Battery monomer, preparation method thereof and power utilization device

Abstract

The invention discloses a battery monomer, a preparation method thereof and an electric device. The battery monomer comprises a positive electrode plate, the positive electrode plate 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; the chemical formula of the first metal oxide meets Li5MO4, and M comprises one or more of Fe, Cr, V and Mo; the chemical formula of the second metal oxide meets LiaNbO2, and a is bgt; 1, 1lt; a < = 2, 0lt; b is less than or equal to 1, and N comprises one or more of Cu, Co, Mg, Zn, Mn, Al, Ni, Zr, Ti and Fe; the surfactant comprises one or more of phosphate ester, acrylic ester, hydrogenated butyronitrile and polyvinylpyrrolidone, the first-circle charging capacity of the battery monomer can be improved, and gas production in the battery monomer can be reduced.

Description

Technical Field

[0001] The present 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 more and more 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 an 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 a technical problem to be solved urgently. Summary of the Invention

[0004] The present 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, the present application provides a battery cell, a preparation method thereof, and an electrical device.

[0006] In a first aspect, a battery cell is provided, including a positive electrode tab, the positive electrode tab 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: Li 5 MO 4 , 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 O 2 , 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 rubbers, and polyvinylpyrrolidones.

[0007] In the embodiment of the present application, the first metal oxide and the second metal oxide can provide lithium ions, thereby replenishing the lithium ions consumed in the formation process of the SEI film of the battery cell, which is beneficial to improve the first-cycle charging capacity of the battery cell. The positive electrode film layer also includes surfactants such as phosphates, acrylates, hydrogenated nitrile, and polyvinyl pyrrolidone, which can effectively reduce the viscosity of the positive electrode slurry, thereby facilitating the uniform coating of the positive electrode slurry on the positive electrode current collector, and facilitating the first metal oxide and the second metal oxide in the positive electrode film layer of the positive electrode sheet to effectively play their role, so as to improve the first-cycle charging capacity of the battery cell. Moreover, the positive electrode film layer includes the above-mentioned first metal oxide and second metal oxide at the same time, which can reduce the gas production of the battery cell in the aging stage after formation. Therefore, the technical solution of the embodiment of the present application can reduce the gas production in the battery cell while increasing the first-cycle charging capacity of the battery cell.

[0008] In a possible implementation, based on the total mass of the positive electrode film layer, the mass percentage content P of the surfactant is 1 Satisfied: 0% <P 1 ≤2%. In this way, in the process of preparing the battery monomer, the viscosity of the positive electrode slurry can be kept within an appropriate range, which is beneficial to the coating of the positive electrode slurry.

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

[0010] In a possible implementation, based on the total mass of the positive electrode film layer, the mass percentage content P of the first metal oxide is 2 Satisfied: 0% <P 2 ≤8%. The first metal oxide has an appropriate content ratio in the positive electrode film layer, so that the battery cell has a higher first cycle charging capacity.

[0011] In one possible implementation, 0.8% ≤ P 2 ≤4%. This is conducive to further improving the first cycle charging capacity of the battery cell.

[0012] In a possible implementation, based on the total mass of the positive electrode film layer, the mass percentage content P of the second metal oxide is 3 Satisfied: 0% <P 3 ≤2%. The second metal oxide has a suitable content ratio in the positive electrode film layer, so that the battery cell has a higher first cycle charging capacity and less gas production.

[0013] In one possible implementation, 0.2% ≤ P 3≤1%. This is conducive to further improving the first cycle charging capacity of the battery cell and reducing the gas production of the battery cell during the aging stage.

[0014] In a possible implementation, the surface of the second metal oxide is coated with oxide and / or carbon material, which is helpful to improve the conductivity of the second metal oxide, and further helps to improve the first cycle charging capacity of the battery cell.

[0015] In a possible implementation, the oxide includes a metal element, and the metal element includes one or more of Ni, W, Cu, Mn, Al, Fe, Ti, Mo, Ce, Co, Cr or V. The oxide including the above metal elements has good electrical conductivity, which is beneficial to improving the conductivity of the second metal oxide, and further beneficial to improving the first cycle charging capacity of the battery cell.

[0016] In a possible implementation, the oxide includes Al 2 O 3 .

[0017] In a possible implementation, based on the total mass of the second metal oxide and the oxide, the mass percentage content P of the oxide is 5 Satisfy: 0.1% ≤ P 5 By setting the mass content of the oxide within the above range, the conductivity of the second metal oxide and the amount of released lithium ions can be taken into account, which is beneficial to improving the first cycle charging capacity of the battery cell.

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

[0019] In a possible implementation, the positive electrode film layer further includes a positive electrode active material, and 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 first cycle charging capacity and long-term cycle performance of the battery cell.

[0020] In a possible implementation, 0.5 μm ≤ Dv50 ≤ 5 μm. This is beneficial to further improve the first cycle charging capacity and long-term cycle performance of the battery cell.

[0021] In a possible implementation, based on the total mass of the positive electrode film layer, the mass percentage content P of the positive electrode active material is 4 Satisfaction: 80% ≤ P 4 ≤95%. In this way, the battery cell can have a higher first cycle charging capacity, higher capacity and better long-term cycle performance.

[0022] In a possible implementation, the positive electrode active material includes: lithium-containing phosphate in an olivine structure, and the lithium-containing phosphate in the olivine structure includes lithium iron phosphate. In this way, the stability of the positive electrode active material is stronger, which is beneficial to improving the long-term use performance and the lifespan of the battery cell.

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

[0028] In a possible implementation, the battery cell is a battery cell before formation. After the formation process, lithium ions are removed from the first metal oxide and the second metal oxide in the positive electrode plate of the battery cell, 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: Li 5 MO 4 , wherein M includes one or more of Fe, Cr, V, and 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 rubbers, polyvinylpyrrolidones; the slurry of the positive electrode film layer is coated on at least one side surface of the current collector to provide the positive electrode plate.

[0030] Mixing the first metal oxide, the second metal oxide and the surfactant to form the slurry of the positive electrode film layer is conducive to the uniform coating of the slurry. The preparation method of the above positive electrode plate is relatively simple and the preparation complexity is relatively low; and after the prepared positive electrode plate is applied to the battery cell, the battery cell has a relatively high first-cycle charging capacity and a relatively small gas generation amount.

[0031] In a possible implementation manner, the viscosity η of the slurry satisfies: 5000 mPa·S < η ≤ 30000 mPa·S. Setting the viscosity of the slurry of the positive electrode film layer within the above range is conducive to the uniform coating of the positive electrode slurry, and is conducive to the first metal oxide and the second metal oxide in the positive electrode film layer of the positive electrode plate to effectively play their roles, so as to improve the first-cycle charging capacity of the battery cell and reduce the gas generation in the battery cell.

[0032] In a possible implementation manner, 7000 mPa·S < η ≤ 10000 mPa·S. In this way, it can further be conducive to the uniform coating of the positive electrode slurry, thereby being conducive to further improving the first-cycle charging capacity of the battery cell and further reducing the gas generation in the battery cell.

[0033] In a third aspect, an electrical device is provided, including the battery cell in the first aspect and any one of its possible implementation manners, and / or the battery cell obtained by the preparation method in the second aspect.

[0034] In a possible implementation manner, the electrical device includes an energy storage device or a heavy truck. The energy storage device and the heavy truck have relatively high requirements for the service life and long-term cycling performance of the battery cell. Applying the battery cell to the above electrical device can improve the life of the electrical device. Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced below. Obviously, the following described drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the drawings.

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

[0037] Figure 2 A schematic diagram of a battery cell according to an embodiment of the present application;

[0038] Figure 3 A schematic diagram of a method for preparing a battery cell according to an embodiment of the present application;

[0039] Figure 4 A schematic diagram of a battery according to an embodiment of the present application;

[0040] Figure 5 A schematic diagram of an electrical device according to an embodiment of the present application;

[0041] Figure 6 FIG. 1 is a schematic diagram of an electrical device according to an embodiment of the present application. DETAILED DESCRIPTION

[0042] The positive electrode sheet and its preparation method, and the implementation mode of the battery cell of the present application are described in detail with appropriate reference to the drawings, but there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0043] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0045] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0046] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0047] The development of battery technology must consider many design factors at the same time, such as energy density, cycle life, discharge capacity, charge and discharge rate, reliability, first-cycle charging capacity, etc. In the process of forming the SEI film of the battery cell, about 10% of the active lithium is consumed, and the consumption of active lithium is not conducive to improving the capacity of the battery cell. Adding certain lithium supplement materials to the battery cell can supplement the active lithium. For example, adding lithium-rich metal oxides to the positive electrode plate to supplement the active lithium, thereby improving the first-cycle charging capacity of the battery cell. However, during the charging process, some lithium-rich metal oxides with high oxygen content can contain more lithium ions due to the negative electronegativity of oxygen. While de-lithiation, more active lithium ions will be released to supplement more capacity, but more oxygen will also be released, which will destroy the structural stability of the positive electrode film layer, and oxygen will dissolve in the electrolyte and react with the electrolyte in the subsequent charging process (such as the aging stage after formation), which will lead to more obvious gas production in the battery cell, which is not conducive to the improvement of the performance of the battery cell. In addition, lithium-rich metal oxide materials are generally alkaline, which will increase the instability of the positive electrode film slurry, and in severe cases, will cause gelation, resulting in uneven or impossible coating of the positive electrode film slurry, making it difficult to prepare a battery cell with less gas production and higher first-cycle charging capacity. Therefore, how to provide a battery cell with less gas production and higher first-cycle charging capacity is a technical problem that needs to be solved urgently.

[0048] In view of this, the present application provides a battery cell, comprising: a positive electrode plate; the positive electrode plate 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, the positive electrode film layer comprises a first metal oxide, a second metal oxide and a surfactant; the chemical formula of the first metal oxide satisfies: Li 5MO 4 , 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 O 2 , 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 rubbers, and polyvinylpyrrolidones. The combination of the first metal oxide and the second metal oxide is beneficial to improving the first-cycle charging capacity of the battery cell while reducing the gas generation of the battery cell during the aging stage, and thus is 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, thereby facilitating the uniform coating of the positive electrode slurry on the positive electrode current collector, facilitating the formation of the positive electrode film layer of the positive electrode sheet, enabling the first metal oxide and the second metal oxide in the positive electrode film layer to effectively play their roles, so as to improve the first-cycle charging capacity of the battery cell and reduce the 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 sheet, thereby making up 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, and this surfactant can reduce the viscosity of the slurry, which is beneficial to the 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; while 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, and 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, and going through formation is helpful for the formation of the SEI film in the battery cell.

[0054] In the embodiments of the present application, aging may refer to the process of standing the battery cell at room temperature or high temperature after formation. Through 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 sheet.

[0055] The battery cell in the embodiments of the present application may refer to the smallest structural unit of the battery. Multiple battery cells can first form a battery module, and then the battery modules form a battery; multiple battery cells can 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 that can be reversibly charged and discharged.

[0057] [Battery cell]

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

[0059] Figure 1 It is a schematic structural diagram of the positive electrode sheet of an embodiment of the present application. For example, as Figure 1 shown, the positive electrode sheet 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 can be provided on one side surface of the positive electrode current collector 10, or can 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: Li 5 MO 4 , 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 O 2 , 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 can be 2, b can be 1; a can be 1.5, b can be 1; a can be 1.5, b can be 0.75.

[0064] The second metal oxide may be a layered material, wherein the layered structure refers to a layered lattice structure. In the layered structure of the second metal oxide, lithium oxide occupies one layer, metal oxide occupies one layer, and excess lithium occupies the metal oxide layer.

[0065] As an example, the first metal oxide includes Li 5 FeO 4 , the second metal oxide includes Li 2 NiO 2 .

[0066] During the charging process of the battery cell, the first metal oxide releases oxygen after de-lithiation. For example, during the formation process of the battery cell, the first metal oxide de-lithiations and releases oxygen. Although the oxygen can be extracted by the exhaust device during the formation stage, some oxygen still dissolves in the electrolyte; during the aging stage after formation, oxygen reacts with the electrolyte to produce gas, which not only leads to a longer process time and higher cost for the battery cell, but also leads to a decrease in the stability of the positive electrode film layer during the later use of the battery cell, a decrease in the reliability of the battery cell, and a decrease in the yield rate of the battery cell.

[0067] The first metal oxide and the second metal oxide are arranged in the positive electrode plate, which can not only achieve the lithium supplement effect, but also reduce the gas production of the battery cell in the aging stage after formation. Among them, it can be explained by the following possible mechanisms: (1) During the charging process of the battery cell, in the second metal oxide, the lithium occupied in the metal oxide layer is unstable and easy to be released. After the lithium occupied in the metal oxide layer is released, vacancies will be left to form vacancy clusters, thereby capturing oxygen in the surface lattice structure, reducing the problem caused by the first metal oxide removing lithium to produce oxygen; (2) The nickel ions in the second metal oxide can also react with the oxygen dissolved in the electrolyte, thereby absorbing oxygen. It should be noted that the above mechanism is only used to explain the reasons for the reduction of gas production in the battery cell, and it is not a limitation on the battery cell.

[0068] It should be noted that the battery will be accompanied by Li deintercalation and consumption during the charging and discharging process, and the molar content of Li is different when the battery is discharged to different states. In the enumeration of the first metal oxide, the second metal oxide, and the positive electrode active material in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode material is used in the battery system, and the molar content of Li will change after the charge and discharge cycle. In the enumeration of the first metal oxide, the second metal oxide, and the positive electrode active material in this application, the molar content of O is only a theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0069] In the process of preparing the battery cell, the slurry of the positive electrode film layer includes the above-mentioned first metal oxide and second metal oxide. Since the first metal oxide and the second metal oxide are alkaline, the viscosity of the positive electrode slurry will increase, making the viscosity of the positive electrode slurry too high. In severe cases, the positive electrode slurry will be in a gel state, making it difficult to coat the positive electrode slurry on the positive electrode current collector, and it cannot be coated evenly (or even cannot be coated). The positive electrode film layer formed in this way is not conducive to the first metal oxide and the second metal oxide to effectively play their roles, thereby not conducive to improving the first cycle charging capacity of the battery cell and reducing the gas production in the battery cell. Therefore, the positive electrode slurry also includes a surfactant, which can reduce the viscosity of the positive electrode slurry, which is conducive to the uniform coating of the positive electrode slurry, thereby facilitating 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 and reduce the gas production in the battery cell.

[0070] In the embodiment of the present application, the first metal oxide and the second metal oxide can provide lithium ions, thereby replenishing the lithium ions consumed in the formation process of the SEI film of the battery cell, which is beneficial to improve the first-cycle charging capacity of the battery cell. The positive electrode film layer also includes surfactants such as phosphates, acrylates, hydrogenated nitrile, and polyvinyl pyrrolidone, which can effectively reduce the viscosity of the positive electrode slurry, thereby facilitating the uniform coating of the positive electrode slurry on the positive electrode current collector, and facilitating the first metal oxide and the second metal oxide in the positive electrode film layer of the positive electrode sheet to effectively play their role, so as to improve the first-cycle charging capacity of the battery cell. Moreover, the positive electrode film layer includes the above-mentioned first metal oxide and second metal oxide at the same time, which can reduce the gas production of the battery cell in the aging stage after formation. Therefore, the technical solution of the embodiment of the present application can reduce the gas production in the battery cell while increasing the first-cycle charging capacity of the battery cell.

[0071] In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage content P of the surfactant is 1 Satisfied: 0% <P 1 ≤2%.

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

[0073] By setting the mass percentage of the surfactant within the above range, the viscosity of the positive electrode slurry can be within an appropriate range, which is beneficial to the coating of the positive electrode slurry.

[0074] In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage content P of the surfactant is 1Satisfy: 0.2% ≤ P 1 ≤1%. In this way, the positive electrode slurry can have a more suitable viscosity, which is further beneficial to the coating of the positive electrode slurry.

[0075] In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage content P of the first metal oxide is 2 Satisfied: 0% <P 2 ≤8%.

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

[0077] The first metal oxide has a suitable content ratio in the positive electrode film layer, so that the battery cell has a higher first-cycle charging capacity.

[0078] In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage content P of the first metal oxide is 2 Satisfy: 0.8% ≤ P 2 ≤4%. This is conducive to 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 layer, the mass percentage content P of the second metal oxide is 3 Satisfied: 0% <P 3 ≤2%.

[0080] Specifically, P 3 It can be 0.2%, 0.5%, 1%, 1.2%, 1.5%, 1.8%, 2%, or a value within the range obtained by combining any two of the above values.

[0081] The second metal oxide has a suitable content ratio in the positive electrode film layer, so that the battery cell has a higher first-cycle charging capacity and less gas production.

[0082] In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage content P of the second metal oxide is 3 Satisfy: 0.2% ≤ P 3 ≤1%. This is conducive to 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 material, which is helpful to improve the conductivity of the second metal oxide, and further helps to improve the first cycle charging capacity of the battery cell.

[0084] In some embodiments, the oxide includes a metal element, and the metal element includes one or more of Ni, W, Cu, Mn, Al, Fe, Ti, Mo, Ce, Co, Cr or V. The oxide including the above metal elements has good electrical conductivity, which is beneficial to improving the conductivity of the second metal oxide, and further beneficial to improving the first cycle charging capacity of the battery cell.

[0085] In some embodiments, the oxide includes Al 2 O 3 .

[0086] In some embodiments, based on the total mass of the second metal oxide and the oxide, the mass percentage of the oxide is P 5 Satisfy: 0.1% ≤ P 5 ≤10%.

[0087] Specifically, P 5 It can be 0.1%, 0.5%, 1%, 5%, 8%, 10%, or a value within the range obtained by combining any two of the above 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 released lithium ions can be taken into account, 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 is P 5 Satisfy: 0.5% ≤ P 5 ≤5%.

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

[0091] Dv50 can refer to the particle size corresponding to when the cumulative particle size volume distribution number of a sample reaches 50%, or it can refer to the particle size smaller than it accounting for 50%.

[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 combining any two of the above values.

[0093] When Dv50≥0.5μm, the risk of agglomeration of the 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 evenly, which is beneficial to reduce gas production in the battery cell and improve the cycle performance of the battery cell; when Dv50≤10μm, lithium ions have a suitable transmission path, which is beneficial to the transmission and diffusion of lithium ions, and the battery cell has a higher first-cycle charging 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 cycle charging capacity and long-term cycle performance of the battery cell.

[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 to further improve the first cycle charging capacity and long-term cycle performance of the battery cell.

[0096] In some embodiments, based on the total mass of the positive electrode film layer, the mass percentage content P of the positive electrode active material is 4 Satisfaction: 80% ≤ P 4 ≤95%.

[0097] Specifically, P 4 It can be 80%, 82%, 85%, 87%, 90%, 92%, 93%, 94%, 95%, or any value within the range obtained by combining any two of the above values.

[0098] By further setting P 4 When the above range is met, the first metal oxide and the second metal oxide also have a relatively suitable mass ratio, which can achieve a better lithium replenishment effect, 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 process of lithium release by the lithium replenisher, so that the battery cell has better cycle performance and cycle life.

[0099] In some embodiments, the positive electrode active material includes: an olivine-structured lithium-containing phosphate, and the olivine-structured lithium-containing phosphate includes lithium iron phosphate. In this way, the positive electrode active material is more stable, which is conducive to improving the long-term performance and life of the battery cell.

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

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

[0102] The layered structure of lithium-containing transition metal oxides may include ternary materials such as lithium nickel cobalt manganese oxide, lithium-rich manganese-based materials, etc. For example, the ternary material may be LiNi 0.8 Co 0.1 Mn 0.1 O 2 、LiNi 0.6 Co 0.2 Mn 0.2 O 2 For another example, other metal elements may be doped into the ternary material to improve certain properties of the ternary material. For example, materials such as Zr and Al may be doped.

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

[0104] The spinel-structured lithium salt may include lithium manganate.

[0105] In some embodiments, the positive electrode active material further includes a carbon material, and the carbon material is coated on the surface of the lithium phosphate to form a carbon coating layer. This is beneficial to improving the conductivity of the positive electrode active material, and further to improving the first cycle charging capacity and long-term cycle performance of the battery cell.

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

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

[0108] 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 cycle performance of the battery cell.

[0109] In some embodiments, the thickness L of the carbon coating layer satisfies: 1 nm ≤ L ≤ 5 nm. This is beneficial to further improve the first cycle charging capacity and long-term cycle performance of the battery cell.

[0110] In some embodiments, the powder resistivity R of the positive electrode active material at 20 MPa satisfies: 2Ω·cm≤R≤50Ω·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 its value is within the range obtained by combining any two of the above values.

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

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

[0114] In some embodiments, the battery cell is a battery cell before formation. After the formation process, the first metal oxide and the second metal oxide in the positive electrode plate of the battery cell release lithium ions, thereby increasing the first cycle charging capacity of the battery cell.

[0115] In the embodiment of the present application, after the formation and aging processes, the battery cell of the embodiment of the present application has a higher first-cycle charging capacity and a smaller volume expansion compared to the battery cell that does not adopt the positive electrode plate of the embodiment of the present application; after the aging process, the smaller volume expansion is beneficial to improving the yield rate of the battery cell and is beneficial to making the battery cell have higher reliability during later use; the higher first-cycle charging capacity is beneficial to improving the cycle performance and service life of the battery cell.

[0116] As an example, in the case where the first metal oxide includes Li 5 FeO 4 In the case of LiFeO 2 The second metal oxide includes Li 2 NiO 2 In the case of Li 2 O and NiO. After the battery cell is formed, the LiFeO 2 , Li 2 O, NiO to determine the positive electrode sheet including Li 5 FeO 4 and Li 2 NiO 2In addition, the first metal oxide and the second metal oxide added to the positive electrode sheet can be determined by observing the holes left on the positive electrode sheet after the first metal oxide and the second metal oxide are decomposed and the size of the holes.

[0117] The embodiment of the present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square or any other shape. The battery cell may be a lithium-ion battery, a lithium-sulfur battery, a sodium-ion battery, a magnesium-ion battery, etc.

[0118] Figure 3 Schematic diagram of a battery cell according to an embodiment of the present application. Figure 3 As shown, the battery cell 3 is a square battery cell and includes a housing 31 , an end cap assembly 32 and an electrode assembly 33 disposed in the housing 31 .

[0119] The electrode assembly 33 may be made of a positive electrode sheet, a negative electrode sheet and a separator through a winding process or a lamination process.

[0120] The end cap assembly 32 includes an electrode terminal 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 further includes a current collecting member 34, which is used to connect the tab 331 of the electrode assembly 33 and the electrode terminal 322. For example, when the electrode sheet 1 of the embodiment of the present application is a positive electrode sheet, one current collecting member 34 is used to connect the tab of the positive electrode and the positive electrode terminal, and the other current collecting member 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 , and the electrode assembly 33 includes an electrode assembly body 330 and a tab 331 extending from the electrode assembly body 330 .

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

[0124] [Positive electrode]

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

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

[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), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0128] The positive electrode film layer 11 may further include a conductive agent, which 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]

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

[0131] The negative electrode current collector may be a metal foil or a composite negative electrode current collector. The negative electrode current collector may be a copper foil. The composite negative electrode current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0132] The negative electrode film layer includes a negative electrode active material. The negative electrode active material can be a negative electrode active material for a battery known in the art. 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, 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, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[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), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0134] The negative electrode film layer may also optionally include a conductive agent, which 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 plays a role in conducting ions between the positive electrode and the negative electrode. The present application embodiment has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

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

[0138] The electrolyte salt may include one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorobisoxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0139] The solvent may include one or more of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

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

[0141] [Isolation film]

[0142] The separator is used to separate the positive electrode sheet from the negative electrode sheet. The embodiment of the present application has no particular limitation on the type of separator, and any known porous structure separator with good chemical stability and mechanical stability can be selected.

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

[0144] The positive electrode sheet, negative electrode sheet, and separator 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. Combining Figure 2 as shown, the preparation method 200 of the electrode sheet can include the following steps.

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

[0148] Among them, providing the positive electrode sheet includes: mixing a first metal oxide, a second metal oxide, and a surfactant to obtain a slurry for the positive electrode film layer, where the chemical formula of the first metal oxide satisfies: Li 5 MO 4 , 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 O 2 , 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 rubbers, and polyvinylpyrrolidones; coating the slurry of the positive electrode film layer on at least one side surface of the current collector to prepare the positive electrode sheet.

[0149] During the process of preparing the positive electrode sheet, a positive electrode active material, a binder, a conductive agent, and a solvent can also be added, and after mixing, a slurry for the positive electrode film layer is obtained.

[0150] As an example, the slurry of the positive electrode film layer is coated on the surfaces of both sides of the current collector to prepare the positive electrode sheet.

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

[0152] In the preparation method of the battery cell of the embodiment of the present application, the first metal oxide, the second metal oxide, and the surfactant are mixed to form a slurry of the positive electrode film layer, which is conducive to the uniform coating of the slurry. The prepared positive electrode plate can not only play a good role in lithium supplementation and improve the first cycle charging capacity of the battery cell, but also reduce the gas production of the battery cell in the aging stage after formation, reducing the gas production in the battery cell. In addition, the preparation method does not require sintering treatment of the first metal oxide and the second metal oxide, the preparation method is relatively simple, and the preparation complexity is low.

[0153] [Battery]

[0154] An embodiment of the present application provides a battery, including the battery cell in the above embodiment, and the battery cell may be a battery cell after formation and aging processes. Figure 4 Schematic diagram of a battery according to an embodiment of the present application. Figure 4 As shown, the battery 5 may include a plurality of battery cells (not shown in the figure).

[0155] The battery cells 3 can directly form the battery 5 , or can first form a battery module, and then multiple battery modules form the battery 5 .

[0156] [Electrical devices]

[0157] An embodiment of the present application provides an electrical device, comprising the battery described in the above embodiment.

[0158] In some embodiments, the electrical device includes an energy storage device or a heavy truck. The energy storage device and the heavy truck have high requirements for the service life and long-term cycle performance of the battery cells. Applying the battery cells to the above electrical devices can increase the service life of the electrical devices.

[0159] The electrical device may also be a lighting device, a spacecraft, etc., and the embodiments of the present application include but are not limited to the above.

[0160] Figure 5 FIG. 1 is a schematic diagram of an electrical device according to an embodiment of the present application. Figure 5 As shown, the present application provides an electrical device, which is a heavy truck 6. The batteries in the heavy truck 6 can be replaced by a battery replacement device to replace low-power batteries with fully-charged batteries.

[0161] Figure 6 FIG. 1 is a schematic diagram of an electrical device according to an embodiment of the present application. Figure 6 As shown, the present application provides an electric device, which is an energy storage device 7, and the energy storage device 7 may include a plurality of batteries 5. The energy storage device 7 may be applied to a power storage station 2 to store and release electric energy.

[0162] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0163] [Examples and Comparative Examples]

[0164] Example 1

[0165] (1) Preparation of positive electrode sheet

[0166] The first metal oxide Li 5 FeO 4 and the second metal oxide Li 2 NiO 2 The mixed material and the positive electrode active material are mixed in 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, dissolved in the solvent N-methylpyrrolidone (NMP), and fully stirred and mixed to prepare a positive electrode slurry. The viscosity η of the positive electrode slurry is 8453mPa·S; the positive electrode slurry is evenly coated on the two opposite surfaces of the positive electrode current collector aluminum foil, and then dried, cold pressed, and cut to obtain a positive electrode sheet. Among them, the positive electrode active material is lithium iron phosphate and carbon black, a carbon material coated on the surface of lithium iron phosphate, and the thickness L of the carbon coating layer formed by carbon black is 3nm; the volume average particle size Dv50 of the positive electrode active material is 1.5μm; the first metal oxide Li 5 FeO 4 The mass percentage of the second metal oxide Li in the positive electrode film layer is 2.4%. 2 NiO 2 The mass percentage of the positive electrode film layer is 0.6%, the mass percentage of the surfactant alkyl phosphate in the positive electrode film layer is 0.4%; and the powder resistivity R is 8.3Ω·cm.

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

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

[0169] (4) Preparation of electrolyte: Ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1:1, and then LiPF 6 is uniformly dissolved in the above solution to obtain an electrolyte, in which LiPF 6 The concentration is 1 mol / L.

[0170] (5) Preparation of lithium-ion batteries: The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is added. After packaging, standing, forming, aging, and other processes, a battery cell is obtained.

[0171] Embodiment 2-5

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

[0173] Embodiment 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 the 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 first metal oxide Li 5 FeO 4 and the second metal oxide Li 2 NiO 2 The mass percentage of the mixed materials in the positive electrode film layer is different.

[0179] In Examples 1-19 of the present application, the first metal oxide Li 5 FeO 4 The mass percentage of the second metal oxide Li in the positive electrode film 2 NiO 2 The mass percentage ratio in the positive electrode film layer is fixed, which is 4:1.

[0180] Comparative Example 1

[0181] The difference between Comparative Example 1 and Example 1 is that the surfactant alkyl phosphate is not added to the positive electrode slurry, and the positive electrode film layer of the positive electrode sheet does not contain the surfactant alkyl phosphate.

[0182] Comparative Example 2

[0183] The difference between Comparative Example 2 and Example 1 is that the second metal oxide is not added to the positive electrode slurry, and the positive electrode film layer of the positive electrode sheet does not contain the 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, P 1 It represents the mass percentage of surfactant based on the total mass of the positive electrode film layer; P 2 represents the mass percentage of the first metal oxide based on the total mass of the positive electrode film layer; P 3 It represents the mass percentage of the second metal oxide based on the total mass of the positive electrode film layer; Dv50 represents the volume average particle size of the positive electrode active material; L represents the thickness of the carbon coating layer coated on the positive electrode active material; R represents the powder resistivity of the positive electrode active material at 20 MPa; η represents the viscosity of the slurry of the positive electrode film layer.

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

[0190]

[0191]

[0192] The following is a brief introduction to the test methods of the physical and chemical parameters and performance parameters involved in the embodiments of the present application. It should be understood that the following test methods are only examples, and other test methods known in the art may also be used for testing.

[0193] 1. Measurement of first cycle charging capacity

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

[0195] 2. Test of aging gas production

[0196] After the formation is completed, the battery cell is left to stand at 45°C for 48 hours to measure the aging gas production. The aging gas production can be obtained by infrared or water displacement test. Specifically, the volume before and after standing can be tested by water displacement method, and the gas production can be calculated based on the change in volume. The aging gas production is ΔM / (ρ 液 ×Q), where ΔM is the mass of the drainage, ρ 液 is the density of the liquid, and Q is the capacity of the battery cell.

[0197] 3. Test of cycle capacity retention rate

[0198] In the voltage range of 2.5V to 4.2V, charge at a rate of 0.1C to the voltage limit, then charge at a constant voltage until the current is ≤ 0.05mA, let stand for 2 minutes, and discharge at a rate of 0.1C to 2.5V. At this time, the charging capacity is the initial capacity Q1. After the nth cycle, the capacity tested by the same process is Qn; cycle capacity retention rate = (1-(Qn / Q1)^(1 / n))×100%. Among them, Qn is the battery capacity after the nth cycle, Q1 is the initial battery capacity, and n is the number of cycles.

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

[0200] As an example, the positive electrode sheet of the battery cell before formation is taken as a sample, and the positive electrode sheet is observed using a scanning electron microscope. The first metal oxide, the second metal oxide and the positive electrode active material can be distinguished by the observed particle size. Afterwards, the positive electrode film layer of the positive electrode sheet can be scraped off, and the scraped material can be added to aqua regia and digested under mechanical stirring for 30 minutes; the digested solution is added to the ICAP7400 spectrometer to quantitatively analyze the mass fraction of each element in the material, and the mass content of the first metal oxide and the second metal oxide is calculated by the mass fraction of each element.

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

[0202] 5. Volume average particle size test

[0203] The raw materials for preparing the positive electrode plates can be measured. As an example, the volume average particle size Dv50 can be measured by referring to the particle size distribution laser diffraction method in GB / T 19077-2016 using a laser particle size analyzer.

[0204] In addition, the positive electrode can be observed through a scanning electron microscope, and an area of ​​a specific size can be taken to calculate the volume average particle size based on the size and number of particles observed in the specific area.

[0205] 6. Test of powder resistivity

[0206] An appropriate amount of powder of the positive electrode active material was weighed, and then the powder resistivity of the sample was measured using a powder resistivity tester (ST2722 digital four-probe tester, Suzhou Jingge Electronics Co., Ltd.) according to GB / T 30835-2014 "Carbon composite lithium iron phosphate lithium supplement material for lithium ion batteries", and the test pressure was 20 MPa.

[0207] As shown in Examples 1-19 and Comparative Example 1, by adding a surfactant to the slurry of the positive electrode film layer, the viscosity of the positive electrode slurry is significantly reduced (in Comparative Example 1, the slurry viscosity is too high to be measured, and the slurry cannot be coated).

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

[0209] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that: include: A positive electrode sheet, the positive electrode sheet comprising 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; 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, 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 phosphates, acrylates, hydrogenated nitrile and polyvinyl pyrrolidone.

2. The battery cell according to claim 1, characterized in that: Based on the total mass of the positive electrode film layer, the mass percentage content 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 any one of claims 1 to 3, characterized in that: 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%。 5. The battery cell according to claim 4, characterized in that: 0.8％≤P2≤4％。 6. The battery cell according to any one of claims 1 to 5, characterized in that: 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%。 7. The battery cell according to claim 6, characterized in that: 0.2％≤P3≤1％。 8. The battery cell according to any one of claims 1 to 7, characterized in that: The surface of the second metal oxide is coated with oxide and / or carbon material.

9. The battery cell according to claim 8, characterized in that: The oxide includes a metal element, and the metal element includes one or more of Ni, W, Cu, Mn, Al, Fe, Ti, Mo, Ce, Co, Cr or V.

10. The battery cell according to claim 8 or 9, characterized in that: The oxide includes Al2O3.

11. The battery cell according to any one of claims 8 to 10, characterized in that: Based on the total mass of the second metal oxide and the oxide, the mass percentage content P5 of the oxide satisfies: 0.1%≤P5≤10%.

12. The battery cell according to claim 11, characterized in that: 0.5％≤P5≤5％。 13. The battery cell according to any one of claims 1 to 12, characterized in that: The positive electrode film layer further includes a positive electrode active material, and the volume average particle size Dv50 of the positive electrode active material satisfies: 0.5 μm≤Dv50≤10 μm.

14. The battery cell according to claim 13, characterized in that: 0.5μm≤Dv50≤5μm.

15. The battery cell according to claim 13 or 14, characterized in that: Based on the total mass of the positive electrode film layer, the mass percentage content P4 of the positive electrode active material satisfies: 80%≤P4≤95%.

16. The battery cell according to any one of claims 13 to 15, characterized in that: The positive electrode active material includes: a lithium-containing phosphate having an olivine structure, and the lithium-containing phosphate having an olivine structure includes lithium iron phosphate.

17. The battery cell according to claim 16, characterized in that: The positive electrode active material further includes a carbon material, and the carbon material is coated on the surface of the lithium-containing phosphate to form a carbon coating layer.

18. The battery cell according to claim 17, characterized in that: The thickness L of the carbon coating layer satisfies: <L≤10nm。 19. The battery cell according to claim 18, characterized in that: 1nm≤L≤5nm.

20. The battery cell according to any one of claims 13 to 19, characterized in that: The powder resistivity R of the positive electrode active material at 20 MPa satisfies: 2Ω·cm≤R≤50Ω·cm.

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

22. The battery cell according to any one of claims 1 to 21, characterized in that: The battery cells are battery cells before formation.

23. A method for preparing a battery monomer, characterized in that: include: Providing a positive electrode sheet to prepare the battery cell; Wherein, providing the positive electrode sheet comprises: Mix the first metal oxide, the second metal oxide and a surfactant to obtain a slurry for the positive electrode 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, and 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 rubbers, and polyvinylpyrrolidones; The slurry of the positive electrode film layer is coated on the surface of at least one side of the current collector to provide the positive electrode sheet.

24. The preparation method according to claim 23, characterized in that: The viscosity η of the slurry satisfies: 5000mPa·S<η≤30000mPa·S.

25. The preparation method according to claim 24, characterized in that: 7000mPa·S<η≤10000mPa·S.

26. An electrical device, characterized in that: include: A battery cell according to any one of claims 1 to 22, and / or a battery cell obtained by the preparation method according to any one of claims 23 to 25.

27. The electrical device according to claim 26, characterized in that: The electrical device includes an energy storage device or a heavy truck.

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