Battery cell, battery assembly and electric device

Abstract

Disclosed in the present application are a battery cell, a battery assembly and an electric device. The battery cell comprises a positive electrode sheet and a negative electrode sheet, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer arranged on at least one side of the negative electrode current collector, the negative electrode active layer comprises a negative electrode material, and the negative electrode material comprises graphite; and the positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer arranged on at least one side of the positive electrode current collector, the positive electrode active layer comprises a positive electrode material, the positive electrode material comprises a positive electrode active material, the positive electrode active material comprises a lithium manganese iron phosphate material and a lithium iron phosphate material, the lithium manganese iron phosphate material accounts for 50-95% by mass of the positive electrode active material, and the powder resistivity of the positive electrode material at 12 MPa is 5-70 Ω·cm. The energy density and power performance of the battery cell of the present application are both improved.

Description

Battery cell, battery device, and electric device

[0001] This application is based on Chinese Patent Application No. 202411291538.2, filed on September 14, 2024, and Chinese Patent Application No. 202411087332.8, filed on August 8, 2024, for which priority is claimed, and the contents of all of the aforementioned applications are hereby incorporated by reference in their entirety. TECHNICAL FIELD

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

[0003] In recent years, with the increasingly wide range of applications of batteries, batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind, and solar power stations, as well as in electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. Due to the great development of batteries, higher requirements are placed on their energy density and power performance. SUMMARY

[0004] The present application is made in view of the above-mentioned problems, and aims to provide a battery cell, a battery device, and an electric device. The energy density and power performance of the battery cell of the present application are simultaneously improved.

[0005] To achieve the above-mentioned purpose, the first aspect of the present application provides a battery cell, comprising a positive electrode sheet and a negative electrode sheet; wherein,

[0006] The negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer arranged on at least one side of the negative electrode current collector, the negative electrode active layer comprising a negative electrode material, and the negative electrode material comprising graphite;

[0007] The positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer arranged on at least one side of the positive electrode current collector, the positive electrode active layer comprising a positive electrode material, and the positive electrode material comprising a positive electrode active material;

[0008] The positive electrode active material comprises a lithium manganese iron phosphate material and a lithium iron phosphate material, the mass fraction of the lithium manganese iron phosphate material in the positive electrode active material being 50%-95%, and the powder resistivity of the positive electrode material under 12 MPa being 5-70 Ω·cm.

[0009] The platform voltage of the lithium manganese iron phosphate material is higher than that of the lithium iron phosphate material, and increasing the content of the lithium manganese iron phosphate material in the mixed system is beneficial to improve the energy density of the battery cell. However, the powder resistivity of the lithium manganese iron phosphate material is larger than that of the lithium iron phosphate material, which is easy to cause the powder resistivity of the mixture to be too large and deteriorate the power performance of the battery cell. The present application controls the ratio of the lithium manganese iron phosphate material and the lithium iron phosphate material to make the battery cell have a higher energy density, and further adjusts the powder resistivity range of the positive electrode material to improve the energy density and the power performance of the battery cell.

[0010] In any embodiment, the mass ratio of the lithium manganese iron phosphate material in the positive electrode active material is 50%-70%.

[0011] Therefore, it is beneficial to improve the energy density and the power performance of the battery cell at the same time. Moreover, when the mass ratio of the lithium manganese iron phosphate material in the positive electrode active material is in the above range, the energy density of the battery cell is further improved; when the mass ratio of the lithium manganese iron phosphate material in the positive electrode active material is in the above range, the power performance of the battery cell is further improved.

[0012] In any embodiment, the powder resistivity of the lithium manganese iron phosphate material under 12 MPa is 8-120 Ω·cm, which can be 8-80 Ω·cm.

[0013] In any embodiment, the volume average particle size Dv50 of the lithium manganese iron phosphate material is 0.1-1.2 μm, which can be 0.2-0.8 μm.

[0014] Therefore, the powder resistivity and the volume average particle size Dv50 of the lithium manganese iron phosphate material in the above range are beneficial to improve the power performance of the battery cell while improving the energy density of the battery cell.

[0015] In any embodiment, the molar ratio of manganese atoms to iron atoms in the lithium manganese iron phosphate material is 2:8-8:2.

[0016] In any embodiment, the powder resistivity of the lithium iron phosphate material under 12 MPa is 3-100 Ω·cm, which can be 3-20 Ω·cm.

[0017] In any embodiment, the volume average particle size Dv50 of the lithium iron phosphate material is 0.9-1.9 μm.

[0018] In any embodiment, the areal density of the positive electrode active layer of the battery cell under 100% SOC state is 200-450 mg / 1540.25 mm 2 , which can be 290-350 mg / 1540.25 mm 2Thus, the power performance of the battery cell meets the demand, and the energy density of the battery cell is improved.

[0019] In any embodiment, the compaction density of the positive electrode active layer of the battery cell is 2.27-2.67 g / cm 3 , optionally 2.37-2.62 g / cm 3 Thus, the power performance meets the demand, and the energy density of the battery cell is improved.

[0020] In any embodiment, the surface density of the negative electrode active layer of the battery cell is 100-180 mg / 1540.25 mm 2 Thus, the power performance meets the demand, and the energy density of the battery cell is improved.

[0021] In any embodiment, the compaction density of the negative electrode active layer of the battery cell is 1.2-1.45 g / cm 3 , optionally 1.28-1.44 g / cm 3 Thus, the power performance meets the demand, and the energy density of the battery cell is improved.

[0022] In any embodiment, the negative electrode material further comprises a silicon material.

[0023] In any embodiment, the silicon-containing material comprises one or more of a silicon oxide compound, a silicon carbon compound; and / or,

[0024] The mass percentage of the silicon element is 0.3%-10%, optionally 1%-6%, based on the mass of the negative electrode material.

[0025] Thus, the power performance meets the demand, and the energy density of the battery cell is improved.

[0026] In any embodiment, the chemical formula of the lithium iron phosphate material is Li x Fe (1-s) M s P y O z , wherein x is greater than or equal to 0.5 and less than or equal to 1.3, s is greater than or equal to 0 and less than 1, y is greater than or equal to 0.5 and less than or equal to 1.3, z is greater than or equal to 3 and less than or equal to 5, M comprises one or more elements selected from B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Hf, Ni, Co, Ru, Ag, Pb; and / or,

[0027] The chemical formula of the lithium manganese iron phosphate material is Li x Fe (1-t-s) Mn t M s P y O z , wherein x is greater than or equal to 0.5 and less than or equal to 1.3, t is greater than 0 and less than 1, s is greater than or equal to 0 and less than 1, 1-t-s is greater than 0 and less than 1, y is greater than or equal to 0.5 and less than or equal to 1.3, z is greater than or equal to 3 and less than or equal to 5, and M includes one or more elements selected from the group consisting of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Hf, Ni, Co, Ru, Ag, Pb.

[0028] In any embodiment, the powder compaction density of the positive electrode material is 2.2-2.8 g / cm 3 , and optionally 2.3-2.8 g / cm 3 .

[0029] In any embodiment, the positive electrode sheet further includes a positive electrode conductive layer, and the positive electrode conductive layer is arranged between the positive electrode current collector and the positive electrode active layer.

[0030] In any embodiment, the thickness of the positive electrode conductive layer is 0.5-2 μm.

[0031] In any embodiment, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0032] In any embodiment, the battery cell includes one or more of:

[0033] The positive electrode conductive agent includes one or more of super conductive carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0034] The positive electrode conductive agent includes at least super conductive carbon and carbon nanotubes.

[0035] The positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, a polyacrylic acid, and a fluorine-containing acrylic ester resin.

[0036] In any embodiment, the mass percentage of the positive electrode conductive agent is 30%-50% based on the mass of the positive electrode conductive layer; and / or,

[0037] The mass percentage content of the cathode binder is 50%-70% based on the mass of the cathode conductive layer.

[0038] In any embodiment, the anode sheet further comprises an anode conductive layer, which is arranged between the anode current collector and the anode active layer.

[0039] In any embodiment, the thickness of the anode conductive layer is 0.5-2 μm.

[0040] In any embodiment, the anode conductive layer comprises one or more of an anode conductive agent, an anode binder.

[0041] In any embodiment, the anode conductive agent comprises one or more of super conductive carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers; and / or,

[0042] The anode binder comprises one or more of styrene butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate, carboxymethyl chitosan.

[0043] In any embodiment, the mass percentage content of the anode conductive agent is 20%-40% based on the mass of the anode conductive layer; and / or,

[0044] The mass percentage content of the anode binder is 60%-80% based on the mass of the anode conductive layer.

[0045] In any embodiment, the anode active layer is a single-layer or multi-layer structure, and the volume average particle size Dv50 of the anode active material in the anode active layer is 7.5-19.5 μm.

[0046] In any embodiment, the anode active layer is a single-layer structure, and the volume average particle size Dv50 of the anode active material is 8.0-17.5 μm.

[0047] In any embodiment, the anode active layer comprises a first anode active layer close to the anode current collector and a second anode active layer arranged on the first anode active layer.

[0048] In any embodiment, the thickness ratio of the second anode active layer to the first anode active layer is 2:8-8:2.

[0049] In any embodiment, the volume average particle size Dv50 of the anode active material in the first anode active layer is 7.5-19.5 μm, and optionally 12.5-18.5 μm.

[0050] In any embodiment, the volume average particle size Dv50 of the negative active material in the second negative active layer is 7.5-19.5 μm, optionally 7.5-15.5 μm.

[0051] In any embodiment, the volume average particle size Dv50 of the negative active material in the second negative active layer is less than the volume average particle size Dv50 of the negative active material in the first negative active layer. Thereby, the power performance of the battery cell is improved, while the energy density of the battery cell is increased and the cost is reduced.

[0052] In any embodiment, the graphite in the first negative active layer is selected from one or more of natural graphite, composite graphite; and / or,

[0053] The graphite in the second negative active layer is selected from one or more of composite graphite.

[0054] In any embodiment, the composite graphite comprises a body and a coating layer coated on the surface of the body; the body comprises artificial graphite, and the coating layer comprises amorphous carbon.

[0055] In any embodiment, the composite graphite comprises secondary particles.

[0056] In any embodiment, the powder resistivity of the composite graphite at 8 MPa is 0.01-0.04 Ω·cm.

[0057] In any embodiment, the battery cell further comprises an electrolyte, and the conductivity of the electrolyte at normal temperature is 10-20 mS / cm or 12-17 mS / cm.

[0058] In any embodiment, the volume energy density of the battery cell is 400-550 Wh / L or 450-500 Wh / L.

[0059] The second aspect of the present application further provides a battery device comprising the battery cell of the first aspect of the present application; the battery device comprises a battery module, a battery pack or an energy storage device.

[0060] The third aspect of the present application further provides a power utilization device comprising the battery cell of the first aspect of the present application or the battery device of the second aspect of the present application.

[0061] The present application further relates to the following aspects:

[0062] 1.A battery cell comprising an electrode assembly, the electrode assembly comprising a positive electrode tab and a negative electrode tab; the positive electrode tab comprising a positive current collector and a positive active layer disposed on at least one side of the positive current collector, the positive active layer comprising a positive material, the positive material comprising a positive active material; the negative electrode tab comprising a negative current collector and a negative active layer disposed on at least one side of the negative current collector, the negative active layer comprising a negative material, the negative material comprising a negative active material;

[0063] the positive active material comprising at least two lithium-containing phosphates, at least one of which is a first manganese-containing phosphate, the mass fraction of manganese atoms in the first phosphate being 10%-28%; the mass fraction of manganese atoms in the positive material being 6.27%-25.64%; the powder resistivity of the positive material at 12MPa being 2-110Ω·cm;

[0064] the negative active material comprising graphite; the areal density of the negative active layer being 100-180mg / 1540.25mm 2 .

[0065] 2.The battery cell according to the first aspect, the powder resistivity of the positive material at 12MPa being 5-70Ω·cm.

[0066] 3.The battery cell according to the first or second aspect, the mass fraction of the first phosphate in the positive active material being 50%-95%.

[0067] 4.The battery cell according to any one of the first to third aspects, the areal density of the positive active layer being 200-450mg / 1540.25mm 2 or 290-350mg / 1540.25mm 2 .

[0068] 5.The battery cell according to any one of the first to fourth aspects, the powder resistivity of the first phosphate at 12MPa being 10-120Ω·cm or 10-80Ω·cm.

[0069] 6.The battery cell according to any one of the first to fifth aspects, the full charge state of the battery being the state reached when charged at 0.33C to 4.1V and then at 4.1V to a current less than 0.05C at 25℃; the compacted density of the negative active layer at the full charge state being 1.2-1.45g / cm 3 or 1.28-1.44g / cm 3 .

[0070] 7.The battery cell according to any one of the first to sixth aspects, the compacted density of the positive active layer after cold pressing being 2.3-2.7g / cm3 or 2.4-2.65g / cm 3 .

[0071] 8. The battery cell according to any one of aspects 1 to 7, wherein the full charge state of the battery is a state reached when the battery is charged at 0.33C to 4.1V and then charged at 4.1V to a current less than 0.05C at 25°C; and wherein the compaction density of the positive electrode active layer is 2.27-2.67g / cm 3 or 2.37-2.62g / cm 3 .

[0072] 9. The battery cell according to any one of aspects 1 to 8, wherein the lithium-containing phosphate has a chemical formula of Li x Fe (1-t-s) Mn t M s P y O z , wherein each of x is independently greater than or equal to 0.5 and less than or equal to 1.3, each of t is independently greater than or equal to 0 and less than or equal to 1, each of s is independently greater than or equal to 0 and less than 1, each of y is independently greater than or equal to 0.5 and less than or equal to 1.3, each of z is independently greater than or equal to 3 and less than or equal to 5, and each of M independently comprises one or more elements selected from B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Hf, Ni, Co, Ru, Ag, Pb; and / or,

[0073] The lithium-containing phosphate has an olivine structure.

[0074] 10. The battery cell according to any one of aspects 1 to 9, wherein the first phosphate has a volume average particle size Dv50 of 0.1-1.2μm or 0.2-0.8μm.

[0075] 11. The battery cell according to any one of aspects 1 to 10, wherein at least one lithium-containing phosphate in the positive electrode active material further comprises iron atoms; and wherein the mass percentage of the iron atoms in the positive electrode material is 7.5%-30% or 6%-25%.

[0076] 12. The battery cell according to any one of aspects 1 to 11, wherein the first phosphate further comprises iron atoms; and wherein the mass percentage of the iron atoms in the first phosphate is 7%-25% or 13%-27%.

[0077] 13. The battery cell according to any one of aspects 1 to 12, wherein the at least one lithium-containing phosphate in the positive electrode active material is a second phosphate, and the mass percentage of manganese atoms in the second phosphate is ≤ 0.01%; and / or,

[0078] the second phosphate further comprises iron atoms, and the mass percentage of the iron atoms in the second phosphate is 30%-38%.

[0079] 14. The battery cell according to any one of aspects 1 to 13, wherein the powder compaction density of the positive electrode material is ≥ 2.2 g / cm3 under 30000 N. 3 or ≥ 2.3 g / cm3. 3 .

[0080] 15. The battery cell according to any one of aspects 1 to 14, wherein the specific surface area of the positive electrode material is 7-22 m2 / g. 2 .

[0081] 16. The battery cell according to any one of aspects 1 to 15, wherein the volume average particle size Dv50 of the positive electrode material is 0.05-2 μm or 0.15-1.2 μm.

[0082] 17. The battery cell according to any one of aspects 1 to 16, wherein the powder resistivity of the lithium-containing phosphate is 2-20 Ω-cm or 2-10 Ω-cm under 12 MPa.

[0083] 18. The battery cell according to any one of aspects 1 to 17, wherein the volume average particle size Dv50 of the lithium-containing phosphate is 0.5-3 μm or 0.9-1.9 μm.

[0084] 19. The battery cell according to any one of aspects 1 to 18, wherein the powder tap density of the lithium-containing phosphate is 0.5-2.0 g / cm3 or 0.7-1.8 g / cm3. 3 . 3 .

[0085] 20. The battery cell according to any one of aspects 1 to 19, wherein the positive electrode active material further comprises carbon; and / or,

[0086] the mass percentage of the carbon is 1%-3% based on the mass of the positive electrode material.

[0087] 21. The battery cell according to any one of aspects 1 to 20, wherein the positive electrode sheet further comprises a positive electrode conductive layer, and the positive electrode conductive layer is arranged between the positive electrode current collector and the positive electrode active layer.

[0088] 22. The battery cell according to aspect 21, wherein the thickness of the positive electrode conductive layer is 0.5-2 μm.

[0089] 23. The battery cell according to any one of aspects 21 or 22, wherein the positive electrode conductive layer comprises one or more of a positive electrode conductive agent, a positive electrode binder.

[0090] 24. The battery cell according to aspect 23, comprising one or more of:

[0091] the positive electrode conductive agent comprises one or more of super P, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers;

[0092] the positive electrode conductive agent comprises at least super P and carbon nanotubes;

[0093] the positive electrode binder comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorine-containing acrylic ester resin.

[0094] 25. The battery cell according to any one of aspects 23 or 24, wherein the mass percentage of the positive electrode conductive agent is 30%-50% based on the mass of the positive electrode conductive layer; and / or,

[0095] the mass percentage of the positive electrode binder is 50%-70% based on the mass of the positive electrode conductive layer.

[0096] 26. The battery cell according to any one of aspects 1 to 25, wherein the positive electrode active layer further comprises a lithium supplement agent, and the lithium supplement agent comprises one or more of lithium nickel cobalt manganese oxide, lithium ferrite, lithium nickelate, lithium cobaltate, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metavanadate, lithium tartrate, trilithium citrate, lithium oxide, lithium fluoride, lithium sulfide, lithium nitride; and / or,

[0097] the lithium ferrite in the lithium supplement agent is lithium-rich lithium ferrite; and / or,

[0098] the lithium nickelate in the lithium supplement agent is lithium-rich lithium nickelate.

[0099] 27. The battery cell according to aspect 26, wherein the mass percentage of the lithium supplement agent is ≥0.05% or 0.3%-8.5% based on the mass of the positive electrode active layer.

[0100] 28. The battery cell according to any one of aspects 1 to 27, wherein the compaction density of the negative electrode active layer after cold pressing is 1.50-1.80 g / cm 3 or 1.6-1.75 g / cm 3 .

[0101] 29. The battery cell according to any one of aspects 1 to 28, wherein the negative electrode sheet further comprises a negative electrode conductive layer disposed between the negative electrode current collector and the negative electrode active layer.

[0102] 30. The battery cell according to aspect 29, wherein the negative electrode conductive layer has a thickness of 0.5-2 pm.

[0103] 31. The battery cell according to aspect 29 or 30, wherein the negative electrode conductive layer comprises one or more of a negative electrode conductive agent, a negative electrode binder.

[0104] 32. The battery cell according to aspect 31, wherein the negative electrode conductive agent comprises one or more of super conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers; and / or,

[0105] the negative electrode binder comprises one or more of styrene butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate, carboxymethyl chitosan.

[0106] 33. The battery cell according to aspect 31 or 32, wherein the mass percentage of the negative electrode conductive agent is 20%-40% based on the mass of the negative electrode conductive layer; and / or,

[0107] the mass percentage of the negative electrode binder is 60%-80% based on the mass of the negative electrode conductive layer.

[0108] 34. The battery cell according to any one of aspects 1 to 33, wherein the negative electrode active layer is a single layer or a multi-layer structure, and the volume average particle size Dv50 of the negative electrode active material in the negative electrode active layer is 7.5-19.5 pm.

[0109] 35. The battery cell according to any one of aspects 1 to 34, wherein the negative electrode active layer is a single layer structure, and the volume average particle size Dv50 of the negative electrode active material is 8.0-17.5 pm.

[0110] 36. The battery cell according to any one of aspects 1 to 34, wherein the negative electrode active layer comprises a first negative electrode active layer proximate to the negative electrode current collector and a second negative electrode active layer disposed on the first negative electrode active layer.

[0111] 37. The battery cell according to aspect 36, wherein the thickness ratio of the second negative electrode active layer to the first negative electrode active layer is 2:8-8:2.

[0112] 38. The battery cell according to aspect 36 or 37, wherein the volume average particle size Dv50 of the negative electrode active material in the first negative electrode active layer is 7.5-19.5 pm or 12.5-18.5 pm.

[0113] 39. The battery cell according to any one of aspects 36 to 38, wherein the volume average particle size Dv50 of the negative active material in the second negative active layer is 7.5-19.5 pm or 7.5-15.5 pm.

[0114] 40. The battery cell according to any one of aspects 36 to 39, wherein the volume average particle size Dv50 of the negative active material in the second negative active layer is less than the volume average particle size Dv50 of the negative active material in the first negative active layer.

[0115] 41. The battery cell according to any one of aspects 36 to 40, wherein the graphite in the first negative active layer is selected from one or more of natural graphite, composite graphite; and / or,

[0116] the graphite in the second negative active layer is selected from one or more of composite graphite.

[0117] 42. The battery cell according to aspect 41, wherein the composite graphite comprises a bulk and a coating layer coated on the surface of the bulk; the bulk comprises artificial graphite, and the coating layer comprises amorphous carbon.

[0118] 43. The battery cell according to aspect 41 or 42, wherein the composite graphite comprises secondary particles.

[0119] 44. The battery cell according to any one of aspects 41 to 43, wherein the powder resistivity of the composite graphite at 8 MPa is 0.01-0.04 W-cm.

[0120] 45. The battery cell according to any one of aspects 41 to 44, wherein the powder compaction density of the composite graphite at a pressure of 20,000 N is 1.5-1.85 g / cm 3 or 1.55-1.75 g / cm 3 .

[0121] 46. The battery cell according to any one of aspects 1 to 45, wherein the charge specific capacity of the negative electrode material at a rate of 0.1 C is 350-550 mAh / g.

[0122] 47. The battery cell according to any one of aspects 1 to 46, wherein the negative active material further comprises a silicon material.

[0123] 48. The battery cell according to aspect 47, wherein the silicon material comprises one or more of a silicon oxide compound, a silicon carbon compound; and / or,

[0124] the mass percentage content of silicon element is 0.3%-10% or 1%-6% based on the mass of the negative electrode material.

[0125] 49. The battery cell according to any one of aspects 1 to 48, further comprising an electrolyte, wherein the electrolyte has an electrical conductivity of 10-20 mS / cm or 12-17 mS / cm at room temperature.

[0126] 50. The battery cell according to any one of aspects 1 to 49, further comprising a separator, wherein the separator comprises a porous base film and a functional film layer disposed on at least one side of the porous base film.

[0127] 51. The battery cell according to aspect 50, wherein the porous base film has a thickness of ≤ 15 μm or 5-7 μm; and / or,

[0128] the porous base film has a porosity of 20%-70% or 30%-50%.

[0129] 52. The battery cell according to aspects 50 or 51, wherein the functional film layer comprises a first functional film layer and a second functional film layer disposed on both sides of the porous base film, respectively, the first functional film layer comprises inorganic material particles, and the second functional film layer comprises composite particles, the composite particles comprise non-fluoropolymer particles and inorganic material particles attached to the surface of or located within the non-fluoropolymer particles.

[0130] 53. The battery cell according to any one of aspects 1 to 52, wherein the positive current collector has a thickness of 9-17 μm; and / or,

[0131] the negative current collector has a thickness of 4.5-8 μm.

[0132] 54. The battery cell according to any one of aspects 1 to 53, wherein the battery has a battery liquid injection coefficient of 2.4-3.1 g / Ah.

[0133] 55. The battery cell according to any one of aspects 1 to 54, wherein the battery has a volumetric energy density of 400-550 Wh / L or 450-500 Wh / L.

[0134] 56. A battery device comprising the battery cell according to any one of aspects 1 to 55; the battery device comprises a battery module, a battery pack or an energy storage device.

[0135] 57. An electric device comprising the battery cell according to any one of aspects 1 to 55 or the battery device according to aspect 56. BRIEF DESCRIPTION OF DRAWINGS

[0136] FIG. 1 is a schematic view of a battery assembly according to an embodiment of the present application.

[0137] FIG. 2 is an exploded view of a battery cell according to an embodiment of the present application.

[0138] FIG. 3 is a schematic view of a battery pack according to an embodiment of the present application.

[0139] FIG. 4 is an exploded view of the battery pack shown in FIG. 3.

[0140] FIG. 5 is a schematic view of an electric device using the battery pack of the embodiment of the present application as a power source.

[0141] BRIEF DESCRIPTION OF DRAWINGS 1: battery pack; 2: upper case; 3: lower case; 4: battery module; 5: battery cell; 51: case; 52: electrode assembly; 53: top cap assembly. DETAILED DESCRIPTION

[0142] Hereinafter, the embodiments of the battery cell, the battery module, the battery pack, and the electric device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of matters well known in the art, repeated descriptions of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0143] The ranges disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. In addition, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, a numerical range "a-b" represents a shorthand manner of describing each and every numerical value that is contained within the range, wherein a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shorthand manner of describing those numerical combinations. In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0144] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0145] If not specifically stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0146] If not otherwise specified, all steps of the present application can be performed in sequence or randomly, preferably in sequence. For example, a method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, it is mentioned that the method can further comprise step (c), which means that step (c) can be added to the method in any order. For example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0147] [Battery cell]

[0148] Battery cell is also called rechargeable battery or storage battery, which refers to the battery that can be activated by charging after discharging and continue to use.

[0149] Generally, the battery cell comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. During the charging and discharging process of the battery, active ions (such as lithium ions) are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, which mainly prevents the short circuit of the positive and negative electrodes, and allows the active ions to pass through. The electrolyte is between the positive electrode sheet and the negative electrode sheet, which mainly plays the role of conducting active ions.

[0150] One embodiment of the present application provides a battery cell, comprising a positive electrode sheet and a negative electrode sheet; wherein,

[0151] The negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer arranged on at least one side of the negative electrode current collector, and the negative electrode active layer comprises a negative electrode material, and the negative electrode material comprises graphite;

[0152] The positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer arranged on at least one side of the positive electrode current collector, and the positive electrode active layer comprises a positive electrode material, and the positive electrode material comprises a positive electrode active material;

[0153] The positive electrode active material comprises a lithium iron manganese phosphate material and a lithium iron phosphate material, the mass ratio of the lithium iron manganese phosphate material in the positive electrode active material is 50%-95%, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or a range consisting of any of the above values; the powder resistivity of the positive electrode material under 12 MPa is 5-70 Ω·cm, for example, 5 Ω·cm, 7 Ω·cm, 8 Ω·cm, 9 Ω·cm, 10 Ω·cm, 12 Ω·cm, 13 Ω·cm, 15 Ω·cm, 16 Ω·cm, 18 Ω·cm, 20 Ω·cm, 22 Ω·cm, 25 Ω·cm, 27 Ω·cm, 28 Ω·cm, 30 Ω·cm, 31 Ω·cm, 33 Ω·cm, 34 Ω·cm, 35 Ω·cm, 37 Ω·cm, 40 Ω·cm, 42 Ω·cm, 44 Ω·cm, 45 Ω·cm, 48 Ω·cm, 50 Ω·cm, 53 Ω·cm, 55 Ω·cm, 57 Ω·cm, 60 Ω·cm, 62 Ω·cm, 65 Ω·cm, 67 Ω·cm, 68 Ω·cm, 70 Ω·cm, or a range consisting of any of the above values.

[0154] In some embodiments, the positive electrode material can be a powder obtained after calcining and powder scraping of a positive electrode sheet, and the powder can be a positive electrode active material, other materials with incomplete calcination of residual binders, etc.

[0155] In some embodiments, the positive electrode material can also be a positive electrode active material, and the positive electrode active material comprises a lithium iron manganese phosphate material and a lithium iron phosphate material.

[0156] The present application aims to develop a battery cell with high energy density and good power performance under a low-cost system.

[0157] The lithium iron manganese phosphate material has a higher plateau voltage than the lithium iron phosphate material, and increasing the content of the lithium iron manganese phosphate material in the mixed system is beneficial to improving the energy density of the battery cell. However, because the powder resistivity of the lithium iron manganese phosphate material is larger than that of the lithium iron phosphate material, the powder resistivity of the mixture of the two materials is prone to be too large, which deteriorates the power performance of the battery cell. The present application controls the ratio of the lithium iron manganese phosphate material and the lithium iron phosphate material so that the battery cell has a higher energy density, and further adjusts the powder resistivity range of the positive electrode material to improve the energy density and the power performance of the battery cell.

[0158] In some embodiments, the mass ratio of the lithium iron manganese phosphate material in the positive electrode active material is 50%-70%.

[0159] Therefore, the energy density and the power performance of the battery monomer are simultaneously improved. Moreover, the mass ratio of the lithium manganese iron phosphate material in the positive electrode active material is increased in the above range, and the energy density of the battery monomer is further improved; the mass ratio of the lithium manganese iron phosphate material in the positive electrode active material is decreased in the above range, and the power performance of the battery monomer is further improved.

[0160] In some embodiments, the powder resistivity of the lithium manganese iron phosphate material at 12 MPa is 8-120 Ω·cm, optionally 8-80 Ω·cm, for example 8 Ω·cm, 10 Ω·cm, 20 Ω·cm, 23 Ω·cm, 25 Ω·cm, 30 Ω·cm, 32 Ω·cm, 35 Ω·cm, 38 Ω·cm, 40 Ω·cm, 45 Ω·cm, 50 Ω·cm, 60 Ω·cm, 70 Ω·cm, 80 Ω·cm, 90 Ω·cm, 100 Ω·cm, 110 Ω·cm, 120 Ω·cm, or a range consisting of any of the aforementioned values.

[0161] In some embodiments, the volume average particle size Dv50 of the lithium manganese iron phosphate material is 0.1-1.2 μm, optionally 0.2-0.8 μm, for example 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, or a range consisting of any of the aforementioned values.

[0162] Therefore, the powder resistivity and the volume average particle size Dv50 of the lithium manganese iron phosphate material in the above range are beneficial to improving the power performance of the battery monomer while improving the energy density of the battery monomer.

[0163] In some embodiments, the molar ratio of manganese atoms to iron atoms in the lithium manganese iron phosphate material is 2:8-8:2, for example 3:7, 4:6, 5:5, 6:4, 7:3, or a range consisting of any of the aforementioned values.

[0164] In some embodiments, the powder resistivity of the lithium iron phosphate material at 12 MPa is 3-100 Ω·cm, optionally 3-20 Ω·cm, for example 3 Ω·cm, 5 Ω·cm, 7 Ω·cm, 8 Ω·cm, 10 Ω·cm, 20 Ω·cm, 23 Ω·cm, 25 Ω·cm, 30 Ω·cm, 32 Ω·cm, 35 Ω·cm, 38 Ω·cm, 40 Ω·cm, 45 Ω·cm, 50 Ω·cm, 60 Ω·cm, 70 Ω·cm, 80 Ω·cm, 90 Ω·cm, 100 Ω·cm, or a range consisting of any of the aforementioned values.

[0165] In some embodiments, the volume average particle size Dv50 of the lithium iron phosphate material is 0.9-1.9 μm, for example 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, or a range composed of any of the aforementioned values.

[0166] In some embodiments, the surface density of the positive electrode active layer of the battery cell is 200-450 mg / 1540.25 mm2, for example 200 mg / 1540.25 mm2, 210 mg / 1540.25 mm2, 220 mg / 1540.25 mm2, 230 mg / 1540.25 mm2, 240 mg / 1540.25 mm2, 250 mg / 1540.25 mm2, 260 mg / 1540.25 mm2, 270 mg / 1540.25 mm2, 280 mg / 1540.25 mm2, 290 mg / 1540.25 mm2, 300 mg / 1540.25 mm2, 310 mg / 1540.25 mm2, 320 mg / 1540.25 mm2, 330 mg / 1540.25 mm2, 340 mg / 1540.25 mm2, 350 mg / 1540.25 mm2, 360 mg / 1540.25 mm2, 370 mg / 1540.25 mm2, 380 mg / 1540.25 mm2, 390 mg / 1540.25 mm2, 400 mg / 1540.25 mm2, 410 mg / 1540.25 mm2, 420 mg / 1540.25 mm2, 430 mg / 1540.25 mm2, 440 mg / 1540.25 mm2, 450 mg / 1540.25 mm2, or a range composed of any of the aforementioned values. 2 , optionally 290-350 mg / 1540.25 mm2 2 , for example 220 mg / 1540.25 mm2 2 , 250 mg / 1540.25 mm2 2 , 270 mg / 1540.25 mm2 2 , 30 mg / 1540.25 mm2 2 , 320 mg / 1540.25 mm2 2 , 340 mg / 1540.25 mm2 2 , 350 mg / 1540.25 mm2 2 , 370 mg / 1540.25 mm2 2 , 380 mg / 1540.25 mm2 2 , 400 mg / 1540.25 mm2 2 , 420 mg / 1540.25 mm2 2 , 440 mg / 1540.25 mm2 2 , or a range composed of any of the aforementioned values. In this way, the power performance of the battery cell meets the requirements, while the energy density of the battery cell is improved.

[0167] In some embodiments, the compacted density of the positive electrode active layer of the battery cell is 2.27-2.67 g / cm3, for example 2.27 g / cm3, 2.28 g / cm3, 2.29 g / cm3, 2.3 g / cm3, 2.31 g / cm3, 2.32 g / cm3, 2.33 g / cm3, 2.34 g / cm3, 2.35 g / cm3, 2.36 g / cm3, 2.37 g / cm3, 2.38 g / cm3, 2.39 g / cm3, 2.4 g / cm3, 2.41 g / cm3, 2.42 g / cm3, 2.43 g / cm3, 2.44 g / cm3, 2.45 g / cm3, 2.46 g / cm3, 2.47 g / cm3, 2.48 g / cm3, 2.49 g / cm3, 2.5 g / cm3, 2.51 g / cm3, 2.52 g / cm3, 2.53 g / cm3, 2.54 g / cm3, 2.55 g / cm3, 2.56 g / cm3, 2.57 g / cm3, 2.58 g / cm3, 2.59 g / cm3, 2.6 g / cm3, 2.61 g / cm3, 2.62 g / cm3, 2.63 g / cm3, 2.64 g / cm3, 2.65 g / cm3, 2.66 g / cm3, 2.67 g / cm3, or a range composed of any of the aforementioned values. 3 , optionally 2.37-2.62 g / cm3 3 , for example 2.3 g / cm3 3 , 2.35 g / cm3 3 , 2.4 g / cm3 3 , 2.45 g / cm3 3 , 2.47 g / cm3 3 , 2.5 g / cm3 3 , 2.51 g / cm3 3 , 2.52 g / cm3 3 , 2.55 g / cm3 3 , 2.58 g / cm3 3 , 2.6 g / cm33 2.62 g / cm3 3 2.63 g / cm3 3 2.65 g / cm3 3 2.66 g / cm3 3 or a range of values formed by any of the above. Thus, the energy density of the battery cell is improved while meeting the power performance requirements.

[0168] In some embodiments, the battery cell has a surface density of the negative active layer of 100-180 mg / 1540.25 mm2at 100% SOC state. 2 for example 100 mg / 1540.25 mm2 2 110 mg / 1540.25 mm2 2 120 mg / 1540.25 mm2 2 140 mg / 1540.25 mm2 2 150 mg / 1540.25 mm2 2 160 mg / 1540.25 mm2 2 170 mg / 1540.25 mm2 2 180 mg / 1540.25 mm2 2 or a range of values formed by any of the above. Thus, the energy density of the battery cell is improved while meeting the power performance requirements.

[0169] In some embodiments, the battery cell has a compacted density of the negative active layer of 1.2-1.45 g / cm3at 100% SOC state. 3 optionally 1.28-1.44 g / cm3 3 for example 1.25 g / cm3 3 1.3 g / cm3 3 1.34 g / cm3 3 1.38 g / cm3 3 1.4 g / cm3 3 1.41 g / cm3 3 1.42 g / cm3 3 1.44 g / cm3 3 or a range of values formed by any of the above. Thus, the energy density of the battery cell is improved while meeting the power performance requirements.

[0170] In the present application, 100% SOC state refers to the highest state in which the battery cell can release energy. The process of charging the battery cell to 100% SOC is not unique, for example, it can be charged to the charging cutoff voltage at 0.33C constant current at 25°C, and then charged to the state reached when the current is less than 0.05C at the charging cutoff voltage.

[0171] In some embodiments, the negative electrode material further comprises a silicon material.

[0172] In some embodiments, the silicon-containing material comprises one or more of a silicon oxide compound, a silicon carbon compound; and / or,

[0173] The mass percentage of the silicon element is 0.3%-10%, optionally 1%-6%, for example 1%, 2%, 3%, 4%, 5%, 6%, or a range consisting of any of the aforementioned values, based on the mass of the negative electrode material.

[0174] Thus, the energy density of the battery cell is improved while meeting the power performance requirement.

[0175] In some embodiments, the lithium iron phosphate material has a chemical formula of Li x Fe (1-s) M s P y O z wherein x is greater than or equal to 0.5 and less than or equal to 1.3 (for example 0.5, 0.8, 1, 1.1, 1.2, 1.3, or a range consisting of any of the aforementioned values), s is greater than or equal to 0 and less than 1 (for example 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, or a range consisting of any of the aforementioned values), y is greater than or equal to 0.5 and less than or equal to 1.3 (for example 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, or a range consisting of any of the aforementioned values), z is greater than or equal to 3 and less than or equal to 5 (for example 3, 4, 5, or a range consisting of any of the aforementioned values), and M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Hf, Ni, Co, Ru, Ag, Pb.

[0176] In some embodiments, the lithium manganese iron phosphate material has a chemical formula of Li x Fe (1-t-s) Mn t M s P y O zwherein x is greater than or equal to 0.5 and less than or equal to 1.3 (e.g., 0.5, 0.8, 1, 1.1, 1.2, 1.3, or a range of values between any of the foregoing), t is greater than 0 and less than 1 (e.g., 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, or a range of values between any of the foregoing), s is greater than or equal to 0 and less than 1 (e.g., 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, or a range of values between any of the foregoing), 1-t-s is greater than 0 and less than 1 (e.g., 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, or a range of values between any of the foregoing), y is greater than or equal to 0.5 and less than or equal to 1.3 (e.g., 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, or a range of values between any of the foregoing), z is greater than or equal to 3 and less than or equal to 5 (e.g., 3, 4, 5, or a range of values between any of the foregoing), and M comprises one or more elements selected from the group consisting of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Hf, Ni, Co, Ru, Ag, Pb.

[0177] In some embodiments, the positive electrode material has a powder compaction density at 30000 N of 2.2-2.8 g / cm3. 3 , optionally 2.3-2.8 g / cm3. 3 , for example 2.2 g / cm3. 3 , 2.3 g / cm3. 3 , 2.4 g / cm3. 3 , 2.5 g / cm3. 3 , 2.6 g / cm3. 3 , 2.8 g / cm3. 3 , or a range of values between any of the foregoing.

[0178] In some embodiments, the positive electrode sheet further comprises a positive electrode conductive layer disposed between the positive electrode current collector and the positive electrode active layer.

[0179] In some embodiments, the positive electrode conductive layer has a thickness of 0.5-2 μm, for example 1 μm.

[0180] In some embodiments, the positive electrode conductive layer comprises one or more of a positive electrode conductive agent, a positive electrode binder.

[0181] In some embodiments, the battery cell comprises one or more of:

[0182] The positive electrode conductive agent includes one or more of super conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0183] The positive electrode conductive agent includes at least super conductive carbon and carbon nanotubes.

[0184] The positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorine-containing acrylic ester resin.

[0185] In some embodiments, the mass percentage of the positive electrode conductive agent is 30%-50% based on the mass of the positive electrode conductive layer; and / or,

[0186] The mass percentage of the positive electrode binder is 50%-70% based on the mass of the positive electrode conductive layer.

[0187] In some embodiments, the negative electrode sheet further includes a negative electrode conductive layer disposed between the negative electrode current collector and the negative electrode active layer.

[0188] In some embodiments, the thickness of the negative electrode conductive layer is 0.5-2 μm, for example, 1 μm.

[0189] In some embodiments, the negative electrode conductive layer includes one or more of a negative electrode conductive agent and a negative electrode binder.

[0190] In some embodiments, the negative electrode conductive agent includes one or more of super conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; and / or,

[0191] The negative electrode binder includes one or more of styrene butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0192] In some embodiments, the mass percentage of the negative electrode conductive agent is 20%-40% based on the mass of the negative electrode conductive layer; and / or,

[0193] The mass percentage of the negative electrode binder is 60%-80% based on the mass of the negative electrode conductive layer.

[0194] In some embodiments, the negative electrode active layer is a single-layer or multi-layer structure, and the volume average particle size Dv50 of the negative electrode active material in the negative electrode active layer is 7.5-19.5 μm.

[0195] In some embodiments, the negative active layer is a single layer structure, and the volume average particle size Dv50 of the negative active material is 8.0-17.5 μm.

[0196] In some embodiments, the negative active layer comprises a first negative active layer adjacent to the negative current collector and a second negative active layer disposed on the first negative active layer.

[0197] In some embodiments, the thickness ratio of the second negative active layer to the first negative active layer is 2:8-8:2, for example 1:1.

[0198] In some embodiments, the volume average particle size Dv50 of the negative active material in the first negative active layer is 7.5-19.5 μm, optionally 12.5-18.5 μm, for example 8 μm, 8.5 μm, 9 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 13 μm, 13.5 μm, 15 μm, 16 μm, 16.5 μm, 17 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm, or a range formed by any of the aforementioned values.

[0199] In some embodiments, the volume average particle size Dv50 of the negative active material in the second negative active layer is 7.5-19.5 μm, optionally 7.5-15.5 μm, for example 8 μm, 8.5 μm, 9 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 13 μm, 13.5 μm, 15 μm, 16 μm, 16.5 μm, 17 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm, or a range formed by any of the aforementioned values.

[0200] In some embodiments, the volume average particle size Dv50 of the negative active material in the second negative active layer is smaller than the volume average particle size Dv50 of the negative active material in the first negative active layer. Thereby, the power performance of the battery cell is improved, while the energy density of the battery cell is increased and the cost is reduced.

[0201] In some embodiments, the graphite in the first negative active layer is selected from one or more of natural graphite, composite graphite; and / or,

[0202] The graphite in the second negative active layer is selected from one or more of composite graphite.

[0203] In some embodiments, the composite graphite comprises a body and a coating layer coated on the surface of the body; the body comprises artificial graphite, and the coating layer comprises amorphous carbon.

[0204] In some embodiments, the composite graphite comprises secondary particles.

[0205] In some embodiments, the composite graphite has a powder resistivity of 0.01-0.04 Ω·cm at 8 MPa.

[0206] In some embodiments, the composite graphite has a powder compacted density of 1.5-1.85 g / cm 3 or 1.55-1.75 g / cm 3 , for example 1.5 g / cm 3 , 1.6 g / cm 3 , 1.7 g / cm 3 , 1.75 g / cm 3 , 1.8 g / cm 3 or a range consisting of any of the above values.

[0207] In some embodiments, the negative electrode material has a charge specific capacity of 350-550 mAh / g at a 0.1C rate.

[0208] In some embodiments, the battery cell further comprises an electrolyte, and the electrolyte has an electrical conductivity of 10-20 mS / cm or 12-17 mS / cm at room temperature.

[0209] In some embodiments, the battery cell has a volumetric energy density of 400-550 Wh / L or 450-500 Wh / L.

[0210] In this application, the mass percentage of silicon in the negative electrode material is tested by a conventional method in the art. For example, the following specific method is used: the negative electrode sheet of the battery cell is disassembled, the negative electrode sheet is washed with DMC (dimethyl carbonate) and dried and calcined, and then the negative electrode material in the negative electrode active layer is collected, a plurality of points (for example, 10-50 points) in the negative electrode material are selected for testing by SEM-EDS combined instrument, and the average value is taken to obtain the mass percentage of silicon in the negative electrode material.

[0211] In this application, the powder resistivity of the positive electrode material is tested by a conventional method in the art. For example, the following specific method is used: the positive electrode sheet is obtained after disassembling the battery cell, the positive electrode sheet is washed with DMC (dimethyl carbonate) and dried and calcined, and then the positive electrode material on the positive electrode current collector is collected by a powder scraping method, a powder resistance tester is turned on and stabilized, a certain amount of positive electrode material is weighed and added to the feeding cavity and the feeding cavity depth is adjusted, the target pressure is applied according to the target pressure and the cavity area in the feeding cavity, and the powder resistivity test result at a certain pressure is collected.

[0212] In the present application, the powder resistivity of the lithium manganese iron phosphate material and the lithium iron phosphate material is tested by a conventional method in the art. For example, the specific method described above is referred to for testing.

[0213] In the present application, the surface density and the compacted density of the positive active layer (negative active layer) are tested by a conventional method in the art. For example, the specific method as follows is referred to for testing:

[0214] The positive electrode tab (negative electrode tab) of a fixed area is cut and weighed, the weight of the positive current collector (negative current collector) of the same area is weighed and calculated in advance, and the average thickness of the positive active layer (negative active layer) on the positive electrode tab (negative electrode tab) is measured.

[0215] The weight of the positive current collector (negative current collector) is subtracted from the weight of the positive electrode tab (negative electrode tab), and then divided by the fixed area to obtain the surface density of the positive active layer (negative active layer).

[0216] The surface density of the positive active layer (negative active layer) is divided by the average thickness of the positive active layer (negative active layer) to obtain the compacted density of the positive active layer (negative active layer).

[0217] The surface density and the compacted density of the positive active layer (negative active layer) at the 100% SOC state of the battery cell are tested by the above method at the 100% SOC state of the battery cell.

[0218] In the present application, the volume average particle size Dv50 refers to the particle size at which 50% of the volume is accumulated from the small particle size side in the particle size distribution based on volume. The Dv50 particle size is tested by a conventional method in the art, for example, it can be determined 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.

[0219] In the present application, the Dv50 particle size of the lithium manganese iron phosphate material and the lithium iron phosphate material is tested by a conventional method in the art, for example, the specific method described above can be referred to for testing.

[0220] In the present application, the charge specific capacity of the negative electrode material at 0.1C rate is tested by a method conventional in the art. For example, the specific testing method is as follows: the double-sided coated negative electrode sheet in the battery monomer is disassembled, the negative electrode material is scraped off from one side of the negative electrode current collector and weighed, a plurality of negative electrode sheets of the same area are taken and the above operation is performed, the average weight of the negative electrode material on one side of the negative electrode sheet is obtained, and the same area of the single-sided negative electrode sheet is used to prepare a button cell. The button cell is charged to 4.1V at 0.1C rate at 25°C, then constant voltage charged to 0.05C, and after standing for 30min, discharged to 2.5V at 0.1C rate, and the charging and discharging is repeated twice. The last charging capacity is recorded as Cn. The test result is obtained by dividing the last charging capacity Cn by the weight of the negative electrode material on one side m.

[0221] In the present application, the powder compaction density of the positive electrode material is tested by a method conventional in the art. For example, the specific testing method is as follows: the positive electrode sheet of the battery monomer is washed with DMC (dimethyl carbonate) to clean the positive electrode sheet, and the positive electrode material in the positive electrode active layer is collected after the positive electrode sheet is dried and calcined. The positive electrode material powder is weighed in the compaction density tester mold, and the tester automatically applies a target pressure to the powder to compact the powder. According to the cross-sectional area of the mold and the thickness of the powder at this time, the volume of the powder can be calculated, and the powder compaction density result can be obtained according to the compaction density = mass / volume.

[0222] In the present application, the positive electrode material refers to the material of the positive electrode active layer collected from the surface of the positive electrode current collector after the positive electrode sheet is cleaned, dried and calcined. The positive electrode material includes the positive electrode active material and / or its calcined product, and also includes the additives used in the preparation of the positive electrode sheet and / or their calcined products. The additives include, but are not limited to, positive electrode binders, positive electrode conductive agents, positive electrode film formers, etc.

[0223] In the present application, the negative electrode material refers to the material of the negative electrode active layer collected from the surface of the negative electrode current collector after the negative electrode sheet is cleaned, dried and calcined. The negative electrode material includes the negative electrode active material and / or its calcined product, and also includes the additives used in the preparation of the negative electrode sheet and / or their calcined products. The additives include, but are not limited to, negative electrode binders, negative electrode thickeners, negative electrode conductive agents, negative electrode film formers, etc.

[0224] In the present application, the types of elements in the active material of the positive electrode material and the powder compaction density of the positive electrode material can be tested at any state of the battery monomer between 0% SOC and 100% SOC. The above state change of the battery monomer does not substantially affect the test results.

[0225] [Positive electrode sheet]

[0226] The battery cell will be accompanied by Li deintercalation and consumption during charging and discharging process, and the molar content of Li is different when the battery cell is discharged to different states. In the enumeration of the positive electrode active material in the present application, the molar content of Li is the initial state of the material, i.e. the state before feeding, and the positive electrode active material is applied to the battery system. After charging and discharging cycle, the molar content of Li will change.

[0227] In the enumeration of the positive electrode active material in the present application, the molar content of O is only the theoretical state value, and the lattice oxygen release will cause the change of the molar content of oxygen, and the actual molar content of O will appear floating.

[0228] As an example, the positive electrode current collector has two opposite surfaces in the thickness direction of itself, and the positive electrode film layer is arranged on any one or both of the two opposite surfaces of the positive electrode current collector.

[0229] In some embodiments, the positive electrode current collector can adopt a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be adopted. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0230] In some embodiments, the positive electrode active material can also adopt the positive electrode active material for the battery cell known in the art. As an example, the positive electrode active material can also include at least one of the following materials: lithium transition metal oxide and its modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for battery cells can also be used. These positive electrode active materials can be used only one kind alone, or two or more kinds in combination. Among them, examples of lithium transition metal oxides can include but are not limited to lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium iron oxide (such as Li5NiO4), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which can also be referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which can also be referred to as NCM 523 ), LiNi 0.5 Co 0.25Mn 0.25 O2(also can be referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2(also can be referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2(also can be referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2), and modified compounds thereof.

[0231] In some embodiments, the positive active layer can further optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin.

[0232] In some embodiments, the positive active layer can further optionally include a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0233] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as the positive active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector, and after processes such as drying, cold pressing, etc., the positive electrode sheet can be obtained.

[0234] [Negative electrode sheet]

[0235] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is provided on either one or both of the two opposite surfaces of the negative electrode current collector.

[0236] In some embodiments, the negative current collector can employ a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base layer (e.g., a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0237] In some embodiments, the negative active material can also employ a negative active material for a battery cell known in the art. As an example, the negative active material can also include at least one of the following materials: soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can be selected from at least one of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative active material for a battery cell can also be used. These negative active materials can be used alone or in combination of two or more.

[0238] In some embodiments, the negative active layer can also optionally include a binder. As an example, the binder can be selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0239] In some embodiments, the negative active layer can also optionally include a conductive agent. As an example, the conductive agent can be selected from at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

[0240] In some embodiments, the negative active layer can also optionally include other auxiliary agents, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)), etc.

[0241] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-described components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative current collector; and drying, cold-pressing, etc., to obtain the negative electrode sheet.

[0242] [Electrolyte]

[0243] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte is not particularly limited in the present application and can be selected as desired.

[0244] In some embodiments, the electrolyte is in a liquid state and includes an electrolyte salt and a solvent.

[0245] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro oxalato borate, lithium di oxalato borate, lithium difluoro di oxalato phosphate, and lithium tetrafluoro oxalato phosphate.

[0246] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0247] In some embodiments, the electrolyte can also optionally include an additive. As an example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include an additive capable of improving certain properties of the battery cell, such as an additive that improves overcharge performance of the battery cell, an additive that improves high or low temperature performance of the battery cell, etc.

[0248] [Separator]

[0249] In some embodiments, the battery cell further includes a separator. The type of separator is not particularly limited in the present application and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0250] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of the layers can be the same or different and are not particularly limited.

[0251] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly through a winding process or a stacking process.

[0252] In some embodiments, the battery cell can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte described above.

[0253] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, etc. can be listed.

[0254] The shape of the battery cell is not particularly limited in the present application, and can be cylindrical, square, or any other shape. For example, FIG. 1 is an electrode assembly 52 of a battery cell in a square structure as an example.

[0255] In some embodiments, referring to FIG. 2, the outer package can include a shell 51 and a cover plate 53. The shell 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be provided on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can form the electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific actual needs.

[0256] In some embodiments, the battery cell can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more, which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0257] In the battery module, the plurality of battery cells can be arranged in sequence along the length direction of the battery module. Of course, they can also be arranged in any other manner. Further, the plurality of battery cells can be fixed by fasteners.

[0258] Optionally, the battery module can further include a housing having a receiving space, and the plurality of battery cells are received in the receiving space.

[0259] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0260] FIGS. 3 and 4 are a battery pack 1 as an example. Referring to FIGS. 3 and 4, the battery pack 1 can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be provided on the lower box body 3 to form a closed space for receiving the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0261] In addition, the application also provides a power utilization device, which comprises at least one of the battery monomer, the battery module, or the battery pack provided by the application. The battery monomer, the battery module, or the battery pack can be used as a power supply of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0262] As the power utilization device, the battery monomer, the battery module, or the battery pack can be selected according to the use requirements thereof.

[0263] FIG. 5 is a power utilization device as an example. The power utilization device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of high power and high energy density of the battery monomer for the power utilization device, the battery pack or the battery module can be used.

[0264] [Embodiment]

[0265] Hereinafter, the embodiments of the application are described. The embodiments described below are exemplary and are only used to explain the application and cannot be understood as a limitation of the application. If the specific technology or condition is not indicated in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument used is not indicated by the manufacturer, it is a conventional product that can be obtained by purchase.

[0266] Embodiment 1

[0267] (1) Positive electrode tab: the two sides of the positive electrode current collector aluminum foil (thickness of 13 μm) are provided with positive electrode conductive layers, and the positive electrode active layer is provided on the positive electrode conductive layers on the two sides. The positive electrode conductive layer is a film layer formed by uniformly mixing the positive electrode conductive agent super conductive carbon, the positive electrode binder polyacrylate and the solvent, coating on the surface of the positive electrode current collector and drying, the thickness is 1 μm, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 50%, and the mass content of the positive electrode binder in the positive electrode conductive layer is 50%. The positive electrode active layer comprises positive electrode active materials lithium manganese iron phosphate material (LMFP) and lithium iron phosphate material (LFP) (mass ratio 7:3), a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black, and the mass ratio of the three is 97:2:1.

[0268] (2) The negative electrode tab: the two sides of the negative electrode current collector copper foil (thickness of 6 μm) are provided with negative electrode conductive layers, and the negative electrode active layers are arranged on the two sides of the negative electrode conductive layers. The negative electrode conductive layer is formed by uniformly mixing the negative electrode conductive agent superconducting carbon, the negative electrode binder styrene-butadiene rubber SBR, the thickening agent sodium carboxymethyl cellulose (CMC-Na) and the solvent water, and then coating on the surface of the negative electrode current collector to form a film layer after drying, 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 thickening agent in the negative electrode conductive layer is 5%. The negative electrode active layer includes two layers of upper layer (far from the current collector) and lower layer (close to the current collector), the thickness ratio of the two layers of negative electrode active layer is 1:1, and the two layers of negative electrode active layer each includes the negative electrode active material, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR) and the thickening agent sodium carboxymethyl cellulose (CMC-Na) with a mass ratio of 96:1:2:1. The Dv50 particle size of the negative electrode active material in the upper layer (layer II) is 12.3 μm, and the Dv50 particle size of the negative electrode active material in the lower layer (layer I) is 15.31 μm. The negative electrode active material in the upper layer and the lower layer is a mixture of composite graphite and silicon with a mass ratio of 97:3 (the composite graphite particle includes 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%), wherein the Dv50 of the composite graphite particle is 15.4 μm, and the powder compaction density under a pressure of 20,000 N is 1.74 g / cm 3 .

[0269] The compaction density of the entire negative electrode active layer under the 100% SOC state of the battery is 1.41 g / cm 3 .

[0270] (3) The separator film: a polypropylene film with a thickness of 5 μm is used.

[0271] (4) The electrolyte includes ethylene carbonate (EC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC) and LiPF6, the volume ratio of ethylene carbonate (EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC) is 1:1:1, and the concentration of LiPF6 in the electrolyte is 1 mol / L. The conductivity of the electrolyte at room temperature is 13.1 mS / cm.

[0272] (5) Preparation of the battery monomer: including the positive electrode tab, the separator film and the negative electrode tab arranged in stack to obtain an electrode assembly. The electrode assembly is added into an outer packaging square aluminum shell (length of 600 mm, thickness of 19 mm and height of 105 mm), dried and then injected with the electrolyte, and the injection coefficient is 2.9 g / Ah. After packaging, high-temperature standing, formation, secondary injection, aging and capacity processes, the battery monomer is obtained.

[0273] Examples 2-12 and Comparative Examples 1-4 are similar to the battery cell preparation methods in Example 1, with the differences being described below and in Table 1.

[0274] Example 10

[0275] In the negative electrode sheet, the negative electrode active material in both the upper and lower layers is a mixture of composite graphite and silicon with a mass ratio of 94:6 (the composite graphite particles include artificial graphite and a carbon coating layer, with the carbon coating layer covering the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%). The composite graphite particles have a Dv50 of 15.4 μm and a powder compaction density of 1.74 g / cm³ under a pressure of 20000 N. 3 The Dv50 particle size of the negative electrode active material in the upper layer is 12.2 μm, and the Dv50 particle size of the negative electrode active material in the lower layer is 15.12 μm.

[0276] The compaction density of the entire negative electrode active layer at 100% SOC of the battery is 1.37 g / cm³. 3 The areal density is 107 mg / 1540.25 mm. 2 .

[0277] The remaining parameters are shown in Table 1. Parameters not shown are the same as those in Example 1.

[0278] Example 11

[0279] In the negative electrode sheet, the negative electrode active material in both the upper and lower layers is composite graphite. The Dv50 particle size of the composite graphite in the lower layer is 15.5 μm, and the Dv50 particle size of the composite graphite in the upper layer is 12.4 μm.

[0280] The compaction density of the entire negative electrode active layer at 100% SOC of the battery is 1.41 g / cm³. 3 Its areal density is 127 mg / 1540.25 mm. 2 .

[0281] The remaining parameters are shown in Table 1. Parameters not shown are the same as those in Example 1.

[0282] Example 12

[0283] The negative electrode active layer in the negative electrode sheet is a single layer. The negative electrode active material in the negative electrode active layer is a mixture of composite graphite and silicon with a mass ratio of 97:3 (the composite graphite particles include artificial graphite and a carbon coating layer, with the carbon coating layer covering the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%). The Dv50 particle size of the negative electrode active material is 13.81 μm, the Dv50 particle size of the composite graphite particles is 15.4 μm, and the powder compaction density under 20000 N pressure is 1.74 g / cm³. 3The rest of the parameters are shown in Table 1, and the parameters not shown are the same as those in Example 1.

[0284] The tap density of the positive electrode material 30000N powder in Examples 1, 9-12 is 2.37 g / cm 3 The tap density of the positive electrode material 30000N powder in Examples 2-8 and Comparative Examples 1-4 is 2.35 g / cm 3 , 2.42 g / cm 3 , 2.32 g / cm 3 , 2.49 g / cm 3 , 2.25 g / cm 3 , 2.36 g / cm 3 , 2.43 g / cm 3 , 2.53 g / cm 3 , 2.48 g / cm 3 , 2.31 g / cm 3 , 2.35 g / cm 3 .

[0285] Parameter test

[0286] Test of mass percentage of silicon element in negative electrode material: disassemble the negative electrode sheet of the battery monomer, clean the negative electrode sheet with DMC (dimethyl carbonate), and collect the negative electrode material in the negative electrode active layer after drying and calcining the negative electrode sheet. Test multiple points (e.g. 50) in the negative electrode material by SEM-EDS combined instrument, take the average value, and obtain the mass percentage of silicon element in the negative electrode material. In order to improve the test accuracy, ICP-OES and other test methods can also be used.

[0287] Test method of powder resistivity of positive electrode material: after the battery monomer is disassembled, the positive electrode sheet is obtained, the positive electrode sheet is cleaned with DMC (dimethyl carbonate) and dried and calcined, and then the positive electrode material on the positive electrode current collector is collected by the powder scraping method. After the powder resistance tester is turned on and the equipment is stabilized, a certain mass of positive electrode material is weighed and added to the feeding cavity and the feeding cavity depth is adjusted. According to the target pressure and the cavity area in the feeding cavity, the target pressure is applied, and the powder resistivity test result under 12 MPa pressure is collected. The powder resistivity of lithium manganese iron phosphate material and lithium iron phosphate material is tested according to the above method.

[0288] Test method of surface density and tap density of positive electrode active layer (negative electrode active layer):

[0289] Cut the positive electrode sheet (negative electrode sheet) of a fixed area and weigh it. The weight of the positive electrode current collector (negative electrode current collector) of the same area is weighed and calculated in advance. The average thickness of the positive electrode active layer (negative electrode active layer) on the positive electrode sheet (negative electrode sheet) is measured.

[0290] The positive active layer (negative active layer) density of area is obtained by subtracting the weight of the positive current collector (negative current collector) from the weight of the positive electrode sheet (negative electrode sheet) and dividing by the fixed area.

[0291] The positive active layer (negative active layer) density of compaction is obtained by dividing the positive active layer (negative active layer) density of area by the average thickness of the positive active layer (negative active layer).

[0292] The positive active layer (negative active layer) density of compaction at the full charge state of the battery cell is obtained by testing according to the above method at the 100% SOC state of the battery cell. The 100% SOC state of the battery cell may be, for example, charging the battery cell at 25°C to a voltage of 4.1V at a constant current of 0.33C, and then charging at a constant voltage of 4.1V until the current is less than 0.05C.

[0293] The volume average particle size Dv50 refers to the particle size at which 50% of the volume of the powder particles is accumulated from the small particle size side in the particle size distribution based on volume. The Dv50 particle size of the positive electrode material can be determined by a Malvern 3000 laser particle size analyzer according to the standard procedures and requirements of GB / T 19077.1-2016 / ISO 13320:2009 particle size distribution laser diffraction method. The Dv50 particle size of the lithium manganese iron phosphate material and the lithium iron phosphate material is tested according to the above method.

[0294] The test method for the charge capacity per gram of the negative electrode material at a 0.1C rate is as follows: the double-sided coated negative electrode sheet in the battery cell is disassembled, the negative electrode material is scraped off from one side of the negative current collector and weighed, and the same area of 6 negative electrode sheets is subjected to the above operation, and the average weight of the negative electrode material on one side of the negative electrode sheet is obtained. The same area of the single-sided negative electrode sheet is used to prepare a button cell, which is charged at a rate of 0.1C to the upper limit cutoff voltage at 25°C, and then charged at a constant voltage of 0.05C. After standing for 30 minutes, it is discharged at a rate of 0.1C to the lower limit cutoff voltage, and the charging and discharging are repeated twice. The last charging capacity is recorded as Cn. The test result is obtained by dividing the last charging capacity Cn by the weight of the negative electrode material on one side m.

[0295] The test method for the powder compaction density of the positive electrode material is as follows: the positive electrode sheet of the battery cell is washed with DMC (dimethyl carbonate), and the positive electrode sheet is dried and calcined to collect the positive electrode material in the positive active layer. The positive electrode material powder is weighed in the compaction density tester mold, and the tester automatically applies a target pressure to the powder to compact it. According to the cross-sectional area of the mold and the thickness of the powder at this time, the volume of the powder can be calculated. According to the compaction density = mass / volume, the powder compaction density result can be measured.

[0296] Battery cell test

[0297] (1) Volume energy density test of battery cell:

[0298] The battery cell was charged at 0.33C constant current to 4.1V, and then charged at constant voltage to 0.05C at 25℃. The battery cell was discharged at 0.33C constant current to 2.5V, and the discharge capacity A0 and discharge platform voltage V at this time were recorded. The length, thickness and height of the battery cell were measured using a caliper (generally calculated based on the size of the shell of the battery cell, excluding the height of the electrode terminal, and excluding the insulating film outside the shell), and the volume V0 of the battery cell was calculated. The volume energy density VED of the battery cell was (A0xV) / V0, with the unit of Wh / L.

[0299] (2) Discharge internal resistance DCR test of battery cell:

[0300] The battery cell was charged at 0.33C constant current to 4.1V, and then charged at constant voltage to 0.05C at 25℃. The battery cell was discharged at 0.33C constant current to 2.0V, and the discharge capacity A0 and discharge platform voltage V at this time were recorded. The length, thickness and height of the battery cell were measured using a caliper (generally calculated based on the size of the shell of the battery cell, excluding the height of the electrode terminal, and excluding the insulating film outside the shell), and the volume V0 of the battery cell was calculated. The volume energy density VED of the battery cell was (A0xV) / V0, with the unit of Wh / L.

[0301] After the above discharge was completed, the battery cell was charged at 0.33Cn constant current to 0.5Cn capacity (i.e. charged to 50% SOC), and then rested for 60min. The voltage V0 after stabilization was recorded. Then, the battery cell was discharged at 2Cn rate for 10s at 25℃, and the 10th second voltage V1 and discharge current Ic were taken.

[0302] The DCR of 50% SOC discharged at 2C for 10s was (V1-V0) / Ic, with the unit of mΩ.

[0303] Discharge power = V min x (OCVdis-V min ) / DCR;

[0304] Wherein, V min is the lower limit voltage 2V allowed during discharge, and OCVdis is the open circuit voltage value during discharge. Therefore, the discharge power is negatively correlated with the discharge DCR.

[0305] In the following table, the chemical formula of the lithium iron manganese phosphate material also contains M1 elements in addition to Li, Fe, and Mn. The mass content of the M1 elements in the lithium iron manganese phosphate material is trace, and therefore is not expressed in the chemical formula. However, the M1 elements are still considered to be contained in the lithium iron manganese phosphate material shown in the table. The sum of the subscripts of Fe and Mn in the chemical formula of the lithium iron manganese phosphate material and the total number of moles of M1 elements in the chemical formula is 1. The chemical formula of the lithium iron phosphate material also contains M2 elements in addition to Li and Fe. The mass content of the M2 elements in the lithium iron phosphate material is trace, and therefore is not expressed in the chemical formula. However, the M2 elements are still considered to be contained in the lithium iron phosphate material shown in the table. The sum of the subscript of Fe in the chemical formula of the lithium iron phosphate material and the total number of moles of M2 elements in the chemical formula is 1. The M1 elements and the M2 elements can be the same or different.

[0306] From the above table, it can be seen that:

[0307] Compared with the positive electrode active material of Comparative Example 1 which only contains lithium iron phosphate material, the energy density of the battery cell of the present application Examples 1-12 is significantly improved.

[0308] Compared with the positive electrode active material of Comparative Example 2 in which the mass content of lithium manganese iron phosphate is too low, the energy density of the battery cell of the present application Examples 1-12 is significantly improved.

[0309] Compared with the positive electrode active material of Comparative Example 3 which only contains lithium manganese iron phosphate material, the power performance of the battery cell of the present application Examples 1-12 is significantly improved.

[0310] Compared with the positive electrode material of Comparative Example 4 in which the powder resistivity at 12 MPa is too high, the power performance of the battery cell of the present application Examples 1-12 is significantly improved.

[0311] Compared with Example 1, the present application Examples 2 and 4 increase the mass content of lithium manganese iron phosphate in the positive electrode active material, which can improve the energy density of the battery cell.

[0312] Compared with Example 1, the present application Example 3 reduces the mass content of lithium manganese iron phosphate in the positive electrode active material, which can improve the power performance of the battery cell.

[0313] Compared with Example 1, the present application Examples 5 and 8 reduce the powder resistivity of the positive electrode material and reduce the molar ratio of manganese to iron of the lithium manganese iron phosphate material, which can improve the power performance of the battery cell.

[0314] Compared with Example 1, the present application Examples 6 and 7 increase the powder resistivity of the positive electrode material and increase the molar ratio of manganese to iron of the lithium manganese iron phosphate material, which can improve the energy density of the battery cell.

[0315] Compared with example 1, the present embodiment 9 simultaneously increases the surface density of the positive active layer and the negative active layer in the battery 100% SOC state, which can improve the energy density of the battery monomer.

[0316] Compared with example 1, the present embodiment 10 increases the mass proportion of silicon element in the negative active material, which can improve the energy density of the battery monomer.

[0317] Compared with example 1, the present embodiment 11 does not include silicon element in the negative active material, which can improve the power performance of the battery monomer.

[0318] Compared with example 12, the present embodiment 1 adopts double-layer negative active layer, which is conducive to improving the power performance of the battery monomer.

[0319] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications of the embodiments that can be thought of by those skilled in the art, as well as other ways constructed by combining part of the constituent elements in the embodiments, are also included in the scope of the present application.

Claims

A battery monomer comprises a positive electrode sheet and a negative electrode sheet, wherein, The negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer arranged on at least one side of the negative electrode current collector, the negative electrode active layer comprising a negative electrode material, the negative electrode material comprising graphite; The positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer arranged on at least one side of the positive electrode current collector, the positive electrode active layer comprising a positive electrode material, the positive electrode material comprising a positive electrode active material, The positive electrode active material comprises a lithium manganese iron phosphate material and a lithium iron phosphate material, the mass percentage of the lithium manganese iron phosphate material in the positive electrode active material being 50%-95%, and the powder resistivity of the positive electrode material under 12MPa being 5-70Ω·cm. The battery cell of claim 1, wherein, The mass percentage of the lithium manganese iron phosphate material in the positive electrode active material is 50%-70%. The battery cell according to claim 1 or 2, wherein The powder resistivity of the lithium manganese iron phosphate material under 12MPa is 8-120Ω·cm, and optionally 8-80Ω·cm. The battery cell of any one of claims 1 to 3, wherein, The volume average particle size Dv50 of the lithium manganese iron phosphate material is 0.1μm-1.2μm, and optionally 0.2μm-0.8μm. The battery cell of any one of claims 1 to 4, wherein The molar ratio of manganese atoms to iron atoms in the lithium manganese iron phosphate material is 2:8-8:

2. The battery cell of any one of claims 1 to 5, wherein, The powder resistivity of the lithium iron phosphate material under 12MPa is 3-100Ω·cm, and optionally 3-20Ω·cm. The battery cell of any one of claims 1 to 6, wherein, The volume average particle size Dv50 of the lithium iron phosphate material is 0.9-1.9μm. The battery cell of any one of claims 1 to 7, wherein, The battery cell has a surface density of the positive electrode active layer of 200-450 mg / 1540.25 mm in a 100% SOC state 2 , optionally 290-350 mg / 1540.25 mm 2 . The battery cell of any one of claims 1 to 8, wherein, The compaction density of the positive electrode active layer is 2.27-2.67 g / cm 3 , and optionally 2.37-2.62 g / cm 3 . The battery cell of any one of claims 1 to 9, wherein, The battery cell has a surface density of the negative electrode active layer of 100-180 mg / 1540.25 mm in a 100% SOC state 2 . The battery cell of any one of claims 1 to 10, wherein, The compaction density of the negative active layer of the battery cell is 1.2-1.45 g / cm 3 , and the compaction density of the negative active layer of the battery cell is 1.28-1.44 g / cm 3 . The battery cell of any one of claims 1 to 11, wherein, The negative electrode material further comprises a silicon material. The battery cell of claim 12, wherein, The silicon-containing material comprises one or more of a silicon oxide compound and a silicon carbon compound; and / or, The mass percentage of silicon in the negative electrode material is 0.3%-10%, and optionally 1%-6%, based on the mass of the negative electrode material. The battery cell of any one of claims 1 to 13, wherein, The chemical formula of the lithium iron phosphate material is Li x Fe (1-s) M s P y O z wherein x is greater than or equal to 0.5 and less than or equal to 1.3, s is greater than or equal to 0 and less than 1, y is greater than or equal to 0.5 and less than or equal to 1.3, z is greater than or equal to 3 and less than or equal to 5, M includes one or more elements selected from B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Hf, Ni, Co, Ru, Ag, Pb; and / or, The chemical formula of the lithium iron manganese phosphate material is Li x Fe (1-t-s) Mn t M s P y O z , wherein x is greater than or equal to 0.5 and less than or equal to 1.3, t is greater than 0 and less than 1, s is greater than or equal to 0 and less than 1, 1-t-s is greater than 0 and less than 1, y is greater than or equal to 0.5 and less than or equal to 1.3, z is greater than or equal to 3 and less than or equal to 5, and M includes one or more elements selected from B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Hf, Ni, Co, Ru, Ag, Pb. The battery cell of any one of claims 1 to 14, wherein, The powder compaction density of the positive electrode material is 2.2-2.8 g / cm 3 , and optionally 2.3-2.8 g / cm 3 . The battery cell of any one of claims 1 to 15, wherein, The positive electrode sheet further comprises a positive electrode conductive layer arranged between the positive electrode current collector and the positive electrode active layer. The battery cell of claim 16, wherein, The thickness of the positive electrode conductive layer is 0.5-2μm. The battery cell according to claim 16 or 17, wherein The positive electrode conductive layer comprises one or more of a positive electrode conductive agent and a positive electrode binder. The battery cell of claim 18, wherein One or more of the following: The positive electrode conductive agent comprises one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; The positive electrode conductive agent at least comprises superconducting carbon and carbon nanotubes; The positive electrode binder comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorine-containing acrylic ester resin. The battery cell according to claim 18 or 19, wherein The mass percentage of the positive electrode conductive agent is 30%-50%, based on the mass of the positive electrode conductive layer; and / or, The mass percentage of the positive electrode binder is 50%-70%, based on the mass of the positive electrode conductive layer. The battery cell of any one of claims 1 to 20, wherein, The negative electrode sheet further comprises a negative electrode conductive layer arranged between the negative electrode current collector and the negative electrode active layer. The battery cell of claim 21, wherein, The thickness of the negative electrode conductive layer is 0.5-2μm. The battery cell according to claim 21 or 22, wherein The negative electrode conductive layer comprises one or more of a negative electrode conductive agent and a negative electrode binder. The battery cell of claim 23, wherein, The negative electrode conductive agent comprises one or more of super-conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; and / or, The negative electrode binder comprises one or more of styrene butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan. The battery cell according to claim 23 or 24, wherein The mass percentage of the negative electrode conductive agent is 20%-40% based on the mass of the negative electrode conductive layer; and / or, The mass percentage of the negative electrode binder is 60%-80% based on the mass of the negative electrode conductive layer. The battery cell of any one of claims 1 to 25, wherein, The negative electrode active layer is a single-layer or multi-layer structure, and the volume average particle size Dv50 of the negative electrode material in the negative electrode active layer is 7.5-19.5 μm. The battery cell of any one of claims 1 to 26, wherein, The negative electrode active layer is a single-layer structure, and the volume average particle size Dv50 of the negative electrode material is 8.0-17.5 μm. The battery cell of any one of claims 1 to 27, wherein, The negative electrode active layer comprises a first negative electrode active layer close to the negative electrode current collector and a second negative electrode active layer disposed on the first negative electrode active layer. The battery cell of claim 28, wherein, The thickness ratio of the second negative electrode active layer to the first negative electrode active layer is 2:8-8:

2. The battery cell of claim 28 or 29, wherein, The volume average particle size Dv50 of the negative electrode active material in the first negative electrode active layer is 7.5-19.5 μm, and optionally 12.5-18.5 μm. The battery cell of any one of claims 28-30, wherein, The volume average particle size Dv50 of the negative electrode active material in the second negative electrode active layer is 7.5-19.5 μm, and optionally 7.5-15.5 μm. The battery cell of any one of claims 28-31, wherein, The volume average particle size Dv50 of the negative electrode active material in the second negative electrode active layer is smaller than the volume average particle size Dv50 of the negative electrode active material in the first negative electrode active layer. The battery cell of any one of claims 28-32, wherein, The graphite in the first negative electrode active layer is selected from one or more of natural graphite and composite graphite; and / or, The graphite in the second negative electrode active layer is selected from one or more of composite graphite. The battery cell of claim 33, wherein, The composite graphite comprises a body and a coating layer coated on the surface of the body; the body comprises artificial graphite, and the coating layer comprises amorphous carbon. The battery cell of claim 33 or 34, wherein The composite graphite comprises secondary particles. The battery cell of any one of claims 33-35, wherein, The powder resistivity of the composite graphite at 8 MPa is 0.01-0.04 Ω·cm. The battery cell of any one of claims 1 to 36, wherein, The battery cell further comprises an electrolyte, and the conductivity of the electrolyte at room temperature is 10-20 mS / cm, and optionally 12-17 mS / cm. The battery cell of any one of claims 1 to 37, wherein, The volumetric energy density of the battery cell is 400-550 Wh / L, and optionally 450-500 Wh / L. A battery device comprising the battery cell of any one of claims 1-38; the battery device comprises a battery module, a battery pack, or an energy storage device. A power utilization device comprising the battery cell of any one of claims 1-38 or the battery device of claim 39.

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