Battery cell and method for producing the same, electric device

Abstract

A battery monomer, a preparation method thereof, and an electric device. The battery monomer comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer, the positive electrode film layer is arranged on at least one side surface of the positive electrode current collector, and the positive electrode film layer comprises a first metal oxide, a second metal oxide, and a surfactant; a chemical formula of the first metal oxide satisfies: Li5MO4, wherein M comprises one or more of Fe, Cr, V, and Mo; a chemical formula of the second metal oxide satisfies: Li a N b O2, wherein a:b>1, 1

Description

Technical Field

[0001] This application relates to the technical field of batteries, and more specifically, to a battery cell, a preparation method thereof, and an electrical device. Background Art

[0002] The new energy industry has attracted increasing attention. In the new energy industry, battery technology is an important factor related to its development.

[0003] The development of battery technology needs to consider various design factors, such as energy density, cycle life, capacity, reliability, etc. As a lithium supplement material, lithium-rich metal oxide can provide active lithium ions to the battery to supplement the consumption of lithium ions in stages such as formation, thereby improving the capacity of the battery; for example, lithium-rich metal oxide can be added to the positive electrode film layer to supplement lithium for the battery; however, at the same time, there is a relatively obvious gas generation after the lithium-rich metal oxide is delithiated, which will affect the cycle performance of the battery, and the lithium-rich metal oxide material is generally alkaline, which will increase the instability of the slurry of the positive electrode film layer. Seriously, gelation will occur, resulting in uneven coating or inability to coat the slurry of the positive electrode film layer, and it is difficult to prepare a battery cell with less gas generation and higher first-cycle charging capacity. Therefore, how to provide a battery cell with less gas generation and higher first-cycle charging capacity is an urgent technical problem to be solved. Summary of the Invention

[0004] This application is made in view of the above problems, and its purpose is to provide a battery cell with less gas generation and higher first-cycle charging capacity.

[0005] To achieve the above purpose, this application provides a battery cell, a preparation method thereof, and an electrical device.

[0006] In the first aspect, a battery cell is provided, including a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer, the positive electrode film layer is disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a first metal oxide, a second metal oxide, and a surfactant; the chemical formula of the first metal oxide satisfies: Li5MO4, where M includes one or more of Fe, Cr, V, and Mo; the chemical formula of the second metal oxide satisfies: Li a N b O2, where a:b>1, 1<a≤2, 0<b≤1, and N includes one or more of Cu, Co, Mg, Zn, Mn, Al, Ni, Zr, Ti, and Fe; the surfactant includes: one or more of phosphate esters, acrylate esters, hydrogenated nitrile rubber, and polyvinylpyrrolidone.

[0007] In the embodiments of the present application, the first metal oxide and the second metal oxide can provide lithium ions, thereby supplementing the lithium ions consumed during the formation of the SEI film of the battery cell, which is beneficial to improving the first-cycle charging capacity of the battery cell. The positive electrode film layer further includes surfactants such as phosphate esters, acrylate esters, hydrogenated nitrile, and polyvinylpyrrolidone, which can effectively reduce the viscosity of the positive electrode slurry, thus facilitating the uniform coating of the positive electrode slurry on the positive electrode current collector and enabling the first metal oxide and the second metal oxide in the positive electrode film layer of the positive electrode sheet to effectively play their roles, so as to improve the first-cycle charging capacity of the battery cell. Moreover, when the positive electrode film layer simultaneously includes the above-mentioned first metal oxide and second metal oxide, the gas generation amount of the battery cell during the aging stage after formation can be reduced. Therefore, the technical solution of the embodiments of the present application can reduce the gas generation in the battery cell while improving the first-cycle charging capacity of the battery cell.

[0008] In a possible implementation manner, based on the total mass of the positive electrode film layer, the mass percentage content P1 of the surfactant satisfies: 0% < P1 ≤ 2%. In this way, during the preparation of the battery cell, the viscosity of the positive electrode slurry can be within an appropriate range, which is beneficial to the coating of the positive electrode slurry.

[0009] In a possible implementation manner, 0.2% ≤ P1 ≤ 1%. In this way, the positive electrode slurry can have a more appropriate viscosity, which is further beneficial to the coating of the positive electrode slurry.

[0010] In a possible implementation manner, based on the total mass of the positive electrode film layer, the mass percentage content P2 of the first metal oxide satisfies: 0% < P2 ≤ 8%. The first metal oxide has an appropriate content ratio in the positive electrode film layer. In this way, the battery cell has a relatively high first-cycle charging capacity.

[0011] In a possible implementation manner, 0.8% ≤ P2 ≤ 4%. In this way, it is beneficial to further improve the first-cycle charging capacity of the battery cell.

[0012] In a possible implementation manner, based on the total mass of the positive electrode film layer, the mass percentage content P3 of the second metal oxide satisfies: 0% < P3 ≤ 2%. The second metal oxide has an appropriate content ratio in the positive electrode film layer. In this way, the battery cell has a relatively high first-cycle charging capacity and a relatively small gas generation amount.

[0013] In a possible implementation manner, 0.2% ≤ P3 ≤ 1%. In this way, it is beneficial to further improve the first-cycle charging capacity of the battery cell and reduce the gas generation amount of the battery cell during the aging stage.

[0014] In one possible implementation, the surface of the second metal oxide is coated with oxide and / or carbon materials. This improves the conductivity of the second metal oxide, thereby increasing the initial charge capacity of the battery cell.

[0015] In one possible implementation, the oxide comprises a metal element, including one or more of Ni, W, Cu, Mn, Al, Fe, Ti, Mo, Ce, Co, Cr, or V. Oxides comprising these metal elements exhibit good electrical conductivity, which is beneficial for improving the conductivity of the second metal oxide, and consequently, for increasing the initial charge capacity of the battery cell.

[0016] In one possible implementation, the oxide comprises Al2O3.

[0017] In one possible implementation, based on the total mass of the second metal oxide and the oxide, the mass percentage P5 of the oxide satisfies: 0.1% ≤ P5 ≤ 10%. By setting the mass content of the oxide within the above range, the conductivity of the second metal oxide and the amount of lithium ions released can be balanced, which is beneficial to improving the first-cycle charging capacity of the battery cell.

[0018] In one possible implementation, 0.5% ≤ P5 ≤ 5%.

[0019] In one possible implementation, the positive electrode film layer further includes a positive electrode active material, wherein the volume average particle size Dv50 of the positive electrode active material satisfies: 0.5 μm ≤ Dv50 ≤ 10 μm. By setting the volume average particle size of the positive electrode active material within the above range, it is beneficial to improve the initial charge capacity of the battery cell and its long-term cycle performance.

[0020] In one possible implementation, 0.5μm ≤ Dv50 ≤ 5μm. This is beneficial for further improving the initial charge capacity of the battery cells and their long-term cycle performance.

[0021] In one possible implementation, based on the total mass of the positive electrode film, the mass percentage P4 of the positive electrode active material satisfies: 80% ≤ P4 ≤ 95%. This allows the battery cell to have higher initial charge capacity, higher overall capacity, and better long-term cycle performance.

[0022] In one possible implementation, the positive electrode active material comprises a lithium-containing phosphate with an olivine structure, wherein the lithium-containing phosphate with the olivine structure includes lithium iron phosphate. This results in a more stable positive electrode active material, which is beneficial for improving the long-term performance and lifespan of the battery cell.

[0023] In a possible implementation, the positive electrode active material further includes a carbon material, and the carbon material coats the surface of the lithium-containing phosphate to form a carbon coating layer. In this way, it is beneficial to improve the conductivity of the positive electrode active material, and thus beneficial to improve the first-cycle charging capacity and long-term cycling performance of the battery cell.

[0024] In a possible implementation, the thickness L of the carbon coating layer satisfies: 0 < L ≤ 10 nm. By setting the thickness of the carbon coating layer within the above range, it is beneficial to improve the first-cycle charging capacity and long-term cycling performance of the battery cell.

[0025] In a possible implementation, 1 nm ≤ L ≤ 5 nm. In this way, it is beneficial to further improve the first-cycle charging capacity and long-term cycling performance of the battery cell.

[0026] In a possible implementation, the powder resistivity R of the positive electrode active material under 20 MPa satisfies: 2 Ω·cm ≤ R ≤ 50 Ω·cm. By setting the powder resistivity of the positive electrode active material under 20 MPa within the above range, in this way, the positive electrode active material has high conductivity, which is beneficial to improve the capacity and long-term cycling performance of the battery cell.

[0027] In a possible implementation, 5 Ω·cm ≤ R ≤ 20 Ω·cm. In this way, it is beneficial to further improve the capacity and long-term cycling performance of the battery cell.

[0028] In a possible implementation, the battery cell is the battery cell before formation. After the formation process, lithium ions in the first metal oxide and the second metal oxide in the positive electrode plate of the battery cell are removed, thereby improving the first-cycle charging capacity of the battery cell.

[0029] In a second aspect, a method for preparing a battery cell is provided, including: providing a positive electrode plate to prepare the battery cell; wherein, the providing of the positive electrode plate includes: mixing a first metal oxide, a second metal oxide and a surfactant to obtain a slurry for the positive electrode film layer, wherein the chemical formula of the first metal oxide satisfies: Li5MO4, where M includes one or more of Fe, Cr, V, Mo, and the chemical formula of the second metal oxide satisfies: Li a N b O2, where a:b > 1, 1 < a ≤ 2, 0 < b ≤ 1, N includes one or more of Cu, Co, Mg, Zn, Mn, Al, Ni, Zr, Ti, Fe, and the surfactant includes: one or more of phosphate esters, acrylate esters, hydrogenated nitrile butadiene, polyvinylpyrrolidone; coating the slurry of the positive electrode film layer on at least one side surface of the current collector to provide the positive electrode plate.

[0030] The slurry formed by mixing the first metal oxide, the second metal oxide, and the surfactant is beneficial for uniform coating of the slurry. The above-mentioned method for preparing the positive electrode sheet is relatively simple and has low complexity. Furthermore, when the prepared positive electrode sheet is applied to a battery cell, the battery cell has a high first-cycle charging capacity and a small amount of gas production.

[0031] In one possible implementation, the viscosity η of the slurry satisfies: 5000 mPa·s < η ≤ 30000 mPa·s. Setting the viscosity of the slurry for the positive electrode film layer within the above range is beneficial for the uniform coating of the positive electrode slurry and for the effective functioning of the first and second metal oxides in the positive electrode film layer of the positive electrode sheet, thereby improving the first charge capacity of the battery cell and reducing gas generation in the battery cell.

[0032] In one possible implementation, 7000 mPa·S < η ≤ 10000 mPa·S. This further facilitates the uniform coating of the positive electrode slurry, thereby improving the first-cycle charging capacity of the battery cell and further reducing gas generation in the battery cell.

[0033] Thirdly, an electrical device is provided, comprising a battery cell as described in the first aspect and any possible implementation thereof, and / or a battery cell obtained by the preparation method of the second aspect.

[0034] In one possible implementation, the electrical device includes an energy storage device or a heavy-duty truck. Energy storage devices and heavy-duty trucks have high requirements for the lifespan and long-term cycle performance of individual battery cells; applying individual battery cells to these electrical devices can improve their lifespan. Attached Figure Description

[0035] 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.

[0036] Figure 1 This is a schematic diagram of the structure of a positive electrode sheet according to an embodiment of this application;

[0037] Figure 2 This is a schematic diagram of a battery cell according to an embodiment of this application;

[0038] Figure 3 This is a schematic diagram of a method for preparing a battery cell according to an embodiment of this application;

[0039] Figure 4This is a schematic diagram of a battery according to an embodiment of this application;

[0040] Figure 5 This is a schematic diagram of an electrical device according to an embodiment of this application;

[0041] Figure 6 This is a schematic diagram of an electrical device according to an embodiment of this application. Detailed Implementation

[0042] The positive electrode sheet and its preparation method, as well as the embodiments of the battery cell, of this application have been described in detail with appropriate reference to the accompanying drawings. 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.

[0043] 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 a 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 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" 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 "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0045] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0046] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) 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 it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0047] The development of battery technology must consider multiple design factors simultaneously, such as energy density, cycle life, discharge capacity, charge / discharge rate, reliability, and initial charge capacity. During the formation of the SEI film in a battery cell, approximately 10% of the active lithium is consumed. This consumption of active lithium is detrimental to improving the cell's capacity. Adding lithium-replenishing materials to the battery cell can replenish active lithium; for example, adding lithium-rich metal oxides to the positive electrode can replenish active lithium, thereby improving the initial charge capacity. However, during charging, some high-oxygen-content lithium-rich metal oxides, due to the negative charge of oxygen, can contain more lithium ions. While delithiating, they release more active lithium ions to replenish capacity, but also release a significant amount of oxygen. This can disrupt the structural stability of the positive electrode film, and the oxygen dissolves in the electrolyte and undergoes side reactions with the electrolyte during subsequent charging processes (such as the aging stage after formation), leading to significant gas production in the battery cell, which is detrimental to improving its performance. Furthermore, lithium-rich metal oxide materials are generally alkaline, which increases the instability of the positive electrode film slurry. In severe cases, gelation can occur, leading to uneven or impossible coating of the positive electrode film slurry. This makes it difficult to prepare battery cells with low gas production and high first-charge capacity. Therefore, how to provide a battery cell with low gas production and high first-charge capacity is a technical problem that urgently needs to be solved.

[0048] In view of this, this application provides a battery cell, comprising: a positive electrode sheet; the positive electrode sheet includes: a positive current collector and a positive electrode film layer, the positive electrode film layer being disposed on at least one surface of the positive current collector, the positive electrode film layer comprising a first metal oxide, a second metal oxide, and a surfactant; the first metal oxide having the chemical formula: Li5MO4, wherein M includes one or more of Fe, Cr, V, and Mo; the second metal oxide having the chemical formula: Li a N bO2, where a:b > 1, 1 < a ≤ 2, 0 < b ≤ 1, and N includes one or more of Cu, Co, Mg, Zn, Mn, Al, Ni, Zr, Ti, Fe; the surfactant includes one or more of phosphate esters, acrylate esters, hydrogenated nitrile, polyvinylpyrrolidone. The combination of the first metal oxide and the second metal oxide is beneficial to increasing the initial charging capacity of the battery cell while reducing gas generation during the aging stage of the battery cell, thereby being beneficial to improving the performance of the battery cell. During the preparation of the battery cell, adding the above surfactant to the positive electrode slurry can effectively reduce the viscosity of the positive electrode slurry, which is conducive to uniformly coating the positive electrode slurry on the positive electrode current collector, facilitating the formation of the positive electrode film layer of the positive electrode plate, enabling the first metal oxide and the second metal oxide in the positive electrode film layer to effectively play their roles, so as to increase the initial charging capacity of the battery cell and reduce gas generation in the battery cell.

[0049] The first metal oxide and the second metal oxide in the embodiments of the present application can supplement lithium to the positive electrode plate, thereby compensating for the irreversible lithium loss of the positive electrode caused during the formation of the SEI film. During the charging process of the battery cell, lithium ions are released from the first metal oxide and the second metal oxide to provide active lithium ions.

[0050] The surfactant in the embodiments of the present application is added to the slurry of the positive electrode film layer during the preparation of the battery cell. This surfactant can reduce the viscosity of the slurry, which is conducive to uniform coating of the slurry.

[0051] During the charging process of the battery cell, lithium ions are released from the positive electrode active material, move and embed into the negative electrode; during the discharging process, lithium ions are released from the negative electrode, move and embed into the positive electrode active material.

[0052] It should be understood that the "embedding" process described in the present application refers to the process in which lithium ions are embedded in the positive electrode active material or the negative electrode due to an electrochemical reaction. The "releasing" and "deintercalation" processes described in the present application refer to the process in which lithium ions are released from the positive electrode active material or the negative electrode due to an electrochemical reaction.

[0053] In the embodiments of the present application, formation can be understood as the initialization of the battery cell, the process of activating the active substances of the battery cell; it can also be understood as a process of charging the battery cell. After formation, it helps to form the SEI film in the battery cell.

[0054] In the embodiments of the present application, aging can refer to the process of standing the battery cell at room temperature or high temperature after formation. After the aging process, it helps to restructure the SEI, form a loose and porous film, which is beneficial to making the voltage of the battery cell more accurate and stable, and also beneficial to enabling the electrolyte to fully infiltrate the electrode plate.

[0055] The battery cell in the embodiments of the present application may refer to the smallest structural unit of a battery. Multiple battery cells may first form a battery module, and then the battery module forms a battery; multiple battery cells may also directly form a battery.

[0056] The battery cell in the embodiments of the present application refers to a secondary battery, that is, a battery cell capable of reversible charge and discharge.

[0057] [Battery cell]

[0058] The embodiments of the present application provide a battery cell, including a positive electrode tab.

[0059] Figure 1 It is a schematic structural diagram of the positive electrode tab of an embodiment of the present application. For example, as Figure 1 shown, the positive electrode tab 1 includes a positive electrode current collector 10 and a positive electrode film layer 11 provided on at least one side surface of the positive electrode current collector 10.

[0060] The positive electrode current collector 10 has two side surfaces opposite to each other along its own thickness direction. Among them, the positive electrode film layer 11 may be provided on one side surface of the positive electrode current collector 10, or may be provided on both side surfaces of the positive electrode current collector 10. As an example, as Figure 1 shown, the positive electrode film layer 11 is provided on both side surfaces of the positive electrode current collector 10.

[0061] The positive electrode film layer 11 includes a first metal oxide, a second metal oxide and a surfactant. Among them, the first metal oxide and the second metal oxide are different metal oxides.

[0062] The chemical formula of the first metal oxide satisfies: Li5MO4, where M includes one or more of Fe, Cr, V, and Mo.

[0063] The chemical formula of the second metal oxide satisfies: Li a N b O2, where a:b > 1, 1 < a ≤ 2, 0 < b ≤ 1, and N includes one or more of Cu, Co, Mg, Zn, Mn, Al, Ni, Zr, Ti, and Fe. Exemplarily, a may be 2, b may be 1; a may be 1.5, b may be 1; a may be 1.5, b may be 0.75.

[0064] The second metal oxide may be a material with a layered structure, where the layered structure refers to a lattice structure in layers. In the layered structure of the second metal oxide, the oxide of lithium occupies one layer, the metal oxide occupies one layer, and the excess lithium will occupy in the metal oxide layer.

[0065] As an example, the first metal oxide includes Li5FeO4, and the second metal oxide includes Li₂NiO₂.

[0066] During the charging process of a battery cell, the first metal oxide releases oxygen after lithium removal. For example, during the formation process of a battery cell, the first metal oxide releases oxygen after lithium removal. Although the oxygen can be extracted using a degassing device during the formation stage, some oxygen still dissolves in the electrolyte. During the aging stage after formation, the oxygen reacts with the electrolyte to produce gas. This not only leads to longer manufacturing time and higher costs for the battery cell, but also reduces the stability of the positive electrode film, the reliability of the battery cell, and the yield rate during later use.

[0067] Setting a first metal oxide and a second metal oxide in the positive electrode not only achieves lithium replenishment but also reduces gas production in the aging stage of the battery cell after formation. This can be explained by the following possible mechanisms: (1) During the charging process of the battery cell, lithium occupying the metal oxide layer in the second metal oxide is unstable and easily detaches. The detached lithium leaves vacancies, forming vacancy clusters that capture oxygen in the surface lattice structure, reducing the problem caused by oxygen generation from lithium delithiation in the first metal oxide; (2) Nickel ions in the second metal oxide can also react with oxygen dissolved in the electrolyte, thereby absorbing oxygen. It should be noted that the above mechanisms are only used to explain the reasons for reduced gas production in the battery cell and are not a limitation on the battery cell.

[0068] It should be noted that during the charging and discharging process of the battery, Li undergoes insertion / extraction and consumption, resulting in different molar contents of Li at different discharge states. In the examples of the first metal oxide, second metal oxide, and positive electrode active material in this application, the molar contents of Li refer to the initial state of the material, i.e., the state before feeding. As the positive electrode material is applied to the battery system, the molar contents of Li will change after charge-discharge cycles. Similarly, in the examples of the first metal oxide, second metal oxide, and positive electrode active material in this application, the molar contents of O are only theoretical values. Lattice oxygen release will cause changes in the molar contents of oxygen, resulting in fluctuations in the actual molar contents of O.

[0069] In the preparation process of a battery cell, the slurry of the positive electrode film includes the aforementioned first metal oxide and second metal oxide. Since the first and second metal oxides are alkaline, this increases the viscosity of the positive electrode slurry, leading to excessively high viscosity. In severe cases, the positive electrode slurry may even gel, making it difficult to coat the positive electrode current collector evenly (or impossible to coat). Such a positive electrode film is detrimental to the effective function of the first and second metal oxides, thus hindering the improvement of the battery cell's first-cycle charging capacity and reducing gas generation within the battery cell. Therefore, the positive electrode slurry also includes a surfactant. This surfactant reduces the viscosity of the positive electrode slurry, facilitating uniform coating and allowing the first and second metal oxides in the positive electrode film to effectively function, thereby improving the battery cell's first-cycle charging capacity and reducing gas generation within the battery cell.

[0070] In this embodiment, the first metal oxide and the second metal oxide can provide lithium ions, thereby replenishing the lithium ions consumed during the formation of the SEI film of the battery cell, which is beneficial to improving the first-cycle charging capacity of the battery cell. The positive electrode film also includes surfactants such as phosphate esters, acrylates, hydrogenated butadiene nitrile (HNDI) and polyvinylpyrrolidone (PVP), which can effectively reduce the viscosity of the positive electrode slurry, thus facilitating the uniform coating of the positive electrode slurry onto the positive electrode current collector. This allows the first and second metal oxides in the positive electrode film to effectively perform their functions, thereby improving the first-cycle charging capacity of the battery cell. Furthermore, the inclusion of both the first and second metal oxides in the positive electrode film can reduce the amount of gas generated by the battery cell during the aging stage after formation. Therefore, the technical solution of this embodiment can improve the first-cycle charging capacity of the battery cell while reducing gas generation within the battery cell.

[0071] In some embodiments, based on the total mass of the positive electrode film, the mass percentage of the surfactant P1 satisfies: 0%. <P1≤2%。

[0072] Specifically, P1 can be 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 2%, or a value within the range obtained by any combination of the above two values.

[0073] By setting the mass percentage of the surfactant within the above range, the viscosity of the cathode slurry can be kept within a suitable range, which is beneficial for the coating of the cathode slurry.

[0074] In some embodiments, based on the total mass of the positive electrode film, the mass percentage of the surfactant P1 satisfies: 0.2% ≤ P1 ≤ 1%. This allows the positive electrode slurry to have a more suitable viscosity, which further facilitates the coating of the positive electrode slurry.

[0075] In some embodiments, based on the total mass of the positive electrode film, the mass percentage P2 of the first metal oxide satisfies: 0%. <P2≤8%。

[0076] Specifically, P2 can be 0.5%, 0.8%, 1%, 1.5%, 2%, 3%, 4%, 4.5%, 5%, 6%, 7%, 7.5%, 8%, or a value within the range obtained by any combination of the above two values.

[0077] The first metal oxide has an appropriate content ratio in the positive electrode film layer, so that the battery cell has a high first charge capacity.

[0078] In some embodiments, based on the total mass of the positive electrode film, the mass percentage P2 of the first metal oxide satisfies: 0.8% ≤ P2 ≤ 4%. This is beneficial for further improving the first-cycle charging capacity of the battery cell.

[0079] In some embodiments, based on the total mass of the positive electrode film, the mass percentage P3 of the second metal oxide satisfies: 0%. <P3≤2%。

[0080] Specifically, P3 can be 0.2%, 0.5%, 1%, 1.2%, 1.5%, 1.8%, 2%, or a value within the range obtained by any combination of the above two values.

[0081] The second metal oxide has an appropriate content ratio in the positive electrode film layer, so that the battery cell has a high first charge capacity and a low gas production.

[0082] In some embodiments, based on the total mass of the positive electrode film, the mass percentage P3 of the second metal oxide satisfies: 0.2% ≤ P3 ≤ 1%. This is beneficial for further improving the first-cycle charging capacity of the battery cell and reducing the gas production of the battery cell during the aging stage.

[0083] In some embodiments, the surface of the second metal oxide is coated with oxide and / or carbon materials. This improves the conductivity of the second metal oxide, thereby increasing the first-cycle charging capacity of the battery cell.

[0084] In some embodiments, the oxide includes a metal element, which may be one or more selected from Ni, W, Cu, Mn, Al, Fe, Ti, Mo, Ce, Co, Cr, or V. Oxides containing the aforementioned metal elements exhibit good electrical conductivity, which is beneficial for improving the conductivity of the second metal oxide and thus for increasing the first-cycle charging capacity of the battery cell.

[0085] In some embodiments, the oxide includes Al2O3.

[0086] In some embodiments, based on the total mass of the second metal oxide and the oxide, the mass percentage of the oxide P5 satisfies: 0.1% ≤ P5 ≤ 10%.

[0087] Specifically, P5 can be 0.1%, 0.5%, 1%, 5%, 8%, 10%, or a value within the range obtained by any combination of the above two values.

[0088] By setting the mass content of the oxide within the above range, the conductivity of the second metal oxide and the amount of lithium ions released can be balanced, which is beneficial to improving the first-cycle charging capacity of the battery cell.

[0089] In some embodiments, based on the total mass of the second metal oxide and the oxide, the mass percentage of the oxide P5 satisfies: 0.5% ≤ P5 ≤ 5%.

[0090] In some embodiments, the positive electrode film layer further includes a positive electrode active material, wherein the volume average particle size Dv50 of the positive electrode active material satisfies: 0.5μm≤Dv50≤10μm.

[0091] Dv50 can refer to the particle size corresponding to 50% of the cumulative particle size distribution number of a sample, which means that 50% of the particles are smaller than Dv50.

[0092] The volume average particle size Dv50 of the positive electrode active material can be 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, or a value within the range obtained by any combination of the above two values.

[0093] When Dv50 ≥ 0.5 μm, the risk of agglomeration of positive electrode active material can be reduced, and the positive electrode active material, the first metal oxide and the second metal oxide can be mixed more uniformly, which is beneficial to reducing gas generation in the battery cell and improving the cycle performance of the battery cell. When Dv50 ≤ 10 μm, lithium ions have a suitable transport path, which is beneficial to the transport and diffusion of lithium ions, and the battery cell has a higher first charge capacity.

[0094] By setting the volume average particle size of the positive electrode active material within the above range, it is beneficial to improve the first charge capacity of the battery cell and its long-term cycle performance.

[0095] In some embodiments, the volume average particle size Dv50 of the positive electrode active material satisfies: 0.5 μm ≤ Dv50 ≤ 5 μm. This is beneficial for further improving the initial charge capacity of the battery cell and its long-term cycle performance.

[0096] In some embodiments, based on the total mass of the positive electrode film, the mass percentage P4 of the positive electrode active material satisfies: 80% ≤ P4 ≤ 95%.

[0097] Specifically, P4 can be 80%, 82%, 85%, 87%, 90%, 92%, 93%, 94%, 95%, or a value within the range obtained by any combination of the above two values.

[0098] By further setting P4 to meet the above range, the first metal oxide and the second metal oxide also have a more suitable mass ratio, which can play a better role in lithium replenishment, thereby reducing the consumption of active lithium in the positive electrode active material, and better maintaining the structural stability of the positive electrode active material during the lithium release process of the lithium replenishment agent, so that the battery cell has better cycle performance and cycle life.

[0099] In some embodiments, the positive electrode active material includes a lithium phosphate with an olivine structure, wherein the lithium phosphate with the olivine structure includes lithium iron phosphate. This results in a more stable positive electrode active material, which is beneficial for improving the long-term performance and lifespan of the battery cell.

[0100] Lithium-containing phosphates with an olivine structure may also include one or more of lithium manganese iron phosphate, lithium iron phosphate, and lithium titanate.

[0101] The positive electrode active material may include one or more of the following: a layered lithium-containing transition metal oxide and a spinel-structured lithium salt.

[0102] Layered lithium-containing transition metal oxides can include ternary materials such as lithium nickel cobalt manganese oxide and lithium-rich manganese-based materials. For example, ternary materials can be LiNi. 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2. For example, other metallic elements can be doped into ternary materials to improve certain properties. For instance, Zr, Al, and other materials can be doped.

[0103] Lithium-containing phosphates with an olivine structure may also include one or more of lithium manganese phosphate and lithium iron manganese phosphate.

[0104] Spinel-structured lithium salts can include lithium manganese oxide.

[0105] In some embodiments, the positive electrode active material further includes a carbon material coated on the surface of the lithium phosphate to form a carbon coating layer. This improves the conductivity of the positive electrode active material, thereby enhancing the initial charge capacity and long-term cycle performance of the battery cell.

[0106] In some embodiments, the thickness L of the carbon coating layer satisfies: 0 <L≤10nm。

[0107] Specifically, L can be 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, or a value within the range obtained by any combination of the above two values.

[0108] By setting the thickness of the carbon coating layer within the aforementioned range, it is beneficial to improve the initial charge capacity of the battery cell and its long-term cycle performance.

[0109] In some embodiments, the thickness L of the carbon coating layer satisfies: 1nm ≤ L ≤ 5nm. This is beneficial for further improving the initial charge capacity of the battery cell and its long-term cycle performance.

[0110] In some embodiments, the powder resistivity R of the positive electrode active material at 20 MPa satisfies: 2 Ω·cm ≤ R ≤ 50 Ω·cm.

[0111] Specifically, R can be 2Ω·cm, 5Ω·cm, 6Ω·cm, 7Ω·cm, 8Ω·cm, 9Ω·cm, 10Ω·cm, 11Ω·cm, 12Ω·cm, 13Ω·cm, 14Ω·cm, 15Ω·cm, 16Ω·cm, 17Ω·cm, 18Ω·cm, 19Ω·cm, 20Ω·cm, 25Ω·cm, 30Ω·cm, 35Ω·cm, 40Ω·cm, 45Ω·cm, 50Ω·cm, or a value within the range obtained by any combination of the above two values.

[0112] When R is set within the above range, the positive electrode active material has high conductivity, which is beneficial to improving the capacity of the battery cell and its long-term cycle performance.

[0113] In some embodiments, the powder resistivity R of the positive electrode active material at 20 MPa satisfies: 5 Ω·cm ≤ R1 ≤ 20 Ω·cm. This is beneficial for further improving the capacity of the battery cell and its long-term cycle performance.

[0114] In some embodiments, the battery cell is the battery cell before formation. After the formation process, lithium ions are released from the first metal oxide and the second metal oxide in the positive electrode of the battery cell, thereby increasing the first charge capacity of the battery cell.

[0115] In the embodiments of this application, after formation and aging processes, compared with battery cells that do not use the positive electrode sheet of this application, the battery cells of this application have higher first-cycle charging capacity and smaller volume expansion. After the aging process, the smaller volume expansion is beneficial to improving the yield of the battery cells and to making the battery cells more reliable in later use. The higher first-cycle charging capacity is beneficial to improving the cycle performance and service life of the battery cells.

[0116] As an example, when the first metal oxide includes Li5FeO4, it delithigates into LiFeO2; when the second metal oxide includes Li2NiO2, it delithigates into Li2O and NiO. After the battery cell undergoes formation, the presence of Li5FeO4 and Li2NiO2 in the positive electrode can be determined by detecting LiFeO2, Li2O, and NiO within the battery cell. Furthermore, the presence and size of the pores left on the positive electrode after the decomposition of the first and second metal oxides can also be used to determine the first and second metal oxides added to the positive electrode.

[0117] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. The battery cell can be a lithium-ion battery, a lithium-sulfur battery, a sodium-ion battery, a magnesium-ion battery, etc.

[0118] Figure 3 This is a schematic diagram of a battery cell according to an embodiment of this application. For example, such as... Figure 3 As shown, the battery cell 3 is a square battery cell. The battery cell 3 includes a housing 31, an end cap assembly 32, and an electrode assembly 33 disposed in the housing 31.

[0119] The electrode assembly 33 can be made from a positive electrode, a negative electrode, and a separator through a winding process or a stacking process.

[0120] End cap assembly 32 includes electrode terminals 322, such as Figure 3 As shown, the end cap assembly 32 includes two electrode terminals 322, one of which is a positive electrode terminal and the other is a negative electrode terminal.

[0121] The battery cell 3 also includes a current collector 34, which is used to connect the tab 331 of the electrode assembly 33 and the electrode terminal 322. For example, in the case where the electrode 1 in this embodiment is a positive electrode, one current collector 34 is used to connect the tab of the positive electrode and the positive electrode terminal, and another current collector 34 is used to connect the tab of the negative electrode and the negative electrode terminal.

[0122] In some embodiments, the battery cell 3 includes an electrode assembly 33, which includes an electrode assembly body 330 and a tab 331 extending from the electrode assembly body 330.

[0123] In some embodiments, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0124] [Positive electrode plate]

[0125] The positive electrode current collector 10 can be a metal foil or a composite positive electrode current collector. For example, the positive electrode current collector can be an aluminum foil.

[0126] The composite positive electrode current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite positive electrode current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0127] The positive electrode film layer 11 may also optionally include a binder. As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0128] The positive electrode film layer 11 may optionally include a conductive agent. The conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0129] [Negative electrode plate]

[0130] The negative electrode includes a negative current collector and a negative electrode film layer disposed on the negative current collector.

[0131] The negative electrode current collector can be a metal foil or a composite negative electrode current collector. The negative electrode current collector can be copper foil. Composite negative electrode current collectors can be formed by depositing metallic materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) onto a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0132] The negative electrode film layer includes a negative electrode active material. The negative electrode active material can be any negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0133] The negative electrode film layer may also optionally include a binder. As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0134] The negative electrode film may optionally include a conductive agent. The conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0135] [Electrolytes]

[0136] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0137] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0138] Electrolyte salts may include one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0139] Solvents may include one or more of the following: ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0140] The electrolyte may also optionally include a negative electrode film-forming additive, a positive electrode film-forming additive, and may also include a performance additive that can improve certain battery performance, such as a performance additive that improves the overcharge performance of the battery, improves the high-temperature or low-temperature performance of the battery, etc.

[0141] [Separator film]

[0142] The separator film is used to isolate the positive electrode plate and the negative electrode plate. There is no particular limitation on the type of the separator film in the embodiments of the present application, and any well-known porous structure separator film with good chemical stability and mechanical stability can be selected.

[0143] The material of the separator film can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0144] The positive electrode plate, the negative electrode plate, and the separator film can be made into an electrode assembly through a winding process or a stacking process.

[0145] [Preparation method of battery cell]

[0146] Figure 2 It is a schematic diagram of the preparation method of the battery cell according to an embodiment of the present application. As shown in combination with Figure 2 shown, the preparation method 200 of the electrode plate may include the following steps.

[0147] Step 210, providing a positive electrode plate to prepare a battery cell.

[0148] Among them, providing the positive electrode plate includes: mixing a first metal oxide, a second metal oxide, and a surfactant to obtain a slurry of the positive electrode film layer, wherein the chemical formula of the first metal oxide satisfies: Li5MO4, wherein M includes one or more of Fe, Cr, V, and Mo; the chemical formula of the second metal oxide satisfies: Li a N b O2, wherein, a:b>1, 1<a≤2, 0<b≤1, N includes one or more of Cu, Co, Mg, Zn, Mn, Al, Ni, Zr, Ti, and Fe; the surfactant includes: one or more of phosphate esters, acrylate esters, hydrogenated nitrile rubber, and polyvinylpyrrolidone; coating the slurry of the positive electrode film layer on at least one side surface of the current collector to prepare a positive electrode plate.

[0149] During the process of preparing the positive electrode plate, a positive electrode active material, a binder, a conductive agent, and a solvent can also be added, and after mixing, a slurry of the positive electrode film layer is obtained.​​As an example, a slurry for coating a positive electrode film layer is applied to both sides of the current collector to prepare a positive electrode sheet.

[0151] In some embodiments, after step 210, the positive electrode sheet, negative electrode sheet, and separator can be prepared into an electrode assembly by winding or stacking, and then the electrode assembly is placed into a housing to prepare a battery cell.

[0152] In the battery cell preparation method of this application embodiment, the slurry formed by mixing the first metal oxide, the second metal oxide, and the surfactant to form the positive electrode film layer is beneficial for uniform coating of the slurry. The prepared positive electrode not only provides better lithium replenishment and improves the first-cycle charging capacity of the battery cell, but also reduces gas generation in the aging stage after formation, thus reducing the amount of gas generated in the battery cell. In addition, this preparation method does not require sintering treatment of the first and second metal oxides, making the preparation method relatively simple and with low complexity.

[0153] [Battery]

[0154] This application provides a battery, including the battery cell described in the above embodiments. The battery cell can be a battery cell after formation and aging processes. Figure 4 This is a schematic diagram of a battery according to an embodiment of this application. Figure 4 As shown, battery 5 may include multiple battery cells (not shown in the figure).

[0155] Battery cells 3 can be directly assembled into battery 5, or they can be first assembled into battery modules, and then multiple battery modules can be assembled into battery 5.

[0156] [Electrical appliances]

[0157] This application provides an electrical device, including the battery described in the above embodiments.

[0158] In some embodiments, the electrical device includes an energy storage device or a heavy-duty truck. Energy storage devices and heavy-duty trucks have high requirements for the lifespan and long-term cycle performance of battery cells. Applying battery cells to the aforementioned electrical devices can improve the lifespan of the electrical devices.

[0159] Electrical devices can also be lighting devices, spacecraft, etc., and the embodiments of this application include, but are not limited to, these.

[0160] Figure 5 This is a schematic diagram of an electrical device according to an embodiment of this application. Figure 5 As shown, this application provides an electrical device, which is a heavy-duty truck 6. The battery in the heavy-duty truck 6 can be replaced by a battery swapping device to replace the battery with insufficient power with a fully charged battery.

[0161] Figure 6 This is a schematic diagram of an electrical device according to an embodiment of this application. Figure 6 As shown, this application provides an electrical device, which is an energy storage device 7, and the energy storage device 7 may include multiple batteries 5. The energy storage device 7 can be applied to a power storage station 2 to store and release electrical energy.

[0162] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0163] [Examples and Comparative Examples]

[0164] Example 1

[0165] (1) Preparation of positive electrode sheet

[0166] A mixture of the first metal oxide Li5FeO4 and the second metal oxide Li2NiO2, along with the positive electrode active material, is mixed at a mass ratio of 1:35 to obtain the positive electrode material. The positive electrode material, the binder polyvinylidene fluoride (PVDF), the conductive agent (carbon black), and the surfactant alkyl phosphate are mixed evenly and dissolved in the solvent N-methylpyrrolidone (NMP). After thorough stirring and mixing, a positive electrode slurry is prepared with a viscosity η of 8453 mPa·s. The positive electrode slurry is uniformly coated on two opposite surfaces of the positive electrode current collector aluminum foil, and then dried, cold-pressed, and slit to obtain the positive electrode sheet. The positive electrode active material is lithium iron phosphate and carbon black coated on the surface of lithium iron phosphate. The thickness L of the carbon coating layer formed by the carbon black is 3 nm. The volume average particle size Dv50 of the positive electrode active material is 1.5 μm. The mass percentage of the first metal oxide Li5FeO4 in the positive electrode film is 2.4%, the mass percentage of the second metal oxide Li2NiO2 in the positive electrode film is 0.6%, the mass percentage of the surfactant alkyl phosphate in the positive electrode film is 0.4%, and the powder resistivity R is 8.3 Ω·cm.

[0167] (2) Preparation of negative electrode sheet: The negative electrode active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR) and thickener sodium carboxymethyl cellulose (CMC-Na) are dissolved in deionized water at a mass ratio of 96:1.5:1.5:1.0 and mixed thoroughly to prepare a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector copper foil, and then dried, cold pressed and cut to obtain the negative electrode sheet.

[0168] (3) Separation membrane: A polyethylene membrane with a thickness of 13μm is used.

[0169] (4) Preparation of electrolyte: Ethyl carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte with a concentration of 1 mol / L of LiPF6.

[0170] (5) Preparation of lithium-ion battery: The above positive electrode sheet, separator and negative electrode sheet are stacked and wound in sequence to obtain electrode assembly; the electrode assembly is placed in outer packaging, the electrolyte prepared above is added, and after encapsulation, standing, formation and aging processes, a battery cell is obtained.

[0171] Examples 2-5

[0172] The difference between Examples 2-5 and Example 1 is that the mass percentage of the surfactant alkyl phosphate ester in the positive electrode film is different.

[0173] Examples 6-11

[0174] The difference between Examples 6-11 and Example 1 is that the volume average particle size Dv50 of the positive electrode active material is different.

[0175] Examples 12-14

[0176] The difference between Examples 12-14 and Example 1 is that the thickness of the carbon coating layer on the surface of lithium iron phosphate in the positive electrode active material is different.

[0177] Examples 15-19

[0178] The difference between Examples 15-19 and Example 1 is that the mass percentage of the mixed material of the first metal oxide Li5FeO4 and the second metal oxide Li2NiO2 in the positive electrode film layer is different.

[0179] In embodiments 1-19 of this application, the ratio of the mass percentage of the first metal oxide Li5FeO4 in the positive electrode film and the mass percentage of the second metal oxide Li2NiO2 in the positive electrode film is fixed at 4:1.

[0180] Comparative Example 1

[0181] The difference between Comparative Example 1 and Example 1 is that no surfactant alkyl phosphate was added to the positive electrode slurry, and the positive electrode film layer of the positive electrode sheet does not contain surfactant alkyl phosphate.

[0182] Comparative Example 2

[0183] The difference between Comparative Example 2 and Example 1 is that no second metal oxide was added to the positive electrode slurry, and the positive electrode film layer of the positive electrode sheet does not contain a second metal oxide.

[0184] The product parameters of Examples 1-19 and Comparative Examples 1-2 are detailed in Table 1 below, and the performance parameters of Examples 1-19 and Comparative Examples 1-2 are detailed in Table 2 below.

[0185] Table 1 Product parameters of Examples 1-19 and Comparative Examples 1-2

[0186]

[0187]

[0188] In Table 1, P1 represents the mass percentage of surfactant based on the total mass of the positive electrode film; P2 represents the mass percentage of the first metal oxide based on the total mass of the positive electrode film; P3 represents the mass percentage of the second metal oxide based on the total mass of the positive electrode film; Dv50 represents the volume average particle size of the positive electrode active material; L represents the thickness of the carbon coating layer covering the positive electrode active material; R represents the powder resistivity of the positive electrode active material at 20 MPa; and η represents the viscosity of the slurry of the positive electrode film.

[0189] Table 2 Performance parameters of Examples 1-19 and Comparative Examples 1-2

[0190]

[0191]

[0192] The following is a brief description of the testing methods for the physicochemical and performance parameters involved in the embodiments of this application. It should be understood that the following testing methods are only examples, and other testing methods known in the art can also be used for testing.

[0193] 1. Measurement of the first charging capacity

[0194] Testing of individual battery cells: Under a voltage range of 2.5V to 4.25V, charge at a rate of 0.3C to 3.65V, then charge at a constant voltage until the current is ≤0.05mA, and let stand for 2 minutes; then charge at 0.05C to 4.2V. The charging capacity at this point is recorded as C2. Divide the charging capacity C2 by the total mass of the first metal oxide, the second metal oxide, and the positive electrode active material to obtain the specific capacity Q2 of the first charge cycle.

[0195] 2. Testing of gas production during aging

[0196] After formation, the battery cells were left to stand at 45°C for 48 hours, and the gas production during aging was measured. The aging gas production can be obtained using infrared spectroscopy or water displacement methods. Specifically, the volume before and after standing can be measured using the water displacement method, and the gas production is calculated based on the volume change. The aging gas production is ΔM / (ρ 液 ×Q), where ΔM is the mass of the drained water, ρ 液 Let Q be the density of the liquid, and Q be the capacity of a single battery cell.

[0197] 3. Cyclic capacity retention test

[0198] Within a voltage range of 2.5V to 4.2V, charge at a 0.1C rate to the limit voltage, then charge at a constant voltage until the current is ≤0.05mA. Let it rest for 2 minutes, then discharge at a 0.1C rate to 2.5V. The charged capacity at this point is the initial capacity Q1. After the nth cycle, the capacity measured using the same process is Qn; the cycle capacity retention rate = (1-(Qn / Q1)^(1 / n))×100%. Where Qn is the battery capacity after the nth cycle, Q1 is the initial battery capacity, and n is the number of cycles.

[0199] 4. Identification of the first metal oxide and the second metal oxide

[0200] As an example, the positive electrode sheet of a single battery cell before formation is used as a sample. A scanning electron microscope is used to observe the positive electrode sheet, and the particle size can be used to distinguish the first metal oxide, the second metal oxide, and the positive electrode active material. Then, the positive electrode film layer can be scraped off, and the scraped material is added to aqua regia and digested under mechanical stirring for 30 minutes. The digested solution is then added to an ICAP7400 spectrometer to quantitatively analyze the mass fraction of each element in the material. The mass content of the first and second metal oxides is calculated based on the mass fraction of each element.

[0201] As another example, the specific types and mass content of the first metal oxide and the second metal oxide are determined by the raw materials added in the preparation method.

[0202] 5. Test of volume average particle size

[0203] The volume average particle size Dv50 can be determined by measuring the raw materials used to prepare the positive electrode sheet. For example, it can be determined by laser particle size analyzer according to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method.

[0204] In addition, the positive electrode sheet can be observed using a scanning electron microscope. A specific area can be selected, and the volume average particle size can be calculated based on the size and number of particles observed in that area.

[0205] 6. Testing of powder resistivity

[0206] Weigh an appropriate amount of positive electrode active material powder, and then use a powder resistivity tester (ST2722 digital four-probe instrument, manufactured by Suzhou Jingge Electronics Co., Ltd.) to determine the powder resistivity of the sample according to GB / T 30835-2014 "Carbon composite lithium iron phosphate supplementary lithium material for lithium-ion batteries" with a test pressure of 20MPa.

[0207] As shown in Examples 1-19 and Comparative Example 1, adding a surfactant to the slurry of the positive electrode film significantly reduces the viscosity of the positive electrode slurry (in Comparative Example 1, the slurry viscosity was too high to be measured, and the slurry could not be coated).

[0208] As shown in Examples 1-19 and Comparative Example 2, compared to adding only the first metal oxide, adding both the first metal oxide and the second metal oxide can reduce gas generation in the aging stage after formation of the battery cell, increase the first charge capacity of the battery cell, thereby compensating for the irreversible lithium loss of the battery cell and improving the long-term cycle performance and service life of the battery cell.

[0209] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, include: A positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode film layer, the positive electrode film layer being disposed on at least one side surface of the positive current collector, the positive electrode film layer comprising a first metal oxide, a second metal oxide, and a surfactant; The chemical formula of the first metal oxide is: Li5MO4, wherein M includes one or more of Fe, Cr, V, and Mo; The chemical formula of the second metal oxide satisfies: Li a N b O2, where a:b > 1, 1 < a ≤ 2, 0 < b ≤ 1, and N includes one or more of Cu, Co, Mg, Zn, Mn, Al, Ni, Zr, Ti, and Fe; The surfactants include one or more of the following: phosphate esters, acrylates, hydrogenated butyronitrile compounds, and polyvinylpyrrolidones; Based on the total mass of the positive electrode film, the mass percentage content P2 of the first metal oxide satisfies: 0.4% ≤ P2 ≤ 4%, and based on the total mass of the positive electrode film, the mass percentage content P3 of the second metal oxide satisfies: 0.1% ≤ P3 ≤ 1%, and P2 and P3 satisfy: |P2-P3| ≤ 3%; The positive electrode film layer also includes a positive electrode active material, and the volume average particle size Dv50 of the positive electrode active material satisfies: 0.5μm≤Dv50≤10μm.

2. The battery cell according to claim 1, characterized in that, Based on the total mass of the positive electrode film, the mass percentage P1 of the surfactant satisfies: 0%. <P1≤2%。 3. The battery cell according to claim 2, characterized in that, 0.2%≤P1≤1%。 4. The battery cell according to claim 1, characterized in that, The surface of the second metal oxide is coated with oxide and / or carbon materials.

5. The battery cell according to claim 4, characterized in that, The oxide includes a metallic element, which includes one or more of Ni, W, Cu, Mn, Al, Fe, Ti, Mo, Ce, Co, Cr, or V.

6. The battery cell according to claim 4, characterized in that, The oxide includes Al2O3.

7. The battery cell according to claim 4, characterized in that, Based on the total mass of the second metal oxide and the oxide, the mass percentage P5 of the oxide satisfies: 0.1% ≤ P5 ≤ 10%.

8. The battery cell according to claim 7, characterized in that, 0.5%≤P5≤5%。 9. The battery cell according to any one of claims 1 to 8, characterized in that, 0.5μm≤Dv50≤5μm.

10. The battery cell according to any one of claims 1 to 8, characterized in that, Based on the total mass of the positive electrode film, the mass percentage P4 of the positive electrode active material satisfies: 80% ≤ P4 ≤ 95%.

11. The battery cell according to any one of claims 1 to 8, characterized in that, The positive electrode active material includes: a lithium phosphate with an olivine structure, wherein the lithium phosphate with an olivine structure includes lithium iron phosphate.

12. The battery cell according to claim 11, characterized in that, The positive electrode active material also includes carbon material, which coats the surface of the lithium phosphate to form a carbon coating layer.

13. The battery cell according to claim 12, characterized in that, The thickness L of the carbon coating layer satisfies: 0 <L≤10nm。 14. The battery cell according to claim 13, characterized in that, 1nm≤L≤5nm.

15. The battery cell according to any one of claims 1 to 8, characterized in that, The powder resistivity R of the positive electrode active material at 20 MPa satisfies: 2 Ω·cm ≤ R ≤ 50 Ω·cm.

16. The battery cell according to claim 15, characterized in that, 5Ω·cm≤R≤20Ω·cm.

17. The battery cell according to any one of claims 1 to 8, characterized in that, The battery cell is the battery cell before formation.

18. A method for preparing a single battery cell, characterized in that, include: A positive electrode sheet is provided to prepare the battery cell; The positive electrode sheet provided includes: Mix a first metal oxide, a second metal oxide, a cathode active material, and a surfactant to obtain a slurry for a cathode film layer. Among them, the chemical formula of the first metal oxide satisfies: Li5MO4, where M includes one or more of Fe, Cr, V, and Mo. The chemical formula of the second metal oxide satisfies: Li a N b O2, where a:b > 1, 1 < a ≤ 2, 0 < b ≤ 1, N includes one or more of Cu, Co, Mg, Zn, Mn, Al, Ni, Zr, and Ti, the surfactant includes one or more of phosphate esters, acrylate esters, hydrogenated nitrile butadiene rubbers, and polyvinylpyrrolidones, and the volume average particle size Dv50 of the cathode active material satisfies: 0.5 μm ≤ Dv50 ≤ 10 μm; The slurry of the positive electrode film layer is coated on at least one side of the surface of the current collector to provide the positive electrode sheet; Based on the total mass of the positive electrode film, the mass percentage content P2 of the first metal oxide satisfies: 0.4%≤P2≤4%, and based on the total mass of the positive electrode film, the mass percentage content P3 of the second metal oxide satisfies: 0.1%≤P3≤1%, and P2 and P3 satisfy: |P2-P3|≤3%.

19. The preparation method according to claim 18, characterized in that, The viscosity η of the slurry satisfies: 5000mPa·S<η≤30000mPa·S.

20. The preparation method according to claim 19, characterized in that, 7000mPa·S<η≤10000mPa·S.

21. An electrical appliance, characterized in that, include: The battery cell according to claim 1, and / or the battery cell obtained by the preparation method according to any one of claims 18 to 20.

22. The electrical appliance according to claim 21, characterized in that, The electrical equipment includes energy storage devices or heavy-duty trucks.

Images