content of Ti was 0.0003%, the mass content of Y was 0.008%, the mass content of Zr was 0.25%, and the mass content of Sr was 0.0001%; the chemical formula was LiNi 0.6 Co 0.2 Mn 0.2 O2, the content of the other elements in the lithium transition metal oxide containing nickel was as follows: the mass content of Al was 0.04%, the mass content of B was 0.0028%, the mass content of Ti was 0.0003%, the mass content of Y was 0.0076%, the mass content of Zr was 0.24%, and the mass content of Sr was 0.0001%; the chemical formula was LiNi 0.9 Co 0.05 Mn 0.05 O2, the content of the other elements in the lithium transition metal oxide containing nickel was as follows: the mass content of Al was 0.068%, the mass content of B was 0.0033%, the mass content of Ti was 0.0003%, the mass content of Y was 0.008%, the mass content of Zr was 0.21%, and the mass content of Sr was 0.0001%; the chemical formula was LiNi 0.4 Co 0.2 Mn 0.4The content of other elements in the nickel-containing lithium transition metal oxide of O2 is as follows: the mass content of Al is 0.036%, the mass content of B is 0.003%, the mass content of Ti is 0.0003%, the mass content of Y is 0.0079%, the mass content of Zr is 0.25%, and the mass content of Sr is 0.0001%.

[0208] A:B in Table 1 represents the mass ratio of the nickel-containing lithium transition metal oxide and the lithium-containing phosphate-based positive electrode material.

[0209] Material test:

[0210] The powder resistivity test method of the positive electrode material:

[0211] For the positive electrode tab of the battery monomer, the positive electrode tab is washed with DMC (dimethyl carbonate) and the positive electrode tab is dried and calcined to collect the positive electrode material in the positive electrode active layer. After the powder resistance tester is turned on and the equipment is stable, a certain mass of positive electrode material is weighed and added to the feeding cavity and the feeding cavity depth is adjusted. According to the target pressure and the cavity area in the feeding cavity, the target pressure is applied, and the powder resistivity test result under 12 MPa pressure is collected.

[0212] The BET specific surface area test method of the positive electrode material:

[0213] For the positive electrode tab of the battery monomer, the positive electrode tab is washed with DMC (dimethyl carbonate) and the positive electrode tab is dried and calcined to collect the positive electrode material in the positive electrode active layer. According to GB / T 19587-2017, the positive electrode material is tested by nitrogen adsorption specific surface area analysis test method, and the BET (Brunauer Emmett Teller) method is used to calculate, wherein the nitrogen adsorption specific surface area analysis test can be performed by Tri-Star 3020 type specific surface area and pore size analyzer of American Micromeritics company.

[0214]

[0215] Test:

[0216] The compaction density of the positive electrode active layer refers to the compaction density of the positive electrode active layer after charging the battery monomer to 4.2V at 25℃ and 0.33C rate, and then constant voltage charging to less than 0.05C. In addition, the compaction density of the negative electrode active layer under the above conditions is 1.41g / cm 3 .

[0217] The test method of the area density and the compaction density:

[0218] Take the single-sided coated positive electrode sheet (if it is a double-sided coated electrode sheet, the positive electrode film layer on one side can be wiped off first), cut it into a small round piece with an area of S1, weigh it, and record it as M1. Then wipe off the positive electrode active layer of the above weighed positive electrode sheet, weigh the positive current collector, and record it as M0. The single-sided coating weight of the positive electrode active layer (i.e. the area density) = (the weight of the positive electrode sheet M1 - the weight of the positive current collector M0) / S1, the thickness of the positive electrode active layer = the thickness of the positive electrode sheet H1 - the thickness of the positive current collector H0, the compaction density of the positive electrode active layer = the single-sided coating weight of the positive electrode active layer / the thickness of the single-sided positive electrode active layer. The positive electrode active layer in the above test includes the positive electrode active layer and the positive electrode conductive layer in the aforementioned positive electrode sheet.

[0219] Volume energy density test method:

[0220] Place the battery monomer at 25°C, charge it to 4.2V at 0.33C constant current, and then charge it to 0.05C at constant voltage; discharge it to 2.5V at 0.33C constant current to obtain the discharge energy A0 at this time, unit: Wh; measure the length, width and height of the battery monomer (generally calculated by the size of the battery shell, excluding the height of the electrode terminal, and excluding the insulating film outside the shell) using a caliper, calculate the volume V0 of the battery monomer, unit L; the volume energy density VED of the battery monomer = A0 / V0, unit Wh / L.

[0221] DCR test of battery monomer

[0222] The method can be referred to in GB / T 31467 "HEV High Power Lithium Ion Power Battery Performance Test Specification". Specifically as follows:

[0223] At room temperature, charge the battery monomer to 4.2V at 0.33C constant current, stand for 1min, then charge to 4.2V at 0.1C constant current, discharge to 2.0V at 0.33C constant current, record the discharge capacity A0 at this time, unit Ah, then charge 0.5A0 Ah at 0.33C constant current, adjust the SOC to 50%.

[0224] After placing the battery monomer at 25°C for 2h, discharge it at a current of 2C for 10s, record ΔU discharge, ΔI discharge, and calculate the discharge DCR data of the lithium ion battery through the following formula, R discharge = ΔU discharge / ΔI discharge,

[0225] Wherein, ΔU discharge represents the voltage change within 10s of discharging start, and ΔI discharge represents the current value within 10s of discharging start.

[0226] Cycle life test method:

[0227] Cycle number of battery cell to 80% SOH:

[0228] The battery cell was charged at 1C constant current to a charge cut-off voltage of 4.2V at 45℃, and then discharged at 1C constant current to 2.0V, which was one charge-discharge cycle. The above charge-discharge cycle steps were repeated until the cycle capacity retention rate (i.e. Cn / C0x100%) was 80% (the discharge capacity at 1C constant current to 2.0V was recorded as C0, and Cn was the discharge capacity of the nth cycle), and the cycle number was recorded. The more the cycle number, the better the cycle performance of the battery cell.

[0229] The test results are recorded in Table 2.

[0230] Table 2

[0231] According to the comparison of Examples 2 to 14 and Comparative Example 1, it can be seen that the energy density and cycle performance of the battery cell can be improved after mixing lithium manganese iron phosphate with the lithium transition metal oxide containing nickel.

[0232] According to the comparison of Comparative Example 2, Example 13 and Example 14, it can be seen that when the content of lithium manganese iron phosphate in the positive electrode material is reduced to less than 50%, although the energy density of the battery cell increases due to the increase of lithium content in the lithium transition metal oxide containing nickel, the internal resistance of the battery cell is obviously larger.

[0233] According to the comparison of Comparative Example 3, Example 13 and Example 14, it can be seen that by adjusting the powder resistivity of the lithium transition metal oxide containing nickel, when the powder resistivity of the positive electrode material is controlled to be less than 5000Ω·cm, it is beneficial to reduce the internal resistance of the battery cell.

[0234] According to the comparison of Comparative Example 4 and Examples 9 to 14, it can be seen that when the nickel content in the lithium transition metal oxide containing nickel is less than 30%, not only does it result in a higher powder resistivity of the positive electrode material, which makes the DCR internal resistance of the battery device higher, but also it affects the energy density of the battery device.

[0235] Although the present application has been described with reference to the preferred embodiments, various modifications can be made to it without departing from the scope of the application, and equivalent parts can be substituted for the parts thereof. In particular, the technical features mentioned in each embodiment can be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, comprising an electrode assembly, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet, and a separator film between the positive electrode sheet and the negative electrode sheet, wherein, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer provided on at least one side of the negative electrode current collector, the negative electrode active layer comprising a negative electrode material, the negative electrode material comprising a carbon material; the positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer provided on at least one side of the positive electrode current collector, the positive electrode active layer comprising a positive electrode material, the positive electrode material comprising a lithium-containing phosphate-based positive electrode material and a nickel-containing lithium transition metal oxide, the mass content of the nickel-containing lithium transition metal oxide in the positive electrode material is 5%-50%, the mass content of Ni in the nickel-containing lithium transition metal oxide is greater than or equal to 30%; the powder resistivity of the positive electrode material under 12MPa is 30Ω·cm-5000Ω·cm. the mass content of the lithium-containing phosphate-based positive electrode material in the positive electrode material is 50%-95%, which can be 50%-70%. the molar content of Ni in the nickel-containing lithium transition metal oxide is 75%-95%, based on the total molar amount of transition metal elements in the nickel-containing lithium transition metal oxide. the powder resistivity of the positive electrode material under 12MPa is 30Ω·cm-2000Ω·cm. the powder resistivity of the positive electrode material under 12MPa is 30Ω·cm-1500Ω·cm. the powder resistivity of the positive electrode material under 12MPa is 80Ω·cm-1500Ω·cm. the powder resistivity of the positive electrode material under 12MPa is 30Ω·cm-400Ω·cm. the powder resistivity of the nickel-containing lithium transition metal oxide under 12MPa is 100Ω·cm-10000Ω·cm, which can be 100Ω·cm-5000Ω·cm, and further can be 100-4000Ω·cm. the powder resistivity of the phosphate-based positive electrode material under 12MPa is 4-80Ω·cm. the mass content of Ni element is 1.7%-26.5%, which can be 10%-23.5%, based on the total mass of the positive electrode material. the lithium-containing phosphate-based positive electrode material comprises a lithium iron manganese phosphate material, the mass content of Fe element is 4.5%-17%, which can be 4.5%-10.3%, based on the total mass of the positive electrode material. the lithium-containing phosphate-based positive electrode material comprises a lithium iron manganese phosphate material, the mass content of Mn element is 3.4%-22.5%, based on the total mass of the positive electrode material. the nickel-containing lithium transition metal oxide comprises one or more of a lithium-containing nickel cobalt manganese oxide material and a lithium-containing nickel cobalt aluminum oxide material. the nickel-containing lithium transition metal oxide comprises a lithium-containing nickel cobalt manganese oxide, and the lithium-containing nickel cobalt manganese oxide material contains at least one of Zr, Al, B, Fe, Ca, Sr, Ti, V, Y elements. ​ ​ ​ ​ 2. The battery cell of claim 1, wherein, ​ 3. The battery cell of claim 1 or 2, wherein, ​ 4. The battery cell of any one of claims 1-3, wherein, ​ 5. The battery cell of any one of claims 1-4, wherein, ​ 6. The battery cell of any one of claims 1-5, wherein, ​ 7. The battery cell of any one of claims 1-6, wherein, ​ 8. The battery cell of any one of claims 1-7, wherein, ​ 9. The battery cell of any one of claims 1-8, wherein, ​ 10. The battery cell of any one of claims 1 to 9, wherein, ​ 11. The battery cell of any one of claims 1 to 10, wherein, ​ 12. The battery cell of any one of claims 1-11, wherein, ​ 13. The battery cell of any one of claims 1-12, wherein, The areal density of the positive electrode active layer is 200 mg / 1540.25 mm 2 - 370 mg / 1540.25 mm 2 , optionally 240 mg / 1540.25 mm 2 - 340 mg / 1540.25 mm 2 .

14. The battery cell of any one of claims 1-13, wherein, The powder compaction density of the positive electrode material is 2.5 g / cm 3 -2.8 g / cm 3 .

15. The battery cell of any one of claims 1-14, wherein, The lithium-containing phosphate-based positive electrode material includes a lithium iron phosphate material, the battery cell is configured such that the compaction density of the positive electrode active layer corresponding to the battery cell when in a 100% SOC state is 2.55 g / cm 3 - 3.00 g / cm 3 .

16. The battery cell of any one of claims 1-14, wherein, The lithium-containing phosphate-based positive electrode material includes a lithium iron manganese phosphate material, the battery cell is configured such that the compaction density of the positive electrode active layer corresponding to the battery cell when in a 100% SOC state is 2.40 g / cm 3 - 2.90 g / cm 3 .

17. The battery cell of any one of claims 1-16, wherein, The BET specific surface area of the positive electrode material is 7 m 2 / g-18 m 2 / g.

18. The battery cell of any one of claims 1-17, wherein, ​ 19. The battery cell of any one of claims 1-18, wherein, ​ 20. The battery cell of claim 19, wherein, The lithium-containing nickel-cobalt-manganese oxide includes one or more of Zr, Al, B, Fe elements, and satisfies one or more of the following characteristics based on the lithium-containing nickel-cobalt-manganese oxide material: 1) the mass content of Zr is 1000-3000 ppm; 2) the mass content of Al is 100-1000 ppm; 3) the mass content of B is 20-300 ppm.

21. The battery cell of any one of claims 1-20, wherein, The lithium-containing phosphate-based positive electrode material includes a lithium iron manganese phosphate material containing one or more of Al, B, Ca, Cr, Cu, K, Mg, Na, P, Si, Ti, V, Zn elements.

22. The battery cell of claim 21, wherein, The lithium iron manganese phosphate material contains one or more of Al, Ca, Na, Ti, V elements, and satisfies one or more of the following characteristics based on the lithium iron manganese phosphate material: 1) the mass content of Al is 100-1000 ppm; 2) the mass content of Ca is 50-300 ppm; 3) the mass content of Na is 50-600 ppm; 4) the mass content of Ti is 100-1000 ppm; 6) the mass content of V is 1000-3000 ppm.

23. The battery cell of any one of claims 1-22, wherein, The positive electrode material contains a lithium iron manganese phosphate material and a nickel-cobalt-manganese oxide material, and contains one or more of Al, Ca, Na, Ti, V, Zr, B elements in the positive electrode material, and the mass content of each satisfies: Al:0.005％-0.1％； Ca: 0.0001%-0.02%; Na: 0.005%-0.06%; Ti: 0.005%-0.15%; V:0.0001％-0.3％； Zr:0.005％-0.2％； B:0.01％-0.1％。 24. The battery cell of any one of claims 1-23, wherein, The lithium-containing phosphate-based positive electrode material includes a lithium iron manganese phosphate material, and the molar ratio of Mn to Fe in the lithium iron manganese phosphate material is 2:8-8:2, which can be 5:5-7:

3.

25. The battery cell of any one of claims 1-24, wherein, The lithium-containing phosphate-based positive electrode material includes a carbon-containing coating layer, and the mass content of carbon in the lithium-containing phosphate-based positive electrode material is 1%-3%.

26. The battery cell of any one of claims 1-25, wherein, The surface of the lithium-containing phosphate-based positive electrode material includes an ion-conducting material, and the ion-conducting material includes one or more of C element, Ti element, Zr element, Hf element, Ge element or Sn element.

27. The battery cell of any one of claims 1-26, wherein, In the positive electrode material, The mass content of Fe element in particles with a particle size less than or equal to Dv10 is M1, the mass content of Fe element in particles with a particle size greater than or equal to Dv90 is M2, and M1 is greater than M2; and / or The mass content of Ni element in particles with a particle size less than or equal to Dv10 is M3, the mass content of Ni element in particles with a particle size greater than or equal to Dv90 is M4, and M3 is less than M4.

28. The battery cell of any one of claims 1-27, wherein, The positive electrode material has one or more of the following characteristics: 1) the particles of the lithium-containing nickel-cobalt-manganese oxide are spherical or quasi-spherical polycrystalline particles, or the particles of the lithium-containing nickel-cobalt-manganese oxide are single crystal particles; optionally, the volume particle size Dv50 of the single crystal particles of the lithium-containing nickel-cobalt-manganese oxide is 1.5-4.5 μm; optionally, the volume particle size Dv50 of the polycrystalline particles of the lithium-containing nickel-cobalt-manganese oxide is 7-12 μm; 2) The lithium-containing phosphate-based positive electrode material particles are single crystal particles.

29. The battery cell of any one of claims 1-28, wherein, The positive electrode sheet further comprises an electrically conductive layer, which is arranged between the positive current collector and the positive active layer.

30. The battery cell of claim 29, wherein, The electrically conductive layer comprises a binder and an electrically conductive material, and the thickness of the electrically conductive layer is 0.5-2 μm.

31. The battery cell of any one of claims 1-30, wherein, The thickness of the positive current collector is 9-17 μm, and optionally 10-13 μm.

32. The battery cell of any one of claims 1-31, wherein, The areal density of the negative active layer is 90 mg / 1540.25 mm 2 - 170 mg / 1540.25 mm 2 ; optionally 110 mg / 1540.25 mm 2 - 160 mg / 1540.25 mm 2 .

33. The battery cell of claim 33, wherein, The lithium-containing phosphate-based positive electrode material includes a lithium iron manganese phosphate material, and the battery cell is configured such that the compaction density of the negative electrode film layer corresponding to the 100% SOC state is 1.04 g / cm 3 -1.48 g / cm 3 ; and optionally 1.23 g / cm 3 -1.44 g / cm 3 .

34. The battery cell of any one of claims 1-33, wherein, The negative electrode sheet further comprises a negative electrode electrically conductive layer, which is arranged between the negative current collector and the negative active layer, and the thickness of the negative electrode electrically conductive layer is 0.5-3 μm, and optionally 1-2 μm.

35. The battery cell of any one of claims 1-34, wherein, The thickness of the negative current collector is 4-7 μm, and optionally 4-5 μm.

36. The battery cell of any one of claims 1-35, wherein, The carbon material comprises composite graphite particles, which comprise: bulk particles, which comprise primary particles and / or secondary particles, and the bulk particles comprise artificial graphite; and a coating layer, which coats the surface of the bulk particles, and the coating layer comprises amorphous carbon.

37. The battery cell of claim 36, wherein, The mass content of amorphous carbon in the coating layer is 2-5% based on the total mass of the composite graphite particles.

38. The battery cell of any one of claims 1-37, wherein, The negative active layer comprises: a first negative active layer, which is arranged on one side of the negative current collector, and the negative material of the first negative active layer comprises one or more of composite graphite particles and natural graphite, and optionally the volume average particle size Dv50 of the negative material in the first negative active layer is 7.5-19.5 μm, and optionally 12.5-18.5 μm, and a second negative active layer, which is arranged on the side of the first negative active layer away from the negative current collector, and the negative material of the second negative active layer comprises composite graphite particles, and optionally the volume average particle size Dv50 of the negative material in the second negative active layer is 7.5-19.5 μm, and optionally 7.5-15.5 μm.

39. The battery cell of any one of claims 36-38, wherein, The powder compaction density of the composite graphite particles under 20000N pressure is 1.5g / cm 3 -1.85g / cm 3 , optionally 1.55g / cm 3 -1.75g / cm 3 .

40. The battery cell of any one of claims 1-39, wherein, The battery cell further comprises an electrolyte, and the conductivity of the electrolyte is 10-20 mS / cm, and optionally 12-17 mS / cm.

41. The battery cell of claim 40, wherein, The electrolyte comprises lithium hexafluorophosphate and lithium bisfluorosulfonylimide, and the molar concentration ratio between the lithium bisfluorosulfonylimide and the lithium hexafluorophosphate is (2-5):

10.

42. The battery cell of claims 1-41, wherein, The battery cell further comprises a shell, the electrode assembly is arranged in the shell, the positive electrode sheet and the negative electrode sheet are arranged in a stacked manner, the length of the shell is L1, the length of the positive electrode sheet is L2, and L2 / L1 is 80-99%, and preferably L2 / L1 is 88-99%.

43. The battery cell of claim 42, wherein, The size of the shell has one or more of the following characteristics: The L1 is in the range of 300-950 mm; The height of the shell is 85-140 mm; The thickness of the shell is 10-20 mm.

44. The battery cell of any one of claims 42-43, wherein, The shell is an aluminum alloy shell, an alloy steel shell, or a titanium alloy shell.

45. The battery cell of any one of claims 40-44, wherein, The liquid injection coefficient of the battery cell is 1.9-3.1 g / Ah, and optionally 2.4-3.0 g / Ah.

46. The battery cell of claims 42-45, wherein, The volumetric energy density of the battery cell is greater than or equal to 400 Wh / L, optionally 400 Wh / L-650 Wh / L, optionally 500-600 Wh / L.

47. A battery device comprising the battery cell of any one of claims 1-46, the battery device comprising a battery module, a battery pack, or an energy storage device.

48. An electrically powered device comprising the battery cell of any one of claims 1-46, or the battery device of claim 47.

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