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. 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 active material. The positive electrode active material comprises a lithium iron manganese phosphate positive electrode material and a lithium-containing nickel cobalt manganese oxide positive electrode material. In the lithium-containing nickel cobalt manganese oxide positive electrode material, element Ni accounts for 50% to 95% of the total molar amount of three elements, i.e., Ni, Co and Mn. The proportion of the lithium-containing nickel cobalt manganese oxide positive electrode material in the positive electrode active material is 5%-95%. In the lithium iron manganese phosphate positive electrode material, element Mn accounts for 30% to 80% of the total molar amount of the element Mn and element Fe. The battery cell exhibits a discharge voltage plateau of 3.29 V to 4.15 V at room temperature and at a rate of 0.1 C.

Description

Battery cell, battery device and electric device Cross-reference to related applications

[0001] This application claims priority to Chinese Patent Application No. 202411087334.7, filed on August 8, 2024, entitled “Battery cell, battery device and electric device” and Chinese Patent Application No. 202411286585.8, filed on September 13, 2024, entitled “Battery cell, battery device and electric device”, the contents of which are incorporated herein by reference in their entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of batteries, in particular to a battery cell, a battery device and an electric device. BACKGROUND

[0003] With the popularity and development of electric vehicles, the performance requirements for battery cells are gradually increasing. Currently, not only is it necessary to have high energy density to reduce the range anxiety of users, but it is also necessary to have high cycle stability to improve the battery life and safety performance.

[0004] Lithium iron phosphate batteries are widely used in electric vehicles as power batteries due to their low cost. The lithium iron phosphate positive electrode material in the batteries has a significant cost advantage over ternary positive electrode materials. However, the energy density of the lithium iron phosphate positive electrode material is relatively low, and therefore it is necessary to improve the energy density of the battery system while maintaining the low cost advantage. SUMMARY

[0005] The present application provides a battery cell, a battery device and an electric device, which improves the energy density of the battery cell.

[0006] The first aspect of the present application provides a battery cell, comprising 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 arranged on at least one side of the negative electrode current collector, the negative electrode active layer comprising a negative electrode active material, the negative electrode active material comprising one or more of a carbon-based material and a silicon-based material, the positive electrode tab comprising 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 active material, the positive electrode active material comprising a lithium-containing lithium manganese iron phosphate positive electrode material and a lithium-containing nickel cobalt manganese oxide positive electrode material, in the lithium-containing nickel cobalt manganese oxide positive electrode material, the content of Ni element accounts for 50% to 95% of the total molar content of Ni, Co and Mn elements, and the content of the lithium-containing nickel cobalt manganese oxide positive electrode material in the positive electrode active material accounts for 5% to 95%, and the discharge voltage platform of the battery cell at room temperature and a rate of 0.1C is 3.29V to 4.15V.

[0007] The positive electrode active material of the battery cell of the present application comprises a lithium-containing lithium manganese iron phosphate positive electrode material and a lithium-containing nickel cobalt manganese oxide positive electrode material, wherein the content of Mn element in the lithium-containing lithium manganese iron phosphate positive electrode material is positively correlated with the voltage platform of the mixed positive electrode material, but is negatively correlated with the gram capacity of the lithium-containing lithium manganese iron phosphate positive electrode material, and is not conducive to the skeleton stability of the lithium-containing lithium manganese iron phosphate positive electrode material in long-term cycling; and the content of Ni element in the lithium-containing nickel cobalt manganese oxide positive electrode material is positively correlated with the voltage platform and the gram capacity of the mixed positive electrode material, but is not conducive to the skeleton stability of the lithium-containing nickel cobalt manganese oxide in long-term cycling.

[0008] Based on the actual needs of customers for low cost, high specific energy and long cycle, the present application finds that by making the content of Ni element in the lithium-containing nickel cobalt manganese oxide positive electrode material account for 50% to 95% of the total molar content of Ni, Co and Mn elements, and the content of the lithium-containing nickel cobalt manganese oxide positive electrode material in the positive electrode active material accounts for 5% to 95%, and further by making the content of Mn element in the lithium-containing lithium manganese iron phosphate positive electrode material account for 30% to 80% of the total molar content of Mn element and Fe element, the gram capacity of the mixed positive electrode material is better, and the voltage platform is kept in a suitable range, so that the battery cell has low cost, energy density and high cycle performance.

[0009] Meanwhile, the lithium manganese iron phosphate positive electrode material has an olivine structure, which is more stable than a layered structure of the lithium-containing nickel cobalt manganese oxide positive electrode material, and has low cost. The mixed positive electrode material battery cell using the lithium manganese iron phosphate positive electrode material and the lithium-containing nickel cobalt manganese oxide positive electrode material has improved cycle stability, safety and power performance compared with the battery cell using the pure lithium-containing nickel cobalt manganese oxide positive electrode material, and has greatly reduced cost compared with the lithium-containing nickel cobalt manganese oxide positive electrode material.

[0010] In any embodiment of the first aspect, the voltage plateau of the battery cell at room temperature and a rate of 0.1C is 3.67V-3.86V.

[0011] In any embodiment of the first aspect, in the lithium-containing nickel cobalt manganese oxide positive electrode material, the molar content of the Ni element relative to the total moles of nickel cobalt manganese elements is 80%-95%.

[0012] In any embodiment of the first aspect, in the lithium manganese iron phosphate positive electrode material, the molar content of the Mn element relative to the total moles of Mn element and Fe element is 50%-70%.

[0013] In any embodiment of the first aspect, the mass content of the lithium manganese iron phosphate positive electrode material is 50%-95%, and further optionally 50%-70%, based on the total mass of the positive electrode active material.

[0014] In any embodiment of the first aspect, the areal density of the positive electrode active layer is 200mg / 1540.25mm 2 -370mg / 1540.25mm 2 , and optionally 240mg / 1540.25mm 2 -340mg / 1540.25mm 2 .

[0015] In any embodiment of the first aspect, the areal capacity of the positive electrode tab is 50mAh / 1540.25mm 2 -350mAh / 1540.25mm 2 , and optionally 80mAh / 1540.25mm 2 -150mAh / 1540.25mm 2 .

[0016] In any embodiment of the first aspect, the compaction density of the corresponding positive electrode active layer in the battery cell at 100% SOC state is 2.45g / cm 3 -3.4g / cm 3 , and optionally 2.5g / cm 3 -3.2g / cm 3 .

[0017] In any embodiment of the first aspect, the positive electrode active material has a powder compaction density ≥ 2.43 g / cm3 at 30000 N 3 , optionally ≥ 2.45 g / cm3 3 , optionally 2.45 g / cm3 3 - 3.0 g / cm3 3 .

[0018] In any embodiment of the first aspect, the lithium-containing nickel-cobalt-manganese oxide positive electrode material further contains one or more of Zr, Al, B, Fe, Ca, Sr, Ti, V or Y elements.

[0019] In any embodiment of the first aspect, the lithium-containing nickel-cobalt-manganese oxide positive electrode material further contains one or more of Zr, Al, B or Fe elements; optionally, in the lithium-containing nickel-cobalt-manganese oxide positive electrode material, 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, the content of B is 20-300 ppm.

[0020] In any embodiment of the first aspect, the lithium-iron-manganese phosphate positive electrode material further contains one or more of Al, B, Ca, Cr, Cu, K, Mg, Na, P, Si, Ti, V or Zn elements.

[0021] In any embodiment of the first aspect, the lithium-iron-manganese phosphate positive electrode material contains one or more of Al, Ca, Na, Ti or V elements; optionally, in the lithium-iron-manganese phosphate positive electrode material, 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 50-600 ppm, the content of Ti is 100-1000 ppm, the content of V is 1000-3000 ppm.

[0022] In any embodiment of the first aspect, the positive electrode active layer contains one or more of Al, B, Ca, Na, Sr, Ti, V, Y or Zr elements, and the respective mass content based on the total mass of the positive electrode active 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%; B: 0.01%-0.1%.

[0023] In any embodiment of the first aspect, the lithium-iron-manganese phosphate positive electrode material contains a carbon-containing coating layer, and the mass content of carbon in the lithium-iron-manganese phosphate positive electrode material is 1%-3%.

[0024] In any embodiment of the first aspect, in the positive electrode active 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, 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, M3 is less than M4.

[0025] In any embodiment of the first aspect, the lithium-containing nickel-cobalt-manganese oxide particles are spherical or spheroidal polycrystalline particles, and the volume particle size Dv50 of the lithium-containing nickel-cobalt-manganese oxide polycrystalline particles is 1.5 μm-3 μm.

[0026] In any embodiment of the first aspect, the lithium-containing nickel-cobalt-manganese oxide particles are single-crystal particles; and the volume particle size Dv50 of the lithium-containing nickel-cobalt-manganese oxide single-crystal particles is 7 μm-12 μm.

[0027] In any embodiment of the first aspect, the lithium-iron-manganese phosphate positive electrode material particles are single-crystal particles, and the volume particle size Dv50 of the lithium-iron-manganese phosphate positive electrode material is 0.1 μm-15 μm, and is optionally 0.5 μm-2 μm.

[0028] In any embodiment of the first aspect, the positive electrode tab 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.

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

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

[0031] In any embodiment of the first aspect, the areal density of the negative electrode active layer is 90 mg / 1540.25 mm 2 -170 mg / 1540.25 mm 2 , and is optionally 110 mg / 1540.25 mm 2 -160 mg / 1540.25 mm 2 .

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

[0033] In any embodiment of the first aspect, the negative electrode tab further comprises a negative electrode conductive layer, the negative electrode conductive layer is disposed between the negative electrode current collector and the negative electrode active layer, and the negative electrode conductive layer comprises 0.5 μm-3 μm, or 1 μm-2 μm.

[0034] In any embodiment of the first aspect, the negative electrode current collector has a thickness of 4 μm-7 μm, or 4 μm-5 μm.

[0035] In any embodiment of the first aspect, the negative electrode active layer comprises composite graphite particles, the composite graphite particles comprise: body particles, the body particles comprise primary particles or secondary particles, and the body particles comprise artificial graphite; and a coating layer, the coating layer is coated on the surface of the body particles, and the coating layer comprises amorphous carbon.

[0036] In any embodiment of the first aspect, the mass content of amorphous carbon in the coating layer is 2% to 5% based on the total mass of the composite graphite particles.

[0037] In any embodiment of the first aspect, the negative electrode active layer comprises: a first negative electrode active layer disposed on one side of the negative electrode current collector, the first negative electrode active layer comprises one or more of the composite graphite particles and the natural graphite, and optionally the volume average particle size Dv50 of the negative electrode active material in the first negative electrode active layer is 7.5 μm-19.5 μm, or 12.5 μm-18.5 μm; and a second negative electrode active layer disposed on the side of the first negative electrode active layer away from the negative electrode current collector, and optionally the second negative electrode active layer comprises the composite graphite particles, and the volume average particle size Dv50 of the negative electrode active material in the second negative electrode active layer is 7.5 μm-19.5 μm, or 7.5 μm-15.5 μm.

[0038] In any embodiment of the first aspect, 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 .

[0039] In any embodiment of the first aspect, the electrode assembly further comprises an electrolyte, and the lithium ion conductivity of the electrolyte is 10-20 mS / cm, or 12-17 mS / cm.

[0040] In any embodiment of the first aspect, the electrolyte comprises lithium hexafluorophosphate and lithium bisfluorosulfonylimide.

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

[0042] In any implementation form of the first aspect, the battery cell further comprises a shell, the electrode assembly is arranged in an inner cavity of the shell, a length of the shell is L1, a length of the positive electrode tab is L2, and L2 / L1 is 80%-99%, optionally 88%-99%.

[0043] In any implementation form of the first aspect, the shell has one or more of the following features: the L1 is in a range of 300mm-950mm; a height of the shell is 85mm-140mm; a thickness of the shell is 10mm-20mm.

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

[0045] In any implementation form of the first aspect, the battery cell has a liquid injection coefficient of 1.9g / Ah-3.1g / Ah.

[0046] In any implementation form of the first aspect, the battery cell has a volumetric energy density of 470Wh / L-570Wh / L.

[0047] The second aspect of the present application provides a battery device comprising the battery cell provided in any implementation form of the first aspect, the battery device comprising 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 implementation form of the first aspect or the battery device provided in any implementation form 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 effort 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 a battery cell 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 according to an embodiment of the present application shown in FIG. 3.

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

[0055] In the drawings, the figures are not necessarily drawn to scale.

[0056] BRIEF DESCRIPTION OF DRAWINGS

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

[0058] The embodiments of the present application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description and drawings of the following examples are intended to illustrate the principles of the present application by way of example only and are not intended to limit the scope of the present application, i.e., the present application is not limited to the described examples.

[0059] Hereinafter, the embodiments of the battery cell and the electric device according to the present application are specifically disclosed with appropriate reference to the accompanying 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.

[0060] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise specified, the numerical range "a-b" represents a shorthand notation for any real combination of integers between a and b, where 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 just a shorthand notation for these numerical combinations. In addition, when it is stated that a parameter is 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.

[0061] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0062] If there is no special indication, all the technical features of the present application and the optional technical features can be combined with each other to form new technical solutions.

[0063] If there is no special indication, all the 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] If there is no special indication, the "includes" and "contains" mentioned in the present application are open. For example, the "includes" and "contains" can mean that other components not listed can also be included or contained.

[0065] If there is no special indication, in the present application, the term "or" is inclusive. 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 A and B are both true (or exist).

[0066] [Battery cell]

[0067] As analyzed before, the energy density of lithium iron phosphate battery cell is low, in order to improve the energy density of the battery cell.

[0068] 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 active material, the negative electrode active material comprising one or more of a carbon-based material (such as graphite) and a silicon-based material, the positive electrode sheet comprising 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 active material, the positive electrode active material comprising a lithium-containing nickel-cobalt-manganese oxide positive electrode material and a lithium-containing manganese iron phosphate positive electrode material, in the lithium-containing nickel-cobalt-manganese oxide positive electrode material, the Ni element accounts for 50% to 95% of the total molar amount of Ni, Co and Mn elements, and the proportion of the lithium-containing nickel-cobalt-manganese oxide positive electrode material in the positive electrode active material is 5%-95%; in the lithium-containing manganese iron phosphate positive electrode material, the Mn element accounts for 30%-80% of the total molar amount of Mn and Fe elements, and the discharge voltage platform of the battery cell at room temperature and a rate of 0.1C is 3.29V-4.15V.

[0069] The energy of the battery cell is related to the voltage plateau and the capacity of the battery cell, and the capacity is related to the gram capacity of the positive active material. The present application intends to study how to design the battery cell with mixed positive material to improve the energy of the battery cell and not to deteriorate other battery performances such as cycle performance.

[0070] The positive active material of the battery cell of the present application includes lithium iron manganese phosphate positive material and lithium-containing nickel cobalt manganese oxide positive material. The content of Mn element in the lithium iron manganese phosphate positive material is positively correlated with the voltage plateau of the mixed positive material, but is negatively correlated with the gram capacity of the lithium iron manganese phosphate positive material, and is not conducive to the skeleton stability of the lithium iron manganese phosphate positive material in long-term cycle. The content of Ni element in the lithium-containing nickel cobalt manganese oxide positive material is positively correlated with the voltage plateau and the gram capacity of the mixed positive material, but is not conducive to the skeleton stability of the lithium-containing nickel cobalt manganese oxide in long-term cycle.

[0071] Based on the actual needs of customers for low cost, high specific energy and long cycle, the present application finds that by making the content of Ni element in the lithium-containing nickel cobalt manganese oxide positive material account for 50% to 95% of the total molar amount of Ni, Co and Mn elements, and the content of the lithium-containing nickel cobalt manganese oxide positive material in the positive active material accounts for 5%-95%; further by making the content of Mn element in the lithium iron manganese phosphate positive material account for 30%-80% of the total molar amount of Mn element and Fe element, the gram capacity of the mixed positive material is better, and the voltage plateau is kept in a suitable range, so that the battery cell takes into account lower cost, energy density and higher cycle performance.

[0072] At the same time, the lithium iron manganese phosphate positive material has an olivine structure which is more stable than the layered structure of the lithium-containing nickel cobalt manganese oxide positive material, and has low cost. The cycle stability, safety and power performance of the battery cell with mixed positive material of lithium iron manganese phosphate positive material and lithium-containing nickel cobalt manganese oxide positive material are improved compared with the battery cell with pure lithium-containing nickel cobalt manganese oxide positive material, and the cost is greatly reduced compared with the lithium-containing nickel cobalt manganese oxide positive material.

[0073] In some embodiments, the discharge voltage plateau of the battery cell at room temperature and 0.1C rate is 3.67V-3.86V, such as 3.67V, 3.69V, 3.77V or 3.86V. The content of Ni element in the lithium-containing nickel cobalt manganese oxide positive material of the positive active material of the battery cell meeting the above discharge voltage plateau is more (further improving the gram capacity of the material) and / or the content of Mn element in the lithium iron manganese phosphate positive material is more (further improving the discharge voltage plateau of the material), so that the energy density of the battery cell can be further improved.

[0074] In some embodiments, in the lithium-containing nickel-cobalt-manganese oxide positive electrode material, the molar content of the Ni element relative to the total moles of nickel-cobalt-manganese elements is 80%-95%. The higher the content of the Ni element, the higher the gram capacity of the lithium-containing nickel-cobalt-manganese oxide positive electrode material, and the more conducive to improving the energy density of the battery cell.

[0075] In some embodiments, in the lithium-containing nickel-cobalt-manganese oxide positive electrode material, the molar content of the Ni element relative to the total moles of nickel-cobalt-manganese elements is 80%-95%. The higher the content of the Ni element, the higher the gram capacity of the lithium-containing nickel-cobalt-manganese oxide positive electrode material, and the more conducive to improving the energy density of the battery cell.

[0076] In some embodiments, the mass content of the lithium-containing nickel-cobalt-manganese oxide positive electrode material in the positive electrode active material is 50%-95% or 50%-70% based on the total mass of the positive electrode active material. With the above-mentioned content of the lithium-containing nickel-cobalt-manganese oxide positive electrode material in the positive electrode active material, the advantages of the gram capacity of the two positive electrode materials can be fully utilized, and the stability and fast charging performance are complementary, so that the energy density and cycle performance of the battery cell are fully improved.

[0077] The elements in the above-mentioned materials can be determined by the following method:

[0078] For the positive electrode sheet of the battery cell, the positive electrode sheet is washed with DMC (dimethyl carbonate) to collect the positive electrode material in the positive electrode active layer after drying and calcining the positive electrode sheet. The positive electrode material is tested by inductively coupled plasma atomic emission spectrometry (ICP-OES).

[0079] In some embodiments, the energy density of the battery cell can be further improved by the following method: 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 mm 2 .

[0080] The above-mentioned area density is tested by the following method:

[0081] Take a single-sided coated positive electrode sheet (if it is a double-sided coated 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, and measure its thickness H1. Then wipe off the positive electrode active material layer of the above-weighed positive electrode sheet, weigh the positive electrode current collector and record it as M0, and measure its thickness H0. The single-sided coating weight (i.e. the area density) of the positive electrode active material layer = (the weight of the positive electrode sheet M1 - the weight of the positive electrode current collector M0) / S1.

[0082] In some embodiments, if a positive electrode conductive layer is arranged between the positive electrode active layer and the positive electrode current collector, the mass of the positive electrode conductive layer can be ignored when testing the compaction density or the area density of the positive electrode active layer, because the mass of the positive electrode conductive layer is significantly lower than the mass of the positive electrode active layer. The same applies to the negative electrode active layer.

[0083] In some embodiments, the area capacity of the positive electrode tab is 50 mAh / 15 40.25 mm 2 - 350 mAh / 15 40.25 mm 2 , and optionally 80 mAh / 15 40.25 mm 2 - 150 mAh / 15 40.25 mm 2 . The energy density of the battery cell with the above area capacity is further improved.

[0084] The above area capacity is tested by the following method:

[0085] The positive electrode tab is assembled into a button cell, and charged at a rate of 0.1C to 4.2V. After standing for 30 min, the capacity discharged at a rate of 0.1C to 2.5V is recorded as the button cell capacity. The area capacity (unit: mAh / 15 40.25 mm 2 ) of the positive electrode tab = button cell capacity / button cell tab area * 15 40.25.

[0086] The compaction density of the positive electrode active layer affects the stability of the electrolyte infiltration and volume expansion in the positive electrode tab, and also affects the volumetric energy density of the battery cell. Generally, the greater 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 improving the volumetric energy density of the battery cell. 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 active material, thus improving the charging 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 corresponding positive electrode active layer in the battery cell at 100% SOC state is 2.45 g / cm 3 - 3.4 g / cm 3 , and optionally 2.5 g / cm 3 - 3.2 g / cm 3 . Thus, the comprehensive performance of improving energy density, charging performance, and cycle performance is achieved.

[0087] The 100% SOC state described above refers to a state in which the battery cell is charged to a voltage of 4.2V at room temperature at a rate of 0.33C, and then charged at a constant voltage until the current is less than 0.05C.

[0088] The test method for the compaction density of the positive electrode active layer can be implemented according to the following method:

[0089] Based on the areal density test described above, the thickness of the positive electrode active layer is obtained as the thickness H1 of the positive electrode sheet minus the thickness H0 of the positive electrode current collector, 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 thickness of the single-sided positive electrode active layer.

[0090] In order to more stably improve the compaction density of the positive electrode active layer, in some embodiments, the powder compaction density of the positive electrode active material at 30000N is ≥2.43g / cm 3 , and optionally ≥2.45g / cm 3 , and optionally 2.45g / cm 3 -3.0g / cm 3 .

[0091] In some embodiments, the lithium-containing nickel-cobalt-manganese oxide positive electrode material further contains one or more of Zr, Al, B, Fe, Ca, Sr, Ti, V, or Y elements; optionally, the lithium-containing nickel-cobalt-manganese oxide positive electrode material further includes one or more of Zr, Al, B, or Fe elements. The elements in the above modified material can exist in the lithium-containing nickel-cobalt-manganese oxide in the form of doping or coating.

[0092] The Al, B, Ti, Y, Zr, Sr, etc. elements in the lithium-containing nickel-cobalt-manganese oxide can significantly improve its electrochemical performance, structural stability, and cycle performance. For example:

[0093] Al can form AlO6 octahedron, which has a structure similar to TMO6 octahedron (TM is a transition metal) 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 lithium-containing nickel-cobalt-manganese oxide. Al doping helps to improve the chemical stability of the lithium-containing nickel-cobalt-manganese oxide, reduces cationic disordering, and improves its cycle performance.

[0094] The doping of B in the lithium-containing nickel-cobalt-manganese oxide tends to occur on the surface 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 lithium-containing nickel-cobalt-manganese oxide, reduces surface reconstruction, and thus improves the cycle stability of the material. When co-doped with Al, the competitive doping chemistry of B makes it more inclined to aggregate on the surface, achieving synergistic stabilization of the surface and the bulk.

[0095] Ti can significantly improve the particle strength of lithium-containing nickel-cobalt-manganese oxides 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 Li ion transmission rate.

[0096] Y helps to improve the cycle stability and rate performance of lithium-containing nickel-cobalt-manganese oxides. Y has a large ionic radius and can act as a support framework after doping, inhibiting surface structure phase transition and Li / Ni mixing. In addition, Y doping can also widen the Li ion transmission channel and improve the Li ion transmission rate.

[0097] Zr can significantly improve the structural stability and thermal stability of lithium-containing nickel-cobalt-manganese oxides. 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.

[0098] Sr is usually co-doped with other elements such as Zr to form a protective layer or co-doped structure such as SrZrO3. Sr has a large diameter and can act as a support, significantly expanding the lattice unit parameter and 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, improving the structural stability and cycle performance of lithium-containing nickel-cobalt-manganese oxides.

[0099] Therefore, elements such as Al, B, Ti, Y, Zr, and Sr can improve the electrochemical performance, structural stability, and cycle performance of lithium-containing nickel-cobalt-manganese oxides to varying degrees. These elements play a role by forming stable chemical bonds, widening the transmission channel, and inhibiting adverse phase changes.

[0100] In order to fully play the role of each element, in some embodiments, the mass content of elements in the lithium-containing nickel-cobalt-manganese oxide positive electrode material satisfies one or more of the following characteristics: 1) the content of Zr is 1000-3000 ppm; 2) the content of Al is 100-1000 ppm; 3) the content of B is 20-300 ppm.

[0101] In some embodiments, the lithium manganese iron phosphate positive electrode material further contains one or more of Al, B, Ca, Cr, Cu, K, Mg, Na, P, Si, Ti, V or Zn. Optionally, the lithium manganese iron phosphate positive electrode material contains one or more of Al, Ca, Na, Ti or V. The elements in the modified material can be present in the lithium manganese iron phosphate positive electrode material in the form of doping or coating. 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.

[0102] In order to fully exert the effects of the elements, in the lithium manganese iron phosphate positive electrode material of some embodiments, the mass content of the elements satisfies at least one of the following: the content of Al is 100-1000 ppm, the content of Ca is 50-300 ppm, the content of Na is 50-600 ppm, the content of Ti is 100-1000 ppm, and the content of V is 1000-3000 ppm.

[0103] In some embodiments, the positive electrode active layer contains one or more of Al, B, Ca, Na, Sr, Ti, V, Y or Zr, 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%; and B: 0.01%-0.1%, based on the total mass of the positive electrode active material.

[0104] In order to improve the electrical conductivity and surface stability of the lithium manganese iron phosphate positive electrode material, in some embodiments, the lithium manganese iron phosphate positive electrode material includes a carbon-containing coating layer, and the mass content of carbon in the lithium manganese iron phosphate positive electrode material is 1%-3%.

[0105] In some embodiments, the specific capacity of the positive electrode active material is improved by size grading of the material particles in the positive electrode active material. In the positive electrode active 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.

[0106] By the above particle size control, the small particle size of the lithium manganese iron phosphate positive electrode material is matched with the large particle size of the lithium-containing nickel cobalt manganese oxide, the small particle size can be filled in the gap of the large particle size, so that the compaction of the positive electrode active material can be improved; and the matching mode plays a protective role on the lithium manganese iron phosphate positive electrode material, effectively reducing the crushing probability of the lithium manganese iron phosphate positive electrode material under the same cold pressure.

[0107] The energy density or cycle performance of the battery cell is improved by the particle form of the positive electrode material. In some embodiments, the particles of the lithium-containing nickel cobalt manganese oxide are spherical or spherical-like polycrystalline particles, and the volume particle size Dv50 of the polycrystalline particles of the lithium-containing nickel cobalt manganese oxide is 1.5 μm-3 μm. The polycrystalline form of the lithium-containing nickel cobalt manganese oxide has a higher gram capacity, so the energy density of the battery cell can be better improved.

[0108] In some embodiments, the particles of the lithium-containing nickel cobalt manganese oxide are single-crystal particles, and the volume particle size Dv50 of the single-crystal particles of the lithium-containing nickel cobalt manganese oxide is 7 μm-12 μm. The single-crystal form of the lithium-containing nickel cobalt manganese oxide has a more stable structure, so the cycle performance of the battery cell can be better improved.

[0109] In some embodiments, in order to further improve the gram capacity of the lithium manganese iron phosphate positive electrode material, the particles of the lithium manganese iron phosphate positive electrode material are single-crystal particles, and the volume particle size Dv50 of the lithium manganese iron phosphate positive electrode material is 0.1 μm-15 μm, and optionally 0.5 μm-2 μm.

[0110] 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 positive electrode conductive layer is used to improve the electron transmission rate, thereby improving the rate performance of the battery cell.

[0111] In order to improve the adhesion between the positive electrode current collector and the positive electrode active layer by using the positive electrode conductive layer, in some embodiments, the positive electrode conductive layer comprises a positive electrode binder and a positive electrode conductive material.

[0112] 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 thickness of the positive electrode conductive layer is not too large to affect the energy density of the battery cell.

[0113] In some embodiments, the number of the above positive electrode active layers is single layer or multiple layers. If it is a single layer, the above two positive electrode active materials are mixed in the same layer; if it is a multiple layer, the two materials can be arranged in different layers or mixed in different mixing ratios and arranged in different layers.

[0114] 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 active 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 of the active layer due to expansion. 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.

[0115] 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.).

[0116] In some embodiments, the positive electrode film 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.

[0117] In some embodiments, the positive electrode film layer can also optionally include a conductive agent. As an example, the conductive agent can include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0118] 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-methylpyrrolidone) 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.

[0119] [Negative electrode sheet]

[0120] 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 mm 2 -170 mg / 1540.25 mm 2; optionally 110 mg / 1540.25 mm 2 -160 mg / 1540.25 mm 2 .

[0121] When the battery cell is charged, the negative active material expands, resulting in a decrease in the compaction density of the negative active layer. In some embodiments, the compaction density of the negative active layer corresponding to the battery cell in the 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.

[0122] 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 negative electrode conductive layer comprises 0.5 μm-3 μm, or 1 μm-2 μm. The negative electrode conductive layer is used to improve the conductivity of the negative electrode sheet, and further improve the rate performance of the battery cell.

[0123] 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, and optionally 4 μm-5 μm. The negative electrode current collector with the thickness in the range has little 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 expansion of the battery cell during charging.

[0124] In some embodiments, the above negative electrode active layer 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.

[0125] 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. In some embodiments, the mass content of amorphous carbon in the coating layer can be selected to be 2% to 5% based on the total mass of the composite graphite particles.

[0126] In some embodiments, the number of layers of the negative electrode active layer is one or more. When the number of layers of the negative electrode active layer is more than one, negative electrode active materials with corresponding characteristics can be arranged in different layers of the negative electrode active layer according to different purposes.

[0127] 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 first negative active layer includes one or more of the composite graphite particles and the natural graphite, and 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 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.

[0128] In some embodiments, the volume average particle size Dv50 of the negative active 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 active 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 negative active materials with corresponding particle sizes. When the particle size of the negative active material in the second negative active layer is smaller relative to the particle size of the negative active 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.

[0129] 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 .

[0130] In some embodiments, the negative current collector can use a metal foil or a composite current collector. For example, as a 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.).

[0131] 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).

[0132] 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.

[0133] 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.

[0134] 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, the negative electrode sheet can be obtained.

[0135] [Separator]

[0136] 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.

[0137] 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.

[0138] In some embodiments, the separator comprises a porous base film and a functional layer provided 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.

[0139] [Electrolyte]

[0140] 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.

[0141] In some embodiments, the above-mentioned battery cell further comprises an electrolyte, and the electrolyte comprises an electrolyte salt and a solvent.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] In some embodiments, the lithium ion conductivity of the electrolyte solution is selected to be 10-20 mS / cm or 12-17 mS / cm.

[0146] In some embodiments, the electrolyte solution 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.

[0147] In some embodiments, the molar 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 above-described lithium salt, the excessive increase in the cost of the battery cell is controlled.

[0148] In some embodiments, the battery cell further includes a housing in which the electrode assembly is disposed, 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.

[0149] In some embodiments, the size of the housing has one or more of the following characteristics: the range of L1 is 300-950 mm; the height of the housing is 85-140 mm; and the thickness of the housing is 10-20 mm.

[0150] 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.

[0151] In some embodiments, the shell is an aluminum shell or a steel shell.

[0152] In some embodiments, the battery cell has a liquid injection coefficient of 1.9 g / Ah-3.1 g / Ah. The liquid injection coefficient in the above range makes the lithium ion transmission smoother and more stable during the cycling process of the battery cell.

[0153] In some embodiments, the battery cell has a volumetric energy density of 470 Wh / L-570 Wh / L.

[0154] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator film can be made into an electrode assembly through a winding process or a stacking process.

[0155] 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 square structure as an example.

[0156] 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 sheet, the negative electrode sheet, and the separator film can be made into an electrode assembly 52 through 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.

[0157] 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.

[0158] In the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the thickness direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0159] Optionally, the battery module 4 can further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0160] In some embodiments, the above 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, which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0161] 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 provided 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.

[0162] 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, and can also 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.

[0163] As the power utilization device, the battery cell, the battery module or the battery pack can be selected according to the use requirement thereof.

[0164] 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 the power utilization device for high power and high energy density of the battery cell, the battery pack or the battery module can be used.

[0165] [Embodiment]

[0166] Hereinafter, an embodiment of the application will be described. The following described embodiment is exemplary and is only used to explain the application, and cannot be understood as a limitation of the application. If a specific technology or condition is not mentioned in the embodiment, 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 mentioned by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0167] Embodiment 1

[0168] Positive electrode tab

[0169] The positive electrode active material layer comprises a positive electrode active material, a binder polyvinylidene fluoride, and a conductive agent acetylene black (mass ratio of 97:2:1), the positive electrode active material comprises a lithium-containing nickel-cobalt-manganese oxide positive electrode material and a lithium iron manganese phosphate positive electrode material, the mass ratio of the lithium-containing nickel-cobalt-manganese oxide positive electrode material to the lithium iron manganese phosphate positive electrode material in the positive electrode active material is 5:95, and the mass content of carbon in the lithium iron manganese phosphate positive electrode material is about 2%. In the lithium-containing nickel-cobalt-manganese oxide positive electrode material, the subscripts of Ni, Co, and Mn in the chemical formula are 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 the atomic number 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 electrode active material, the mass content of Al is 0.063%, the mass content of B is 0.0039%, and the mass content of Zr is 0.256%. The surface density of the positive electrode active layer is set to 300 mg / 1540.25 mm 2 . The thickness of the current collector aluminum foil is 12 μm, the positive electrode film layer is located on both sides of the aluminum foil, and there is a conductive primer layer between the positive electrode film layer and the aluminum foil. The conductive primer layer is a film layer formed by uniformly mixing a positive electrode conductive agent, a positive electrode binder, and a solvent, and then coating and drying on the surface of the positive electrode current collector. The thickness of the conductive primer layer is 1 μm, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 50%, and the mass content of the positive electrode binder in the negative electrode conductive layer is 50%. The length of the positive electrode tab is 542 mm, and the height is 94 mm.

[0170] The negative electrode tab

[0171] The negative electrode active material layer comprises two layers of an upper layer (far from the current collector) and a lower layer (close to the current collector), and the lower layer comprises 96:1:2:1 of a negative electrode active material, a conductive agent acetylene black, a binder styrene butadiene rubber, and a thickening agent sodium carboxymethyl cellulose. The negative electrode active material is composed of composite graphite particles (the composite graphite particles comprise 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 at a mass ratio of 5:5, wherein the Dv50 of the composite graphite particles is 17 μm, and the powder compaction density under a pressure of 20,000 N is 1.6 g / cm 3 ; the Dv50 of the natural graphite is 18 μm. The negative electrode active material in the upper layer is the composite graphite particles, the Dv50 is 10 μm, and the powder compaction density under a pressure of 20,000 N is 1.8 g / cm 3 .

[0172] The negative current collector is a copper foil with a thickness of 5 μm, and a negative conductive layer is arranged 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 the mixture on the surface of the negative current collector and drying, and the thickness of the conductive primer 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%.

[0173] Electrolyte

[0174] The electrolyte comprises organic solvents, ethyl acetate EA, ethylene carbonate EC, and methyl ethyl carbonate EMC (mass ratio 50:35:15), 10.5% of lithium hexafluorophosphate (LiPF6) and 4.5% of lithium bisfluorosulfonylimide LiFSI as lithium salts, 2.5% of an 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 13 mS / cm.

[0175] Separator film

[0176] A polyethylene (PE) film coated with a nano-aluminum oxide coating layer is used as the separator film.

[0177] Battery cell

[0178] The battery cell is obtained by stacking the positive electrode sheet, the separator film, and the negative electrode sheet, and then adding the electrode assembly into an outer packaging square aluminum shell (length 550 mm, thickness 19.5 mm, height 100 mm), drying, and then injecting the electrolyte with an injection coefficient of 2.9. After the packaging, high-temperature standing, formation, secondary injection, aging, and capacity processes, the battery cell is obtained.

[0179] Sheet test

[0180] The compaction density of the positive active layer / negative active layer:

[0181] The compaction density of the positive active layer / negative active layer refers to the compaction density of the positive active layer / negative active layer 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 charged at a constant voltage until the current is less than 0.05 C, wherein the compaction density of the negative active layer is 1.36 g / cm 3 .

[0182] Method for testing the area density and compaction density:

[0183] 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. Then wipe off the positive active layer of the above weighed positive electrode sheet, weigh the weight of the positive current collector, and record it as M0. 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, 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.

[0184] The area density and compaction density of the negative electrode sheet are tested in the same way as above.

[0185] Volume energy density test method:

[0186] Place the battery monomer at room temperature, charge it at 0.33C constant current to 4.2V, and then charge it at constant voltage to 0.05C; discharge it at 0.33C constant current to 2.5V, and record the discharge capacity A0 at this time, unit: Ah; measure the length, width and height of the battery monomer using a caliper (generally calculated based on the size of the battery shell, excluding the height of the electrode terminal, and excluding the insulating film outside the shell), calculate the volume V0 of the monomer battery, unit L; the volume energy density VED of the battery monomer = (A0 x discharge platform voltage) / V0, unit Wh / L.

[0187] Cycle life test method:

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

[0189] At 45°C, charge the battery monomer at 1C constant current to the charge cut-off voltage 4.2V, and then discharge it at 1C constant current to 2.0V, which is one charge-discharge cycle. Repeat the above charge-discharge cycle steps until the cycle capacity retention rate (i.e. Cn / C0 x 100%) is 80% (the discharge capacity at 1C constant current to 2.0V is recorded as C0, and Cn is the discharge capacity of the nth cycle). The more the cycle number, the better the cycle performance of the battery monomer.

[0190] Examples 2 to 6 and Comparative Examples 1 to 3 adjust the composition of the positive electrode material on the basis of Example 1, and the specific composition is shown in Table 1. In addition, the area density of the positive active layer of Examples 2 to 6 and Comparative Examples 1 to 3 is the same as that of Example 1. In Table 1, A:B represents the mass ratio of the lithium-containing nickel-cobalt-manganese oxide positive electrode material to the manganese iron lithium phosphate positive electrode material.

[0191]

[0192] In Table 1, the chemical formula is LiNi0.8 Co 0.1 Mn 0.1 The content of other elements in the lithium-containing nickel cobalt manganese oxide positive electrode material of O2is as follows: the mass content of Al is 0.062%, the mass content of B is 0.0037%, the mass content of Ti is 0.0003%, the mass content of Y is 0.008%, the mass content of Zr is 0.25%, and the mass content of Sr is 0.0001%; the chemical formula is LiNi 0.95 Co 0.03 Mn 0.02 The content of other elements in the lithium-containing nickel cobalt manganese oxide positive electrode material of O2is as follows: the mass content of Al is 0.062%, the mass content of B is 0.0037%, the mass content of Ti is 0.0003%, the mass content of Y is 0.008%, the mass content of Zr is 0.25%, and the mass content of Sr is 0.0001%; the chemical formula is LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 The content of other elements in the lithium-containing nickel cobalt manganese oxide positive electrode material of O2is as follows: the mass content of Al is 0.064%, the mass content of B is 0.041%, the mass content of Ti is 0.0004%, the mass content of Y is 0.008%, the mass content of Zr is 0.26%, and the mass content of Sr is 0.0001%.

[0193] According to the comparison of the examples and the comparative examples in Table 1, it can be seen that, when the content of nickel element in the lithium-containing nickel cobalt manganese oxide positive electrode material, the content of manganese element in the lithium-containing manganese iron phosphate positive electrode material, and the voltage platform of the battery monomer are within the range set in the present application, not only the high energy density of the battery monomer can be achieved, but also the high cycle stability of the battery monomer can be maintained.

[0194] The effects of the mass ratio of the lithium-containing nickel cobalt manganese oxide positive electrode material and the lithium-containing manganese iron phosphate positive electrode material on the energy density and the cycle performance of the battery monomer were investigated. Examples 7 to 9 were based on Example 5, only the mass ratio of the lithium-containing nickel cobalt manganese oxide positive electrode material and the lithium-containing manganese iron phosphate positive electrode material (i.e. A:B in Table 2) was adjusted, and the rest remained unchanged. The specific test data are recorded in Table 2.

[0195] Table 2

[0196] According to the data in Table 2, it can be seen that, as the content of the lithium-containing manganese iron phosphate positive electrode material decreases, the voltage platform of the battery monomer is slightly improved, the cycle number is slightly reduced, but the energy density of the battery monomer is obviously improved.

[0197] The following investigates the influence of the surface capacity of the positive active layer on the energy density and cycle performance of the battery cell. On the basis of Example 5, the surface density of the positive active layer is adjusted and other parameters remain unchanged, so as to adjust the surface capacity of the positive active layer, and the test results are recorded in Table 3.

[0198] Table 3

[0199] According to the data in Table 3, it can be seen that when the surface capacity of the positive active layer is increased, appropriately adjusting the surface density of the negative active layer is beneficial to fully exert the surface capacity of the positive active layer, and further improve the energy density of the battery cell; in the trend of increasing the surface capacity of the positive active layer, the cycle performance of the battery cell slightly decreases, but the overall level is high, which shows that the surface capacity has little influence on the cycle performance.

[0200] The following investigates the influence of the compaction of the positive active layer on the energy density and cycle performance of the battery cell. On the basis of Example 5, only the compaction of the positive active layer is adjusted to change the full charge compaction, and the rest of the settings remain unchanged, and the test results are recorded in Table 4.

[0201] Table 4

[0202] According to the comparison of the data in Table 4, it can be seen that as the full charge compaction of the positive active layer increases, the volume energy density of the battery cell increases, but it will cause the cycle performance of the battery cell to slightly decrease.

[0203] 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, comprising an electrode assembly, the electrode assembly including a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode, wherein, The negative electrode sheet includes 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 includes a negative electrode active material, which includes one or more of carbon-based materials and silicon-based materials. 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 includes a positive active material, which includes lithium manganese iron phosphate positive electrode material and lithium-containing nickel cobalt manganese oxide positive electrode material. In the lithium-containing nickel-cobalt-manganese oxide cathode material, Ni element accounts for 50% to 95% of the total molar amount of Ni, Co, and Mn elements, and the lithium-containing nickel-cobalt-manganese oxide cathode material accounts for 5% to 95% of the cathode active material; in the lithium manganese iron phosphate cathode material, Mn element accounts for 30% to 80% of the total molar amount of Mn and Fe elements. Furthermore, the discharge voltage plateau of the battery cell at room temperature and a rate of 0.1C is 3.29V-4.15V.

2. The battery cell according to claim 1, wherein, The discharge voltage plateau of the battery cell at room temperature and a 0.1C rate is 3.67V-3.86V.

3. The battery cell according to claim 1 or 2, wherein, In the lithium-containing nickel-cobalt-manganese oxide cathode material, the molar content of Ni relative to the total molar number of nickel, cobalt, and manganese elements is 80%-95%.

4. The battery cell according to any one of claims 1 to 3, wherein, In the lithium manganese iron phosphate cathode material, the molar content of Mn element relative to the total molar number of Mn and Fe elements is 50%-70%.

5. The battery cell according to any one of claims 1 to 4, wherein, Based on the total mass of the positive electrode active material, the mass content of the lithium manganese iron phosphate positive electrode material is 50%-95%.

6. The battery cell according to any one of claims 1 to 5, wherein, Based on the total mass of the positive electrode active material, the mass content of the lithium manganese iron phosphate positive electrode material is 50%-70%.

7. The battery cell according to any one of claims 1 to 6, wherein, The areal density of the positive electrode active layer is 200 mg / 1540.25 mm². 2 -370mg / 1540.25mm 2 The option is 240mg / 1540.25mm. 2 -340mg / 1540.25mm 2 .

8. The battery cell according to any one of claims 1 to 7, wherein, The positive electrode has an area capacity of 50mAh / 1540.25mm². 2 -350mAh / 1540.25mm 2 Available in 80mAh / 1540.25mm configurations. 2 -150mAh / 1540.25mm 2 .

9. The battery cell according to any one of claims 1 to 8, wherein, The compaction density of the positive electrode active layer in the battery cell at 100% SOC is 2.45 g / cm³. 3 -3.4g / cm 3 2.5g / cm³ is an option. 3 -3.2g / cm 3 .

10. The battery cell according to any one of claims 1 to 9, wherein, The positive electrode active material has a powder compaction density ≥ 2.43 g / cm³ at 30000 N. 3 The optional value is ≥2.45g / cm³. 3 2.45g / cm³ is an optional value. 3 -3.0g / cm 3 .

11. The battery cell according to any one of claims 1 to 10, wherein, The lithium-containing nickel-cobalt-manganese oxide cathode material also contains one or more of the elements Zr, Al, B, Fe, Ca, Sr, Ti, V, or Y.

12. The battery cell according to claim 11, wherein, The lithium-containing nickel-cobalt-manganese oxide cathode material further includes one or more of Zr, Al, B, or Fe elements; optionally, in the lithium-containing nickel-cobalt-manganese oxide cathode material, the mass content of the element satisfies at least one: Zr content 1000-3000ppm, Al content 100-1000ppm, and B content 20-300ppm.

13. The battery cell according to any one of claims 1 to 12, wherein, The lithium manganese iron phosphate cathode material also contains one or more of the elements Al, B, Ca, Cr, Cu, K, Mg, Na, P, Si, Ti, V, or Zn.

14. The battery cell according to claim 13, wherein, The lithium manganese iron phosphate cathode material includes one or more of the elements Al, Ca, Na, Ti, or V; optionally, in the lithium manganese iron phosphate cathode material, the mass content of the element satisfies at least one of the following: Al content 100-1000ppm, Ca content 50-300ppm, Na content 50-600ppm, Ti content 100-1000ppm, and V content 1000-3000ppm.

15. The battery cell according to any one of claims 1 to 15, wherein, The positive electrode active layer contains one or more of the elements Al, B, Ca, Na, Sr, Ti, V, Y, or Zr, and the mass content of each element satisfies the following based on the total mass of the positive electrode active material: 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%.

16. The battery cell according to any one of claims 1 to 15, wherein, The lithium manganese iron phosphate cathode material includes a carbon-containing coating layer, and the carbon content in the lithium manganese iron phosphate cathode material is 1%-3% by mass.

17. The battery cell according to any one of claims 1 to 16, wherein, In the positive electrode active material The mass content of Fe in particles with a diameter less than or equal to Dv10 is M1, and the mass content of Fe in particles with a diameter greater than or equal to Dv90 is M2, where M1 is greater than M2; and / or The mass content of Ni in particles with a diameter less than or equal to Dv10 is M3, and the mass content of Ni in particles with a diameter greater than or equal to Dv90 is M4, where M3 is less than M4.

18. The battery cell according to any one of claims 1 to 17, wherein, The lithium-containing nickel-cobalt-manganese oxide particles are spherical or near-spherical polycrystalline particles, and optionally the volumetric particle size Dv50 of the lithium-containing nickel-cobalt-manganese oxide polycrystalline particles is 1.5μm-3μm.

19. The battery cell according to any one of claims 1 to 17, wherein, The lithium-containing nickel-cobalt-manganese oxide particles are single-crystal particles; optionally, the volumetric particle size Dv50 of the lithium-containing nickel-cobalt-manganese oxide single-crystal particles is 7μm-12μm.

20. The battery cell according to any one of claims 1 to 19, wherein, The lithium manganese iron phosphate cathode material particles are single crystal particles, and optionally the volumetric particle size Dv50 of the lithium manganese iron phosphate cathode material is 0.1μm-15μm, or optionally 0.5μm-2μm.

21. The battery cell according to any one of claims 1 to 20, wherein, The positive electrode sheet further includes a positive conductive layer, which is disposed between the positive current collector and the positive active layer.

22. The battery cell according to claim 21, 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 1μm-2μm.

23. The battery cell according to any one of claims 1 to 22, wherein, The thickness of the positive electrode current collector is 9μm-17μm, and can be selected as 10μm-13μm.

24. The battery cell according to any one of claims 1 to 23, wherein, The areal density of the negative electrode active layer is 90 mg / 1540.25 mm. 2 -170mg / 1540.25mm 2 ; 110mg / 1540.25mm is optional. 2 -160mg / 1540.25mm 2 .

25. The battery cell according to any one of claims 1 to 24, wherein, The compaction density of the negative electrode active layer corresponding to the battery cell at 100% SOC is 1.04 g / cm³. 3 -1.48g / cm 3 ; 1.23g / cm³ is an optional value. 3 -1.38g / cm 3 .

26. The battery cell according to any one of claims 1 to 25, wherein, The negative electrode sheet further includes a negative electrode conductive layer, which is disposed between the negative electrode current collector and the negative electrode active layer. The negative electrode conductive layer has a thickness of 0.5μm-3μm or 1μm-2μm.

27. The battery cell according to any one of claims 1 to 26, wherein, The thickness of the negative electrode current collector is 4μm-7μm, and can be selected as 4μm-5μm.

28. The battery cell according to any one of claims 1 to 27, wherein, The negative electrode active layer comprises composite graphite particles, wherein the composite graphite particles include: Bulk particles, including primary or secondary particles, including artificial graphite; and A coating layer is applied to the surface of the bulk particles, and the coating layer includes amorphous carbon.

29. The battery cell according to claim 28, wherein, Based on the total mass of the composite graphite particles, the mass content of amorphous carbon in the coating layer is 2% to 5%.

30. The battery cell according to claim 28 or 29, wherein, The negative electrode active layer includes: A first negative electrode active layer is disposed on one side of the negative electrode current collector. The first negative electrode active layer comprises one or more of composite graphite particles and natural graphite. Optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode active layer is 7.5 μm-19.5 μm, optionally 12.5 μm-18.5 μm. The second negative electrode active layer is disposed on the side of the first negative electrode active layer away from the negative electrode current collector. Optionally, the second negative electrode active layer includes composite graphite particles, and the volume average particle size Dv50 of the negative electrode active material in the second negative electrode active layer is 7.5μm-19.5μm, optionally 7.5μm-15.5μm.

31. The battery cell according to any one of claims 28 to 30, wherein, The compacted density of the composite graphite particles under a pressure of 20,000 N is 1.5 g / cm³. 3 -1.7g / cm 3 Or 1.55g / cm 3 -1.65g / cm 3 .

32. The battery cell according to any one of claims 1 to 31, wherein, The electrode assembly also includes an electrolyte, wherein the lithium-ion conductivity of the electrolyte is 10-20 mS / cm or 12-17 mS / cm.

33. The battery cell according to claim 32, wherein, The electrolyte comprises lithium hexafluorophosphate and lithium difluorosulfonylimide.

34. The battery cell according to claim 33, wherein, The molar ratio of lithium difluorosulfonylimide to lithium hexafluorophosphate is (2-5):

10.

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

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

37. The battery cell according to claim 35 or 36, wherein, The casing is made of aluminum or steel.

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

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

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

41. An electrical device comprising a battery cell according to any one of claims 1 to 39 or a battery device according to claim 40.

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