Battery cell and manufacturing method therefor, and electric device

Abstract

A battery cell and a manufacturing method therefor, and an electric device. The battery cell comprises a positive electrode sheet; the positive electrode sheet comprises a first metal oxide and a second metal oxide; the chemical formula of the first metal oxide satisfies Lia1M1Oc1, 0.2≤a1≤8.2, 1.8≤c1≤6.2, and M1 comprises one or more of V, Nb, Cr, Mo, Fe, Co, or Sn; the chemical formula of the second metal oxide satisfies Lia2Ni1-bM2 bOc2, 0≤a2≤2.2, 0≤b≤1, 0.8≤c2≤2.2, and M2 comprises one or more of Cu, Mg, Zn, Mn, Al, Zr, or Ti; and the ratio of the number of primary particles of the first metal oxide having a particle size of 5 μm-15 μm to a total number of all primary particles of the first metal oxide is 40%-90%. The present invention can reduce gas production in a battery cell and lower the risk of lithium precipitation.

Description

Battery cells and their preparation methods, and electrical devices Cross-reference to related applications

[0001] This application claims priority to Chinese Patent Application No. 202411215875.3, filed on August 30, 2024, entitled “Battery Cell and Method for Preparation Thereof, Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, and more specifically, to a battery cell, a method for preparing the same, and an electrical device thereof. Background Technology

[0003] The new energy industry is attracting increasing attention. Within this industry, battery technology is a crucial factor in its development.

[0004] The development of battery technology requires consideration of various design factors, such as energy density, cycle life, capacity, and reliability. As a lithium replenishment material, metal oxides can provide active lithium ions to the battery to compensate for lithium ion consumption during formation and other stages, thereby improving the battery's initial charge capacity. However, metal oxides also exhibit significant gas generation and lithium plating risks after delithiation, which are detrimental to battery reliability. Therefore, providing a battery cell with both high initial charge capacity and high reliability is a pressing technical problem that needs to be solved. Summary of the Invention

[0005] This application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell with less gas production and a lower risk of lithium plating, so as to balance the reliability of the battery cell and the first charge capacity.

[0006] To achieve the above objectives, this application provides a battery cell, a method for preparing the same, and an electrical device thereof.

[0007] In a first aspect, a battery cell is provided, comprising: a positive electrode sheet, the positive electrode sheet including 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 including a first metal oxide and a second metal oxide; the chemical formula of the first metal oxide satisfying: Li a1 M 1 O c1 , 0.2≤a1≤8.2, 1.8≤c1≤6.2, M 1 Including one or more of V, Nb, Cr, Mo, Fe, Co, or Sn; the chemical formula of the second metal oxide satisfies: Li a2 Ni 1-b M 2b O c2 , 0≤a2≤2.2, 0≤b≤1, 0.8≤c2≤2.2, M 2 It includes one or more of Cu, Mg, Zn, Mn, Al, Zr or Ti; the ratio of the number of primary particles of the first metal oxide with a particle size of 5 μm to 15 μm to the total number of primary particles of the first metal oxide is 40% to 90%.

[0008] In this embodiment, the battery cell includes a positive electrode sheet, which includes a positive current collector and a positive electrode film layer disposed on at least one side surface of the positive current collector. The positive electrode film layer includes a first metal oxide and a second metal oxide. The first metal oxide and the second metal oxide can provide lithium ions, thereby facilitating the replenishment of lithium ions consumed in the battery cell and improving the first-cycle charging capacity of the battery cell. Furthermore, by combining the first metal oxide and the second metal oxide that meet the above-mentioned particle size distribution, the amount of gas generated by the battery cell during the aging stage after formation can be reduced, the risk of lithium plating in the battery cell can be reduced, and the reliability of the battery cell can be improved. Therefore, the technical solution of this embodiment can improve the first-cycle charging capacity and reliability of the battery cell.

[0009] In one possible implementation, the ratio of the number of primary particles of the first metal oxide with a particle size of 5 μm to 11 μm to the total number of primary particles of the first metal oxide is 50% to 80%. This helps to further reduce the amount of gas generated by the battery cell during the aging stage after formation, reduce the risk of lithium plating in the battery cell, and improve the reliability of the battery cell.

[0010] In one possible implementation, 150μm 2 The ratio of the number of weak agglomerates of the first metal oxide to the number of secondary particles of the first metal oxide is 50% to 100%, wherein the weak agglomerates are secondary particles with a primary particle count of less than or equal to 10. This proportion of weak agglomerates within the above range reduces the risk of severe gas generation due to excessive large agglomerates, which can cause gas to remain near the electrode for a short period, disrupting the interface and leading to lithium plating. This improves the reliability of the battery cell.

[0011] In one possible implementation, 150μm 2 The ratio of the number of weak aggregates of the first metal oxide to the number of secondary particles of the first metal oxide is 80% to 100%. This helps to further reduce the risk of lithium plating and improve the reliability of the battery cell.

[0012] In one possible implementation, the average particle size of the first metal oxide is 5 μm to 15 μm, and / or the maximum particle size of the first metal oxide is 20 μm to 30 μm, and / or the minimum particle size of the first metal oxide is 3.5 μm to 6 μm. This results in a more suitable particle size distribution for the first metal oxide, better combination of the first and second metal oxides, less gas generation in the battery cell, a lower risk of lithium plating, and higher reliability of the battery cell.

[0013] In one possible implementation, the average particle size of the second metal oxide is 10 μm to 20 μm. This combination of the first and second metal oxides yields better results, leading to less gas generation in the battery cell, a lower risk of lithium plating, and higher reliability of the battery cell.

[0014] In one possible implementation, the positive electrode film layer further includes a positive electrode active material. Based on the total mass of the first metal oxide, the second metal oxide, and the positive electrode active material, the mass content P of the positive electrode active material satisfies: 90wt% ≤ P ≤ 99wt%. In this way, the positive electrode active material, the first metal oxide, and the second metal oxide all have suitable mass contents, allowing the battery cell to have a higher initial charge capacity, higher overall capacity, and better long-term cycle performance.

[0015] In one possible implementation, the positive electrode active material comprises a lithium phosphate, wherein the average particle size of the lithium phosphate is smaller than the average particle size of the first metal oxide or the average particle size of the second metal oxide.

[0016] In one possible implementation, the average particle size of the lithium phosphate is 0.5 μm to 3 μm.

[0017] In the above technical solution, the lithium phosphate, the first metal oxide, and the second metal oxide have a better particle size distribution, which is beneficial to improving the first charge capacity and reliability of the battery cell.

[0018] In one possible implementation, the molar ratio C of the first metal oxide and the second metal oxide satisfies: 1:1 ≤ C ≤ 10:1. When C ≥ 1:1, the first metal oxide has a higher proportion relative to the second metal oxide, which is beneficial for improving the first-cycle charging capacity of the battery cell; when C ≤ 10:1, the second metal oxide has a suitable proportion, which is beneficial for reducing the amount of gas generated in the battery cell.

[0019] In one possible implementation, 3:1 ≤ C ≤ 5:1. This approach, when including cells containing lithium phosphate, is beneficial for both reducing gas production in individual cells and increasing the initial charge capacity of those cells, thus achieving a better balance between gas production and initial charge capacity.

[0020] In one possible implementation, the positive electrode active material comprises a lithium transition metal oxide, which includes at least one of a single-crystal lithium transition metal oxide or a polycrystalline lithium transition metal oxide, wherein the average particle size of the single-crystal lithium transition metal oxide is 2 μm to 5 μm, and the average particle size of the polycrystalline lithium transition metal oxide is 9 μm to 15 μm.

[0021] In the above technical solution, the lithium transition metal oxide, the first metal oxide, and the second metal oxide have a better particle size distribution, which is beneficial to improving the first charge capacity and reliability of the battery cell.

[0022] In one possible implementation, the molar ratio C of the first metal oxide and the second metal oxide satisfies: 1:1 ≤ C ≤ 10:1. When C ≥ 1:1, the first metal oxide has a higher proportion relative to the second metal oxide, which is beneficial for improving the first-cycle charging capacity of the battery cell; when C ≤ 10:1, the second metal oxide has a suitable proportion, which is beneficial for reducing the amount of gas generated in the battery cell.

[0023] In one possible implementation, 1:1 ≤ C ≤ 3:1. This approach, in battery cells including lithium transition metal oxides, is beneficial for both reducing gas production in the cells and increasing the initial charge capacity, thus achieving a better balance between gas production and initial charge capacity.

[0024] In one possible implementation, the surface of the first metal oxide has a first surface material, the first surface material comprising an aluminum-containing compound and / or a carbon material; and / or, the surface of the second metal oxide has a second surface material, the second surface material comprising an aluminum-containing compound and / or a carbon material.

[0025] Depositing carbon materials on the surface of the first metal oxide and / or the second metal oxide helps reduce the agglomeration of the first metal oxide and / or the second metal oxide, reduces gas retention at the electrode interface, and lowers the risk of lithium plating. Furthermore, it facilitates lithium ion extraction and increases the first-cycle charging capacity of the battery cell. Depositing aluminum-containing compounds on the surface of the first metal oxide and / or the second metal oxide helps improve the stability of their crystal structure.

[0026] In one possible implementation, in the first metal oxide, based on the total mass of the first metal oxide, the mass content D1 of aluminum in the aluminum-containing compound satisfies: 0.1 wt% ≤ D1 ≤ 10 wt%, and / or, the mass content E1 of carbon in the carbon material satisfies: 0.1 wt% ≤ E1 ≤ 10 wt%; and / or, in the second metal oxide, based on the total mass of the second metal oxide, the mass content D2 of aluminum in the aluminum-containing compound satisfies: 0.1 wt% ≤ D2 ≤ 10 wt%, and / or, the mass content E2 of carbon in the carbon material satisfies: 0.1 wt% ≤ E2 ≤ 10 wt%. In this way, the battery cell has a suitable first-cycle charging capacity and a low gas production.

[0027] In one possible implementation, 0.5wt% ≤ D1 ≤ 5wt%, and / or 0.5wt% ≤ E1 ≤ 5wt%; and / or 0.5wt% ≤ D2 ≤ 5wt%, and / or 0.5wt% ≤ E2 ≤ 5wt%. This results in a battery cell having a suitable initial charge capacity and less gas production.

[0028] In one possible implementation, the first metal oxide comprises one or more of Li5FeO4 or LiFeO2, and the second metal oxide comprises one or more of Li2NiO2 or NiO2. After a certain number of charge-discharge cycles, the first metal oxide can be delithiated to form LiFeO2, and the second metal oxide can be delithiated to form NiO2. If the first metal oxide is not completely consumed, Li5FeO4 will remain, and if the second metal oxide is not completely consumed, Li2NiO2 will remain.

[0029] In one possible implementation, the volumetric particle size distribution of the first metal oxide is Dv50. 1 Satisfies: 1μm≤Dv50 1 ≤20μm, and / or, the volumetric particle size distribution Dv90 of the first metal oxide 1 Satisfies: 15μm≤Dv90 1 ≤25μm, and / or, the volumetric particle size distribution Dv10 of the first metal oxide 1 Satisfies: 3μm≤Dv10 1 ≤7μm. In this way, the first metal oxide has a more suitable particle size distribution, and there is a better matching effect between the second metal oxide. This helps to reduce the amount of gas generated by the battery cells during the aging stage after formation, reduce the risk of lithium plating in the battery cells, and improve the reliability of the battery cells.

[0030] In one possible implementation, 5μm≤Dv501 ≤14μm, and / or, 16μm≤Dv90 1 ≤20μm, and / or, 4.5μm≤Dv10 1 ≤6μm. This helps to further reduce the amount of gas generated by battery cells during the aging stage after formation, reduce the risk of lithium plating in battery cells, and improve the reliability of battery cells.

[0031] In one possible implementation, 5μm≤Dv90 1 -Dv50 1 ≤14μm, and / or, 2μm≤Dv50 1 -Dv10 1 ≤10μm. In this way, the particles of the first metal oxide are more uniform and have a more suitable particle size distribution, and there is a better matching effect between the second metal oxide. This helps to reduce the amount of gas generated by the battery cell during the aging stage after formation, reduce the risk of lithium plating in the battery cell, and improve the reliability of the battery cell.

[0032] In one possible implementation, 5μm≤Dv90 1 -Dv50 1 ≤10μm, and / or, 2μm≤Dv50 1 -Dv10 1 ≤6μm. This helps to further reduce the amount of gas generated by battery cells during the aging stage after formation, reduce the risk of lithium plating in battery cells, and improve the reliability of battery cells.

[0033] In one possible implementation, the volumetric particle size distribution of the first metal oxide is Dv99. 1 Satisfies: 20μm≤Dv99 1 ≤30μm. This results in a more uniform particle size distribution of the first metal oxide, which helps reduce the amount of gas generated in the battery cell.

[0034] In one possible implementation, the quantity distribution Dn10 of the first metal oxide satisfies: 0.5 μm ≤ Dn10 ≤ 1.0 μm. This gives the first metal oxide a suitable particle size, which is beneficial for reducing gas generation in the battery cell.

[0035] In one possible implementation, the specific surface area S1 of the first metal oxide satisfies: 0.01 m². 2 / g≤S1≤10m 2 / g, and / or, the specific surface area S2 of the second metal oxide satisfies: 0.01m 2 / g≤S2≤10m 2 / g. In this way, the first metal oxide and the second metal oxide have suitable specific surface areas, which are conducive to the diffusion of lithium ions, thereby helping to improve the first charge capacity of the battery cell.

[0036] In one possible implementation, 0.5m 2 / g≤S1≤5m 2 / g, and / or, 0.1m 2 / g≤S2≤5m 2 / g. This helps to further improve the first-charge capacity of individual battery cells.

[0037] In one possible implementation, the powder resistivity R1 of the first metal oxide at 20 MPa satisfies: R1 ≤ 25 Ω·cm. This gives the first metal oxide high conductivity, which is beneficial for further increasing the capacity of the battery cell.

[0038] In one possible implementation, R1 ≤ 5 Ω·cm. This results in the first metal oxide having higher conductivity, which is beneficial for further increasing the capacity of the battery cell.

[0039] In one possible implementation, the volumetric particle size distribution of the second metal oxide is Dv50. 2 Satisfies: 1μm≤Dv50 2 ≤50μm. In this way, the second metal oxide has a suitable particle size, which facilitates the extraction of lithium ions and gives the battery cell a high first-charge capacity.

[0040] In one possible implementation, 10μm≤Dv50 2 ≤20μm. This helps to further improve the first-cycle charging capacity of individual battery cells.

[0041] Secondly, a method for preparing a battery cell is provided, comprising: providing a positive electrode sheet to prepare the battery cell; wherein providing the positive electrode sheet comprises: mixing a first metal oxide and a second metal oxide to obtain a slurry for a positive electrode film layer, wherein the chemical formula of the first metal oxide satisfies: Li a1 M 1 O c1 , 0.2≤a1≤8.2, 1.8≤c1≤6.2, M 1 Including one or more of V, Nb, Cr, Mo, Fe, Co, or Sn; the chemical formula of the second metal oxide satisfies: Li a2 Ni 1-b M 2 b O c2 , 0≤a2≤2.2, 0≤b≤1, 0.8≤c2≤2.2, M 2including one or more of Cu, Mg, Zn, Mn, Al, Zr or Ti; the volume particle size distribution Dv50 of the first metal oxide 1 satisfies: 1μm ≤ Dv50 1 ≤ 20μm, and / or, the volume particle size distribution Dv90 of the first metal oxide 1 satisfies: 15μm ≤ Dv90 1 ≤ 25μm; 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.

[0042] The preparation method of the above positive electrode sheet is relatively simple, and the preparation complexity is low; and after the prepared positive electrode sheet is applied to the battery cell, the battery cell has a high first-cycle charging capacity, a small gas generation amount and a low risk of lithium precipitation, and the battery cell has both a high first-cycle charging capacity and high reliability.

[0043] In a possible implementation manner, 2.8 ≤ a1 ≤ 8.2, 2.8 ≤ c1 ≤ 6.2, 1 < a2 ≤ 2.2, 0 < b ≤ 1, 1.8 ≤ c2 ≤ 2.2. When the molar contents of the elements of the first metal oxide and the second metal oxide satisfy the above ranges, more lithium ions can be extracted during the charge and discharge process of the battery cell to supplement lithium ions to the battery cell.

[0044] In a possible implementation manner, the first metal oxide includes Li5FeO4, and the second metal oxide includes Li2NiO2. Li5FeO4 can extract more lithium ions, and the combination of Li5FeO4 and Li2NiO2 can both improve the first-cycle charging capacity of the battery cell and reduce the gas generation amount of the battery cell.

[0045] In a possible implementation manner, 150μm 2 The ratio of the number of weak agglomerates of the first metal oxide to the number of secondary particles of the first metal oxide within is 50% - 100%, where the weak agglomerate is a secondary particle with the number of primary particles less than or equal to 10. In this way, the proportion of the number of weak agglomerates has a suitable range, which can reduce the interface problems and the risk of lithium precipitation caused by the excessive agglomeration degree of the agglomerates resulting in the gas in the battery cell staying near the electrode sheet, and is beneficial to improving the reliability of the battery cell.

[0046] In the third aspect, an electrical device is provided, including the battery cell in the first aspect and any one of the possible implementation manners thereof, and / or the battery cell obtained by the preparation method in the second aspect and any one of the possible implementation manners thereof.

[0047] In one possible implementation, the electrical device includes an energy storage device or a truck. Energy storage devices and 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

[0048] 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.

[0049] Figure 1 is a schematic diagram of the structure of a positive electrode sheet according to an embodiment of this application;

[0050] Figure 2 is a schematic diagram of a battery cell according to an embodiment of this application;

[0051] Figure 3 is a schematic diagram of a method for preparing a battery cell according to an embodiment of this application;

[0052] Figure 4 is a schematic diagram of a battery according to an embodiment of this application;

[0053] Figure 5 is a schematic diagram of an electrical device according to an embodiment of this application;

[0054] Figure 6 is a schematic diagram of an electrical device according to an embodiment of this application;

[0055] Figure 7 is a SEM schematic diagram of the positive electrode sheet according to an embodiment of this application;

[0056] Figure 8 is a SEM schematic diagram of a first metal oxide according to an embodiment of this application;

[0057] Figure 9 is a SEM schematic diagram of a first metal oxide according to an embodiment of this application;

[0058] Figure 10 is a SEM schematic diagram of a pair of proportions of the first metal oxide of this application.

[0059] Reference numerals: 1: Positive electrode sheet; 10: Positive current collector; 11: Positive electrode film; 3: Battery cell; 31: Casing; 32: End cap assembly; 33: Electrode assembly; 34: Connecting member; 322: Electrode terminal; 331: Tab; 5: Battery; 6: Truck; 7: Energy storage device. Detailed Implementation

[0060] The battery cell and its preparation method, as well as the embodiments of the electrical device, of this application have been described in detail with 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 making the following description unnecessarily lengthy 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.

[0061] 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 included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 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.

[0062] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0063] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0064] 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.

[0065] 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 the active lithium; for example, adding Li5FeO4 to the positive electrode can replenish active lithium, thereby improving the initial charge capacity. However, during charging, Li5FeO4 releases a significant amount of oxygen while delithiating to release active lithium ions. This 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 and lithium plating within the battery cell, which is detrimental to improving the cell's performance.

[0066] In some implementations, Li5FeO4 and Li2NiO2 are mixed to reduce gas production in battery cells during post-formation aging stages while replenishing active lithium ions. However, this method still results in significant gas production and lithium plating during post-formation aging stages, offering limited improvement in battery cell reliability.

[0067] 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 and a second metal oxide; the chemical formula of the first metal oxide satisfies: Li a1 M 1 O c1 , 0.2≤a1≤8.2, 1.8≤c1≤6.2, M 1 Including one or more of V, Nb, Cr, Mo, Fe, Co, or Sn; the chemical formula of the second metal oxide satisfies: Li a2 Ni 1-b M 2 b O c2 , 0≤a2≤2.2, 0≤b≤1, 0.8≤c2≤2.2, M 2 The first metal oxide comprises one or more of Cu, Mg, Zn, Mn, Al, Zr, or Ti; the ratio of the number of primary particles of the first metal oxide with a particle size of 5 μm to 15 μm to the total number of primary particles of the first metal oxide is 40% to 90%. By combining the second metal oxide with the first metal oxide that meets the above particle size distribution, the first-cycle charging capacity of the battery cell can be improved while reducing gas generation and lithium plating risk in the battery cell, thereby balancing the first-cycle charging capacity and reliability of the battery cell.

[0068] In the embodiments of this application, the first and second metal oxides are used as lithium replenishing agents to compensate for the irreversible lithium loss caused during SEI film formation. During the charging process of the battery cell, lithium ions are extracted from the first and second metal oxides to provide active lithium ions.

[0069] During the charging process of a single 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.

[0070] It should be understood that the “intercalation” process described in this application refers to the process by which lithium ions are intercalated into the positive electrode active material or the negative electrode due to an electrochemical reaction, and the “extraction” and “deintercalation” processes described in this application refer to the process by which lithium ions are extracted from the positive electrode active material or the negative electrode due to an electrochemical reaction.

[0071] In the embodiments of this application, formation can be understood as the initialization of a battery cell, which is the process of activating the active material of the battery cell; it can also be understood as a process of charging the battery cell, and formation helps to form the SEI film in the battery cell.

[0072] In the embodiments of this application, aging can refer to the process of leaving the battery cells at room temperature or high temperature after formation. The aging process helps the SEI structure to reorganize and form a loose and porous film, which is beneficial to make the voltage of the battery cells more accurate and stable, and also helps the electrolyte to fully wet the electrode.

[0073] In the embodiments of this application, formation and aging are processes performed before the battery cells are shipped.

[0074] In this application's embodiments, a single battery cell can refer to the smallest structural unit of a battery. Multiple battery cells can first be assembled into a battery module, and then the battery module can be assembled into a battery; multiple battery cells can also be directly assembled into a battery.

[0075] In this application, the battery cell refers to a lithium-ion secondary battery, that is, a lithium-ion battery cell that can be reversibly charged and discharged.

[0076] [Battery cell]

[0077] This application provides a battery cell including a positive electrode.

[0078] Figure 1 is a schematic diagram of the structure of a positive electrode sheet according to an embodiment of this application. For example, as shown in Figure 1, the positive electrode sheet 1 includes a positive current collector 10 and a positive electrode film layer 11 disposed on at least one side surface of the positive current collector 10.

[0079] The positive electrode current collector 10 has two opposing surfaces along its thickness direction. The positive electrode film layer 11 can be disposed on one surface of the positive electrode current collector 10 or on both surfaces. As an example, as shown in FIG1, the positive electrode film layer 11 is disposed on both surfaces of the positive electrode current collector 10.

[0080] The positive electrode film 11 includes a first metal oxide and a second metal oxide. The first metal oxide and the second metal oxide are different lithium supplementation materials.

[0081] Before the first charge of a battery cell, the first and second metal oxides have a higher molar lithium content compared to the positive electrode active material, allowing for the release of more lithium ions to compensate for irreversible lithium loss; for example, the molar lithium content in the first and second metal oxides is greater than 1. After the battery cell undergoes its first charge (e.g., formation process) and subsequent charge-discharge cycles, the first and second metal oxides form other products during lithium removal, causing changes in the molar lithium content in both materials.

[0082] The chemical formula of the first metal oxide satisfies: Li a1 M 1 O c1 , 0.2≤a1≤8.2, 1.8≤c1≤6.2, M 1 It includes one or more of V, Nb, Cr, Mo, Fe, Co, or Sn. Wherein, a1 can be 0.2, 0.5, 1, 1.5, 2, 2.5, 2.8, 3, 4, 5, 6, 7, 8, 8.2, or any value within the above range, and c1 can be 1.8, 2, 3, 4, 5, 6, 6.2, or any value within the above range.

[0083] The chemical formula of the second metal oxide satisfies: Li a2 Ni 1-b M 2 b O c2 , 0≤a2≤2.2, 0≤b≤1, 0.8≤c2≤2.2, M 2 It includes one or more of Cu, Mg, Zn, Mn, Al, Zr, or Ti. Wherein, a2 can be 0, 0.5, 1, 1.04, 1.2, 1.5, 1.8, 2, 2.2, or any value within the above range; b can be 0, 0.3, 0.4, 0.5, 0.8, 1, or any value within the above range; and c2 can be 0.8, 1, 1.8, 2, 2.2, or any value within the above range.

[0084] When b is 0, the transition metal element in the second metal oxide is mainly Ni; when b is greater than 0, the second metal oxide is also doped with other transition metal elements, such as Cu, Co, Mg, Zn, Al, etc.

[0085] During the formation stage of the battery cell and the subsequent charge-discharge cycle, the first metal oxide and the second metal oxide undergo delithiation to release lithium ions, and their specific compositions also change. For example, the first metal oxide before formation includes Li5FeO4, which becomes LiFeO2 after delithiation; the second metal oxide before formation includes Li2NiO2, which becomes Li2O and NiO2 after delithiation. After the formation stage and the subsequent charge-discharge cycle, at least a portion of the first metal oxide and at least a portion of the second metal oxide change, and the molar content of lithium and oxygen also changes accordingly.

[0086] The ratio of the number of primary particles of the first metal oxide with a particle size of 5 μm to 15 μm to the total number of primary particles of the first metal oxide is 40% to 90%.

[0087] The first metal oxide includes primary particles of the first metal oxide, secondary particles of the first metal oxide, and may also include crushed particles. The crushed particles are mostly particles with a diameter of less than 2 μm, and may exist alone or be attached to the surface of the primary or secondary particles.

[0088] Primary particles can refer to unagglomerated particles, while secondary particles refer to agglomerated particles, which include multiple primary particles agglomerated together.

[0089] For the first metal oxide, the particle type of the first metal oxide includes multiple primary particles, which may have the same or different particle sizes. For example, the particle size of the primary particles may be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 15 μm, 20 μm or other values.

[0090] As an example, a region of a certain size can be selected, and the number and size of primary particles of the first metal oxide within that region can be counted. Then, the ratio of the number of primary particles of the first metal oxide with a particle size of 5μm to 15μm to the total number of primary particles of the first metal oxide can be calculated.

[0091] The morphology of the first metal oxide can be irregular, for example, an irregular prism or polyhedron.

[0092] The particle size of the first metal oxide can be the maximum particle size of the first metal oxide. For example, the size of the first metal oxide (e.g., primary or secondary particles of the first metal oxide) is measured in three mutually perpendicular directions, and the largest size is taken as the particle size of the first metal oxide.

[0093] During the charging process of a battery cell, the first metal oxide releases oxygen after delithiation. For example, during the formation process of a battery cell, the first metal oxide delithilates and releases oxygen. 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, which not only increases the amount of gas produced by the battery cell but also poses a risk of lithium plating.

[0094] The positive electrode includes a first metal oxide and a second metal oxide, and the volume particle size distribution of the first metal oxide meets the above-mentioned range. This is not only beneficial to improving the first-cycle charging capacity of the battery cell, but also beneficial to reducing the amount of gas generated by the battery cell after formation, reducing the risk of lithium plating, and thus improving the reliability of the battery cell.

[0095] In some embodiments, the ratio of the number of primary particles of the first metal oxide with a particle size of 5 μm to 11 μm to the total number of primary particles of the first metal oxide is 50% to 80%. This helps to further reduce the amount of gas generated by the battery cell during the aging stage after formation, reduce the risk of lithium plating in the battery cell, and improve the reliability of the battery cell.

[0096] In some embodiments, 150μm 2 The ratio of the number of weak aggregates of the first metal oxide to the number of secondary particles of the first metal oxide is 50% to 100%, wherein the weak aggregates are secondary particles with a number of primary particles less than or equal to 10.

[0097] The ratio of the number of weak aggregates to the number of secondary particles of the first metal oxide can be 50%, 60%, 70%, 80%, 90%, 100%, or any value within the above range.

[0098] As an example, the secondary particles of the first metal oxide are all weak aggregates, that is, the ratio of the number of weak aggregates to the number of secondary particles of the first metal oxide is 100.

[0099] When the number of primary particles in secondary particles is greater than 10, the secondary particles are large agglomerates. Large agglomerates are not conducive to the discharge of gas generated near the electrode, and may damage the interface or even lead to lithium plating.

[0100] In the above embodiments, the proportion of weak agglomerates within the above range can reduce the risk of severe gas generation due to excessive large agglomerates, which would cause gas to remain near the electrode for a short time and fail to be discharged smoothly, damaging the interface and leading to lithium plating. This is beneficial to improving the reliability of the battery cell.

[0101] In some embodiments, 150μm 2 The ratio of the number of weak aggregates of the first metal oxide to the number of secondary particles of the first metal oxide is 80% to 100%. This helps to further reduce the risk of lithium plating and improve the reliability of the battery cell.

[0102] In some embodiments, the average particle size of the first metal oxide is 5 μm to 15 μm, and / or the maximum particle size of the first metal oxide is 20 μm to 30 μm, and / or the minimum particle size of the first metal oxide is 3.5 μm to 6 μm.

[0103] The average particle size of the first metal oxide can be the average particle size of the particles of the first metal oxide. For example, by taking a region of a specific size, counting the number and size of primary particles, and the number and size of secondary particles, the average particle size is the ratio of the sum of the particle sizes of all primary particles and all secondary particles to the sum of the number of primary and secondary particles.

[0104] The maximum particle size of the first metal oxide is the particle size of the largest particle in the first metal oxide; the minimum particle size of the first metal oxide is the particle size of the smallest particle in the first metal oxide.

[0105] The average particle size of the first metal oxide can be 5 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 15 μm or any value within the above range, the maximum particle size of the first metal oxide can be 20 μm, 22 μm, 25 μm, 28 μm, 30 μm or any value within the above range, and the minimum particle size of the first metal oxide can be 3.5 μm, 4 μm, 5 μm, 6 μm or any value within the above range.

[0106] In the above embodiments, the first metal oxide has a more suitable particle size distribution, the combination between the first metal oxide and the second metal oxide has a better effect, the amount of gas generated in the battery cell is less, the risk of lithium plating is lower, and the battery cell has higher reliability.

[0107] In some embodiments, the average particle size of the second metal oxide is 10 μm to 20 μm.

[0108] The average particle size of the second metal oxide can be 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, or any value within the above range. The test method for the average particle size of the second metal oxide is the same as that for the first metal oxide, and will not be repeated here.

[0109] In the above embodiments, the combination of the first metal oxide and the second metal oxide has a better effect, with less gas generation in the battery cell, a lower risk of lithium plating, and higher reliability of the battery cell.

[0110] In some embodiments, the positive electrode film layer further includes a positive electrode active material, and the mass content P of the positive electrode active material satisfies the following condition based on the total mass of the first metal oxide, the second metal oxide, and the positive electrode active material: 90wt%≤P≤99wt%.

[0111] P can be 90wt%, 93wt%, 96wt%, 99wt%, or any value within the above range.

[0112] In the above embodiments, the positive electrode active material, the first metal oxide, and the second metal oxide all have suitable mass content, and the battery cell can have a high first charge capacity, a high capacity, and good long-term cycle performance.

[0113] In some embodiments, the positive electrode active material includes a lithium phosphate, wherein the average particle size of the lithium phosphate is smaller than the average particle size of the first metal oxide or the average particle size of the second metal oxide.

[0114] Lithium-containing phosphates may include at least one of lithium iron phosphate, lithium manganese phosphate, and lithium manganese iron phosphate. As an example, lithium-containing phosphates include lithium iron phosphate.

[0115] In some embodiments, the average particle size of the lithium phosphate is 0.5 μm to 3 μm. The average particle size of the lithium phosphate can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 3 μm or any value within the above range.

[0116] The test method for the average particle size of lithium phosphate is the same as that for the first metal oxide, and will not be repeated here.

[0117] As an example, in the process of preparing the positive electrode sheet, the volume average particle size Dv50 of the lithium phosphate added is 0.5 μm to 3 μm.

[0118] In the above technical solution, the lithium phosphate, the first metal oxide, and the second metal oxide have a better particle size distribution, which is beneficial to improving the first charge capacity and reliability of the battery cell.

[0119] In some embodiments, the molar ratio C of the first metal oxide and the second metal oxide satisfies: 1:1 ≤ C ≤ 10:1.

[0120] The molar ratio C of the first metal oxide and the second metal oxide can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1 or any value within the above range.

[0121] The larger the molar ratio C of the first metal oxide and the second metal oxide, the more lithium ions are provided, which is beneficial to improving the first charge capacity of the battery cell. However, as the molar ratio C increases, the content of the second metal oxide is less, and the improvement on gas production in the battery cell is also weaker.

[0122] When C≥1:1, the first metal oxide has a higher proportion than the second metal oxide, which is beneficial to improving the first charge capacity of the battery cell; when C≤10:1, the second metal oxide has a suitable proportion, which is beneficial to reducing the amount of gas generated in the battery cell.

[0123] In some embodiments, 3:1 ≤ C ≤ 5:1. This approach, when including cells containing lithium phosphate, is beneficial for both reducing gas production in the cells and increasing the initial charge capacity, thus achieving a better balance between gas production and initial charge capacity.

[0124] In some embodiments, the positive electrode active material includes a lithium transition metal oxide, which includes at least one of a single-crystal lithium transition metal oxide or a polycrystalline lithium transition metal oxide. The average particle size of the single-crystal lithium transition metal oxide is 2 μm to 5 μm, and the average particle size of the polycrystalline lithium transition metal oxide is 9 μm to 15 μm.

[0125] Single-crystal lithium transition metal oxides can refer to lithium transition metal oxides with a single-crystal morphology; polycrystalline lithium transition metal oxides can refer to lithium transition metal oxides with a polycrystalline morphology, and polycrystalline can be formed by multiple single crystals.

[0126] The testing methods for the average particle size of single-crystal lithium transition metal oxides and polycrystalline lithium transition metal oxides are the same as those for the first metal oxide, and will not be repeated here.

[0127] The average particle size of single-crystal lithium transition metal oxides can be 2 μm, 3 μm, 4 μm, 5 μm or any value within the above range, and the average particle size of polycrystalline lithium transition metal oxides can be 9 μm, 10 μm, 12 μm, 15 μm or any value within the above range.

[0128] As an example, in the process of preparing the positive electrode, the volume average particle size Dv50 of the single-crystal lithium transition metal oxide added is 2μm to 5μm.

[0129] As an example, in the preparation of the positive electrode, the volume average particle size Dv50 of the polycrystalline lithium transition metal oxide added is 9 μm to 15 μm.

[0130] Lithium transition metal oxides can be layered lithium-containing transition metal oxides. Lithium 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, elements such as Zr and Al can be doped.

[0131] 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 positive electrode active materials listed in this application, the molar contents of Li represent the initial state of the material. When the positive electrode active material is applied to the battery system, the molar contents of Li will change after charge-discharge cycles. Furthermore, in the examples of positive electrode active materials listed in this application, the molar contents of O are only ideal values. Oxygen release from the crystal lattice will cause changes in the molar contents of O, and the actual molar contents of O will fluctuate.

[0132] In the above technical solution, the lithium transition metal oxide, the first metal oxide, and the second metal oxide have a better particle size distribution, which is beneficial to improving the first charge capacity and reliability of the battery cell.

[0133] In some embodiments, the molar ratio C of the first metal oxide and the second metal oxide satisfies: 1:1 ≤ C ≤ 10:1. When C ≥ 1:1, the first metal oxide has a higher proportion than the second metal oxide, which is beneficial to improving the first-cycle charging capacity of the battery cell; when C ≤ 10:1, the second metal oxide has a suitable proportion, which is beneficial to reducing the amount of gas generated in the battery cell.

[0134] In some embodiments, 1:1 ≤ C ≤ 3:1. For example, C is 1:1, 2:1, 3:1, or any value within the range described above.

[0135] By setting the ratio of 1:1 ≤ C ≤ 3:1, the second metal oxide has a higher mass content than the first metal oxide, which is beneficial for further reducing gas production in the battery cell. Thus, in battery cells including lithium transition metal oxides, this approach both reduces gas production and increases the initial charge capacity, achieving a better balance between gas production and initial charge capacity.

[0136] In some embodiments, the surface of the first metal oxide has a first surface material, the first surface material comprising an aluminum-containing compound and / or a carbon material; and / or, the surface of the second metal oxide has a second surface material, the second surface material comprising an aluminum-containing compound and / or a carbon material.

[0137] Aluminum-containing compounds and carbon materials can be applied as coating layers on the surfaces of the first metal oxide and the second metal oxide. For example, aluminum-containing compounds may coat part or all of the surfaces of the first metal oxide and the second metal oxide, and carbon materials may coat part or all of the surfaces of the first metal oxide and the second metal oxide.

[0138] The surface of the first metal oxide may be provided with one of an aluminum-containing compound and a carbon material, or both an aluminum-containing compound and a carbon material. The surface of the second metal oxide may be provided with one of an aluminum-containing compound and a carbon material, or both an aluminum-containing compound and a carbon material.

[0139] As an example, the surface of the first metal oxide is provided with an aluminum-containing compound and a carbon material, while the surface of the second metal oxide is not provided with an aluminum-containing compound and a carbon material. The carbon material can be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0140] Depositing carbon material on the surface of the first metal oxide and / or the second metal oxide helps reduce the agglomeration of the first metal oxide and / or the second metal oxide, reduces gas retention at the electrode, and reduces gas obstruction of lithium ion insertion into the negative electrode, thereby reducing the risk of lithium plating. Furthermore, it facilitates lithium ion extraction and increases the first-cycle charging capacity of the battery cell. Depositing aluminum-containing compounds on the surface of the first metal oxide and / or the second metal oxide helps improve the stability of the crystal structure of the first metal oxide and / or the second metal oxide.

[0141] In some embodiments, in the first metal oxide, based on the total mass of the first metal oxide, the mass content D1 of aluminum in the aluminum-containing compound satisfies: 0.1 wt% ≤ D1 ≤ 10 wt%, and / or, the mass content E1 of carbon in the carbon material satisfies: 0.1 wt% ≤ E1 ≤ 10 wt%; and / or, in the second metal oxide, based on the total mass of the second metal oxide, the mass content D2 of aluminum in the aluminum-containing compound satisfies: 0.1 wt% ≤ D2 ≤ 10 wt%, and / or, the mass content E2 of carbon in the carbon material satisfies: 0.1 wt% ≤ E2 ≤ 10 wt%.

[0142] D1 can be 0.1wt%, 1wt%, 2wt%, 5wt%, 8wt%, 10wt%, or any value within the above range, and E1 can be 0.1wt%, 1wt%, 2wt%, 5wt%, 8wt%, 10wt%, or any value within the above range.

[0143] D2 can be 0.1wt%, 1wt%, 2wt%, 5wt%, 8wt%, 10wt%, or any value within the above range, and E2 can be 0.1wt%, 1wt%, 2wt%, 5wt%, 8wt%, 10wt%, or any value within the above range.

[0144] In the above embodiments, by setting the mass content of aluminum and / or carbon to meet the above range, the battery cell has a more suitable first-cycle charging capacity and less gas production.

[0145] In some embodiments, 0.5wt% ≤ D1 ≤ 5wt%, and / or 0.5wt% ≤ E1 ≤ 5wt%; and / or 0.5wt% ≤ D2 ≤ 5wt%, and / or 0.5wt% ≤ E2 ≤ 5wt%. This results in a battery cell having a suitable initial charge capacity and less gas production.

[0146] In some embodiments, the first metal oxide includes one or more of Li5FeO4 or LiFeO2, and the second metal oxide includes one or more of Li2NiO2 or NiO2.

[0147] After a certain number of charge-discharge cycles, the first metal oxide can be delithiated to form LiFeO2, and the second metal oxide can be delithiated to form NiO2. If the first metal oxide is not completely consumed, there will be Li5FeO4 remaining, and if the second metal oxide is not completely consumed, there will be Li2NiO2 remaining.

[0148] In some embodiments, the volumetric particle size distribution Dv50 of the first metal oxide 1 Satisfies: 1μm≤Dv501 ≤20μm, and / or, the volumetric particle size distribution Dv90 of the first metal oxide 1 Satisfies: 15μm≤Dv90 1 ≤25μm, and / or, the volumetric particle size distribution Dv10 of the first metal oxide 1 Satisfies: 3μm≤Dv10 1 ≤7μm.

[0149] During the cycle of a battery cell (e.g., in a stage where the state of oxygen (SOH) of the battery cell is 70%–100%) or in a battery cell before formation, the Dv50 of the first metal oxide 1 Within the range of 1 μm to 20 μm, and / or, the Dv90 of the first metal oxide. 1 Within the range of 15 μm to 25 μm, and / or, the Dv10 of the first metal oxide. 1 Within the range of 3μm to 7μm.

[0150] Dv50 can refer to the particle size at which the cumulative particle size distribution number (DV50) of a sample reaches 50%, meaning that particles smaller than DV50 account for 50% of the total particle size distribution. Here, Dv50... 1 The superscript "1" is to correspond with Dv50 below. 2 To distinguish between different substances or different particles, indicating the volume and particle size distribution.

[0151] Dv90 can refer to the particle size corresponding to 90% of the cumulative particle size distribution number of a sample, which means that 90% of the particles are smaller than Dv90.

[0152] Dv10 can refer to the particle size corresponding to a sample when the cumulative particle size distribution number reaches 10%, which means that 10% of the particles are smaller than Dv10.

[0153] The volumetric particle size distribution of the first metal oxide, Dv50 1 It can be 1μm, 2μm, 5μm, 8μm, 10μm, 15μm, 20μm or any value within the above range.

[0154] The volumetric particle size distribution of the first metal oxide is Dv90. 1 It can be 15μm, 20μm, 25μm or any value within the above range.

[0155] The volumetric particle size distribution Dv10 of the first metal oxide 1 It can be 3μm, 4μm, 5.5μm, 6μm, 7μm or any value within the above range.

[0156] In the above embodiments, the first metal oxide has a more suitable particle size distribution, and when combined with the second metal oxide, it has a better effect. This is beneficial to further reduce the amount of gas generated by the battery cell during the aging stage after formation, reduce the risk of lithium plating in the battery cell, and improve the reliability of the battery cell.

[0157] In some embodiments, 5μm≤Dv50 1 ≤14μm, and / or, 16μm≤Dv90 1 ≤20μm, and / or, 4.5μm≤Dv10 1 ≤6μm. This helps to further reduce the amount of gas generated by battery cells during the aging stage after formation, reduce the risk of lithium plating in battery cells, and improve the reliability of battery cells.

[0158] In some embodiments, 5μm≤Dv90 1 -Dv50 1 ≤14μm, and / or, 2μm≤Dv50 1 -Dv10 1 ≤10μm.

[0159] Dv90 1 -Dv50 1 It can be 5μm, 8μm, 10μm, 12μm, 14μm or any value within the above range, Dv50 1 -Dv10 1 It can be 2μm, 3.5μm, 5μm, 8μm, 10μm or any value within the above range.

[0160] In the above embodiments, the particles of the first metal oxide are relatively uniform and have a suitable particle size distribution, and there is a good matching effect between the first and second metal oxides. This is beneficial to reduce the amount of gas generated by the battery cell during the aging stage after formation, reduce the risk of lithium plating in the battery cell, and improve the reliability of the battery cell.

[0161] In some embodiments, 5μm≤Dv90 1 -Dv50 1 ≤10μm, and / or, 2μm≤Dv50 1 -Dv10 1 ≤6μm. This helps to further reduce the amount of gas generated by battery cells during the aging stage after formation, reduce the risk of lithium plating in battery cells, and improve the reliability of battery cells.

[0162] In some embodiments, the volumetric particle size distribution of the first metal oxide is Dv99. 1 Satisfies: 20μm≤Dv99 1 ≤30μm.

[0163] Dv99 can refer to the particle size at which the cumulative particle size distribution number (CPD) of a sample reaches 99%, meaning that 99% of the particles are smaller than Dv99. Here, Dv99... 1 The superscript "1" is used to distinguish the volumetric particle size distribution Dv99 of the first metal oxide from the volumetric particle size distribution Dv99 of other substances.

[0164] The volumetric particle size distribution of the first metal oxide is Dv99. 1 It can be 20μm, 25μm, 30μm or any value within the above range.

[0165] In the above embodiments, the particle size distribution of the first metal oxide is Dv99. 1 Satisfies: 20μm≤Dv99 1 With a particle size of ≤30μm, the first metal oxide has a relatively uniform particle size distribution, which is beneficial to reducing the amount of gas generated in the battery cell.

[0166] In some embodiments, the quantity distribution Dn10 of the first metal oxide satisfies: 0.5μm≤Dn10≤1.0μm.

[0167] Dn10 can refer to the particle size corresponding to 10% of the cumulative particle size distribution of a sample, which means that particles smaller than Dn10 account for 10% of the total number of particles.

[0168] The quantity distribution Dn10 of the first metal oxide can be 0.5 μm, 0.6 μm, 0.8 μm, 1.0 μm or any value within the above range.

[0169] In the above embodiments, the first metal oxide has a suitable particle size, which is beneficial to reducing the amount of gas generated in the battery cell.

[0170] In some embodiments, the specific surface area S1 of the first metal oxide satisfies: 0.01 m² / s². 2 / g≤S1≤10m 2 / g, and / or, the specific surface area S2 of the second metal oxide satisfies: 0.01m 2 / g≤S2≤10m 2 / g.

[0171] The specific surface area of ​​the first metal oxide can be 0.01 m². 2 / g, 0.5m 2 / g、1m 2 / g、3m 2 / g、5m 2 / g, 10m 2 / g or any value within the above range, the second metal oxide can be 0.01m 2 / g, 0.1m 2 / g, 0.5m 2 / g、1m 2 / g、3m 2 / g、5m 2 / g or any value within the above range.

[0172] In the above embodiments, the first metal oxide and the second metal oxide have suitable specific surface areas, which are conducive to the diffusion of lithium ions, thereby helping to improve the first charge capacity of the battery cell.

[0173] In some embodiments, 0.5m 2 / g≤S1≤5m 2 / g, and / or, 0.1m 2 / g≤S2≤5m 2 / g. This helps to further improve the first-charge capacity of individual battery cells.

[0174] In some embodiments, the powder resistivity R1 of the first metal oxide at 20 MPa satisfies: R1 ≤ 25 Ω·cm.

[0175] R1 can be 25Ω·cm, 20Ω·cm, 15Ω·cm, 10Ω·cm, 8Ω·cm, 5Ω·cm, 4Ω·cm, 3Ω·cm, 2Ω·cm, 1Ω·cm, 0.5Ω·cm or any value within the above range.

[0176] In the above embodiments, the first metal oxide has high conductivity, which is beneficial to further improve the capacity of the battery cell.

[0177] In some embodiments, R1 ≤ 5 Ω·cm. This allows the first metal oxide to have higher conductivity, which is beneficial for further increasing the capacity of the battery cell.

[0178] In some embodiments, the volumetric particle size distribution Dv50 of the second metal oxide 2 Satisfies: 1μm≤Dv50 2 ≤50μm.

[0179] The volumetric particle size distribution of the second metal oxide, Dv50 2 It can be 1μm, 2μm, 5μm, 8μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm or any value within the above range.

[0180] After delithiation of the second metal oxide, the second metal oxide shrinks, and its particle size after delithiation is reduced by a certain proportion compared to its particle size before delithiation. In the embodiments of this application, the volumetric particle size distribution Dv50 of the second metal oxide is as follows during the cycle of a single battery cell. 2Within the range of 1μm to 50μm.

[0181] In Dv50 2 When the particle size is greater than or equal to 1 μm, the risk of agglomeration between the particles of the second metal oxide can be reduced, which is beneficial for a more uniform distribution of the second metal oxide in the positive electrode film layer and for the extraction of lithium ions; at Dv50 2 When the thickness is less than or equal to 50 μm, the path length for lithium ions to escape from the second metal oxide is more suitable, which is conducive to the extraction of lithium ions and thus helps to improve the capacity of the battery cell.

[0182] In the above embodiments, the second metal oxide has a suitable particle size, which facilitates the extraction of lithium ions, and the battery cell has a high first-cycle charging capacity.

[0183] In some embodiments, 10μm≤Dv50 2 ≤20μm. This helps to further improve the first-cycle charging capacity of individual battery cells.

[0184] 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, less gas production, and lower lithium plating risk. After the aging process, the smaller volume expansion is beneficial to improving the yield of 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 battery cells.

[0185] The embodiments of this application do not impose any particular restrictions on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape.

[0186] Figure 2 is a schematic diagram of a battery cell according to an embodiment of this application. For example, as shown in Figure 2, 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.

[0187] 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.

[0188] The end cap assembly 32 includes electrode terminals 322, as shown in FIG2. 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.

[0189] The battery cell 3 also includes a connecting member 34, which is used to connect the tabs 331 and the electrode terminals 322 of the electrode assembly 33.

[0190] 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.

[0191] [Positive electrode plate]

[0192] 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.

[0193] 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.).

[0194] 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.

[0195] 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.

[0196] [Negative electrode plate]

[0197] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on the negative current collector.

[0198] 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.).

[0199] 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.

[0200] 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), styrene-butadiene rubber, carboxymethyl cellulose, PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0201] 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.

[0202] [Electrolytes]

[0203] 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.

[0204] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0205] 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.

[0206] 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.

[0207] The electrolyte may also optionally include negative electrode film-forming additives, positive electrode film-forming additives, and performance additives that can improve certain battery performance, such as performance additives that improve battery overcharge performance, battery high temperature or low temperature performance, etc.

[0208] [Isolation Component]

[0209] The separator is used to separate the positive electrode and the negative electrode. This application does not impose any particular limitation on the type of separator; any known porous membrane with good chemical and mechanical stability can be selected.

[0210] 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; there are no particular restrictions. When the separator is a multi-layer composite film, the materials of each layer can be the same or different; there are no particular restrictions.

[0211] Positive electrode, negative electrode and separator can be made into electrode assembly by winding process or stacking process.

[0212] The embodiments of the battery cell have been described above with reference to Figures 1 and 2. The embodiments of the preparation method of the battery cell are described below with reference to Figure 3. Similar descriptions in the embodiments of the preparation method of the battery cell can be found in the descriptions of the embodiments of the battery cell, and will not be repeated below.

[0213] [Preparation methods for battery cells]

[0214] Figure 3 is a schematic diagram of a method for preparing a battery cell according to an embodiment of this application. Referring to Figure 3, the electrode preparation method 200 may include the following steps.

[0215] Step 210: Provide a positive electrode sheet to prepare a battery cell.

[0216] The provision of the positive electrode includes: mixing a first metal oxide and a second metal oxide to obtain a slurry for the positive electrode film, wherein the chemical formula of the first metal oxide satisfies: Li a1 M 1 O c1 , 0.2≤a1≤8.2, 1.8≤c1≤6.2, M 1 Including one or more of V, Nb, Cr, Mo, Fe, Co, or Sn; the chemical formula of the second metal oxide satisfies: Li a2 Ni 1-b M 2 b O c2 , 0≤a2≤2.2, 0≤b≤1, 0.8≤c2≤2.2, M 2comprising one or more of Cu, Mg, Zn, Mn, Al, Zr or Ti; the volume particle size distribution Dv50 of the first metal oxide 1 satisfies: 1μm ≤ Dv50 1 ≤ 20μm, and / or, the volume particle size distribution Dv90 of the first metal oxide 1 satisfies: 15μm ≤ Dv90 1 ≤ 25μm; Coating the slurry of the positive electrode film layer on the surface of at least one side of the current collector to provide the positive electrode sheet.

[0217] In the embodiments of the preparation method of the battery cell, the molar content of lithium element and the molar content of oxygen element are the contents at the time of feeding.

[0218] In 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 of the positive electrode film layer is obtained.

[0219] 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.

[0220] In some embodiments, after step 210, the positive electrode sheet, the negative electrode sheet, and the separator can also be made into an electrode assembly by winding or laminating, and then the electrode assembly is placed in a casing to prepare the battery cell.

[0221] In the preparation method of the battery cell in the embodiments of the present application, after the first metal oxide and the second metal oxide are mixed, not only can they play a good lithium supplementing role and improve the first-cycle charging capacity of the battery cell, but also they can reduce the gas generation in the aging stage after the battery cell is formed, reducing the gas generation amount in the battery cell. In addition, this preparation method does not require sintering treatment of the first metal oxide and the second metal oxide, and the preparation method is relatively simple and the preparation complexity is low.

[0222] In some embodiments, 2.8 ≤ a1 ≤ 8.2, 2.8 ≤ c1 ≤ 6.2, 1 < a2 ≤ 2.2, 0 < b ≤ 1, 1.8 ≤ c2 ≤ 2.2. When the molar contents of the elements of the first metal oxide and the second metal oxide satisfy the above ranges, more lithium ions can be released during the charge and discharge process of the battery cell to supplement active lithium ions to the battery cell.

[0223] In some embodiments, the first metal oxide includes one or more of Li3VO4, Li3NbO4, Li3CrO4, Li3MoO4, Li5FeO4, Li5CrO4, Li5VO4, Li5MoO4, Li6CoO4, Li6VO4, Li6CrO4, Li6MoO4 or Li8SnO6.

[0224] In some embodiments, the second metal oxide includes Li 1.8 NiO2, Li2NiO2, Li2Ni 0.5 Cu 0.5 O 2、 Li2Ni 0.5 Cu 0.5 O 2、 Li2Ni 0.5 Mn 0.5 O 2、 Li2Ni 0.5 Zr 0.5 O2, Li2Ni 0.5 Cu 0.5 O2 or Li2Ni 0.8 Cu 0.2 One or more of O2.

[0225] In some embodiments, the first metal oxide includes Li5FeO4, and the second metal oxide includes Li2NiO2. Li5FeO4 can release more lithium ions, and the combination of Li5FeO4 and Li2NiO2 can both improve the first-cycle charging capacity of the battery cell and reduce the gas production of the battery cell.

[0226] In some embodiments, 150μm 2 The ratio of the number of weak aggregates of the first metal oxide to the number of secondary particles of the first metal oxide is 50% to 100%, wherein the weak aggregates are secondary particles with a number of primary particles less than or equal to 10. This reduces the risk of interface problems and lithium plating caused by gas stagnation near the electrode in the battery cell, thus improving the reliability of the battery cell.

[0227] In some embodiments, the surface of the first metal oxide has a first surface material, the first surface material comprising an aluminum-containing compound and / or a carbon material; and / or, the surface of the second metal oxide has a second surface material, the second surface material comprising an aluminum-containing compound and / or a carbon material.

[0228] As an example, an aluminum-containing compound is deposited on the surface of a first metal oxide or a second metal oxide by atomic layer deposition (ALD). For example, the aluminum-containing compound may include aluminum oxide.

[0229] Depositing carbon materials on the surface of the first metal oxide and / or the second metal oxide helps reduce the agglomeration of the first metal oxide and / or the second metal oxide, reduces gas retention at the electrode, and lowers the risk of lithium plating. Furthermore, it facilitates lithium ion extraction and increases the first-cycle charging capacity of the battery cell. Depositing aluminum-containing compounds on the surface of the first metal oxide and / or the second metal oxide helps improve the stability of their crystal structure.

[0230] [Battery]

[0231] This application provides a battery, including the battery cells described in the above embodiments. The battery cells can be battery cells after formation and aging processes. Figure 4 is a schematic diagram of a battery according to an embodiment of this application. As shown in Figure 4, the battery 5 may include multiple battery cells (not shown in the figure).

[0232] 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.

[0233] [Electrical appliances]

[0234] This application provides an electrical device, including the battery described in the above embodiments.

[0235] In some embodiments, the electrical device includes an energy storage device or a truck. Energy storage devices and trucks have high requirements for the lifespan and long-term cycle performance of individual battery cells. Applying individual battery cells to the aforementioned electrical devices can improve the lifespan of the electrical devices.

[0236] Electrical devices can also be lighting devices, spacecraft, etc., and the embodiments of this application include, but are not limited to, these.

[0237] Figure 5 is a schematic diagram of an electrical device according to an embodiment of this application. As shown in Figure 5, this application provides an electrical device, which is a truck 6. As one example, the battery in the truck 6 can be replaced by a battery swapping device to replace a battery with insufficient power with a fully charged battery. As another example, the battery in the truck 6 can be charged by a charging device (e.g., a charging station).

[0238] Figure 6 is a schematic diagram of an electrical device according to an embodiment of this application. As shown in Figure 6, 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 to store and release electrical energy.

[0239] 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.

[0240] [Example]

[0241] Example 1

[0242] In Example 1, a positive electrode slurry was prepared by mixing a first metal oxide, a second metal oxide, a positive electrode active material, a conductive agent, a binder, and a solvent in a certain proportion. The positive electrode slurry was then coated on the surface of the positive electrode current collector to obtain a positive electrode sheet.

[0243] The first metal oxide comprises Li5FeO4, the surface of which is coated with carbon material and an aluminum-containing compound. Based on the total mass of the first metal oxide, the mass content of aluminum in the aluminum-containing compound, D1, is 1 wt%, and the mass content of carbon in the carbon material, E1, is 2.5 wt%. The second metal oxide comprises Li2NiO2. The molar ratio C of the first metal oxide and the second metal oxide is 5:1, and the volumetric particle size distribution Dv50 of the first metal oxide is... 1 It is 10.5μm, Dv90 1 It is 17.8μm, Dv10 1 The diameter is 5.2 μm, and the specific surface area S1 is 0.76 m². 2 / g, resistivity R1 is 0.662Ω·cm, and the volumetric particle size distribution Dv50 of the second metal oxide is... 2 It is 13.3μm, Dv90 1 33.1 μm, Dv10 1 Its diameter is 4.2 μm, and its specific surface area S2 is 0.28 m². 2 / g; The positive electrode active material includes lithium iron phosphate, and the volumetric particle size distribution of the positive electrode active material is Dv50. 4 The thickness is 1 μm. Based on the total mass of the first metal oxide, the second metal oxide, and the positive electrode active material, the ratio of the total mass of the first metal oxide and the second metal oxide to the mass of the positive electrode active material is 1:35.

[0244] Examples 2-4

[0245] The difference between Examples 2-4 and Example 1 is that the molar ratio C of the first metal oxide and the second metal oxide is different.

[0246] Example 5

[0247] The difference between Example 5 and Example 1 is that the volumetric particle size distribution Dv50 of the first metal oxide is... 1 Dv90 1 and Dv10 1 different.

[0248] Comparative Example 1

[0249] The difference between Comparative Example 1 and Example 1 is that only the first metal oxide is added to the positive electrode, and the second metal oxide is not added.

[0250] Comparative Example 2

[0251] The difference between Comparative Example 2 and Example 1 is that the first metal oxide has a volumetric particle size distribution Dv50. 1 It is 28.9μm, Dv90 1 It is 51.2 μm, Dv10 1 It is 14.3 μm.

[0252] Table 1 shows the specific parameters of the first and second metal oxides during the preparation of the positive electrode sheet. Table 2 shows the relevant test results of the battery cells. Table 3 shows the relevant parameters of the positive electrode sheets in the battery cells of Example 1 and Comparative Example 2 after disassembly. In Table 3, A1 represents the ratio of the number of primary particles with a particle size of 5μm to 15μm of the first metal oxide to the total number of primary particles of the first metal oxide; A2 represents the ratio of the number of primary particles with a particle size of 5μm to 11μm to the total number of primary particles of the first metal oxide; A3 represents the ratio of the number of weak aggregates to the number of secondary particles; and A4 represents the average particle size of the first metal oxide. Table 1 Specific parameters of Examples 1-5 and Comparative Examples 1-2 Table 2 Test results of Examples 1-5 and Comparative Examples 1-2 Table 3. Relevant parameters of Example 1 and Comparative Example 2

[0253] Referring to Table 3, the battery cells corresponding to Example 1 after the aging and gas generation test were disassembled, and the positive electrode was tested. The specific test results are as follows: The ratio of the number of primary particles with a particle size of 5μm to 15μm to the total number of primary particles of the first metal oxide was 89%, the ratio of the number of primary particles with a particle size of 5μm to 11μm to the total number of primary particles of the first metal oxide was 72%, the ratio of the number of weak aggregates to the number of secondary particles was 100%, and the average particle size of the first metal oxide was 8μm.

[0254] Referring to Table 3, the battery cells of Comparative Example 2 were disassembled after the aging and gas generation test, and the positive electrode was tested. The specific test results are as follows: The ratio of the number of primary particles with a particle size of 5μm to 15μm to the total number of secondary particles of the first metal oxide was 18%; the ratio of the number of primary particles with a particle size of 5μm to 11μm to the total number of primary particles of the first metal oxide was 9%; the ratio of the number of weak aggregates to the number of secondary particles was 5%; and the average particle size of the first metal oxide was 23μm.

[0255] [Preparation of battery cells]

[0256] (1) Preparation of the positive electrode sheet:

[0257] A mixture of a first metal oxide and a second metal oxide, along with a positive electrode active material, is mixed at a mass ratio of 1:35 to obtain the positive electrode material. The mixed positive electrode material, along with the binder polyvinylidene fluoride (PVDF) and the conductive agent (carbon black), are then mixed uniformly at a mass ratio of 97:2:1 and dissolved in the solvent N-methylpyrrolidone (NMP). After thorough mixing, a positive electrode slurry is prepared. This slurry is then uniformly coated onto two opposite surfaces of a positive electrode current collector aluminum foil. Following drying, cold pressing, and slitting, a positive electrode sheet is obtained, with a compaction density of 2.4 g / cm³. 3 (This compaction density is the compaction density before formation).

[0258] (2) Preparation of the negative electrode sheet: The negative electrode active material artificial graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC-Na) were dissolved in deionized water at a mass ratio of 96:1.5:1.5:1.0 and thoroughly mixed to prepare a negative electrode slurry. The negative electrode slurry was coated onto the negative electrode current collector copper foil, and then dried, cold-pressed, and slit to obtain the negative electrode sheet, wherein the compacted density of the negative electrode sheet was 1.6 g / cm³. 3 (This compaction density is the compaction density before formation).

[0259] (3) Separation membrane: A polyethylene membrane with a thickness of 13μm is used.

[0260] (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.

[0261] (5) Preparation of lithium-ion battery: The above positive electrode sheet, separator and negative electrode sheet are stacked and wound in sequence to obtain an electrode assembly; the electrode assembly is placed in the shell, the electrolyte prepared above is added, and after encapsulation, standing, formation and aging processes, a battery cell is obtained.

[0262] [First Charging Capacity Test]

[0263] 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 C0. Divide the charging capacity C0 by the total mass of the first metal oxide, the second metal oxide, and the positive electrode active material to obtain the specific capacity Q0 of the first charge cycle.

[0264] [Test of gas production during aging]

[0265] 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, as an example, the volume before and after standing was measured using the water displacement method, and the gas production was 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.

[0266] [Lithium plating test]

[0267] After the aging and gas production test is completed, the battery cells are disassembled, and the surface of the negative electrode is observed to see if lithium plating occurs. Slight lithium plating is considered when the total area of ​​black spots on the negative electrode is between 0% and 20% of the total area, while severe lithium plating is considered when the total area of ​​black spots on the negative electrode is between 70% and 100% of the total area.

[0268] [Identification of the first and second metal oxides]

[0269] The positive electrode sheet of the battery cell was taken as a sample, and the positive electrode sheet was subjected to ion polishing (CP) along the extension direction of the positive electrode sheet (which is perpendicular to the thickness direction of the positive electrode sheet). The positive electrode sheet was then analyzed and tested using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).

[0270] Specifically, after the positive electrode sheet undergoes CP treatment, it is observed using a scanning electron microscope (SEM). This allows for the observation of the number and size of particles within the positive electrode sheet, enabling the differentiation of the positive electrode active material, the first metal oxide, and the second metal oxide based on particle size. Furthermore, energy-dispersive X-ray spectroscopy (EDS) can be used to analyze the elemental composition of the particles in the positive electrode sheet, further distinguishing the positive electrode active material, the first metal oxide, and the second metal oxide based on elemental composition.

[0271] (1) Analysis and testing of positive electrode sheets including lithium iron phosphate

[0272] In one example, during the preparation of the positive electrode, the positive active material is lithium iron phosphate, the first metal oxide is Li5FeO4, and the second metal oxide is Li2NiO2. The testing of the positive electrode will be explained using this example.

[0273] The particle size of the first metal oxide, the particle size of the second metal oxide, and the particle size of the positive electrode active material lithium iron phosphate are significantly different. The particle size of the first metal oxide and the second metal oxide are larger than that of the positive electrode active material lithium iron phosphate. The positive electrode active material can be distinguished from the first metal oxide and the second metal oxide by the particle size.

[0274] Figure 7 is a SEM schematic diagram of the positive electrode sheet according to an embodiment of this application. Figure 7 is a SEM schematic diagram of the positive electrode sheet before formation after cold pressing. As shown in Figure 7, the particle size of lithium iron phosphate is clearly distinguishable from the particle sizes of the first metal oxide and the second metal oxide.

[0275] It should be noted that after a single battery cell undergoes formation and a certain number of charge-discharge cycles, the particles of the first and second metal oxides will shrink. For example, within 1000 cycles, the shrinkage ratio of the first and second metal oxide particles is approximately in the range of 20% to 50%.

[0276] Before and after formation, the particle sizes of the first and second metal oxides are significantly different from those of the positive electrode active material.

[0277] For example, in the SEM image of the positive electrode, take an appropriate size (e.g., 500 μm). 2 The particle size of the region was statistically analyzed, and particles smaller than 3 μm were identified as lithium iron phosphate. The number and size of the remaining particles were then counted. EDS elemental analysis was performed on the remaining particles; particles containing Fe were labeled as first metal oxides, and particles containing Ni were labeled as second metal oxides. The size of each first metal oxide particle was then calculated, and the average particle size was determined.

[0278] (2) Analysis and testing of positive electrode sheets including ternary materials

[0279] In another example, during the preparation of the positive electrode, the positive electrode active material is the ternary material LiNi. 0.6 Co 0.2 Mn 0.2 The first metal oxide is Li5FeO4, and the second metal oxide is Li2NiO2. The testing of the positive electrode is illustrated using this positive electrode as an example.

[0280] In the SEM image of the positive electrode, take an appropriate size (e.g., 500 μm). 2 The region was statistically analyzed. EDS analysis was performed on each particle; particles detecting Fe were labeled as first metal oxides, particles detecting Mn were labeled as positive electrode active materials, and the remaining particles were labeled as second metal oxides. The size of each first metal oxide particle was statistically analyzed, and the average particle size was calculated.

[0281] It should be understood that, in addition to EDS (Electrode Sequencing), other methods can be used for elemental analysis. For example, the positive electrode film can be scraped off from the positive electrode sheet, and the scraped material can be added to aqua regia and digested under mechanical stirring for 30 minutes. The digested solution can then be added to an ICAP7400 spectrometer to analyze its elemental composition. When the positive electrode active material is lithium iron phosphate, the presence of Li₂NiO₂ in the pre-formation positive electrode film can be determined by detecting Ni. When the positive electrode active material is a ternary material, the presence of Li₅FeO₄ in the pre-formation positive electrode film can be determined by detecting Fe.

[0282] [Average particle size test]

[0283] Taking the first metal oxide as an example, the testing of particle size and average particle size is explained. The testing methods for the particle size and average particle size of the second metal oxide and the positive electrode active material can refer to the testing methods for the particle size and average particle size of the first metal oxide.

[0284] The particle size of the first metal oxide can be the maximum particle size of the first metal oxide. For example, the size of the first metal oxide particles (e.g., primary or secondary particles of the first metal oxide) is measured in three mutually perpendicular directions, and the largest size is taken as the particle size of the first metal oxide.

[0285] The average particle size of the first metal oxide can be the average particle size of the particles of the first metal oxide. Specifically, a region of a suitable size (e.g., 20 μm × 20 μm) is selected, and the number and size of primary particles and the number and size of secondary particles are counted within this region (e.g., primary and secondary particles falling at the boundary of the region are not counted). The average particle size is the ratio of the sum of the particle sizes of all primary particles and all secondary particles to the sum of the number of primary and secondary particles.

[0286] [Specific Surface Area Test]

[0287] After measuring the amount of gas adsorbed on the solid surface at a pressure of 20 MPa under constant temperature, the amount of monolayer adsorption of the sample was obtained based on the Brown-Etter-Taylor (BET) multilayer adsorption theory and its formula, thereby calculating the specific surface area of ​​the solid.

[0288] [Test of volumetric particle size distribution]

[0289] The volumetric particle size distribution can be determined using a particle size analyzer-laser diffraction method. Specifically, refer to standard GB / T19077-2016, using a laser diffraction scattering particle size analyzer, and perform measurements according to the manufacturer's instructions. For example, take an appropriate amount of sample (first metal oxide, second metal oxide, or positive electrode active material). The sample can be obtained directly from powder (e.g., self-made or purchased) or from powder obtained through disassembly of battery products. Use a Malvern 2000 (MasterSizer 2000) laser particle size analyzer to test the average volumetric particle size of the sample material. Take an appropriate amount of the sample to be tested (the sample concentration should be 8-12% opacity), add 20 ml of deionized water, and simultaneously incubate for 5 minutes (53 kHz / 120 W) to ensure complete dispersion of the sample. Then, measure the sample according to GB / T19077-2016 / ISO 13320:2009 standard.

[0290] [Resistivity Test]

[0291] Weigh an appropriate amount of lithium replenishment 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 replenishment material for lithium-ion batteries" with a test pressure of 20MPa.

[0292] Figure 8 is a SEM image of the first metal oxide of one embodiment of this application, Figure 9 is a SEM image of the first metal oxide of one embodiment of this application, and Figure 10 is a SEM image of the first metal oxide of a comparative example of this application. Referring to Figures 8 to 10, compared to the comparative example, the first metal oxide in the embodiments of this application exhibits less particle aggregation and a higher proportion of primary particles with a particle size within a suitable range.

[0293] As shown in Example 1 and Comparative Example 1, compared to adding only the first metal oxide, adding both the first metal oxide and the second metal oxide can increase the first charge capacity of the battery cell while reducing gas generation in the aging stage after formation, thus reducing the risk of lithium plating.

[0294] As shown in Example 1 and Comparative Example 2, the ratio of the number of primary particles of the first metal oxide with a particle size of 5 μm to 15 μm to the total number of primary particles of the first metal oxide is in the range of 40% to 90%, and 150 μm... 2 When the ratio of the number of weak aggregates of the first metal oxide to the number of secondary particles of the first metal oxide is in the range of 50% to 100%, the battery cell produces less gas during the aging process and has a lower risk of lithium plating.

[0295] As shown in Examples 1-4, setting the molar ratio C of the first metal oxide to the second metal oxide to be 1:1 to 10:1 is beneficial to reduce gas production in the aging stage after formation of the battery cell while increasing the first charge capacity of the battery cell. Furthermore, setting C to 3:1 to 5:1 is beneficial to further balance the gas production in the aging stage after formation of the battery cell and the first charge capacity of the battery cell.

[0296] Based on Examples 1 and 5, and Comparative Example 2, selecting a first metal oxide with a suitable particle size distribution results in less gas generation during the aging process of the battery cells, a lower risk of interface problems, and a lower risk of lithium plating. The volumetric particle size distribution Dv50 of the first metal oxide... 1 Satisfies: 1μm≤Dv50 1 ≤20μm, the volumetric particle size distribution of the first metal oxide is Dv90 1 Satisfies: 15μm≤Dv90 1 ≤25μm, the volumetric particle size distribution Dv10 of the first metal oxide 1 Satisfies: 3μm≤Dv10 1 ≤7μm, the battery cell has a low gas production; the volumetric particle size distribution of the first metal oxide is Dv50. 1 Satisfies: 5μm≤Dv50 1≤14μm, the volumetric particle size distribution of the first metal oxide is Dv90 1 Satisfies: 16μm≤Dv90 1 ≤20μm, the volumetric particle size distribution Dv10 of the first metal oxide 1 Satisfies: 4.5μm≤Dv10 1 With a thickness of ≤6μm, the battery cells produce less gas and virtually no lithium plating occurs.

[0297] 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 and a second metal oxide; The chemical formula of the first metal oxide satisfies: Li a1 M 1 O c1 , 0.2≤a1≤8.2, 1.8≤c1≤6.2, M 1 Including one or more of V, Nb, Cr, Mo, Fe, Co, or Sn; The chemical formula of the second metal oxide satisfies: Li a2 Ni 1-b M 2 b O c2 , 0≤a2≤2.2, 0≤b≤1, 0.8≤c2≤2.2, M 2 Including one or more of Cu, Mg, Zn, Mn, Al, Zr, or Ti; The ratio of the number of primary particles of the first metal oxide with a particle size of 5 μm to 15 μm to the total number of primary particles of the first metal oxide is 40% to 90%.

2. The battery cell according to claim 1, characterized in that, The ratio of the number of primary particles of the first metal oxide with a particle size of 5 μm to 11 μm to the total number of primary particles of the first metal oxide is 50% to 80%.

3. The battery cell according to claim 1 or 2, characterized in that, 150μm 2 The ratio of the number of weak aggregates of the first metal oxide to the number of secondary particles of the first metal oxide is 50% to 100%, wherein the weak aggregates are secondary particles with a number of primary particles less than or equal to 10.

4. The battery cell according to claim 3, characterized in that, 150μm 2 The ratio of the number of weak aggregates of the first metal oxide to the number of secondary particles of the first metal oxide is 80% to 100%.

5. The battery cell according to any one of claims 1-4, characterized in that, The average particle size of the first metal oxide is 5 μm to 15 μm, and / or the maximum particle size of the first metal oxide is 20 μm to 30 μm, and / or the minimum particle size of the first metal oxide is 3.5 μm to 6 μm.

6. The battery cell according to any one of claims 1-5, characterized in that, The average particle size of the second metal oxide is 10 μm to 20 μm.

7. The battery cell according to any one of claims 1-6, characterized in that, The positive electrode film layer further includes a positive electrode active material. Based on the total mass of the first metal oxide, the second metal oxide, and the positive electrode active material, the mass content P of the positive electrode active material satisfies: 90wt% ≤ P ≤ 99wt%.

8. The battery cell according to claim 7, characterized in that, The positive electrode active material includes lithium phosphate, and the average particle size of the lithium phosphate is smaller than the average particle size of the first metal oxide or the average particle size of the second metal oxide.

9. The battery cell according to claim 8, characterized in that, The average particle size of the lithium phosphate is 0.5 μm to 3 μm.

10. The battery cell according to claim 8 or 9, characterized in that, The molar ratio C of the first metal oxide and the second metal oxide satisfies: 1:1≤C≤10:

1.

11. The battery cell according to claim 10, characterized in that, 3:1≤C≤5:1。 12. The battery cell according to claim 7, characterized in that, The positive electrode active material includes lithium transition metal oxide, which includes at least one of single-crystal lithium transition metal oxide or polycrystalline lithium transition metal oxide. The average particle size of the single-crystal lithium transition metal oxide is 2 μm to 5 μm, and the average particle size of the polycrystalline lithium transition metal oxide is 9 μm to 15 μm.

13. The battery cell according to claim 12, characterized in that, The molar ratio C of the first metal oxide and the second metal oxide satisfies: 1:1≤C≤10:

1.

14. The battery cell according to claim 13, characterized in that, 1:1≤C≤3:1。 15. The battery cell according to any one of claims 1-14, characterized in that, The surface of the first metal oxide has a first surface material, which includes an aluminum-containing compound and / or a carbon material; And / or, The surface of the second metal oxide has a second surface material, which includes an aluminum-containing compound and / or a carbon material.

16. The battery cell according to claim 15, characterized in that, In the first metal oxide, based on the total mass of the first metal oxide, the mass content D1 of aluminum in the aluminum-containing compound satisfies: 0.1wt% ≤ D1 ≤ 10wt%, and / or, the mass content E1 of carbon in the carbon material satisfies: 0.1wt% ≤ E1 ≤ 10wt%. And / or, In the second metal oxide, based on the total mass of the second metal oxide, the mass content D1 of aluminum in the aluminum-containing compound satisfies: 0.1wt% ≤ D2 ≤ 10wt%, and / or, the mass content E1 of carbon in the carbon material satisfies: 0.1wt% ≤ E2 ≤ 10wt%.

17. The battery cell according to claim 16, characterized in that, 0.5wt%≤D1≤5wt%, and / or, 0.5wt%≤E1≤5wt%; And / or, 0.5wt% ≤ D2 ≤ 5wt%, and / or, 0.5wt% ≤ E2 ≤ 5wt%.

18. The battery cell according to any one of claims 1-17, characterized in that, The first metal oxide includes one or more of Li5FeO4 or LiFeO2, and the second metal oxide includes one or more of Li2NiO2 or NiO2.

19. The battery cell according to any one of claims 1-18, characterized in that, The volumetric particle size distribution Dv50 of the first metal oxide 1 Satisfies: 1μm≤Dv50 1 ≤20μm, and / or, the volumetric particle size distribution Dv90 of the first metal oxide 1 Satisfies: 15μm≤Dv90 1 ≤25μm, and / or, the volumetric particle size distribution Dv10 of the first metal oxide 1 Satisfies: 3μm≤Dv10 1 ≤7μm.

20. The battery cell according to claim 19, characterized in that, 5μm≤Dv50 1 ≤14μm, and / or, 16μm≤Dv90 1 ≤20μm, and / or, 4.5μm≤Dv10 1 ≤6μm.

21. The battery cell according to claim 19 or 20, characterized in that, 5μm≤Dv90 1 -Dv50 1 ≤14μm, and / or, 2μm≤Dv50 1 -Dv10 1 ≤10μm.

22. The battery cell according to claim 21, characterized in that, 5μm≤Dv90 1 -Dv50 1 ≤10μm, and / or, 2μm≤Dv50 1 -Dv10 1 ≤6μm.

23. The battery cell according to any one of claims 1-22, characterized in that, The volumetric particle size distribution of the first metal oxide is Dv99. 1 Satisfies: 20μm≤Dv99 1 ≤30μm.

24. The battery cell according to any one of claims 1-23, characterized in that, The quantity distribution Dn10 of the first metal oxide satisfies: 0.5μm≤Dn10≤1.0μm.

25. The battery cell according to any one of claims 1-24, characterized in that, The specific surface area of ​​the first metal oxide is 0.01 m². 2 / g≤S1≤10m 2 / g, and / or, the specific surface area S2 of the second metal oxide satisfies: 0.01m 2 / g≤S2≤10m 2 / g.

26. The battery cell according to claim 25, characterized in that, 0.5m 2 / g≤S1≤5m 2 / g, and / or, 0.1m 2 / g≤S2≤5m 2 / g.

27. The battery cell according to any one of claims 1-26, characterized in that, The powder resistivity R1 of the first metal oxide at 20 MPa satisfies: R1≤25Ω·cm.

28. The battery cell according to claim 27, characterized in that, R1≤5Ω·cm.

29. The battery cell according to any one of claims 1-28, characterized in that, The volumetric particle size distribution Dv50 of the second metal oxide 2 Satisfies: 1μm≤Dv50 2 ≤50μm.

30. The battery cell according to claim 29, characterized in that, 10μm <Dv50 2 ≤20μm.

31. 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: A first metal oxide and a second metal oxide are mixed to obtain a slurry for the positive electrode film, wherein the chemical formula of the first metal oxide satisfies: Li a1 M 1 O c1 , 0.2≤a1≤8.2, 1.8≤c1≤6.2, M 1 Including one or more of V, Nb, Cr, Mo, Fe, Co, or Sn; The chemical formula of the second metal oxide satisfies: Li a2 Ni 1-b M 2 b O c2 , 0≤a2≤2.2, 0≤b≤1, 0.8≤c2≤2.2, M 2 Including one or more of Cu, Mg, Zn, Mn, Al, Zr, or Ti; The volumetric particle size distribution Dv50 of the first metal oxide 1 Satisfies: 1μm≤Dv50 1 ≤20μm, and / or, the volumetric particle size distribution Dv90 of the first metal oxide 1 Satisfies: 15μm≤Dv90 1 ≤25μm; The slurry of the positive electrode film is coated on at least one side of the current collector to provide the positive electrode sheet.

32. The preparation method according to claim 31, characterized in that, 2.8≤a1≤8.2, 2.8≤c1≤6.2, 1 <a2≤2.2,0<b≤1,1.8≤c2≤2.2。 33. The preparation method according to claim 31 or 32, characterized in that, The first metal oxide includes Li5FeO4, and the second metal oxide includes Li2NiO2.

34. The preparation method according to any one of claims 31-33, characterized in that, 150μm 2 The ratio of the number of weak aggregates of the first metal oxide to the number of secondary particles of the first metal oxide is 50% to 100%, wherein the weak aggregates are secondary particles with a number of primary particles less than or equal to 10.

35. An electrical appliance, characterized in that, include: The battery cell according to any one of claims 1-30, and / or the battery cell obtained by the preparation method according to any one of claims 31-34.

36. The electrical appliance according to claim 35, characterized in that, The electrical equipment includes energy storage devices or trucks.

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