Battery cell, battery device and electric device

Abstract

The invention provides a battery monomer, a battery device and a power utilization device. The battery monomer comprises an electrode assembly, the electrode assembly comprises a positive pole piece, a negative pole piece and an isolating membrane, the negative pole piece comprises a negative pole current collector and a negative pole active layer arranged on at least one side of the negative pole current collector, the negative pole active layer comprises a negative pole material, and the negative pole material comprises a carbon material; the positive electrode plate comprises a positive electrode current collector and a positive electrode active layer arranged on at least one side of the positive electrode current collector, the positive electrode active layer comprises a positive electrode material, the positive electrode material comprises a lithium-containing phosphate positive electrode material and a nickel-containing lithium transition metal oxide, and the mass content of the nickel-containing lithium transition metal oxide in the positive electrode active material is 5-50%; the mass content of Ni in the nickel-containing lithium transition metal oxide is greater than or equal to 30%; and the powder resistivity of the positive electrode material under 12 MPa is 30 omega.cm to 5000 omega.cm.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell, a battery device and an electrical device. Background Art

[0002] Phosphate-based batteries are widely used as power batteries in electric vehicles due to their low cost. The phosphate-based positive electrode materials have obvious cost advantages over ternary positive electrode materials. However, the energy density of phosphate-based positive electrode materials is low, so it is necessary to improve the energy density of the battery system while maintaining the low cost advantage. Summary of the invention

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

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

[0005] In order to maintain the low-cost advantage of phosphate-based positive electrode materials, the present application mixes lithium-containing phosphate-based positive electrode materials and nickel-containing lithium transition metal oxides, and controls the mass content of nickel-containing lithium transition metal oxides within the range of 5%-50%, so that the battery cell has a good volume energy density and maintains a cost advantage. However, when the mass content of nickel-containing lithium transition metal oxides is within the range of 5%-50%, the use of nickel-containing lithium transition metal oxides will cause the powder resistivity of the positive electrode active material to increase, resulting in a loss of discharge power performance of the battery cell. The present application further controls the internal resistance of the battery cell by controlling the powder resistivity of the positive electrode active material within 30-5000Ω·cm; further, by controlling the Ni content in the nickel-containing lithium transition metal oxide, the energy density of the battery cell is increased, thereby obtaining a battery cell with high energy density and good discharge power performance, and at the same time, the heating rate of the battery cell during charging can be alleviated to a certain extent. Moreover, the battery cell of the present application also has the advantages of good thermal stability, high safety, long life and low cost of lithium-containing phosphate-based positive electrode materials.

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

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

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

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

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

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

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

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

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

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

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

[0017] In any embodiment of the first aspect of the present application, the surface density of the positive electrode active layer is 200 mg / 1540.25 mm 2 -370mg / 1540.25mm 2 , optional: 240mg / 1540.25mm 2 -340mg / 1540.25mm 2 .

[0018] In any embodiment of the first aspect of the present application, the powder compaction density of the positive electrode material at 30000N is 2.5g / cm 3 -2.8g / cm 3 .

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

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

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

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

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

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

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

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

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

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

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

[0030] In any embodiment of the first aspect of the present application, the surface of the above-mentioned lithium-containing phosphate-based positive electrode material includes an ion-conducting material, and the ion-conducting material includes one or more of C element, Ti element, Zr element, Hf element, Ge element or Sn element.

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

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

[0033] In any embodiment of the first aspect of the present application, the positive electrode plate further includes a conductive layer, and the conductive layer is disposed between the positive electrode current collector and the positive electrode active layer.

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

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

[0036] In any embodiment of the first aspect of the present application, the surface density of the negative electrode active layer is 90 mg / 1540.25 mm 2-170 mg / 1540.25 mm 2 ; Optional: 110mg / 1540.25mm 2 -160mg / 1540.25mm 2 .

[0037] In any embodiment of the first aspect of the present application, the lithium-containing phosphate-based positive electrode material comprises a lithium iron phosphate material, and the battery cell is configured such that the compaction density of the negative electrode film layer corresponding to the 100% SOC state is 1.04 g / cm 3 -1.48g / cm 3 ; Optional: 1.23g / cm 3 -1.42g / cm 3 .

[0038] In any embodiment of the first aspect of the present application, the negative electrode plate further includes a negative electrode conductive layer, which is disposed between the negative electrode current collector and the negative electrode active layer, and has a thickness of 0.5 μm-3 μm, and may be 1 μm-2 μm.

[0039] In any embodiment of the first aspect of the present application, the thickness of the negative electrode current collector is 4 μm-7 μm, and can be 4 μm-5 μm.

[0040] In any embodiment of the first aspect of the present application, the above-mentioned carbon material includes composite graphite particles, and the composite graphite particles include: main particles, the main particles include primary particles and / or secondary particles, the main particles include artificial graphite; and a coating layer, the coating layer is coated on the surface of the main particles, and the coating layer includes amorphous carbon.

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

[0042] In any embodiment of the first aspect of the present application, the negative electrode active layer includes: a first negative electrode active layer, arranged on one side of the negative electrode current collector, the negative electrode material of the first negative electrode active layer includes one or more of composite graphite particles and natural graphite, the volume average particle size Dv50 of the negative electrode material in the first negative electrode active layer is 7.5μm-19.5μm, which can be optionally 12.5μm-18.5μm, and a second negative electrode active layer, arranged on the side of the first negative electrode active layer away from the negative electrode current collector, the negative electrode material of the second negative electrode active layer includes composite graphite particles, and the volume average particle size Dv50 of the negative electrode material in the second negative electrode active layer is 7.5μm-19.5μm, which can be optionally 7.5μm-15.5μm.

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

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

[0045] In any embodiment of the first aspect of the present application, the electrolyte includes lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI).

[0046] In any embodiment of the first aspect of the present application, the molar concentration ratio of the above-mentioned lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate is (2-5):10.

[0047] In any embodiment of the first aspect of the present application, the above-mentioned battery cell includes a shell, the electrode assembly is arranged in the shell, the positive electrode sheet and the negative electrode sheet are arranged in a stacked manner, the length of the shell is L1, the length of the positive electrode sheet is L2, L2 / L1 is 80%-99%, and preferably L2 / L1 is 88%-99%.

[0048] In any embodiment of the first aspect of the present application, the size of the shell has 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.

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

[0050] In any embodiment of the first aspect of the present application, the liquid injection coefficient of the above-mentioned battery monomer is 1.9g / Ah-3.1g / Ah, and can be optionally 2.4g / Ah-3.0g / Ah.

[0051] In any embodiment of the first aspect of the present application, the volume energy density of the above-mentioned battery monomer is greater than or equal to 400Wh / L, and can be optionally 400Wh / L-650Wh / L, and can be optionally 500-600Wh / L.

[0052] A second aspect of the present application provides a battery device, comprising a battery cell provided by any embodiment of the first aspect, wherein the battery device comprises a battery module, a battery pack or an energy storage device.

[0053] A second aspect of the present application provides an electrical device, comprising a battery cell provided by any embodiment of the first aspect, or a battery device provided by any embodiment of the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0055] Figure 1 It is a schematic diagram of a battery assembly according to one embodiment of the present application.

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

[0057] Figure 3 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0058] Figure 4 yes Figure 3 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0059] Figure 5 Schematic diagram of an electrical device using a battery pack according to an embodiment of the present application as a power source.

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

[0061] Description of reference numerals:

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

[0063] The following detailed description and drawings of the embodiments of the present application are used to illustrate the principles of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0064] Hereinafter, the battery cells, battery devices and power devices of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually 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 descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0065] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. 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 scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0066] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0067] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0068] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0069] If there is no special explanation, the "include" and "comprising" mentioned in this application represent open-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or comprised.

[0070] If not otherwise specified, in this 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 both A and B are true (or exist).

[0071] [Battery Cell]

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

[0073] During the charge and discharge process of the battery cell, lithium ions are inserted and removed back and forth between the positive electrode and the negative electrode. The separator is set between the positive electrode and the negative electrode, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing lithium ions to pass through.

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

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

[0076] In some embodiments, a powder resistance tester may be used to test the powder resistivity of the positive electrode material as follows:

[0077] For the positive electrode of the battery cell, DMC (dimethyl carbonate) is used to fully clean the positive electrode, and the positive electrode is dried and calcined before collecting the positive electrode material in the positive active layer. After the powder resistance tester is turned on and the equipment is stable, a certain mass of positive electrode material is weighed and added to the feeding chamber and the depth of the feeding chamber is adjusted. The target pressure is applied according to the target pressure and the area of ​​the cavity in the feeding chamber, and the powder resistivity test results under a pressure of 12MPa are collected.

[0078] In some embodiments, the mass content of the lithium-containing phosphate-based positive electrode material in the above positive electrode material is 50%-95%, and can be optionally 50%-70%. When the positive electrode material has the above mass content of the lithium-containing phosphate-based positive electrode material, the advantages of the phosphate-based positive electrode material are fully utilized and the volume energy density of the battery cell is increased while minimizing the internal resistance of the battery.

[0079] As the Ni content increases, the gram capacity of the nickel-containing lithium transition metal oxide increases. In some embodiments, based on the total molar amount of transition metal elements in the nickel-containing lithium transition metal oxide, the molar content of Ni in the nickel-containing lithium transition metal oxide is 50%-95%, optionally 70%-95%, and further optionally 75%-95%. The use of nickel-containing lithium transition metal oxides with high nickel content can further increase the gram capacity of the positive electrode active material, thereby further improving the energy density of the battery cell.

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

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

[0082] In some embodiments, the powder resistivity of the positive electrode material at 12 MPa is 80 Ω·cm-1500 Ω·cm, and can be optionally 140 Ω·cm-650 Ω·cm.

[0083] In some embodiments, the powder resistivity of the positive electrode material at 12 MPa is 30 Ω·cm-400 Ω·cm, and can be optionally 30 Ω·cm-120 Ω·cm.

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

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

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

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

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

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

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

[0091] The positive electrode sheet of the battery cell was fully cleaned with DMC (dimethyl carbonate), and the positive electrode sheet was dried and calcined before collecting the positive electrode material in the positive electrode active layer. The positive electrode material was tested using inductively coupled plasma atomic emission spectrometry (ICP-OES).

[0092] In order to further improve the energy density of the battery cell by setting the active layer structure, in some embodiments, the surface density of the positive electrode active layer is 200 mg / 1540.25 mm 2 -370mg / 1540.25mm 2 , optional: 240mg / 1540.25mm 2 -340mg / 1540.25mm 2 .

[0093] The above surface density is tested by the following method:

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

[0095] In some embodiments, if a positive electrode conductive layer is disposed between the positive electrode active layer and the positive electrode current collector, the mass of the positive electrode conductive layer is significantly lower than that of the positive electrode active layer, so when testing the compaction density or surface density of the positive electrode active layer, the mass of the positive electrode conductive layer can be ignored. The same is true for the compaction density or surface density test of the negative electrode active layer.

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

[0097] The positive electrode sheet of the battery cell was fully cleaned with DMC (dimethyl carbonate), and the positive electrode sheet was dried and calcined before collecting the positive electrode material in the positive electrode active layer. The powder compaction density of the positive electrode material under 30000N was tested.

[0098] The compaction density of the positive electrode active layer affects the stability of the electrolyte's wetting and volume expansion in the positive electrode plate, and also affects the volume 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 wettability of the electrolyte therein, and the smaller the buffer space reserved for the expansion of the positive electrode active material, thereby affecting the charging performance and cycle performance of the battery cell, but the volume energy density of the battery cell can be improved; the smaller the compaction density, the larger the pores between the positive electrode active material particles, the better the wettability of the electrolyte therein, and the larger the buffer space reserved for the expansion of the positive electrode material, thereby improving the charging performance and cycle performance of the battery cell, but causing a decrease in the volume energy density of the battery cell.

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

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

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

[0102] Based on the above surface density test, the thickness of the positive electrode active layer = the thickness of the positive electrode plate H1-the thickness of the positive electrode collector H0, and the compaction density of the positive electrode active layer = the single-sided coating weight of the positive electrode active layer / the single-sided thickness of the positive electrode active layer.

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

[0104] The specific surface area is a well-known meaning in the art and can be tested by methods known in the art. For example, for the positive electrode plate of the battery cell, DMC (dimethyl carbonate) is used to fully clean the positive electrode plate, and the positive electrode plate is dried and calcined, and the positive electrode material in the positive electrode active layer is collected. With reference to GB / T 19587-2017, the positive electrode material can be tested by the nitrogen adsorption specific surface area analysis test method, and calculated by the BET (Brunauer Emmett Teller) method, wherein the nitrogen adsorption specific surface area analysis test can be performed by the Tri-Star 3020 specific surface area pore size analysis tester of Micromeritics, USA.

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

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

[0107] Doping Al, B, Ti, Y, Zr, Sr and other elements into nickel-containing lithium transition metal oxides can significantly improve their electrochemical properties, structural stability and cycle performance. For example:

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

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

[0110] Ti doping can significantly improve the particle strength of nickel-containing lithium transition metal oxides and enhance the cycle performance. After Ti replaces the transition metal elements, the strong Ti-O bonds formed help stabilize the lattice structure and prevent adverse changes in the structure during the charge and discharge process. In addition, Ti doping can also broaden the insertion / extraction channels of Li ions and increase the transmission rate of Li ions.

[0111] Y doping is beneficial to improve the cycle stability and rate performance of nickel-containing lithium transition metal oxides. Y has a large ionic radius and can serve as a supporting framework after doping to inhibit surface structural phase change and Li / Ni mixing. In addition, Y doping can also broaden the transmission channel of Li ions and increase the transmission rate of Li ions.

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

[0113] Sr doping is usually 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 pillar, significantly expanding the lattice unit parameters and O-Li-O interlayer spacing, thereby improving the diffusion kinetics and rate performance of Li ions. Sr / Zr co-doping can also build a strong crystal framework and improve the structural stability and cycle performance of nickel-containing lithium transition metal oxides.

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

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

[0116] The lithium-containing phosphate-based positive electrode material used in the present application can adopt any one of the conventional materials of this type, for example, the lithium-containing phosphate-based positive electrode material includes a lithium iron manganese phosphate material, and the lithium iron manganese phosphate material contains one or more of the elements Al, B, Ca, Cr, Cu, K, Mg, Na, P, Si, Ti, V, and Zn; optionally, the lithium iron manganese phosphate material includes one or more of the elements Al, Ca, Na, Ti, and V. The elements in the above materials can be present in the lithium-containing phosphate-based positive electrode material in the form of doping or coating. Among them, the Al element can reduce the resistivity of the material, change the crystal structure, shorten the lithium ion transmission path, 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 conductivity and cycle stability of the material, and the Ti element can change the crystal structure and improve the charge and discharge performance of the material.

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

[0118] In some embodiments, the positive electrode active layer contains lithium iron manganese phosphate material and nickel cobalt manganese oxide material, and the positive electrode material contains one or more of Al, Ca, Na, Ti, V, Zr, and B elements, and based on the positive electrode material, the mass content of each element 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%.

[0119] In some embodiments, the lithium-containing phosphate-based positive electrode material includes a lithium iron manganese phosphate material, in which the molar ratio of Mn to Fe is 2:8 to 8:2, and can be optionally 5:5 to 7:3. The appropriate molar ratio range of Mn to Fe is helpful for comprehensively regulating the voltage platform, transition metal dissolution problems, gas production problems during the cycle, etc. of the lithium iron manganese phosphate material. The cycle performance of the lithium iron manganese phosphate with the above molar ratio is relatively stable, and is beneficial to improving the energy density of the battery cell.

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

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

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

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

[0124] Through the above-mentioned particle size control, the small-particle lithium-containing phosphate-based positive electrode material and the large-particle nickel-containing lithium transition metal oxide are combined, and the small particles can fill the gaps between the large particles, thereby improving the compaction of the positive electrode active material; and this combination method protects the lithium-containing phosphate-based positive electrode material, effectively reducing the probability of breakage when it is cold pressed at the same pressure.

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

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

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

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

[0129] In order to improve the rate performance of the battery cell, in some embodiments, the positive electrode plate further includes a conductive layer, which is disposed between the positive current collector and the positive active layer. The conductive layer is used to increase the electron transfer rate, thereby improving the rate performance of the battery cell.

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

[0131] In some embodiments, the thickness of the conductive layer is 0.5 μm-2 μm, so that the conductive layer can be fully utilized to improve the conductivity, and the influence of the conductive layer thickness on the energy density of the battery cell is avoided.

[0132] The strength of the positive electrode current collector is related to its thickness. Generally, the greater the thickness, the greater the strength. However, the greater the strength, the worse the ductility, and it will also cause the energy density of the battery cell to decrease. During the charge and discharge cycle, the positive electrode active material expands and contracts, and the greater the surface density of the positive electrode active layer, the more obvious the volume expansion and contraction of the positive electrode active layer. Therefore, the positive electrode current collector requires both a certain strength to restrain the expansion and a certain ductility to adapt to the increase in area of ​​the active layer caused by the expansion. In some embodiments, the thickness of the positive electrode current collector is 9μm-17μm, and can be optionally 10μm-13μm. The positive electrode current collector within this thickness range has little effect on the energy density, and it has a good matching ability of strength and ductility, thereby effectively reducing the risk of cracking of the current collector caused by the expansion of the battery cell during the charging process.

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

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

[0135] In some embodiments, the positive electrode active layer may further include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0136] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0137] [Negative electrode]

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

[0139] In some embodiments, the battery cell is configured such that the compaction density of the negative electrode film layer corresponding to the 100% SOC state is 1.04 g / cm 3 -1.48g / cm 3 ; Optional: 1.23g / cm 3 -1.42g / cm 3 The negative electrode sheet with the above compaction density has small expansion deformation and good electrolyte infiltration, thereby improving the cycle performance of the battery cell.

[0140] In some embodiments, the negative electrode plate further includes a negative electrode conductive layer, which is disposed between the negative electrode current collector and the negative electrode active layer, and has a thickness of 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 plate, thereby improving the rate performance of the battery cell.

[0141] The same considerations as above for selecting the thickness of the positive electrode current collector, in some embodiments, the thickness of the negative electrode current collector is 4μm-7μm, and can be 4μm-5μm. The negative electrode current collector within this thickness range has little effect on the energy density, and has good strength and ductility matching capabilities, thereby effectively reducing the risk of current collector cracking caused by expansion during the charging process of the battery cell.

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

[0143] On the basis of improving the conductivity of the composite graphite particles, the gram 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.

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

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

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

[0147] In order to maximize the contribution of the second negative electrode 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 20000N is 1.5g / cm 3 -1.85g / cm 3 , or 1.55g / cm 3 -1.75g / cm 3 .

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

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

[0150] In some embodiments, the negative electrode film layer may further include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0151] In some embodiments, the negative electrode conductive layer includes a negative electrode binder and a negative electrode conductive material, wherein the negative electrode binder and the negative electrode conductive material can be selected from the binder and the conductive agent in the negative electrode film layer.

[0152] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0153] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0154] [Isolation film]

[0155] The present application has no particular limitation on the type of isolation membrane, and any known porous isolation membrane with good chemical stability and mechanical stability can be selected.

[0156] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0157] In some embodiments, the isolation membrane includes a porous base membrane and a functional layer disposed on at least one side of the porous base membrane. That is, the isolation membrane is a composite film. The corresponding functional layer is selected according to different functional requirements, and this application will not repeat it here.

[0158] [Electrolytes]

[0159] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0160] In some embodiments, the battery cell further includes an electrolyte solution including an electrolyte salt and a solvent.

[0161] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0162] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl 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, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0163] In some embodiments, the electrolyte may further include additives. As examples, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

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

[0165] In some embodiments, the electrolyte includes lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI). Lithium bis(fluorosulfonyl)imide can improve the lithium ion transfer rate, thereby improving the charging rate of the battery cell; and it has high temperature stability, thereby improving the high temperature cycle performance of the battery cell.

[0166] In some embodiments, the molar concentration ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate is (2-5): 10. Thus, the above lithium salt is used to improve the cycle stability and charging rate of the battery monomer, while controlling the excessive increase in the cost of the battery monomer.

[0167] In some embodiments, the types and contents of the inorganic components / lithium salt concentrations in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, the inorganic components / lithium salt concentrations in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis methods with reference to standard JY / T020-1996 "General Rules for Ion Chromatography Analysis Methods".

[0168] In the embodiments of the present application, a newly prepared electrolyte can be taken as a sample, or a battery that has been fully discharged (discharged to the lower limit cut-off voltage so that the battery's charged state is approximately 0% SOC) can be reversely disassembled, and the free electrolyte obtained from the battery can be used as a sample for detection using an ion chromatography analysis method.

[0169] In the embodiments of the present application, the type and content of the organic components in the electrolyte are well-known in the art, and can be detected by using equipment and methods well-known in the art. For example, reference can be made to GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" to perform qualitative and quantitative analysis of the organic components in the electrolyte by gas chromatography. In the embodiments of the present application, a newly prepared electrolyte can be taken as a sample, or a battery that has been fully discharged (discharged to the lower limit cut-off voltage so that the battery's charged state is about 0% SOC) can be reversely disassembled, and the free electrolyte obtained from the battery can be used as a sample, and the ion chromatography analysis method can be used for detection.

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

[0171] Thereby further improving the volume energy density of the battery cell.

[0172] In some embodiments, the dimensions of the housing have one or more of the following characteristics:

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

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

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

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

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

[0178] In some embodiments, the battery cell filling factor is 1.9 g / Ah-3.1 g / Ah.

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

[0180] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0181] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. For example, Figure 1 The electrode assembly 52 is an example of a battery cell having a square structure.

[0182] In some embodiments, reference Figure 2 , the outer packaging may include a shell 51 and a top cover assembly 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

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

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

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

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

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

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

[0189] Figure 3 and Figure 4 1 is a battery pack 1 as an example. Figure 3 and Figure 4 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0190] In addition, the present application also provides an electric device, which includes a battery cell or a battery device provided in the present application. The battery cell or the battery device can be used as a power source for the electric device, or as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0191] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

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

[0193] [Example]

[0194] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0195] Positive electrode

[0196] The positive electrode active layer includes positive electrode active material, binder polyvinylidene fluoride, conductive agent acetylene black (mass ratio is 96.7:2.3:1.0), the current collector aluminum foil thickness is 13μm, the positive electrode active layer is located on both sides of the aluminum foil, and there is a positive electrode conductive layer between the positive electrode active layer and the aluminum foil. The positive electrode conductive layer is a film layer formed by mixing the positive electrode conductive agent superconducting carbon, the positive electrode binder polyacrylate and the solvent evenly and then coating it on the surface of the positive electrode collector and drying it. The thickness is 1μm, 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 positive electrode conductive layer is 50%. The length of the positive electrode sheet is 592mm.

[0197] Negative electrode

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

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

[0200] Electrolyte

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

[0202] Isolation film

[0203] A polyethylene (PE) film coated with nano-aluminum oxide was used as the isolation film.

[0204] Battery Cell

[0205] The electrode assembly is obtained by stacking the positive electrode sheet, the separator and the negative electrode sheet. The electrode assembly is added to the outer packaging square aluminum shell (length 600mm, thickness 19mm, height 105mm), and the electrolyte is injected after drying, and the injection coefficient is 2.9. After packaging, high temperature standing, formation, secondary injection, aging, capacity and other processes, a battery cell is obtained.

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

[0207] The powder resistivity in Table 1 is the powder resistivity of the material at 12 MPa. Table 1 In addition to the elements in the chemical formula, there are other elements M in the nickel-containing lithium transition metal oxide. The subscripts of Ni, Co and Mn in the chemical formula are rounded data. Because the content of other elements M is trace, these elements and their atomic numbers are not reflected in the chemical formula. It does not mean that element M has no effect on battery performance. The content of other elements M is explained below. The chemical formula is LiNi 0.8 Co0.1 Mn 0.1 The contents of other elements in the nickel-containing lithium transition metal oxide of O2 are 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 0.6 Co 0.2 Mn 0.2 The contents of other elements in the nickel-containing lithium transition metal oxide of O2 are as follows: the mass content of Al is 0.04%, the mass content of B is 0.0028%, the mass content of Ti is 0.0003%, the mass content of Y is 0.0076%, the mass content of Zr is 0.24%, and the mass content of Sr is 0.0001%; ​​the chemical formula is LiNi 0.9 Co 0.05 Mn 0.05 The contents of other elements in the nickel-containing lithium transition metal oxide of O2 are as follows: the mass content of Al is 0.068%, the mass content of B is 0.0033%, the mass content of Ti is 0.0003%, the mass content of Y is 0.008%, the mass content of Zr is 0.21%, and the mass content of Sr is 0.0001%; ​​the chemical formula is LiNi 0.4 Co 0.2 Mn 0.4 The contents of other elements in the nickel-containing lithium transition metal oxide of O2 are as follows: the mass content of Al is 0.036%, the mass content of B is 0.003%, the mass content of Ti is 0.0003%, the mass content of Y is 0.0079%, the mass content of Zr is 0.25%, and the mass content of Sr is 0.0001%.

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

[0209] Material Testing:

[0210] Powder resistivity test method for positive electrode materials:

[0211] For the positive electrode of the battery cell, DMC (dimethyl carbonate) is used to fully clean the positive electrode, and the positive electrode is dried and calcined before collecting the positive electrode material in the positive active layer. After the powder resistance tester is turned on and the equipment is stable, a certain mass of positive electrode material is weighed and added to the feeding chamber and the depth of the feeding chamber is adjusted. The target pressure is applied according to the target pressure and the area of ​​the cavity in the feeding chamber, and the powder resistivity test results under a pressure of 12MPa are collected.

[0212] BET specific surface area test method for positive electrode materials:

[0213] For the positive electrode sheet of the battery cell, DMC (dimethyl carbonate) is used to fully clean the positive electrode sheet, and the positive electrode sheet is dried and calcined to collect the positive electrode material in the positive electrode active layer. Referring to GB / T 19587-2017, the positive electrode material is tested by the nitrogen adsorption specific surface area analysis test method, and calculated by the BET (Brunauer Emmett Teller) method, wherein the nitrogen adsorption specific surface area analysis test can be performed by the Tri-Star 3020 specific surface area pore size analysis tester of Micromeritics, USA.

[0214]

[0215] test:

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

[0217] Test methods for surface density and compacted density:

[0218] Take a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, wipe off the positive electrode film layer on one side first), punch it into small discs with an area of ​​S1, weigh it, record it as M1, and measure its thickness H1. Then wipe off the positive active layer of the weighed positive electrode sheet, weigh the weight of the positive current collector, record it as M0, and measure its thickness H0. The single-sided coating weight of the positive active layer (also known as the surface 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 positive electrode sheet H1-the thickness of the positive current collector H0, the compacted 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. The positive active layer in the above test includes the positive active layer and the positive conductive layer in the aforementioned positive electrode sheet).

[0219] Volume energy density test method:

[0220] The battery cell is placed at 25°C, charged to 4.2V at a constant current of 0.33C, and then charged to 0.05C at a constant voltage; discharged to 2.5V at a constant current of 0.33C, and the discharge energy A0 at this time is obtained, in units of Wh; the length, width, and height of the battery cell are measured with a caliper (generally calculated based on the outer shell size of the battery, excluding the height of the electrode terminals and the insulating film outside the outer shell), and the volume V0 of the battery cell is calculated, in units of L; the volume energy density of the battery cell is VED = A0 / V0, in units of Wh / L.

[0221] DC internal resistance DCR test of battery cells

[0222] You can refer to the method in GB / T 31467 "Performance Test Specification for High Power Lithium-ion Power Batteries for HEV". The details are as follows:

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

[0224] After the battery cell is placed at 25°C for 2 hours, it is discharged at a constant current of 2C for 10 seconds, and ΔU discharge and ΔI discharge are recorded. The discharge DCR data of the lithium-ion battery is calculated by the following formula: R discharge = ΔU discharge / ΔI discharge,

[0225] Here, ΔUdischarge represents the voltage change within 10 seconds after the start of discharge, and ΔIdischarge represents the current value within 10 seconds after the start of discharge.

[0226] Cycle life test method:

[0227] The number of cycles of the battery cell to 80% SOH:

[0228] At 45°C, charge the battery cell at 1C constant current to a charge cutoff voltage of 4.2V, and then discharge it at 1C constant current to 2.0V. This is a charge and discharge cycle. Repeat the above charge and discharge cycle steps until the cycle capacity retention rate (i.e. Cn / C0×100%) 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). Record the number of cycles. The more cycles, the better the cycle performance of the battery cell.

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

[0230] According to the comparison between Examples 2 to 14 and Comparative Example 1, it can be seen that the energy density and cycle performance of the battery cell can be improved by mixing lithium manganese iron phosphate with nickel-containing lithium transition metal oxide.

[0231] According to the comparison of Comparative Example 2, Example 13 and Example 14, it can be seen that when the content of lithium iron manganese phosphate in the positive electrode material is reduced to below 50%, although the energy density of the battery cell increases due to the increase in the lithium content of the nickel-containing lithium transition metal oxide, the internal resistance of the battery cell is significantly larger.

[0232] According to the comparison between Comparative Example 3, Example 13 and Example 14, it can be seen that by adjusting the powder resistivity of the nickel-containing lithium transition metal oxide to control the powder resistivity of the positive electrode material below 5000Ω·cm, it is beneficial to reduce the internal resistance of the battery cell.

[0233] According to the comparison between Comparative Example 4 and Examples 9 to 14, it can be seen that when the nickel content in the nickel-containing lithium transition metal oxide is less than 30%, not only the powder resistivity of the positive electrode material is higher, resulting in a higher DCR internal resistance of the battery device, but also the energy density of the battery device is affected.

[0234] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there are no structural conflicts. 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, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet, and a separator 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 disposed on at least one side of the negative electrode current collector, wherein the negative electrode active layer comprises a negative electrode material, and the negative electrode material comprises a carbon material; The positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active layer comprises a positive electrode material, and the positive electrode material comprises a lithium-containing phosphate-based positive electrode material and a nickel-containing lithium transition metal oxide. The mass content of the nickel-containing lithium transition metal oxide in the positive electrode material is 5%-50%, and the mass content of Ni in the nickel-containing lithium transition metal oxide is greater than or equal to 30%; The powder resistivity of the positive electrode material at 12 MPa is 30 Ω·cm-5000 Ω·cm.

2. The battery cell according to claim 1, wherein: The mass content of the lithium-containing phosphate-based positive electrode material in the positive electrode material is 50%-95%, and can be optionally 50%-70%.

3. The battery cell according to claim 1 or 2, wherein: Based on the total molar amount of transition metal elements in the nickel-containing lithium transition metal oxide, the molar content of Ni in the nickel-containing lithium transition metal oxide is 75%-95%.

4. The battery cell according to any one of claims 1 to 3, wherein: The powder resistivity of the positive electrode material at 12 MPa is 30 Ω·cm-2000 Ω·cm.

5. The battery cell according to any one of claims 1 to 4, wherein: The powder resistivity of the positive electrode material at 12 MPa is 30 Ω·cm-1500 Ω·cm.

6. The battery cell according to any one of claims 1 to 5, wherein: The powder resistivity of the positive electrode material at 12 MPa is 80 Ω·cm-1500 Ω·cm.

7. The battery cell according to any one of claims 1 to 6, wherein: The powder resistivity of the positive electrode material at 12 MPa is 30 Ω·cm-400 Ω·cm.

8. The battery cell according to any one of claims 1 to 7, wherein: The powder resistivity of the nickel-containing lithium transition metal oxide at 12 MPa is 100 Ω·cm-10000 Ω·cm, optionally 100 Ω·cm-5000 Ω·cm, and further optionally 100-4000 Ω·cm.

9. The battery cell according to any one of claims 1 to 8, wherein: The powder resistivity of the phosphate-based positive electrode material at 12 MPa is 4-80Ω·cm.

10. The battery cell according to any one of claims 1 to 9, wherein: Based on the total mass of the positive electrode material, the mass content of the Ni element is 1.7%-26.5%, and can be optionally 10%-23.5%.

11. The battery cell according to any one of claims 1 to 10, wherein: The lithium-containing phosphate-based positive electrode material includes lithium manganese iron phosphate material. Based on the total mass of the positive electrode material, the mass content of Fe element is 4.5%-17%, and can be optionally 4.5%-10.3%.

12. The battery cell according to any one of claims 1 to 11, wherein: The lithium-containing phosphate-based positive electrode material comprises lithium manganese iron phosphate material, and based on the total mass of the positive electrode material, the mass content of Mn element is 3.4%-22.5%.

13. The battery cell according to any one of claims 1 to 12, wherein: The surface density of the positive electrode active layer is 200 mg / 1540.25 mm 2 -370mg / 1540.25mm 2 , optional: 240mg / 1540.25mm 2 -340mg / 1540.25mm 2 .

14. The battery cell according to any one of claims 1 to 13, wherein: The powder compaction density of the positive electrode material at 30000N is 2.5g / cm 3 -2.8g / cm 3 .

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

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

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

18. The battery cell according to any one of claims 1 to 17, wherein: The nickel-containing lithium transition metal oxide includes one or more of a lithium-containing nickel-cobalt-manganese oxide material and a lithium-containing nickel-cobalt-aluminum oxide material.

19. The battery cell according to any one of claims 1 to 18, wherein: The nickel-containing lithium transition metal oxide includes lithium-containing nickel-cobalt-manganese oxide, and the lithium-containing nickel-cobalt-manganese oxide material contains at least one of the elements Zr, Al, B, Fe, Ca, Sr, Ti, V, and Y.

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

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

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

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

3.

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

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

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

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

29. The battery cell according to any one of claims 1 to 28, wherein: The positive electrode plate further includes a conductive layer, and the conductive layer is disposed between the positive electrode current collector and the positive electrode active layer.

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

31. The battery cell according to any one of claims 1 to 30, wherein: The thickness of the positive electrode current collector is 9 μm-17 μm, and can be 10 μm-13 μm.

32. The battery cell according to any one of claims 1 to 31, wherein: The surface density of the negative electrode active layer is 90 mg / 1540.25 mm 2 -170 mg / 1540.25 mm 2 ; Optional: 110mg / 1540.25mm 2 -160mg / 1540.25mm 2 .

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

34. The battery cell according to any one of claims 1 to 33, wherein: The negative electrode plate further includes a negative electrode conductive layer, which is disposed between the negative electrode current collector and the negative electrode active layer. The thickness of the negative electrode conductive layer is 0.5 μm-3 μm, and can be optionally 1 μm-2 μm.

35. The battery cell according to any one of claims 1 to 34, wherein: The thickness of the negative electrode current collector is 4 μm-7 μm, and can be 4 μm-5 μm.

36. The battery cell according to any one of claims 1 to 36, wherein: The carbon material includes composite graphite particles, and the composite graphite particles include: Main particles, the main particles comprising primary particles and / or secondary particles, the main particles comprising artificial graphite; and The coating layer is coated on the surface of the main particle, and the coating layer includes amorphous carbon.

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

38. The battery cell according to claim 39, wherein: The negative electrode active layer comprises: A first negative electrode active layer is disposed on one side of the negative electrode current collector, wherein the negative electrode material of the first negative electrode active layer comprises one or more of composite graphite particles and natural graphite, and optionally the volume average particle size Dv50 of the negative electrode material in the first negative electrode active layer is 7.5 μm-19.5 μm, and optionally 12.5 μm-18.5 μm, and The second negative electrode active layer is arranged on the side of the first negative electrode active layer away from the negative electrode current collector. The negative electrode material of the second negative electrode active layer includes composite graphite particles. Optionally, the volume average particle size Dv50 of the negative electrode material in the second negative electrode active layer is 7.5μm-19.5μm, and can be optionally 7.5μm-15.5μm.

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

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

41. The battery cell according to claim 40, wherein: The electrolyte includes lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, and the molar concentration ratio between the lithium bis(fluorosulfonyl)imide and the lithium hexafluorophosphate is (2-5):

10.

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

43. The battery cell according to claim 42, 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 housing is 85 mm to 140 mm; The thickness of the shell is 10mm-20mm.

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

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

46. ​​The battery cell according to claims 42 to 45, wherein: The volume energy density of the battery cell is greater than or equal to 400Wh / L, and can be selected as 400Wh / L-650Wh / L, and can be selected as 500-600Wh / L.

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

48. An electrical device comprising the battery cell according to any one of claims 1 to 46, or the battery device according to claim 47.

Images