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 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. The positive electrode material comprises a nickel-containing lithium transition metal oxide and a lithium-containing phosphate-based positive electrode material. In the nickel-containing lithium transition metal oxide, the molar content of the Ni element relative to the metallic elements other than the lithium element is greater than or equal to 50%. In the lithium-containing phosphate-based positive electrode material, the molar content of the Mn element relative to the metallic elements other than the lithium element is 50% to 90%. The areal density of the positive electrode active layer is 190 mg / 1540.25 mm2 to 380 mg / 1540.25 mm2.

Description

Battery cell, battery device, and electric device Cross-reference to Related Applications This application claims priority to Chinese Patent Application No. 202411088614.X, filed on August 8, 2024, entitled “Battery cell, battery device, and electric device,” and Chinese Patent Application No. 202411174838.2, filed on August 26, 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] Lithium iron phosphate positive electrode material is widely used in the positive electrode of secondary batteries due to its low cost, but its low energy density limits its application. In order to improve its energy density, some technologies attempt to compound lithium iron phosphate and manganese phosphate to form lithium manganese iron phosphate. With the increase of manganese content in lithium manganese iron phosphate, although the energy density is improved, the cycle performance is deteriorated. SUMMARY

[0003] The present application provides a battery cell, a battery device, and an electric device to improve the energy density output performance and cycle performance of the battery cell.

[0004] A first aspect of the present application provides 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 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 active layer comprising a positive electrode material, the positive electrode material comprising a lithium transition metal oxide containing nickel and a lithium-containing phosphate-based positive electrode material, the molar content of Ni element in the lithium transition metal oxide containing nickel is greater than or equal to 50% in terms of the total molar amount of other metal elements in the lithium transition metal oxide containing nickel except for lithium element; the molar content of Mn element in the lithium-containing phosphate-based positive electrode material is 50%-90% in terms of the total molar amount of other metal elements in the lithium-containing phosphate-based positive electrode material except for lithium element, and the area density of the positive electrode active layer is 190 mg / 1540.25 mm 2 -380 mg / 1540.25 mm 2 .

[0005] The addition of the lithium-containing phosphate-based positive electrode material makes the positive electrode material have a lower cost than the pure system of the nickel-containing lithium transition metal oxide positive electrode material.

[0006] The molar content of the Ni element in the lithium-containing transition metal oxide is greater than or equal to 50%, which is a high-nickel-content lithium-containing transition metal oxide, has a higher gram capacity, and thus can provide a higher energy density for the battery monomer; the molar content of the Mn element in the lithium-containing phosphate-based positive electrode material is 50%-90%, which is a high-manganese-content lithium manganese iron phosphate salt, has a higher platform voltage, and thus can provide a higher energy density for the battery monomer, and the positive electrode active layer is provided to have a high area density of 190 mg / 1540.25 mm 2 -380 mg / 1540.25 mm 2 , so that the battery monomer with the above positive electrode material has a high energy density output.

[0007] At the same time, considering that when the area density is too large, the positive electrode active layer including the mixed positive electrode material is difficult to compact to the surface of the current collector due to the limitation of the processing technology, resulting in serious powder falling of the pole piece, increasing the difficulty of the preparation process of the battery monomer, and thus it is difficult to realize the production of the battery monomer with high energy density, therefore, the energy density is controlled to be below 380 mg / 1540.25 mm 2 . In addition, when the content of the Mn element in the lithium-containing phosphate-based positive electrode material is too high, the gram capacity of the lithium-containing phosphate-based positive electrode material is too low, which limits the improvement of the energy density of the battery monomer, therefore, the content of the Mn element in the lithium-containing phosphate-based positive electrode material is controlled to be less than 90%.

[0008] In any embodiment of the first aspect of the application, the area density of the positive electrode active layer is 200 mg / 1540.25 mm 2 -350 mg / 1540.25 mm 2 .

[0009] In any embodiment of the first aspect of the application, the mass ratio of the Fe element to the Ni element in the positive electrode material ranges from (0.4-10):1.

[0010] In any embodiment of the first aspect of the application, the molar content of the Ni element in the nickel-containing lithium transition metal oxide is 70%-95%, and can be 80%-95%, based on the total molar amount of the other metal elements in the nickel-containing lithium transition metal oxide except for the lithium element.

[0011] In any embodiment of the first aspect of the application, the molar content of the Mn element in the lithium-containing phosphate-based positive electrode material is 50%-70%, based on the total molar amount of the other metal elements in the lithium-containing phosphate-based positive electrode material except for the lithium element.

[0012] In any embodiment of the first aspect of the application, the battery cell is configured such that the compaction density of the positive active layer corresponding to the battery cell when in a 100% SOC state is 2.32 g / cm 3 - 3.18 g / cm 3 , optionally 2.53 g / cm 3 - 2.84 g / cm 3 .

[0013] In any embodiment of the first aspect of the application, the compaction density of the powder of the positive electrode material is > 2.5 g / cm at 30000 N 3 , optionally 2.5 g / cm 3 - 2.8 g / cm 3 .

[0014] In any embodiment of the first aspect of the application, the lithium transition metal oxide containing nickel comprises a lithium-containing nickel-cobalt-manganese oxide containing one or more of the elements Zr, Al, B, Fe, Ca, Sr, Ti, V or Y.

[0015] In any embodiment of the first aspect of the application, the lithium transition metal oxide containing nickel comprises a lithium-containing nickel-cobalt-manganese oxide containing one or more of the elements Zr, Al, B or Fe.

[0016] In any embodiment of the first aspect of the application, in the lithium-containing nickel-cobalt-manganese oxide, the mass content of the elements satisfies at least one of: the content of Zr is 1000-3000 ppm, the content of Al is 100-1000 ppm, the content of B is 50-300 ppm.

[0017] In any embodiment of the first aspect of the application, the lithium-containing phosphate-based positive electrode material comprises lithium manganese iron phosphate containing one or more of the elements Al, B, Ca, Cr, Cu, K, Mg, Na, P, Si, Ti, V or Zn.

[0018] In any embodiment of the first aspect of the application, the lithium manganese iron phosphate contains one or more of the elements Al, Ca, Na, Ti or V.

[0019] In any embodiment of the first aspect of the application, in the lithium manganese iron phosphate, the mass content of the elements satisfies at least one of: the content of Al is 100-1000 ppm, the content of Ca is 50-300 ppm, the content of Na is 50-300 ppm, the content of Ti is 100-1000 ppm, the content of V is 1000-3000 ppm.

[0020] In any embodiment of the first aspect of the present application, the positive electrode active layer contains lithium-containing phosphate-based positive electrode material and nickel-cobalt-manganese oxide, the positive electrode active layer contains one or more of Al, B, Ca, Fe, Sr, Ti, V, Y or Zn elements, and in the positive electrode material, 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%.

[0021] In any embodiment of the first aspect of the present application, 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%.

[0022] In any embodiment of the first aspect of the present application, 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.

[0023] In any embodiment of the first aspect of the present application, the particles of the nickel-containing lithium transition metal oxide are spherical or spheroidal polycrystalline particles, and the particles of the lithium-containing phosphate-based positive electrode material are single-crystal particles.

[0024] In any embodiment of the first aspect of the present application, the particles of the nickel-containing lithium transition metal oxide are single-crystal particles, and the particles of the lithium-containing phosphate-based positive electrode material are single-crystal particles.

[0025] In any embodiment of the first aspect of the present application, the volume particle size Dv50 of the single-crystal particles of the nickel-containing lithium transition metal oxide is 1 μm-5 μm, which can be 1.5 μm-3 μm.

[0026] In any embodiment of the first aspect of the present application, the volume particle size Dv50 of the polycrystalline particles of the nickel-containing lithium transition metal oxide is 7 μm-12 μm.

[0027] In any embodiment of the first aspect of the present application, the volume particle size Dv50 of the lithium-containing phosphate-based positive electrode material is 0.1 μm-15 μm, or 0.5 μm-2 μm.

[0028] In any embodiment of the first aspect of the present application, the positive electrode sheet further includes a positive electrode conductive layer, and the positive electrode conductive layer is arranged between the positive electrode current collector and the positive electrode active layer.

[0029] In any embodiment of the first aspect of the application, the positive electrode conductive layer comprises a positive electrode binder and a positive electrode conductive material, and / or the thickness of the positive electrode conductive layer is 1-2 μm.

[0030] In any embodiment of the first aspect of the application, the thickness of the positive electrode current collector is 9-17 μm, optionally 10-13 μm.

[0031] In any embodiment of the first aspect of the application, the areal density of the negative electrode active layer is 95 mg / 1540.25 mm 2 -180 mg / 1540.25 mm 2 , optionally 130 mg / 1540.25 mm 2 -150 mg / 1540.25 mm 2 .

[0032] In any embodiment of the first aspect of the application, the compaction density of the negative electrode active layer corresponding to the battery cell when in a 100% SOC state is 1.04 g / cm 3 -1.48 g / cm 3 , optionally 1.23 g / cm 3 -1.38 g / cm 3 .

[0033] In any embodiment of the first aspect of the application, the carbon material comprises composite graphite particles, the composite graphite particles comprising: a bulk particle, the bulk particle comprising secondary particles, the bulk particle comprising artificial graphite; and a coating layer, the coating layer being coated on the surface of the bulk particle, the coating layer comprising amorphous carbon.

[0034] In any embodiment of the first aspect of the application, the mass content of amorphous carbon in the coating layer is 2%-5% based on the total mass of the composite graphite particles.

[0035] In any embodiment of the first aspect of the application, the powder compaction density of the composite graphite particles under a pressure of 20,000 N is 1.5 g / cm 3 -1.7 g / cm 3 , or 1.55 g / cm 3 -1.65 g / cm 3 .

[0036] In any embodiment of the first aspect of the application, the negative active layer comprises: a first negative active layer disposed on one side of the negative current collector, the first negative active layer comprising one or more of the composite graphite particles and the natural graphite, the volume average particle size Dv50 of the negative active material in the first negative active layer being 7.5-19.5 μm, optionally 12.5-18.5 μm, and a second negative active layer disposed on the side of the first negative active layer away from the negative current collector, the second negative active layer comprising the composite graphite particles, the volume average particle size Dv50 of the negative active material in the second negative active layer being 7.5-19.5 μm, optionally 7.5-15.5 μm.

[0037] In any embodiment of the first aspect of the application, the negative electrode sheet further comprises a negative conductive layer, the negative conductive layer being disposed between the negative current collector and the negative active layer.

[0038] In any embodiment of the first aspect of the application, the negative conductive layer comprises a negative binder and a negative conductive material, the thickness of the negative conductive layer being 1-2 μm.

[0039] In any embodiment of the first aspect of the application, the thickness of the negative current collector is 4-7 μm, optionally 4-5 μm.

[0040] In any embodiment of the first aspect of the application, the battery cell further comprises an electrolyte, the electrolyte comprising lithium hexafluorophosphate and lithium bisfluorosulfonylimide.

[0041] In any embodiment of the first aspect of the application, the molar concentration ratio of lithium bisfluorosulfonylimide to lithium hexafluorophosphate is (2-5):10.

[0042] In any embodiment of the first aspect of the application, the battery cell further comprises a shell, the electrode assembly being disposed in an inner cavity of the shell, the positive electrode sheet and the negative electrode sheet being disposed in a stacked manner, the length of the shell being L1, the length of the positive electrode sheet being L2, L2 / L1 being 80%-99%, optionally 88%-99%.

[0043] In any embodiment 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.

[0044] In any embodiment of the first aspect of the application, the shell is an aluminum shell or a steel shell.

[0045] In any embodiment of the first aspect of the application, the battery cell injection coefficient is 1.9-3.1 g / Ah.

[0046] In any embodiment of the first aspect of the present application, the volumetric energy density of the battery cell is 470-570 Wh / L.

[0047] The second aspect of the present application provides a battery device comprising the battery cell provided in any embodiment of the first aspect, and the battery device comprises a battery module, a battery pack or an energy storage device.

[0048] The third aspect of the present application provides a power consumption device comprising the battery cell provided in any embodiment of the first aspect or the battery device provided in any embodiment of the second aspect. BRIEF DESCRIPTION OF DRAWINGS

[0049] 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 be obtained by those skilled in the art without creative labor on the basis of the drawings.

[0050] FIG. 1 is a schematic diagram of an electrode assembly according to an embodiment of the present application.

[0051] FIG. 2 is an exploded view of the battery cell shown in FIG. 1 according to an embodiment of the present application.

[0052] FIG. 3 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0053] FIG. 4 is an exploded view of the battery pack shown in FIG. 3 according to an embodiment of the present application.

[0054] FIG. 5 is a schematic diagram of a power consumption device using the battery cell as a power supply according to an embodiment of the present application.

[0055] In the drawings, the drawings are not drawn according to the actual scale.

[0056] Explanation of reference signs:

[0057] 1 battery pack; 2 upper box body; 3 lower box body; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0058] The embodiments of the present application will be further described in detail below in combination with 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 embodiments.

[0059] Hereinafter, specific embodiments of the battery cell, the battery device, and the electric device of the present application will be described in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known well, repeated description of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to sufficiently understand the present application, and are not intended to limit the subject matter recited in the claims.

[0060] The ranges disclosed herein are defined by their lower and upper limits. Ranges that include both a lower limit and an upper limit are defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the range. Ranges that include only one of a lower or an upper limit are also defined by a lower or an upper limit. Ranges that include only one of a lower or an upper limit are also defined to have a value of 0 as the unselected limit. For example, a range of 60-120 and a range of 80-110 are understood to be a range of 60-110 and a range of 80-120, respectively. Furthermore, a range of 1-2 and a range of 3-5 are understood to be a range of 1-3, a range of 1-4, a range of 1-5, a range of 2-3, a range of 2-4, and a range of 2-5, respectively. In the present application, unless otherwise stated, a numerical range "a-b" indicates a shorthand manner of presenting all real combinations of "a-b", where "a" and "b" are both real numbers. For example, a numerical range "0-5" indicates that all real numbers between "0-5" have been presented herein, and "0-5" is merely a shorthand manner of presenting these numerical combinations. In addition, when a parameter is stated to be an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.

[0061] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0062] Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0063] Unless otherwise specified, all steps of the present application can be performed in sequence or randomly, and preferably in sequence. 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 also comprises 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.

[0064] Unless otherwise specified, the terms "comprising" and "including" as used in this application are open-ended. For example, "comprising" and "including" may mean that other components not listed may also be included or contained.

[0065] Unless otherwise specified, the term "or" is inclusive in this application. For example, any of the following conditions satisfies 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 both A and B are true (or exist).

[0066] As analyzed in the background section, with the increase of manganese content in lithium manganese iron phosphate, although the energy density of the battery cell is improved, its cycle performance deteriorates. In order to improve the energy density output of the battery cell while maintaining high cycle performance, this application provides a battery cell, a battery device, and an electrical device.

[0067] [Battery cell]

[0068] The first embodiment of this application provides a battery cell comprising an electrode assembly, which includes a positive electrode, a negative electrode, and a separator between the positive and negative electrode. The negative electrode includes a negative current collector and a negative active layer disposed on at least one side of the negative current collector, the negative active layer comprising a negative electrode material, the negative electrode material being a carbon material. The positive electrode includes a positive current collector and a positive active layer disposed on at least one side of the positive current collector, the positive active layer comprising a positive electrode material, the positive electrode material comprising a nickel-containing lithium transition metal oxide and a lithium-containing phosphate-based positive electrode material. The nickel-containing lithium transition metal oxide, based on the total molar amount of metal elements other than lithium, has a Ni molar content greater than or equal to 50%; the lithium-containing phosphate-based positive electrode material, based on the total molar amount of metal elements other than lithium, has a Mn molar content of 50%-90%, and the areal density of the positive active layer is 190 mg / 1540.25 mm². 2 -380mg / 1540.25mm 2 .

[0069] During battery charging and discharging, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrode plates. A separator is placed between the positive and negative electrode plates, primarily to prevent short circuits between the positive and negative electrodes, while simultaneously allowing active ions to pass through.

[0070] The addition of lithium-containing phosphate-based cathode materials makes the cathode materials less expensive than pure systems containing nickel-containing lithium transition metal oxides.

[0071] The molar content of Ni element in the lithium-containing transition metal oxide is greater than or equal to 50%, which is a high-nickel-content lithium-containing transition metal oxide, has a high gram capacity, and thus can provide a high energy density for the battery cell; the molar content of Mn element in the lithium-containing phosphate-based positive electrode material is 50%-90%, which is a high-manganese-content lithium manganese iron phosphate, has a high platform voltage, and thus can provide a high energy density for the battery cell, and the positive electrode active layer is provided with a high surface density of 190 mg / 1540.25 mm 2 -380 mg / 1540.25 mm 2 so that the battery cell with the above positive electrode material has a high energy density output.

[0072] At the same time, considering that when the surface density is too large, the positive electrode active layer including the mixed positive electrode material is difficult to be compacted to the surface of the current collector due to the limitation of the processing technology, leading to serious powder falling of the pole piece, increasing the difficulty of the preparation process of the battery cell, and thus it is difficult to realize the production of the battery cell with high energy density, therefore, the energy density is controlled to be less than 380 mg / 1540.25 mm 2 below.

[0073] In addition, when the content of Mn element in the lithium-containing phosphate-based positive electrode material is too high, the gram capacity of the lithium-containing phosphate-based positive electrode material is too low, which limits the improvement of the energy density of the battery cell, therefore, the content of the above Mn element in the lithium-containing phosphate-based positive electrode material is controlled to be less than 90%.

[0074] In some embodiments, the elements in the positive electrode material can be determined by the following method:

[0075] For the positive electrode pole piece of the battery cell, the positive electrode pole piece is washed with DMC (dimethyl carbonate) to collect the positive electrode material in the positive electrode active layer after the positive electrode pole piece is dried and calcined. The positive electrode material is tested by inductively coupled plasma atomic emission spectrometry (ICP-OES).

[0076] In some embodiments, the content of the elements in the positive electrode material can be comprehensively determined by XRD, SEM-EDS, TEM-EDX, ICP-OES or other detection methods.

[0077] In some embodiments, the surface density is tested by the following method:

[0078] Take the single-sided coated positive electrode sheet (if it is a double-sided coated electrode sheet, the positive active 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, and measure its thickness H1. Then wipe off the positive active layer of the above weighed positive electrode sheet, weigh the positive current collector, and record it as M0, and measure its thickness H0. The single-sided coating weight of the positive active layer (i.e. the area density) = (the weight of the positive electrode sheet M1 - the weight of the positive current collector M0) / S1.

[0079] In some embodiments, if a positive conductive layer is provided between the positive active layer and the positive current collector, the mass of the positive conductive layer can be negligible when testing the compaction density or area density of the positive active layer, because the mass of the positive conductive layer is significantly lower than the mass of the positive active layer. The same applies to the negative active layer compaction density or area density test.

[0080] In some embodiments of the present application, the area density of the positive active layer is 200 mg / 1540.25 mm 2 - 350 mg / 1540.25 mm 2 , thereby more stably improving the high energy density output performance of the battery cell.

[0081] In some embodiments of the present application, in order to fully exert the respective advantages of the nickel-containing lithium transition metal oxide and the lithium-containing phosphate-based positive electrode material, the mass ratio of Fe element to Ni element in the positive electrode material is optionally in the range of (0.4-10):1. Under the mixed ratio of the nickel-containing lithium transition metal oxide and the lithium-containing phosphate-based positive electrode material corresponding to the above-mentioned molar ratio of Fe element to Ni element, the cycle stability and energy density of the battery cell are more fully improved, and the cost is more effectively controlled.

[0082] As the content of Ni element increases, the gram capacity of the nickel-containing lithium transition metal oxide increases, and in some embodiments, the molar content of Ni element in the nickel-containing lithium transition metal oxide is 70%-95%, optionally 80%-95%, based on the total molar amount of other metal elements in the nickel-containing lithium transition metal oxide excluding lithium element. The use of high-nickel-content nickel-containing lithium transition metal oxide can further improve the gram capacity of the positive electrode material, and thus further improve the energy density of the battery cell.

[0083] In some embodiments, the mole content of Mn element in the lithium-containing phosphate-based positive electrode material is 50%-70%, and further optionally 50%-60%, based on the total mole amount of other metal elements in the lithium-containing phosphate-based positive electrode material except for lithium element. Within the above range, as the Mn content increases, the gravimetric capacity of the lithium-containing phosphate-based positive electrode material decreases, but the platform voltage of the battery cell can be improved, and thus the mass energy density of the battery cell can also be improved. Moreover, by controlling the content of Mn within the above range, the excessive influence of excessive Mn content on the conductivity of the positive electrode material and the manganese elution are controlled, and thus the excessive negative influence on the rate performance and cycle performance of the battery cell is controlled.

[0084] 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 volumetric energy density of the battery cell. Generally, the larger the compaction density, the smaller the pores between the positive electrode material particles, the worse the electrolyte infiltration therein, and the smaller the buffer space reserved for the expansion of the positive electrode material, thus affecting the charge performance and cycle performance of the battery cell, but improving the volumetric energy density of the battery cell. The smaller the compaction density, the larger the pores between the positive electrode material particles, the better the electrolyte infiltration therein, and the larger the buffer space reserved for the expansion of the positive electrode material, thus improving the charge performance and cycle performance of the battery cell, but leading to a decrease in the volumetric energy density of the battery cell. In some embodiments, the compaction density of the positive electrode active layer corresponding to the battery cell when in a 100% SOC state is 2.32 g / cm 3 -3.18 g / cm 3 or 2.53 g / cm 3 -2.84 g / cm 3 . Thus, the comprehensive performance of energy density, charge performance, and cycle performance is improved.

[0085] The above "100% SOC state" refers to the state after the battery cell is charged to a voltage of 4.2 V at 25°C and a rate of 0.33 C, and then constant-voltage charged to a current less than 0.05 C.

[0086] The test method of the compaction density of the positive electrode active layer can be implemented according to the following method:

[0087] On the basis of the above 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-side coating weight of the positive electrode active layer / the thickness of the single-side positive electrode active layer.

[0088] In some embodiments, if an electrically conductive layer is provided between the positive active layer and the positive current collector, the mass of the electrically conductive layer can be ignored when testing the compaction density or the area density of the positive active layer, because the mass of the electrically conductive layer is significantly lower than the mass of the positive active layer. The same applies to the testing of the compaction density or the area density of the negative active layer.

[0089] In some embodiments, the powder compaction density of the positive electrode material is ≥ 2.5 g / cm3 under 30000 N. 3 , optionally 2.5 g / cm3 3 - 2.8 g / cm3 3 To provide a material basis for achieving as large an active layer compaction density as possible.

[0090] The nickel-containing lithium transition metal oxide used in the present application can be selected from conventional positive electrode materials of this type, such as one or more of lithium-containing nickel cobalt manganese oxides, lithium-containing nickel cobalt aluminum oxides.

[0091] In some embodiments, the nickel-containing lithium transition metal oxide comprises a lithium-containing nickel cobalt manganese oxide, and the lithium-containing nickel cobalt manganese oxide contains one or more of Zr, Al, B, Fe, Ca, Sr, Ti, V, or Y elements. The elements in the above modified materials can exist in the nickel-containing lithium transition metal oxide in the form of doping or coating.

[0092] With the use of some of the above elements, the lithium interlayer spacing is widened, the transport of lithium ions is promoted; or the migration of nickel ions to the lithium layer is inhibited, the cationic disorder is reduced, and the structural stability is maintained; or the bond between transition metal and oxygen is strengthened, the harmful phase change during the cycle is inhibited, and the release of structural oxygen is inhibited. In some embodiments, the nickel-containing lithium transition metal oxide comprises a lithium-containing nickel cobalt manganese oxide containing one or more of Zr, Al, B, or Fe elements.

[0093] In order to fully exert the effects of the elements, in some embodiments, in the lithium-containing nickel cobalt manganese oxide, the mass content of the elements satisfies at least one of the following: the content of Zr is 1000-3000 ppm, the content of Al is 100-1000 ppm, and the content of B is 50-300 ppm.

[0094] The lithium-containing phosphate-based positive electrode material used in the present application can use any of the conventional materials of this type, such as lithium iron manganese phosphate containing one or more of Al, B, Ca, Cr, Cu, K, Mg, Na, P, Si, Ti, V, or Zn elements. The elements in the above modified materials can exist in the lithium-containing phosphate-based positive electrode material in the form of doping or coating.

[0095] In some embodiments, the lithium-containing phosphate-based positive electrode material includes one or more of Al, Ca, Na, Ti, or V elements. The Al element can reduce the resistivity of the material, change the crystal structure, shorten the lithium ion transmission path, and 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 cell. The Na element and the V element can improve the electrical conductivity and cycle stability of the material. The Ti element can change the crystal structure and improve the charge and discharge performance of the material.

[0096] To fully exert the effects of the elements, in the lithium-containing phosphate-based positive electrode material, the mass content of the elements satisfies at least one of the following conditions: the content of Al is 100-1000 ppm, the content of Ca is 50-300 ppm, the content of Na is 50-300 ppm, the content of Ti is 100-1000 ppm, and the content of V is 1000-3000 ppm.

[0097] In some embodiments, the lithium-containing phosphate-based positive electrode material includes one or more of Al, Ca, Na, Ti, V, Zr, B, or Fe elements, and in the positive electrode material, the mass content of each element satisfies:

[0098] 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%.

[0099] To improve the electrical 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%.

[0100] In some embodiments, the specific capacity of the positive electrode material is improved by the size grading of the material particles in the positive electrode 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.

[0101] 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 fill in the gap of the large particle size, thus the compaction of the positive electrode material can be improved; and this combination mode protects the lithium-containing phosphate-based positive electrode material, effectively reducing the breaking probability when the lithium-containing phosphate-based positive electrode material is cold-pressed under the same pressure.

[0102] In some embodiments, the particles of the nickel-containing lithium transition metal oxide are polycrystalline particles in spherical or spheroidal shape, and the particles of the lithium-containing phosphate-based positive electrode material are single-crystal particles. The specific capacity of the nickel-containing lithium transition metal oxide in polycrystalline form is higher, thus the energy density of the battery cell can be better improved.

[0103] In some embodiments, the particles of the nickel-containing lithium transition metal oxide are single-crystal particles, and the particles of the lithium-containing phosphate-based positive electrode material are single-crystal particles. The structure of the nickel-containing lithium transition metal oxide in single-crystal form is more stable, thus the cycle performance of the battery cell can be better improved.

[0104] In order to further improve the specific capacity of the nickel-containing lithium transition metal oxide, in some embodiments, the volume particle size Dv50 of the single-crystal particles of the nickel-containing lithium transition metal oxide is 1 μm-5 μm, which can be selected as 1.5 μm-3 μm.

[0105] In order to further improve the specific capacity of the nickel-containing lithium transition metal oxide, in some embodiments, the volume particle size Dv50 of the polycrystalline particles of the nickel-containing lithium transition metal oxide is selected as 7 μm-12 μm.

[0106] In order to further improve the specific capacity of the lithium-containing phosphate-based positive electrode material, in some embodiments, the volume particle size Dv50 of the lithium-containing phosphate-based positive electrode material is 0.1 μm-15 μm, or 0.5 μm-2 μm.

[0107] In order to improve the rate performance of the battery cell, in some embodiments, the positive electrode sheet further comprises a positive electrode conductive layer, and the positive electrode 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 positive electrode conductive layer, thereby improving the rate performance of the battery cell.

[0108] 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 positive electrode conductive layer comprises a positive electrode binder and a positive electrode conductive material.

[0109] In some embodiments, the thickness of the positive electrode conductive layer is 1 μm-2 μm. Thus, the purpose of improving the conductivity can be fully achieved by using the positive electrode conductive layer, and the energy density of the battery cell is not affected by the too large thickness of the conductive layer.

[0110] The strength of the positive electrode current collector is related to its thickness, generally the greater the thickness, the greater the strength, but the greater the strength, the worse the ductility, and also leads to the battery cell energy density to decline. The positive electrode material expands during the charge and discharge cycle, so the positive electrode current collector needs to have a certain strength to bind the expansion, while also having 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 impact on the energy density, and it 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 the charging process. At the same time, due to the increase in the thickness of the positive electrode current collector, the resistance of the metal parts in the cell increases, which also leads to the increase of the battery cell discharge DCR, that is, the increase of the internal resistance of the battery cell.

[0111] 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.).

[0112] 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.

[0113] 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.

[0114] 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.

[0115] [Negative electrode sheet]

[0116] The areal density of the negative active layer is designed to vary with the areal density of the positive active layer according to the CB value of the battery cell, and the CB value is generally set to be between 1.04 and 1.20, and in some embodiments, in order to fully exert the capacity of the positive electrode material, the areal density of the negative active layer is 95 mg / 1540.25 mm 2 -180 mg / 1540.25 mm 2 ; optionally 130 mg / 1540.25 mm 2 -150 mg / 1540.25 mm 2 . Thus, a better match is formed with the areal density of the positive active layer of the positive electrode sheet, and the capacity of the positive and negative electrode materials is fully exerted.

[0117] When the battery cell is charged, the negative electrode material expands, causing the compaction density of the negative active layer to decrease, and in some embodiments, the compaction density of the negative active layer corresponding to the battery cell when it is in a 100% SOC state is 1.04 g / cm 3 -1.48 g / cm 3 ; optionally 1.23 g / cm 3 -1.38 g / cm 3 . The negative electrode sheet with the above compaction density has small expansion deformation and good electrolyte infiltration, thus improving the cycle performance of the battery cell.

[0118] In some embodiments, the above-mentioned carbon material includes composite graphite particles, and the composite graphite particles include: a body particle and a coating layer, the body particle includes primary particles or secondary particles, and the body particle includes artificial graphite; the coating layer is coated on the surface of the body particle, and the coating layer includes amorphous carbon. The artificial graphite coated with amorphous carbon has a simple structure and high electrical conductivity.

[0119] On the basis of improving the electrical 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 amorphous carbon in the coating layer is 2% to 5% based on the total mass of the composite graphite particles.

[0120] 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 -1.7 g / cm 3 , or 1.55 g / cm 3 -1.65 g / cm 3 .

[0121] In some embodiments, the negative active layer comprises: 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 first negative active layer comprises one or more of the composite graphite particles and the natural graphite, optionally the volume average particle size Dv50 of the negative active material in the first negative active layer is 7.5-19.5 μm, optionally 12.5-18.5 μm; the second negative active layer is disposed on the side of the first negative active layer away from the negative current collector, the second negative active layer comprises the composite graphite particles, optionally the volume average particle size Dv50 of the negative active material in the second negative active layer is 7.5-19.5 μm, optionally 7.5-15.5 μm. 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.

[0122] In some embodiments, the negative electrode sheet further comprises a negative conductive layer, the negative conductive layer is disposed between the negative current collector and the negative active layer, the negative conductive layer comprises a negative binder and a negative conductive material, the thickness of the negative conductive layer is 0.5-3 μm, or 1-2 μm. The negative conductive primer layer is used to improve the conductivity of the negative electrode sheet, and further improve the rate performance of the battery cell.

[0123] As the above-mentioned considerations for the thickness of the positive current collector, in some embodiments, the thickness of the negative current collector is 4-7 μm, optionally 4-5 μm. The negative current collector with the thickness in the range has less impact 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.

[0124] In some embodiments, the negative current collector can adopt a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be adopted. The composite current collector can comprise a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material. 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 material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0125] In some embodiments, the negative active layer can further optionally comprise 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).

[0126] In some embodiments, the negative active layer can also optionally include 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.

[0127] In some embodiments, the negative active layer can also optionally include other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

[0128] 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 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, the negative electrode sheet can be obtained.

[0129] [Separator]

[0130] 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.

[0131] 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.

[0132] In some embodiments, the separator includes a porous base film and a functional layer disposed on at least one side of the porous base film. That is, the separator is a composite film. The corresponding functional layer is selected according to different functional needs, which will not be described herein.

[0133] [Electrolyte]

[0134] 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.

[0135] In some embodiments, the above-mentioned battery cell further includes an electrolyte, and the electrolyte includes an electrolyte salt and a solvent.

[0136] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorobisoxalate phosphate.

[0137] 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, butane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0138] 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.

[0139] In some embodiments, the electrolyte solution described above includes lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonylimide (LiFSI). The lithium bisfluorosulfonylimide 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.

[0140] In some embodiments, the molar concentration ratio of lithium bisfluorosulfonylimide to lithium hexafluorophosphate is (2-5): 10. Thus, on the basis of improving the cycle stability and charging rate of the battery cell using the lithium salt described above, the excessive increase in the cost of the battery cell is controlled.

[0141] In some embodiments, the battery cell includes a housing, the electrode assembly is disposed in an inner cavity of the housing, the positive electrode sheet and the negative electrode sheet are disposed in a stacked manner, the length of the housing is L1, the length of the positive electrode sheet is L2, and L2 / L1 is 80%-99%, optionally 88%-99%. Thus, the volumetric energy density of the battery cell is further improved.

[0142] In some embodiments, the size of the housing has one or more of the following characteristics:

[0143] L1 is in the range of 300 mm-950 mm;

[0144] The height of the housing is 85 mm-140 mm;

[0145] The thickness of the housing is 10 mm-20 mm.

[0146] 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 pouch-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.

[0147] In some embodiments, the shell is an aluminum shell or a steel shell.

[0148] In some embodiments, the battery cell has a liquid injection coefficient of 1.9 g / Ah-3.1 g / Ah.

[0149] In some embodiments, the battery cell has a volumetric energy density of 470 Wh / L-570 Wh / L.

[0150] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator film can be formed into an electrode assembly through a winding process or a stacking process.

[0151] The battery cell can have a square shape or any other shape. For example, FIG. 1 is an electrode assembly 52 of a battery cell 5 having a square structure as an example.

[0152] 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, and the bottom plate and the side plate can form an accommodation cavity. The shell 51 has an opening communicating with the accommodation cavity, and the top cover assembly 53 can be arranged on the opening to close the accommodation cavity. The positive electrode sheet, the negative electrode sheet, and the separator film can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the accommodation 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, and a person skilled in the art can select according to the specific actual needs.

[0153] 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, and a person skilled in the art can select according to the application and capacity of the battery module.

[0154] In the battery module, a plurality of battery cells can be arranged in sequence along the thickness direction of the battery module. Of course, other arrangements can also be used. Further, the plurality of battery cells can be fixed by fasteners.

[0155] Optionally, the battery module can further include a housing having an accommodation space, and the plurality of battery cells are accommodated in the accommodation space.

[0156] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and a person skilled in the art can select according to the application and capacity of the battery pack.

[0157] 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.

[0158] In addition, the application also provides a power utilization device, which comprises the battery cell provided by the application. The battery cell 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.

[0159] As the power utilization device, the battery cell, the battery module or the battery pack can be selected according to the use requirement thereof.

[0160] 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 requirement of high power and high energy density of the battery cell of the power utilization device, the battery pack or the battery module can be used.

[0161] [Embodiment]

[0162] Hereinafter, the embodiments of the application will be described. The embodiments described below are exemplary and are only used to explain the application, and cannot be understood as a limitation of the application. If the specific technology or condition is not indicated in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument is not indicated by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0163] Embodiment 1

[0164] Positive electrode tab

[0165] The positive active layer includes positive active material, binder polyvinylidene fluoride, and conductive agent acetylene black (mass ratio of 96.7:2.3:1). In the positive active material, the mass ratio of lithium transition metal oxide containing nickel and lithium-containing phosphate-based positive material is 4:6, and the mass content of carbon in the lithium-containing phosphate-based positive material is about 1.7%. In the lithium transition metal oxide containing nickel, the subscripts of Ni, Co, and Mn in the chemical formula are the integral data, and the content of element M other than lithium and oxygen is trace compared with the content of Ni, Co, and Mn, so these elements and their atomic numbers are not reflected in the chemical formula, but it does not mean that element M has no effect on the battery performance. In the positive material, the mass content of Al element is 0.063%, the mass content of B is 0.0039%, and the mass content of Zr is 0.256%. The thickness of the current collector aluminum foil is 12 μm, and the positive active layer is located on both sides of the aluminum foil. There is a positive conductive layer between the positive active layer and the aluminum foil. The positive conductive layer includes a film layer formed by uniformly mixing the positive conductive agent super-conductive carbon, the positive binder polyacrylate, and the solvent and then coating on the surface of the positive current collector and drying. The thickness of the film layer is 1 μm. The mass content of the positive conductive agent in the positive conductive layer is 50%, and the mass content of the positive binder in the positive conductive layer is 50%. The length of the positive electrode sheet is 592 mm.

[0166] The negative electrode sheet

[0167] The negative active layer includes 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, and the mass content of the carbon coating layer is 3.5%) and natural graphite in a mass ratio of 5:5. The Dv50 of the composite graphite particles is 17 μm, and the Dv50 of the natural graphite is 18 μm. The negative active material in the upper layer is composite graphite particles, and the Dv50 is 10 μm. The powder compaction density of the composite graphite material in the negative active layer of the above-mentioned negative electrode sheet is 1.6 g / cm 3 .

[0168] The negative current collector is a copper foil with a thickness of 5 μm. There is a negative conductive layer between the copper foil and the lower active layer. The conductive layer is a film layer formed by uniformly mixing the negative conductive agent super-conductive carbon, the negative binder styrene butadiene rubber SBR, the thickening agent sodium carboxymethyl cellulose (CMC-Na), and the solvent water, coating on the surface of the negative current collector, and drying. The thickness of the film layer 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%. The compaction density of the negative active layer is 1.32 g / cm under the following test conditions.3 .

[0169] The electrolyte comprises the organic solvents ethyl acetate (EA), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) (mass ratio 50:35:15), 0.9 mol / L lithium hexafluorophosphate (LiPF6) and 0.3 mol / L lithium bis(fluorosulfonyl)imide (LiFSI) as lithium salts, 2.5% vinylene carbonate (VC), 1% fluoroethylene carbonate (FEC), 0.5% 1,3-propylene sulfonate lactone (PS), 0.5% vinyl sulfite (DTD), and 0.5% lithium difluorophosphate (LiPO2F2). The electrolyte has a conductivity of 11 mS / cm.

[0170] Separating membrane

[0171] A polyethylene (PE) film coated with a nano-alumina layer is used as the isolation membrane.

[0172] battery cell

[0173] The electrode assembly consists of stacked positive electrode sheets, separator, and negative electrode sheets. The electrode assembly is then placed into a square aluminum casing (600mm long, 19mm thick, and 105mm high), dried, and filled with electrolyte at an injection coefficient of 2.9. Following encapsulation, high-temperature settling, formation, secondary electrolyte injection, aging, and capacity testing, a single battery cell is obtained.

[0174] Electrode Testing

[0175] Compaction of the positive electrode active layer

[0176] The degree refers to the compaction density of the positive electrode active layer after charging a single cell to 4.2V at 25℃ and a rate of 0.33C, and then charging it at a constant voltage until the current is less than 0.05C.

[0177] Test methods for areal density and compacted density:

[0178] Take a single-sided coated positive electrode sheet (if it is a double-sided coated electrode sheet, the positive active layer on one side can be wiped off first), cut it into a small circular sheet with an area of ​​S1, weigh it and record its weight as M1, and measure its thickness H1. Then wipe off the positive active layer of the weighed positive electrode sheet, weigh the positive current collector and record it as M0, and measure its thickness H0. The single-sided coating weight of the positive active layer (i.e., the areal density) = (weight of the positive electrode sheet M1 - weight of the positive current collector M0) / S1, the thickness of the positive active layer = the thickness of the single-sided positive electrode sheet H1 - the thickness of the positive current collector H0, and the compaction density of the positive active layer = the single-sided coating weight of the positive active layer / the thickness of the single-sided positive active layer.

[0179] Battery cell testing

[0180] Volume energy density test method:

[0181] Place the battery monomer at 25℃, charge it to 4.2V at a constant current of 0.33C, and then charge it to 0.05C at a constant voltage. Discharge it to 2.5V at a constant current of 0.33C to obtain the discharge energy A0 at this time, unit: Wh. Measure the length, width and height of the battery monomer with a caliper (usually calculate the size of the battery shell, excluding the height of the electrode terminal, and excluding the insulation film outside the shell), calculate the volume V0 of the battery monomer, unit L. The volume energy density VED of the battery monomer is A0 / V0, unit Wh / L.

[0182] DC internal resistance DCR test of battery monomer

[0183] The method can be referred to in GB / T 31467 "HEV High Power Lithium Ion Power Battery Performance Test Specification". Specifically as follows:

[0184] At room temperature, charge the battery monomer to 4.2V at a constant current of 0.33C, stand for 1min, then charge it to 4.2V at a constant current of 0.1C, discharge it to 2.0V at a constant current of 0.33C, record the discharge capacity A0 at this time, unit Ah, then charge 0.5A0 Ah at a constant current of 0.33C, adjust the SOC to 50%.

[0185] After placing the battery monomer at 25℃ for 2h, discharge it at a constant 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,

[0186] Wherein, ΔU discharge represents the voltage change within 10s of discharging start, and ΔI discharge represents the current value within 10s of discharging start.

[0187] Cycle life test method:

[0188] Cycle number of battery monomer to 80% SOH:

[0189] At 45℃, charge the battery monomer to the charge cut-off voltage 4.2V at a constant current of 1C, and then discharge it to 2.0V at a constant current of 1C. This is one charge-discharge cycle. Repeat the above charge-discharge cycle steps until the cycle capacity retention rate (i.e. Cn / C0x100%) is 80% (the discharge capacity of 1C constant current discharge to 2.0V is recorded as C0, and Cn is the discharge capacity of the nth cycle). Record the cycle number. The more the cycle number is, the better the cycle performance of the battery monomer is.

[0190] Example 2, Example 3, Comparative Examples 1 to 3 adjust the composition or areal density of the positive electrode material on the basis of Example 1, and other parameters remain the same as in Example 1. In Example 2, the mass content of other elements M in the positive electrode material in the positive electrode active layer is Al 0.060%, B 0.0050%, and Zr 0.249%; in Example 3, the mass content of other elements is Al 0.060%, B 0.0043%, and Zr 0.257%. The specific adjustments are shown in Table 1 below, and the volume energy density test results of each example and comparative example are recorded in Table 1.

[0191] Table 1

[0192] From the comparison of the above examples and comparative examples, it can be seen that when the molar content of Ni element in the lithium transition metal oxide containing nickel is less than 50% relative to the transition metal elements, or the molar content of Mn element in the lithium-containing phosphate-based positive electrode material is less than 50% or greater than 90% relative to the transition metal elements, or the areal density of the positive electrode active layer is too small, the energy density of the battery cell will decrease significantly.

[0193] The following investigates the effect of the change in the content of Mn element in the lithium-containing phosphate-based positive electrode material on the energy density and cycle performance of the battery cell.

[0194] The lithium transition metal oxide containing nickel used in Examples 4 to 7 is the same as in Example 2, the areal density of the positive electrode active layer is the same as in Example 2, the mass ratio of the lithium transition metal oxide containing nickel and the lithium-containing phosphate-based positive electrode material is 4:6, the negative electrode sheet, electrolyte, and separator film are the same as in Example 2. The remaining variable settings are recorded in Table 2.

[0195] Table 2

[0196] From the comparison of the data in Table 2, it can be seen that as the content of Mn element in the lithium-containing phosphate-based positive electrode material increases, the volume energy density and cycle number of the battery cell both deteriorate, and especially when the molar ratio of Mn element and iron element is greater than 7:3, the deterioration of energy density and cycle number is obvious. Therefore, controlling the content of Mn element in the lithium-containing phosphate-based positive electrode material is beneficial to maintaining the high energy density and high cycle performance of the battery cell.

[0197] The following investigates the effect of the ratio of the lithium transition metal oxide containing nickel and the lithium-containing phosphate-based positive electrode material on the energy density and cycle performance of the battery cell.

[0198] The lithium transition metal oxide containing nickel and the lithium-containing phosphate-based positive electrode material used in Examples 8 to 11 are the same as in Example 2, and the area density of the positive electrode active layer is also the same as in Example 2, but the mass ratio of the lithium transition metal oxide containing nickel and the lithium-containing phosphate-based positive electrode material is adjusted according to Table 3 to further adjust the elemental mass ratio of Fe and Ni in the positive electrode material, and the negative electrode sheet, electrolyte and separator are the same as in Example 2. The remaining variables are recorded in Table 3.

[0199] Table 3

[0200] As can be seen from the data in Table 3, as the content of the lithium-containing phosphate-based positive electrode material increases, the energy density of the battery cell decreases, but the cycle performance is improved.

[0201] The following examines the effect of the area density of the positive electrode active layer on the energy density of the battery cell. Based on Example 2, the area density of the positive electrode active layer is adjusted as described in Table 4, and the area density of the negative electrode active layer is adjusted to adapt to the same CB value for each example. The test results are recorded in Table 4

[0202] Table 4

[0203] As can be seen from the data in Table 4, the increase in the area density of the positive electrode is beneficial to improve the energy density of the battery cell.

[0204] The following examines the effect of the change in the compaction density of the positive electrode active layer corresponding to the battery cell configured at 100% SOC on the volumetric energy density and cycle performance of the battery cell. Based on Example 2, the pressure conditions during preparation of the positive electrode active layer are adjusted to obtain the compaction shown in Table 5, and the test results are also recorded in Table 5.

[0205] Table 5

[0206] As can be seen from the data in Table 5, as the compaction density increases, the volumetric energy density of the battery cell increases, but also causes a decrease in cycle performance.

[0207] The following examines the effect of the change in the compaction density of the negative electrode active layer corresponding to the battery cell configured at 100% SOC on the volumetric energy density and cycle performance of the battery cell. Based on Example 2, the pressure conditions during preparation of the negative electrode active layer are adjusted to obtain the compaction shown in Table 6, and the test results are also recorded in Table 6.

[0208] Table 6

[0209] As can be seen from the data in Table 6, the volumetric energy density of the battery cell increases with the increase of the compaction density, but also leads to the decrease of the cycle performance.

[0210] The following considers the effects of the positive electrode tab thickness and the negative electrode tab thickness on the battery energy density and the DCR internal resistance. On the basis of Embodiment 2, the positive electrode tab thickness or the negative electrode tab thickness is adjusted, and the rest remains unchanged, and the test results are recorded in Table 7.

[0211] Table 7

[0212] As can be seen from the data in Table 7, with the increase of the positive current collector thickness or the negative current collector thickness, the energy density of the battery cell decreases, the cycle performance is improved, but the discharge DCR increases significantly, which indicates that the increase of the current collector thickness leads to the increase of the resistance of the metal structural part in the battery cell, causing the increase of the battery cell discharge DCR.

[0213] The following investigates the effects of the length of the positive electrode tab on the battery cell energy density. On the basis of Embodiment 2, the length of the positive electrode tab is adjusted as recorded in Table 8, and the test results are also recorded in Table 8.

[0214] Table 8

[0215] As can be seen from the data in Table 8, with the increase of the length of the positive electrode tab, the proportion of the positive electrode active layer that can play an energy role in the battery cell increases, thus improving the energy density of the battery cell.

[0216] 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 components can be substituted therefor. 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, The battery cell comprises an electrode assembly, the electrode assembly comprising a positive electrode tab, a negative electrode tab, and a separator film between the positive electrode tab and the negative electrode tab, wherein The negative electrode tab 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 tab 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 transition metal oxide containing nickel and a lithium-containing phosphate-based positive electrode material, wherein The molar content of Ni element in the lithium transition metal oxide containing nickel is greater than or equal to 50% in terms of the total molar amount of other metal elements in the lithium transition metal oxide containing nickel except lithium element; The molar content of Mn element in the lithium-containing phosphate-based positive electrode material is 50%-90% in terms of the total molar amount of other metal elements in the lithium-containing phosphate-based positive electrode material except lithium element, and The areal density of the positive electrode active layer is 190 mg / 1540.25 mm 2 - 380 mg / 1540.25 mm 2 .

2. The battery cell of claim 1, wherein, The face density of the positive electrode active layer is 200 mg / 1540.25 mm 2 - 350 mg / 1540.25 mm 2 .

3. The battery cell of claim 1 or 2, wherein, The mass ratio of Fe element to Ni element in the positive electrode material ranges from (0.4-10):

1.

4. The battery cell of any one of claims 1 to 3, wherein, The molar content of Ni element in the lithium transition metal oxide containing nickel is 70%-95%, optionally 80%-95% in terms of the total molar amount of other metal elements in the lithium transition metal oxide containing nickel except lithium element.

5. The battery cell of any one of claims 1 to 4, wherein, The molar content of Mn element in the lithium-containing phosphate-based positive electrode material is 50%-70% in terms of the total molar amount of other metal elements in the lithium-containing phosphate-based positive electrode material except lithium element.

6. The battery cell of any one of claims 1 to 5, wherein, The battery cell is configured such that the compaction density of the positive electrode active layer corresponding to the battery cell at 100% SOC is 2.32 g / cm 3 - 3.18 g / cm 3 , optionally 2.53 g / cm 3 - 2.84 g / cm 3 .

7. The battery cell of any one of claims 1 to 6, wherein, The positive electrode material has a powder compaction density ≥ 2.5 g / cm under 30000 N 3 , optionally 2.5 g / cm 3 - 2.8 g / cm 3 .

8. The battery cell of any one of claims 1 to 7, wherein, The lithium transition metal oxide containing nickel comprises a lithium-containing nickel cobalt manganese oxide containing one or more of Zr, Al, B, Fe, Ca, Sr, Ti, V or Y elements.

9. The battery cell of claim 8, wherein, The lithium-containing nickel cobalt manganese oxide contains one or more of Zr, Al, B or Fe elements; optionally, in the lithium-containing nickel cobalt manganese oxide, the element mass content satisfies at least one of: the content of Zr is 1000-3000 ppm, the content of Al is 100-1000 ppm, and the content of B is 50-300 ppm.

10. The battery cell of any one of claims 1-9, wherein, The lithium-containing phosphate-based positive electrode material comprises a lithium manganese iron phosphate containing one or more of Al, B, Ca, Cr, Cu, K, Mg, Na, P, Si, Ti, V or Zn elements.

11. The battery cell of claim 10, wherein, The lithium manganese iron phosphate contains one or more of Al, Ca, Na, Ti or V elements; optionally, in the lithium manganese iron phosphate, the element mass content satisfies at least one of: the content of Al is 100-1000 ppm, the content of Ca is 50-300 ppm, the content of Na is 50-300 ppm, the content of Ti is 100-1000 ppm, and the content of V is 1000-3000 ppm.

12. The battery cell of any one of claims 1-11, wherein, The positive electrode material includes lithium manganese iron phosphate and nickel cobalt manganese oxide, the positive electrode material includes one or more of Al, B, Ca, Fe, Sr, Ti, V, Y or Zn elements, and in the positive electrode material, 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%.

13. The battery cell of any one of claims 1-12, 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%.

14. The battery cell of any one of claims 1-13, wherein, In the positive electrode material, The mass content of Fe elements in particles with a particle size less than or equal to Dv10 is M1, the mass content of Fe elements in particles with a particle size greater than or equal to Dv90 is M2, M1 is greater than M2; and / or The mass content of Ni elements in particles with a particle size less than or equal to Dv10 is M3, the mass content of Ni elements in particles with a particle size greater than or equal to Dv90 is M4, M3 is less than M4.

15. The battery cell of any one of claims 1-14, wherein, The particles of the nickel-containing lithium transition metal oxide are spherical or spheroidal polycrystalline particles, and the particles of the lithium-containing phosphate-based positive electrode material are single-crystal particles.

16. The battery cell of any one of claims 1-14, wherein, The particles of the nickel-containing lithium transition metal oxide are single-crystal particles, and the particles of the lithium-containing phosphate-based positive electrode material are single-crystal particles.

17. The battery cell of claim 15, wherein, The volume particle size Dv50 of the polycrystalline particles of the nickel-containing lithium transition metal oxide is 7 μm-12 μm.

18. The battery cell of claim 16, wherein, The volume particle size Dv50 of the single-crystal particles of the nickel-containing lithium transition metal oxide is 1 μm-5 μm, which can be 1.5 μm-3 μm.

19. The battery cell of any one of claims 15-18, wherein, The volume particle size Dv50 of the single-crystal particles of the lithium-containing phosphate-based positive electrode material is 0.1 μm-15 μm, which can be 0.5 μm-2 μm.

20. The battery cell of any one of claims 1-19, wherein, The positive electrode tab includes a positive electrode conductive layer, and the positive electrode conductive layer is arranged between the positive electrode current collector and the positive electrode active layer.

21. The battery cell of claim 20, wherein, The positive electrode conductive layer includes a positive electrode binder and a positive electrode conductive material, and the thickness of the positive electrode conductive layer is 1 μm-2 μm.

22. The battery cell of any one of claims 1-21, wherein, The thickness of the positive electrode current collector is 9 μm-17 μm, which can be 10 μm-13 μm.

23. The battery cell of any one of claims 1-22, wherein, The areal density of the negative active layer is 95 mg / 1540.25 mm 2 - 180 mg / 1540.25 mm 2 ; optionally 130 mg / 1540.25 mm 2 - 150 mg / 1540.25 mm 2 .

24. The battery cell of any one of claims 1 to 23, configured to have a compacted density of the negative active layer corresponding to 1.04 g / cm3 when in a 100% SOC state. 3 -1.48 g / cm3. 3 ; optionally 1.23 g / cm3. 3 -1.38 g / cm3. 3 .

25. The battery cell of any one of claims 1-23, wherein, The carbon material includes composite graphite particles, and the composite graphite particles include: A bulk particle, the bulk particle includes secondary particles, and the bulk particle includes artificial graphite; and A coating layer, the coating layer is coated on the surface of the bulk particle, and the coating layer includes amorphous carbon.

26. The battery cell of claim 25, wherein, The mass content of amorphous carbon in the coating layer is 2%-5% based on the total mass of the composite graphite particles.

27. The battery cell of claim 25 or 26, wherein, The powder compaction density of the composite graphite particles is 1.5 g / cm 3 -1.7 g / cm 3 , or 1.55 g / cm 3 -1.65 g / cm 3 .

28. The battery cell of any one of claims 25-27, wherein, The negative electrode active layer includes: A first negative active layer disposed on one side of the negative current collector, the first negative active layer comprising one or more of composite graphite particles and natural graphite, optionally the volume average particle size Dv50 of the negative active material in the first negative active layer is 7.5-19.5 μm, optionally 12.5-18.5 μm, and A second negative active layer disposed on the side of the first negative active layer away from the negative current collector, the second negative active layer comprising composite graphite particles, optionally the volume average particle size Dv50 of the negative active material in the second negative active layer is 7.5-19.5 μm, optionally 7.5-15.5 μm.

29. The battery cell of any one of claims 1-28, wherein, The negative electrode sheet comprises a negative conductive layer disposed between the negative current collector and the negative active layer.

30. The battery cell of claim 29, wherein, The negative conductive layer comprises a negative binder and a negative conductive material, the thickness of the negative conductive layer is 1-2 μm.

31. The battery cell of any one of claims 1-30, wherein, The thickness of the negative current collector is 4-7 μm, optionally 4-5 μm.

32. The battery cell of any one of claims 1-31, wherein, The electrode assembly further comprises an electrolyte, the electrolyte comprising lithium hexafluorophosphate and lithium bisfluorosulfonylimide.

33. The battery cell of claim 32, wherein, The molar concentration ratio of the lithium bisfluorosulfonylimide to the lithium hexafluorophosphate is (2-5):

10.

34. The battery cell of claim 32 or 33, wherein, The conductivity of the electrolyte is 10-20 mS / cm, optionally 12-17 mS / cm.

35. The battery cell of any one of claims 1-34, wherein, The battery cell further comprises a housing, the electrode assembly is disposed in the inner cavity of the housing, the positive electrode sheet and the negative electrode sheet are disposed in a stacked manner, the length of the housing is L1, the length of the positive electrode sheet is L2, L2 / L1 is 80-99%, optionally 88-99%.

36. The battery cell of claim 35, wherein, The size of the housing has one or more of the following characteristics: The L1 is in the range of 300-950 mm; The height of the housing is 85-140 mm; The thickness of the housing is 10-20 mm.

37. The battery cell of claim 35 or 36, wherein, The housing is an aluminum housing or a steel housing.

38. The battery cell of any one of claims 1-37, wherein, The injection coefficient of the battery cell is 1.9-3.1 g / Ah.

39. The battery cell of claims 1-38, wherein, The volumetric energy density of the battery cell is 470-570 Wh / L.

40. A battery device comprising the battery cell of any one of claims 1-39, the battery device comprising a battery module, a battery pack, or an energy storage device.

41. An electric device comprising the battery cell of any one of claims 1-39, or the battery device of claim 40.

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