Secondary battery and electronic device comprising same

Abstract

The present application provides a secondary battery and an electronic device comprising same. The secondary battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte solution. The negative electrode sheet comprises a negative electrode material layer, wherein the negative electrode material layer comprises a silicon-containing active material; the silicon-containing active material comprises silicon; and on the basis of the total mass of the negative electrode material layer, the mass percentage content of silicon is C%, and 1≤C≤20. The electrolyte solution comprises: (1) a first component, which is a boron-containing lithium salt, wherein on the basis of the total mass of the electrolyte solution, the mass percentage content of the first component is B%, and 0.1≤B≤5; and (2) a second component, which comprises at least one of a compound represented by formula I or a compound represented by formula II, wherein on the basis of the total mass of the electrolyte solution, the mass percentage content of the second component is A%, and 25≤A≤70. The secondary battery of the present application has good high-temperature and high-voltage cycling stability.

Description

Secondary battery and electronic device comprising same

[0001] This application claims priority to the Chinese patent application No. 202410708509.5, filed on May 31, 2024, and entitled "Secondary battery and electronic device comprising same", the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of electrochemistry, in particular to a secondary battery and an electronic device comprising the same. BACKGROUND

[0003] Electrochemical devices (lithium ion batteries) are widely used in many fields such as 3C electronic products, electric vehicles and energy storage power stations due to their high energy density, high power density, small self-discharge, no memory effect and long cycle life. With the continuous expansion of the use of lithium ion batteries, their use scenarios are more diverse, and the market has higher requirements for the electrochemical performance of lithium ion batteries. SUMMARY

[0004] The purpose of the present application is to provide a secondary battery and an electronic device comprising the same to improve the high-temperature high-voltage cycle stability of the secondary battery. The specific technical solutions are as follows:

[0005] A first aspect of the present application provides a secondary battery, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; the negative electrode sheet comprises a negative electrode material layer, the negative electrode material layer comprises a silicon-containing active material, the silicon-containing active material comprises a silicon element, and the mass percentage content of the silicon element is C% based on the total mass of the negative electrode material layer, 1≤C≤20; the electrolyte comprises: (1) a first component, the first component is a boron-containing lithium salt, comprising at least one of the following compounds: lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium difluoroborate, lithium tetracyanoborate, lithium tetra(trifluoromethyl)borate, lithium dicyano(oxalato)borate, lithium tetramethoxyborate, lithium tetraethoxyborate, lithium perfluoro-t-butoxytrifluoroborate, lithium bis(difluorophosphoryloxy)difluoroborate, lithium pentafluoroethyltrifluoroborate, lithium methoxytricyanoborate and lithium sulfate bis(trifluoroborate); the mass percentage content of the first component is B% based on the total mass of the electrolyte, 0.1≤B≤5; (2) a second component, the second component comprises at least one of a compound of formula I or a compound of formula II:

[0006] wherein, R 11 and R 12 each independently is a fluorine-substituted or unsubstituted C1 to C 10 alkyl, R 11 and R 12at least one of R 21 and R 22 each independently is a fluorine-substituted or unsubstituted C1 to C 10 alkyl, R 21 and R 22 at least one of R is fluorine-substituted; the mass percentage content of the second component is A% based on the total mass of the electrolyte, 25≤A≤70.

[0007] In the secondary battery, the negative electrode material layer includes a silicon-containing active material, the electrolyte includes a first component and a second component, and the values of A, B and C are regulated within the above ranges, which can form good protection for the positive electrode and the negative electrode, and play a synergistic effect of the first component and the second component, so that the secondary battery has good high-temperature high-voltage cycle stability.

[0008] In some embodiments, 0.01≤B / A≤0.12. Regulating the value of B / A within the above range can better play the synergistic effect of the first component and the second component, thereby further improving the high-temperature high-voltage cycle stability of the secondary battery.

[0009] In some embodiments, 0.01≤B / C≤3. Regulating the value of B / C within the above range can further improve the protection effect on the positive electrode and the negative electrode, thereby further improving the high-temperature high-voltage cycle stability of the secondary battery.

[0010] In some embodiments, 1≤C≤15. Regulating the value of C within the above range can further improve the high-temperature high-voltage cycle stability of the secondary battery.

[0011] In some embodiments, 0.5≤B≤3. Regulating the value of B within the above range can further improve the high-temperature high-voltage cycle stability of the secondary battery.

[0012] In some embodiments, 40≤A≤70. Regulating the value of A within the above range can further improve the high-temperature high-voltage cycle stability of the secondary battery.

[0013] In some embodiments, the compound of formula I comprises at least one of the following compounds:

[0014] The electrolyte includes the second component within the above range, which can participate in the formation of a CEI film with better stability, improve the protection effect on the positive electrode, and thereby further improve the high-temperature high-voltage cycle stability of the secondary battery.

[0015] In some embodiments, the compound of formula II comprises at least one of the following compounds:

[0016] The electrolyte includes the second component within the above range, can participate in the formation of a CEI film with better stability, improve the protection of the positive electrode, and thus further improve the high-temperature high-voltage cycle stability of the secondary battery.

[0017] In some embodiments, the electrolyte further includes fluoroethylene carbonate, the mass percentage of the fluoroethylene carbonate is D%, 0.05≤B / D≤1.5 based on the total mass of the electrolyte. The electrolyte includes fluoroethylene carbonate and regulates the value of B / D within the above range, which can improve the protection of the silicon-containing negative electrode interface, while reducing the cycle gas production, thereby improving the high-temperature high-voltage cycle stability of the secondary battery.

[0018] In some embodiments, the electrolyte further includes lithium difluorophosphate, the mass percentage of the lithium difluorophosphate is E%, 0.1≤E≤5 based on the total mass of the electrolyte. The electrolyte includes lithium difluorophosphate and regulates the value of E within the above range, which can inhibit the side reaction between the positive and negative electrodes and the electrolyte, reduce the interface impedance in different charge states and long cycles, while generating a stable interface film on the positive electrode surface, which can effectively inhibit the oxidative decomposition of the electrolyte, thereby improving the high-temperature high-voltage cycle stability of the secondary battery.

[0019] In some embodiments, the electrolyte further includes fluoropyridine, the mass percentage of the fluoropyridine is F%, 0.01≤F≤2 based on the total mass of the electrolyte. The electrolyte includes fluoropyridine and regulates the value of F within the above range, which can further improve the high-temperature high-voltage cycle stability of the secondary battery.

[0020] In some embodiments, the electrolyte further includes a third component, the third component includes adiponitrile, and at least one of vinylene carbonate, vinyl sulfate, 1,3-propane sultone or propylene-1,3-propane sulfonate; the mass percentage of the third component is G%, 0.1≤G≤8 based on the total mass of the electrolyte. The electrolyte includes the third component and regulates the value of G within the above range, which can improve the protection of the positive electrode, enhance the interface protection of the silicon-containing negative electrode, and thus improve the high-temperature high-voltage cycle stability of the secondary battery.

[0021] In some embodiments, the silicon-containing active material includes at least one of silicon-oxygen composite material or silicon-carbon composite material. The negative electrode tab includes the silicon-containing active material of the above type, which is conducive to improving the high-temperature high-voltage cycle stability of the secondary battery.

[0022] The second aspect of the present application provides an electronic device comprising the secondary battery in any of the foregoing embodiments. Thus, the electronic device of the present application has a longer service life.

[0023] The application provides a secondary battery and an electronic device comprising the same. The secondary battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. The negative electrode sheet comprises a negative electrode material layer, and the negative electrode material layer comprises a silicon-containing active material. The silicon-containing active material comprises a silicon element, and the mass percentage of the silicon element is C% based on the total mass of the negative electrode material layer, wherein 1≤C≤20. The electrolyte comprises: (1) a first component, wherein the first component is a boron-containing lithium salt; the mass percentage of the first component is B% based on the total mass of the electrolyte, wherein 0.1≤B≤5; and (2) a second component, wherein the second component comprises at least one of a compound of Formula I or a compound of Formula II; the mass percentage of the second component is A% based on the total mass of the electrolyte, wherein 25≤A≤70. In the secondary battery, the negative electrode material layer comprises the silicon-containing active material, the electrolyte comprises the first component and the second component, and the values of A, B and C are regulated within the above ranges, so that the positive electrode and the negative electrode are well protected, the synergistic effect of the first component and the second component is exerted, and the secondary battery has good high-temperature high-voltage cycle stability.

[0024] Of course, implementing any of the products or methods of the application does not necessarily require all the advantages described above to be achieved simultaneously. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the application, not all the embodiments. All other embodiments obtained by those skilled in the art based on the application belong to the scope of protection of the application.

[0026] It should be noted that in the specific embodiments of the application, the lithium ion battery is taken as an example of the secondary battery to explain the application, but the secondary battery of the application is not limited to the lithium ion battery. The specific technical solutions are as follows:

[0027] The first aspect of this application provides a secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode includes a negative electrode material layer comprising a silicon-containing active material, the silicon-containing active material comprising silicon element, and the mass percentage of silicon element is C% based on the total mass of the negative electrode material layer, 1 ≤ C ≤ 20. For example, the value of C can be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 12, 12.5, 13, 14, 15, 15.5, 16, 17, 18, 19, 20, or a range of any two values ​​therein. The electrolyte comprises a first component and a second component. The first component is a boron-containing lithium salt, which includes at least one of the following compounds: lithium tetrafluoroborate (LiBF4), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluoroborate, lithium tetracyanoborate (LiTCB), lithium tetra(trifluoromethyl)borate, lithium dicyanooxalate borate, lithium tetramethoxyborate, lithium tetraethoxyborate, lithium perfluorotert-butoxytrifluoroborate, lithium di(difluorophosphoroxy)difluoroborate, lithium pentafluoroethyltrifluoroborate, lithium methoxytricyanoborate, and lithium di(trifluoroborate)sulfate. Based on the total mass of the electrolyte, the mass percentage of the first component is B%, 0.1 ≤ B ≤ 5. For example, the value of B can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.8, 1, 1.2, 1.5, 1.7, 1.8, 2, 2.2, 2.5, 2.6, 2.8, 3, 3.2, 3.3, 3.5, 3.8, 4, 4.2, 4.5, 4.6, 4.8, 5, or a range of any two values ​​therein. The second component includes at least one compound of formula I or formula II.

[0028] Among them, R 11 and R 12 Each of the C1 to C1 atoms is independently fluorine-substituted or unsubstituted. 10 Alkyl, R 11 and R 12 At least one of them is fluorinated; R 21 and R 22 Each of the C1 to C1 atoms is independently fluorine-substituted or unsubstituted. 10 Alkyl, R 21 and R 22At least one component is fluorinated; the mass percentage of the second component is A%, based on the total mass of the electrolyte, with 25 ≤ A ≤ 70. For example, the value of A can be 25, 27, 28, 30, 32, 33, 35, 36, 38, 40, 42, 45, 48, 50, 52, 55, 58, 60, 62, 65, 68, 70, or a range of any two values ​​therein. In this application, "high temperature" means a temperature greater than or equal to 45°C, and "high voltage" or "high voltage" means a voltage between the positive and negative electrodes greater than or equal to 4.2V.

[0029] The inventors discovered that when the value of C is too large, for example, greater than 20, the reaction at the negative electrode-electrolyte interface becomes violent, which is detrimental to improving the high-temperature, high-voltage cycle stability of the secondary battery. When the value of B is too small, for example, less than 0.1, it is insufficient to improve the high-temperature, high-voltage cycle stability of the secondary battery; when the value of B is too large, for example, greater than 5, the first component will continuously react and consume lithium ions, resulting in a thicker interfacial film and increased impedance, which is detrimental to improving the high-temperature, high-voltage cycle stability of the secondary battery. When the value of A is too small, for example, less than 25, it is difficult to effectively protect the positive electrode interface, and the lithium ion extraction barrier is high, making it difficult to improve the high-temperature, high-voltage cycle stability of the secondary battery; when the value of A is too large, for example, greater than 70, the lithium ion transport capacity is insufficient, which is detrimental to improving the high-temperature, high-voltage cycle stability of the secondary battery. In the secondary battery of this application, the electrolyte includes a first component and a second component. The first component, a boron-containing lithium salt, can participate in the formation of a solid electrolyte interface (SEI) film with high ion conductivity, low conductivity, and high temperature resistance during the first charge, and participate in the formation of an oxidation-resistant positive electrode electrolyte interface (CEI) film. The second component can improve the high voltage resistance of the electrolyte, reduce the lithium ion extraction or binding barrier during cycling, and reduce the lithium ion insertion / extraction resistance at the interface. At the same time, the negative electrode material layer includes silicon-containing active material, and the values ​​of A, B, and C are controlled within the above range, which can form good protection for the positive and negative electrodes and give full play to the synergistic effect of the first and second components, so that the secondary battery has good high temperature and high voltage cycle stability.

[0030] In one embodiment of this application, the second component comprises a compound of formula I, wherein the mass percentage of the compound of formula I is 25% to 70% based on the total mass of the electrolyte.

[0031] In another embodiment of this application, the second component comprises a compound of formula II, wherein the mass percentage of the compound of formula II is 25% to 70% based on the total mass of the electrolyte.

[0032] In another embodiment of this application, the second component comprises a compound of formula I and a compound of formula II, wherein the sum of the mass percentages of the compounds of formula I and formula II is 25% to 70% based on the total mass of the electrolyte. This application does not impose any particular limitation on the mass ratio of the compounds of formula I and formula II, as long as the purpose of this application can be achieved, for example, the mass ratio of the compounds of formula I and formula II is 1:(0.5 to 1.5).

[0033] In some implementations, 0.01 ≤ B / A ≤ 0.12. For example, the value of B / A can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, or a range of any two of these values. Adjusting the value of B / A within this range allows for better synergy between the first and second components, thereby further improving the high-temperature, high-voltage cycle stability of the secondary battery.

[0034] In some implementations, 0.01 ≤ B / C ≤ 3. For example, the value of B / C can be 0.01, 0.03, 0.05, 0.07, 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.8, 1, 1.2, 1.5, 1.7, 1.8, 2, 2.2, 2.5, 2.6, 2.8, 3, or a range of any two of these values. Adjusting the value of B / C within the above range can further enhance the protection of the positive and negative electrodes and further improve the high-temperature, high-voltage cycle stability of the secondary battery.

[0035] In some implementation schemes, 1 ≤ C ≤ 15. Adjusting the value of C within this range can further improve the high-temperature and high-voltage cycle stability of the secondary battery.

[0036] In some implementation schemes, 0.5 ≤ B ≤ 3. Adjusting the value of B within this range can further improve the high-temperature, high-voltage cycle stability of the secondary battery.

[0037] In some implementations, 40 ≤ A ≤ 70. Adjusting the value of A within this range can further improve the high-temperature, high-voltage cycle stability of the secondary battery.

[0038] In some embodiments, the compound of formula I comprises at least one of the following compounds:

[0039] The electrolyte includes a second component within the aforementioned range, which can participate in the formation of a more stable CEI film, improving the protection of the positive electrode and thus further improving the high-temperature and high-voltage cycle stability of the secondary battery.

[0040] In some embodiments, the compound of formula II comprises at least one of the following compounds:

[0041] The electrolyte includes a second component within the aforementioned range, which can participate in the formation of a more stable CEI film, improving the protection of the positive electrode and thus further improving the high-temperature and high-voltage cycle stability of the secondary battery.

[0042] In some embodiments, the electrolyte also includes fluoroethylene carbonate (FEC), with a mass percentage of FEC of D% based on the total mass of the electrolyte, and a B / D ratio of 0.05 ≤ B ≤ 1.5. For example, the B / D value can be 0.05, 0.07, 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.8, 1, 1.1, 1.2, 1.3, 1.4, 1.5, or a range of any two values ​​therein. Including FEC in the electrolyte and controlling the B / D value within the above range can improve the protection of the silicon-containing anode interface and reduce cycle gas generation, thereby improving the high-temperature, high-voltage cycle stability of the secondary battery.

[0043] In some implementations, 2 ≤ D ≤ 12, for example, the value of D can be 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, or a range of any two of these values. Including FEC in the electrolyte and controlling the value of D within the above range is beneficial for improving the high-temperature, high-voltage cycle stability of the secondary battery.

[0044] In some implementations, the electrolyte also includes lithium difluorophosphate, with the mass percentage of lithium difluorophosphate being E%, 0.1 ≤ E ≤ 5, based on the total mass of the electrolyte. For example, the value of E can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.8, 1, 1.2, 1.5, 1.7, 1.8, 2, 2.2, 2.5, 2.6, 2.8, 3, 3.2, 3.3, 3.5, 3.8, 4, 4.2, 4.5, 4.6, 4.8, 5, or a range of any two of these values. By including lithium difluorophosphate in the electrolyte and controlling the value of E within the above range, lithium difluorophosphate can suppress side reactions between the positive and negative electrodes and the electrolyte, reduce interfacial impedance under different charging states and during long cycles, and simultaneously generate a stable interfacial film on the positive electrode surface, effectively suppressing the oxidative decomposition of the electrolyte, thereby improving the high-temperature and high-voltage cycle stability of the secondary battery.

[0045] In some embodiments, the electrolyte further includes fluoropyridine, with a mass percentage of fluoropyridine of F% based on the total mass of the electrolyte, where 0.01 ≤ F ≤ 2. For example, the value of F can be 0.01, 0.03, 0.05, 0.07, 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.8, 1, 1.2, 1.5, 1.7, 1.8, 2, or a range of any two of these values. By including fluoropyridine in the electrolyte and controlling the value of F within the aforementioned range, fluoropyridine can form an SEI film together with the first and second components. The reduction of fluoropyridine to form a nitrogen-containing polymer helps to construct a "mosaic" type interface film, reducing the continuous degradation of the SEI film during cycling, thereby further improving the high-temperature, high-voltage cycling stability of the secondary battery. In this application, fluoropyridine is selected from at least one of 2-fluoropyridine, 3-fluoropyridine, or 4-fluoropyridine.

[0046] In some embodiments, the electrolyte further includes a third component, which includes adiponitrile and at least one of vinylene carbonate (VC), vinyl sulfate (DTD), 1,3-propanesulfonyl lactone (PS), or propylene-1,3-propanesulfonyl lactone (PES); the mass percentage of the third component is G% based on the total mass of the electrolyte, 0.1 ≤ G ≤ 8, for example, the value of G can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.8, 1, 1.2, 1.5, 1.7, 2, 2.2, 2.5, 2.8, 3, 3.3, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.3, 5.5, 5.7, 6, 6.3, 6.5, 6.8, 7, 7.2, 7.5, 7.8, 8, or a range of any two of these values. The electrolyte includes a third component and the value of G is adjusted within the above range. The nitrile group of adiponitrile can complex with metal ions, inhibit the dissolution of metal ions, and improve the protection capability of the positive electrode. At the same time, at least one of VC, DTD, PS or PES can participate in the formation of a reduction-resistant SEI film during the initial formation process, enhance the interface protection of the silicon-containing negative electrode, and thus improve the high-temperature and high-voltage cycle stability of the secondary battery.

[0047] In some embodiments, based on the total mass of the electrolyte, the mass percentage of adiponitrile is G1%, and the total mass percentage of vinylene carbonate, vinyl sulfate, 1,3-propanesulfonyl lactone, and propenyl-1,3-propanesulfonyl lactone is G2%. This application does not impose any particular limitation on the value of G1:G2, as long as it achieves the purpose of this application; exemplaryly, G1:G2 is 1:(0.5 to 1.5).

[0048] In this application, fluoroethylene carbonate, lithium difluorophosphate, fluoropyridine, and the third component within the above-mentioned scope can be used in any combination, as long as the purpose of this application can be achieved.

[0049] In some embodiments, the silicon-containing active material includes at least one of silicon-oxygen composite materials or silicon-carbon composite materials. Exemplarily, the silicon-oxygen composite material is such as SiOx, where 0 < x ≤ 2; the silicon-carbon composite material is such as SiC, and silicon-oxygen composite materials or silicon-carbon composite materials known in the art or commercially available can be used; for example, in commercially available silicon-carbon composite materials, the silicon element typically accounts for 40% to 60% of the mass percentage of the silicon-carbon composite material. Without being limited to any theory, including the above-mentioned types of silicon-containing active materials in the negative electrode sheet can simplify the processing of the negative electrode slurry and negative electrode sheet, while simultaneously improving the energy density of the secondary battery and contributing to improved high-temperature, high-voltage cycle stability of the secondary battery.

[0050] In this application, the electrolyte also includes an electrolyte salt and a non-aqueous solvent. This application does not impose any particular limitation on the electrolyte salt, as long as it achieves the purpose of this application. For example, the electrolyte salt may include, but is not limited to, at least one of LiPF6, LiAsF6, LiClO4, LiCH3SO3, LiCF3SO3, LiC(SO2CF3)3, or Li2SiF6. This application does not impose any particular limitation on the content of the electrolyte salt in the electrolyte, as long as it achieves the purpose of this application. For example, based on the mass of the electrolyte, the mass percentage content of the electrolyte salt is 8% to 15%.

[0051] This application does not impose any particular limitation on non-aqueous solvents, as long as they can achieve the purpose of this application. For example, non-aqueous solvents may include, but are not limited to, at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents. The aforementioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds or cyclic carbonate compounds. The aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (MEC). The aforementioned cyclic carbonates may include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), or vinyl ethylene carbonate (VEC). The aforementioned carboxylic acid ester compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valproic acid lactone, or caprolactone. The aforementioned ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. Other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. This application does not impose any particular limitation on the content of non-aqueous solvents in the electrolyte, as long as the purpose of this application is achieved. For example, based on the total mass of the electrolyte, the mass percentage of non-aqueous solvents may be 0% to 66%.

[0052] In one embodiment of this application, the electrolyte includes a first component, a second component, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the first component, the second component, and the electrolyte salt, based on the total mass of the electrolyte, are as described above, and the mass percentage of the non-aqueous solvent is 10% to 66%. The electrolyte includes the first component and the second component. Secondary batteries using the electrolyte of this application exhibit improved high-temperature and high-voltage cycle stability.

[0053] In one embodiment of this application, the electrolyte comprises a first component, a second component, fluoroethylene carbonate, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the first component, the second component, the fluoroethylene carbonate, and the electrolyte salt, based on the total mass of the electrolyte, are as described above, and the mass percentage of the non-aqueous solvent is 0% to 64%. The electrolyte, comprising the first component, the second component, and the fluoroethylene carbonate, further improves the high-temperature, high-voltage cycle stability of secondary batteries using the electrolyte of this application.

[0054] In one embodiment of this application, the electrolyte comprises a first component, a second component, lithium difluorophosphate, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the first component, second component, lithium difluorophosphate, and electrolyte salt, based on the total mass of the electrolyte, are as described above, and the mass percentage of the non-aqueous solvent is 5% to 66%. The electrolyte comprises the first component, the second component, and lithium difluorophosphate. Secondary batteries using the electrolyte of this application exhibit further improved high-temperature and high-voltage cycle stability.

[0055] In one embodiment of this application, the electrolyte comprises a first component, a second component, fluoropyridine, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the first component, second component, fluoropyridine, and electrolyte salt, based on the total mass of the electrolyte, are as described above, and the mass percentage of the non-aqueous solvent is 8% to 66%. With the electrolyte comprising the first component, second component, and fluoropyridine, the secondary battery using the electrolyte of this application exhibits further improved high-temperature and high-voltage cycle stability.

[0056] In one embodiment of this application, the electrolyte comprises a first component, a second component, a third component, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the first component, second component, third component, and electrolyte salt, based on the total mass of the electrolyte, are as described above, and the mass percentage of the non-aqueous solvent is 2% to 66%. The electrolyte comprises the first component, second component, and third component. Secondary batteries using the electrolyte of this application exhibit further improved high-temperature and high-voltage cycle stability.

[0057] In one embodiment of this application, the electrolyte comprises a first component, a second component, fluoroethylene carbonate, lithium difluorophosphate, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the first component, second component, fluoroethylene carbonate, lithium difluorophosphate, and electrolyte salt, based on the total mass of the electrolyte, are as described above, and the mass percentage of the non-aqueous solvent is 0% to 64%. The electrolyte comprises the first component, second component, fluoroethylene carbonate, and lithium difluorophosphate. Secondary batteries using the electrolyte of this application exhibit further improved high-temperature and high-voltage cycle stability.

[0058] In one embodiment of this application, the electrolyte comprises a first component, a second component, fluoroethylene carbonate, fluoropyridine, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the first component, second component, fluoroethylene carbonate, fluoropyridine, and electrolyte salt, based on the total mass of the electrolyte, are as described above, and the mass percentage of the non-aqueous solvent is 0% to 64%. The secondary battery using the electrolyte comprising the first component, second component, fluoroethylene carbonate, and fluoropyridine exhibits further improved high-temperature and high-voltage cycle stability.

[0059] In one embodiment of this application, the electrolyte comprises a first component, a second component, fluoroethylene carbonate, a third component, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the first component, second component, fluoroethylene carbonate, third component, and electrolyte salt, based on the total mass of the electrolyte, are as described above, and the mass percentage of the non-aqueous solvent is 0% to 64%. The electrolyte comprises the first component, second component, fluoroethylene carbonate, and third component. Secondary batteries using the electrolyte of this application exhibit further improved high-temperature and high-voltage cycle stability.

[0060] In one embodiment of this application, the electrolyte comprises a first component, a second component, lithium difluorophosphate, fluoropyridine, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the first component, second component, lithium difluorophosphate, fluoropyridine, and electrolyte salt, based on the total mass of the electrolyte, are as described above, and the mass percentage of the non-aqueous solvent is 3% to 66%. The electrolyte, comprising the first component, second component, lithium difluorophosphate, and fluoropyridine, further improves the high-temperature, high-voltage cycle stability of secondary batteries using the electrolyte of this application.

[0061] In one embodiment of this application, the electrolyte comprises a first component, a second component, lithium difluorophosphate, a third component, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the first component, second component, lithium difluorophosphate, third component, and electrolyte salt, based on the total mass of the electrolyte, are as described above, and the mass percentage of the non-aqueous solvent is 0% to 66%. The electrolyte comprises the first component, second component, lithium difluorophosphate, and third component. Secondary batteries using the electrolyte of this application exhibit further improved high-temperature and high-voltage cycle stability.

[0062] In one embodiment of this application, the electrolyte comprises a first component, a second component, fluoropyridine, a third component, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the first component, second component, fluoropyridine, third component, and electrolyte salt, based on the total mass of the electrolyte, are as described above, and the mass percentage of the non-aqueous solvent is 0% to 66%. The electrolyte comprises the first component, second component, fluoropyridine, and third component. Secondary batteries using the electrolyte of this application exhibit further improved high-temperature and high-voltage cycle stability.

[0063] In one embodiment of this application, the electrolyte comprises a first component, a second component, fluoroethylene carbonate, lithium difluorophosphate, fluoropyridine, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the first component, second component, fluoroethylene carbonate, lithium difluorophosphate, fluoropyridine, and electrolyte salt, based on the total mass of the electrolyte, are as described above, and the mass percentage of the non-aqueous solvent is 0% to 64%. The secondary battery using the electrolyte comprising the first component, second component, fluoroethylene carbonate, lithium difluorophosphate, and fluoropyridine exhibits further improved high-temperature and high-voltage cycle stability.

[0064] In one embodiment of this application, the electrolyte comprises a first component, a second component, fluoroethylene carbonate, lithium difluorophosphate, a third component, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the first component, second component, fluoroethylene carbonate, lithium difluorophosphate, third component, and electrolyte salt, based on the total mass of the electrolyte, are as described above, and the mass percentage of the non-aqueous solvent is 0% to 64%. The electrolyte comprises the first component, second component, fluoroethylene carbonate, lithium difluorophosphate, and third component. Secondary batteries using the electrolyte of this application exhibit further improved high-temperature and high-voltage cycle stability.

[0065] In one embodiment of this application, the electrolyte comprises a first component, a second component, fluoroethylene carbonate, fluoropyridine, a third component, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the first component, second component, fluoroethylene carbonate, fluoropyridine, third component, and electrolyte salt, based on the total mass of the electrolyte, are as described above, and the mass percentage of the non-aqueous solvent is 0% to 64%. The secondary battery using the electrolyte of this application exhibits further improved high-temperature and high-voltage cycle stability, comprising the first component, second component, fluoroethylene carbonate, fluoropyridine, and third component.

[0066] In one embodiment of this application, the electrolyte comprises a first component, a second component, lithium difluorophosphate, fluoropyridine, a third component, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the first component, second component, lithium difluorophosphate, fluoropyridine, third component, and electrolyte salt, based on the total mass of the electrolyte, are as described above, and the mass percentage of the non-aqueous solvent is 0% to 66%. The secondary battery using the electrolyte of this application exhibits further improved high-temperature and high-voltage cycle stability, comprising the first component, second component, lithium difluorophosphate, fluoropyridine, and third component.

[0067] In one embodiment of this application, the electrolyte comprises a first component, a second component, fluoroethylene carbonate, lithium difluorophosphate, fluoropyridine, a third component, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the first component, second component, fluoroethylene carbonate, lithium difluorophosphate, fluoropyridine, third component, and electrolyte salt, based on the total mass of the electrolyte, are as described above, and the mass percentage of the non-aqueous solvent is 0% to 64%. The secondary battery using the electrolyte comprising the first component, second component, fluoroethylene carbonate, lithium difluorophosphate, fluoropyridine, and third component exhibits further improved high-temperature and high-voltage cycle stability.

[0068] In this application, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The phrase "the negative electrode material layer is disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its thickness direction, or on two surfaces of the negative electrode current collector along its thickness direction. It should be noted that the term "surface" here can refer to the entire surface area of ​​the negative electrode current collector, or only a portion thereof; this application does not impose any particular limitation, as long as the purpose of this application is achieved.

[0069] This application does not impose any particular restrictions on the negative electrode current collector, as long as it can achieve the purpose of this application. For example, it may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or composite current collector. For example, the composite current collector may be lithium copper composite current collector, carbon copper composite current collector, nickel copper composite current collector, titanium copper composite current collector, etc.

[0070] The negative electrode material layer may also include other negative electrode active materials. This application does not impose any particular restrictions on other negative electrode active materials, as long as they can achieve the purpose of this application. For example, other negative electrode active materials may include, but are not limited to, natural graphite, artificial graphite, mesophase micro carbon spheres, hard carbon, soft carbon, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 Or at least one of Li-Al alloys.

[0071] In this application, the mass percentage of silicon in the anode material layer can also be controlled by adjusting the mass ratio of silicon-containing active material to other anode active materials.

[0072] In some embodiments of this application, the negative electrode material layer may further include a conductive agent and a binder. This application does not particularly limit the types of conductive agents and binders, as long as they achieve the purpose of this application. For example, the conductive agent may include, but is not limited to, at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metallic materials, or conductive polymers. The conductive carbon black may include, but is not limited to, at least one of acetylene black or Ketjen black. The aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The aforementioned carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers. The aforementioned metallic materials may include, but are not limited to, metal powders and / or metal fibers; specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The aforementioned conductive polymers may include, but are not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. For example, the binder may include, but is not limited to, at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamide-imide, styrene-butadiene rubber, or polyvinylidene fluoride. This application does not impose any particular limitation on the mass ratio of the negative electrode active material, conductive agent, and binder in the negative electrode material layer; those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved. The negative electrode material layer may also include a thickener. This application does not impose any particular limitation on the content and type of thickener; conventional types and contents known in the art can be used, as long as the purpose of this application is achieved.

[0073] This application does not impose any particular limitation on the thickness of the negative electrode material layer, as long as it achieves the purpose of this application. For example, the thickness of the negative electrode material layer can be from 30 μm to 120 μm. This application also does not impose any particular limitation on the thickness of the negative electrode current collector, as long as it achieves the purpose of this application. For example, the thickness of the negative electrode current collector can be from 4 μm to 15 μm.

[0074] Optionally, the negative electrode sheet may further include a conductive layer located between the negative electrode current collector and the negative electrode material layer. This application does not impose any particular limitation on the composition of the conductive layer, which can be a conductive layer commonly used in the art. For example, the conductive layer may include a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer; for example, it can be at least one of the aforementioned conductive agents and binders.

[0075] In this application, the positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The phrase "positive electrode material layer disposed on at least one surface of the positive current collector" means that the positive electrode material layer can be disposed on one surface of the positive current collector along its thickness direction, or on two surfaces of the positive current collector along its thickness direction. It should be noted that "surface" here can refer to the entire surface area of ​​the positive current collector, or only a portion thereof; this application does not impose any particular limitation, as long as the purpose of this application is achieved.

[0076] This application does not impose any particular restrictions on the positive electrode current collector, as long as it can achieve the purpose of this application. For example, it may include aluminum foil, aluminum alloy foil, or composite current collector (such as aluminum-carbon composite current collector).

[0077] The positive electrode material layer includes a positive electrode active material. This application does not impose any particular limitation on the positive electrode active material, as long as it can achieve the purpose of this application. For example, the positive electrode active material may include, but is not limited to, lithium nickel cobalt manganese oxide (e.g., NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium manganese iron phosphate, or lithium titanate.

[0078] The positive electrode material layer may also include a conductive agent and a binder. This application does not impose any particular restrictions on the types of conductive agents and binders, as long as they achieve the purpose of this application. For example, it may include at least one of the aforementioned conductive agents and binders. This application does not impose any particular restrictions on the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0079] This application does not impose any particular limitations on the thickness of the positive electrode current collector and the positive electrode material layer, as long as the purpose of this application can be achieved. For example, the thickness of the positive electrode current collector can be 5 μm to 20 μm, and the thickness of the positive electrode material layer can be 30 μm to 120 μm.

[0080] Optionally, the positive electrode may further include a conductive layer located between the positive current collector and the positive electrode material layer. The composition of the conductive layer is not particularly limited and can be any conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer; for example, it can be at least one of the aforementioned conductive agents and binders.

[0081] In this application, the secondary battery also includes a separator. This application does not impose any particular limitation on the separator, as long as it achieves the purpose of this application. For example, the material of the separator may include, but is not limited to, at least one of polyethylene (PE), polyolefins (PO) primarily composed of polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The type of separator may include at least one of woven membrane, nonwoven membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane.

[0082] In some embodiments of this application, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used.

[0083] Optionally, a surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic substances.

[0084] In some embodiments of this application, the inorganic layer comprises inorganic particles and a binder. This application does not particularly limit the inorganic particles; for example, the inorganic particles may include at least one selected from alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. This application does not particularly limit the binder; for example, the binder may be at least one of the binders described above. In some embodiments of this application, the polymer layer comprises a polymer, the polymer material of which includes at least one selected from polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, or polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0085] In this application, there is no particular limitation on the thickness of the separator, as long as it can achieve the purpose of this application. For example, the thickness of the separator can be from 3 μm to 30 μm.

[0086] In this application, the secondary battery also includes a casing for housing the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the field of secondary batteries. This application does not limit the scope of these other components. This application does not impose any particular limitation on the casing; it can be a casing known in the art, as long as it achieves the purpose of this application. For example, the casing can be a rigid casing or a flexible casing. The material of the rigid casing can be metal; this application does not limit the type of metal and can use known metal rigid casings, as long as they achieve the purpose of this application. The flexible casing can be a metal plastic film, such as aluminum-plastic film, steel-plastic film, etc.

[0087] The fabrication process of the secondary battery described in this application is well known to those skilled in the art, and this application does not impose any particular limitations. For example, the fabrication process of the secondary battery may include, but is not limited to, the following steps: stacking the positive electrode sheet, separator, and negative electrode sheet in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the secondary battery. Alternatively, stacking the positive electrode sheet, separator, and negative electrode sheet in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the secondary battery. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the housing as needed to prevent pressure rise and overcharging / discharging inside the secondary battery.

[0088] This application does not impose any particular limitation on the type of secondary battery, which may include any device in which an electrochemical reaction occurs. For example, secondary batteries may include, but are not limited to: lithium metal secondary batteries, lithium-ion batteries, sodium-ion batteries, lithium polymer secondary batteries, and lithium-ion polymer secondary batteries.

[0089] A second aspect of this application provides an electronic device comprising a secondary battery as described in any of the foregoing embodiments. The secondary battery provided by this application exhibits high-temperature and high-voltage cycle stability, thereby giving the electronic device a longer service life.

[0090] This application does not specifically limit the type of electronic device; it can be any electronic device known in the prior art. In some embodiments of this application, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0091] Example

[0092] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0093] Test methods and equipment:

[0094] Test for silicon elemental mass percentage:

[0095] A lithium-ion battery discharged at 0.5C to 3.0V was disassembled, and the negative electrode sheet was removed. It was then soaked in dimethyl carbonate (DMC) for 20 minutes, followed by rinsing with DMC and acetone respectively. The negative electrode sheet was then placed in an oven and baked at 80°C for 12 hours. The negative electrode sheet was then dried in a vacuum oven at 100°C for 24 hours. The negative electrode material layer was scraped off with a blade, and the mass percentage of silicon in the negative electrode material layer was measured using an ICP (Inductively Coupled Plasma) analyzer.

[0096] High temperature and high voltage cycling performance test:

[0097] Place the lithium-ion battery in a 45℃ constant temperature test chamber and let it stand for 30 minutes to allow it to reach a constant temperature. Charge it at a constant current of 0.5C to 4.45V, then charge it at a constant voltage to a current of 0.025C. Let it stand for 5 minutes, then discharge it at a constant current of 0.5C to 3.0V. Record this as the initial discharge capacity C1. Repeat this charge-discharge cycle and record the discharge capacity C2 after each cycle. Calculate the cycle capacity retention rate of the lithium-ion battery: Cycle capacity retention rate = C2 / C1 × 100%. Stop the test when the cycle capacity retention rate is ≤80%, and record the number of cycles at this point.

[0098] Example 1-1

[0099] <Preparation of Negative Electrode Sheets>

[0100] A Si / C composite material (commercially available, silicon nanopore-loaded Si, with a silicon element mass percentage of 50% in the silicon-carbon composite material), artificial graphite, lithium polyacrylate (PAA-Li) binder, and carbon nanotubes conductive agent were mixed in a mass ratio of 2:88:7:3. Deionized water was added, and the mixture was stirred evenly under vacuum to obtain a negative electrode slurry with a solid content of 30 wt%. The negative electrode slurry was uniformly coated on one side of a 12 μm thick copper foil for the negative electrode current collector and dried at 120 °C to obtain a negative electrode sheet with a single-sided coating material layer of 143 μm. The above steps were repeated on the other side of the copper foil to obtain a negative electrode sheet with a double-sided coating material layer. After cold pressing and slitting, a negative electrode sheet with a size of 78 mm × 875 mm was obtained. The thickness of the single-sided negative electrode material layer after cold pressing was 80 μm. Based on the total mass of the negative electrode material layer, the mass percentage of Si element (C%) was 1%.

[0101] <Preparation of the positive electrode>

[0102] Lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) binder were mixed in a mass ratio of 97:1.4:1.6. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75%. The mixture was stirred under vacuum until a homogeneous positive electrode slurry was formed. The positive electrode slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil current collector and dried at 85°C to obtain a single-sided positive electrode sheet with a 90 μm thick positive electrode material layer. The above steps were then repeated on the other surface of the positive electrode sheet to obtain a double-sided positive electrode sheet. After coating, the positive electrode sheet was cold-pressed and cut into 74 mm × 867 mm dimensions for later use. The compaction density of the positive electrode sheet was 4 g / cm³. 3 .

[0103] <Preparation of Electrolyte>

[0104] In an argon-atmospheric glove box with a water content of less than 10 ppm, ethyl methyl carbonate was used as a non-aqueous solvent. Then, lithium difluoroborate (component 1), I-3 (component 2), and the electrolyte salt LiPF6 were added to the non-aqueous solvent and mixed thoroughly to obtain the electrolyte. Based on the total mass of the electrolyte, the mass percentage of component 1 (B%) was 3%, the mass percentage of component 2 (A%) was 40%, the mass percentage of the electrolyte salt was 12.5%, and the remainder was the non-aqueous solvent.

[0105] <Isolation membrane>

[0106] A 5μm thick polyethylene (PE) porous membrane (provided by Shanghai Enjie Co., Ltd.) was used.

[0107] <Preparation of Lithium-ion Batteries>

[0108] The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode assembly is then wound to obtain the electrode assembly. After welding the tabs, the electrode assembly is placed in an aluminum-plastic film packaging shell and dried in an 85°C vacuum oven for 12 hours to remove moisture. The prepared electrolyte is then injected, and the lithium-ion battery is obtained through vacuum sealing, settling, formation (0.02C constant current charging to 3.5V, then 0.1C constant current charging to 3.9V), shaping, and capacity testing.

[0109] Examples 1-2 to 1-23

[0110] Except for adjusting the mass ratio of silicon-containing active material and artificial graphite in the <Preparation of Negative Electrode Sheet>, while keeping the total mass of silicon-containing active material and artificial graphite constant, so that the mass percentage of silicon element C% in the negative electrode material layer is as shown in Table 1, and adjusting the type and mass percentage of the first component B% and the type and mass percentage of the second component A according to Table 1 in the <Preparation of Electrolyte>, the mass percentage of non-aqueous solvent changes accordingly, and the mass percentage of electrolyte salt remains unchanged, the rest is the same as in Example 1-1.

[0111] Examples 1-24

[0112] Except for the fact that in the <Preparation of Negative Electrode Sheet>, the type of silicon-containing active material was adjusted to a silicon-oxygen composite material (commercially available) so that the type of silicon-containing active material is as shown in Table 1, the rest is the same as in Examples 1-3.

[0113] Examples 2-1 to 2-3

[0114] Except for the addition of fluoroethylene carbonate as shown in Table 2 in the <Preparation of Electrolyte>, the adjustment of the mass percentage D of fluoroethylene carbonate according to Table 2, the change of the mass percentage of non-aqueous solvent, and the unchanged mass percentage of the first component, the second component, and the electrolyte salt, the rest are the same as in Examples 1-10.

[0115] Examples 2-4 to 2-30

[0116] Except for the addition of fluoroethylene carbonate, lithium difluorophosphate, fluoropyridine:2-fluoropyridine, and the third component as shown in Table 2 in the <Preparation of Electrolyte>, and the adjustment of the mass percentages of fluoroethylene carbonate (D%), lithium difluorophosphate (E%), fluoropyridine (F%), the type and mass percentage of the third component (G%) according to Table 2, and the change of the mass percentage of non-aqueous solvents, while keeping the mass percentages of the first component, the second component, and the electrolyte salt unchanged, the rest is the same as in Examples 1-3.

[0117] Comparative Examples 1-1 to 1-10

[0118] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Example 1-1. When silicon is not present, the silicon-containing active material of the negative electrode is replaced with artificial graphite. When the mass percentage of the first component B% and / or the mass percentage of the second component A% changes, the mass percentage of the non-aqueous solvent changes accordingly, while the mass percentage of the electrolyte salt remains unchanged. The mass percentage C% of silicon in the negative electrode material layer is adjusted by changing the mass ratio of the silicon-containing active material and artificial graphite in the <Preparation of the Negative Electrode Sheet>, while keeping the total mass of the silicon-containing active material and artificial graphite constant, as shown in Table 1.

[0119] As can be seen from Examples 1-1 to 1-24 and Comparative Examples 1-1 to 1-10, when the negative electrode sheet includes a silicon-containing active material and the content of silicon element C in the negative electrode material layer is controlled within the range of this application, and the electrolyte includes a first component and a second component and the values ​​of B and A are controlled within the range of this application, the lithium-ion battery has a high number of high-temperature and high-voltage cycle cycles, indicating that the lithium-ion battery has good high-temperature and high-voltage cycle stability.

[0120] The B / A ratio typically affects the high-temperature, high-voltage cycle stability of lithium-ion batteries. As can be seen from Examples 1-3, 1-6 to 1-15, when the B / A ratio is adjusted within the range specified in this application, the lithium-ion battery exhibits a higher number of high-temperature, high-voltage cycle cycles, indicating that the lithium-ion battery possesses good high-temperature, high-voltage cycle stability.

[0121] The B / C ratio typically affects the high-temperature, high-voltage cycle stability of lithium-ion batteries. As can be seen from Examples 1-1 to 1-5 and Examples 1-16 to 1-18, when the B / C ratio is adjusted within the range specified in this application, the lithium-ion battery exhibits a higher number of high-temperature, high-voltage cycle cycles, indicating that the lithium-ion battery possesses good high-temperature, high-voltage cycle stability.

[0122] The type of the first component, the second component, and the silicon-containing active material typically affects the high-temperature, high-voltage cycle stability of lithium-ion batteries. As can be seen from Examples 1-3, 1-19 to 1-24, lithium-ion batteries using the selected first component, second component, and silicon-containing active material within the scope of this application exhibit higher high-temperature, high-voltage cycle counts, indicating that the lithium-ion batteries possess better high-temperature, high-voltage cycle stability.

[0123] The B / D ratio typically affects the high-temperature, high-voltage cycle stability of lithium-ion batteries. As can be seen from Examples 1-3, 1-10, and 2-1 to 2-7, when the B / D ratio is adjusted within the range specified in this application, the lithium-ion battery exhibits a higher number of high-temperature, high-voltage cycle cycles, indicating better high-temperature, high-voltage cycle stability.

[0124] The content of lithium difluorophosphate and fluoropyridine typically affects the high-temperature, high-voltage cycle stability of lithium-ion batteries. As can be seen from Examples 2-8 to 2-18, when the electrolyte includes lithium difluorophosphate or fluoropyridine within the content range of this application, the lithium-ion battery can achieve a higher number of high-temperature, high-voltage cycles, indicating better high-temperature, high-voltage cycle stability.

[0125] The type and content of the third component typically affect the high-temperature and high-voltage cycle stability of lithium-ion batteries. As can be seen from Examples 1-3, 2-19 to 2-24, when the electrolyte includes the third component within the range of types and contents specified in this application, the lithium-ion battery exhibits a higher number of high-temperature and high-voltage cycle cycles, indicating better high-temperature and high-voltage cycle stability.

[0126] Different types of electrolytes typically affect the high-temperature, high-voltage cycle stability of lithium-ion batteries. As can be seen from Examples 1-3 and Examples 2-1 to 2-30, when the electrolyte of this application, consisting of fluoroethylene carbonate, lithium difluorophosphate, fluoropyridine, and the third component, is used in combination, the number of high-temperature, high-voltage cycles of the lithium-ion battery can be further increased, indicating that the high-temperature, high-voltage cycle stability of the lithium-ion battery is further improved.

[0127] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0128] The element connected by the terms "one of," "among," "a kind of," or other similar terms refers to any one of the listed elements. For example, "one of A or B" means only A or only B; similarly, "one of A, B, and C" means only A, only B, or only C. The element connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms refers to any combination of the listed elements. For example, "at least one of A or B" means only A, only B, A and B; similarly, "at least one of A, B, or C" means only A, only B, only C, only A and B, only A and C, only B and C, A and B and C.

[0129] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0130] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A secondary battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte; wherein the negative electrode comprises a negative electrode material layer, the negative electrode material layer comprises a silicon-containing active material, the silicon-containing active material comprises silicon element, and based on the total mass of the negative electrode material layer, the mass percentage of silicon element is C%, 1≤C≤20; the electrolyte comprises: (1) A first component, wherein the first component is a boron-containing lithium salt, the boron-containing lithium salt comprising at least one of the following compounds: lithium tetrafluoroborate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluoroborate, lithium tetracyanoborate, lithium tetra(trifluoromethyl)borate, lithium dicyanooxalate borate, lithium tetramethoxyborate, lithium tetraethoxyborate, lithium perfluorotert-butoxytrifluoroborate, lithium di(difluorophosphoroxy)difluoroborate, lithium pentafluoroethyltrifluoroborate, lithium methoxytricyanoborate, and lithium di(trifluoroborate)sulfate; Based on the total mass of the electrolyte, the mass percentage of the first component is B%, 0.1≤B≤5; (2) A second component, the second component comprising at least one of a compound of formula I or a compound of formula II: Among them, R 11 and R 12 Each of the C1 to C1 atoms is independently fluorine-substituted or unsubstituted. 10 Alkyl, R 11 and R 12 At least one of them is fluorinated; R 21 and R 22 Each of the C1 to C1 atoms is independently fluorine-substituted or unsubstituted. 10 Alkyl, R 21 and R 22 At least one of them is fluorinated; Based on the total mass of the electrolyte, the mass percentage of the second component is A%, and 25 ≤ A ≤ 70%.

2. The secondary battery according to claim 1, wherein, 0.01≤B / A≤0.

12.

3. The secondary battery according to claim 1, wherein, 0.01≤B / C≤3.

4. The secondary battery according to claim 1, wherein, The secondary battery must satisfy at least one of the following characteristics: a) 1 ≤ C ≤ 15; b) 0.5 ≤ B ≤ 3; c) 40≤A≤70.

5. The secondary battery according to claim 1, wherein, The compound of formula I comprises at least one of the following compounds:

6. The secondary battery according to claim 1, wherein, The compound of formula II comprises at least one of the following compounds:

7. The secondary battery according to any one of claims 1 to 6, wherein, The electrolyte also includes fluoroethylene carbonate, and the mass percentage of fluoroethylene carbonate is D% based on the total mass of the electrolyte, with a content of 0.05 ≤ B / D ≤ 1.

5.

8. The secondary battery according to any one of claims 1 to 6, wherein, The electrolyte also includes lithium difluorophosphate, and the mass percentage of lithium difluorophosphate is E% based on the total mass of the electrolyte, 0.1≤E≤5.

9. The secondary battery according to any one of claims 1 to 6, wherein, The electrolyte also includes fluoropyridine, and the mass percentage of fluoropyridine is F% based on the total mass of the electrolyte, with a mass percentage of 0.01 ≤ F ≤ 2.

10. The secondary battery according to any one of claims 1 to 6, wherein, The electrolyte further includes a third component, which includes adiponitrile and at least one of vinylene carbonate, vinyl sulfate, 1,3-propanesulfonyl lactone or propenyl-1,3-propanesulfonyl lactone; the mass percentage of the third component is G% based on the total mass of the electrolyte, and 0.1 ≤ G ≤ 8%.

11. The secondary battery according to any one of claims 1 to 6, wherein, The silicon-containing active material includes at least one of silicon-oxygen composite materials or silicon-carbon composite materials.

12. An electronic device comprising a secondary battery according to any one of claims 1 to 11.

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