Battery monomer, battery device and electric device

Abstract

The invention provides a battery monomer, a battery device and a power utilization device. Each battery monomer comprises a shell and an electrode assembly in the shell, the electrode assembly comprises a positive pole piece, a negative pole piece and an isolating membrane between the two pole pieces, the positive pole piece comprises a positive current collector and a positive active layer arranged on at least one side of the positive current collector, and the positive active layer comprises a positive active material; the positive electrode active material comprises a nickel-containing lithium transition metal oxide and a lithium-containing phosphate, the molar weight of the Ni element in the nickel-containing lithium transition metal oxide accounts for 70-95% of the total molar weight of the transition metal, the positive electrode active material comprises Ni, Co, Mn, Fe and Li elements, and the ratio of the mass of the Ni element in the positive electrode active material to the sum of the mass of the Fe element and the mass of the Mn element is 0.15-2.

Description

Technical Field

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

[0002] With the popularization and development of electric vehicles, the performance requirements for battery devices are gradually increasing. Currently, they not only need to have high energy density and fast charging rate to reduce users' mileage anxiety, but also need to have high cycle stability to improve battery life and safety performance.

[0003] However, when the energy density of a battery device is high and its electrodes are in a highly lithium-intercalated or lithium-extracted state, the battery stability often decreases, causing degradation of the positive electrode structure, side reactions at the interface, and dramatic changes in the negative electrode volume. There is a trade-off between energy density and cycle stability. Therefore, how to improve cycle performance while increasing the energy density of the battery device is one of the key goals of current battery research. Summary of the invention

[0004] The present application provides a battery cell, a battery device and an electrical device, which can achieve high electrode energy density while improving cycle performance.

[0005] The first aspect of the present application provides a battery cell, comprising a shell and an electrode assembly located inside the shell, the electrode assembly comprising a positive electrode plate, a negative electrode plate, and a separator located between the positive electrode plate and the negative electrode plate, wherein the negative electrode plate comprises a negative electrode collector and a negative electrode active layer arranged on at least one side of the negative electrode collector, the negative electrode active layer comprises a negative electrode active material, the negative electrode active material comprises graphite, the positive electrode plate comprises a positive electrode collector and a positive electrode active layer arranged on at least one side of the positive electrode collector, the positive electrode active layer comprises a positive electrode active material, the positive electrode active material comprises a nickel-containing lithium transition metal oxide and a lithium-containing phosphate, the molar amount of the Ni element in the nickel-containing lithium transition metal oxide accounts for 70% to 95% of the total molar amount of the transition metal; the lithium-containing phosphate comprises Mn and Fe elements, and the ratio of the mass of the Ni element in the positive electrode active material to the sum of the mass of the Fe element and the Mn element in the positive electrode active material is between 0.15 and 2.

[0006] In any embodiment of the first aspect, the ratio of the mass of the Ni element in the positive electrode active material to the sum of the mass of the Fe element and the Mn element in the positive electrode active material is between 0.55 and 1.42.

[0007] In any embodiment of the first aspect, the mass content of the lithium-containing phosphate in the positive electrode active material is 50%-90%, and optionally 50%-70%.

[0008] In any embodiment of the first aspect, in the nickel-containing lithium transition metal oxide, the molar amount of Ni element accounts for 80%-95% of the total molar amount of nickel, cobalt and manganese elements.

[0009] In any embodiment of the first aspect, the nickel-containing lithium transition metal oxide includes a lithium-containing nickel-cobalt-manganese oxide, and the lithium-containing nickel-cobalt-manganese oxide contains one or more of the elements Zr, Al, B, Fe, Ca, Sr, Ti, V or Y.

[0010] In any embodiment of the first aspect, the lithium-containing nickel-cobalt-manganese oxide includes one or more of the elements Zr, Al, B or Fe; optionally, in the lithium-containing nickel-cobalt-manganese oxide, the mass content of the elements satisfies at least one: the content of Zr is 1000-3000 ppm, the content of Al is 100-1000 ppm, and the content of B is 50-300 ppm.

[0011] In any embodiment of the first aspect, the lithium-containing phosphate includes lithium manganese iron phosphate, and the molar amount of Mn element in the lithium manganese iron phosphate is 20%-80% of the total molar amount of transition metal elements, optionally 30%-70%, and further optionally 30%-50%.

[0012] In any embodiment of the first aspect, the lithium manganese iron phosphate contains one or more of Al, B, Ca, Cr, Cu, K, Mg, Na, P, Si, Ti, V or Zn elements, and optionally the lithium manganese iron phosphate includes one or more of Al, Ca, Na, Ti or V elements; further optionally, in the lithium manganese iron phosphate, the mass content of the elements satisfies at least one: the Al content is 100-1000ppm, the Ca content is 50-300ppm, the Na content is 50-300ppm, the Ti content is 100-1000ppm, and the V content is 1000-3000ppm.

[0013] In any embodiment of the first aspect, the positive electrode active layer contains lithium manganese iron phosphate and lithium-containing nickel cobalt manganese oxide, and the positive electrode active material contains one or more of Al, B, Ca, Na, Sr, Ti, V, Y or Zr elements, and based on the total mass of the positive electrode active material, the mass content of each element satisfies: Al: 0.005%-0.1%; Ca: 0.0001%-0.02%; Na: 0.005%-0.06%; Ti: 0.005%-0.15%; V: 0.0001%-0.3%; Zr: 0.005%-0.2%; B: 0.01%-0.1%.

[0014] In any embodiment of the first aspect, the positive electrode active layer includes a first active layer and a second active layer, the first active layer is arranged close to the positive electrode current collector, and the second active layer is arranged on a side of the first active layer away from the positive electrode current collector, based on the total mass of the positive electrode active layer, the mass content of the Ni element in the first active layer is less than the mass content of the Ni element in the second active layer, and the mass content of the Fe element in the first active layer is greater than the mass content of the Fe element in the second active layer.

[0015] In any embodiment of the first aspect, the battery monomer further comprises a non-aqueous electrolyte, the non-aqueous electrolyte comprises a solvent and a lithium salt, the solvent comprises a cyclic carbonate and a linear carbonate; optionally, the cyclic carbonate comprises ethylene carbonate (EC); optionally, the linear carbonate comprises one or more of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC); optionally, the mass ratio of the cyclic carbonate to the linear carbonate is 2:8 to 5:5.

[0016] In any embodiment of the first aspect, the electrolyte injection coefficient of the battery cell is 1.8 g / Ah-3.5 g / Ah, and can be optionally 1.9 g / Ah-3.1 g / Ah.

[0017] A second aspect of the present application provides a battery device, comprising any one of the battery cells of the first aspect, and the battery device comprises a battery module, a battery pack or an energy storage device.

[0018] A third aspect of the present application provides an electrical device, comprising any one of the battery cells of the first aspect, or the battery device of the second aspect.

[0019] The present application can achieve simultaneous regulation of energy density and cycle life through the design of the positive electrode active material, so that the energy density of the battery cell can be fully utilized while having good cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0021] Figure 1 It is a schematic diagram of a battery assembly according to one embodiment of the present application.

[0022] Figure 2 yes Figure 1 An exploded view of a battery cell according to an embodiment of the present application is shown.

[0023] Figure 3It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0024] Figure 4 yes Figure 3 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0025] Figure 5 It is a schematic diagram of an electrical device using a battery cell according to an embodiment of the present application as a power source.

[0026] In the drawings, the drawings are not drawn to scale.

[0027] Description of reference numerals:

[0028] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0029] The following detailed description and drawings of the embodiments of the present application are used to illustrate the principles of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0030] Below, the embodiments of the secondary battery and the electrical device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure 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 drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0031] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0032] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0033] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0034] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0035] If there is no special explanation, the "include" and "comprising" mentioned in this application represent open-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or comprised.

[0036] If not otherwise specified, in this application, the term "or" is inclusive. For example, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0037] [Battery Cell]

[0038] As mentioned above, improving the energy density of the battery while improving the cycle performance is one of the focuses of the current battery research field. The present application provides a battery cell, including a shell and an electrode assembly located inside the shell, the electrode assembly including a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet, wherein the negative electrode sheet includes a negative electrode collector and a negative electrode active layer arranged on at least one side of the negative electrode collector, the negative electrode active layer includes a negative electrode active material, the negative electrode active material includes graphite, the positive electrode sheet includes a positive electrode collector and a positive electrode active layer arranged on at least one side of the positive electrode collector, the positive electrode active layer includes a positive electrode active material, the positive electrode active material includes a nickel-containing lithium transition metal oxide and a lithium-containing phosphate, the molar amount of the Ni element in the nickel-containing lithium transition metal oxide accounts for 70% to 95% of the total molar amount of the transition metal; the lithium-containing phosphate includes Mn and Fe elements, and the ratio of the mass of the Ni element in the positive electrode active material to the sum of the mass of the Fe element and the Mn element in the positive electrode active material is between 0.15 and 2.

[0039] The present application aims to develop a low-cost lithium-ion battery cell with both high energy density and good cycle performance. Compared with pure nickel-containing lithium transition metal oxides, lithium-containing phosphate materials have significant low-cost advantages. The mixed use of the two can give full play to the high gram capacity advantage of nickel-cobalt-manganese oxide materials at a low cost advantage and improve the energy density of battery cells. However, the present application unexpectedly discovered that when the Ni content, Mn content, and Fe content in the mixed nickel-containing lithium transition metal oxide and lithium-containing phosphate positive electrode active materials not only affect the energy density of the battery cell, but also have a significant effect on the cycle performance of the battery cell. The present application hopes to obtain a battery cell with both high energy density and long cycle life in the mixed nickel-containing lithium transition metal oxide and lithium-containing phosphate system.

[0040] The battery cell of the present application includes a nickel-containing lithium transition metal oxide and a positive electrode active material containing lithium phosphate. The nickel-containing lithium transition metal oxide has a high molar amount of Ni element (the molar amount of Ni element accounts for 70% to 95% of the total molar amount of transition metals), and is a high-nickel lithium transition metal oxide, which helps to improve the energy density of the battery cell. However, if too much high-nickel lithium transition metal oxide is added in order to improve the energy density of the battery cell, the proportion of lithium phosphate material will be too small, thereby making the proportion of Ni element content, Mn element content, and Fe element in the positive electrode active material unbalanced, affecting the cycle performance of the battery cell. Therefore, the present application further controls the relative proportion of Ni element content, Mn element content, and Fe element, that is, by limiting the ratio of the mass of Ni element in the positive electrode active material to the sum of the mass of Fe element and Mn element in the positive electrode active material to between 0.15 and 2, so that the relative contents of high-nickel lithium transition metal oxide and lithium phosphate in the positive electrode active material are maintained within a reasonable range, so that the battery cell has both high energy density and cycle performance.

[0041] Specifically, when the molar amount of Ni in the nickel-containing lithium transition metal oxide is in the range of 70% to 95%, and the ratio of the mass of Ni in the positive electrode active material to the sum of the mass of Fe and Mn in the positive electrode active material is less than 0.15, it means that the content of lithium-containing phosphate in the positive electrode active material is too high, corresponding to the excessively high content of Mn and Fe in the positive electrode active material, which makes it easy for Mn and Fe to escape from the lithium-containing phosphate skeleton and cause transition metal dissolution, thereby reducing the cycle performance of the battery cell; correspondingly, when the molar amount of Ni in the nickel-containing lithium transition metal oxide is in the range of 70% to 95%, the ratio of the mass of Ni in the positive electrode active material to the sum of the mass of Fe and Mn in the positive electrode active material is less than 0.15. Within the range of 5%, when the ratio of the mass of Ni element in the positive electrode active material to the sum of the mass of Fe element and Mn element in the positive electrode active material is greater than 2, it means that the content of high-nickel lithium transition metal oxide in the positive electrode active material is too high, corresponding to the excessively high content of Ni element in the positive electrode active material. At this time, although the energy density of the battery cell is high, the structural stability of the high-nickel lithium transition metal oxide is poor, and the Ni element is easy to escape from the skeleton structure of the high-nickel lithium transition metal oxide. In addition, the surface residual alkali of the high-nickel lithium transition metal oxide is also high, and it is easy to have side reactions with the electrolyte, thereby reducing the cycle performance of the battery cell.

[0042] The present application reasonably controls the molar amount of the Ni element in the nickel-containing lithium transition metal oxide, and the ratio of the mass of the Ni element in the positive electrode active material to the sum of the mass of the Fe element and the Mn element in the positive electrode active material within a reasonable range, so that the battery cell has low cost, high energy density and good cycle performance.

[0043] In some embodiments, the ratio of the mass of Ni element in the positive electrode active material to the sum of the mass of Fe element and Mn element in the positive electrode active material is between 0.55 and 1.42, such as 0.55, 0.60, 0.62, 0.64, 0.66, 07, 0.8, 0.9, 0.97, 1.0, 1.1, 1.2, 1.3, 1.4 or 1.42.

[0044] When the Ni content in the nickel-containing lithium transition metal oxide is relatively high, the ratio of the mass of the Ni element in the above-mentioned positive electrode active material to the sum of the masses of the Fe and Mn elements makes the content of the nickel-containing lithium transition metal oxide in the positive electrode active material relatively high, thereby improving the energy density of the battery cell and better improving the cycle performance of the battery cell.

[0045] In some embodiments, the mass content of lithium phosphate in the positive electrode active material is 50%-90%, such as 50%, 55%, 60%, 65%, 70%, 75%, 80% or 90%, and 50%-70% is optional. When the mass content of lithium phosphate in the positive electrode active material is within the above range, the battery cell has a higher energy density.

[0046] In nickel-containing lithium transition metal oxides, increasing the Ni content can effectively increase the gram capacity of the material system, thereby further increasing the energy density of the battery cell. In addition, in a low temperature environment, the capacity retention rate of the nickel-containing lithium transition metal oxide is high and has good low-temperature stability. In some embodiments, in the nickel-containing lithium transition metal oxide, the molar amount of the Ni element accounts for 80%-95% of the total molar amount of nickel, cobalt and manganese elements. Increasing the molar percentage of the Ni element is beneficial to improving the energy density of the entire multi-system hybrid positive electrode plate, and controlling the molar percentage of the Ni element to no more than 95%, improving the structural stability of the nickel-containing lithium transition metal oxide, and also reducing the side reactions with the battery cell, so as to optimize the cycle performance and safety performance of the battery cell.

[0047] In some embodiments, the nickel-containing lithium transition metal oxide includes a lithium-containing nickel-cobalt-manganese oxide, and the lithium-containing nickel-cobalt-manganese oxide contains one or more of the elements Zr, Al, B, Fe, Ca, Sr, Ti, V or Y. The above elements may be present in the nickel-containing lithium transition metal oxide in the form of doping or coating.

[0048] The energy density of nickel-containing lithium transition metal oxides (especially high-nickel ternary material systems) is high, but there are defects such as element mixing, phase change, poor thermal stability, microcracks, and the cycle stability and life need to be improved. In order to improve the comprehensive performance of lithium-containing nickel-cobalt-manganese oxides, they can be modified by methods such as doping, modification, compounding, and morphology control. For example, including cation doping, anion doping, and co-doping of multiple ions, for example, Zr, Al, Fe, Ca, Sr, Ti, V, and Y can be used as cation doping elements, and B can be used as anion doping elements. In some embodiments, Zr can occupy Ni and Li positions at the same time, reduce the mixing between Ni and Li, and improve ionic conductivity. There is a strong chemical bond between Zr and O, which is conducive to stabilizing the crystal structure of the layered material and plays a supporting role in the process of stripping / inserting lithium. Al is dissolved in the transition metal layer of lithium-containing nickel-cobalt-manganese oxide in the form of a solid solution, which can effectively improve the capacity retention during the cycle. B, as an anion doping, can alleviate the strain of lithium-containing nickel-cobalt-manganese oxide during the lithiation / delithiation process, and improve the cycle stability and life.

[0049] In some embodiments, the lithium-containing nickel-cobalt-manganese oxide includes one or more of Zr, Al, B or Fe elements; optionally, in the lithium-containing nickel-cobalt-manganese oxide, the mass content of the elements satisfies at least one of the following: Zr content of 1000-3000 ppm, Al content of 100-1000 ppm, and B content of 50-300 ppm. This is conducive to a better balance between cycle stability and gram capacity.

[0050] In some embodiments, the lithium-containing phosphate includes lithium iron manganese phosphate, and the molar amount of the Mn element in the lithium iron manganese phosphate is 20%-80% of the total molar amount of the non-lithium metal elements, such as 20%, 30%, 40%, 50%, 60%, 70% or 80%, optionally 30%-70%, and further optionally 30%-50%. When the molar percentage content of the Mn element in the non-lithium metal elements of the lithium-containing phosphate is within the above range, the gram capacity of the lithium-containing phosphate can be maintained as high as possible, and the voltage platform of the battery cell can be increased, thereby improving the energy density of the battery cell.

[0051] In some embodiments, lithium manganese iron phosphate contains one or more of Al, B, Ca, Cr, Cu, K, Mg, Na, P, Si, Ti, V or Zn elements, and lithium manganese iron phosphate includes one or more of Al, Ca, Na, Ti or V elements; further optionally, in lithium manganese iron phosphate, the mass content of the elements satisfies at least one: the Al content is 100-1000ppm, the Ca content is 50-300ppm, the Na content is 50-300ppm, the Ti content is 100-1000ppm, and the V content is 1000-3000ppm.

[0052] Doping one or more of the above elements into lithium-containing phosphates can promote the Li + The lattice migration can improve the conductivity of the material. For example, Mg doping can improve the conductivity and improve the structural stability; Al doping can improve the conductivity of the material and help suppress the phase change under high voltage or deep discharge; Ca doping can improve the cycle stability; Na doping can promote the ion diffusion rate and improve the specific capacity; Ti doping can provide additional Li + sites, improve the specific capacity, and help reduce the dissolution of Mn during the cycle; V doping can improve the conductivity and electrochemical activity, and improve the charge and discharge performance.

[0053] In some embodiments, the positive electrode active layer contains lithium manganese iron phosphate and lithium-containing nickel cobalt manganese oxide, and the positive electrode active material contains one or more of Al, B, Ca, Na, Sr, Ti, V, Y or Zr elements, and based on the total mass of the positive electrode active material, the mass content of each element satisfies: Al: 0.005%-0.1%; Ca: 0.0001%-0.02%; Na: 0.005%-0.06%; Ti: 0.005%-0.15%; V: 0.0001%-0.3%; Zr: 0.005%-0.2%; B: 0.01%-0.1%. The energy density of the battery cell with the above characteristics can be maintained at a high level, and the cycle life is longer, which has more safety advantages.

[0054] The elements in the above materials can be determined by the following methods:

[0055] The positive electrode sheet of the battery cell was fully cleaned with dimethyl carbonate (DMC), and the positive electrode sheet was dried and calcined before collecting the positive electrode material in the positive electrode active layer. The positive electrode material was tested using inductively coupled plasma atomic emission spectrometry (ICP-OES).

[0056] In some embodiments, the positive electrode active layer includes a first active layer and a second active layer, the first active layer is arranged close to the positive electrode current collector, and the second active layer is arranged on the side of the first active layer away from the positive electrode current collector. Based on the total mass of the positive electrode active layer, the mass content of Ni in the first active layer is less than the mass content of Ni in the second active layer, and the mass content of Fe in the first active layer is greater than the mass content of Fe in the second active layer. The first active layer is arranged close to the current collector, wherein the positive electrode active material is mainly lithium-containing phosphate; the second active layer is arranged away from the positive electrode current collector, that is, in contact with the electrolyte, wherein the positive electrode active material is mainly nickel-containing lithium transition metal oxide. The use of nickel-containing lithium transition metal oxide can block the side reaction of lattice water in lithium-containing phosphate and electrolyte, thereby improving the cycle life of the battery cell.

[0057] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0058] In some embodiments, the positive electrode film layer may further include a conductive agent, for example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0059] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0060] [Electrolytes]

[0061] In some embodiments, the battery cell further includes an electrolyte. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0062] In some embodiments, the battery cell includes a non-aqueous electrolyte, the non-aqueous electrolyte includes a solvent, the solvent includes a cyclic carbonate and a linear carbonate; optionally, the cyclic carbonate includes ethylene carbonate (EC); optionally, the linear carbonate includes one or more of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC); optionally, the mass ratio of the cyclic carbonate to the linear carbonate is 2:8 to 5:5. The cyclic carbonate has a large dielectric constant, which is conducive to promoting the dissociation of lithium salts, and the linear carbonate has a low viscosity, which is conducive to Li + Migration of ions. When the mass ratio of cyclic carbonate to linear carbonate is in the range of 2:8 to 5:5, the oxidation resistance of the electrolyte can be significantly improved, which is beneficial to prolonging the cycle life of the battery cell.

[0063] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0064] In some embodiments, the electrolyte may further include additives. As examples, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0065] In some embodiments, the electrolyte injection coefficient of the battery cell is 1.8-3.5 g / Ah, and can be 1.9-3.1 g / Ah. When the battery cell operates normally, a small electrolyte injection coefficient is beneficial to reduce the degree of deterioration of side reactions caused by the electrolyte and improve the cycle life of the battery cell.

[0066] [Negative electrode]

[0067] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active layer is disposed on any one or both of the two facing surfaces of the negative electrode current collector.

[0068] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0069] In some embodiments, the graphite of the negative electrode active material includes artificial graphite and natural graphite. In addition, in some embodiments, the negative electrode active material may also include soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0070] In some embodiments, the negative electrode film layer may further include a binder. As an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0071] In some embodiments, the negative electrode film layer may further include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0072] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0073] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0074] [Isolation film]

[0075] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0076] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0077] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0078] The second embodiment of the present application further provides a battery device, comprising any one of the battery cells provided in the first embodiment, and the battery device includes a battery module, a battery pack or an energy storage device.

[0079] In some embodiments, the battery device may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0080] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0081] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square or any other shape. Figure 1 The electrode assembly 52 is a square structure as an example.

[0082] In some embodiments, reference Figure 2 , the outer packaging may include a shell 51 and a top cover assembly 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0083] In some embodiments, secondary battery cells may be assembled into a battery module. The number of secondary battery cells contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0084] In the battery module 4, the plurality of battery cells may be arranged in sequence along the thickness direction of the battery cells. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells may be fixed by fasteners.

[0085] Optionally, the battery module may further include a housing having a receiving space, and a plurality of battery cells are received in the receiving space.

[0086] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0087] Figure 3 and Figure 4 1 is a battery pack 1 as an example. Figure 3 and Figure 4The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0088] In addition, the present application also provides an electric device, which includes a battery cell or a battery device provided in the present application. The battery cell or the battery device can be used as a power source for the electric device, or as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0089] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0090] Figure 5 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device's requirements for high power and high energy density of battery cells, a battery pack or a battery module can be used.

[0091] [Example]

[0092] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0093] Example 1

[0094] Positive electrode:

[0095] The positive electrode active layer includes a positive electrode active material, a binder polyvinylidene fluoride, and a conductive agent acetylene black (mass ratio is 96.7:2.3:1). In the positive electrode active material, the mass ratio of the nickel-containing lithium transition metal oxide to the lithium-containing phosphate is 3:7. The chemical formula of the nickel-containing lithium transition metal oxide is Li(Ni 0.90 Co 0.05 Mn 0.05 ) 2 The chemical formula of lithium phosphate is Li(Fe 0.5 Mn 0.5 )PO 4, the ratio of the Ni element mass to the sum of the Fe element and the Mn element mass is 0.64.

[0096] The other elements in the positive electrode active material are all from lithium transition metal oxides containing nickel. The subscripts of Ni, Co and Mn in the chemical formula are rounded data. Because the content of other elements M is trace or even lower, these elements and their molar numbers are not reflected in the chemical formula. It does not mean that element M has no effect on the performance of the battery cell. In the chemical formula of Li(Ni 0.90 Co 0.05 Mn 0.05 ) 2 In the nickel-containing lithium transition metal oxide, the mass contents of the elements in the element M are: Al: 0.081%, B: 0.091%, Na: 0.0093%, S: 0.082%, Sb: 0.014%, Sr: 0.025%, W: 0.035%; Zr: 0.143%.

[0097] The thickness of the positive electrode current collector aluminum foil is 13μm, the positive electrode film layer is located on both sides of the aluminum foil, and there is a conductive primer layer between the positive electrode film layer and the aluminum foil. The conductive primer layer is a film layer formed by mixing the positive electrode conductive agent superconducting carbon, the positive electrode binder polyacrylate and the solvent evenly and then coating it on the surface of the positive electrode current collector and drying it. The thickness is 1μm, the mass content of the positive electrode conductive agent in the negative electrode conductive layer is 50%, and the mass content of the positive electrode binder in the negative electrode conductive layer is 50%. The length of the positive electrode sheet is 592mm.

[0098] The coating density of the positive electrode is 315mg / 1540.25mm 2 .

[0099] Negative electrode:

[0100] The negative electrode active layer includes negative electrode active material graphite, conductive agent acetylene black, binder styrene butadiene rubber and thickener sodium carboxymethyl cellulose in a mass ratio of 96:1:2:1.

[0101] The negative electrode current collector is a copper foil of 5 μm, there is a negative electrode conductive layer between the copper foil and the lower film layer, the conductive primer is a film layer formed by mixing the negative electrode conductive agent superconducting carbon, the negative electrode binder styrene-butadiene rubber SBR, the thickener sodium carboxymethyl cellulose (CMC-Na) and the solvent water evenly, and then coating it on the surface of the negative electrode current collector and drying it. The thickness is 1 μm, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 35%, the mass content of the negative electrode binder in the negative electrode conductive layer is 60%, and the mass content of the thickener in the negative electrode conductive layer is 5%.

[0102] The coating density of the negative electrode sheet is 160mg / 1540.25mm 2 .

[0103] The electrolyte includes an organic solvent, a lithium salt and an additive, wherein:

[0104] The organic solvent is a mixture of cyclic carbonate and linear carbonate, the cyclic carbonate is ethylene carbonate (EC), the linear carbonate is dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), EC, DMC, EMC, and DEC are mixed in a mass ratio of 30%:20%:20%:30%, and the mass ratio of cyclic carbonate to linear carbonate is 3:7;

[0105] The lithium salt is lithium hexafluorophosphate (LiPF 6 );

[0106] The electrolyte additive composition is as follows: 2.5wt% vinylene carbonate (VC), 1wt% fluoroethylene carbonate (FEC), 0.5wt% 1,3-propylene sultone (PS), 0.5wt% diethylene sulfite (DTD) and 0.5wt% lithium difluorophosphate (LiPO 2 F 2 ).

[0107] Preparation of isolation membrane:

[0108] A polyethylene (PE) film coated with an alumina inorganic coating and a PVDF organic coating was used as the separator. The thickness of the polyethylene film was 7 μm, and the separator was purchased from Zhuogao Technology Co., Ltd.

[0109] Preparation of battery cells:

[0110] The electrode assembly includes a stacked positive electrode sheet, a separator, and a negative electrode sheet. The electrode assembly is added to an outer square aluminum shell (length 600mm, thickness 19mm, height 105mm, shell wall thickness 1mm), and after drying, the electrolyte is injected, and the injection coefficient is 2.75g / Ah. After packaging, high-temperature standing, formation, secondary injection, aging, capacity and other processes, a battery cell is obtained.

[0111] The nickel-containing lithium transition metal oxides and lithium-containing phosphates used in the examples and comparative examples are all conventional materials in the art or are prepared using conventional methods.

[0112] The chemical formula is Li(Ni 0.93 Co 0.06 Mn 0.01 ) 2 、Li(Ni 0.95 Co 0.03 Mn 0.02 ) 2In the 9 series nickel-containing lithium transition metal oxides, the mass contents of each element in element M are: Al: 0.081%, B: 0.091%, Na: 0.0093%, S: 0.082%, Sb: 0.014%, Sr: 0.025%, W: 0.035%; Zr: 0.143%.

[0113] The chemical formula is Li(Ni 0.70 Co 0.10 Mn 0.20 ) 2 In the nickel-containing lithium transition metal oxide, the mass content of each element in the element M is: Al: 0.199%; Fe: 0.0016%; S: 0.141%; Sr: 0.045%; Ti: 0.0014%; W: 0.254%; Y: 0.0007%; Zr: 0.175%.

[0114] The chemical formula is Li(Ni 0.45 Co 0.18 Mn 0.37 ) 2 、Li(Ni 0.45 Co 0.25 Mn 0.30 ) 2 、Li(Ni 0.50 Co 0.20 Mn 0.30 ) 2 、Li(Ni 0.55 Co 0.05 Mn 0.40 ) 2 In the nickel-containing lithium transition metal oxide, the mass content of each element in the element M is: Al: 0.0054%; B: 0.0024%; Ca: 0.0032%; Cr: 0.0001%; ​​Cu: 0.0003%; Mg: 0.0037%; Na: 0.010%; S: 0.063%; Sr: 0.085%; Ti: 0.175%; W: 0.059%; Y: 0.0001%; ​​Zn: 0.0002%; Zr: 0.125%.

[0115] [Battery cell performance test]

[0116] Test method for volume energy density:

[0117] The battery cell is placed at 25°C, charged to 4.3V at a constant current rate of 0.33C, and then charged to 0.05C at a constant voltage. The discharge capacity A of the battery cell when it is discharged from 4.3V to 2.5V at a constant current rate of 0.33C is recorded. 0(Unit: Ah), C is the nominal capacity of the battery cell; use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the battery shell size, excluding the electrode terminal height and the insulating film outside the shell), and calculate the volume V of the single battery 0 , unit L; the volume energy density of the battery cell VED = (A 0 × discharge platform voltage) / V 0 , unit: Wh / L.

[0118] Cycle performance test method:

[0119] The battery cell was placed in a constant temperature environment of 25°C and charged and discharged between 2.5V and 4.3V. The specific operation was as follows: charge to 4.3V at 0.33C, then charge at a constant voltage at 4.3V until the current was no higher than 0.05C, let stand for 5 minutes, and then discharge to 2.5V at 1C. The capacity is recorded as C. m (m=1,2,3,…), repeat the above operation, the capacity retention rate is expressed as C m / C 3 The ratio indicates that when C m / C 3 ×100%=80%, record the corresponding number of cycles as an evaluation index of the cycle capacity. The more cycles, the better the cycle performance of the battery cell.

[0120] Based on Example 1, the following examples adjust the composition of the nickel-containing lithium transition metal oxide and the mass ratio of the nickel-containing lithium transition metal oxide and the lithium-containing phosphate in the positive electrode active material. The negative electrode sheet, electrolyte and separator are the same as those in Example 1.

[0121] The specific adjustment conditions are shown in Table 1. The battery cell performance test results of each embodiment are recorded in Table 1.

[0122] Table 1

[0123] The data T in Table 1 represents the mass content of lithium phosphate in the positive electrode active material.

[0124] The data in Table 1 illustrate that controlling the ratio of the mass of the Ni element to the sum of the masses of the Fe element and the Mn element (hereinafter referred to as the "Ni and (Fe+Mn) mass ratio") is beneficial to improving energy density and cycle life. If the Ni:(Fe+Mn) mass ratio is too low, such as in Comparative Examples 1 and 2, the energy density and cycle performance of the battery cell will deteriorate; if the Ni:(Fe+Mn) mass ratio is too high, such as in Comparative Examples 3 and 4, although the energy density of the battery cell is improved, the number of cycles is significantly reduced and the cycle life is sharply reduced. When the Ni:(Fe+Mn) mass ratio is between 0.15 and 2, the energy density and cycle performance of the battery cell are balanced at a high level.

[0125] The following examines the effect of the change in the molar ratio of the Mn element to the transition metal element in the lithium-containing phosphate on the energy density and cycle performance of the battery cell.

[0126] The nickel-containing lithium transition metal oxide used in Examples 5 to 8 is the same as that in Example 1, and all satisfy the mass ratio of the nickel-containing lithium transition metal oxide to the lithium-containing phosphate of 3:7. The negative electrode plate, electrolyte and isolation membrane are the same as those in Example 1. The variable settings and battery cell performance test results of each example are shown in Table 2.

[0127] Table 2

[0128] By comparing and analyzing the data of each embodiment in Table 2, it can be found that:

[0129] There is a nonlinear relationship between the molar percentage of the Mn element in the transition metal element in the lithium-containing phosphate and the performance of the battery cell. When the molar percentage is 30%-50%, the energy density and cycle life of the battery cell have relatively better performance.

[0130] Next, by adjusting the mass content of lithium-containing phosphate in the positive electrode active material, the effect of the mass ratio of nickel-containing lithium transition metal oxide to lithium-containing phosphate in the positive electrode active material on the energy density and cycle performance of the battery cell was investigated.

[0131] In the positive electrode active materials of Examples 9 to 12, the compositions of the nickel-containing lithium transition metal oxide and the lithium-containing phosphate are the same as those of Example 1. The nickel-containing lithium transition metal oxide is Li(Ni 0.9 Co 0.05 Mn 0.05 ) 2 , lithium phosphate containing Li(Fe 0.5 Mn 0.5 )PO 4, only the mass ratio of the nickel-containing lithium transition metal oxide to the lithium-containing phosphate is changed; in addition, the remaining settings of the positive electrode plate and the settings of the negative electrode plate, electrolyte, and isolation membrane are the same as those in Example 1.

[0132] The variable settings and battery cell performance test results of each embodiment are shown in Table 3.

[0133] Table 3 T / ％ Mass ratio of Ni and (Fe+Mn) Energy density / Wh / L Number of cycles Example 9 50 1.42 648.90 1700 Example 10 60 0.97 617.82 1717 Example 1 70 0.64 586.96 1743 Embodiment 11 80 0.37 556.26 1732 Example 12 90 0.16 527.70 1728

[0134] The data T in Table 3 represents the mass content of lithium phosphate in the positive electrode active material.

[0135] By comparing and analyzing the data of each embodiment in Table 3, it can be found that:

[0136] The mass content of lithium phosphate is 50% to 90%, and the battery cells all show good cycle performance; further, when the mass content of lithium phosphate is 50% to 70%, combined with a high-nickel lithium transition metal oxide system, the energy density is improved even more.

[0137] Based on Example 1, the following examples only adjust the molar content of Ni element in Ni, Co, and Mn elements in the nickel-containing lithium transition metal oxide, and other initial conditions remain unchanged. That is, the positive electrode active materials of each example meet the following requirements: the mass ratio of the nickel-containing lithium transition metal oxide to the lithium-containing phosphate is 3:7, and the lithium-containing phosphate is Li(Fe 0.5 Mn 0.5 )PO 4 , that is, the molar amount of Mn element in the lithium-containing phosphate accounts for 50% of the total molar amount of non-lithium transition metal elements. The negative electrode plate, electrolyte and isolation membrane are the same as those in Example 1.

[0138] The variable settings and battery cell performance test results of each embodiment are shown in Table 4.

[0139] Table 4

[0140] By comparing and analyzing the data of each embodiment in Table 4, it can be found that:

[0141] The composition of lithium-containing phosphate and its mass content in the positive electrode active material are controlled unchanged. In the nickel-containing lithium transition metal oxide, as the molar content of Ni element in Ni, Co, and Mn elements increases, the mass ratio of Ni:(Fe+Mn) also increases accordingly, making the energy density of the battery cell increase gradually, while the number of cycles decreases.

[0142] The amount and composition of the electrolyte are closely related to its ion transport capacity, chemical stability and other properties, which in turn affect the cycle life of the battery cell. Therefore, the role of the electrolyte on the cycle life of the battery cell is investigated by adjusting the electrolyte injection coefficient and different solvent ratios.

[0143] On the one hand, for the electrolytes of Examples 18 to 23, only the respective injection coefficients are set to different values, and the other conditions such as the composition of the electrolyte remain consistent with those of Example 1. The settings of the positive electrode sheet, negative electrode sheet, and isolation membrane of each embodiment are also the same as those of Example 1.

[0144] The variable settings and battery cell performance test results of each embodiment are shown in Table 5.

[0145] Table 5

[0146] From the data presented in Table 5, we can know that: the injection coefficient of the battery cell is too high or too low, which will affect the cycle life. If the injection coefficient is too high, it may easily cause electrolyte side reactions, which will reduce the cycle performance; if the injection coefficient is too low, it may easily lead to insufficient electrode wetting, which will also reduce the cycle performance. When the electrolyte injection coefficient is within the range of 1.8g / Ah-3.5g / Ah, especially within the range of 1.9g / Ah-3.1g / Ah, the cycle performance can be maintained at a high level.

[0147] On the other hand, for Examples 24 to 27, only the mass ratio of cyclic carbonate to linear carbonate in each electrolyte is adjusted, and the other conditions such as the injection coefficient remain consistent with Example 1. The settings of the positive electrode sheet, negative electrode sheet, and isolation membrane of each example are also the same as those in Example 1.

[0148] The variable settings and battery cell performance test results of each embodiment are shown in Table 6.

[0149] Table 6

[0150] From the data presented in Table 6, it can be learned that in the above embodiments, the mass ratio of different cyclic carbonates to linear carbonates mainly affects the cycle performance of the battery monomer. Based on Example 1, whether the mass content of the cyclic carbonate is reduced or increased, the number of cycles shows a downward trend. This may be because the cyclic carbonate is conducive to the dissociation of lithium ions, and the reduction of its mass content will affect the dissociation degree and conductivity of lithium ions. The cyclic carbonate itself has a large viscosity and weak oxidation resistance. The increase of its mass content may cause polarization loss of the battery monomer, thereby affecting the cycle performance.

[0151] In general, by combining nickel-containing lithium transition metal oxides and lithium-containing phosphates, and through the design of positive electrode active materials, it is possible to achieve simultaneous regulation of energy density and cycle life, so that the battery cells can obtain more balanced energy density and cycle life, and the energy density of the battery cells can be fully utilized. Compared with the case of using only high-nickel lithium transition metal oxides as positive electrode active materials, the safety risks are significantly reduced.

[0152] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, comprising a housing and an electrode assembly located inside the housing, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet, wherein: The negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active layer comprises a negative electrode active material, and the negative electrode active material comprises graphite. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer disposed on at least one side of the positive electrode current collector, the positive electrode active layer comprises a positive electrode active material, the positive electrode active material comprises a nickel-containing lithium transition metal oxide and a lithium-containing phosphate, and the molar amount of the Ni element in the nickel-containing lithium transition metal oxide accounts for 70% to 95% of the total molar amount of the transition metal in the nickel-containing lithium transition metal oxide; The lithium-containing phosphate includes Mn and Fe elements, and the ratio of the mass of the Ni element in the positive electrode active material to the sum of the mass of the Fe element and the Mn element in the positive electrode active material is between 0.15 and 2.

2. The battery cell according to claim 1, wherein: The ratio of the mass of the Ni element in the positive electrode active material to the sum of the mass of the Fe element and the Mn element in the positive electrode active material is between 0.55 and 1.

42.

3. The battery cell according to claim 1 or 2, wherein: The mass content of the lithium-containing phosphate in the positive electrode active material is 50%-90%, and can be optionally 50%-70%.

4. The battery cell according to any one of claims 1 to 3, wherein: The nickel-containing lithium transition metal oxide includes lithium-containing nickel-cobalt-manganese oxide, and the molar amount of the Ni element in the lithium-containing nickel-cobalt-manganese oxide accounts for 80%-95% of the total molar amount of the nickel-cobalt-manganese elements.

5. The battery cell according to any one of claims 1 to 4, wherein: The nickel-containing lithium transition metal oxide includes lithium-containing nickel-cobalt-manganese oxide, and the lithium-containing nickel-cobalt-manganese oxide contains one or more of Zr, Al, B, Fe, Ca, Sr, Ti, V or Y elements.

6. The battery cell according to claim 5, wherein: The lithium-containing nickel-cobalt-manganese oxide includes one or more of Zr, Al, B or Fe elements; optionally, in the lithium-containing nickel-cobalt-manganese oxide, the mass content of the elements satisfies at least one of the following: the content of Zr is 1000-3000 ppm, the content of Al is 100-1000 ppm, and the content of B is 50-300 ppm.

7. The battery cell according to any one of claims 1 to 6, wherein: The lithium-containing phosphate includes lithium manganese iron phosphate, and the molar amount of the Mn element in the lithium manganese iron phosphate accounts for 20%-80% of the total molar amount of transition metal elements, optionally 30%-70%, and further optionally 30%-50%.

8. The battery cell according to any one of claims 1 to 7, wherein: The lithium manganese iron phosphate contains one or more of Al, B, Ca, Cr, Cu, K, Mg, Na, P, Si, Ti, V or Zn elements. Optionally, the lithium manganese iron phosphate includes one or more of Al, Ca, Na, Ti or V elements; further optionally, in the lithium manganese iron phosphate, the mass content of the elements satisfies at least one of the following: Al content is 100-1000ppm, Ca content is 50-300ppm, Na content is 50-300ppm, Ti content is 100-1000ppm, and V content is 1000-3000ppm.

9. The battery cell according to any one of claims 1 to 8, wherein: The positive electrode active layer contains lithium manganese iron phosphate and lithium-containing nickel cobalt manganese oxide, and the positive electrode active material contains one or more of Al, B, Ca, Na, Sr, Ti, V, Y or Zr elements, and based on the total mass of the positive electrode active material, the mass content of each element satisfies: Al:0.005％-0.1％； Ca: 0.0001%-0.02%; Na: 0.005%-0.06%; Ti: 0.005%-0.15%; V:0.0001％-0.3％； Zr:0.005％-0.2％； B:0.01％-0.1％。 10. The battery cell according to any one of claims 1 to 9, wherein: The positive electrode active layer includes a first active layer and a second active layer, the first active layer is arranged close to the positive electrode current collector, and the second active layer is arranged on a side of the first active layer away from the positive electrode current collector. Based on the total mass of the positive electrode active layer, the mass content of the Ni element in the first active layer is less than the mass content of the Ni element in the second active layer, and the mass content of the Fe element in the first active layer is greater than the mass content of the Fe element in the second active layer.

11. The battery cell according to any one of claims 1 to 10, wherein: The battery monomer also includes a non-aqueous electrolyte, the non-aqueous electrolyte includes a solvent and a lithium salt, the solvent includes a cyclic carbonate and a linear carbonate; optionally, the cyclic carbonate includes ethylene carbonate; optionally, the linear carbonate includes one or more of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; optionally, the mass ratio of the cyclic carbonate to the linear carbonate is 2:8 to 5:

5.

12. The battery cell according to any one of claims 1 to 11, wherein: The electrolyte injection coefficient of the battery cell is 1.8g / Ah-3.5g / Ah, and can be optionally 1.9g / Ah-3.1g / Ah.

13. A battery device comprising the battery cell according to any one of claims 1 to 12, wherein the battery device comprises a battery module, a battery pack or an energy storage device.

14. An electrical device comprising the battery cell according to any one of claims 1 to 12, or the battery device according to claim 13.

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