Battery cell, battery and electric device

Abstract

A battery cell, a battery and an electric device. The battery cell comprises a positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector; the positive electrode film layer contains a lithium nickel cobalt manganese oxide; and the lithium nickel cobalt manganese oxide comprises single crystal particles, and comprises Ni and Al, Ni accounting for 50-70% of the total number of transition metal atoms in the lithium nickel cobalt manganese oxide, and the mass content of Al relative to the total mass of the lithium nickel cobalt manganese oxide being 0.2-1.0 wt%. The energy density of the battery cell can be improved, and the internal resistance of the battery cell can be reduced.

Description

Battery cells, batteries and electrical devices

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202410268438.1, filed on March 8, 2024, entitled “Battery Cell, Battery and Electrical Device,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to a battery cell, a battery and an electrical device. Background Art

[0004] Battery cells, with their high capacity and long lifespan, are widely used in electronic devices such as mobile phones, laptops, electric bicycles, electric cars, electric airplanes, electric boats, electric toy cars, electric toy boats, electric toy airplanes, and power tools. As the battery industry has made significant progress, higher performance requirements have been placed on battery cells.

[0005] However, the energy density of battery cells still needs to be further improved, and the internal resistance needs to be further reduced.

[0006] Summary of the Invention

[0007] The present application provides a battery cell, a battery, and an electrical device, which can improve the energy density of the battery cell and reduce the internal resistance of the battery cell.

[0008] In a first aspect, an embodiment of the present application proposes a battery cell, which includes a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, the positive electrode film layer contains lithium nickel cobalt manganese oxide, the lithium nickel cobalt manganese oxide includes single crystal particles, the lithium nickel cobalt manganese oxide includes Ni and Al elements, the Ni element accounts for 50% to 70% of the total number of transition metal atoms in the lithium nickel cobalt manganese oxide; the mass content of the Al element relative to the total mass of the lithium nickel cobalt manganese oxide is 0.2wt% to 1.0wt%.

[0009] Therefore, the lithium nickel cobalt manganese oxide in the embodiment of the present application mainly adopts single crystal particles. The single crystal particles have good power performance, can reduce the internal resistance of the battery cell, and can withstand higher voltages. However, in the related art, when preparing lithium nickel cobalt manganese oxide as a positive electrode film layer, the lithium nickel cobalt manganese oxide needs to be rolled, and the structural stability of the single crystal particles is poor. Under high-pressure rolling, the single crystal particles are easily crushed, making it difficult to prepare a positive electrode film layer with a high compaction density, and it is impossible to further improve the energy density of the battery cell. The embodiment of the present application can improve the capacity of the lithium nickel cobalt manganese oxide material itself and the structural stability under high pressure by regulating the elements in the lithium nickel cobalt manganese oxide, thereby improving the energy density of the battery cell.

[0010] In some embodiments, the mass content of Al element relative to the total mass of the lithium nickel cobalt manganese oxide is 0.4 wt % to 1.0 wt %. When the mass content of Al element is within the above range, the structural stability of the lithium nickel cobalt manganese oxide can be further improved.

[0011] In some embodiments, the single crystal particle includes an inner region and an outer region. The outer region is a region extending 500 nm from any point on the outer surface of the single crystal particle directly toward the interior of the single crystal particle. Al is distributed at least in the outer region. Optionally, the Al is distributed non-uniformly in the outer region. The distribution of Al at least in the outer region can improve the structural stability of the lithium nickel cobalt manganese oxide, enhance the pressure resistance of the lithium nickel cobalt manganese oxide, and help increase the compaction density of the positive electrode film layer, thereby increasing the energy density of the battery cell.

[0012] In some embodiments, the lithium nickel cobalt manganese oxide further comprises at least one element selected from the group consisting of Ti, Zr, Mg, V, P, S, and B, with the total mass content of these elements being between 2000 ppm and 3000 ppm. These elements can enhance the cycling stability of the lithium nickel cobalt manganese oxide at high voltages, reduce the risk of structural damage to the lithium nickel cobalt manganese oxide, and enhance the cycling performance of the battery cells.

[0013] In some embodiments, the battery cell further includes an electrolyte, the electrolyte includes lithium hexafluorophosphate, and the mass content of lithium hexafluorophosphate relative to the total mass of the electrolyte is 12 wt% to 18 wt%; optionally 12 wt% to 16 wt%.

[0014] In some embodiments, the electrolyte further comprises difluorophosphate, and the mass content of the difluorophosphate is 300 ppm to 3000 ppm based on the total mass of the electrolyte. When the mass content of difluorophosphate is within the above range, on the one hand, the difluorophosphate can "associate" with the Al element in the lithium nickel cobalt manganese oxide, which can reduce the dissolution of the Al element and improve the stability of the lithium nickel cobalt manganese oxide during the battery cell cycle process; on the other hand, the difluorophosphate can form a cathode electrolyte interphase (CEI) film on the surface of the positive electrode film layer, slowing down the interfacial side reactions between the positive electrode film layer and the electrolyte, and further reducing the internal resistance of the battery cell.

[0015] In some embodiments, the electrolyte further comprises tetrafluoroborate and fluorosulfonate. The mass content of tetrafluoroborate is 100 ppm to 1000 ppm, optionally 150 ppm to 600 ppm, based on the total mass of the electrolyte. The mass content of fluorosulfonate is 100 ppm to 1000 ppm, optionally 150 ppm to 600 ppm, based on the total mass of the electrolyte. The tetrafluoroborate and fluorosulfonate can modify the surface of the lithium nickel cobalt manganese oxide, making it more stable at high voltages and enabling the lithium nickel cobalt manganese oxide to maintain a stable output capacity at high voltages.

[0016] In some embodiments, the electrolyte further comprises an organic solvent, comprising ethyl methyl carbonate (EMC) and ethylene carbonate (EC). The ratio of the mass content of ethyl methyl carbonate (EMC) to the mass content of ethylene carbonate (EC) is 1:(0.4 to 0.6) based on the total mass of the electrolyte. Alternatively, the mass content of ethyl methyl carbonate (EMC) is 50 wt% to 70 wt% based on the total mass of the electrolyte. Alternatively, the mass content of ethylene carbonate (EC) is 20 wt% to 30 wt% based on the total mass of the electrolyte. When used in conjunction with a high-density positive electrode film, the above-mentioned organic solvent can help reduce the internal resistance of the battery cell.

[0017] In some embodiments, the electrolyte further includes lithium bis(fluorosulfonyl)imide (LiFSI), with the weight content of LiFSI being 2 wt% to 4 wt% relative to the total weight of the electrolyte. This weight content of LiFSI can improve the conductivity of the electrolyte and, when used in conjunction with a high-density cathode film, effectively reduce the internal resistance of the battery cell.

[0018] In some embodiments, the compaction density of a single-sided positive electrode film layer is 3.3 g / cm 3 Up to 3.6g / cm 3 When the compaction density of the single-sided positive electrode film layer is within the above range, the energy density of the battery cell can be effectively improved.

[0019] In some embodiments, the volume average particle size D of the single crystal particles is v 50 is 2.5 μm to 4.0 μm. The volume average particle size D of the single crystal particles v When 50 is within the above range, it is beneficial to further improve the compaction density, thereby improving the energy density.

[0020] In some embodiments, the battery cell further includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, and the negative electrode film layer includes at least one of artificial graphite and natural graphite.

[0021] In a second aspect, the present application further proposes a battery, which includes a battery cell according to any embodiment of the first aspect of the present application.

[0022] In a third aspect, the present application further proposes an electrical device comprising a battery according to any embodiment of the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. 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 creative work.

[0024] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0025] FIG. 2 is an exploded schematic diagram of an embodiment of the battery cell of FIG. 1 .

[0026] FIG3 is a schematic diagram of an embodiment of a battery module of the present application.

[0027] FIG4 is a schematic diagram of an embodiment of a battery pack of the present application.

[0028] FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .

[0029] FIG6 is a schematic diagram of an embodiment of an electric device including the battery cell of the present application as a power source.

[0030] The drawings are not necessarily drawn to scale.

[0031] The accompanying drawings are described as follows: 1. battery pack; 2. upper case; 3. lower case; 4. battery module; 5. battery cell; 51. housing; 52. electrode assembly; 53. cover plate; 6. electrical device. DETAILED DESCRIPTION

[0032] Below, the embodiments of the battery cell, battery, and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be 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.

[0033] " Range " disclosed in this application is limited in the form of lower limit and upper limit, and 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 special range. The scope limited in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that the range of 60 to 110 and 80 to 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, then the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 and 5" are listed herein, and "0 to 5" is merely an abbreviation for a combination of these values. Furthermore, when a parameter is expressed as an integer ≥ 2, this 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.

[0034] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0035] 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.

[0036] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which indicates 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.

[0037] A battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator. The separator is arranged between the positive electrode sheet and the negative electrode sheet to separate the positive electrode sheet and allow active ions to pass through. During the cyclic charge and discharge process of the battery cell, the positive electrode active material provides the battery cell with the lithium ions required for reciprocating intercalation and deintercalation between the positive and negative electrodes. Positive electrode active materials include lithium manganese oxide, lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, etc. Lithium nickel cobalt manganese oxide has a relatively high energy density and is widely used.

[0038] In the process of rolling lithium nickel cobalt manganese oxide as the positive electrode active material to form a positive electrode film layer, due to the poor structural stability of lithium nickel cobalt manganese oxide, lithium nickel cobalt manganese oxide is easily crushed, resulting in a relatively small compaction density of the positive electrode film layer, making it difficult to further improve the energy density of the battery cell.

[0039] In view of the above problems, the embodiments of the present application propose a battery cell, which includes a positive electrode plate, which contains lithium nickel cobalt manganese oxide, and the lithium nickel cobalt manganese oxide contains 0.2wt% to 1.0wt% aluminum (Al). The Al element can improve the structural stability of the lithium nickel cobalt manganese oxide and improve the material's pressure resistance, thereby increasing the compaction density of the plate and the energy density of the battery cell. The lithium nickel cobalt manganese oxide is mainly single crystal particles, which have good power performance and are conducive to reducing the internal resistance of the battery cell. The technical solution of this application is described in detail below.

[0040] battery cells

[0041] In a first aspect, an embodiment of the present application provides a battery cell.

[0042] The battery cell includes a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, the positive electrode film layer contains lithium nickel cobalt manganese oxide, the lithium nickel cobalt manganese includes single crystal particles, the lithium nickel cobalt manganese oxide includes nickel Ni and aluminum Al elements, the Ni element accounts for 50% to 70% of the total number of transition metal atoms in the lithium nickel cobalt manganese oxide; the mass content of the Al element relative to the total mass of the lithium nickel cobalt manganese oxide is 0.2wt% to 1.0wt%.

[0043] The lithium nickel cobalt manganese oxide in the embodiment of the present application mainly adopts single crystal particles. The single crystal particles have good power performance, can reduce the internal resistance of the battery cell, and can withstand higher voltages. However, in the related art, when preparing lithium nickel cobalt manganese oxide as a positive electrode film layer, the lithium nickel cobalt manganese oxide needs to be rolled, and the structural stability of the single crystal particles is poor. Under high-pressure rolling, the single crystal particles are easily crushed, making it difficult to prepare a positive electrode film layer with a high compaction density, and it is impossible to further improve the energy density of the battery cell. The embodiment of the present application can improve the capacity of the lithium nickel cobalt manganese oxide material itself and the structural stability under high pressure by regulating the elements in the lithium nickel cobalt manganese oxide, thereby improving the energy density of the battery cell.

[0044] The specific mechanism of the embodiment of the present application is speculated to be as follows:

[0045] The three elements of nickel, cobalt and manganese in lithium nickel cobalt manganese oxide have a synergistic effect and have different effects on the electrochemical properties of the material. Cobalt helps to improve the structural stability of lithium nickel cobalt manganese oxide and can alleviate the cation mixing phenomenon to a certain extent, improving the electronic conductivity and cycle performance of the material. Manganese helps to improve the structural stability and reliability of lithium nickel cobalt manganese oxide. Nickel exists in the form of nickel divalent cations, nickel trivalent cations, nickel tetravalent cations, etc. The redox couple potential of the nickel ions of different valences is low. At high voltages (for example, greater than or equal to 4.3V), relatively more lithium ions are released, which can store more electricity. As the number of nickel atoms increases, the capacity of lithium nickel cobalt manganese oxide can be improved, especially when the proportion of nickel elements relative to the total number of transition metal atoms in lithium nickel cobalt manganese oxide is 50% to 70%, the improvement of nickel elements on capacity is more significant. As the number of nickel atoms increases further, although nickel elements have a certain contribution to the capacity improvement, the capacity improvement is not significant, and the cation mixing phenomenon generated by nickel ions and lithium ions is more significant, resulting in reduced rate performance and cycle performance. For example, the proportion of nickel can be 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70% or a range consisting of any two of the above values.

[0046] Aluminum is further introduced into lithium nickel cobalt manganese oxide. When the mass content of aluminum is too low (less than 0.2wt%), the improvement of the structural stability of the lithium nickel cobalt manganese oxide by aluminum is limited, the pressure resistance of the material is still poor, and there is a risk of damage by external forces during the preparation of the pole piece. When the mass content of aluminum is too high (greater than 1.0wt%), aluminum may increase the transmission resistance of lithium ions in the lithium nickel cobalt manganese oxide, resulting in an increase in internal resistance. Therefore, in the embodiment of the present application, when the mass content of aluminum relative to the total mass of lithium nickel cobalt manganese oxide is set to 0.2wt% to 1.0wt%, the structure of the lithium nickel cobalt manganese oxide is relatively stable, which can improve the pressure resistance of the material, and then increase the compaction density of the pole piece, thereby improving the energy density of the battery cell. Optionally, when the mass content of aluminum relative to the total mass of lithium nickel cobalt manganese oxide is 0.4wt% to 1wt%, the structural stability of the lithium nickel cobalt manganese oxide can be further improved.

[0047] For example, the mass content of aluminum element relative to the total mass of lithium nickel cobalt manganese oxide can be 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, 0.5wt%, 0.55wt%, 0.6wt%, 0.65wt%, 0.7wt%, 0.75wt%, 0.8wt%, 0.85wt%, 0.9wt%, 0.95wt%, 1.0wt% or a range consisting of any two of the above values.

[0048] Aluminum can be located on the surface of the lithium nickel cobalt manganese oxide to act as a coating, improving its structural stability; or located within the crystal phase of the lithium nickel cobalt manganese oxide to stabilize its lattice structure; or it can be located both on the surface of the lithium nickel cobalt manganese oxide and within its crystal phase. If aluminum is detected during testing of the lithium nickel cobalt manganese oxide, it is considered that the lithium nickel cobalt manganese oxide contains aluminum.

[0049] In some embodiments, the single crystal particle includes an inner region and an outer region, the outer region is a region extending 500 nm straight from any point on the outer surface of the single crystal particle toward the interior of the single crystal particle; the Al element is distributed at least in the outer region.

[0050] The inner region of the single crystal particle can be understood as the core of the single crystal particle, and the outer region is covered outside the inner region; there may be no obvious boundary between the outer region and the inner region, and the outer region and the inner region can be considered as two artificially defined regions. The outer region is the region extending 500nm from any point on the outer surface of the single crystal particle toward the inside of the single crystal particle, and the extension path is a straight path. The outer region can be understood as a ring structure, and the radial spacing of the ring structure is less than or equal to 500nm.

[0051] The volume average particle size D of the single crystal particles vWhen 50≤500nm, it can be considered that the Al element is distributed on the surface and inside of the single crystal particles.

[0052] The Al element is distributed at least in the outer region, which can improve the structural stability of the lithium nickel cobalt manganese oxide, improve the pressure resistance of the lithium nickel cobalt manganese oxide, and help to improve the compaction density of the positive electrode film layer, thereby improving the energy density of the battery cell. Optionally, the Al element is unevenly distributed in the outer region, which can further improve the structural stability of the lithium nickel cobalt manganese oxide. Non-uniformity can be understood as the distribution of the Al element in the outer region having differences, for example, the content of one of the outer regions is relatively high, and the content of another of the outer regions is relatively low. Of course, in addition to being distributed in the outer region, the Al element can also be further distributed in the inner region.

[0053] In some embodiments, the lithium nickel cobalt manganese oxide further comprises at least one element selected from the group consisting of Ti, Zr, Mg, V, P, S, and B, with the total mass content of these elements being between 2000 ppm and 3000 ppm. These elements can enhance the cycling stability of the lithium nickel cobalt manganese oxide at high voltages, reduce the risk of structural damage to the lithium nickel cobalt manganese oxide, and enhance the cycling performance of the battery cells.

[0054] For example, the total mass content of Ti, Zr, Mg, V, P, S, and B elements may be 2000 ppm, 2100 ppm, 2200 ppm, 2300 ppm, 2400 ppm, 2500 ppm, 2600 ppm, 2700 ppm, 2800 ppm, 2900 ppm, 3000 ppm, or a range consisting of any two of the above values.

[0055] In the embodiment of the present application, the content of the elements in the positive electrode active material has a meaning well known in the art and can be detected by equipment and methods well known in the art, for example, with reference to EPA 6010D-2014, by inductively coupled plasma atomic emission spectrometry, using plasma atomic emission (ICP-OES, instrument model: Thermo ICAP7400) for determination. First, 0.4g of the positive electrode active material was weighed and 10ml (50% concentration) of aqua regia was added thereto. Then it was placed on a 180°C plate for 30min. After digestion on the plate, the volume was fixed to 100mL, and the standard curve method was used for quantitative testing.

[0056] In some embodiments, the volume average particle size D of the single crystal particles is v50 is 2.5 μm to 4.0 μm, for example, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4.0 μm, or a range consisting of any two of the above values. The volume average particle size D of the single crystal particles is 2.5 μm to 4.0 μm, for example, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4.0 μm, or a range consisting of any two of the above values. v When 50 is within the above range, it is beneficial to further improve the compaction density, thereby improving the energy density.

[0057] In the embodiment of the present application, the volume average particle size D of the particles v 50 is a well-known meaning in the art, and the volume average particle size D of the particles is v 50 refers to the particle size corresponding to 50% in the volume distribution, which can be tested using equipment and methods known in the art. For example, a newly prepared positive electrode active material is taken as a sample for testing, or a battery that has been fully discharged (discharged to the lower limit cut-off voltage so that the battery's state of charge is approximately 0% SOC) is reversely disassembled to remove the positive electrode sheet, and then the positive electrode film layer in the positive electrode sheet is scraped off from the positive electrode current collector as a test sample. After the test sample positive electrode active material is dried, the volume average particle size D of the particles is measured using a Mastersizer 2000E laser particle size analyzer in accordance with the test standard GB / T 19077-2016. v In the embodiment of the present application, a fresh battery cell may be a battery cell that has just been shipped from the factory (not subjected to charge and discharge cycles after formation), or a battery cell that is mounted on an electrical device and has been cycled less than 10 times.

[0058] In some embodiments, the compaction density of a single-sided positive electrode film layer is 3.3 g / cm 3 Up to 3.6g / cm 3 , for example, 3.30 g / cm 3 、3.35g / cm 3 、3.40g / cm 3 、3.45g / cm 3 、3.50g / cm 3 、3.55g / cm 3 、3.60g / cm 3 When the compaction density of the positive electrode film layer on one side is within the above range, the energy density of the battery cell can be effectively improved.

[0059] In the embodiment of the present application, the compaction density of the positive electrode film layer has a meaning well known in the art and can be tested using methods known in the art. For example, take a single-sided coated and cold-pressed positive electrode sheet (if it is a double-sided coated positive electrode sheet, the positive electrode film layer on one side can be wiped off first), punch it into small discs with an area of ​​S1, weigh it, and record it as M1. Then wipe off the positive electrode film layer of the weighed positive electrode sheet, weigh the weight of the positive electrode collector, and record it as M0. The surface density of the positive electrode film layer = (the weight of the positive electrode sheet M1-the weight of the positive electrode collector M0) / S1, and the compaction density of the positive electrode film layer = the surface density of the positive electrode film layer / the thickness of the positive electrode film layer.

[0060] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The present application embodiment does not particularly limit the type of positive electrode conductive agent. For example, the positive electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the positive electrode conductive agent is ≤5 wt % based on the total mass of the positive electrode film layer.

[0061] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. The embodiments of the present application do not particularly limit the type of positive electrode binder. As an example, the positive electrode binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and at least one of fluorine-containing acrylic resins. In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5wt%.

[0062] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector and comprising a positive electrode active material. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposing surfaces of the positive electrode current collector.

[0063] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0064] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP).

[0065] [Electrolyte]

[0066] In some embodiments, the battery cell further includes an electrolyte.

[0067] In some embodiments, the electrolyte includes lithium hexafluorophosphate (LiPF6), and the weight content of lithium hexafluorophosphate relative to the total weight of the electrolyte is 12 wt% to 18 wt%, or optionally 12 wt% to 16 wt%. For example, the weight content of lithium hexafluorophosphate relative to the total weight of the electrolyte can be 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, or a range consisting of any two of the foregoing values.

[0068] In some embodiments, the electrolyte further comprises difluorophosphate, and the mass content of difluorophosphate is 300 ppm to 3000 ppm based on the total mass of the electrolyte. For example, the mass content of difluorophosphate can be 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, 2100 ppm, 2200 ppm, 2300 ppm, 2400 ppm, 2500 ppm, 2600 ppm, 2700 ppm, 2800 ppm, 2900 ppm, 3000 ppm, or a range consisting of any two of the foregoing values.

[0069] When the mass content of difluorophosphate is within the above range, on the one hand, difluorophosphate can "associate" with the Al element in the lithium nickel cobalt manganese oxide, thereby reducing the dissolution of the Al element and improving the stability of the lithium nickel cobalt manganese oxide during the battery cell cycle process; on the other hand, difluorophosphate can form a cathode electrolyte interface (Cathode Electrolyte Interphase, CEI) film on the surface of the positive electrode film layer, slowing down the interfacial side reactions between the positive electrode film layer and the electrolyte, and further reducing the internal resistance of the battery cell.

[0070] In some embodiments, the electrolyte further includes at least one of tetrafluoroborate and fluorosulfonate. Optionally, the electrolyte further includes tetrafluoroborate and fluorosulfonate. Tetrafluoroborate and fluorosulfonate can modify the surface of the lithium nickel cobalt manganese oxide, making the lithium nickel cobalt manganese oxide more stable at high voltages, thereby enabling the lithium nickel cobalt manganese oxide to output a stable capacity at high voltages.

[0071] Optionally, based on the total mass of the electrolyte, the mass content of tetrafluoroborate is 100ppm to 1000ppm; optionally 150ppm to 600ppm. For example, the mass content of tetrafluoroborate can be 100ppm, 150ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, or a range consisting of any two of the above values. The above mass content of tetrafluoroborate can improve the surface modification effect of lithium nickel cobalt manganese oxide, making the lithium nickel cobalt manganese oxide more stable under high voltage, so that the lithium nickel cobalt manganese oxide can stably output capacity under high voltage.

[0072] Optionally, based on the total mass of the electrolyte, the mass content of fluorosulfonate is 100ppm to 1000ppm; optionally, 150ppm to 600ppm. For example, the mass content of fluorosulfonate can be 100ppm, 150ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, or a range consisting of any two of the above values. The above mass content of fluorosulfonate can improve the surface modification effect of lithium nickel cobalt manganese oxide, making the lithium nickel cobalt manganese oxide more stable under high voltage, so that the lithium nickel cobalt manganese oxide can stably output capacity under high voltage.

[0073] The cations corresponding to the tetrafluoroborate and fluorosulfonate mentioned above may be lithium ions, sodium ions, etc., and lithium ions may be selected.

[0074] In some embodiments, the electrolyte further comprises an organic solvent, and the organic solvent comprises ethyl methyl carbonate (EMC) and ethylene carbonate (EC); based on the total mass of the electrolyte, the mass content ratio of ethyl methyl carbonate (EMC) to ethylene carbonate (EC) is 1:(0.4 to 0.6). The organic solvent comprises ethyl methyl carbonate (EMC) and ethylene carbonate (EC), and the addition amount of ethyl methyl carbonate (EMC) is relatively high, while the addition amount of ethylene carbonate (EC) is relatively low, and the viscosity of the electrolyte is low; the organic solvent and the high compacted density (e.g., 3.3 g / cm 3 Up to 3.6g / cm 3 ) is used in combination with the positive electrode film layer, which is beneficial to reducing the internal resistance of the battery cell.

[0075] Illustratively, the ratio of the mass content of ethyl methyl carbonate EMC to the mass content of ethylene carbonate EC can be 1:0.40, 1:0.41, 1:0.42, 1:0.43, 1:0.44, 1:0.45, 1:0.46, 1:0.47, 1:0.48, 1:0.49, 1:0.50, 1:0.51, 1:0.52, 1:0.53, 1:0.54, 1:0.55, 1:0.56, 1:0.57, 1:0.58, 1:0.59, 1:0.60 or a range consisting of any two of the above values.

[0076] Exemplarily, based on the total mass of the electrolyte, the mass content of ethyl methyl carbonate EMC is 50wt% to 70wt%; for example, 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, 55wt%, 56wt%, 57wt%, 58wt%, 59wt%, 60wt%, 61wt%, 62wt%, 63wt%, 64wt%, 65wt%, 66wt%, 67wt%, 68wt%, 69wt%, 70wt% or a range consisting of any two of the above values.

[0077] Exemplarily, based on the total mass of the electrolyte, the mass content of ethylene carbonate EC is 20 wt% to 30 wt%, for example, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt% or a range consisting of any two of the above values.

[0078] In some embodiments, the electrolyte further comprises lithium bis(fluorosulfonyl)imide (LiFSI), and the mass content of lithium bis(fluorosulfonyl)imide (LiFSI) relative to the total mass of the electrolyte is 2 wt % to 4 wt %. The above mass content of lithium bis(fluorosulfonyl)imide (LiFSI) can improve the conductivity of the electrolyte and the high compaction density (3.3 g / cm 3 Up to 3.6g / cm 3 ) when used in combination with a positive electrode film layer, it can effectively reduce the internal resistance of the battery cell.

[0079] Illustratively, based on the total mass of the electrolyte, the mass content of lithium bis(fluorosulfonyl)imide LiFSI can be 2.0 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt%, 3.0 wt%, 3.1 wt%, 3.2 wt%, 3.3 wt%, 3.4 wt%, 3.5 wt%, 3.6 wt%, 3.7 wt%, 3.8 wt%, 3.9 wt%, 4.0 wt% or a range consisting of any two of the above values.

[0080] The qualitative and quantitative properties of each substance or element in this application can be detected using appropriate equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and international detection standards, domestic and international enterprise standards, etc., and those skilled in the art can also adapt certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. A single detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0081] In the embodiments of the present application, the types and contents of the inorganic components / lithium salt concentrations in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, the inorganic components / lithium salt concentrations in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis method with reference to standard JY / T020-1996 "General Rules for Ion Chromatography Analysis Methods". In the embodiments of the present application, a freshly prepared electrolyte can be taken as a sample, or a battery that has been fully discharged (discharged to the lower limit cut-off voltage so that the battery's state of charge is approximately 0% SOC) can be reversely disassembled, and the free electrolyte obtained from the battery can be used as a sample for detection using an ion chromatography analysis method.

[0082] In the embodiments of the present application, the types and contents of the organic components in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, reference can be made to GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" for qualitative and quantitative analysis of the organic components in the electrolyte by gas chromatography. In the embodiments of the present application, a freshly prepared electrolyte can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the battery's state of charge is approximately 0%) can be reversely disassembled, and the free electrolyte obtained from the battery can be used as a sample for detection using an ion chromatography analysis method.

[0083] For example, using liquid-phase nuclear magnetic resonance (NMR) chromatography to test the composition of an electrolyte additive, for example, lithium difluorophosphate and lithium hexafluorophosphate, a 7ml glass bottle is prepared in a nitrogen glove box. 5ml of a premixed NMR reagent solution is added to the bottle and allowed to stand in the nitrogen glove box at room temperature (20-25°C) for 24 hours to allow the electrolyte in the electrode and separator to diffuse into the premixed NMR solution, thus obtaining the NMR test sample. The premixed NMR solution consists of 100ml of deuterated acetonitrile and 3ml of trifluoromethylbenzene (C7H5F3). This premixed NMR reagent solution is pre-dried with 4A molecular sieves (15g of freshly opened 4A molecular sieves per 100ml of premixed NMR reagent solution is dried at room temperature (20-25°C) in a nitrogen glove box for over 30 days). 19F NMR measurements are performed using a Bruker Avance 400HD NMR instrument.

[0084] To identify and quantify individual species, the following settings were used with respect to flip angle and scanning time.

[0085] Fluorine spectrum test pulse sequence: 2gfhigqn.2;

[0086] Delay time: 1 second;

[0087] Scan times: 16 times;

[0088] The relative contents of trifluoromethylbenzene and LiPF6 were calculated based on the integrated intensity of the signal peaks of the two substances in F-NMR. The calculation method is:

[0089] LiPF6 relative content = (I LiPF6 ×M LiPF6 / 6) / (I CF3ph ×M CF3ph / 3), where I is the corresponding NMR peak area and M is the corresponding relative molecular mass.

[0090] The content of the electrolyte in the deuterated reagent is calculated based on the content of lithium hexafluorophosphate LiPF6.

[0091] Based on the F-NMR of trifluoromethylbenzene and PO2F2 - The relative content of the two substances is calculated based on the integrated intensity of the signal peaks. The calculation method is:

[0092] PO2F2 - Relative content = (I PO2F2- ×M PO2F2- / 2) / (I CF3ph ×M CF3ph / 3), where I is the corresponding NMR peak area and M is the corresponding relative molecular mass.

[0093] In some embodiments, the various solutes or solvents in the electrolyte mentioned in this application include substances actively added when preparing the electrolyte, and also include substances derived from certain substances already existing in the electrolyte during the preparation of the electrolyte or in the process of preparing a battery from the electrolyte, or during the storage or use of a battery containing the electrolyte.

[0094] [Negative electrode]

[0095] In some embodiments, the battery cell further includes a negative electrode plate.

[0096] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and comprising a negative electrode active material. For example, the negative electrode current collector may have two opposing surfaces in its thickness direction, and the negative electrode film layer may be disposed on either or both of the two opposing surfaces of the negative electrode current collector.

[0097] The negative electrode active material can be any negative electrode active material known in the art for use in battery cells. For example, the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include at least one of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include at least one of elemental tin, tin oxide, and tin alloys.

[0098] In some embodiments, the negative electrode film layer may include at least one of artificial graphite and natural graphite, and artificial graphite may be selected because artificial graphite has relatively high structural stability.

[0099] The graphite material in the embodiment of the present application can be subjected to X-ray powder diffraction testing and qualitative analysis on the negative electrode sheet or negative electrode active material in combination with JIS / K0131-1996 General Rules for X-ray Diffraction Analysis.

[0100] In some embodiments, the weight content of the artificial graphite is greater than or equal to 85 wt % and less than 100 wt % based on the total weight of the negative electrode film layer. For example, the weight content of the artificial graphite can be 85 wt %, 86 wt %, 87 wt %, 88 wt %, 89 wt %, 90 wt %, 91 wt %, 92 wt %, 93 wt %, 94 wt %, 95 wt %, 96 wt %, 97 wt %, 98 wt %, 99 wt %, or a range consisting of any two of the foregoing values.

[0101] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present embodiments do not particularly limit the type of negative electrode conductive agent. For example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the negative electrode conductive agent is ≤5 wt % based on the total mass of the negative electrode film layer.

[0102] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. The embodiments of the present application do not particularly limit the type of the negative electrode binder. As an example, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin (SR-1B), aqueous acrylic resin (e.g., polyacrylic acid (PAA), polymethacrylic acid (PMAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS)). In some embodiments, the mass content of the negative electrode binder is ≤5 wt % based on the total mass of the negative electrode film layer.

[0103] In some embodiments, the negative electrode film layer may optionally include other additives. For example, these additives may include thickeners, such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor materials, and the like. In some embodiments, the weight content of these additives is ≤ 2 wt % based on the total weight of the negative electrode film layer.

[0104] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. Copper foil may be used as an example of a metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal material may include at least one of copper, a copper alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. For example, the polymer base layer may include at least one of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, and polyethylene.

[0105] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0106] The negative electrode sheet does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the embodiments of the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0107] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly through a winding process and / or a lamination process.

[0108] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0109] In some embodiments, the outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell can also be a soft shell, such as a bag-type soft shell. The soft shell can be made of plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0110] The present invention has no particular restrictions on the shape of the battery cell, which can be cylindrical, square, or any other shape. FIG1 shows a battery cell 5 with a square structure as an example.

[0111] In some embodiments, as shown in FIG2 , the outer packaging may include a shell 51 and a cover plate 53. 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 cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the separator may be formed into an electrode assembly 52 through a winding process and / or a lamination process. The electrode assembly 52 is encapsulated 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 may be one or more, which can be adjusted according to demand.

[0112] The preparation methods of the battery cells of the embodiments of the present application are well known. In some embodiments, a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, separator, and negative electrode sheet can be wound and / or laminated to form an electrode assembly. The electrode assembly is then placed in an outer packaging, dried, and then injected with electrolyte. The battery cell is then vacuum packaged, allowed to stand, formed, and shaped to obtain a battery cell.

[0113] In some embodiments of the present application, the battery cells according to the present application can be assembled into a battery module. The battery module can contain multiple battery cells, and the specific number can be adjusted according to the application and capacity of the battery module.

[0114] Figure 3 is a schematic diagram of an exemplary battery module 4. As shown in Figure 3 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0115] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0116] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0117] Figures 4 and 5 are schematic diagrams of an exemplary battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 covers the lower case 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0118] Electrical devices

[0119] A second aspect of the embodiments of the present application provides an electrical device, which includes at least one of the battery cells, battery modules, or battery packs of the embodiments of the present application. The battery cells, battery modules, or battery packs can be used as power sources for the electrical device, or as energy storage units for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop 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, a satellite, an energy storage system, etc.

[0120] The electrical device can select battery cells, battery modules or battery packs according to its usage requirements.

[0121] FIG6 is a schematic diagram of an exemplary electric device 6. The electric device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electric device 6, a battery pack or battery module may be used.

[0122] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0123] Example

[0124] The following examples describe the disclosure of the present invention in more detail. These examples are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present invention will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0125] Example 1

[0126] 1. Preparation of positive electrode sheet

[0127] The positive electrode sheet includes a positive electrode current collector aluminum foil and a positive electrode film layer. The positive electrode film layer includes a positive electrode slurry (the solvent is N-methylpyrrolidone NMP) uniformly coated on the surface of the positive electrode current collector aluminum foil, and a film layer formed after drying and cold pressing. The positive electrode film layer includes a positive electrode active material, a conductive agent carbon black, and a binder polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:1.4:1.1.

[0128] The positive electrode active material includes lithium nickel cobalt manganese oxide single crystal particles, and the lithium nickel cobalt manganese oxide also includes aluminum Al and nickel Ni.

[0129] 2. Preparation of negative electrode sheet

[0130] The negative electrode sheet includes a negative electrode current collector copper foil and a negative electrode film layer. The negative electrode film layer includes a negative electrode slurry (the solvent is deionized water) uniformly coated on the surface of the negative electrode current collector copper foil, and a film layer formed after drying and cold pressing. The negative electrode film layer includes a negative electrode active material, a binder styrene-butadiene rubber (SBR), a thickener sodium carboxymethyl cellulose (CMC-Na), and a conductive agent carbon black (Super P) in a weight ratio of 96.2:1.8:1.2:0.8.

[0131] The negative electrode active material includes artificial graphite.

[0132] 3. Isolation film

[0133] The isolation membrane is a porous polypropylene membrane.

[0134] 4. Preparation of electrolyte

[0135] The electrolyte includes an organic solvent, lithium salt and additives.

[0136] 5. Preparation of batteries

[0137] The lithium-ion battery includes an outer packaging shell, an electrode assembly and an electrolyte. The electrode assembly and the electrolyte are arranged in the outer packaging shell. The electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator. The electrode assembly is a wound electrode assembly, and the separator is arranged between the positive electrode sheet and the negative electrode sheet.

[0138] Comparative Example 1 and Comparative Example 2

[0139] A lithium-ion battery was prepared using a method similar to that of Example 1, except that at least the mass content of the Al element was adjusted.

[0140] Example 2-1 to Example 2-4

[0141] A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 1 was that the mass content of the Al element in the positive electrode active material was adjusted.

[0142] Example 3

[0143] A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 1 was that the positive electrode active material further included Zr element.

[0144] Example 4-1 and Example 4-2

[0145] A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 1 was that the volume average particle size of the single crystal particles of the positive electrode active material was adjusted.

[0146] Example 5-1 and Example 5-2

[0147] A lithium-ion battery was prepared using a method similar to that of Example 1. The difference from Example 1 was that the atomic ratio of Ni element in the positive electrode active material was adjusted.

[0148] Performance Testing

[0149] 1. Energy density of battery cells

[0150] In the embodiments of the present application, the term "energy density" refers to the volume (usually expressed in Wh / L) or weight (usually expressed in Wh / kg) of energy transferred during each cycle of charge / discharge. The present application uses weight energy density to characterize the energy density of a battery cell. For example, the battery cells prepared in the examples and comparative examples are charged with a 1C constant current to 4.35V, then charged with a constant voltage to 0.05C, left to stand for 30 minutes, and discharged at 1C to 2.8V. The discharge capacity D0 is recorded, the battery is weighed, and the total mass m0 of the battery cell is recorded. The energy density of the battery cell is D0 / m0 (capacity per unit mass).

[0151] 2. Internal resistance of battery cells

[0152] At 25°C, the state of charge (SOC) of the battery cells prepared in the embodiment and the comparative example were respectively adjusted to 20% of the full charge capacity, and discharged at a rate of 0.3C for 10s. The voltage before discharge was recorded as U1, and the voltage after discharge was recorded as U2. The initial DC internal resistance of the battery cell DCR0 = (U1-U2) / I.

[0153] Test results

[0154] The test results are shown in Table 1.

[0155] Table 1

[0156] In Table 1,

[0157] The energy density of comparative example 1 is 230Wh / Kg. The relative value of the energy density of the embodiment in Table 1 is the percentage of the energy density of the embodiment to the energy density of comparative example 1, that is, the value calculated with the energy density of comparative example 1 as 100%.

[0158] The relative values ​​of energy densities of other comparative examples are the percentages of the energy densities of other comparative examples to the energy density of comparative example 1, that is, the values ​​calculated with the energy density of comparative example 1 being 100%.

[0159] The internal resistance of Comparative Example 1 is 29.5 mΩ. The relative internal resistance value of the embodiment in Table 1 is the percentage of the internal resistance of the embodiment to the internal resistance of Comparative Example 1, that is, the value calculated with the internal resistance of Comparative Example 1 as 100%.

[0160] The relative values ​​of the internal resistances of the other comparative examples are the percentages of the internal resistances of the other comparative examples to the internal resistance of comparative example 1, that is, the values ​​calculated with the internal resistance of comparative example 1 being 100%.

[0161] In Comparative Example 1, the aluminum content (Al) is too low, failing to effectively improve the structural stability of the lithium nickel cobalt manganese oxide. This makes it easily crushed during electrode preparation, resulting in a relatively low compaction density and energy density of the positive electrode film. In Comparative Example 2, the aluminum content (Al) is too high. While this effectively improves the structural stability of the lithium nickel cobalt manganese oxide and contributes to an increase in energy density, the excessive Al content may increase resistance to lithium ion migration and thus internal resistance.

[0162] The embodiment of the present application can effectively improve the structural stability of lithium nickel cobalt manganese oxide by controlling the mass content of aluminum element to 0.2wt% to 1.0wt%, especially when it meets 0.4wt% to 0.7wt%, which is beneficial to improving energy density; and the lithium ion transmission performance is better, and the power performance in single crystal particles is better, which is beneficial to reducing the internal resistance of the battery cell.

[0163] In Example 3, by introducing the Zr element into the positive electrode active material, the stability of the crystal structure can be effectively improved, which is beneficial to improving the cycle performance, enhancing the power performance, and reducing the internal resistance.

[0164] Example 4-1 and Example 4-2 were tested by measuring the volume average particle size D of the single crystal particles. v 50 can further improve the power performance and reduce the internal resistance of the battery cell.

[0165] By adjusting the proportion of Ni in Example 5-1 and Example 5-2, the power performance can be further improved and the internal resistance of the battery cell can be reduced.

[0166] Example 6-1 to Example 6-4

[0167] A lithium-ion battery was prepared using a method similar to that of Example 1, except that the mass content of difluorophosphate was adjusted.

[0168] Example 7-1 to Example 7-7

[0169] A lithium-ion battery was prepared using a method similar to that of Example 1, except that the mass content of at least one of tetrafluoroborate and sulfonate was adjusted.

[0170] Example 8-1 and Example 8-2

[0171] A lithium ion battery was prepared using a method similar to that of Example 1, except that the content and type of the organic solvent were adjusted.

[0172] Example 9-1 and Example 9-2

[0173] A lithium-ion battery was prepared using a method similar to that of Example 1, except that the content of lithium bis(fluorosulfonyl)imide (LiFSI) was adjusted.

[0174] Table 2

[0175] Example 1, Example 6-1 to Example 9-2 also include 15 wt% lithium hexafluorophosphate LiPF6 relative to the total mass of the electrolyte.

[0176] The electrolyte compositions of the comparative examples and examples (not shown) were the same as those of Example 1.

[0177] In Example 1 and Example 6-1 to Example 6-4, the content of difluorophosphate was adjusted. Difluorophosphate can reduce the dissolution of the Al element and improve the stability of lithium nickel cobalt manganese oxide during the battery cell cycle process; difluorophosphate can also form a CEI film on the surface of the positive electrode film layer, slowing down the interfacial side reactions between the positive electrode film layer and the electrolyte, and further reducing the internal resistance of the battery cell.

[0178] In Example 7-1 and Example 7-7, the content of at least one of tetrafluoroborate and fluorosulfonate is adjusted, which can improve the cycle stability of lithium nickel cobalt manganese oxide and reduce the internal resistance of the battery cell.

[0179] In Example 8-1 and Example 8-2, the internal resistance of the battery cell can be effectively improved by regulating the mass content ratio of ethyl methyl carbonate EMC and ethylene carbonate EC.

[0180] In Example 9-1 and Example 9-2, the internal resistance of the battery cell can be effectively improved by regulating the mass content of lithium bis(fluorosulfonyl)imide LiFSI.

[0181] Although illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions, and modifications may be made to the embodiments without departing from the spirit, principles, and scope of the present application.

Claims

1. A battery cell comprising a positive electrode plate, the positive electrode plate comprising a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer comprising lithium nickel cobalt manganese oxide, the lithium nickel cobalt manganese oxide comprising single crystal particles, and the lithium nickel cobalt manganese oxide comprising: Ni element, which accounts for 50% to 70% of the total number of transition metal atoms in the lithium nickel cobalt manganese oxide; as well as The Al element has a mass content of 0.2 wt% to 1.0 wt% relative to the total mass of the lithium nickel cobalt manganese oxide.

2. The battery cell according to claim 1, wherein: The mass content of Al element relative to the total mass of the lithium nickel cobalt manganese oxide is 0.4 wt % to 1.0 wt %.

3. The battery cell according to claim 1 or 2, wherein: The single crystal particle includes an inner region and an outer region. The outer region is a region extending 500 nm straight from any point on the outer surface of the single crystal particle toward the interior of the single crystal particle. Al element is distributed at least in the outer region.

4. The battery cell according to claim 3, wherein: The Al element is non-uniformly distributed in the outer region.

5. The battery cell according to any one of claims 1 to 4, wherein: The lithium nickel cobalt manganese oxide further includes at least one element selected from the group consisting of Ti, Zr, Mg, V, P, S, and B; The total mass content of the Ti, Zr, Mg, V, P, S and B elements is 2000 ppm to 3000 ppm.

6. The battery cell according to any one of claims 1 to 5, wherein: The battery cell further includes an electrolyte, the electrolyte includes lithium hexafluorophosphate, and the mass content of the lithium hexafluorophosphate relative to the total mass of the electrolyte is 12 wt % to 18 wt %.

7. The battery cell according to claim 6, wherein: The mass content of the lithium hexafluorophosphate relative to the total mass of the electrolyte is 12 wt % to 16 wt %.

8. The battery cell according to claim 6 or 7, wherein: The electrolyte also includes difluorophosphate, The mass content of the difluorophosphate is 300 ppm to 3000 ppm based on the total mass of the electrolyte.

9. The battery cell according to any one of claims 6 to 8, wherein: The electrolyte also includes tetrafluoroborate and fluorosulfonate, The mass content of the tetrafluoroborate is 100 ppm to 1000 ppm based on the total mass of the electrolyte; and / or Based on the total mass of the electrolyte, the mass content of the fluorosulfonate ion is 100 ppm to 1000 ppm.

10. The battery cell according to claim 9, wherein: The mass content of the tetrafluoroborate is 150 ppm to 600 ppm.

11. The battery cell according to claim 9 or 10, wherein: The mass content of the fluorosulfonate ion is 150 ppm to 600 ppm.

12. The battery cell according to any one of claims 6 to 11, wherein: The electrolyte further includes an organic solvent, and the organic solvent includes ethyl methyl carbonate EMC and ethylene carbonate EC; Based on the total mass of the electrolyte, the ratio of the mass content of the ethyl methyl carbonate EMC to the mass content of the ethylene carbonate EC is 1:(0.4 to 0.6).

13. The battery cell according to claim 12, wherein: Based on the total mass of the electrolyte, the mass content of the ethyl methyl carbonate EMC is 50wt% to 70wt%; or Based on the total mass of the electrolyte, the mass content of the ethylene carbonate EC is 20 wt % to 30 wt %.

14. The battery cell according to any one of claims 6 to 13, wherein: The electrolyte further includes lithium bis(fluorosulfonyl)imide (LiFSI), and the mass content of lithium bis(fluorosulfonyl)imide (LiFSI) relative to the total mass of the electrolyte is 2 wt % to 4 wt %.

15. The battery cell according to claim 14, wherein: The compaction density of the positive electrode film layer on one side is 3.3g / cm 3 Up to 3.6g / cm 3 .

16. The battery cell according to any one of claims 1 to 15, wherein: The volume average particle size D of the single crystal particles v 50 is 2.5μm to 4.0μm.

17. The battery cell according to any one of claims 1 to 16, further comprising a negative electrode plate, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode film layer comprises at least one of artificial graphite and natural graphite.

18. A battery comprising the battery cell according to any one of claims 1 to 17.

19. An electrical device comprising the battery according to claim 18.

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