Battery cell, battery apparatus, and electric device

Abstract

A battery cell, a battery apparatus, and an electric device, relating to the technical field of batteries. The battery cell comprises: a positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector, wherein the positive electrode film layer comprises a lithium-containing phosphate, a first additive, and a second additive, the first additive comprises a lithium-containing transition metal oxide, and the second additive comprises a nickel-containing metal oxide; a negative electrode sheet, comprising a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector, wherein the negative electrode film layer comprises graphite; and an electrolyte, comprising a chain carboxylic acid ester solvent, wherein the mass content of the chain carboxylic acid ester solvent is 32%-60% on the basis of the total mass of the electrolyte. The technical solution of the present application can reduce the gas production of the battery cell so as to improve the cycle performance of the battery cell, and the battery cell also has good fast charge performance.

Description

Battery cells, battery devices, electrical equipment Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a battery cell, a battery device, and an electrical appliance. Background Technology

[0002] With increasing environmental pollution, the new energy industry is attracting more and more attention. Within the new energy industry, battery technology is a crucial factor in its development.

[0003] The development of battery technology requires consideration of various design factors, such as energy density, cycle life, service life, capacity, fast charging performance, and reliability. How to provide a battery cell with good fast charging performance and long cycle life is a technical problem that urgently needs to be solved. Summary of the Invention

[0004] This application is made in view of the above-mentioned issues, and its purpose is to provide a battery cell with better fast charging performance and long cycle life.

[0005] To achieve the above objectives, this application provides a battery cell, a battery device, and an electrical appliance.

[0006] 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 disposed on at least one side of the positive current collector, the positive electrode film layer including lithium phosphate, a first additive and a second additive, the first additive including a lithium transition metal oxide and the second additive including a nickel metal oxide; a negative electrode sheet, including a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, the negative electrode film layer including graphite; and an electrolyte including a chain-like carboxylic acid ester solvent, wherein the mass content of the chain-like carboxylic acid ester solvent is 32%-60% based on the total mass of the electrolyte.

[0007] In this embodiment, the positive electrode includes a first additive and a second additive, and the electrolyte includes a chain-like carboxylic acid ester solvent. The first additive includes a lithium-containing transition metal oxide, and the second additive includes a nickel-containing metal oxide. The first additive releases lithium ions to compensate for the loss of active lithium in the battery cell during cycling, thereby improving the cycle performance of the battery cell. The chain-like carboxylic acid ester solvent helps improve the conductivity of the electrolyte to meet the fast-charging performance of the battery cell. The second additive promotes the rapid conversion of oxygen free radicals generated by the delithiation of the first additive into oxygen, reducing the subsequent side reactions of organic fragments RH+ generated by oxygen free radicals at the negative electrode to generate hydrogen gas, thus reducing the corrosion of the SEI film by RH+ and improving the cycle performance of the battery cell. In other words, by using the first additive, the second additive, and the chain-like carboxylic acid ester solvent, the gas production of the battery cell can be reduced and the cycle performance of the battery cell can be improved in a highly conductive electrolyte system.

[0008] In some possible implementations, the average longest diameter of the lithium-containing transition metal oxide is 8 μm-30 μm on a longitudinal section along the thickness direction of the positive electrode sheet.

[0009] In this embodiment, by making the average length of the lithium-containing transition metal oxide greater than or equal to 8 μm, the degree of side reactions occurring in the battery cell can be reduced, thereby improving the cycle performance of the battery cell; by making the average length of the lithium-containing transition metal oxide less than or equal to 30 μm, it is conducive to the insertion and extraction of lithium ions, thereby balancing the capacity and cycle performance of the battery cell.

[0010] In some possible implementations, the average longest diameter of the nickel-containing metal oxide is 7 μm-20 μm on a longitudinal section along the thickness direction of the positive electrode sheet.

[0011] In this embodiment, by making the average length of the nickel-containing metal oxide greater than or equal to 7 μm, the degree of side reactions of the nickel-containing metal oxide in the battery cell can be reduced, thereby improving the film quality of the SEI film; by making the average length of the nickel-containing metal oxide less than or equal to 20 μm, the contact area between the nickel-containing metal oxide and other substances can be increased, promoting the conversion of oxygen free radicals, thereby reducing the gas production of the battery cell.

[0012] In some possible implementations, the lithium-containing transition metal oxide comprises a substrate and a coating layer located on at least a portion of the surface of the substrate, the substrate comprising Li x1 N y1 O z1 Where 1≤x1≤6, 1≤y1≤3, 1≤z1≤6, and N includes at least one of Ni, Fe, Cu, Co, Mn, Al, and Na.

[0013] In this embodiment, the lithium transition metal oxide includes a substrate and a coating layer, wherein the substrate has the general formula Li. x1 N y1 O z1 1≤x1≤6, 1≤y1≤3, 1≤z1≤6, N includes at least one of Ni, Fe, Cu, Co, Mn, Al, and Na. Such lithium-containing transition metal oxides can provide active lithium to compensate for lithium loss in battery cells during cycling.

[0014] In some possible implementations, the matrix comprises Li5FeO4.

[0015] In this embodiment, Li5FeO4 is added as a first additive to the positive electrode film layer of the battery cell. The lithium ions released from it can compensate for the lithium loss of the battery cell, thereby improving the initial efficiency and energy density of the battery cell.

[0016] In some possible implementations, the matrix comprises Li e FeO f ,0≤e≤5,0 <f≤4。

[0017] In this embodiment of the application, during the formation stage of the battery cell, the matrix of the first additive decomposes, generating oxygen free radicals while producing lithium ions, and the molar content of Li and O elements changes.

[0018] In some possible implementations, the matrix comprises Li h FeO n ,0≤h≤1,0 <n≤2。

[0019] In the embodiments of this application, during the formation process of the battery cell, the matrix decomposes, generating oxygen free radicals while producing lithium ions, and the molar content of Li and O elements changes.

[0020] In some possible implementations, the coating layer includes at least one of C, Al, Zr, Si, B, S, and P.

[0021] In this embodiment, the first additive includes a matrix and a coating layer. The coating layer includes at least one of C, Al, Zr, Si, B, S, and P. The coating layer can reduce the probability of the matrix being in direct contact with air, reduce the probability of the matrix reacting with water and carbon dioxide in the air, improve the air stability of the matrix, and reduce the formation of impurity lithium on the matrix surface. At the same time, it can improve the conductivity of the matrix and improve the utilization rate of active lithium ions.

[0022] In some possible implementations, the thickness of the coating layer is 10 nm to 100 nm.

[0023] In this embodiment, by making the thickness of the coating layer 10nm-100nm, the coating layer has a reasonable thickness, which helps the extraction and insertion of lithium ions, thereby improving the ionic conductivity of the first additive and the kinetic performance of the battery cell.

[0024] In some possible implementations, the nickel-containing metal oxide includes M m NiO d M includes at least one of Li, Na, and K, 0≤m≤2, 1≤d≤2.

[0025] In this embodiment, the first additive generates oxygen free radicals while replenishing active lithium. This is achieved by adding a second additive, comprising a nickel-containing metal oxide, to the positive electrode film layer, wherein the general formula of the nickel-containing metal oxide is M. m NiO d M includes at least one of Li, Na, and K, 0≤m≤2, 1≤d≤2. Such nickel-containing metal oxides can rapidly convert the oxygen free radical intermediates generated by the first additive into oxygen, reduce the residence time of oxygen free radicals, and thus reduce the damage to the electrolyte and SEI film components, which helps to improve the stability of the negative electrode film formation and improve the cycle performance of the battery cell.

[0026] In some possible implementations, the nickel-containing metal oxide includes Li2NiO2.

[0027] In this embodiment, Li2NiO2 is added as a second additive to the positive electrode film layer of the battery cell, which can effectively convert oxygen free radicals and reduce the impact of oxygen free radicals on the electrolyte and SEI film.

[0028] In some possible implementations, the nickel-containing metal oxide includes Li g NiO i ,0≤g≤2,0 <i≤2。

[0029] In this embodiment of the application, during the formation process of the battery cell, the nickel-containing metal oxide decomposes, and the molar content of lithium and oxygen will change to a certain extent.

[0030] In some possible implementations, the nickel-containing metal oxide includes NiO. q 0 <q≤2。

[0031] In this embodiment of the application, during the formation process of the battery cell, the nickel-containing metal oxide decomposes, and the molar content of oxygen element will change to a certain extent.

[0032] In some possible implementations, the ratio of the mass content of the nickel-containing metal oxide to the mass content of the lithium-containing transition metal oxide is 0.1-0.4.

[0033] In this embodiment, by setting the mass ratio of nickel-containing metal oxide to lithium-containing transition metal oxide to 0.1-0.4, the nickel-containing metal oxide can more thoroughly convert the oxygen free radicals generated by the lithium-containing transition metal oxide, thereby reducing the gas production of the battery cell and improving the cycle performance of the battery cell.

[0034] In some possible implementations, the mass ratio of the nickel-containing metal oxide to the lithium-containing transition metal oxide is 0.15-0.25.

[0035] In this embodiment, by setting the mass ratio of nickel-containing metal oxide to lithium-containing transition metal oxide to 0.15-0.25, the nickel-containing metal oxide can more thoroughly convert the oxygen free radicals generated by the lithium-containing transition metal oxide, which helps to further reduce the gas production of the battery cell and improve the cycle performance of the battery cell.

[0036] In some possible implementations, the lithium phosphate content is 80%-97% based on the total mass of the positive electrode film.

[0037] In this embodiment, the mass content of lithium phosphate in the positive electrode film layer is 80%-97%, which can ensure that the battery cell 3 has a high energy density and capacity.

[0038] In some possible implementations, the mass content of the lithium-containing transition metal oxide is 0.1%-5% based on the total mass of the positive electrode film.

[0039] In this embodiment of the application, the mass content of lithium transition metal oxide in the positive electrode film layer is 0.1%-5%. This mass content of the first additive can compensate for a large number of lithium ions without generating a large number of oxygen free radicals, which helps to improve the overall performance of the battery cell.

[0040] In some possible implementations, the mass content of the nickel-containing metal oxide is 0.03%-2% based on the total mass of the positive electrode film.

[0041] In this embodiment of the application, the mass content of nickel metal oxide in the positive electrode film is 0.03%-2%, and the second additive with this mass content can more thoroughly convert the oxygen free radicals generated by the first additive.

[0042] In one possible implementation, the specific charging capacity of the lithium-containing transition metal oxide is 300mAh / g-800mAh / g in a voltage range of 2V-4.3V.

[0043] In this embodiment of the application, at a voltage of 2V-4.3V, a lithium-containing transition metal oxide with a charging capacity of 300mAh / g-800mAh / g is added as a first additive to the positive electrode film layer of the battery cell. The lithium-containing transition metal oxide not only has a high charging capacity, but can also effectively replenish the lithium-ion loss of the battery cell during the cycle, which is beneficial to improving the initial efficiency and energy density of the battery cell.

[0044] In one possible implementation, the specific charging capacity of the lithium-containing transition metal oxide is 600mAh / g-700mAh / g in a voltage range of 2V-4.3V.

[0045] In this embodiment of the application, by using a lithium-containing transition metal oxide with a charging capacity of 600mAh / g-700mAh / g as a first additive added to the positive electrode film layer of the battery cell, the lithium ion loss of the battery cell during the cycle can be further compensated.

[0046] In one possible embodiment, the chain-like carboxylic acid ester solvent includes at least one of methyl formate, methyl acetate, ethyl acetate, ethyl propionate, and their fluorinated organic compounds.

[0047] In this embodiment, by selecting at least one of methyl formate, methyl acetate, ethyl acetate, ethyl propionate, and their fluorinated organic compounds to add to the electrolyte, the fast-charging performance of the battery cell can be satisfied.

[0048] In some possible embodiments, the electrolyte further includes a carbonate solvent, which includes at least one selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; the carbonate solvent content is 12%-33% based on the total mass of the electrolyte.

[0049] In this embodiment, carbonate solvents have good solvation ability, which is beneficial to the dissociation of lithium ions in lithium salts. By adding carbonate solvents to the electrolyte, the degree of lithium ion dissociation can be improved, thereby further improving the performance of the battery cell.

[0050] In some possible implementations, the carbonate solvent includes at least one of ethylene carbonate and propylene carbonate.

[0051] In the embodiments of this application, ethylene carbonate or propylene carbonate is readily available and inexpensive, which is beneficial for its widespread application in production.

[0052] In one possible implementation, the electrolyte further includes an electrolyte salt, which includes at least one of fluorosulfonylimide salt and lithium hexafluorophosphate; the fluorosulfonylimide salt includes one or more of lithium bisfluorosulfonylimide and lithium bistrifluoromethanesulfonate imide.

[0053] In this embodiment of the application, adding at least one of fluorosulfonyl imide salt or lithium hexafluorophosphate as an electrolyte salt can improve the conductivity and degree of ion dissociation of lithium ions. Furthermore, when the electrolyte salt includes at least one of lithium fluorosulfonyl imide or lithium bis(trifluoromethanesulfonate)imide, the conductivity, migration ability and thermal stability of the battery cell can be further improved.

[0054] In some possible embodiments, the electrolyte salt comprises lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate; in the electrolyte, the molar concentration of lithium bis(fluorosulfonyl)imide is 0.2 mol / L-0.5 mol / L and the molar concentration of lithium hexafluorophosphate is 0.5 mol / L-1 mol / L.

[0055] In this embodiment, lithium hexafluorophosphate has advantages such as good solubility, high ion conductivity, high ion dissociation degree, and low cost, while lithium difluorosulfonyl imide has advantages such as good stability, higher ion conductivity, and more lithium ion transference numbers. By combining lithium hexafluorophosphate and lithium difluorosulfonyl imide in an appropriate concentration in the electrolyte, the performance of the battery cell can be further improved and the production cost of the battery cell can be reduced.

[0056] In some possible embodiments, the electrolyte salt comprises lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate; the molar concentration ratio of the lithium bis(fluorosulfonyl)imide to the molar concentration of the lithium hexafluorophosphate is 0.2-0.5.

[0057] In this embodiment of the application, when the electrolyte includes lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate, by making the molar concentration ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate 0.2-0.5, lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate have a more reasonable combination, which helps to improve the performance of the battery cell.

[0058] In one possible implementation, the electrolyte further includes at least one of carbonate additives, sulfur-containing additives, and lithium salt additives.

[0059] In this embodiment, by adding at least one of carbonate additives, sulfur-containing additives, and lithium salt additives to the electrolyte, it is helpful to form a more stable SEI film without increasing the impedance of the battery cells.

[0060] In one possible implementation, the carbonate additive includes at least one of vinylene carbonate and fluoroethylene carbonate.

[0061] In one possible implementation, the sulfur-containing additive includes at least one of vinyl sulfate, vinyl disulfate, butene sulfite, 1,3-propanesulfonate lactone, vinyl sulfite, and methylene disulfonate.

[0062] In one possible implementation, the lithium salt additive includes at least one of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium dioxalate borate.

[0063] In this embodiment of the application, by adding at least one of carbonate additives, sulfur-containing additives, and lithium salt additives to the electrolyte, the performance of the battery cell can be further improved.

[0064] In one possible implementation, the total mass content of the carbonate additive, the sulfur-containing additive, and the lithium salt additive is 1%-10% based on the total mass of the electrolyte.

[0065] In this embodiment of the application, when the total mass content of carbonate additives, sulfur-containing additives and lithium salt additives in the electrolyte is greater than or equal to 1%, the excessive decomposition of the electrolyte in the battery cell under overcharge and over-discharge conditions can be reduced; when the total mass content of carbonate additives, sulfur-containing additives and lithium salt additives is less than or equal to 10%, the impact on the impedance of the battery cell can be reduced and the probability of deterioration of fast charging capability can be reduced.

[0066] In one possible implementation, the electrolyte comprises vinylene carbonate and the fluoroethylene carbonate; based on the total mass of the electrolyte, the mass content of the vinylene carbonate is 0.5%-5%, and the mass content of the fluoroethylene carbonate is 0.1%-3%.

[0067] In this embodiment of the application, when the electrolyte includes vinylene carbonate and fluoroethylene carbonate, the performance of the battery cell can be improved by making the mass contents of vinylene carbonate and fluoroethylene carbonate 0.5%-5% and 0.1%-3%, respectively.

[0068] In one possible implementation, the electrolyte comprises vinylene carbonate and the fluoroethylene carbonate; based on the total mass of the electrolyte, the mass content of the vinylene carbonate is 2.5%-5% and the mass content of the fluoroethylene carbonate is 1%-3%.

[0069] In this embodiment of the application, when the electrolyte includes vinylene carbonate and fluoroethylene carbonate, the performance of the battery cell can be further improved by making the mass contents of vinylene carbonate and fluoroethylene carbonate 2.5%-5% and 1%-3%, respectively.

[0070] In one possible implementation, the electrolyte satisfies at least one of the following conditions: the viscosity of the electrolyte at 20°C-30°C is 2.3 mPa·s-3.5 mPa·s; the conductivity of the electrolyte at 20°C-30°C is 10 mS / cm-18.5 mS / cm.

[0071] In this embodiment of the application, by making the electrolyte meet the above conditions, the battery cell has good conductivity and low internal resistance.

[0072] In one possible implementation, the electrolyte satisfies at least one of the following conditions: the viscosity of the electrolyte at 20°C-30°C is 2.3 mPa·s-3.5 mPa·s; the conductivity of the electrolyte at 20°C-30°C is 14 mS / cm-17.5 mS / cm.

[0073] In this embodiment of the application, by making the electrolyte meet the above conditions, the battery cell has better conductivity and lower internal resistance.

[0074] In one possible implementation, the negative electrode sheet satisfies at least one of the following conditions: the porosity of the negative electrode sheet is 25%-60%; the compaction density of the negative electrode sheet at 0% SOC is 1.65 g / cm³. 3 -1.75g / cm 3 .

[0075] In this embodiment, the negative electrode sheet has a suitable porosity and compaction density, and the battery cell has a suitable energy density and cycle performance.

[0076] In one possible implementation, the negative electrode sheet satisfies at least one of the following conditions: the porosity of the negative electrode sheet is 25%-35%; the compaction density of the negative electrode sheet at 0% SOC is 1.65 g / cm³. 3 -1.75g / cm 3 .

[0077] In this embodiment, the negative electrode sheet has a more suitable porosity and compaction density, and the battery cell has a more suitable energy density and cycle performance.

[0078] In some possible implementations, the volume average particle size of the graphite is Dv50. 1 The size is 7μm-15μm.

[0079] In this embodiment of the application, when the volume average particle size Dv50 of the graphite in the negative electrode sheet is... 1 With a thickness of 7μm-15μm, it can meet the requirements of fast-charging battery systems and improve the performance of individual battery cells.

[0080] In some possible implementations, the volume average particle size of the graphite is Dv50. 1 It is 9μm-12μm.

[0081] In this embodiment of the application, when the volume average particle size Dv50 of the graphite in the negative electrode sheet is... 1 With a thickness of 9μm-12μm, the performance of individual battery cells can be further improved.

[0082] In one possible implementation, the lithium phosphate comprises primary particles and secondary particles formed by the agglomeration of the primary particles, wherein the average longest diameter of the primary particles is 100 nm to 500 nm and the average longest diameter of the secondary particles is 1 μm to 2 μm.

[0083] In the embodiments of this application, when the lithium-containing phosphate meets the above-mentioned limitations, such lithium iron phosphate has a suitable size, which facilitates the intercalation and deintercalation of lithium ions and helps the battery cell to achieve its capacity.

[0084] In one possible implementation, the lithium-containing phosphate comprises the general formula Li x2 D y2 Me a M b P 1-c X c Y z2 The compounds, wherein 0.5≤x²≤1.3, 0≤y²≤1.3, and 0.9≤x²+y²≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z²≤5; D includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of Cl, C, and N; Y includes one or more of O and F.

[0085] In this embodiment of the application, during the charging and discharging process of a single battery cell, the molar content of lithium, oxygen, and other elements in the lithium phosphate varies within a certain range.

[0086] In one possible implementation, the lithium-containing phosphate includes LiFePO4.

[0087] In this embodiment, LiFePO4 is used as the positive electrode active material in the battery cell, which is beneficial to the widespread production of battery cells.

[0088] In one possible implementation, at least a portion of the surface of the lithium phosphate contains carbon.

[0089] In this embodiment, coating the surface of lithium phosphate with carbon elements is beneficial to improving the conductivity of lithium phosphate and maximizing the capacity of the battery cell, thereby giving the battery cell a higher capacity.

[0090] In one possible implementation, the carbon content on the surface of the lithium phosphate is 1%-2% based on the total mass of the lithium phosphate.

[0091] In this embodiment of the application, the surface carbon content of the lithium phosphate is 1%-2%, which can improve the conductivity of the lithium phosphate and thus improve the utilization of the battery cell capacity.

[0092] In one possible implementation, the positive electrode film layer satisfies at least one of the following conditions: the volume average particle size Dv50 of the lithium-containing transition metal oxide is... 2 The particle size is 0.8 μm-5 μm; the volume average particle size Dv50 of the nickel-containing metal oxide is... 3 The particle size is 3μm-30μm; the volume average particle size Dv50 of the lithium phosphate is... 4 The range is 2μm-20μm.

[0093] In this embodiment of the application, by ensuring that the volume average particle size Dv50 of lithium-containing transition metal oxides, nickel-containing metal oxides, and lithium-containing phosphates meets the above requirements, the performance of the battery cell can be improved.

[0094] In one possible implementation, the positive electrode film layer satisfies at least one of the following conditions: the volume average particle size Dv50 of the lithium-containing transition metal oxide is... 2 The particle size is 1μm-3μm; the volume average particle size Dv50 of the nickel-containing metal oxide is... 3 The particle size is 7μm-20μm; the volume average particle size Dv50 of the lithium phosphate is... 4 The size is 5μm-15μm.

[0095] In this embodiment of the application, by ensuring that the volume average particle size Dv50 of lithium-containing transition metal oxides, nickel-containing metal oxides, and lithium-containing phosphates meets the above requirements, the performance of the battery cell can be further improved.

[0096] In a second aspect, a battery device is provided, comprising a battery cell as described in the first aspect and any possible implementation thereof.

[0097] Thirdly, an electrical device is provided, comprising a battery cell as described in the first aspect and any possible embodiment thereof, or a battery device as described in the second aspect, wherein the battery cell or battery device is used to store or provide electrical energy. Attached Figure Description

[0098] 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.

[0099] Figure 1 is a schematic diagram of a vehicle according to an embodiment of this application;

[0100] Figure 2 is a schematic diagram of the structure of a battery device according to an embodiment of this application;

[0101] Figure 3 is a schematic diagram of the structure of a battery cell according to an embodiment of this application;

[0102] Figure 4 is a schematic diagram of the positive electrode sheet according to an embodiment of this application;

[0103] Figure 5 is a schematic diagram of the negative electrode sheet according to an embodiment of this application.

[0104] Reference numerals: 1-Vehicle, 10-Battery unit, 30-Controller, 40-Motor, 11-Box, 111-First box section, 112-Second box section, 3-Battery cell, 31-Shell, 32-End cap assembly, 33-Electrode assembly, 34-Connecting member, 331-Taper, 322-Electrode terminal, 50-Positive electrode sheet, 501-Positive current collector, 502-Positive film, 60-Negative electrode sheet, 601-Negative current collector, 602-Negative film.

[0105] The accompanying drawings are not drawn to scale. Detailed Implementation

[0106] Embodiments of the battery cell, battery device, and electrical appliance of this application have been described in detail with appropriate reference to the accompanying drawings; however, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0107] 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.

[0108] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0109] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0110] 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.

[0111] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0112] Unless otherwise specified, the following terms have the following meanings. Any undefined terms have their technically accepted meanings.

[0113] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits while allowing active ions to pass through.

[0114] In some embodiments, the positive electrode can be a positive electrode sheet, which can include a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes a positive electrode active material, which includes a lithium phosphate.

[0115] In some embodiments, the negative electrode may be a negative electrode sheet, which may include a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0116] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

[0117] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0118] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride, and ceramic.

[0119] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0120] In some embodiments, the battery cell also includes an electrolyte, which 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. The electrolyte can be liquid, gel, or solid.

[0121] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0122] In some embodiments, the battery cell may include a housing. The housing is used to encapsulate components such as electrode assemblies and electrolytes. The housing may be made of steel, aluminum, plastic (such as polypropylene), composite metal (such as copper-aluminum composite), or aluminum-plastic film, etc. The housing includes a shell and end caps.

[0123] The battery mentioned in the embodiments of this application may be a single physical module comprising one or more battery cells to provide higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, parallel, or mixed via a busbar.

[0124] In some embodiments, the battery device may be a battery pack, which includes a housing and individual battery cells, with the individual battery cells or battery modules housed within the housing.

[0125] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0126] In some embodiments, the battery device may be located within an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0127] The embodiments of this application will be described next.

[0128] Battery systems are a crucial component of modern electric vehicle technology, playing a key role in improving the performance and efficiency of electric vehicles. With the rapid development of the electric vehicle market, consumers' demands for vehicle charging and extended driving range are increasing, driving advancements in fast-charging battery system technology.

[0129] During continuous battery cycling, some lithium ions become completely embedded in the material and cannot be extracted, causing more and more active lithium to become dead lithium, resulting in a decreasing active lithium content in the battery. To replenish the active lithium, lithium-containing transition metal oxides are used as lithium replenishers in the positive electrode. However, during the extraction of active lithium ions, lithium transition metal oxide lithium replenishers generate oxygen free radicals (active oxygen). These oxygen free radicals react with the electrolyte to produce organic fragments RH+. RH+ diffuses to the negative electrode and is reduced to produce hydrogen gas. Furthermore, to reduce battery internal resistance and increase charging speed, fast-charging battery systems generally use highly conductive electrolytes. However, highly conductive electrolytes generally have poor stability and are easily oxidized by oxygen free radicals, generating gas. This further increases the risk of excessive gas production inside the battery, potentially severely affecting the battery's cycle performance.

[0130] In summary, while lithium-containing transition metal oxides can replenish active lithium ions as lithium supplements, they also generate a significant amount of gas, and highly conductive electrolytes may exacerbate this gas production. Therefore, how to reduce battery gas production while improving fast-charging performance to enhance cycle performance is a pressing technical challenge.

[0131] In view of this, this application provides a battery cell, comprising a positive electrode sheet including a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer including lithium phosphate, a first additive and a second additive, the first additive including a lithium transition metal oxide and the second additive including a nickel metal oxide; a negative electrode sheet including a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, the negative electrode film layer including graphite; and an electrolyte including a chain-like carboxylic acid ester solvent, the chain-like carboxylic acid ester solvent having a mass content of 32%-60% based on the total mass of the electrolyte. The first additive can release lithium ions to compensate for the loss of active lithium in the battery cell during cycling; the chain-like carboxylic acid ester solvent helps to improve the conductivity of the electrolyte to meet the fast-charging performance of the battery cell; and the second additive can promote the rapid conversion of oxygen free radicals generated by the delithiation of the first additive into oxygen, reducing the amount of gas generated by the side reaction of RH+ generated by oxygen free radicals at the negative electrode and reducing the impact on cycle performance. That is, by using chain-like carboxylic acid ester solvents, the first additive, and the second additive, it is possible to improve the fast charging performance of battery cells while reducing the gas production of battery cells and improving the cycle performance of battery cells.

[0132] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use battery devices.

[0133] Electrical equipment can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-mentioned electrical equipment.

[0134] For ease of explanation, the following embodiments use a vehicle as an example of electrical equipment.

[0135] For example, as shown in Figure 1, which is a structural schematic diagram of a vehicle 1 according to an embodiment of this application, vehicle 1 can be a gasoline vehicle, a natural gas vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A motor 40, a controller 30, and a battery device 10 can be installed inside vehicle 1. The controller 30 is used to control the battery device 10 to supply power to the motor 40. For example, the battery device 10 can be installed at the bottom, front, or rear of vehicle 1. The battery device 10 can be used to power vehicle 1. For example, the battery device 10 can serve as the operating power source for vehicle 1, for example, for the electrical system of vehicle 1, such as for the power requirements of vehicle 1's starting, navigation, and operation. In another embodiment of this application, the battery device 10 can not only serve as the operating power source for vehicle 1, but also as the driving power source for vehicle 1, replacing or partially replacing gasoline or natural gas to provide driving power for vehicle 1.

[0136] Figure 2 shows a partial structural schematic diagram of the battery device 10 according to an embodiment of this application. For example, as shown in Figure 2, the battery device 10 according to this application embodiment may include multiple battery cells 3 to meet different power usage requirements. The shape of the battery cell 3 according to this application embodiment can be set according to actual application. For example, the battery cell 3 can be cylindrical, or it can be cuboid or other shapes, and this application embodiment is not limited to this.

[0137] It should be understood that, as shown in FIG. 2, the battery device 10 of this embodiment may further include a housing 11, which can be used to accommodate multiple battery cells 3. The housing 11 of this embodiment has a hollow internal structure, and the multiple battery cells 3 are accommodated within the housing 11. The housing 11 may include two parts, referred to herein as a first housing portion 111 and a second housing portion 112, which are fastened together. The shapes of the first housing portion 111 and the second housing portion 112 can be determined according to the shape of the components accommodated internally, for example, according to the shape of the combination of the multiple battery cells 3 accommodated internally. At least one of the first housing portion 111 and the second housing portion 112 has an opening. For example, as shown in Figure 2, the first housing portion 111 and the second housing portion 112 can both be hollow cuboids with one open face. The openings of the first housing portion 111 and the second housing portion 112 are opposite to each other, and the first housing portion 111 and the second housing portion 112 are interlocked to form a housing 11 with a closed cavity, which can be used to accommodate multiple battery cells 3. The multiple battery cells 3 are connected in parallel, series, or mixed and placed inside the housing 11 formed by the interlocking of the first housing portion 111 and the second housing portion 112.

[0138] For example, unlike what is shown in Figure 2, only one of the first housing portion 111 and the second housing portion 112 may be a hollow cuboid with an opening, while the other is plate-shaped to cover the opening. Taking the second housing portion 112 as a hollow cuboid with one opening, and the first housing portion 111 as a plate-shaped example, then the first housing portion 111 covers the opening of the second housing portion 112 to form a housing 11 with a closed chamber, which can be used to accommodate multiple battery cells 3.

[0139] In this embodiment of the application, the battery cell 3 can be a secondary battery, which refers to the battery cell 3 that can be used again after being discharged by recharging to activate the active materials.

[0140] The battery cell 3 can be a lithium-ion battery or a lithium metal battery.

[0141] During the charging process of battery cell 3, lithium ions are extracted from the positive electrode active material, move and embed into the negative electrode; while during the discharging process, lithium ions are extracted from the negative electrode, move and embed into the positive electrode active material.

[0142] It should be understood that the “intercalation” process described in this application refers to the process by which lithium ions are intercalated in the positive electrode active material or the negative electrode due to an electrochemical reaction, and the “extraction” process described in this application refers to the process by which lithium ions are extracted from the positive electrode active material or the negative electrode due to an electrochemical reaction.

[0143] Typically, a battery cell 3 includes a positive electrode, a negative electrode, an electrolyte, and a separator. The battery cell and its components provided in this application will be described below.

[0144] [Battery cell]

[0145] Figure 3 is a schematic diagram of the structure of a battery cell according to an embodiment of this application. In one embodiment of this application, for example, referring to Figure 3, the battery cell 3 includes a housing 31, an end cap assembly 32, and an electrode assembly 33. The housing 31 has an opening for accommodating the electrode assembly 33, and the end cap assembly 32 is used to close the opening. The electrode assembly 33 may include a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode.

[0146] Figure 4 is a schematic diagram of a positive electrode sheet in one embodiment of this application. For example, as shown in Figure 4, the positive electrode sheet 50 includes a positive current collector 501 and a positive electrode film layer 502 disposed on at least one side of the positive current collector 501.

[0147] The positive electrode current collector 501 has two side surfaces along its own thickness direction (e.g., the z-direction in Figure 4). The positive electrode film layer 502 can be disposed on one side surface of the positive electrode current collector 501 or on both side surfaces of the positive electrode current collector 501. As an example, as shown in Figure 4, the positive electrode film layer 502 is disposed on both side surfaces of the positive electrode current collector 501.

[0148] The positive electrode film 502 includes lithium phosphate, a first additive, and a second additive. The first additive includes a lithium transition metal oxide, and the second additive includes a nickel metal oxide.

[0149] Lithium-containing phosphates can refer to lithium-containing transition metal phosphates with an olivine structure, such as lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and their modified forms.

[0150] Lithium-containing transition metal oxides include lithium, transition elements, and oxygen; transition metals include iron, among others. Within a certain voltage range, lithium-containing transition metal oxides can decompose to produce lithium ions, and simultaneously generate oxygen free radicals (also known as reactive oxygen species).

[0151] Lithium-containing transition metal oxides are used as the first additive, that is, lithium-containing transition metal oxides can generate active lithium ions to replenish the lithium ions consumed in the process of forming the solid electrolyte interface membrane (SEI).

[0152] Nickel-containing metal oxides include nickel and oxygen. In some embodiments, nickel-containing metal oxides may also include lithium.

[0153] The electrolyte, including chain carboxylic acid ester solvents, has a mass content of 32%-60% based on the total mass of the electrolyte.

[0154] Based on the total mass of the electrolyte, when the mass content of the chain carboxylic acid ester solvent is greater than or equal to 32%, it helps to reduce the overall viscosity of the electrolyte to improve ionic conductivity and reduce the internal resistance of the battery cell 3. When the mass content of the chain carboxylic acid ester solvent is less than or equal to 60%, it can reduce the risk of the electrolyte viscosity being too low due to the addition of too much chain carboxylic acid ester solvent, which would affect the lithium ion transport efficiency between the electrodes, so as to ensure the energy density of the battery cell 3.

[0155] Therefore, fast-charging battery systems require higher electrolyte conductivity. Adding a low-molecular-weight, low-viscosity solvent to the electrolyte and adjusting its concentration to 32% to 60% can improve the electrolyte's charge transfer capacity and reduce the internal resistance of the battery cell 3. However, chain-like carboxylic acid ester solvents are prone to side reactions, especially at high temperatures, which can easily lead to undesirable side reactions such as gas generation, thus reducing the battery's long-term cycle performance. This application improves the long-term cycle performance of fast-charging battery cells by adding lithium-containing transition metal oxides that can release more active lithium ions to the positive electrode. However, while releasing active lithium ions, these lithium-containing transition metal oxides also generate oxygen free radicals. These oxygen free radicals easily react with the electrolyte to produce organic fragments RH+. These RH+ ions diffuse to the negative electrode and are reduced, further generating gas. Furthermore, due to the poor stability of chain-like carboxylic acid esters, they are easily oxidized by RH+, further increasing the risk of high gas generation within the battery cell 3. In other words, although lithium-containing transition metal oxides can replenish active lithium ions as the first additive, they will generate more gas during long-term battery cycling, which is not conducive to improving battery cycle performance.

[0156] Although the mechanism is not yet clear, this application further adds nickel-containing metal oxides to the positive electrode. During the formation of the battery cell, the nickel-containing metal oxides can catalyze the oxygen free radicals generated by lithium-containing transition metal oxides, thereby reducing the content of oxygen free radicals in the battery cell. This further reduces the content of organic fragments RH+ generated by the side reaction of oxygen free radicals with the electrolyte, and reduces the amount of hydrogen gas generated by the subsequent side reaction of RH+ at the negative electrode and reduces the risk of oxygen free radicals oxidizing chain carboxylic acid ester solvents and generating gas. As a result, the amount of gas generated by the battery during long-term cycling can be reduced, and the cycle performance of the battery can be improved.

[0157] Figure 5 is a schematic diagram of a negative electrode sheet in one embodiment of this application. For example, as shown in Figure 5, the negative electrode sheet 60 includes a negative current collector 601 and a negative electrode film layer 602 disposed on at least one side of the negative current collector 601.

[0158] The negative electrode current collector 601 has two side surfaces along its own thickness direction (e.g., the z-direction in FIG. 5). The negative electrode film layer 602 can be disposed on one side surface of the negative electrode current collector 601 or on both side surfaces of the negative electrode current collector 601. As an example, as shown in FIG. 5, the negative electrode film layer 602 is disposed on both side surfaces of the negative electrode current collector 601.

[0159] The negative electrode film 602 includes a negative electrode active material, which includes graphite; the negative electrode film 602 includes graphite.

[0160] Graphite, as the negative electrode active material of battery cell 3, has a high theoretical capacity, a low operating voltage platform, and good cycle performance.

[0161] By using chain-like carboxylic acid ester solvents in the electrolyte, the conductivity of the electrolyte can be improved, enabling the battery cell 3 to meet the requirements of fast charging.

[0162] By using lithium-containing transition metal oxides as the first additive in battery cell 3, the loss of active lithium in battery cell 3 during cycling can be compensated, which is beneficial to improving the first coulombic efficiency and cycle performance of battery cell 3.

[0163] This application further adds nickel-containing metal oxides to the positive electrode. During the formation of the battery cell, the nickel-containing metal oxides can catalyze the oxygen free radicals generated by lithium-containing transition metal oxides, thereby reducing the content of oxygen free radicals in the battery cell. This further reduces the content of RH+ generated by the side reaction of oxygen free radicals with the electrolyte, and reduces the amount of hydrogen gas generated by the subsequent side reaction of RH+ at the negative electrode and reduces the risk of oxygen free radicals oxidizing chain carboxylic acid ester solvents and generating gas. As a result, the amount of gas generated by the battery during long-term cycling can be reduced, and the cycle performance of the battery can be improved.

[0164] Specifically, based on the total mass of the electrolyte, the mass content of the chain carboxylic acid ester solvent can be 32%, 40%, 45%, 50%, 55%, 60%, or any value within the above range.

[0165] Specifically, the specific components in the electrolyte can be tested using the following methods: the types and contents of organic components in the electrolyte can be detected using equipment and methods known in the art. For example, the organic components in the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography using GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, or a fully discharged battery (discharged to the lower limit cutoff voltage so that the battery's state of charge is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample for detection using ion chromatography.

[0166] In some embodiments, the average length of the longest diameter of the lithium-containing transition metal oxide is 8 μm-30 μm on a longitudinal section along the thickness direction of the positive electrode 50.

[0167] The longest diameter of a particle can be defined as the longest straight line that passes through the center point of the particle and extends to the outer periphery of the particle. The average value of the longest diameter of lithium transition metal oxides can be obtained by taking 30 lithium transition metal oxide particles in a longitudinal section of the positive electrode film layer 502, measuring the longest diameter of each of the 30 particles, and then taking the average value.

[0168] In the above scheme, by making the average length of the lithium-containing transition metal oxide greater than or equal to 8 μm, the degree of side reaction of the lithium-containing transition metal oxide in the battery cell 3 can be reduced, thereby improving the cycle performance of the battery cell 3; by making the average length of the lithium-containing transition metal oxide less than or equal to 30 μm, it is conducive to the deintercalation and deintercalation of lithium ions, which helps to balance the capacity and cycle performance of the battery cell 3.

[0169] Specifically, on the longitudinal section along the thickness direction of the positive electrode 50, the average value of the longest diameter of the lithium-containing transition metal oxide can be 8μm, 10μm, 16μm, 20μm, 25μm, 30μm or any value within the above range.

[0170] Specifically, the longest diameter of the materials can be tested using the following method: After disassembling the battery cell 3, the positive electrode sheet is removed and cut along the thickness direction to expose the longitudinal section of the positive electrode film. The longest diameter of the first additive, the second additive, and the lithium iron phosphate material is determined by scanning electron microscopy (SEM) testing of the longitudinal section of the positive electrode film. Specifically, the longest diameter of the first additive refers to the longest straight line passing through the center point of the first additive and extending to the outer periphery of the particle; the longest diameter of the lithium iron phosphate material refers to the longest straight line passing through the center point of the lithium iron phosphate material and extending to the outer periphery of the particle; and the longest diameter of the second additive refers to the longest straight line passing through the center point of the second additive and extending to the outer periphery of the particle. As an example, arbitrarily select 30 first additive particles in the longitudinal section of the positive electrode film, measure the longest diameter of each of the 30 first additive particles, and take their average value; arbitrarily select 30 lithium iron phosphate material particles in the longitudinal section of the positive electrode film, measure the longest diameter of each of the 30 lithium iron phosphate material particles, and take their average value; arbitrarily select 30 second additive particles in the longitudinal section of the positive electrode film, measure the longest diameter of each of the 30 second additive particles, and take their average value.

[0171] In some embodiments, the average length of the longest diameter of the nickel-containing metal oxide is 7 μm to 20 μm on a longitudinal section along the thickness direction of the positive electrode 50.

[0172] The average value of the longest diameter of nickel-containing metal oxide can be obtained by taking 30 nickel-containing metal oxide particles in the longitudinal section of the positive electrode film 502, measuring the longest diameter of each of the 30 particles, and then taking the average value to obtain the average value of the longest diameter of the nickel-containing metal oxide.

[0173] In the above scheme, by making the average length of the nickel-containing metal oxide greater than or equal to 7 μm, the degree of side reaction of the nickel-containing metal oxide in the battery cell 3 can be reduced, thereby improving the film quality of the SEI film; by making the average length of the nickel-containing metal oxide less than or equal to 20 μm, the contact area between the nickel-containing metal oxide and other substances can be increased, promoting the conversion of oxygen free radicals, thereby reducing the gas production of the battery cell 3.

[0174] Specifically, on the longitudinal section along the thickness direction of the positive electrode 50, the average value of the longest diameter of the nickel-containing metal oxide can be 7μm, 10μm, 12μm, 14μm, 16μm, 20μm or any value within the above range.

[0175] In some embodiments, the lithium-containing transition metal oxide includes a substrate and a coating layer located on at least a portion of the surface of the substrate, the substrate comprising Li x1 N y1 O z1 Where 1≤x1≤6, 1≤y1≤3, 1≤z1≤6, and N includes at least one of Ni, Fe, Cu, Co, Mn, Al, and Na.

[0176] When the molar content of lithium in the matrix is ​​greater than or equal to 1, it is beneficial to release more lithium ions to replenish the active lithium consumed in the battery cell 3.

[0177] In the above scheme, the lithium-containing transition metal oxide includes a substrate and a coating layer, wherein the substrate has the general formula Li. x1 N y1 O z1 1≤x1≤6, 1≤y1≤3, 1≤z1≤6, N includes at least one of Ni, Fe, Cu, Co, Mn, Al, and Na. Such lithium-containing transition metal oxides can provide active lithium to compensate for lithium loss in battery cell 3 during cycling.

[0178] Specifically, in the general formula Li x1 N y1 O z1 In the compound, x1 can be 1, 1.5, 2, 2.5, 3, 4.5, 5 or any value within the above range; y1 can be 1, 1.5, 2.3, 3, 4, 4.8, 5 or any value within the above range; z1 can be 1, 1.8, 2.6, 3.9, 4.2, 5, 6 or any value within the above range.

[0179] In some embodiments, the matrix comprises Li5FeO4.

[0180] In the above scheme, Li5FeO4 is added as the first additive to the positive electrode film layer 502 of the battery cell 3. The lithium ions released from it can compensate for the lithium loss of the battery cell 3, so as to improve the initial efficiency and energy density of the battery cell 3.

[0181] It should be noted here that Li5FeO4 is the chemical formula of the matrix before delithiation. During the formation of battery cell 3, Li5FeO4 decomposes to produce lithium ions and oxygen free radicals. The molar content of lithium and oxygen in the matrix will change depending on the degree of decomposition.

[0182] In some embodiments, the matrix includes Li e FeO f ,0≤e≤5,0 <f≤4。

[0183] In the above scheme, during the formation stage of battery cell 3, the matrix of the first additive decomposes, generating oxygen free radicals while producing lithium ions, and the molar content of Li and O elements changes. For example, after decomposition, it can be an iron oxide that does not contain lithium. In the formed battery cell 3, the molar content of each element in the chemical formula of the matrix of the first additive in the positive electrode film layer 502 is within the above-mentioned range.

[0184] Specifically, in the general formula Li e FeO f In the compound, e can be 1, 1.5, 1.8, 2, 2.5, 3, 4.5, 5 or any value within the above range; f can be 1, 1.5, 2, 2.3, 2.8, 3, 4 or any value within the above range.

[0185] In some embodiments, the matrix includes Li h FeO n ,0≤h≤1,0 <n≤2。

[0186] In the above scheme, during the formation process of battery cell 3, the matrix decomposes, generating oxygen free radicals along with lithium ions, and the molar contents of Li and O elements change. In the formed battery cell 3, the molar contents of each element in the chemical formula of the matrix of the first additive in the positive electrode film layer 502 are within the above-mentioned range.

[0187] Specifically, in the general formula Li h FeO n In the compound, h can be 0, 0.2, 0.45, 0.5, 0.63, 0.88, 1 or any value within the above range; n can be 0.1, 0.5, 0.8, 1, 1.2, 1.5, 2 or any value within the above range.

[0188] In some embodiments, the coating layer includes at least one of C, Al, Zr, Si, B, S, and P.

[0189] In the above scheme, the first additive includes a matrix and a coating layer. The coating layer includes at least one of C, Al, Zr, Si, B, S, and P. The coating layer can reduce the probability of the matrix being in direct contact with air, reduce the probability of the matrix reacting with water and carbon dioxide in the air, improve the air stability of the matrix, reduce the formation of impurity lithium on the matrix surface, and at the same time improve the conductivity of the matrix and improve the utilization rate of active lithium ions.

[0190] In some implementations, the thickness of the coating layer is 10nm-100nm.

[0191] In the above scheme, by making the thickness of the coating layer 10nm-100nm, the coating layer has a reasonable thickness, which helps the extraction and insertion of lithium ions, thereby improving the ionic conductivity of the first additive and the kinetic performance of the battery cell 3.

[0192] Specifically, the thickness of the coating layer can be 10nm, 25nm, 40nm, 60nm, 80nm, 100nm or any value within the above range.

[0193] Specifically, the thickness of the coating layer can be detected by the following method: After disassembling the battery cell, remove the positive electrode sheet. Cut the positive electrode sheet along its thickness direction to expose the longitudinal section of the positive electrode film. By performing SEM testing on the longitudinal section of the positive electrode film, and selecting the first additive particle, it can be observed that the first additive particle has a core-shell structure. The thickness of the shell layer is then measured as the thickness of the coating layer.

[0194] In some embodiments, the nickel-containing metal oxide includes M m NiO d M includes at least one of Li, Na, and K, 0≤m≤2, 1≤d≤2.

[0195] When battery cell 3 is a lithium battery cell, M can be lithium; when battery cell 3 is a sodium battery cell, M can be sodium, and so on.

[0196] When m is 0, the nickel-containing metal oxide can be nickel oxide; when M is lithium and m is greater than 0, the nickel-containing metal oxide can be a lithium-containing nickel metal oxide; when M is lithium and m is greater than 1, the nickel-containing metal oxide has a higher molar content of lithium, and can also provide active lithium ions to battery cell 3 to replenish the consumed active lithium ions.

[0197] In the above scheme, the first additive generates oxygen free radicals while replenishing active lithium. This is addressed by adding a second additive, including a nickel-containing metal oxide, to the positive electrode film layer 502, where the general formula of the nickel-containing metal oxide is M. m NiO d M includes at least one of Li, Na, and K, 0≤m≤2, 1≤d≤2. Such nickel-containing metal oxides can rapidly convert the oxygen free radical intermediates generated by the first additive into oxygen, reduce the residence time of oxygen free radicals, and thus reduce the damage to the electrolyte and SEI film components, which helps to improve the stability of the negative electrode film formation and improve the cycle performance of the battery cell 3.

[0198] Specifically, in the general formula M m NiO d In the compound, m can be 0, 0.2, 0.5, 0.9, 1.4, 1.6, 2 or any value within the above range; d can be 1, 1.1, 1.29, 1.4, 1.6, 1.88, 2 or any value within the above range.

[0199] In some embodiments, the nickel-containing metal oxide includes Li2NiO2.

[0200] In the above scheme, Li2NiO2 is added as a second additive to the positive electrode film layer 502 of the battery cell 3, which can effectively convert oxygen free radicals and reduce the impact of oxygen free radicals on the electrolyte and SEI film.

[0201] It should be noted that before the formation of battery cell 3, the nickel-containing metal oxide of the positive electrode film 502 in battery cell 3 can be Li2NiO2. During the formation process, Li2NiO2 decomposes, lithium ions are released, and the oxygen content may also change accordingly.

[0202] In some embodiments, the nickel-containing metal oxide includes Li g NiO i ,0≤g≤2,0 <i≤2。

[0203] In the above scheme, during the formation process of battery cell 3, the nickel-containing metal oxide decomposes, and the molar content of lithium and oxygen will change to a certain extent.

[0204] Specifically, in the general formula Li g NiO i In the compound, g can be 0, 0.4, 0.68, 1, 1.4, 1.6, 2 or any value within the above range; i can be 0.2, 0.5, 0.9, 1.3, 1.5, 1.9, 2 or any value within the above range.

[0205] In some embodiments, the nickel-containing metal oxide includes NiO. q 0 <q≤2。

[0206] In the above scheme, during the formation process of battery cell 3, the nickel-containing metal oxide decomposes, and the molar content of oxygen will change to a certain extent. For example, lithium in the nickel-containing metal oxide is completely released and decomposes into nickel oxide.

[0207] In some embodiments, the ratio of the mass content of nickel-containing metal oxide to the mass content of lithium-containing transition metal oxide is 0.1-0.4.

[0208] In the above scheme, by making the mass ratio of nickel-containing metal oxide to lithium-containing transition metal oxide 0.1-0.4, the nickel-containing metal oxide can more thoroughly convert the oxygen free radicals generated by the lithium-containing transition metal oxide, thereby reducing the gas production of battery cell 3 and improving the cycle performance of battery cell 3.

[0209] Specifically, the ratio of the mass content of nickel-containing metal oxide to the mass content of lithium-containing transition metal oxide can be 0.1, 0.15, 0.2, 0.27, 0.32, 0.4 or any value within the above range.

[0210] In some embodiments, the mass ratio of nickel-containing metal oxide to lithium-containing transition metal oxide is 0.15-0.25.

[0211] In the above scheme, by making the mass ratio of nickel-containing metal oxide to lithium-containing transition metal oxide 0.15-0.25, the nickel-containing metal oxide can more thoroughly convert the oxygen free radicals generated by the lithium-containing transition metal oxide, which helps to further reduce the gas production of battery cell 3 and improve the cycle performance of battery cell 3.

[0212] In some implementations, the mass content of lithium phosphate is 80%-97% based on the total mass of the positive electrode film 502.

[0213] In the above scheme, the mass content of lithium phosphate in the positive electrode film layer 502 is 80%-97%, which can ensure that the battery cell 3 has a high energy density and capacity.

[0214] Specifically, based on the total mass of the positive electrode film layer 502, the mass content of lithium phosphate can be 80%, 83%, 85%, 89%, 90%, 95%, 97%, or any value within the above range.

[0215] In some embodiments, the mass content of lithium transition metal oxide is 0.1%-5% based on the total mass of the positive electrode film 502.

[0216] In the above scheme, the mass content of lithium transition metal oxide in the positive electrode film layer 502 is 0.1%-5%. This mass content of the first additive can compensate for more lithium ions without generating more oxygen free radicals, which helps to improve the overall performance of the battery cell 3.

[0217] Specifically, based on the total mass of the positive electrode film layer 502, the mass content of lithium transition metal oxide can be 0.1%, 0.8%, 1.5%, 2.8%, 3.7%, 4%, 5%, or any value within the above range.

[0218] Specifically, the specific components in the positive electrode film can be tested using the following method: After disassembling the battery cell 3, scrape off the positive electrode film of the positive electrode sheet. Add the scraped material to aqua regia and digest it under mechanical stirring for 30 minutes. Add the digested solution to an ICAP7400 spectrometer to analyze the elemental composition. For example, for the positive electrode sheet, the contents of Ni, Fe, and P elements can be measured. Specifically, the mass content of the second additive (e.g., Li2NiO2) can be determined by detecting the Ni element, and the mass content of the first additive (e.g., Li5FeO4) in the positive electrode film can be determined by detecting the ratio of P to Fe elements.

[0219] In some embodiments, the mass content of nickel metal oxide is 0.03%-2% based on the total mass of the positive electrode film 502.

[0220] In the above scheme, the mass content of nickel metal oxide in the positive electrode film layer 502 is 0.03%-2%, and the second additive with this mass content can more thoroughly convert the oxygen free radicals generated by the first additive.

[0221] Specifically, based on the total mass of the positive electrode film 502, the mass content of nickel metal oxide can be 0.03%, 0.1%, 0.5%, 0.8%, 1.2%, 1.5%, 2%, or any value within the above range.

[0222] In some implementations, the specific charging capacity of the lithium transition metal oxide is 300 mAh / g to 800 mAh / g in a voltage range of 2V to 4.3V.

[0223] In the above scheme, at a voltage of 2V-4.3V, a lithium-containing transition metal oxide with a charging capacity of 300mAh / g-800mAh / g is added as the first additive to the positive electrode film layer 502 of the battery cell 3. The lithium-containing transition metal oxide not only has a high charging capacity, but can also effectively replenish the lithium ion loss of the battery cell 3 during the cycle, which is beneficial to improving the first efficiency and energy density of the battery cell 3.

[0224] Specifically, within a voltage range of 2V-4.3V, the charge capacity of lithium transition metal oxides can be 300mAh / g, 380mAh / g, 420mAh / g, 500mAh / g, 600mAh / g, 750mAh / g, 800mAh / g, or any value within the above range.

[0225] Specifically, the specific capacity of the material can be tested using the following method: A positive electrode slurry is prepared by mixing lithium-containing transition metal oxide, conductive carbon Super P, and binder polyvinylidene fluoride (PVDF) in a mass ratio of 7:2:1 and adding it to N-methylpyrrolidone (NMP). The positive electrode slurry is then coated onto aluminum foil and dried to obtain the positive electrode sheet. Using a conventional electrolyte from a lithium iron phosphate battery system, the positive electrode sheet is assembled with a copper sheet to form a coin cell (CR2025). The coin cell capacity is measured by constant current charging to 4.3V at a rate of 0.05C. Specific capacity = coin cell capacity / mass of the first additive.

[0226] In some implementations, the specific charging capacity of the lithium transition metal oxide is 600mAh / g-700mAh / g in a voltage range of 2V-4.3V.

[0227] In the above scheme, by using a lithium-containing transition metal oxide with a charging capacity of 600mAh / g-700mAh / g as the first additive added to the positive electrode film layer 502 of the battery cell 3, it is beneficial to further improve the initial efficiency and energy density of the battery cell 3.

[0228] In some embodiments, the chain carboxylic acid ester solvent includes at least one of methyl formate, methyl acetate, ethyl acetate, ethyl propionate, and their fluorinated organic compounds.

[0229] In the above scheme, by selecting at least one of methyl formate, methyl acetate, ethyl acetate, ethyl propionate and their fluorinated organic compounds to add to the electrolyte, the fast charging performance of battery cell 3 can be satisfied.

[0230] In some embodiments, the electrolyte further includes a carbonate solvent, which includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; the carbonate solvent content is 12%-33% based on the total mass of the electrolyte.

[0231] Chain-like carboxylic acid ester solvents have lower melting points and viscosity, which can reduce interfacial tension and exhibit better fluidity at low temperatures, thus improving the battery's charging capability at low temperatures. However, due to their low dielectric constant and poor chemical stability, exceeding a certain limit can lead to poor lithium salt dissociation and severe side reactions, adversely affecting the fast-charging and cycle performance of battery cell 3. Carbonate solvents have good solvation capabilities, which is beneficial for dissociating lithium ions from lithium salts; however, their high viscosity, poor fluidity, and poor wettability result in a lack of ability to bring lithium ions to the correct potential. Therefore, adding both chain-like carboxylic acid ester solvents and carbonate solvents to the electrolyte is beneficial for improving battery performance.

[0232] In the above scheme, carbonate solvents have better solubilization ability, which is beneficial to the dissociation of lithium ions in lithium salt. By adding carbonate solvents to the electrolyte, the degree of lithium ion dissociation can be improved, thereby further improving the performance of battery cell 3.

[0233] Specifically, based on the total mass of the electrolyte, the mass content of carbonate solvents can be 12%, 20%, 24%, 28%, 30%, 33%, or any value within the above range.

[0234] In some embodiments, the carbonate solvent includes at least one of ethylene carbonate and propylene carbonate.

[0235] In the above schemes, ethylene carbonate or propylene carbonate are readily available and have low cost, which is conducive to their widespread application in production.

[0236] In some embodiments, the electrolyte further includes an electrolyte salt, which includes at least one of fluorosulfonylimide salt and lithium hexafluorophosphate; the fluorosulfonylimide salt includes one or more of lithium bisfluorosulfonylimide and lithium bistrifluoromethanesulfonate imide.

[0237] The electrolyte salt may consist only of fluorosulfonyl imide salt, or only of lithium hexafluorophosphate, or may include both fluorosulfonyl imide salt and lithium hexafluorophosphate.

[0238] Lithium hexafluorophosphate (LiPF6) has advantages such as good solubility, high ion conductivity, and high ion dissociation, but its poor thermal stability and tendency to hydrolyze into hydrogen fluoride lead to rapid capacity decay in batteries. Fluorosulfonyl imide salts offer higher thermal stability, ion conductivity, lithium-ion transference number, and superior low-temperature performance, but they are more expensive. Therefore, adding both as electrolyte salts to the electrolyte can improve the performance of individual battery cells while reducing production costs.

[0239] In the above scheme, adding at least one of fluorosulfonyl imide salt or lithium hexafluorophosphate as electrolyte salt can improve the lithium ion conductivity and ion dissociation degree; furthermore, when the electrolyte salt includes at least one of lithium fluorosulfonyl imide or lithium bistrifluoromethanesulfonate imide, the ion conductivity, ion migration ability and thermal stability of battery cell 3 can be further improved.

[0240] In some embodiments, the electrolyte salt includes lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate; in the electrolyte, the molar concentration of lithium bis(fluorosulfonyl)imide is 0.2 mol / L-0.5 mol / L and the molar concentration of lithium hexafluorophosphate is 0.5 mol / L-1 mol / L.

[0241] In the above scheme, lithium hexafluorophosphate has advantages such as good solubility, high ion conductivity, high ion dissociation degree and low cost, while lithium difluorosulfonylimide has advantages such as good stability, higher ion conductivity and lithium ion transference number. By using lithium hexafluorophosphate and lithium difluorosulfonylimide in the electrolyte at a reasonable concentration, the performance of battery cell 3 can be further improved and the production cost of battery cell 3 can be reduced.

[0242] Specifically, in the electrolyte, the molar concentration of lithium bis(fluorosulfonyl)imide can be 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L or any value within the above range, and the molar concentration of lithium hexafluorophosphate can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L or any value within the above range.

[0243] Specifically, the mass content of electrolyte salts can be detected by the following methods: The concentration of inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed using ion chromatography, referring to standard JY / T020-1996 "General Rules for Ion Chromatography Analysis". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, the free electrolyte from a fresh battery can be used as a sample, or a fully discharged battery (discharged to the lower cutoff voltage so that the battery's state of charge is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample for detection using ion chromatography.

[0244] In some embodiments, the electrolyte salt comprises lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate; the molar concentration ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate is 0.2-0.5.

[0245] In the above scheme, when the electrolyte includes lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate, by making the molar concentration ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate 0.2-0.5, lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate have a relatively reasonable combination, which helps to improve the performance of battery cell 3.

[0246] Specifically, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate can be 0.2, 0.3, 0.4, 0.48, 0.5 or any value within the above range.

[0247] In some embodiments, the electrolyte further includes at least one of carbonate additives, sulfur-containing additives, and lithium salt additives.

[0248] In the above scheme, by adding at least one of carbonate additives, sulfur-containing additives, and lithium salt additives to the electrolyte, it helps to form a more stable SEI film without increasing the impedance of the battery cell 3.

[0249] In some embodiments, the carbonate additives include at least one of vinylene carbonate and fluoroethylene carbonate.

[0250] In some embodiments, the sulfur-containing additives include at least one of vinyl sulfate, vinyl disulfate, butene sulfite, 1,3-propanesulfonate lactone, vinyl sulfite, and methylene disulfonate.

[0251] In some embodiments, the lithium salt additive includes at least one of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium dioxalate borate.

[0252] In the above scheme, by adding at least one of the following substances to the electrolyte: carbonate additives, sulfur-containing additives, and lithium salt additives, the performance of the battery cell 3 can be further improved.

[0253] In some embodiments, the total mass content of carbonate additives, sulfur-containing additives, and lithium salt additives is 1%-10% based on the total mass of the electrolyte.

[0254] In the above scheme, when the total mass content of carbonate additives, sulfur-containing additives and lithium salt additives in the electrolyte is greater than or equal to 1%, the excessive decomposition of the electrolyte in the battery cell 3 under overcharge and over-discharge conditions can be reduced; when the total mass content of carbonate additives, sulfur-containing additives and lithium salt additives is less than or equal to 10%, the impact on the impedance of the battery cell 3 can be reduced and the probability of deterioration of fast charging capability can be reduced.

[0255] Specifically, based on the total mass of the electrolyte, the total mass content of carbonate additives, sulfur-containing additives, and lithium salt additives can be 1%, 2%, 5%, 6.8%, 8%, 10%, or any value within the above range.

[0256] In some embodiments, the electrolyte comprises vinylene carbonate and the fluoroethylene carbonate; based on the total mass of the electrolyte, the mass content of vinylene carbonate is 0.5%-5% and the mass content of fluoroethylene carbonate is 0.1%-3%.

[0257] In the above scheme, when the electrolyte includes vinylene carbonate and fluoroethylene carbonate, the performance of the battery cell 3 can be improved by making the mass contents of vinylene carbonate and fluoroethylene carbonate 0.5%-5% and 0.1%-3% respectively.

[0258] Specifically, based on the total mass of the electrolyte, the mass content of vinylene carbonate can be 0.5%, 1.3%, 2%, 3%, 4%, 5% or any value within the above range, and the mass content of fluoroethylene carbonate can be 0.1%, 0.5%, 0.9%, 1.4%, 1.9%, 2%, 3% or any value within the above range.

[0259] In some embodiments, the electrolyte comprises vinylene carbonate and fluoroethylene carbonate; based on the total mass of the electrolyte, the mass content of vinylene carbonate is 2.5%-5% and the mass content of fluoroethylene carbonate is 1%-3%.

[0260] In the above scheme, when the electrolyte includes vinylene carbonate and fluoroethylene carbonate, the performance of the battery cell 3 can be further improved by making the mass contents of vinylene carbonate and fluoroethylene carbonate 2.5%-5% and 1%-3% respectively.

[0261] In some embodiments, the electrolyte satisfies at least one of the following conditions: the viscosity of the electrolyte at 20°C-30°C is 2.3 mPa·s-3.5 mPa·s; the conductivity of the electrolyte at 20°C-30°C is 10 mS / cm-18.5 mS / cm.

[0262] In the above scheme, by making the electrolyte meet the above conditions, the battery cell 3 has good conductivity and low internal resistance.

[0263] Specifically, at 20℃-30℃, the viscosity of the electrolyte can be 2.3 mPa·s, 2.5 mPa·s, 2.8 mPa·s, 3 mPa·s, 3.5 mPa·s or any value within the above range, and the conductivity of the electrolyte can be 10 mS / cm, 12 mS / cm, 15 mS / cm, 16 mS / cm, 18.5 mS / cm or any value within the above range.

[0264] Specifically, the viscosity of the electrolyte can be detected by the following methods: the detection can be carried out using equipment and methods known in the art, such as referring to GB / T 10247-2008 "Viscosity Measurement Methods", using a DV-2TLV instrument, taking a certain amount of electrolyte sample, injecting it into the viscometer, and calculating the viscosity of the electrolyte based on the reading of the rotational viscometer.

[0265] Specifically, the conductivity of an electrolyte can be detected using the following methods: Equipment and methods known in the art can be employed. A commonly used standard solution is potassium chloride solution, whose conductivity has accurate known values ​​at different temperatures and concentrations. The electrolyte to be tested should be thoroughly stirred to ensure uniform composition and concentration. Record the measured conductivity value, measurement temperature, electrolyte composition and concentration, and other relevant information.

[0266] In some embodiments, the electrolyte satisfies at least one of the following conditions: the viscosity of the electrolyte at 20°C-30°C is 2.3 mPa·s-3.5 mPa·s; the conductivity of the electrolyte at 20°C-30°C is 14 mS / cm-17.5 mS / cm.

[0267] In the above scheme, by making the electrolyte meet the above conditions, the battery cell 3 has better conductivity and lower internal resistance.

[0268] In some embodiments, the negative electrode 60 satisfies at least one of the following conditions: the porosity of the negative electrode 60 is 25%-60%; the compaction density of the negative electrode 60 at 0% SOC is 1.65 g / cm³. 3 -1.75g / cm 3 .

[0269] In the above scheme, the negative electrode sheet 60 has a more suitable porosity and compaction density, and the battery cell 3 has a more suitable energy density and cycle performance.

[0270] As an example, a battery cell 3 with 0% SOC can be obtained by the following method. Specifically, the battery cell 3 is first charged to 3.65V at a constant current of 0.3C, then charged to 0.05C at a constant voltage of 3.65V, and finally discharged to 2.5V to obtain a battery cell 3 with 0% SOC. Afterwards, the battery cell 3 is disassembled to obtain the electrode (e.g., the positive electrode), and the compaction density of the electrode is tested.

[0271] Specifically, the porosity of the negative electrode sheet 60 can be 25%, 28%, 30%, 32%, 35%, or any value within the above range.

[0272] Specifically, at 0% SOC, the compaction density of the negative electrode sheet 60 can be 1.65 g / cm³. 3 1.68g / cm 3 1.7g / cm 3 1.72g / cm 3 1.75g / cm 3 Or any value within the above range.

[0273] Specifically, the porosity of the electrode sheet can be detected by the following method: Take the negative electrode sheet as a sample, place the sample cup containing the sample in a true density tester, seal the test system, introduce helium gas according to the procedure, detect the gas pressure in the sample chamber and expansion chamber, calculate the true volume V1 according to PV=nRT, and then calculate the porosity using (V2-V1) / V2×100%, where the apparent volume V2=S×H×A, S is the sample area, H is the sample thickness, and A is the number of samples.

[0274] Specifically, the compaction density of the electrode can be detected by the following method: Remove the negative electrode from the lithium-ion battery cell and measure the electrode thickness and current collector thickness respectively. Take an electrode of a certain area, measure its area, and weigh the mass of the film layer on the current collector after removing the current collector. Calculate the electrode surface density based on this area and mass. The compaction density of the electrode is calculated as: Electrode surface density / (Electrode thickness - Current collector thickness).

[0275] In some embodiments, the volume average particle size of graphite is Dv50. 1 The size is 7μm-15μm.

[0276] Dv50 can refer to the particle size at which the cumulative particle size distribution number of a sample reaches 50%, meaning that 50% of the particles are smaller than Dv50. Here, Dv501 is used to distinguish it from other Dv50 values, representing the volume average particle size of different substances.

[0277] In the above scheme, when the volume average particle size of graphite in the negative electrode 60 is DDv50 1With a thickness of 7μm-15μm, it can meet the requirements of fast-charging battery systems and improve the performance of battery cells 3.

[0278] Specifically, the volume average particle size of graphite can be 7 μm, 9 μm, 11.5 μm, 13 μm, 15 μm or any value within the above range.

[0279] Specifically, the volume average particle size of materials can be determined using the following methods: A particle size analyzer-laser diffraction method can be employed. Specifically, refer to standard GB / T19077-2016, using a laser diffraction scattering particle size analyzer, and perform the measurement according to the manufacturer's instructions. For example, take an appropriate amount of sample (first additive, second additive, or lithium phosphate). 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 volume particle size of the sample material. Take an appropriate amount of the sample to be tested (ensuring a sample concentration of 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, determine the sample according to GB / T19077-2016 / ISO 13320:2009 standard.

[0280] In some embodiments, the volume average particle size of graphite is Dv50. 1 It is 9μm-12μm.

[0281] In the above scheme, when the volume average particle size Dv50 of the graphite in the negative electrode 60 1 With a thickness of 9μm-12μm, the performance of the battery cell 3 can be further improved.

[0282] In some embodiments, the lithium phosphate includes primary particles and secondary particles formed by the agglomeration of the primary particles, wherein the average longest diameter of the primary particles is 100 nm to 500 nm and the average longest diameter of the secondary particles is 1 μm to 2 μm.

[0283] A primary particle refers to the smallest unit of a particle within a certain observation range. A primary particle may contain defects of any form, but it is impossible to define smaller particles within a primary particle. Primary particles may aggregate under physical forces such as van der Waals forces, but such aggregation is easily disaggregated under external forces such as ultrasound, stirring, and rolling, so that the main component of lithium phosphate in the film layer is still primary particles.

[0284] Secondary particles refer to particles formed by the successive aggregation of particles.

[0285] In the above scheme, when the lithium-containing phosphate meets the above limitations, such lithium iron phosphate has a suitable size, which facilitates the insertion and extraction of lithium ions and helps the battery cell 3 to achieve its capacity.

[0286] Specifically, the average longest diameter of the primary particles of lithium iron phosphate can be 100nm, 150nm, 200nm, 280nm, 350nm, 400nm, 500nm or any value within the above range; the average longest diameter of the secondary particles of lithium iron phosphate can be 1μm, 1.2μm, 1.45μm, 1.6μm, 1.8μm, 2μm or any value within the above range.

[0287] In some embodiments, lithium phosphates include those with the general formula Li x2 D y2 Me a M b P 1-c X c Y z2 The compounds, wherein 0.5≤x²≤1.3, 0≤y²≤1.3, and 0.9≤x²+y²≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z²≤5; D includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of Cl, C, and N; Y includes one or more of O and F.

[0288] Specifically, in the general formula for lithium phosphate, x2 can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.3 or any of the above values; y2 can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.3 or any of the above values; a can be 0.9, 1, 1.2, 1.3, 1.4, 1.5 or any of the above values; b can be 0, 0.1, 0.2, 0.3, 0.4, 0.5 or any of the above values; c can be 0, 0.1, 0.2, 0.3, 0.4, 0.5 or any of the above values; and z2 can be 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5 or any of the above values.

[0289] In the above scheme, during the charging and discharging process of battery cell 3, the molar content of lithium, oxygen and other elements in lithium phosphate changes within a certain range.

[0290] In some embodiments, the lithium phosphate includes LiFePO4.

[0291] In the above scheme, using LiFePO4 as the positive electrode active material in battery cell 3 is beneficial to the widespread production of battery cell 3.

[0292] During the charging and discharging process, lithium (Li) is deintercalated and consumed in battery cell 3. The molar content of Li in the lithium-containing phosphate varies depending on the discharge state of battery cell 3. In the examples of lithium-containing phosphates in this application, the molar content of Li refers to the initial state of the material, i.e., the state before feeding. After charge-discharge cycles, the molar content of Li changes when the lithium-containing phosphate is applied to the battery system. Similarly, the molar content of O in the examples of lithium-containing phosphates in this application is only an ideal value. Lattice oxygen release causes changes in the molar content of O, and the actual molar content of O will fluctuate.

[0293] In some embodiments, at least a portion of the surface of the lithium phosphate contains carbon.

[0294] As an example, at least a portion of the surface of the lithium phosphate is provided with a coating layer, which includes carbon elements. The presence of a carbon-containing coating layer improves the conductivity of the lithium phosphate, facilitating the utilization of the capacity of the battery cell 3.

[0295] In the above scheme, by coating the surface of lithium phosphate with carbon elements, it is beneficial to improve the conductivity of lithium phosphate and maximize the capacity of battery cell 3, so that battery cell 3 has a high capacity.

[0296] In some implementations, the carbon content on the surface of the lithium phosphate is 1%-2% based on the total mass of the lithium phosphate.

[0297] In the above scheme, the surface carbon content of the lithium phosphate is 1%-2%, which can improve the conductivity of the lithium phosphate and thus improve the capacity utilization of the battery cell.

[0298] Specifically, based on the total mass of lithium phosphate, the mass content of carbon on the surface of lithium phosphate can be 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, or any value within the above range.

[0299] In some embodiments, the positive electrode film 502 satisfies at least one of the following conditions: the volume average particle size Dv50 of the lithium transition metal oxide is... 2The particle size ranges from 0.8 μm to 5 μm; the volume average particle size of nickel-containing metal oxides is Dv50. 3 The particle size is 3μm-30μm; the volume average particle size of lithium phosphate is Dv50. 4 The range is 2μm-20μm.

[0300] In the above scheme, by ensuring that the volume average particle size Dv50 of lithium-containing transition metal oxides, nickel-containing metal oxides, and lithium-containing phosphates meets the above requirements, the performance of the battery cell 3 can be improved.

[0301] Specifically, the volume average particle size Dv50 of the lithium-containing transition metal oxide can be 0.8 μm, 1.2 μm, 1.8 μm, 2.5 μm, 3 μm, 4 μm, 5 μm or any value within the above range.

[0302] Specifically, the volume average particle size Dv50 of the nickel-containing metal oxide can be 3 μm, 8 μm, 10 μm, 15 μm, 20 μm, 26 μm, 30 μm or any value within the above range.

[0303] Specifically, the volume average particle size Dv50 of lithium phosphate can be 2μm, 5μm, 10μm, 14μm, 16μm, 20μm or any value within the above range.

[0304] In some embodiments, the positive electrode film 502 satisfies at least one of the following conditions: the volume average particle size Dv50 of the lithium transition metal oxide is... 2 The particle size is 1μm-3μm; the volume average particle size of nickel-containing metal oxides is Dv50. 3 The particle size is 7μm-20μm; the volume average particle size of lithium phosphate is Dv50. 4 The size is 5μm-15μm.

[0305] In the above scheme, by ensuring that the volume average particle size Dv50 of lithium-containing transition metal oxides, nickel-containing metal oxides, and lithium-containing phosphates meets the above requirements, the performance of the battery cell 3 can be further improved.

[0306] In some embodiments, the end cap assembly 32 includes electrode terminals 322, as shown in FIG3. 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.

[0307] The lithium-ion battery cell 3 also includes a connecting member 34 for connecting the tab 331 and the electrode terminal 322 of the electrode assembly 33. For example, one connecting member 34 is used to connect the tab of the positive electrode and the positive electrode terminal, and another connecting member 34 is used to connect the tab of the negative electrode and the negative electrode terminal.

[0308] [Positive electrode plate]

[0309] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes a positive electrode active material, which includes a lithium phosphate.

[0310] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0311] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0312] In some embodiments, the positive electrode film layer further includes a binder. As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0313] In some embodiments, the positive electrode film layer further includes a conductive agent. As an example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0314] In one embodiment, the positive electrode sheet can be prepared by forming a positive electrode slurry using the components described above. For example, the positive electrode active material, conductive agent, binder, and any other components are dispersed in a solvent (e.g., N-methylpyrrolidone) to form the positive electrode slurry. The positive electrode slurry is then coated onto a positive electrode current collector, and after drying, cold pressing, and other processes, the positive electrode sheet is obtained.

[0315] [Negative electrode plate]

[0316] The negative electrode includes a negative current collector and a negative electrode film layer disposed on the negative current collector.

[0317] 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.).

[0318] The negative electrode film layer may also optionally include a binder. As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0319] 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.

[0320] In one embodiment, the negative electrode sheet can be prepared by forming a negative electrode slurry using the components described above. For example, the negative electrode active material, conductive agent, binder, and any other components are dispersed in a solvent (e.g., deionized water) to form the negative electrode slurry. The negative electrode slurry is then coated onto the positive electrode current collector, and after drying, cold pressing, and other processes, the negative electrode sheet is obtained.

[0321] [Isolation Component]

[0322] The separator is used to separate the positive electrode and the negative electrode. This application does not impose any particular restrictions on the type of separator; for example, any known porous membrane with good chemical and mechanical stability can be selected.

[0323] In one embodiment, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0324] This application provides a battery device, including the battery cell in any of the above embodiments.

[0325] This application provides an electrical device including a battery cell or battery device as described in any of the above embodiments, wherein the battery cell or battery device is used to store or provide electrical energy.

[0326] 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.

[0327] [Example]

[0328] [Example 1]

[0329] (1) Preparation of positive electrode sheet

[0330] The positive electrode active material lithium iron phosphate (LiFePO4), lithium-containing transition metal oxide (Li5FeO4), nickel-containing metal oxide (Li2NiO2), positive electrode conductive agent Super P, positive electrode binder polyvinylidene fluoride (PVDF), and dispersant were mixed in a mass ratio of 95:1.92:0.48:0.6:1.7:0.3. N-methylpyrrolidone (NMP) solvent was added, and the mixture was stirred under vacuum until the system became homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on both surfaces of the positive electrode current collector aluminum foil. The positive electrode current collector coated with slurry was dried and cold-pressed to obtain the positive electrode sheet. Among them, the average length of the longest diameter L1 of lithium transition metal oxide is 8 μm, the specific capacity of 8 μm Li5FeO4 is 700 mAh / g, the average length of the longest diameter L2 of nickel metal oxide is 10 μm, the Dv50 of lithium transition metal oxide is 10 μm, the Dv50 of nickel metal oxide is 25 μm, and the Dv50 of lithium phosphate is 2 μm.

[0331] (2) Preparation of negative electrode sheet

[0332] Artificial graphite (negative electrode active material), Super P (negative electrode conductive agent), sodium carboxymethyl cellulose (thickener), and styrene-butadiene rubber (SBR) (negative electrode binder) were mixed in a mass ratio of 98:0.7:0.7:0.6. Deionized water was added as a solvent, and the mixture was stirred uniformly under vacuum to prepare a negative electrode slurry. The negative electrode slurry was then uniformly coated onto both surfaces of a copper foil current collector. After drying and cold pressing, the negative electrode sheet was obtained. The artificial graphite had a volume average particle size (Dv50) of 10.6 μm, the negative electrode film had a porosity of 29%, and the negative electrode sheet had a compaction density of 1.75 g / cm³ at 0% SOC. 3 .

[0333] (3) Preparation of the isolation membrane: The isolation membrane consists of a 5μm PE base membrane.

[0334] (4) Preparation of electrolyte: The electrolyte includes solvent and electrolyte salt. The solvent is ethyl acetate, a chain carboxylic acid ester solvent, and ethylene carbonate, a carbonate solvent, in a mass ratio of 1:1. The electrolyte salt is LiFSI and LiPF6. The additives are vinylene carbonate and fluoroethylene carbonate. The mass content of the chain carboxylic acid ester solvent E3 is 50%, the concentration of LiFSI is 0.3 mol / L, the concentration of LiPF6 is 0.8 mol / L, the mass percentage of vinylene carbonate is 3.5%, the mass percentage of fluoroethylene carbonate is 2.5%, the viscosity of the electrolyte at 25℃ is 3 mPa·s, and the conductivity at 25℃ is 15 mS / cm.

[0335] (5) Preparation of battery cells

[0336] The negative electrode, separator, and positive electrode are wound into an electrode assembly; the electrode assembly is placed in the housing, electrolyte is injected, and after standing and formation processes, a single battery cell is obtained.

[0337] In Example 1, the positive electrode film layer includes a positive electrode active material, a lithium-containing transition metal oxide, and a nickel-containing metal oxide. The positive electrode active material includes lithium iron phosphate. The lithium-containing transition metal oxide includes a substrate and a coating layer located on at least a portion of the surface of the substrate. The substrate includes Li5FeO4, and the coating layer includes carbon (C) with a thickness of 90 nm. The nickel-containing metal oxide includes Li2NiO2. Based on the total mass of the positive electrode film layer, the mass content of Li5FeO4 (E1) is 1.92%, the mass content of Li2NiO2 (E2) is 0.48%, and the mass ratio of Li2NiO2 to Li5FeO4 (E2 / E1) is 0.25.

[0338] [Example 2]

[0339] The difference between Example 2 and Example 1 is that the average length of the longest diameter L1 of Li5FeO4 in Example 2 is 40 μm, and the specific capacity of 40 μm Li5FeO4 is 620 mAh / g.

[0340] [Example 3]

[0341] The difference between Example 3 and Example 1 is that the average value of the longest diameter L2 of Li2NiO2 in Example 3 is 30 μm.

[0342] [Example 4]

[0343] The difference between Example 4 and Example 1 is that the mass content of the chain carboxylic acid ester solvent E3 in Example 4 is 60%.

[0344] [Example 5]

[0345] The difference between Example 5 and Example 1 is that the mass content of the chain carboxylic acid ester solvent, E3, is 32% in Example 5.

[0346] [Example 6]

[0347] The difference between Example 6 and Example 1 is that in Example 6, the mass content of Li5FeO4 is 2.22%, the mass content of Li2NiO2 is 0.18%, and the ratio of the mass content of Li2NiO2 to the mass content of Li5FeO4, E2 / E1, is 0.08.

[0348] [Example 7]

[0349] The difference between Example 7 and Example 1 is that in Example 7, the mass content of Li5FeO4 is 1.37%, the mass content of Li2NiO2 is 1.03%, and the ratio of the mass content of Li2NiO2 to the mass content of Li5FeO4, E2 / E1, is 0.75.

[0350] [Example 8]

[0351] The difference between Example 8 and Example 1 is that in Example 8, the mass content of Li5FeO4 is 1.78%, the mass content of Li2NiO2 is 0.62%, and the ratio of the mass content of Li2NiO2 to the mass content of Li5FeO4, E2 / E1, is 0.35.

[0352] [Example 9]

[0353] The difference between Example 9 and Example 8 is that the chain carboxylic acid ester solvent in Example 9 is methyl formate.

[0354] [Example 10]

[0355] The difference between Example 10 and Example 1 is that there is no carbonate solvent in Example 10.

[0356] [Example 11]

[0357] The difference between Example 11 and Example 1 is that the electrolyte salt in Example 11 is only lithium hexafluorophosphate.

[0358] [Example 12]

[0359] The difference between Example 12 and Example 1 is that the additive in Example 12 is only vinylene carbonate.

[0360] [Comparative Example 1]

[0361] The difference between Comparative Example 1 and Example 1 is that the positive electrode film in Comparative Example 1 does not contain a second additive, and the electrolyte does not contain chain carboxylic acid ester solvents.

[0362] [Comparative Example 2]

[0363] The difference between Comparative Example 2 and Example 1 is that the positive electrode film layer in Comparative Example 2 does not contain a second additive.

[0364] [Comparative Example 3]

[0365] The difference between Comparative Example 3 and Example 1 is that the positive electrode film layer in Comparative Example 3 does not contain the first additive and the second additive.

[0366] [Comparative Example 4]

[0367] The difference between Comparative Example 4 and Example 1 is that the mass content of the chain carboxylic acid ester solvent E3 in Comparative Example 4 is 5%.

[0368] [Comparative Example 5]

[0369] The difference between Comparative Example 5 and Example 1 is that the mass content of the chain carboxylic acid ester solvent E3 in Comparative Example 5 is 80%.

[0370] The following is a brief description of the testing methods for the physicochemical and performance parameters involved in the embodiments of this application. It should be understood that the following testing methods are only examples, and other testing methods known in the art can also be used for testing.

[0371] 1. Cycle life test method

[0372] At 25℃, the battery cell was charged at a constant current rate of 1 / 3C to 3.65V, then charged at a constant voltage rate until the current was less than or equal to 0.05C. After resting for 5 minutes, it was discharged at a constant current rate of 1C to 2.5V. This constitutes one charge-discharge cycle, and the discharge capacity of this cycle is recorded as the discharge capacity of the battery cell in the first cycle. The battery cell was subjected to 500 charge-discharge cycles using the above method, and the discharge capacity of each cycle was recorded.

[0373] The capacity retention rate of a single lithium-ion battery cell after 500 cycles at 25℃ and 0.33C / 1C = discharge capacity of the 500th cycle / discharge capacity of the 1st cycle × 100%.

[0374] 2. Testing methods for fast charging performance

[0375] Charging time test: At 25℃, the formed battery was charged at a constant current of 0.33C to 3.65V, and then charged at a constant voltage of 3.6V until the current dropped below 0.05C. After resting, it was discharged at 0.33C to 2.5V, and the initial capacity C0 was measured. Then, it was charged at 0.1C to 3.65V. The potential of the negative electrode was monitored by connecting the reference electrode and the negative electrode. When the potential of the negative electrode reached 0mV, even if the upper limit voltage of 3.65V had not been reached, it was allowed to rest for a moment, and then discharged at 0.33C to 2.5V. The charging capacity C before resting was recorded. x Subsequently, the charging capacity at different rates (0.2C, 0.5C, 1C, 2C, 3C, 4C) was measured using the same procedure to obtain the charging capacity at different rates. The charging capacity C at different rates was then calculated. x The ratio of SOC to C0 yields the upper limit of SOC for different charging rates. A plot is then created with SOC on the x-axis and the charging rate on the y-axis. After fitting the plot, the upper limit charging rate R for each 10% SOC can be obtained. x Based on the maximum charging rate R per 10% SOC x According to the formula: charging time per segment = 1 / R x The charging time is calculated by multiplying 60 by 0.1 and then summing the results. Please refer to the table below for the test results of the charging time.

[0376] Table 1. Experimental parameters of Examples 1-12 and Comparative Examples 1-5

[0377] As can be seen from Example 1 and Comparative Example 1, by adding a second additive to the positive electrode film layer, the amount of gas generated by the battery cell can be effectively reduced, thereby improving the cycle performance of the battery cell.

[0378] As shown in Example 1 and Comparative Examples 1-2, adding a first additive to the positive electrode film and a chain-like carboxylic acid ester solvent to the electrolyte exacerbates gas generation within the battery cell, further reducing its cycle performance. Therefore, by adding a second additive to the positive electrode film, the problem of increased gas generation in battery cells using highly conductive electrolytes can be effectively alleviated, thereby further improving the cycle performance of the battery cells.

[0379] As shown in Example 1 and Comparative Example 3, when no first additive is added to the positive electrode film layer and only a chain-like carboxylic acid ester solvent is added to the electrolyte, the battery cell exhibits lower gas production and better fast-charging performance, but its cycle performance is generally poor. By adding both the first and second additives to the positive electrode film layer, the battery cell can achieve a balance between cycle performance and fast-charging performance.

[0380] As can be seen from Examples 1, 4-5 and Comparative Examples 4-5, by making the mass content of chain carboxylic acid ester solvent in the electrolyte 32%-60%, the battery cell can achieve both good fast charging performance and cycle performance.

[0381] As can be seen from Examples 1 and 2, by making the average length of the lithium metal oxide particles 8μm-30μm on the longitudinal section of the thickness direction of the positive electrode sheet, the agglomeration of lithium metal oxide particles can be reduced, so that the lithium transition metal oxide can better replenish lithium ions, thereby improving the cycle performance of the battery cell.

[0382] As can be seen from Examples 1 and 3, by making the average longest diameter of the nickel-containing metal oxide 7μm-20μm on the longitudinal section of the thickness direction of the positive electrode sheet, the nickel-containing metal oxide with a smaller particle size can effectively improve the gas generation of the battery cell, thereby ensuring the cycle performance of the battery cell.

[0383] As can be seen from Examples 1 and 6-7, by maintaining the ratio of the mass content of nickel-containing metal oxide to the mass content of lithium-containing transition metal oxide at 0.1-0.4, the battery cell can have a smaller amount of gas production, reducing the impact of gas production on the cycle performance of the battery cell, and can also avoid the impact of nickel dissolution caused by excessive addition of nickel-containing metal oxide on the cycle performance of the battery cell.

[0384] As can be seen from Examples 1 and 8, by maintaining the ratio of the mass content of nickel metal oxide to the mass content of lithium-containing transition metal oxide at 0.15-0.25, the gas production of the battery cell can be further reduced to improve the cycle performance of the battery cell.

[0385] As can be seen from Examples 8 and 9, adding various substances as chain-like carboxylic acid ester solvents to the electrolyte can enable battery cells to achieve both fast charging performance and cycle performance.

[0386] As can be seen from Examples 1 and 10, adding chain carboxylic acid ester solvents and carbonate solvents to the electrolyte can enable battery cells to achieve both fast charging performance and cycle performance.

[0387] As can be seen from Examples 1 and 11, adding lithium difluorosulfonylimide and lithium hexafluorophosphate to the electrolyte can enable the battery to have good cycle performance while maintaining fast charging performance.

[0388] As can be seen from Examples 1 and 12, adding vinylene carbonate and fluoroethylene carbonate to the electrolyte can further improve the fast charging performance and cycle performance of the battery cells.

[0389] 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 includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a lithium phosphate, a first additive, and a second additive. The first additive includes a lithium transition metal oxide, and the second additive includes a nickel metal oxide. A negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, wherein the negative electrode film layer includes graphite; The electrolyte includes a chain-like carboxylic acid ester solvent, wherein the chain-like carboxylic acid ester solvent has a mass content of 32%-60% based on the total mass of the electrolyte.

2. The battery cell according to claim 1, characterized in that, On the longitudinal section along the thickness direction of the positive electrode sheet, the average longest diameter of the lithium-containing transition metal oxide is 8μm-30μm.

3. The battery cell according to claim 1 or 2, characterized in that, On the longitudinal section along the thickness direction of the positive electrode sheet, the average length of the longest diameter of the nickel-containing metal oxide is 7μm-20μm.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The lithium-containing transition metal oxide includes a substrate and a coating layer located on at least a portion of the surface of the substrate, the substrate comprising Li x1 N y1 O z1 Where 1≤x1≤6, 1≤y1≤3, 1≤z1≤6, and N includes at least one of Ni, Fe, Cu, Co, Mn, Al, and Na.

5. The battery cell according to claim 4, characterized in that, The matrix comprises Li5FeO4.

6. The battery cell according to claim 4 or 5, characterized in that, The matrix includes Li e FeO f ,0≤e≤5,0 <f≤4。 7. The battery cell according to any one of claims 4 to 6, characterized in that, The matrix includes Li h FeO n ,0≤h≤1,0 <n≤2。 8. The battery cell according to any one of claims 4 to 7, characterized in that, The coating layer includes at least one of C, Al, Zr, Si, B, S, and P.

9. The battery cell according to any one of claims 4 to 8, characterized in that, The thickness of the coating layer is 10nm-100nm.

10. The battery cell according to any one of claims 1 to 9, characterized in that, The nickel-containing metal oxide includes M m NiO d M includes at least one of Li, Na, and K, 0≤m≤2, 1≤d≤2.

11. The battery cell according to any one of claims 1 to 10, characterized in that, The nickel-containing metal oxide includes Li2NiO2.

12. The battery cell according to any one of claims 1 to 11, characterized in that, The nickel-containing metal oxide includes Li g NiO i ,0≤g≤2,0 <i≤2。 13. The battery cell according to any one of claims 1 to 12, characterized in that, The nickel-containing metal oxide includes NiO. q 0 <q≤2。 14. The battery cell according to any one of claims 1 to 13, characterized in that, The ratio of the mass content of the nickel-containing metal oxide to the mass content of the lithium-containing transition metal oxide is 0.1-0.

4.

15. The battery cell according to any one of claims 1 to 14, characterized in that, The mass ratio of the nickel-containing metal oxide to the lithium-containing transition metal oxide is 0.15-0.

25.

16. The battery cell according to any one of claims 1 to 15, characterized in that, Based on the total mass of the positive electrode film, the mass content of the lithium phosphate is 80%-97%.

17. The battery cell according to any one of claims 1 to 16, characterized in that, Based on the total mass of the positive electrode film, the mass content of the lithium-containing transition metal oxide is 0.1%-5%.

18. The battery cell according to any one of claims 1 to 17, characterized in that, Based on the total mass of the positive electrode film, the mass content of the nickel-containing metal oxide is 0.03%-2%.

19. The battery cell according to any one of claims 1 to 18, characterized in that, Within a voltage range of 2V-4.3V, the charging capacity of the lithium-containing transition metal oxide is 300mAh / g-800mAh / g.

20. The battery cell according to any one of claims 1 to 19, characterized in that, Within a voltage range of 2V-4.3V, the charging capacity of the lithium-containing transition metal oxide is 600mAh / g-700mAh / g.

21. The battery cell according to any one of claims 1 to 20, characterized in that, The chain-like carboxylic acid ester solvents include at least one of methyl formate, methyl acetate, ethyl acetate, ethyl propionate, and their fluorinated organic compounds.

22. The battery cell according to any one of claims 1 to 21, characterized in that, The electrolyte also includes carbonate solvents, which include at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Based on the total mass of the electrolyte, the mass content of the carbonate solvent is 12%-33%.

23. The battery cell according to claim 22, characterized in that, The carbonate solvents include at least one of ethylene carbonate and propylene carbonate.

24. The battery cell according to any one of claims 1 to 23, characterized in that, The electrolyte further includes an electrolyte salt, which includes at least one of fluorosulfonyl imide salt and lithium hexafluorophosphate; the fluorosulfonyl imide salt includes one or more of lithium bisfluorosulfonyl imide and lithium bistrifluoromethanesulfonate.

25. The battery cell according to claim 24, characterized in that, The electrolyte salt includes lithium difluorosulfonylimide and lithium hexafluorophosphate; In the electrolyte, the molar concentration of lithium bis(fluorosulfonyl)imide is 0.2 mol / L-0.5 mol / L, and the molar concentration of lithium hexafluorophosphate is 0.5 mol / L-1 mol / L.

26. The battery cell according to claim 24 or 25, characterized in that, The electrolyte salt includes lithium difluorosulfonylimide and lithium hexafluorophosphate; In the electrolyte, the molar concentration ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate is 0.2-0.

5.

27. The battery cell according to any one of claims 1 to 26, characterized in that, The electrolyte includes at least one of carbonate additives, sulfur-containing additives, and lithium salt additives.

28. The battery cell according to claim 27, characterized in that, The carbonate additives include at least one of vinylene carbonate and fluoroethylene carbonate.

29. The battery cell according to claim 27 or 28, characterized in that, The sulfur-containing additives include at least one of vinyl sulfate, vinyl disulfate, butene sulfite, 1,3-propanesulfonate lactone, vinyl sulfite, and methylene disulfonate.

30. The battery cell according to any one of claims 27 to 29, characterized in that, The lithium salt additives include at least one of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium dioxalate borate.

31. The battery cell according to any one of claims 27 to 30, characterized in that, Based on the total mass of the electrolyte, the total mass content of the carbonate additives, the sulfur-containing additives, and the lithium salt additives is 1%-10%.

32. The battery cell according to any one of claims 27 to 31, characterized in that, Based on the total mass of the electrolyte, the total mass content of the carbonate additives, the sulfur-containing additives, and the lithium salt additives is 3.5%-8%.

33. The battery cell according to any one of claims 28 to 32, characterized in that, The electrolyte comprises the vinylene carbonate and the fluoroethylene carbonate; Based on the total mass of the electrolyte, the mass content of vinylene carbonate is 0.5%-5%, and the mass content of fluoroethylene carbonate is 0.1%-3%.

34. The battery cell according to any one of claims 28 to 33, characterized in that, The electrolyte comprises the vinylene carbonate and the fluoroethylene carbonate; Based on the total mass of the electrolyte, the mass content of vinylene carbonate is 2.5%-5%, and the mass content of fluoroethylene carbonate is 1%-3%.

35. The battery cell according to any one of claims 1 to 34, characterized in that, The electrolyte satisfies at least one of the following conditions: The viscosity of the electrolyte at 20℃-30℃ is 2.3mPa·s-3.5mPa·s; The electrolyte has a conductivity of 10 mS / cm to 18.5 mS / cm at 20℃-30℃.

36. The battery cell according to any one of claims 1 to 35, characterized in that, The electrolyte satisfies at least one of the following conditions: The viscosity of the electrolyte at 20℃-30℃ is 2.3mPa·s-3.5mPa·s; The electrolyte has a conductivity of 14 mS / cm to 17.5 mS / cm at 20℃-30℃.

37. The battery cell according to any one of claims 1 to 36, characterized in that, The negative electrode sheet satisfies at least one of the following conditions: The porosity of the negative electrode sheet is 25%-60%; The compaction density of the negative electrode sheet at 0% SOC is 1.65 g / cm³. 3 -1.75g / cm 3 .

38. The battery cell according to any one of claims 1 to 37, characterized in that, The negative electrode sheet satisfies at least one of the following conditions: The porosity of the negative electrode sheet is 25%-35%; The compaction density of the negative electrode sheet at 0% SOC is 1.65 g / cm³. 3 -1.75g / cm 3 .

39. The battery cell according to any one of claims 1 to 38, characterized in that, The volume average particle size of the graphite is Dv50. 1 The size is 7μm-15μm.

40. The battery cell according to any one of claims 1 to 39, characterized in that, The volume average particle size of the graphite is Dv50. 1 It is 9μm-12μm.

41. The battery cell according to any one of claims 1 to 40, characterized in that, The lithium phosphate comprises primary particles and secondary particles formed by the aggregation of the primary particles. The average longest diameter of the primary particles is 100nm-500nm, and the average longest diameter of the secondary particles is 1μm-2μm.

42. The battery cell according to any one of claims 1 to 41, characterized in that, The lithium-containing phosphate includes those with the general formula Li x2 D y2 Me a M b P 1-c X c Y z2 The compounds, wherein 0.5≤x²≤1.3, 0≤y²≤1.3, and 0.9≤x²+y²≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z²≤5; D includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of Cl, C, and N; Y includes one or more of O and F.

43. The battery cell according to any one of claims 1 to 42, characterized in that, The lithium-containing phosphate includes LiFePO4.

44. The battery cell according to any one of claims 1 to 43, characterized in that, At least a portion of the surface of the lithium phosphate contains carbon.

45. The battery cell according to claim 44, characterized in that, Based on the total mass of the lithium phosphate, the mass content of carbon on the surface of the lithium phosphate is 1%-2%.

46. ​​The battery cell according to any one of claims 1 to 45, characterized in that, The positive electrode film layer satisfies at least one of the following conditions: The volume average particle size Dv50 of the lithium-containing transition metal oxide 2 The range is 0.8μm-5μm; The volume average particle size of the nickel-containing metal oxide is Dv50. 3 The thickness ranges from 3μm to 30μm. The volume average particle size of the lithium phosphate is Dv50. 4 The range is 2μm-20μm.

47. The battery cell according to any one of claims 1 to 46, characterized in that, The positive electrode film layer satisfies at least one of the following conditions: The volume average particle size Dv50 of the lithium-containing transition metal oxide 2 The size is 1μm-3μm; The volume average particle size of the nickel-containing metal oxide is Dv50. 3 The thickness ranges from 7μm to 20μm. The volume average particle size of the lithium phosphate is Dv50. 4 The size is 5μm-15μm.

48. A battery device, characterized in that, include: Multiple battery cells according to any one of claims 1 to 47.

49. An electrical appliance, characterized in that, include: Multiple battery cells according to any one of claims 1 to 47, or battery devices according to claim 48, wherein the battery cells or battery devices are used to store or provide electrical energy.

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