Battery cell, battery apparatus and electrical device

Abstract

A battery cell, a battery apparatus and an electrical 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, the positive electrode film layer comprising a positive electrode active material, a first additive and a second additive, the positive electrode active material comprising a lithium-containing phosphate, the first additive comprising a lithium-containing transition metal oxide, and the second additive comprising 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, the negative electrode film layer comprising a carbon material; and an electrolyte, comprising a carbon-containing ester compound and a sulfur-containing ester compound, wherein on the basis of the total mass of the electrolyte, the sum of the mass content of the carbon-containing ester compound and the mass content of the sulfur-containing ester compound is 2%-6%. The technical solution of the present application can improve the cycle performance of battery cells.

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 a 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 problems, and its purpose is to provide a battery cell with a 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 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 a positive active material, a first additive, and a second additive, the positive active material including a lithium phosphate, 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 a carbon material; and an electrolyte including a carbon-containing ester compound and a sulfur-containing ester compound; based on the total mass of the electrolyte, the sum of the mass content of the carbon-containing ester compound and the mass content of the sulfur-containing ester compound is 2%-6%.

[0007] In the above scheme, the first additive can release lithium ions to compensate for the loss of active lithium in the battery cell during cycling. The second additive can convert the oxygen free radicals generated by the delithiation of the first additive into oxygen, reducing the RH+ generated by oxygen free radicals and reducing the generation of hydrogen gas, thereby reducing the continuous corrosion of the SEI film by RH+ and improving the cycle performance of the battery cell. Carbon-containing and sulfur-containing ester compounds in the electrolyte can increase the proportion of organic components in the SEI film, thereby improving the stability of the SEI film and blocking the contact between RH+ and carbon materials to further mitigate side reactions, thereby further improving the cycle performance of the battery cell. That is, by adding lithium-containing transition metal oxides and nickel-containing metal oxides to the positive electrode film layer, and adding carbon-containing and sulfur-containing ester compounds to the electrolyte, the gas production of the battery cell can be reduced and the cycle performance of the battery cell can be improved.

[0008] In some possible implementations, the average longest diameter of the lithium-containing transition metal oxide is 4 μm-16 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 4 μm, the degree of side reactions of the lithium-containing transition metal oxide in the battery cell can be reduced and the production cost 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 16 μm, it is conducive to the insertion and extraction of lithium ions, thereby taking into account both 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 10 μm-40 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 10 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 40 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 one possible implementation, the average length of the longest diameter of the nickel-containing metal oxide is less than the average length of the longest diameter of the lithium-containing transition metal oxide.

[0013] In this embodiment, lithium-containing transition metal oxides generate oxygen free radicals while releasing lithium ions. These oxygen free radicals react with the electrolyte to generate RH+, thereby damaging the SEI. By making the average longest diameter of nickel-containing metal oxides smaller than that of lithium-containing transition metal oxides, smaller nickel-containing metal oxide particles can suppress the side reactions between lithium-containing transition metal oxides and the electrolyte.

[0014] In one possible implementation, 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≤4, 2≤z1≤10, and N includes at least one of Fe, Cu, Co, Mn, Al, and Na.

[0015] 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.

[0016] In some possible implementations, the matrix comprises Li5FeO4.

[0017] 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 cycle performance of the battery cell.

[0018] In some possible implementations, the matrix comprises Li e FeO f ,0≤e≤5,0 <f≤4。

[0019] 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.

[0020] In some possible implementations, the matrix comprises Li h FeO n ,0≤h≤1,0 <n≤2。

[0021] 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.

[0022] In one possible implementation, the coating layer comprises carbon.

[0023] In this embodiment, the first additive includes a matrix and a coating layer. The coating layer includes carbon elements. 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 generation 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.

[0024] In some possible implementations, the thickness of the coating layer is 5nm-50nm.

[0025] In this embodiment, by making the thickness of the coating layer 5nm-50nm, 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.

[0026] In one possible implementation, the thickness of the coating layer is 15nm-35nm.

[0027] In this embodiment of the application, by making the thickness of the coating layer 15nm-35nm, the ionic conductivity of the first additive and the kinetic performance of the battery cell can be further improved.

[0028] In one possible implementation, the carbon content in the coating layer is 0.2%-4% based on the total mass of the lithium-containing transition metal oxide.

[0029] In the above scheme, by making the mass ratio of carbon element in the coating layer 0.2%-4% of the total mass of lithium-containing transition metal oxide, the ionic conductivity of the first additive can be improved, and the lithium-containing transition metal oxide can be conveniently released to release lithium ions, thereby improving the performance of the battery cell.

[0030] In one possible implementation, the carbon content in the coating layer is 0.5%-2% based on the total mass of the lithium-containing transition metal oxide.

[0031] In the above scheme, by making the mass ratio of carbon element in the coating layer 0.5%-2% of the total mass of lithium transition metal oxide, the performance of the battery cell can be further improved.

[0032] In one possible implementation, the nickel-containing metal oxide includes M m NiOd M includes at least one of Li, Na, and K, 0≤m≤2, 1≤d≤2.

[0033] 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.

[0034] In some possible implementations, the nickel-containing metal oxide includes Li2NiO2.

[0035] 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.

[0036] In some possible implementations, the nickel-containing metal oxide includes Li g NiO i ,0≤g≤2,0 <i≤2。

[0037] 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.

[0038] In some possible implementations, the nickel-containing metal oxide includes NiO. q 0 <q≤2。

[0039] 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.

[0040] In one possible implementation, based on the total mass of the positive electrode film, the sum of the mass percentage of the lithium-containing transition metal oxide and the mass percentage of the nickel-containing metal oxide is 0.1%-5%.

[0041] In this embodiment, the positive electrode film layer includes a positive electrode active material, a lithium-containing transition metal oxide, and a nickel-containing metal oxide. By making the total mass percentage of the lithium-containing transition metal oxide and the nickel-containing metal oxide 0.1%-5%, the cycle performance of the battery cell can be improved while also taking into account the energy density of the battery cell.

[0042] In one possible implementation, based on the total mass of the positive electrode film, the sum of the mass percentage of the lithium-containing transition metal oxide and the mass percentage of the nickel-containing metal oxide is 0.5%-3.5%.

[0043] In this embodiment, the positive electrode film layer includes a positive electrode active material, a lithium-containing transition metal oxide, and a nickel-containing metal oxide. By making the total mass percentage of the lithium-containing transition metal oxide and the nickel-containing metal oxide 0.5%-3.5%, the cycle performance and energy density of the battery cell can be further balanced.

[0044] In one possible implementation, the nickel-containing metal oxide accounts for 3%-40% of the total mass of the lithium-containing transition metal oxide and the nickel-containing metal oxide.

[0045] In this embodiment, by making the mass proportion of nickel-containing metal oxides 3%-40% in the total mass of lithium-containing transition metal oxides and nickel-containing metal oxides, the nickel-containing metal oxides can more thoroughly convert the oxygen free radicals generated by the lithium-containing transition metal oxides, thereby reducing the gas production of the battery cell and improving the cycle performance of the battery cell.

[0046] In one possible implementation, the nickel-containing metal oxide accounts for 12%-25% of the total mass of the lithium-containing transition metal oxide and the nickel-containing metal oxide.

[0047] In this embodiment of the application, by making the mass proportion of nickel-containing metal oxide 12%-25% in the total mass of lithium-containing transition metal oxide and nickel-containing metal oxide, 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.

[0048] 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.

[0049] In the above scheme, at a voltage of 2V-4.3V, by using a lithium-containing transition metal oxide with a charging capacity of 300mAh / g-800mAh / g as the 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 effectively replenished, thereby improving the cycle performance of the battery cell.

[0050] 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.

[0051] 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, thereby improving the cycle performance of the battery cell.

[0052] In one possible implementation, the mass content of the carbon-containing ester compound is 0.5%-4% based on the total mass of the electrolyte.

[0053] In this embodiment, based on the total mass of the electrolyte, by making the mass content of carbon-containing ester compounds 0.5%-4%, the organic components in the SEI film can be increased, which helps to form a more stable SEI film. It can also increase the overall chemical stability of the electrolyte and reduce the possibility of its decomposition under high voltage, thereby improving the performance of the battery cell.

[0054] In one possible implementation, the mass content of the carbon-containing ester compound is 0.8%-2.4% based on the total mass of the electrolyte.

[0055] In this embodiment of the application, based on the total mass of the electrolyte, the performance of the battery cell can be further improved by making the mass content of carbon-containing ester compounds 0.8%-2.4%.

[0056] In one possible implementation, the mass content of the sulfur-containing ester compound is 0.2%-3% based on the total mass of the electrolyte.

[0057] In this embodiment, based on the total mass of the electrolyte, by making the mass content of sulfur-containing ester compounds 0.2%-3%, the organic components in the SEI film can be increased, which helps to form a more stable SEI film, and the chemical stability of the electrode / electrolyte interface can be enhanced, thereby comprehensively improving the performance of the battery cell.

[0058] In one possible implementation, the mass content of the sulfur-containing ester compound is 0.9%-1.8% based on the total mass of the electrolyte.

[0059] In this embodiment of the application, based on the total mass of the electrolyte, the performance of the battery cell can be further improved by making the mass content of sulfur-containing ester compounds 0.9%-1.8%.

[0060] In one possible implementation, after the battery cell has undergone 1200 cycles, the residual mass content of the carbon-containing ester compound is 0.3%-2% based on the total mass of the electrolyte.

[0061] In this embodiment, after 1200 cycles, the residual mass content of carbon-containing ester compounds is 0.3%-2%, which can be used to assist in the detection of SEI film stability.

[0062] In one possible implementation, after the battery cell has undergone 1200 cycles, the residual mass content of the sulfur-containing ester compound is 0.2%-1.8% based on the total mass of the electrolyte.

[0063] In this embodiment, after 1200 cycles, the residual mass content of sulfur-containing ester compounds is 0.2%-1.8%, which can be used to assist in the detection of the stability of the SEI film.

[0064] In one possible implementation, the carbon-containing ester compound includes at least one of vinylene carbonate and fluoroethylene carbonate.

[0065] In this embodiment, by selecting at least one of vinylene carbonate and fluoroethylene carbonate as a carbon-containing ester compound to be added to the electrolyte, the requirements of both assisting in the formation of a more stable SEI film and increasing the overall chemical stability of the electrolyte are met, thereby reducing its decomposition under high voltage.

[0066] In one possible implementation, the sulfur-containing ester compound includes at least one of vinyl sulfate, vinyl disulfate, butene sulfite, 1,3-propanesulfonate lactone, and vinyl sulfite.

[0067] In this embodiment, at least one of vinyl sulfate, vinyl disulfate, butene sulfite, 1,3-propanesulfonate lactone, and vinyl sulfite is selected as a sulfur-containing ester compound and added to the electrolyte. This satisfies the requirements of both assisting in the formation of a more stable SEI film and enhancing the chemical stability of the electrode / electrolyte interface.

[0068] 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.

[0069] 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.

[0070] In one possible implementation, the electrolyte salt comprises the fluorosulfonamide salt and the lithium hexafluorophosphate; based on the total mass of the electrolyte, the sum of the mass content of the fluorosulfonamide salt and the mass content of the lithium hexafluorophosphate is 7%-18%.

[0071] In this embodiment of the application, by making the total mass percentage of fluorosulfonyl imide salt and lithium hexafluorophosphate in the electrolyte 7%-18%, the conductivity and degree of ion dissociation of lithium ions can be improved.

[0072] In one possible implementation, the electrolyte salt comprises the fluorosulfonamide salt and the lithium hexafluorophosphate; based on the total mass of the electrolyte, the sum of the mass content of the fluorosulfonamide salt and the mass content of the lithium hexafluorophosphate is 10%-15%.

[0073] In this embodiment of the application, by making the combined mass percentage of fluorosulfonyl imide salt and lithium hexafluorophosphate in the electrolyte 10%-15%, the conductivity and degree of ion dissociation of lithium ions can be further improved.

[0074] In one possible implementation, the mass content of the fluorosulfonamide salt is 7%-10% based on the total mass of the electrolyte.

[0075] In this embodiment, lithium fluorosulfonylimide has advantages such as good stability, higher ion conduction ability and more lithium ion transference number. By making the mass content of lithium fluorosulfonylimide in the electrolyte 7%-10%, the performance of the battery cell can be further improved.

[0076] In this embodiment of the application, the mass content of lithium hexafluorophosphate is 3%-5% based on the total mass of the electrolyte.

[0077] In this embodiment, lithium hexafluorophosphate has advantages such as good solubility, high ion conductivity, high ion dissociation degree, and low cost. By making the mass content of lithium hexafluorophosphate in the electrolyte 3%-5%, the performance of the battery cell can be further improved.

[0078] In one possible embodiment, the electrolyte further includes a solvent comprising at least one of carbonate solvents or carboxylic acid ester solvents, wherein the carbonate solvent comprises at least one of cyclic carbonate solvents or linear carbonate solvents; based on the total mass of the electrolyte, the mass content of the cyclic carbonate solvent is 10%-50%, the mass content of the linear carbonate solvent is 50%-90%, and the mass content of the carboxylic acid ester solvent is 0%-20%.

[0079] In this embodiment, cyclic carbonate solvents ensure good solubility of lithium salts in the electrolyte, linear carbonate solvents improve the conductivity and long-term stability of the electrolyte, and carboxylic acid ester solvents improve the fluidity of the electrolyte, thus modifying the electrolyte's performance at low temperatures. In other words, by combining cyclic carbonate solvents, linear carbonate solvents, and carboxylic acid ester solvents in the electrolyte, the overall performance of the electrolyte can be improved, which helps to enhance the performance of the battery cells.

[0080] 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 3 μm and the average longest diameter of the secondary particles is 500 nm to 5 μm.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] In one possible implementation, the lithium-containing phosphate includes at least one of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0085] In the above scheme, using at least one of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4 as the positive electrode active material in the battery cell is beneficial to the widespread production of battery cells.

[0086] In one possible implementation, at least a portion of the surface of the lithium phosphate has an ion-conducting layer; the ion-conducting layer includes at least one element selected from C, Fe, Ti, Zr, Hf, Ge, or Sn.

[0087] In the above scheme, by setting an ion-conducting layer on the surface of lithium phosphate, the conductivity of lithium phosphate is improved, thereby improving the performance of the battery cell.

[0088] In one possible implementation, the lithium-ion conductive layer comprises 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, based on the total mass of the positive electrode active material, the carbon content in the lithium-ion conductive layer is 0.8%-2% by mass.

[0091] In this embodiment of the application, the surface carbon content of the lithium phosphate is 0.8%-2% by mass, 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... 1 The particle size is 4μm-25μm; the volume average particle size of the nickel-containing metal oxide is Dv50. 2 The particle size is 3μm-40μm; the volume average particle size of the lithium phosphate is Dv50. 3 The range is 0.2μm-8μm.

[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... 1 The particle size is 6μm-16μm; the volume average particle size of the nickel-containing metal oxide is Dv50. 2 The particle size is 8μm-20μm; the volume average particle size of the lithium phosphate is Dv50. 3 The range is 0.5μm-4μm.

[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 one possible implementation, the positive electrode sheet satisfies at least one of the following conditions: the porosity of the positive electrode sheet is 15%-30%; the one-sided density of the positive electrode sheet is 0.28 g / 1540.25 mm. 2 -0.42g / 1540.25mm 2 The compaction density of the positive electrode sheet at 0% SOC is 2.4 g / cm³. 3 -2.9g / cm 3 .

[0097] In this embodiment of the application, by ensuring that the porosity, unilateral density, and compaction density of the positive electrode sheet meet the above requirements, the performance of the battery cell can be improved.

[0098] In one possible implementation, the positive electrode sheet satisfies at least one of the following conditions: the porosity of the positive electrode sheet is 16%-21%; the density of the positive electrode sheet on one side is 0.3g / 1540.25mm. 2 -0.38g / 1540.25mm 2 The compaction density of the positive electrode sheet at 0% SOC is 2.55 g / cm³. 3 -2.8g / cm 3 .

[0099] In this embodiment of the application, by ensuring that the porosity, unilateral density, and compaction density of the positive electrode sheet meet the above requirements, the performance of the battery cell can be further improved.

[0100] In one possible implementation, the carbon material comprises graphite, which satisfies at least one of the following conditions: the volume average particle size Dv50 of the graphite. 4 The thickness is 5μm-30μm; the specific surface area of ​​the graphite is 1.2m². 2 / g-2.2m 2 / g.

[0101] In this embodiment of the application, when the volume average particle size and specific surface area of ​​graphite in the negative electrode sheet meet the above requirements, the needs of the battery system can be met, thereby improving the performance of the battery cell.

[0102] In one possible implementation, the negative electrode sheet satisfies at least one of the following conditions: the density of the negative electrode sheet on one side is 0.12 g / 1540.25 mm. 2 -0.2g / 1540.25mm 2 The compaction density of the negative electrode sheet at 0% SOC is 1.2 g / cm³. 3 -1.7g / cm 3 .

[0103] In this embodiment of the application, by ensuring that the single-sided density and compaction density of the negative electrode sheet meet the above requirements, the performance of the battery cell can be improved.

[0104] In one possible implementation, the battery cell further includes a separator having a thickness of 5 μm-12 μm.

[0105] In this embodiment of the application, by ensuring that the thickness of the separator meets the above requirements, the probability of battery capacity loss caused by excessive separator thickness can be reduced, as well as the production cost of battery cells and the risk of metal leaching and puncturing the separator can be reduced.

[0106] In a second aspect, a battery device is provided, comprising a battery cell as described in the first aspect and any possible implementation thereof.

[0107] 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

[0108] 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.

[0109] Figure 1 is a schematic diagram of a vehicle according to an embodiment of this application;

[0110] Figure 2 is a schematic diagram of the structure of a battery device according to an embodiment of this application;

[0111] Figure 3 is a schematic diagram of the structure of a battery cell according to an embodiment of this application;

[0112] Figure 4 is a schematic diagram of the positive electrode sheet according to an embodiment of this application;

[0113] Figure 5 is a schematic diagram of the negative electrode sheet according to an embodiment of this application.

[0114] 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, 501-Positive current collector, 502-Positive film, 60-Negative electrode, 601-Negative current collector, 602-Negative film.

[0115] The accompanying drawings are not drawn to scale. Detailed Implementation

[0116] 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.

[0117] 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.

[0118] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0119] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0120] 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.

[0121] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0122] Unless otherwise specified, the following terms have the following meanings. Any undefined terms have their technically accepted meanings.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] In some implementations, 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.

[0136] In some implementations, the battery device may be located within an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0137] The embodiments of this application will be described next.

[0138] The development of battery technology requires consideration of multiple design factors, such as energy density, cycle life, discharge capacity, fast charging performance, and reliability. Lithium phosphates, due to their high structural stability, are widely used in the positive electrode of battery cells. To further improve the initial cycle efficiency of battery cells, lithium transition metal oxides are added to the positive electrode to replenish active lithium ions. However, during the extraction of active lithium ions, lithium transition metal oxides generate oxygen free radicals. These oxygen free radicals react with the electrolyte to produce RH+, which further migrates through the electrolyte to the negative electrode side, "corroding" the SEI film and triggering adverse side reactions. This not only results in the generation of more hydrogen gas inside the battery cell, increasing battery safety risks, but also leads to the continuous consumption of active lithium during battery cycling, increasing the inorganic components in the SEI film. The continuously generated RH+ in the battery cell is more likely to attack the SEI film with a higher inorganic component content. This causes battery cells containing lithium transition metal oxide additives to continuously produce the aforementioned adverse side reactions, significantly reducing the cycle performance of the battery cells.

[0139] In view of the above, this application provides a battery cell, the battery cell comprising a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer comprising a positive active material, a first additive and a second additive, the first additive comprising a lithium-containing transition metal oxide and the second additive comprising a nickel-containing metal oxide; a negative electrode sheet, comprising 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 comprising a carbon material; an electrolyte comprising a carbon-containing ester compound and a sulfur-containing ester compound; based on the total mass of the electrolyte, the sum of the mass content of the carbon-containing ester compound and the mass content of the sulfur-containing ester compound is 2%-6%.

[0140] Although the mechanism is not yet clear, this application adds a second additive, a nickel-containing metal oxide, to the positive electrode. This nickel-containing metal oxide can catalyze the oxygen free radicals generated by the first additive, allowing more and faster conversion of oxygen free radicals into oxygen, reducing the amount of RH+ generated, optimizing the gas composition of the battery cell, reducing the continuous corrosion of the SEI film by RH+, and improving the cycle performance of the battery cell. Furthermore, although the RH+ concentration is reduced by adjusting the second additive, the nickel-containing metal oxide, there is still a risk of corrosion of the negative electrode SEI film (because the SEI film is continuously renewed during cycling). Therefore, this application further introduces appropriate amounts of carbon-containing ester compounds and sulfur-containing ester compounds to increase the proportion of organic components in the SEI film on the surface of the negative electrode active material, thereby improving the stability of the SEI film, blocking the contact between RH+ and the carbon material surface, further mitigating side reactions, and improving the cycle performance of the battery cell.

[0141] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use battery devices.

[0142] 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.

[0143] For ease of explanation, the following embodiments use a vehicle as an example of electrical equipment.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] The battery cell 3 can be a lithium-ion battery or a lithium metal battery.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] [Battery cell]

[0154] 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.

[0155] 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.

[0156] 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.

[0157] The positive electrode film 502 includes a positive electrode active material, a first additive, and a second additive. The positive electrode active material includes a lithium phosphate, the first additive includes a lithium transition metal oxide, and the second additive includes a nickel metal oxide.

[0158] 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.

[0159] 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).

[0160] 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).

[0161] Nickel-containing metal oxides include nickel and oxygen. In some embodiments, nickel-containing metal oxides may also include lithium.

[0162] 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.

[0163] 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.

[0164] The negative electrode film 602 includes a negative electrode active material, which includes carbon material; simply put, the negative electrode film 602 includes carbon material.

[0165] Carbon materials, as the negative electrode active material of battery cell 3, have high theoretical capacity, low operating voltage platform and good cycle performance.

[0166] The electrolyte, comprising carbon-containing ester compounds and sulfur-containing ester compounds, has a total mass content of 2%-6% for carbon-containing ester compounds and sulfur-containing ester compounds based on the total mass of the electrolyte.

[0167] During the cycling process of a battery cell, RH+ tends to attack the SEI film on the surface of the negative electrode active material, particularly those with a higher proportion of inorganic components. Therefore, improving the composition of the negative electrode SEI film is crucial for improving the cycle performance of the battery cell. Carbon-containing and sulfur-containing ester compounds have low film-forming potentials and can preferentially form films in the early stages of cycling, resulting in a dominant organic component in the negative electrode SEI film. This ensures that the subsequent SEI film renewal process maintains a suitable organic component ratio, reducing the damage caused by RH+ to the negative electrode SEI film. Furthermore, excessively high levels of carbon-containing and sulfur-containing ester compounds can lead to excessively high impedance in the SEI film, which is detrimental to battery cycle performance and rate performance.

[0168] This application adds a second additive, a nickel-containing metal oxide, to the positive electrode. This nickel-containing metal oxide catalyzes the oxygen free radicals generated by the first additive, causing more and faster conversion of oxygen free radicals into oxygen, reducing the amount of RH+ generated, optimizing the gas composition of the battery cell, reducing the continuous corrosion of the SEI film by RH+, and improving the cycle performance of the battery cell. Furthermore, although the RH+ concentration is reduced by adjusting the second additive, the nickel-containing metal oxide, there is still a risk of corrosion of the negative electrode SEI film (because the SEI film is continuously renewed during cycling). Therefore, this application further increases the proportion of organic components in the SEI film on the surface of the negative electrode active material by introducing appropriate amounts of carbon-containing ester compounds and sulfur-containing ester compounds, thereby improving the stability of the SEI film, blocking the contact between RH+ and the graphite surface, further mitigating side reactions, and improving the cycle performance of the battery cell. Therefore, by adding lithium-containing transition metal oxides and nickel-containing metal oxides to the positive electrode film, and adding carbon-containing ester compounds and sulfur-containing ester compounds to the electrolyte, and making the total mass content of carbon-containing ester compounds and sulfur-containing ester compounds in the electrolyte 2%-6%, the gas production of the battery cell can be reduced and the cycle performance of the battery cell can be improved.

[0169] Specifically, based on the total mass of the electrolyte, the sum of the mass contents of carbon-containing ester compounds and sulfur-containing ester compounds can be 2%, 2.8%, 3.5%, 4%, 4.5%, 5.1%, 6%, or any value within the above range.

[0170] In some embodiments, the average longest diameter of the lithium-containing transition metal oxide is 4 μm-16 μm on a longitudinal section along the thickness direction of the positive electrode 50.

[0171] 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.

[0172] In the above scheme, by making the average length of the lithium-containing transition metal oxide greater than or equal to 4 μm, the degree of side reaction of the lithium-containing transition metal oxide in the battery cell 3 can be reduced and the production cost 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 16 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.

[0173] 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 4μm, 6.5μm, 9.2μm, 10.8μm, 12μm, 13.9μm, 15μm, 16μm or any value within the above range.

[0174] In some embodiments, the average length of the longest diameter of the nickel-containing metal oxide is 10 μm to 40 μm on a longitudinal section along the thickness direction of the positive electrode 50.

[0175] 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.

[0176] In the above scheme, by making the average length of the nickel-containing metal oxide greater than or equal to 10 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 40 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.

[0177] 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 10μm, 14μm, 18μm, 22.5μm, 28μm, 30μm, 35μm, 40μm or any value within the above range.

[0178] In some embodiments, the average length of the longest diameter of the nickel-containing metal oxide is less than the average length of the longest diameter of the lithium-containing transition metal oxide.

[0179] In the above scheme, lithium-containing transition metal oxides generate oxygen free radicals while releasing lithium ions. These oxygen free radicals react with the electrolyte to generate RH+, thereby damaging the SEI film. By making the average longest diameter of nickel-containing metal oxides smaller than that of lithium-containing transition metal oxides, smaller nickel-containing metal oxide particles can suppress the side reactions between lithium-containing transition metal oxides and the electrolyte.

[0180] 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.

[0181] 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.

[0182] 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.

[0183] 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.

[0184] In some embodiments, the matrix comprises Li5FeO4.

[0185] 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 cycle performance of the battery cell 3.

[0186] 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.

[0187] In some embodiments, the matrix includes Li e FeO f ,0≤e≤5,0 <f≤4。

[0188] 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.

[0189] 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.

[0190] In some embodiments, the matrix includes Li h FeO n ,0≤h≤1,0 <n≤2。

[0191] 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.

[0192] 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.

[0193] It should be noted that, in the reverse stage, if Li5FeO4 and Li2NiO2 are not directly detected after disassembling the battery cell, but byproducts of Li5FeO4 (such as iron oxides) and byproducts of Li2NiO2 (such as nickel oxides) are detected, those skilled in the art can determine the presence of Li5FeO4 and Li2NiO2 in the battery cell before formation by the byproducts, and the battery cell is also within the scope of protection of this application.

[0194] In some implementations, the coating layer includes carbon.

[0195] In the above scheme, the first additive includes a matrix and a coating layer. The coating layer includes carbon elements. 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 generation 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.

[0196] In some implementations, the thickness of the coating layer is 5nm-50nm.

[0197] In the above scheme, by making the thickness of the coating layer 5nm-50nm, 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.

[0198] Specifically, the thickness of the coating layer can be 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 40nm, 50nm or any value within the above range.

[0199] In some implementations, the thickness of the coating layer is 15nm-35nm.

[0200] In the above scheme, by making the thickness of the coating layer 15nm-35nm, the ionic conductivity of the first additive and the kinetic performance of the battery cell can be further improved.

[0201] In some implementations, the carbon content in the coating layer is 0.2%-4% based on the total mass of the lithium-containing transition metal oxide.

[0202] Based on the total mass of lithium-containing transition metal oxides, when the mass content of carbon in the coating layer is greater than or equal to 0.2%, the carbon on the surface of the lithium-containing transition metal oxide can improve the conductivity of the lithium-containing transition metal oxide; when the mass content of carbon in the coating layer is less than or equal to 4%, it can reduce the probability that the lithium-containing transition metal oxide is difficult to release lithium ions due to excessive coating.

[0203] In the above scheme, by making the mass ratio of carbon element in the coating layer 0.2%-4% of the total mass of lithium transition metal oxide, the ionic conductivity of the first additive can be improved, and the lithium transition metal oxide can be conveniently released to release lithium ions, thereby improving the performance of the battery cell 3.

[0204] Specifically, based on the total mass of the lithium-containing transition metal oxide, the mass percentage of carbon in the coating layer can be 0.2%, 0.8%, 1%, 1.5%, 2%, 2.2%, 3%, 4%, or any value within the above range.

[0205] In some implementations, the carbon content in the coating layer is 0.5%-2% based on the total mass of the lithium-containing transition metal oxide.

[0206] In the above scheme, by making the mass ratio of carbon element in the coating layer 0.5%-2% of the total mass of lithium transition metal oxide, the performance of the battery cell 3 can be further improved.

[0207] 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.

[0208] When cell 3 is a lithium battery cell, M can be Li; when cell 3 is a sodium battery cell, M can be Na, and so on.

[0209] When m is 0, the nickel-containing metal oxide can be nickel oxide; when m is greater than 0, the nickel-containing metal oxide can be a lithium-containing nickel metal oxide; when 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.

[0210] 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.

[0211] Specifically, in the general formula M m NiO dIn 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.

[0212] In some embodiments, the nickel-containing metal oxide includes Li2NiO2.

[0213] 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.

[0214] 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.

[0215] In some embodiments, the nickel-containing metal oxide includes Li g NiO i ,0≤g≤2,0 <i≤2。

[0216] 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.

[0217] 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.

[0218] In some embodiments, the nickel-containing metal oxide includes NiO. q 0 <q≤2。

[0219] 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.

[0220] In some implementations, based on the total mass of the positive electrode film 502, the sum of the mass percentage of lithium transition metal oxide and the mass percentage of nickel metal oxide is 0.1%-5%.

[0221] In the above scheme, the positive electrode film layer 502 includes a positive electrode active material, a lithium-containing transition metal oxide and a nickel-containing metal oxide. By making the total mass ratio of the lithium-containing transition metal oxide and the nickel-containing metal oxide 0.1%-5%, the cycle performance of the battery cell 3 can be improved, while also taking into account the energy density of the battery cell 3.

[0222] Specifically, based on the total mass of the positive electrode film layer 502, the sum of the mass percentage of lithium transition metal oxide and the mass percentage of nickel metal oxide can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, or any value within the above range.

[0223] In some implementations, based on the total mass of the positive electrode film 502, the sum of the mass percentages of lithium transition metal oxide and nickel metal oxide is 0.5%-3.5%.

[0224] In the above scheme, the positive electrode film layer 502 includes a positive electrode active material, a lithium-containing transition metal oxide and a nickel-containing metal oxide. By making the total mass ratio of the lithium-containing transition metal oxide and the nickel-containing metal oxide 0.5%-3.5%, the cycle performance and energy density of the battery cell 3 can be further balanced.

[0225] In some implementations, the mass percentage of nickel-containing metal oxides is 3%-40% based on the total mass of lithium-containing transition metal oxides and nickel-containing metal oxides.

[0226] In the above scheme, by making the mass ratio of nickel-containing metal oxides 3%-40% in the total mass of lithium-containing transition metal oxides and nickel-containing metal oxides, the nickel-containing metal oxides can more thoroughly convert the oxygen free radicals generated by lithium-containing transition metal oxides, thereby reducing the gas production of battery cell 3 and improving the cycle performance of battery cell 3.

[0227] Specifically, based on the total mass of lithium-containing transition metal oxides and nickel-containing metal oxides, the mass percentage of nickel-containing metal oxides can be 3%, 8%, 15%, 18%, 20%, 25%, 30%, 35%, 40%, or any value within the above range.

[0228] In some implementations, the mass percentage of nickel-containing metal oxides is 12%-25% based on the total mass of lithium-containing transition metal oxides and nickel-containing metal oxides.

[0229] In the above scheme, by making the mass ratio of nickel-containing metal oxides 12%-25% in the total mass of lithium-containing transition metal oxides and nickel-containing metal oxides, the nickel-containing metal oxides can more thoroughly convert the oxygen free radicals generated by lithium-containing transition metal oxides, which helps to further reduce the gas production of battery cell 3 and improve the cycle performance of battery cell 3.

[0230] 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.

[0231] 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, which is beneficial to improving the initial efficiency and energy density of the battery cell 3, but also effectively replenishes the lithium ion loss of the battery cell 3 during the cycle, so as to improve the cycle performance of the battery cell 3.

[0232] 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.

[0233] 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.

[0234] 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, as well as the cycle performance of the battery cell 3.

[0235] In some embodiments, the mass content of carbon-containing ester compounds is 0.5%-4% based on the total mass of the electrolyte.

[0236] Based on the total mass of the electrolyte, when the mass content of carbon-containing ester compounds is greater than or equal to 0.5%, the film quality of the SEI film at the negative electrode can be improved and the gas generation problem of the battery cell 3 in long-term cycling can be improved; when the mass content of carbon-containing ester compounds is less than or equal to 4%, the SEI film has a suitable thickness and will not cause impedance deterioration due to excessive SEI film thickness.

[0237] In the above scheme, based on the total mass of the electrolyte, by making the mass content of carbon-containing ester compounds 0.5%-4%, it is possible to increase the organic components in the SEI film, assist in the formation of a more stable SEI film, and also increase the overall chemical stability of the electrolyte, reducing the possibility of its decomposition under high voltage, thereby improving the performance of the battery cell 3.

[0238] Specifically, based on the total mass of the electrolyte, the mass content of carbon-containing ester compounds can be 0.5%, 0.9%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or any value within the above range.

[0239] In some embodiments, the mass content of carbon-containing ester compounds is 0.8%-2.4% based on the total mass of the electrolyte.

[0240] In the above scheme, based on the total mass of the electrolyte, the performance of the battery cell 3 can be further improved by making the mass content of carbon-containing ester compounds 0.8%-2.4%.

[0241] In some embodiments, the mass content of sulfur-containing ester compounds is 0.2%-3% based on the total mass of the electrolyte.

[0242] Based on the total mass of the electrolyte, when the mass content of sulfur-containing ester compounds is 0.2%, the film quality of the SEI film at the negative electrode can be improved; when the mass content of sulfur-containing ester compounds is less than or equal to 3%, the SEI film has a suitable thickness and will not cause impedance deterioration due to excessive SEI film thickness.

[0243] In the above scheme, based on the total mass of the electrolyte, by making the mass content of sulfur-containing ester compounds 0.2%-3%, it is possible to increase the organic components in the SEI film, assist in the formation of a more stable SEI film, and enhance the chemical stability of the electrode / electrolyte interface, so as to comprehensively improve the performance of the battery cell 3.

[0244] Specifically, based on the total mass of the electrolyte, the mass content of sulfur-containing ester compounds can be 0.2%, 0.8%, 1%, 1.5%, 1.9%, 2%, 2.5%, 3%, or any value within the above range.

[0245] In some embodiments, the mass content of sulfur-containing ester compounds is 0.9%-1.8% based on the total mass of the electrolyte.

[0246] In the above scheme, based on the total mass of the electrolyte, the performance of the battery cell 3 can be further improved by making the mass content of sulfur-containing ester compounds 0.9%-1.8%.

[0247] In some embodiments, after 1200 cycles, the residual mass content of carbon-containing ester compounds in the battery cell 3 is 0.3%-2% based on the total mass of the electrolyte.

[0248] In the above scheme, after 1200 cycles, the residual mass content of carbon-containing ester compounds is 0.3%-2%, which can be used to assist in the detection of SEI membrane stability.

[0249] Specifically, after 1200 cycles, the residual mass content of carbon-containing ester compounds in battery cell 3, based on the total mass of the electrolyte, is 0.3%, 0.5%, 0.9%, 1%, 1.3%, 1.6%, 2%, or any value within the above range.

[0250] In some embodiments, after 1200 cycles, the residual mass content of sulfur-containing ester compounds in the battery cell 3 is 0.2%-1.8% based on the total mass of the electrolyte.

[0251] In the above scheme, after 1200 cycles, the residual mass content of sulfur-containing ester compounds in battery cell 3 is 0.2%-1.8%, which can be used to assist in the detection of SEI film stability.

[0252] Specifically, after 1200 cycles, the residual mass content of sulfur-containing ester compounds in battery cell 3, based on the total mass of the electrolyte, is 0.2%, 0.4%, 0.8%, 1%, 1.3%, 1.6%, 2%, or any value within the above range.

[0253] In some embodiments, the carbon-containing ester compound includes at least one of vinylene carbonate and fluoroethylene carbonate.

[0254] In the above scheme, by selecting at least one of vinylene carbonate and fluoroethylene carbonate as a carbon-containing ester compound to be added to the electrolyte, the requirements of both assisting in the formation of a more stable SEI film and increasing the overall chemical stability of the electrolyte are met, thereby reducing its decomposition under high voltage.

[0255] In some embodiments, the sulfur-containing ester compound includes at least one of vinyl sulfate, vinyl disulfate, butene sulfite, 1,3-propanesulfonate lactone, and vinyl sulfite.

[0256] In the above scheme, by selecting at least one of vinyl sulfate, vinyl disulfate, butene sulfite, 1,3-propanesulfonate lactone, and vinyl sulfite as sulfur-containing ester compounds to be added to the electrolyte, it can both help form a more stable SEI film and enhance the chemical stability of the electrode / electrolyte interface.

[0257] 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.

[0258] The electrolyte salt may consist only of fluorosulfonyl imide salt, lithium hexafluorophosphate salt, or a mixture of fluorosulfonyl imide salt and lithium hexafluorophosphate.

[0259] 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.

[0260] 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.

[0261] In some embodiments, the electrolyte salt comprises a fluorosulfonamide salt and lithium hexafluorophosphate; the sum of the mass content of the fluorosulfonamide salt and the mass content of the lithium hexafluorophosphate is 7%-18% based on the total mass of the electrolyte.

[0262] In the above scheme, by making the combined mass percentage of fluorosulfonamide salt and lithium hexafluorophosphate in the electrolyte 7%-18%, the conductivity and degree of ion dissociation of lithium ions can be improved.

[0263] Specifically, based on the total mass of the electrolyte, the sum of the mass content of fluorosulfonamide salt and the mass content of lithium hexafluorophosphate can be 7%, 10%, 12%, 14.5%, 15%, 16%, 18%, or any value within the above range.

[0264] In some embodiments, the electrolyte salt comprises a fluorosulfonamide salt and lithium hexafluorophosphate; the sum of the mass content of the fluorosulfonamide salt and the mass content of the lithium hexafluorophosphate is 10%-15% based on the total mass of the electrolyte.

[0265] In the above scheme, by making the combined mass ratio of fluorosulfonamide salt and lithium hexafluorophosphate in the electrolyte 10%-15%, the conductivity and degree of ion dissociation of lithium ions can be further improved.

[0266] In some embodiments, the mass content of fluorosulfonamide salt is 7%-10% based on the total mass of the electrolyte.

[0267] In the above scheme, lithium fluorosulfonamide has advantages such as good stability, higher ion conduction ability and more lithium ion transference number. By making the mass content of lithium fluorosulfonamide in the electrolyte 7%-10%, the performance of battery cell 3 can be further improved.

[0268] Specifically, based on the total mass of the electrolyte, the mass content of the fluorosulfonamide salt can be 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or any value within the above range.

[0269] In some implementations, the lithium hexafluorophosphate content is 3%-5% based on the total mass of the electrolyte.

[0270] In the above scheme, lithium hexafluorophosphate has advantages such as good solubility, high ion conductivity, high ion dissociation degree and low cost. By making the mass content of lithium hexafluorophosphate in the electrolyte 3%-5%, the performance of battery cell 3 can be further improved.

[0271] Specifically, based on the total mass of the electrolyte, the mass content of lithium hexafluorophosphate can be 3%, 3.5%, 4%, 4.5%, 4.8%, 5%, or any value within the above range.

[0272] In some embodiments, the electrolyte further includes a solvent, which includes at least one of carbonate solvents or carboxylic acid ester solvents, wherein the carbonate solvent includes at least one of cyclic carbonate solvents or linear carbonate solvents; based on the total mass of the electrolyte, the mass content of the cyclic carbonate solvent is 10%-50%, the mass content of the linear carbonate solvent is 50%-90%, and the mass content of the carboxylic acid ester solvent is 0%-20%.

[0273] In this embodiment, cyclic carbonate solvents ensure good solubility of lithium salts in the electrolyte, linear carbonate solvents improve the conductivity and long-term stability of the electrolyte, and carboxylic acid ester solvents improve the fluidity of the electrolyte, thus modifying the electrolyte's performance at low temperatures. In other words, by combining cyclic carbonate solvents, linear carbonate solvents, and carboxylic acid ester solvents in the electrolyte, the overall performance of the electrolyte can be improved, which helps to enhance the performance of the battery cells.

[0274] Specifically, based on the total mass of the electrolyte, the mass content of the cyclic carbonate solvent can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any value within the above range.

[0275] Specifically, based on the total mass of the electrolyte, the mass content of linear carbonate solvent can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any value within the above range.

[0276] Specifically, based on the total mass of the electrolyte, the mass content of carboxylic acid ester solvent can be 0%, 5%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, or any value within the above range.

[0277] 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 3 μm and the average longest diameter of the secondary particles is 500 nm to 5 μm.

[0278] 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.

[0279] Secondary particles refer to particles formed by the successive aggregation of particles.

[0280] 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.

[0281] Specifically, the average longest diameter of the primary particles of lithium iron phosphate can be 100nm, 400nm, 600nm, 800nm, 1μm, 2μm, 3μm or any value within the above range; the average longest diameter of the secondary particles of lithium iron phosphate can be 500nm, 800nm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 5μm or any value within the above range.

[0282] 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 z2The compound, 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.

[0283] 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.

[0284] 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.

[0285] In some embodiments, the lithium phosphate includes at least one of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0286] In the above scheme, using at least one of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4 as the positive electrode active material in the battery cell is beneficial to the widespread production of battery cells.

[0287] 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.

[0288] In some embodiments, at least a portion of the surface of the lithium phosphate contains an ion-conducting layer; the ion-conducting layer includes at least one element selected from C, Fe, Ti, Zr, Hf, Ge, or Sn.

[0289] In the above scheme, by setting an ion-conducting layer on the surface of lithium phosphate, the conductivity of lithium phosphate is improved, thereby improving the performance of the battery cell.

[0290] In some implementations, the lithium-ion conductive layer includes carbon elements.

[0291] 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 the battery cell, so that the battery cell 3 has a high capacity.

[0292] In some implementations, the carbon content in the lithium-ion conductive layer is 0.8%-2% based on the total mass of the positive electrode active material.

[0293] In the above scheme, the surface carbon content of the positive electrode active material is 0.8%-2%, which can improve the conductivity of lithium phosphate and thus improve the capacity utilization of the battery cell.

[0294] Specifically, based on the total mass of the positive electrode active material, the mass content of carbon in the lithium-ion conductive layer can be 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, or any value within the above range.

[0295] 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... 1 The particle size ranges from 4 μm to 25 μm; the volume average particle size of nickel-containing metal oxides is Dv50. 2 The particle size is 3μm-40μm; the volume average particle size of lithium phosphate is Dv50. 3 The range is 0.2μm-8μm.

[0296] Dv50 can refer to the particle size at which the cumulative particle size distribution number (DV50) of a sample reaches 50%, meaning that particles smaller than DV50 account for 50% of the total particle size distribution. Here, Dv50... 1 Dv50 2 Dv50 3 It is used to distinguish different Dv50 values, representing the volume average particle size of different substances.

[0297] 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 cells can be further improved.

[0298] Specifically, the volume average particle size Dv50 of the lithium-containing transition metal oxide can be 4 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 20 μm, 25 μm or any value within the above range.

[0299] Specifically, the volume average particle size Dv50 of the nickel-containing metal oxide can be 3 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 40 μm or any value within the above range.

[0300] Specifically, the volume average particle size Dv50 of the lithium phosphate can be 0.2μm, 0.5μm, 1μm, 1.5μm, 2μm, 3μm, 3.5μm, 4μm, 8μm or any value within the above range.

[0301] 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... 1 The particle size ranges from 6 μm to 16 μm; the volume average particle size of nickel-containing metal oxides is Dv50. 2 The particle size is 8μm-20μm; the volume average particle size of lithium phosphate is Dv50. 3 The range is 0.5μm-4μm.

[0302] 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.

[0303] In some embodiments, the positive electrode 50 satisfies at least one of the following conditions: the porosity of the positive electrode 50 is 15%-30%; the one-sided density of the positive electrode 50 is 0.28 g / 1540.25 mm. 2 -0.42g / 1540.25mm 2 The compaction density of the positive electrode 50 at 0% SOC is 2.4 g / cm³. 3 -2.9g / cm3 .

[0304] 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 sheets (e.g., positive electrode sheet 50 or negative electrode sheet 60), and the compaction density of the electrode sheets is tested.

[0305] In the above scheme, by ensuring that the porosity, unilateral density, and compaction density of the positive electrode sheet 50 meet the above requirements, the performance of the battery cell 3 can be improved.

[0306] Specifically, the porosity of the positive electrode 50 can be 16%, 17%, 18%, 19%, 20%, 21%, or any value within the above range.

[0307] Specifically, the density of one side of the positive electrode 50 can be 0.3g / 1540.25mm. 2 0.32g / 1540.25mm 2 0.35g / 1540.25mm 2 0.365g / 1540.25mm 2 0.37g / 1540.25mm 2 0.38g / 1540.25mm 2 Or any value within the above range.

[0308] Specifically, the compaction density of the positive electrode 50 at 0% SOC can be 2.55 g / cm³. 3 2.6g / cm 3 2.7g / cm 3 2.72 g / cm 3 2.75g / cm 3 2.8g / cm 3 Or any value within the above range.

[0309] In some embodiments, the positive electrode 50 satisfies at least one of the following conditions: the porosity of the positive electrode 50 is 16%-21%; the density of one side surface of the positive electrode 50 is 0.3g / 1540.25mm. 2 -0.38g / 1540.25mm 2 The compaction density of the positive electrode 50 at 0% SOC is 2.55 g / cm³. 3 -2.8g / cm 3 .

[0310] In the above scheme, by ensuring that the porosity, unilateral density, and compaction density of the positive electrode sheet 50 meet the above requirements, the performance of the battery cell 3 can be further improved.

[0311] In some embodiments, the carbon material includes graphite, which satisfies at least one of the following conditions: the volume average particle size of graphite is Dv50. 4 Its thickness ranges from 5μm to 30μm; the specific surface area of ​​graphite is 1.2m². 2 / g-2.2m 2 / g.

[0312] In the above scheme, when the volume average particle size and specific surface area of ​​graphite in the negative electrode sheet 60 meet the above requirements, the needs of the battery system can be met, so as to improve the performance of the battery cell 3.

[0313] Specifically, the volume average particle size Dv50 of graphite can be 5μm, 10μm, 15μm, 18μm, 20μm, 25μm, 30μm or any value within the above range.

[0314] Specifically, the specific surface area of ​​graphite can be 1.2 m². 2 / g, 1.5m 2 / g, 1.7m 2 / g, 1.9m 2 / g、2m 2 / g, 2.2m 2 / g or any value within the above range.

[0315] In some embodiments, the negative electrode 60 satisfies at least one of the following conditions: the density of one side of the negative electrode 60 is 0.12 g / 1540.25 mm. 2 -0.2g / 1540.25mm 2 The compaction density of the negative electrode sheet 60 at 0% SOC is 1.2 g / cm³. 3 -1.7g / cm 3 .

[0316] In the above scheme, by ensuring that the single-sided density and compaction density of the negative electrode sheet 60 meet the above requirements, the performance of the battery cell 3 can be improved.

[0317] Specifically, the density of the negative electrode sheet 60 on one side can be 0.12 g / 1540.25 mm. 2 0.14g / 1540.25mm 2 0.16g / 1540.25mm 2 0.18g / 1540.25mm 2 0.2g / 1540.25mm 2 Or any value within the above range.

[0318] Specifically, the compaction density of the negative electrode sheet 60 at 0% SOC can be 1.2 g / cm³. 3 1.3g / cm 3 1.4g / cm 3 1.5g / cm 3 1.6g / cm 3 1.7g / cm 3 Or any value within the above range.

[0319] In some embodiments, the battery cell 3 further includes a separator with a thickness of 5 μm-12 μm.

[0320] When the thickness of the separator is greater than or equal to 5μm, the production cost of the battery cell 3 can be reduced, and it will not be easily punctured by the dissolved metal; when the thickness of the separator is less than or equal to 12μm, the capacity loss of the battery can be reduced.

[0321] In this embodiment of the application, by ensuring that the thickness of the separator meets the above requirements, the probability of battery capacity loss caused by excessive separator thickness can be reduced, as well as the production cost of battery cells and the risk of metal leaching and puncturing the separator can be reduced.

[0322] 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.

[0323] 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.

[0324] [Positive electrode plate]

[0325] 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.

[0326] 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.

[0327] 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.).

[0328] 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.

[0329] 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.

[0330] 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 processes such as drying and cold pressing, the positive electrode sheet is obtained.

[0331] [Negative electrode plate]

[0332] The negative electrode includes a negative current collector and a negative electrode film layer disposed on the negative current collector.

[0333] 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.).

[0334] 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.

[0335] 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.

[0336] 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 processes such as drying and cold pressing, the negative electrode sheet is obtained.

[0337] [Isolation Component]

[0338] 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.

[0339] 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.

[0340] This application provides a battery device, including the battery cell in any of the above embodiments.

[0341] 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.

[0342] 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.

[0343] [Example]

[0344] Example 1

[0345] (1) Preparation of positive electrode sheet

[0346] 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, and positive electrode binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 95:1.8:0.2:1:2. 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 longest diameter of the lithium-containing transition metal oxide is 8 μm, the specific capacity of 8 μm Li5FeO4 is 700 mAh / g, the average longest diameter of the nickel-containing metal oxide is 10 μm, the Dv50 of the lithium-containing transition metal oxide is 15 μm, the Dv50 of the nickel-containing metal oxide is 16 μm, and the Dv50 of the lithium phosphate is 2 μm; the porosity of the positive electrode film is 25%, and the single-sided density is 0.35 g / 1540.25 mm. 2 The compacted density at 0% SOC is 2.6 g / cm³. 3 .

[0347] (2) Preparation of negative electrode sheet

[0348] 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 96:1:1:2. Deionized water was added as a solvent, and the mixture was stirred evenly 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 graphite had a Dv50 of 13 μm and a specific surface area of ​​1.8 m². 2 / g, the single-sided density of the negative electrode film is 0.18g / 1540.25mm. 2 The compacted density at 0% SOC is 1.4 g / cm³. 3 .

[0349] (3) Preparation of the isolation membrane: The isolation membrane consists of a 12μm PE base membrane.

[0350] (4) Preparation of electrolyte: The electrolyte includes solvent and electrolyte salt. The solvent is ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate and propylene carbonate in a volume ratio of 30:50:15:5. The electrolyte salt is LiFSI and LiPF6, with a concentration of 0.8 mol / L for LiFSI and 0.4 mol / L for LiPF6. Then, 2% by mass of vinylene carbonate and 1.5% by mass of 1,3-propanesulfonic acid lactone are added to the electrolyte, with a total mass content of 3.5%.

[0351] (5) Preparation of battery cells

[0352] 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.

[0353] In Example 1, the positive electrode film layer includes a positive electrode active material, a first additive, and a second additive. The positive electrode active material includes lithium iron phosphate, the first additive includes a lithium-containing transition metal oxide, and the second additive includes a nickel-containing transition metal oxide. 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, the coating layer includes carbon (C) with a mass content of 3%, and the nickel-containing transition metal oxide includes Li2NiO2. Based on the total mass of the positive electrode film layer, the mass content of Li5FeO4 is 1.8%, the mass content of Li2NiO2 is 0.2%, and the sum of the mass contents of Li2NiO2 and Li5FeO4 is 0.1.

[0354] [Example 2]

[0355] The difference between Example 2 and Example 1 is that the longest diameter of Li5FeO4 in Example 2 is 20μm, and the specific capacity of 20μm Li5FeO4 is 650mAh / g.

[0356] [Example 3]

[0357] The difference between Example 3 and Example 1 is that the longest diameter of Li2NiO2 in Example 3 is 50 μm.

[0358] [Example 4]

[0359] The difference between Example 4 and Example 1 is that in Example 4, the mass content of Li5FeO4 is 1.95%, the mass content of Li2NiO2 is 0.05%, and the sum of the mass content of Li2NiO2 / Li5FeO4 and Li2NiO2 is 0.025.

[0360] [Example 5]

[0361] The difference between Example 5 and Example 1 is that in Example 5, the mass content of Li5FeO4 is 1%, the mass content of Li2NiO2 is 1%, and the mass content of Li2NiO2 / the sum of the mass contents of Li5FeO4 and Li2NiO2 is 0.5.

[0362] [Example 6]

[0363] The difference between Example 6 and Example 1 is that the carbon-containing ester compound in Example 6 is fluoroethylene carbonate, and the sulfur-containing ester compound is ethylene disulfate.

[0364] [Example 7]

[0365] The difference between Example 7 and Example 1 is that in Example 7, the mass content of vinylene carbonate is 1.1%, the mass content of 1,3-propanesulfonic acid lactone is 0.9%, and the sum of the mass content of vinylene carbonate and the mass content of 1,3-propanesulfonic acid lactone is 2%.

[0366] [Example 8]

[0367] The difference between Example 8 and Example 1 is that in Example 8, the mass content of vinylene carbonate is 3.5%, the mass content of 1,3-propanesulfonic acid lactone is 2.5%, and the sum of the mass content of vinylene carbonate and the mass content of 1,3-propanesulfonic acid lactone is 6%.

[0368] [Comparative Example 1]

[0369] The difference between Comparative Example 1 and Example 1 is that the positive electrode film in Comparative Example 1 contains only lithium transition metal oxide Li5FeO4 and does not contain nickel metal oxide Li2NiO2. The electrolyte does not contain vinylene carbonate and 1,3-propanesulfonic acid lactone.

[0370] [Comparative Example 2]

[0371] The difference between Comparative Example 2 and Example 1 is that no vinylene carbonate and 1,3-propanesulfonic acid lactone were added to the electrolyte in Comparative Example 2.

[0372] [Comparative Example 3]

[0373] The difference between Comparative Example 3 and Example 1 is that the positive electrode film in Comparative Example 3 contains only lithium transition metal oxide Li5FeO4 and does not contain nickel metal oxide Li2NiO2.

[0374] [Comparative Example 4]

[0375] The difference between Comparative Example 4 and Example 1 is that the mass content of vinylene carbonate in Comparative Example 4 is 8%, the mass content of 1,3-propanesulfonic acid lactone is 1.5%, and the sum of the mass content of vinylene carbonate and the mass content of 1,3-propanesulfonic acid lactone is 9.5%.

[0376] [Comparative Example 5]

[0377] The difference between Comparative Example 5 and Example 1 is that the mass content of vinylene carbonate in Comparative Example 5 is 2%, the mass content of 1,3-propanesulfonic acid lactone is 5%, and the sum of the mass content of vinylene carbonate and the mass content of 1,3-propanesulfonic acid lactone is 7%.

[0378] [Comparative Example 6]

[0379] The difference between Comparative Example 6 and Example 1 is that the mass content of vinylene carbonate in Comparative Example 6 is 1%, the mass content of 1,3-propanesulfonic acid lactone is 0.5%, and the sum of the mass content of vinylene carbonate and the mass content of 1,3-propanesulfonic acid lactone is 1.5%.

[0380] Table 1. Experimental parameters of Examples 1-8 and Comparative Examples 1-6

[0381] As shown in Example 1 and Comparative Examples 1-3, by adding Li2NiO2 as a second additive to the positive electrode film layer, the oxygen free radicals generated by the first additive can be converted into oxygen, thereby reducing the gas production of the battery cell and improving the cycle performance of the battery cell. Furthermore, by adding vinylene carbonate as a carbon-containing ester compound and 1,3-propanesulfonic acid lactone as a sulfur-containing ester compound to the electrolyte, the proportion of organic components in the SEI film can be increased, thereby improving the stability of the SEI film and further improving the cycle performance of the battery cell.

[0382] As can be seen from Examples 1 and 2, by making the average length of the lithium-containing metal oxide particles 4μm-16μm on the longitudinal section of the thickness direction of the positive electrode sheet, the agglomeration of lithium-containing metal oxide particles can be reduced, so that the lithium-containing transition metal oxide can better replenish lithium ions, thereby improving the cycle performance of the battery cell.

[0383] As can be seen from Examples 1 and 3, by making the average longest diameter of the nickel-containing metal oxide 10μm-40μm 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.

[0384] As can be seen from Examples 1 and 4-5, based on the total mass of lithium-containing transition metal oxides and nickel-containing metal oxides, by making the mass ratio of nickel-containing metal oxides 3%-40%, the nickel-containing metal oxides can effectively improve the gas generation problem and reduce the impact of excessive gas generation on the cycle performance of battery cells, while avoiding the impact of nickel dissolution caused by excessive addition of nickel-containing metal oxides on the cycle performance of battery cells.

[0385] As can be seen from Examples 1 and 6, the addition of various substances as carbon-containing ester compounds and sulfur-containing ester compounds to the electrolyte can improve the cycle performance of the battery cell.

[0386] As can be seen from Examples 1, 7-8 and Comparative Examples 4-6, based on the total mass of the electrolyte, by making the mass content of carbon-containing ester compounds 0.5%-4%, the mass content of sulfur-containing ester compounds 0.2%-3%, and the sum of the mass content of carbon-containing ester compounds and the mass content of sulfur-containing ester compounds 2%-6%, the SEI film can be of higher quality and moderate thickness, thereby improving the cycle performance of the battery cell.

[0387] 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.

[0388] 1. Cycle life test method

[0389] 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 800 charge-discharge cycles using the above method, and the discharge capacity of each cycle was recorded.

[0390] The capacity retention rate of a single lithium-ion battery cell after 800 cycles at 25℃ and 0.33C / 1C = discharge capacity of the 800th cycle / discharge capacity of the 1st cycle × 100%.

[0391] 2. Test of the average value of the longest diameter

[0392] The positive electrode sheet, which includes the first additive, the second additive, and the lithium iron phosphate material, is 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.

[0393] Specifically, the longest diameter of the first additive refers to the longest straight line that passes through the center point of the first additive and extends to the outer periphery of the particle; the longest diameter of the lithium iron phosphate material refers to the longest straight line that passes through the center point of the lithium iron phosphate material and extends to the outer periphery of the particle; and the longest diameter of the second additive refers to the longest straight line that passes through the center point of the second additive and extends to the outer periphery of the particle.

[0394] 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.

[0395] 3. Test method for coating thickness

[0396] Cut the positive electrode sheet along its thickness to expose the longitudinal section of the positive electrode film. By performing SEM testing on the longitudinal section of the positive electrode film, after 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 the thickness of the coating layer.

[0397] 4. Testing of specific components in the positive electrode film layer

[0398] The positive electrode film layer of the positive electrode can be scraped off, and the scraped material is added to aqua regia and digested under mechanical stirring for 30 minutes. The digested solution is then added to an ICAP7400 spectrometer to analyze the elemental composition. For example, for the positive electrode, the content of Ni, Fe, and P elements can be measured.

[0399] 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 the P and Fe elements.

[0400] 5. Testing of specific components in the electrolyte

[0401] Take a battery in any state, disassemble the battery electrodes, centrifuge and collect the free electrolyte, and test the composition and content by GC-MS gas chromatography quantitative analysis method for organic components.

[0402] 6. Testing of the mass content of electrolyte salts

[0403] The concentration of inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by 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 by ion chromatography.

[0404] 7. Test of volume average particle size

[0405] The volumetric particle size distribution can be determined using a particle size analyzer-laser diffraction method. Specifically, refer to standard GB / T19077-2016, using a laser diffraction scattering particle size analyzer, and perform measurements according to the manufacturer's instructions. For example, take an appropriate amount of sample (first 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 volumetric particle size of the sample material. Take an appropriate amount of the sample to be tested (the sample concentration should be 8-12% opacity), add 20 ml of deionized water, and simultaneously incubate for 5 minutes (53 kHz / 120 W) to ensure complete dispersion of the sample. Then, determine the sample according to GB / T19077-2016 / ISO 13320:2009 standard.

[0406] 8. Porosity testing of positive electrode sheets

[0407] Take the positive electrode as the sample, place the sample cup containing the sample in the 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.

[0408] 9. Testing of unilateral surface density and compacted density

[0409] The negative electrode sheet is removed from the lithium-ion battery cell, and the thickness of the electrode sheet and the thickness of the current collector are measured. A certain area of ​​the electrode sheet is taken, its area is measured, and the mass of the film layer on the current collector after removing the current collector is weighed. The electrode sheet surface density and the compaction density of the electrode sheet are calculated based on the area and mass: electrode sheet surface density / (electrode sheet thickness - current collector thickness).

[0410] 10. Specific surface area test

[0411] The specific surface area of ​​substances can be determined by the gas adsorption BET method, referring to the GB / T19587-2017 standard.

[0412] 11. Testing the thickness of the separator membrane

[0413] Take the release liner and measure it using a small handheld thickness gauge, referring to GB / T 6672-2001 or GB / T 20220-2006 standards.

[0414] 12. Measurement of gram capacity

[0415] This section uses the first additive as an example to introduce the specific capacity testing method. The first additive, conductive carbon Super P, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 7:2:1 and added to N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The positive electrode slurry is then coated onto aluminum foil and dried to obtain the positive electrode sheet. Using a conventional electrolyte for lithium iron phosphate batteries, the positive electrode sheet is assembled with a copper sheet to form a CR2025 coin cell. The coin cell is discharged at a constant current rate of 0.05C to 0.005V, and then charged at a constant current rate to 2.0V. The specific capacity is then measured. Specific capacity = coin cell capacity / mass of the first additive.

[0416] 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 positive active material, a first additive, and a second additive. The positive active material includes a lithium phosphate, 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 comprises a carbon material; The electrolyte comprises carbon-containing ester compounds and sulfur-containing ester compounds; based on the total mass of the electrolyte, the sum of the mass content of the carbon-containing ester compounds and the mass content of the sulfur-containing ester compounds is 2%-6%.

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 4μm-16μm.

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 10 μm-40 μm.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The average length of the longest diameter of the nickel-containing metal oxide is less than the average length of the longest diameter of the lithium-containing transition metal oxide.

5. The battery cell according to any one of claims 1 to 4, 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≤4, 2≤z1≤10, and N includes at least one of Fe, Cu, Co, Mn, Al, and Na.

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

7. The battery cell according to claim 5 or 6, characterized in that, The matrix includes Li e FeO f ,0≤e≤5,0 <f≤4。 8. The battery cell according to any one of claims 5 to 7, characterized in that, The matrix includes Li h FeO n ,0≤h≤1,0 <n≤2。 9. The battery cell according to any one of claims 5 to 8, characterized in that, The coating layer includes carbon.

10. The battery cell according to any one of claims 5 to 9, characterized in that, The thickness of the coating layer is 5nm-50nm.

11. The battery cell according to any one of claims 5 to 10, characterized in that, The thickness of the coating layer is 15nm-35nm.

12. The battery cell according to any one of claims 5 to 11, characterized in that, Based on the total mass of the lithium-containing transition metal oxide, the carbon content in the coating layer is 0.2%-4% by mass.

13. The battery cell according to any one of claims 5 to 12, characterized in that, Based on the total mass of the lithium-containing transition metal oxide, the carbon content in the coating layer is 0.5%-2% by mass.

14. The battery cell according to any one of claims 1 to 13, 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.

15. The battery cell according to any one of claims 1 to 14, characterized in that, The nickel-containing metal oxide includes Li2NiO2.

16. The battery cell according to any one of claims 1 to 15, characterized in that, The nickel-containing metal oxide includes Li g NiO i ,0≤g≤2,0 <i≤2。 17. The battery cell according to any one of claims 1 to 16, characterized in that, The nickel-containing metal oxide includes NiO. q 0 <q≤2。 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 sum of the mass percentage of the lithium-containing transition metal oxide and the mass percentage of the nickel-containing metal oxide is 0.1%-5%.

19. The battery cell according to any one of claims 1 to 18, characterized in that, Based on the total mass of the positive electrode film, the sum of the mass percentage of the lithium-containing transition metal oxide and the mass percentage of the nickel-containing metal oxide is 0.5%-3.5%.

20. The battery cell according to any one of claims 1 to 19, characterized in that, Based on the total mass of the lithium-containing transition metal oxide and the nickel-containing metal oxide, the mass percentage of the nickel-containing metal oxide is 3%-40%.

21. The battery cell according to any one of claims 1 to 20, characterized in that, Based on the total mass of the lithium-containing transition metal oxide and the nickel-containing metal oxide, the mass percentage of the nickel-containing metal oxide is 12%-25%.

22. The battery cell according to any one of claims 1 to 21, 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.

23. The battery cell according to any one of claims 1 to 22, 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.

24. The battery cell according to any one of claims 1 to 23, characterized in that, Based on the total mass of the electrolyte, the mass content of the carbon-containing ester compound is 0.5%-4%.

25. The battery cell according to any one of claims 1 to 24, characterized in that, Based on the total mass of the electrolyte, the mass content of the carbon-containing ester compound is 0.8%-2.4%.

26. The battery cell according to any one of claims 1 to 25, characterized in that, Based on the total mass of the electrolyte, the mass content of the sulfur-containing ester compound is 0.2%-3%.

27. The battery cell according to any one of claims 1 to 26, characterized in that, Based on the total mass of the electrolyte, the mass content of the sulfur-containing ester compound is 0.9%-1.8%.

28. The battery cell according to any one of claims 1 to 27, characterized in that, After 1200 cycles, the residual mass content of the carbon-containing ester compound in the battery cell is 0.3%-2% based on the total mass of the electrolyte.

29. The battery cell according to any one of claims 1 to 28, characterized in that, After 1200 cycles, the residual mass content of the sulfur-containing ester compounds in the battery cell is 0.2%-1.8% based on the total mass of the electrolyte.

30. The battery cell according to any one of claims 1 to 29, characterized in that, The carbon-containing ester compounds include at least one of vinylene carbonate and fluoroethylene carbonate.

31. The battery cell according to any one of claims 1 to 30, characterized in that, The sulfur-containing ester compounds include at least one of vinyl sulfate, vinyl disulfate, butene sulfite, 1,3-propanesulfonate lactone, and vinyl sulfite.

32. The battery cell according to any one of claims 1 to 31, 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.

33. The battery cell according to claim 32, characterized in that, The electrolyte salt includes the fluorosulfonylimide salt and the lithium hexafluorophosphate; Based on the total mass of the electrolyte, the sum of the mass content of the fluorosulfonamide salt and the mass content of the lithium hexafluorophosphate is 7%-18%.

34. The battery cell according to claim 32 or 33, characterized in that, The electrolyte salt includes the fluorosulfonylimide salt and the lithium hexafluorophosphate; Based on the total mass of the electrolyte, the sum of the mass content of the fluorosulfonamide salt and the mass content of the lithium hexafluorophosphate is 10%-15%.

35. The battery cell according to any one of claims 32 to 34, characterized in that, Based on the total mass of the electrolyte, the mass content of the fluorosulfonamide salt is 7%-10%.

36. The battery cell according to any one of claims 32 to 35, characterized in that, Based on the total mass of the electrolyte, the lithium hexafluorophosphate content is 3%-5%.

37. The battery cell according to any one of claims 1 to 36, characterized in that, The electrolyte further includes a solvent, which includes at least one of carbonate solvents or carboxylic acid ester solvents, and the carbonate solvent includes at least one of cyclic carbonate solvents or linear carbonate solvents; Based on the total mass of the electrolyte, the mass content of the cyclic carbonate solvent is 10%-50%, the mass content of the linear carbonate solvent is 50%-90%, and the mass content of the carboxylic acid ester solvent is 0%-20%.

38. The battery cell according to any one of claims 1 to 37, 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 100 nm to 3 μm, and the average longest diameter of the secondary particles is 500 nm to 5 μm.

39. The battery cell according to any one of claims 1 to 38, 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.

40. The battery cell according to any one of claims 1 to 39, characterized in that, The lithium-containing phosphate includes at least one of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

41. The battery cell according to any one of claims 1 to 40, characterized in that, At least a portion of the surface of the lithium-containing phosphate has a lithium-ion conductive layer; The lithium-ion conductive layer includes at least one element selected from C, Fe, Ti, Zr, Hf, Ge, or Sn.

42. The battery cell according to claim 41, characterized in that, The lithium-ion conductive layer includes carbon elements.

43. The battery cell according to claim 42, characterized in that, Based on the total mass of the positive electrode active material, the mass content of C element in the lithium-ion conductive layer is 0.8%-2%.

44. The battery cell according to any one of claims 1 to 43, 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 1 The thickness ranges from 4μm to 25μm. The volume average particle size of the nickel-containing metal oxide is Dv50. 2 The thickness ranges from 3μm to 40μm. The volume average particle size of the lithium phosphate is Dv50. 3 The range is 0.2μm-8μm.

45. The battery cell according to any one of claims 1 to 44, 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 1 The thickness ranges from 6μm to 16μm. The volume average particle size of the nickel-containing metal oxide is Dv50. 2 The thickness ranges from 8μm to 20μm. The volume average particle size of the lithium phosphate is Dv50. 3 The range is 0.5μm-4μm.

46. ​​The battery cell according to any one of claims 1 to 45, characterized in that, The positive electrode sheet satisfies at least one of the following conditions: The porosity of the positive electrode sheet is 15%-30%; The density of the positive electrode sheet on one side is 0.28 g / 1540.25 mm. 2 -0.42g / 1540.25mm 2 ; The compaction density of the positive electrode sheet at 0% SOC is 2.4 g / cm³. 3 -2.9g / cm 3 .

47. The battery cell according to any one of claims 1 to 46, characterized in that, The positive electrode sheet satisfies at least one of the following conditions: The porosity of the positive electrode sheet is 16%-21%; The density of the positive electrode sheet on one side is 0.3 g / 1540.25 mm. 2 -0.38g / 1540.25mm 2 ; The compaction density of the positive electrode sheet at 0% SOC is 2.55 g / cm³. 3 -2.8g / cm 3 .

48. The battery cell according to any one of claims 1 to 47, characterized in that, The carbon material includes graphite, and the graphite satisfies at least one of the following conditions: The volume average particle size of the graphite is Dv50. 4 The thickness ranges from 5μm to 30μm. The specific surface area of ​​the graphite is 1.2 m². 2 / g-2.2m 2 / g.

49. The battery cell according to any one of claims 1 to 48, characterized in that, The negative electrode sheet satisfies at least one of the following conditions: The density of the negative electrode sheet on one side is 0.12 g / 1540.25 mm. 2 -0.2g / 1540.25mm 2 ; The compaction density of the negative electrode sheet at 0% SOC is 1.2 g / cm³. 3 -1.7g / cm 3 .

50. The battery cell according to any one of claims 1 to 49, characterized in that, The battery cell also includes a separator, the thickness of which is 5μm-12μm.

51. A battery device, characterized in that, include: Multiple battery cells according to any one of claims 1 to 50.

52. An electrical appliance, characterized in that, include: A plurality of battery cells according to any one of claims 1 to 50, or a battery device according to claim 51, wherein the battery cells or battery device are used to store or provide electrical energy.

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