Battery cell, battery, and electric device

Abstract

The application relates to a battery monomer, a battery and a power utilization device. The battery monomer comprises a positive pole sheet, the positive pole sheet comprises a positive pole current collector and a positive pole film layer arranged on at least one side of the positive pole current collector, the positive pole film layer contains lithium nickel cobalt manganese oxide, the lithium nickel cobalt manganese oxide comprises single-crystal particles, the lithium nickel cobalt manganese oxide comprises Ni elements and Al elements, the proportion of the Ni elements in the total number of transition metal atoms in the lithium nickel cobalt manganese oxide is 50% to 70%, and the mass content of the Al elements in the total mass of the lithium nickel cobalt manganese oxide is 0.2wt% to 1.0wt%. The application can improve the energy density of the battery monomer and reduce the internal resistance of the battery monomer.

Description

[0001] This application is a divisional application based on the invention with application number 202410268438.1, application date March 8, 2024, applicant CATL, and invention title "Battery Cell, Battery and Electrical Device". Technical Field

[0002] This application relates to a battery cell, a battery, and an electrical device. Background Technology

[0003] Battery cells possess characteristics such as high capacity and long lifespan, making them widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools. Due to significant advancements in the battery field, even higher performance requirements have been placed on battery cells.

[0004] However, the energy density of individual battery cells still needs to be further improved, and the internal resistance needs to be further reduced. Summary of the Invention

[0005] This application provides a battery cell, a battery, and an electrical device that can improve the energy density of the battery cell and reduce the internal resistance of the battery cell.

[0006] In a first aspect, embodiments of this application propose a battery cell, the battery cell comprising a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer containing lithium nickel cobalt manganese oxide, the lithium nickel cobalt manganese oxide comprising single crystal particles, the lithium nickel cobalt manganese oxide comprising Ni element and Al element, the proportion of Ni element relative to the total number of transition metal atoms in the lithium nickel cobalt manganese oxide being 50% to 70%; the mass content of Al element relative to the total mass of the lithium nickel cobalt manganese oxide being 0.2 wt% to 1.0 wt%.

[0007] Therefore, the lithium nickel cobalt manganese oxide in this embodiment mainly uses single-crystal particles. Single-crystal particles have better power performance, can reduce the internal resistance of the battery cell, and can withstand higher voltages. However, in related technologies, when preparing lithium nickel cobalt manganese oxide as a positive electrode film, it is necessary to roll-press the lithium nickel cobalt manganese oxide. However, the structural stability of single-crystal particles is poor. Under high-pressure rolling, single-crystal particles are easily crushed, making it difficult to prepare a high-density positive electrode film and thus failing to further improve the energy density of the battery cell. In contrast, the embodiment of this application, by controlling the elements in the lithium nickel cobalt manganese oxide, can improve the capacity of the lithium nickel cobalt manganese oxide material itself and its structural stability under high pressure, thereby improving the energy density of the battery cell.

[0008] In some embodiments, the Al content relative to the total mass of lithium nickel cobalt manganese oxide is 0.4 wt% to 1.0 wt%. When the Al content is within the above range, the structural stability of the lithium nickel cobalt manganese oxide can be further improved.

[0009] In some embodiments, the single-crystal particle includes an inner region and an outer region. The outer region is a region extending 500 nm directly from any point on the outer surface of the single-crystal particle towards its interior. Al element is at least distributed in the outer region. Optionally, Al element is non-uniformly distributed in the outer region. The presence of Al element at least in the outer region can improve the structural stability of lithium nickel cobalt manganese oxide, enhance its withstand voltage, and help increase the compaction density of the cathode film, thereby improving the energy density of the battery cell.

[0010] In some embodiments, the lithium nickel cobalt manganese oxide further includes at least one element selected from Ti, Zr, Mg, V, P, S, and B; the total mass content of Ti, Zr, Mg, V, P, S, and B is 2000 ppm to 3000 ppm. These elements can improve the cycle 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 improve the cycle performance of the battery cell.

[0011] In some embodiments, the battery cell further includes an electrolyte comprising lithium hexafluorophosphate, wherein the mass content of lithium hexafluorophosphate relative to the total mass of the electrolyte is 12 wt% to 18 wt%; optionally, it is 12 wt% to 16 wt%.

[0012] In some embodiments, the electrolyte further includes difluorophosphate, with a difluorophosphate content of 300 ppm to 3000 ppm based on the total mass of the electrolyte. When the difluorophosphate content is within this range, on the one hand, difluorophosphate can associate with Al in lithium nickel cobalt manganese oxide, reducing Al dissolution and improving the stability of lithium nickel cobalt manganese oxide during battery cell cycling; on the other hand, difluorophosphate can form a cathode electrolyte interphase (CEI) film on the surface of the cathode film, mitigating interfacial side reactions between the cathode film and the electrolyte, further reducing the internal resistance of the battery cell.

[0013] In some embodiments, the electrolyte further includes tetrafluoroborate and fluorosulfonate. The mass content of tetrafluoroborate is from 100 ppm to 1000 ppm, optionally from 150 ppm to 600 ppm, based on the total mass of the electrolyte. The mass content of fluorosulfonate is from 100 ppm to 1000 ppm, optionally from 150 ppm to 600 ppm, based on the total mass of the electrolyte. Tetrafluoroborate and fluorosulfonate can modify the surface of lithium nickel cobalt manganese oxide, making the lithium nickel cobalt manganese oxide more stable under high voltage, thus enabling stable output capacity under high voltage.

[0014] In some embodiments, the electrolyte further includes an organic solvent, comprising ethyl methyl carbonate (EMC) and ethylene carbonate (EC); the mass ratio of EMC to EC is 1:(0.4 to 0.6) based on the total mass of the electrolyte; optionally, the mass content of EMC is 50 wt% to 70 wt% based on the total mass of the electrolyte; optionally, the mass content of EC is 20 wt% to 30 wt% based on the total mass of the electrolyte. When the above-mentioned organic solvent is used in conjunction with a high-density positive electrode film, it is beneficial to reduce the internal resistance of the battery cell.

[0015] In some embodiments, the electrolyte further includes lithium bis(fluorosulfonyl)imide (LiFSI), wherein the mass content of LiFSI relative to the total mass of the electrolyte is 2 wt% to 4 wt%. The aforementioned mass content of LiFSI can improve the conductivity of the electrolyte, and when used in conjunction with a high-density positive electrode film, it can effectively reduce the internal resistance of the battery cell.

[0016] In some embodiments, the compaction density of the single-sided positive electrode film is 3.3 g / cm³. 3 Up to 3.6 g / cm 3 When the compaction density of the single-sided positive electrode film is within the above range, the energy density of the battery cell can be effectively improved.

[0017] In some embodiments, the volume average particle size D of the single crystal particles v 50 ranges from 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 increase the compaction density, thereby increasing the energy density.

[0018] In some embodiments, the battery cell further includes a negative electrode sheet, which includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, the negative electrode film layer including at least one of artificial graphite and natural graphite.

[0019] Secondly, this application also proposes a battery comprising a battery cell as described in any embodiment of the first aspect of this application.

[0020] Thirdly, this application also proposes an electrical device including a battery as described in any embodiment of the second aspect of this application. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of one embodiment of the battery cell of this application.

[0023] Figure 2 yes Figure 1 An exploded view of the implementation method of the battery cell.

[0024] Figure 3 This is a schematic diagram of one embodiment of the battery module of this application.

[0025] Figure 4 This is a schematic diagram of one embodiment of the battery pack of this application.

[0026] Figure 5 yes Figure 4 An exploded view of an embodiment of the battery pack shown.

[0027] Figure 6 This is a schematic diagram of one embodiment of an electrical device that uses the battery cell of this application as a power source.

[0028] The accompanying drawings may not be drawn to scale.

[0029] The annotations in the attached figures are explained as follows:

[0030] 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery module;

[0031] 5. Battery cell; 51. Housing; 52. Electrode assembly;

[0032] 53. Cover plate;

[0033] 6. Electrical appliances. Detailed Implementation

[0034] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0035] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, it is also expected that ranges of 60 to 110 and 80 to 120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all 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 stated, the numerical range "a to b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 and 5" have been listed in this article; "0 to 5" is just a shortened representation of these numerical combinations. In addition, when a parameter is stated as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0036] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0037] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0038] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it 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 it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0039] A battery cell includes electrode components and an electrolyte. The electrode components include a positive electrode, a negative electrode, and a separator. The separator is positioned between the positive and negative electrodes to separate them while allowing active ions to pass through. During the battery cell's charge-discharge cycle, the positive electrode active material provides the lithium ions needed for the repeated insertion and extraction between the positive and negative electrodes. Positive electrode active materials include lithium manganese oxide, lithium iron phosphate, lithium cobalt oxide, and lithium nickel cobalt manganese oxide, among others. Lithium nickel cobalt manganese oxide has a relatively high energy density and is widely used.

[0040] During the process of forming the positive electrode film layer by rolling lithium nickel cobalt manganese oxide as the positive electrode active material, the lithium nickel cobalt manganese oxide has poor structural stability and is easily crushed, resulting in a relatively low compaction density of the positive electrode film layer, making it difficult to further improve the energy density of the battery cell.

[0041] In view of the above problems, this application proposes a battery cell comprising a positive electrode sheet containing lithium nickel cobalt manganese oxide. The lithium nickel cobalt manganese oxide contains 0.2 wt% to 1.0 wt% aluminum (Al), which enhances the structural stability of the lithium nickel cobalt manganese oxide, improves the material's pressure resistance, and thus increases the compaction density of the electrode sheet and the energy density of the battery cell. The lithium nickel cobalt manganese oxide is mainly composed of single-crystal particles, which have better power performance and are beneficial for reducing the internal resistance of the battery cell. The technical solution of this application will now be described in detail.

[0042] battery cell

[0043] In one aspect, this application proposes a battery cell.

[0044] The battery cell includes a positive electrode sheet, which includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer contains lithium nickel cobalt manganese oxide, which includes single crystal particles. The lithium nickel cobalt manganese oxide includes nickel (Ni) and aluminum (Al) elements. The proportion of Ni element to the total number of transition metal atoms in the lithium nickel cobalt manganese oxide is 50% to 70%, and the mass content of Al element to the total mass of the lithium nickel cobalt manganese oxide is 0.2 wt% to 1.0 wt%.

[0045] The lithium nickel cobalt manganese oxide in this application primarily uses single-crystal particles. Single-crystal particles exhibit better power performance, reducing the internal resistance of individual battery cells and enabling them to withstand higher voltages. However, in related technologies, when preparing lithium nickel cobalt manganese oxide as a positive electrode film, it requires rolling. Single-crystal particles have poor structural stability and are easily crushed under high-pressure rolling, making it difficult to prepare a high-density positive electrode film and further improve the energy density of the individual battery cells. This application, however, improves the capacity and structural stability of the lithium nickel cobalt manganese oxide material under high pressure by controlling the elements within the lithium nickel cobalt manganese oxide, thereby enhancing the energy density of the individual battery cells.

[0046] The specific mechanism of the implementation method of this application is speculated to be as follows:

[0047] The nickel, cobalt, and manganese elements in lithium nickel cobalt manganese oxide (LCO) exhibit a synergistic effect, with varying impacts on the material's electrochemical performance. Cobalt contributes to improving the structural stability of LCO and mitigates cation mixing to some extent, enhancing electronic conductivity and cycle performance. Manganese contributes to improving the structural stability and reliability of LCO. Nickel exists in divalent, trivalent, and tetravalent forms. The redox couples composed of these nickel ions at different valences have lower potentials, resulting in more lithium ion release at higher voltages (e.g., ≥4.3V), allowing for greater energy storage. Increasing the number of nickel atoms improves the capacity of LCO, particularly when nickel constitutes 50% to 70% of the total transition metal atoms. Further increases in nickel atom count contribute less to capacity improvement, and the cation mixing between nickel and lithium ions becomes more pronounced, leading to decreased rate performance and cycle performance. For example, the percentage 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 any range of two of the above values.

[0048] Introducing aluminum into lithium nickel cobalt manganese oxide (LCM) has several drawbacks. When the aluminum content is too low (less than 0.2 wt%), its effect on structural stability is limited, resulting in poor pressure resistance and a risk of damage during electrode fabrication. Conversely, when the aluminum content is too high (greater than 1.0 wt%), it may increase lithium-ion transport resistance, leading to increased internal resistance. Therefore, in this embodiment, the aluminum content relative to the total mass of LCM is set to 0.2 wt% to 1.0 wt%, resulting in a more stable structure, improved pressure resistance, and consequently, increased electrode compaction density, thus enhancing the energy density of the battery cell. Optionally, an aluminum content of 0.4 wt% to 1 wt% further improves the structural stability of LCM.

[0049] For example, the mass content of aluminum 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 any range of two of the above values.

[0050] Aluminum can be deposited on the surface of lithium nickel cobalt manganese oxide (LCM) to act as a coating, improving its structural stability; or it can be located within the crystal phase of LCM to stabilize the crystal lattice structure; or it can be located both on the surface and within the crystal phase of LCM. If aluminum can be detected when analyzing LCM, it is considered that LCM contains aluminum.

[0051] In some embodiments, the single crystal particle includes an inner region and an outer region, wherein the outer region is a region extending 500 nm directly from any point on the outer surface of the single crystal particle toward the interior of the single crystal particle; the Al element is at least distributed in the outer region.

[0052] The inner region of a single crystal particle can be understood as the core of the single crystal particle, and the outer region covers the inner region. There may be no clear boundary between the outer region and the inner region. The outer region and the inner region can be considered as two artificially defined regions. The outer region is the region that extends 500 nm from any point on the outer surface of the single crystal particle toward the interior 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 500 nm.

[0053] The volume average particle size D of single crystal particles vWhen 50 ≤ 500 nm, Al can be considered to be distributed on the surface and inside of single crystal particles.

[0054] Al (Al) is distributed at least in the outer region, which can improve the structural stability and withstand voltage of lithium nickel cobalt manganese oxide (LiNiCoMnO4), thus increasing the compaction density of the cathode film and consequently improving the energy density of the battery cell. Optionally, non-uniform Al distribution in the outer region can further enhance the structural stability of LiNiCoMnO4. Non-uniformity can be understood as a difference in the distribution of Al in the outer region; for example, the content may be relatively high in one location and relatively low in another. Of course, in addition to being distributed in the outer region, Al can also be further distributed in the inner region.

[0055] In some embodiments, the lithium nickel cobalt manganese oxide further includes at least one element selected from Ti, Zr, Mg, V, P, S, and B; the total mass content of Ti, Zr, Mg, V, P, S, and B is 2000 ppm to 3000 ppm. These elements can improve the cycle 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 improve the cycle performance of the battery cell.

[0056] For example, the total mass content of Ti, Zr, Mg, V, P, S and B can be 2000ppm, 2100ppm, 2200ppm, 2300ppm, 2400ppm, 2500ppm, 2600ppm, 2700ppm, 2800ppm, 2900ppm, 3000ppm or any range of two of the above values.

[0057] In this embodiment, the elemental content in the positive electrode active material is defined in a way known in the art and can be detected using equipment and methods known in the art. For example, referring to EPA 6010D-2014, it can be measured by inductively coupled plasma atomic emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). First, 0.4g of the positive electrode active material is weighed and 10ml (50% concentration) of aqua regia is added. Then, it is placed on a plate at 180℃ for 30min. After digestion on the plate, the volume is adjusted to 100mL, and quantitative testing is performed using the standard curve method.

[0058] In some embodiments, the volume average particle size D of the single crystal particles v50 represents a particle size ranging from 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 any combination of two of the above values. The volume average particle size D of the single crystal is... v When 50 is within the above range, it is beneficial to further increase the compaction density, thereby increasing the energy density.

[0059] In the embodiments of this application, the volume average particle size D v 50 has a well-known meaning in the art, referring to the volume average particle size D. v 50 refers to the particle size corresponding to 50% of the volume distribution. This can be detected using equipment and methods known in the art. For example, freshly prepared positive electrode active material can be used as a sample for testing, or a fully discharged battery (discharged to the lower cutoff voltage so that the battery's state of charge is approximately 0% SOC) can be disassembled in reverse, the positive electrode sheet can be removed, and the positive electrode film layer can be scraped off from the positive electrode current collector as a test sample. After drying the positive electrode active material of the test sample, the volume average particle size D of the particles can be tested using a Mastersizer 2000E laser particle size analyzer according to the testing standard GB / T 19077-2016. v 50. In the embodiments of this application, a fresh battery cell may be a battery cell that has just left the factory (which has not been charged and discharged after formation) or a battery cell that has been assembled on an electrical device and has been used for less than 10 cycles.

[0060] In some embodiments, the compaction density of the single-sided positive electrode film is 3.3 g / cm³. 3 Up to 3.6 g / cm 3 For example, 3.30 g / cm³ 3 3.35g / cm 3 3.40 g / cm 3 3.45g / cm 3 3.50g / cm 3 3.55g / cm 3 3.60g / cm 3 Or it can be a range consisting of any two of the above values. When the compaction density of the single-sided positive electrode film is within the above range, it can effectively improve the energy density of the battery cell.

[0061] In this embodiment, the compaction density of the positive electrode film has a meaning known in the art and can be tested using methods known in the art. For example, take a positive electrode sheet that has been coated on one side and cold-pressed (if it is a positive electrode sheet coated on both sides, the positive electrode film layer on one side can be wiped off first), cut it into a small circular piece with an area of ​​S1, weigh it, and record its weight as M1. Then wipe off the positive electrode film layer of the above-weighed positive electrode sheet, weigh the positive current collector, and record it as M0. The areal density of the positive electrode film layer = (weight of the positive electrode sheet M1 - weight of the positive current collector M0) / S1, and the compaction density of the positive electrode film layer = areal density of the positive electrode film layer / thickness of the positive electrode film layer.

[0062] In some embodiments, the positive electrode film layer may optionally include a positive electrode conductive agent. This application does not impose particular limitations on the type of positive electrode conductive agent; as an example, the positive electrode conductive agent includes at least one selected from 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.

[0063] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. This application does not impose particular limitations on the type of positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. In some embodiments, the mass content of the positive electrode binder is ≤5 wt% based on the total mass of the positive electrode film layer.

[0064] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector and comprising a positive active material. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0065] In some embodiments, the positive 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 substrate and a metal material layer formed on at least one surface of the polymer substrate. As an example, 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 substrate may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0066] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to it.

[0067] Electrolyte

[0068] In some implementations, the battery cell also includes an electrolyte.

[0069] In some embodiments, the electrolyte comprises lithium hexafluorophosphate (LiPF6), wherein the mass content of lithium hexafluorophosphate relative to the total mass of the electrolyte is 12 wt% to 18 wt%; optionally, it is 12 wt% to 16 wt%. For example, the mass content of lithium hexafluorophosphate relative to the total mass of the electrolyte can be 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, or a range of any two of the above values.

[0070] In some embodiments, the electrolyte further includes difluorophosphate, with a difluorophosphate content of 300 ppm to 3000 ppm based on the total mass of the electrolyte. For example, the difluorophosphate content 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 of any two of the above values.

[0071] When the mass content of difluorophosphate is within the above range, on the one hand, difluorophosphate can associate with the Al element in lithium nickel cobalt manganese oxide, which can reduce the dissolution of Al element and improve the stability of lithium nickel cobalt manganese oxide in the cycle process of battery cell; on the other hand, difluorophosphate can form a cathode electrolyte interphase (CEI) film on the surface of the cathode film, which can slow down the interfacial side reaction between the cathode film and the electrolyte and further reduce the internal resistance of the battery cell.

[0072] 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 lithium nickel cobalt manganese oxide, making the lithium nickel cobalt manganese oxide more stable under high voltage, thus enabling the lithium nickel cobalt manganese oxide to stably output capacity under high voltage.

[0073] Optionally, based on the total mass of the electrolyte, the mass content of tetrafluoroborate is from 100 ppm to 1000 ppm; optionally, it is from 150 ppm to 600 ppm. For example, the mass content of tetrafluoroborate can be 100 ppm, 150 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, or any combination of two of the above values. The above-mentioned mass content of tetrafluoroborate can improve the modification effect on the surface of lithium nickel cobalt manganese oxide, making the lithium nickel cobalt manganese oxide more stable under high voltage, and enabling the lithium nickel cobalt manganese oxide to stably output capacity under high voltage.

[0074] Optionally, based on the total mass of the electrolyte, the fluorosulfonate content is from 100 ppm to 1000 ppm; alternatively, it is from 150 ppm to 600 ppm. For example, the fluorosulfonate content can be 100 ppm, 150 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, or any combination of two of the above values. The fluorosulfonate content at the above-mentioned mass levels can improve the modification effect on the surface of lithium nickel cobalt manganese oxide, making the lithium nickel cobalt manganese oxide more stable under high voltage, and enabling the lithium nickel cobalt manganese oxide to stably output capacity under high voltage.

[0075] The cations corresponding to the tetrafluoroborate and fluorosulfonate ions mentioned above can be lithium ions, sodium ions, etc., and lithium ions can be selected.

[0076] In some embodiments, the electrolyte further includes an organic solvent comprising ethyl methyl carbonate (EMC) and ethylene carbonate (EC); based on the total mass of the electrolyte, the mass ratio of EMC to EC is 1:(0.4 to 0.6). The organic solvent comprises EMC and EC, with a relatively high amount of EMC and a relatively low amount of EC, resulting in a low viscosity of the electrolyte; the organic solvent and the high compaction density (e.g., 3.3 g / cm³) are also considered. 3 Up to 3.6 g / cm 3 When used in conjunction with the positive electrode film layer, it helps to reduce the internal resistance of the battery cell.

[0077] For example, the mass ratio of ethyl methyl carbonate (EMC) to 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 of any two of the above values.

[0078] For example, based on the total mass of the electrolyte, the mass content of ethyl methyl carbonate (EMC) is 50 wt% to 70 wt%; for example, 50 wt%, 51 wt%, 52 wt%, 53 wt%, 54 wt%, 55 wt%, 56 wt%, 57 wt%, 58 wt%, 59 wt%, 60 wt%, 61 wt%, 62 wt%, 63 wt%, 64 wt%, 65 wt%, 66 wt%, 67 wt%, 68 wt%, 69 wt%, 70 wt%, or a range of any two of the above values.

[0079] For example, based on the total mass of the electrolyte, the mass content of ethylene carbonate EC is 20 wt% to 30 wt%, such as 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 of any two of the above values.

[0080] In some embodiments, the electrolyte further includes lithium bis(fluorosulfonyl)imide (LiFSI), wherein the mass content of LiFSI relative to the total mass of the electrolyte is 2 wt% to 4 wt%. This mass content of LiFSI can improve the conductivity and high flatness (3.3 g / cm³) of the electrolyte. 3 Up to 3.6 g / cm 3 When used in conjunction with the positive electrode film layer, it can effectively reduce the internal resistance of the battery cell.

[0081] For example, based on the total mass of the electrolyte, the mass content of lithium bisfluorosulfonylimide (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 any range of two of the above values.

[0082] The qualitative and quantitative analysis of each substance or element in this application can be performed using suitable equipment and methods known to those skilled in the art. Relevant testing methods can be referenced from domestic and international testing standards and enterprise standards. Furthermore, those skilled in the art can adaptively modify certain testing steps / instrument parameters from the perspective of testing accuracy to obtain more accurate results. One testing method can be used for qualitative or quantitative analysis, or several testing methods can be used in combination for qualitative or quantitative determination.

[0083] In the embodiments of this application, the types and contents of inorganic components / lithium salt concentrations in the electrolyte are well-known in the art and can be detected using equipment and methods known in the art. For example, the concentrations of inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis using standard JY / T020-1996 "General Rules for Ion Chromatography Analysis". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, or a fully discharged battery (discharged to the lower limit cutoff voltage so that the battery's state of charge is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample for detection by ion chromatography analysis.

[0084] In the embodiments of this application, the types and contents of organic components in the electrolyte are defined in the art and can be detected using equipment and methods known in the art. For example, the organic components in the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography using GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, or a fully discharged battery (discharged to the lower limit cutoff voltage so that the battery's state of charge is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample for detection using ion chromatography.

[0085] For example, to test the composition of an additive in an electrolyte using liquid chromatography-nuclear magnetic resonance (NMR), taking the detection of lithium difluorophosphate and lithium hexafluorophosphate as an example, a 7ml glass bottle is prepared in a nitrogen-filled glove box. 5ml of NMR reagent premix is ​​added to the bottle, and the mixture is left to stand for 24 hours at room temperature (20-25°C) in a nitrogen-filled glove box. This allows the electrolyte in the electrode and separator to diffuse into the NMR premix, thus obtaining the NMR test sample. The NMR premix consists of 100ml of deuterated acetonitrile with 3ml of trifluoromethylbenzene (C7H5F3). This NMR reagent premix is ​​pre-dried using molecular sieve 4A (100ml of NMR reagent premix is ​​added to 15g of freshly opened 4A molecular sieve and dried in a nitrogen-filled glove box at room temperature (20-25°C) for more than 30 days). 19F NMR measurement is performed (NMR: Bruker Avance 400HD).

[0086] To identify and quantify each species, the following settings were used for the flip angle and scan time.

[0087] Fluorine spectrum test pulse sequence: 2gfhigqn.2;

[0088] Delay time: 1 second;

[0089] Number of scans: 16;

[0090] The relative contents of trifluoromethylbenzene and LiPF6 were calculated based on the integrated peak intensities of their respective signals in F-NMR. The calculation method is as follows:

[0091] Relative content of LiPF6 = (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.

[0092] The content of the electrolyte in the deuterated reagent was calculated based on the content of lithium hexafluorophosphate (LiPF6).

[0093] Based on trifluoromethylbenzene and PO2F2 in F-NMR - The relative content of two substances is calculated by integrating the signal peak intensities of the two substances. The calculation method is as follows:

[0094] 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.

[0095] In some embodiments, the various solutes or solvents in the electrolyte mentioned in this application include substances actively added during the preparation of the electrolyte, as well as substances derived from substances already present in the electrolyte during the preparation of the electrolyte, the process of making a battery from the electrolyte, or the storage or use of a battery containing the electrolyte.

[0096] [Negative electrode plate]

[0097] In some implementations, the battery cell also includes a negative electrode.

[0098] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and comprising a negative electrode active material. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0099] The negative electrode active material may be any negative electrode active material known in the art for use in battery cells. As an 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.

[0100] In some embodiments, the negative electrode film layer may include at least one of artificial graphite and natural graphite, preferably artificial graphite, which has relatively high structural stability.

[0101] In the embodiments of this application, the graphite material can be subjected to X-ray powder diffraction testing and qualitative analysis of the negative electrode sheet or negative electrode active material in accordance with the general rules of X-ray diffraction analysis in JIS / K0131-1996.

[0102] In some embodiments, the mass content of artificial graphite is greater than or equal to 85 wt% and less than 100 wt% based on the total mass of the negative electrode film. For example, the mass content of 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 of any two of the above values.

[0103] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose particular limitations on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one selected from 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.

[0104] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. This application does not impose particular limitations on the type of negative electrode binder. As an example, the negative electrode binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, and waterborne acrylic resins (e.g., at least one of 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.

[0105] In some embodiments, the negative electrode film may optionally include other additives. As examples, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass content of other additives is ≤2 wt% based on the total mass of the negative electrode film.

[0106] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include at least one of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, and polyethylene.

[0107] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0108] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the present application further includes a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) 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 present application further includes a protective layer covering the surface of the negative electrode film layer.

[0109] In some implementations, the positive electrode, separator, and negative electrode can be fabricated into an electrode assembly using a winding process and / or a stacking process.

[0110] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0111] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0112] The embodiments of this application do not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. Figure 1 The example shown is a square-structured battery cell 5.

[0113] In some implementations, such as Figure 2 As shown, the outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates enclosing a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 is used to cover the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process and / or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. Electrolyte is immersed 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 requirements.

[0114] The method for preparing the battery cell according to the embodiments of this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained.

[0115] In some embodiments of the present application, the battery cells according to the present application can be assembled into a battery module. The number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0116] Figure 3 This is a schematic diagram of battery module 4 as an example. Figure 3 As shown, in battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0117] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0118] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0119] Figure 4 and Figure 5 This is a schematic diagram of battery pack 1 as an example. Figure 4 and Figure 5As shown, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3. The upper body 2 covers the lower body 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0120] Electrical appliances

[0121] A second aspect of this application provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack described in this application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit of the electrical device. The electrical device can be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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.

[0122] Electrical devices can be equipped with individual battery cells, battery modules, or battery packs depending on their usage requirements.

[0123] Figure 6 This is a schematic diagram of an example electrical device 6. This electrical device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device 6, a battery pack or battery module can be used.

[0124] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0125] Example

[0126] The following embodiments describe the contents disclosed in this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of the embodiments of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0127] Example 1

[0128] 1. Preparation of positive electrode sheet

[0129] The positive electrode sheet includes a positive current collector aluminum foil and a positive electrode film layer. The positive electrode film layer is formed by uniformly coating a positive electrode slurry (solvent being N-methylpyrrolidone NMP) onto the surface of the positive current collector aluminum foil, followed by drying and cold pressing. The positive electrode film layer includes positive electrode active material, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:1.4:1.1.

[0130] The positive electrode active material includes lithium nickel cobalt manganese oxide single crystal particles, which also include aluminum (Al) and nickel (Ni).

[0131] 2. Preparation of negative electrode sheet

[0132] The negative electrode sheet includes a negative current collector copper foil and a negative electrode film layer. The negative electrode film layer is formed by uniformly coating the surface of the negative current collector copper foil with a negative electrode slurry (solvent is deionized water), and then drying and cold pressing it. 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.

[0133] Negative electrode active materials include artificial graphite.

[0134] 3. Separating membrane

[0135] The separator is a porous polypropylene membrane.

[0136] 4. Preparation of electrolyte

[0137] The electrolyte consists of organic solvents, lithium salts, and additives.

[0138] 5. Battery manufacturing

[0139] A lithium-ion battery includes an outer casing, an electrode assembly, and an electrolyte. The electrode assembly and electrolyte are disposed inside the outer casing. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The electrode assembly is a wound electrode assembly, and the separator is disposed between the positive electrode and the negative electrode.

[0140] Comparative Example 1 and Comparative Example 2

[0141] Lithium-ion batteries were prepared using a method similar to that of Example 1, except that the mass content of Al was adjusted.

[0142] Examples 2-1 to 2-4

[0143] A lithium-ion battery was prepared using a method similar to that in Example 1, except that the mass content of Al in the positive electrode active material was adjusted.

[0144] Example 3

[0145] A lithium-ion battery was prepared using a method similar to that of Example 1, except that the positive electrode active material also included Zr.

[0146] Examples 4-1 and 4-2

[0147] A lithium-ion battery was prepared using a method similar to that in Example 1, except that the volume average particle size of the single crystal particles of the positive electrode active material was adjusted.

[0148] Examples 5-1 and 5-2

[0149] A lithium-ion battery was prepared using a method similar to that in Example 1, except that the atomic percentage of Ni in the positive electrode active material was adjusted.

[0150] Performance testing

[0151] 1. Energy density of a single battery cell

[0152] In the embodiments of this application, the term "energy density" refers to the volumetric (typically expressed in Wh / L) or gravimetric (typically expressed in Wh / kg) energy transferred during each charge / discharge cycle. This application uses gravimetric energy density to characterize the energy density of a single battery cell. For example, the battery cells prepared in the examples and comparative examples are charged at 1C constant current to 4.35V, then charged at constant voltage to 0.05C, left to stand for 30 min, and then 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).

[0153] 2. Internal resistance of individual battery cells

[0154] At 25°C, the state of charge (SOC) of the battery cells prepared in the examples and comparative examples was adjusted to 20% of the full charge capacity. They were 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. Then, the initial DC internal resistance of the battery cell DCR0 = (U1-U2) / I.

[0155] Test Results

[0156] The test results are shown in Table 1.

[0157] Table 1

[0158]

[0159] In Table 1,

[0160] The energy density of Comparative Example 1 is 230Wh / Kg. The relative energy density values ​​of the embodiments in Table 1 are percentages of the energy density of the embodiments to the energy density of Comparative Example 1, that is, values ​​calculated with the energy density of Comparative Example 1 as 100%.

[0161] The relative energy densities of other comparative examples are percentages of the energy densities of other comparative examples to the energy density of Comparative Example 1, i.e., values ​​calculated with the energy density of Comparative Example 1 as 100%.

[0162] The internal resistance of Comparative Example 1 is 29.5 mΩ. The relative internal resistance values ​​of the embodiments in Table 1 are percentages of the internal resistance of the embodiments to the internal resistance of Comparative Example 1, that is, values ​​calculated with the internal resistance of Comparative Example 1 as 100%.

[0163] The relative internal resistance values ​​of other comparative examples are percentages of the internal resistance of other comparative examples to the internal resistance of Comparative Example 1, that is, values ​​calculated with the internal resistance of Comparative Example 1 as 100%.

[0164] In Comparative Example 1, the aluminum (Al) content was too low, failing to effectively improve the structural stability of the lithium nickel cobalt manganese oxide. This resulted in the oxide being easily crushed during electrode fabrication, leading to a relatively low compaction density and energy density in the positive electrode film. In Comparative Example 2, the aluminum (Al) content was too high. While this effectively improved the structural stability of the lithium nickel cobalt manganese oxide and was beneficial for increasing energy density, the excessive Al content could increase lithium-ion migration resistance, leading to increased internal resistance.

[0165] In this embodiment of the application, by controlling the mass content of aluminum element to be 0.2wt% to 1.0wt%, especially to 0.4wt% to 0.7wt%, the structural stability of lithium nickel cobalt manganese oxide can be effectively improved, which is beneficial to the improvement of energy density; moreover, the lithium-ion transport performance is better, the power performance in single crystal particles is better, which is beneficial to reducing the internal resistance of battery cells.

[0166] In Example 3, the introduction of Zr into the positive electrode active material can effectively improve the stability of the crystal structure, which is beneficial to improving cycle performance, power performance and reducing internal resistance.

[0167] Examples 4-1 and 4-2, through the analysis of the volume average particle size D of single crystal particles v Adjusting the 50 can further improve power performance and reduce the internal resistance of individual battery cells.

[0168] Examples 5-1 and 5-2, by adjusting the proportion of Ni, can further improve power performance and reduce the internal resistance of individual battery cells.

[0169] Examples 6-1 to 6-4

[0170] Lithium-ion batteries were prepared using a method similar to that of Example 1, except that the mass content of difluorophosphate was adjusted.

[0171] Examples 7-1 to 7-7

[0172] Lithium-ion batteries were 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.

[0173] Examples 8-1 and 8-2

[0174] Lithium-ion batteries were prepared using a method similar to that of Example 1, except that the content and type of organic solvents were adjusted.

[0175] Examples 9-1 and 9-2

[0176] Lithium-ion batteries were prepared using a method similar to that in Example 1, except that the content of lithium bis(fluorosulfonyl)imide (LiFSI) was adjusted.

[0177] Table 2

[0178]

[0179] Examples 1, 6-1 to 9-2 also include 15 wt% lithium hexafluorophosphate (LiPF6) relative to the total mass of the electrolyte.

[0180] The electrolyte components of the comparative examples and embodiments not shown are the same as those in Example 1.

[0181] In Examples 1 and 6-1 to 6-4, the content of difluorophosphate was adjusted. Difluorophosphate can reduce the dissolution of Al and improve the stability of lithium nickel cobalt manganese oxide during the cycle of the battery cell. Difluorophosphate can also form a CEI film on the surface of the positive electrode film, which can slow down the interfacial side reaction between the positive electrode film and the electrolyte and further reduce the internal resistance of the battery cell.

[0182] Examples 7-1 and 7-7 show that adjusting the content of at least one of tetrafluoroborate and fluorosulfonate can improve the cycle stability of lithium nickel cobalt manganese oxide and reduce the internal resistance of the battery cell.

[0183] Examples 8-1 and 8-2 demonstrate that by adjusting the mass ratio of ethyl methyl carbonate (EMC) to ethylene carbonate (EC), the internal resistance of a single battery cell can be effectively improved.

[0184] Examples 9-1 and 9-2 demonstrate that by controlling the mass content of lithium bis(fluorosulfonyl)imide (LiFSI), the internal resistance of a single battery cell can be effectively improved.

[0185] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A battery cell, characterized in that, The device includes a positive electrode sheet and a separator. The positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer contains lithium nickel cobalt manganese oxide, which comprises single-crystal particles. The lithium nickel cobalt manganese oxide includes: Ni element, comprising 50% to 70% of the total number of transition metal atoms in the lithium nickel cobalt manganese oxide; and The Al element has a mass content of 0.4 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, characterized in that, The single crystal particle includes an inner region and an outer region. The outer region is a region extending 500 nm directly 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.

3. The battery cell according to claim 2, characterized in that, Al is not uniformly distributed in the outer region.

4. The battery cell according to claim 1, characterized in that, The lithium nickel cobalt manganese oxide also includes at least one element selected from Ti, Zr, Mg, V, P, S, and B; The total mass content of the elements Ti, Zr, Mg, V, P, S, and B is between 2000 ppm and 3000 ppm.

5. The battery cell according to claim 1, characterized in that, The battery cell also includes an electrolyte, which includes lithium hexafluorophosphate, and the lithium hexafluorophosphate has a mass content of 12 wt% to 18 wt% relative to the total mass of the electrolyte.

6. The battery cell according to claim 5, characterized in that, The lithium hexafluorophosphate content relative to the total mass of the electrolyte is 12 wt% to 16 wt%.

7. The battery cell according to claim 5 or 6, characterized in that, The electrolyte also includes difluorophosphate. Based on the total mass of the electrolyte, the mass content of difluorophosphate is between 300 ppm and 3000 ppm.

8. The battery cell according to claim 5 or 6, characterized in that, The electrolyte also includes tetrafluoroborate and fluorosulfonate. Based on the total mass of the electrolyte, the mass content of tetrafluoroborate is from 100 ppm to 1000 ppm; and / or Based on the total mass of the electrolyte, the mass content of the fluorosulfonate is between 100 ppm and 1000 ppm.

9. The battery cell according to claim 8, characterized in that, The mass content of the tetrafluoroborate is from 150 ppm to 600 ppm.

10. The battery cell according to claim 8, characterized in that, The mass content of the fluorosulfonate is from 150 ppm to 600 ppm.

11. The battery cell according to claim 5 or 6, characterized in that, The electrolyte also includes an organic solvent, which includes 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).

12. The battery cell according to claim 11, characterized in that, Based on the total mass of the electrolyte, the mass content of ethyl methyl carbonate (EMC) is 50 wt% to 70 wt%; or Based on the total mass of the electrolyte, the mass content of ethylene carbonate EC is 20 wt% to 30 wt%.

13. The battery cell according to claim 5 or 6, characterized in that, The electrolyte also includes lithium bisfluorosulfonyl imide (LiFSI), wherein the mass content of lithium bisfluorosulfonyl imide (LiFSI) relative to the total mass of the electrolyte is 2 wt% to 4 wt%.

14. The battery cell according to claim 13, characterized in that, The compaction density of the positive electrode film layer on one side is 3.3 g / cm³. 3 Up to 3.6 g / cm 3 .

15. The battery cell according to any one of claims 1 to 6, characterized in that, The volume average particle size D of the single crystal particles v 50 ranges from 2.5 μm to 4.0 μm.

16. The battery cell according to any one of claims 1 to 6, characterized in that, The battery cell further includes a negative electrode sheet, which includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes at least one of artificial graphite and natural graphite.

17. A battery, characterized in that, Includes the battery cell as described in any one of claims 1 to 16.

18. An electrical appliance, characterized in that, Includes the battery as described in claim 17.

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