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. The negative electrode sheet comprises a negative electrode material layer; the negative electrode material layer comprises a silicon-containing active substance; the silicon-containing active substance comprises a silicon element; and on the basis of the total mass of the negative electrode material layer, the mass percentage of the silicon element is A%, wherein 1≤A≤20. The electrolyte comprises: a first component, the first component comprising at least one of a compound of formula I and a compound of formula II; and a second component. On the basis of the total mass of the electrolyte, the mass percentage of the first component is B%, and the mass percentage of the second component is C%, wherein 25≤B≤70, and 0.07≤C / B≤1. The secondary battery in the present application has good cycle stability and low-temperature discharging performance.

Description

Secondary battery and electronic device comprising same

[0001] The present application claims priority to the Chinese patent application No. 202410703741.X, filed on May 31, 2024, and entitled "Secondary battery and electronic device comprising same", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of electrochemistry, and 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 range 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, so as to improve the cycle stability and low-temperature discharge performance of the secondary battery. The specific technical solutions are as follows:

[0005] The 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, the mass percentage content of the silicon element is A% based on the total mass of the negative electrode material layer, and 1≤A≤20; the electrolyte comprises: (1) a first component, the first component comprises at least one of a compound of formula I or a compound of formula II:

[0006] wherein, R 11 and R 12 are each independently a fluorine-substituted or unsubstituted C1 to C10 alkyl, R 11 and R 12 are each independently a fluorine-substituted or unsubstituted C1 to C10 alkyl, R 21 and R 22 are each independently a fluorine-substituted or unsubstituted C1 to C10 alkyl, R 21 and R 22At least one of the components is fluorinated; and (2) a second component, the second component comprising at least one of the following compounds: ethyl formate, methyl acetate, ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), dimethyl carbonate (DMC), or diethyl carbonate (DEC); based on the total mass of the electrolyte, the mass percentage of the first component is B%, and the mass percentage of the second component is C%, wherein 25≤B≤70, 0.07≤C / B≤1. In the secondary battery of this application, 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 / B are adjusted within the above ranges to form good protection for the positive and negative electrodes, so that the secondary battery has good cycle stability. At the same time, the first component has a low binding energy with lithium ions, and the second component can reduce the viscosity of the electrolyte and reduce the lithium ion transport resistance, thereby giving the secondary battery good low-temperature discharge performance.

[0007] In one embodiment of this application, 3 ≤ A ≤ 15. Adjusting the value of A within the above range can further improve the cycle stability and low-temperature discharge performance of the secondary battery.

[0008] In one embodiment of this application, 30 ≤ B ≤ 60. Adjusting the value of B within the above range can further improve the cycle stability and low-temperature discharge performance of the secondary battery.

[0009] In one embodiment of this application, 0.1 ≤ C / B ≤ 0.9. Adjusting the value of C / B within the above range can further improve the cycle stability and low-temperature discharge performance of the secondary battery.

[0010] In one embodiment of this application, 0.01 ≤ A / (B+C) ≤ 0.5. For example, the value of A / (B+C) can be 0.01, 0.02, 0.03, 0.05, 0.07, 0.08, 0.1, 0.12, 0.13, 0.15, 0.16, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, 0.45, 0.5, or a range consisting of any two of these values. Adjusting the value of A / (B+C) within the above range can further improve the protection of the positive and negative electrodes, while further reducing the electrolyte viscosity and lithium-ion transport resistance, thereby further improving the cycle stability and low-temperature discharge performance of the secondary battery.

[0011] In one embodiment of this application, the compound of formula I comprises at least one of the following compounds:

[0012] The electrolyte includes the first component within the above range, can participate in the formation of a positive electrode electrolyte interface (CEI) film with better stability, improve the protection of the positive electrode, and further improve the cycle stability and low-temperature discharge performance of the secondary battery.

[0013] In an embodiment of the present application, the compound of formula II includes at least one of the following compounds:

[0014] The electrolyte includes the first 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 further improve the cycle stability and low-temperature discharge performance of the secondary battery.

[0015] In an embodiment of the present application, the electrolyte further includes fluoroethylene carbonate (FEC), and the mass percentage of the fluoroethylene carbonate in the total mass of the electrolyte is D%, 2≤D≤12. The electrolyte includes FEC and regulates the value of D within the above range, which can improve the protection of the negative electrode sheet, while reducing the cycle gas production, thereby improving the cycle stability and low-temperature discharge performance of the secondary battery.

[0016] In an embodiment of the present application, the electrolyte further includes a third component, and the third component includes at least one of the following compounds: butanedinitrile, pentanedinitrile, methylpentanedinitrile, hexanedinitrile, heptanedinitrile, octanedinitrile, nonanedinitrile, decanedinitrile, 1,2-bis(cyanoethoxy)ethane, 1,2,3-tris(2-cyanoethoxy)propane, 1,3,5-pentanetristitrite, or 1,3,6-hexanetristitrite; and the mass percentage of the third component in the total mass of the electrolyte is E%, 0.5≤E≤6. The electrolyte includes the third component and regulates the value of E within the above range, which is conducive to improving the stability of the positive electrode interface, reducing the side reaction of the positive electrode sheet and the electrolyte, thereby improving the cycle performance and low-temperature discharge performance of the secondary battery.

[0017] In an embodiment of the present application, the electrolyte further includes a fourth component, and the fourth component includes at least one of the following compounds: ethylene sulfate, vinylene carbonate, 1,3-propane sulfolane, propylene-1,3-sulfonic acid lactone; and the mass percentage of the fourth component in the total mass of the electrolyte is F%, 0.01≤F≤5. The electrolyte includes the fourth component and regulates the value of F within the above range, which can further enhance the interface protection of the silicon-containing negative electrode sheet, while avoiding a large increase in electrolyte impedance, thereby further improving the cycle stability of the secondary battery, while taking into account the low-temperature discharge performance of the secondary battery.

[0018] In an embodiment of the present application, the silicon-containing active material comprises at least one of silicon-oxygen composite material or silicon-carbon composite material. The negative electrode sheet comprising the silicon-containing active material of the above-mentioned kind is advantageous in improving both the cycle stability and the low-temperature discharge performance of the secondary battery.

[0019] In an embodiment of the present application, the electrolyte further comprises a nitrogen-containing lithium salt, the nitrogen-containing lithium salt comprises at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bisfluorosulfonylimide salt (LiFSI) or lithium nitrate (LiNO3); the mass percentage of the nitrogen-containing lithium salt in the electrolyte is G%, 0.1≤G≤7 based on the total mass of the electrolyte. The electrolyte comprising the nitrogen-containing lithium salt and regulating the value of G within the above-mentioned range has good solubility and dissociation ability, which can further ensure the ion conduction ability of the electrolyte, thereby further improving the cycle stability and the low-temperature discharge performance of the secondary battery.

[0020] 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.

[0021] The present application provides a secondary battery and an electronic device comprising the same, the secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; the negative electrode sheet comprising a negative electrode material layer, the negative electrode material layer comprising a silicon-containing active material, the silicon-containing active material comprising silicon element, the mass percentage of the silicon element in the negative electrode material layer being A%, 1≤A≤20 based on the total mass of the negative electrode material layer; the electrolyte comprising: (1) a first component, the first component comprising at least one of a compound of formula I or a compound of formula II; and (2) a second component; the mass percentage of the first component in the electrolyte being B%, the mass percentage of the second component being C%, 25≤B≤70, 0.07≤C / B≤1 based on the total mass of the electrolyte. In the secondary battery of the present application, 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 / B are regulated within the above-mentioned range, which can form good protection for the positive electrode and the negative electrode, so that the secondary battery has good cycle stability, at the same time, the first component has low binding energy with lithium ions, and the second component can reduce the viscosity of the electrolyte and reduce the resistance of lithium ion transport, thereby making the secondary battery have good low-temperature discharge performance.

[0022] Of course, implementing any of the products or methods of the present application does not necessarily require achieving all the advantages described above at the same time. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. All other embodiments obtained by those skilled in the art based on the present application are within the scope of protection of the present application.

[0024] It should be noted that in the specific embodiments of the present application, the present application is explained by taking lithium ion batteries as an example of secondary batteries, but the secondary batteries of the present application are not limited to lithium ion batteries. The specific technical solutions are as follows:

[0025] The first aspect of the present application provides a secondary battery, which comprises 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, the mass percentage of the silicon element is A% based on the total mass of the negative electrode material layer, 1≤A≤20, for example, the value of A 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 composed of any two of them; the electrolyte comprises: (1) a first component, the first component comprises at least one of a compound of formula I or a compound of formula II:

[0026] wherein, R 11 and R 12 are each independently a fluorine-substituted or unsubstituted C1 to C10 alkyl, R 11 and R 12 are each independently a fluorine-substituted or unsubstituted C1 to C10 alkyl, R 21 and R 22 are each independently a fluorine-substituted or unsubstituted C1 to C10 alkyl, R 21 and R 22(1) At least one of the following is fluorinated; and (2) a second component comprising at least one of the following compounds: ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, dimethyl carbonate or diethyl carbonate; the first component is B% by mass based on the total mass of the electrolyte, and the second component is C% by mass, wherein 25 ≤ B ≤ 70, for example, the value of B can be 25, 27, 28, 30, 32, 33, 35, 36, 38, 40, 42, 45, 48, 50, 52, 55, 58, 60, 62, 65, 6 8, 70, or any two of these values, where 0.07 ≤ C / B ≤ 1. For example, the value of C / B can be 0.07, 0.08, 0.1, 0.12, 0.13, 0.15, 0.16, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.88, 0.9, 0.92, 0.95, 0.98, 1, or any two of these values.

[0027] The inventors discovered that when the value of A is too small, for example, less than 1, the silicon content in the negative electrode material layer is insufficient to improve the cycle stability and low-temperature discharge performance of the secondary battery. When the value of A is too large, for example, greater than 20, the reaction at the negative electrode-electrolyte interface is intense, which is detrimental to improving the cycle stability and low-temperature discharge performance of the secondary battery. When the value of B is too small, for example, less than 25, it is difficult to effectively protect the positive electrode interface, resulting in a high lithium-ion extraction barrier, which is also detrimental to improving the cycle stability and low-temperature discharge performance of the secondary battery. When the value of B is too large, the electrolyte cannot provide enough lithium ions during low-temperature discharge, increasing polarization and hindering the improvement of the cycle stability and low-temperature discharge performance of the secondary battery. When the value of C / B is too small, for example, less than 0.07, it is difficult to reduce the electrolyte viscosity, resulting in a large lithium-ion transport resistance, which is insufficient to improve the cycle stability and low-temperature discharge performance of the secondary battery. When the value of C / B is too large, for example, greater than 1, it weakens the protective effect of the positive electrode, increases the lithium-ion extraction barrier, and is also detrimental to improving the cycle stability and low-temperature discharge performance of the secondary battery. In this application's secondary battery, the negative electrode material layer includes a silicon-containing active material, and the electrolyte includes a first component and a second component. By adjusting the values ​​of A, B, and C / B within the aforementioned ranges, good protection can be provided to both the positive and negative electrodes, resulting in good cycle capacity retention and cycle stability. Simultaneously, the first component has a low binding energy with lithium ions, and the second component reduces electrolyte viscosity and alleviates lithium-ion transport resistance, thereby enabling the secondary battery to exhibit good low-temperature discharge performance. In this application, "low temperature" refers to a temperature less than or equal to -10°C.

[0028] In an embodiment of the present application, 3≤A≤15. Controlling the value of A within the above range can further improve the cycle stability and low-temperature discharge performance of the secondary battery.

[0029] In an embodiment of the present application, 30≤B≤60. Controlling the value of B within the above range can further improve the cycle stability and low-temperature discharge performance of the secondary battery.

[0030] In an embodiment of the present application, 0.1≤C / B≤0.9. Controlling the value of C / B within the above range can further improve the cycle stability and low-temperature discharge performance of the secondary battery.

[0031] In an embodiment of the present application, the first component comprises the compound of Formula I, and the mass percentage of the compound of Formula I based on the total mass of the electrolyte is 25% to 70%; in an embodiment of the present application, the mass percentage of the compound of Formula I is 30% to 60%.

[0032] In another embodiment of the present application, the first component comprises the compound of Formula II, and the mass percentage of the compound of Formula II based on the total mass of the electrolyte is 25% to 70%; in an embodiment of the present application, the mass percentage of the compound of Formula II is 30% to 60%.

[0033] In another embodiment of the present application, the first component comprises the compound of Formula I and the compound of Formula II, and the sum of the mass percentages of the compound of Formula I and the compound of Formula II based on the total mass of the electrolyte is 25% to 70%; in an embodiment of the present application, the sum of the mass percentages of the compound of Formula I and the compound of Formula II is 30% to 60%. The present application does not particularly limit the mass ratio of the compound of Formula I and the compound of Formula II, as long as the purpose of the present application can be achieved, for example, the mass ratio of the compound of Formula I and the compound of Formula II is 1:(0.5 to 1.5).

[0034] In an embodiment of the present application, 0.01≤A / (B+C)≤0.5, for example, the value of A / (B+C) can be 0.01, 0.02, 0.03, 0.05, 0.07, 0.08, 0.1, 0.12, 0.13, 0.15, 0.16, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, 0.45, 0.5, or a range between any two of the above values. Controlling the value of A / (B+C) within the above range can further improve the protection of the positive electrode and the negative electrode, while further reducing the viscosity of the electrolyte, reducing the resistance of lithium ion transmission, and thus further improving the cycle stability and low-temperature discharge performance of the secondary battery.

[0035] In an embodiment of the present application, 26≤B+C≤89, for example, the value of B+C can be 26, 28, 30, 32, 33, 35, 36, 38, 40, 42, 45, 48, 50, 52, 55, 58, 60, 62, 65, 68, 70, 73, 75, 77, 80, 82, 85, 86, 89, or a range between any two of them. Controlling the value of B+C within the above range can ensure the ion transport function of the electrolyte, reduce the viscosity of the electrolyte, and reduce the lithium ion transport resistance, thereby improving the cycle stability and low-temperature discharge performance of the secondary battery.

[0036] In an embodiment of the present application, the compound of formula I comprises at least one of the following compounds:

[0037] The electrolyte comprises the first component within the above range, which can participate in the formation of a CEI film with better stability, improve the protection of the positive electrode, and further improve the cycle stability and low-temperature discharge performance of the secondary battery.

[0038] In an embodiment of the present application, the compound of formula II comprises at least one of the following compounds:

[0039] The electrolyte comprises the first component within the above range, which can participate in the formation of a CEI film with better stability, improve the protection of the positive electrode, and further improve the cycle stability and low-temperature discharge performance of the secondary battery.

[0040] In an embodiment of the present application, the electrolyte further comprises fluoroethylene carbonate, and the mass percentage of fluoroethylene carbonate in the total mass of the electrolyte is D%, 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 between any two of them. The electrolyte comprises FEC and controls the value of D within the above range, which has good compatibility with the silicon-containing negative electrode sheet, can form a cross-linked high-toughness polymer protective layer on the negative electrode interface during the formation process of the secondary battery, improves the protection of the negative electrode sheet, and at the same time can reduce the cycle gas production, thereby improving the cycle stability and low-temperature discharge performance of the secondary battery.

[0041] In an embodiment of the present application, the electrolyte further comprises a third component, the third component comprises at least one of the following compounds: butanedinitrile, pentanedinitrile, methylpentanedinitrile, hexanedinitrile, heptanedinitrile, octanedinitrile, nonanedinitrile, decanedinitrile, 1,2-bis(cyanoethoxy)ethane, 1,2,3-tris(2-cyanoethoxy)propane, 1,3,5-pentanetristitriple or 1,3,6-hexanetristitriple; the mass percentage content of the third component is E%, 0.5≤E≤6, for example, the value of E can be 0.5, 0.6, 0.8, 1, 1.2, 1.3, 1.5, 1.6, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.7, 5, 5.2, 5.5, 5.8, 6 or a range between any two of the above values. The electrolyte comprises the third component and regulates the value of E within the above range, the third component can be adsorbed on the positive electrode interface, which is conducive to improving the stability of the positive electrode interface, reducing the side reaction of the positive electrode plate and the electrolyte, thereby improving the cycle performance and low-temperature discharge performance of the secondary battery.

[0042] In an embodiment of the present application, the electrolyte further comprises a fourth component, the fourth component comprises at least one of the following compounds: ethylene sulfate, vinylene carbonate, 1,3-propane sulfolane, propylene-1,3-sulfonic acid lactone; the mass percentage content of the fourth component is F%, 0.01≤F≤5, 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, 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 between any two of the above values. The electrolyte comprises the fourth component and regulates the value of F within the above range, which can participate in the formation of a reduction-resistant solid electrolyte interface (SEI) film during the initial formation of the secondary battery, further enhancing the interface protection of the silicon-containing negative electrode plate, while avoiding a large increase in electrolyte impedance, thereby further improving the cycle stability of the secondary battery, while taking into account the low-temperature discharge performance of the secondary battery.

[0043] In an embodiment of the present application, the silicon-containing active material comprises at least one of a silicon-oxygen composite material or a silicon-carbon composite material. Illustratively, the silicon-oxygen composite material is SiOx, 0

[0044] The preparation method of the silicon-containing active material is not particularly limited in the present application, and exemplarily, the preparation method of the silicon-containing active material can include but is not limited to the following steps: dissolving a silicon material and lithium nitrate in a solvent, drying the mixture to obtain a powder material, and then heat-treating the powder material in a carbon-containing gas to obtain the silicon-containing active material. The drying temperature is 80-120°C; the heat-treatment temperature is 300-800°C, the heat-treatment temperature rising rate is 1-10°C / min, and the heat-treatment holding time is 0.5-6h; the mass ratio of the silicon material to lithium nitrate can be (10-200):1; the silicon material can be a silicon-carbon material, a silicon-oxygen material, or a pre-lithiated silicon-oxygen material; the solvent can include but is not limited to at least one of ethanol, water, or acetone; the carbon-containing gas includes at least one of acetylene, methane, or propylene; and the mass ratio of the powder material to the carbon-containing gas can be (20-100):1. In the present application, the mass percentage of silicon in the silicon-containing active material can be regulated by regulating the mass ratio of the silicon material to lithium nitrate.

[0045] In an embodiment of the present application, the electrolyte further includes a nitrogen-containing lithium salt, the nitrogen-containing lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bisfluorosulfonylimide, or lithium nitrate; the mass percentage of the nitrogen-containing lithium salt in the electrolyte is G%, 0.1≤G≤7, 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, 5.2, 5.5, 5.7, 6, 6.3, 6.5, 6.8, 7, or a range between any two of the above values. The electrolyte includes the nitrogen-containing lithium salt and regulates the value of G within the above range, has good solubility and dissociation ability, can further ensure the ion conduction ability of the electrolyte, and the nitrogen-containing lithium salt can also help to form a stable electrolyte-electrode interface, thereby further improving the cycle stability and low-temperature discharge performance of the secondary battery.

[0046] In the present application, the fluorinated ethylene carbonate, the third component, the fourth component, the nitrogen-containing lithium salt, etc. within the above ranges can be used in any combination, as long as the purpose of the present application can be achieved.

[0047] In the present application, the electrolyte solution further includes an electrolyte salt and a non-aqueous solvent. The electrolyte salt is not particularly limited in the present application as long as the object of the present application can be achieved. For example, the electrolyte salt can include, but is not limited to, at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalato)borate (LiBOB), or lithium difluoroborate. The content of the electrolyte salt in the electrolyte solution is not particularly limited in the present application as long as the object of the present application can be achieved. For example, the mass percentage of the electrolyte salt is 8% to 15% based on the mass of the electrolyte solution.

[0048] The non-aqueous solvent is not particularly limited in the present application as long as the object of the present application can be achieved, for example, the non-aqueous solvent can include, but is not limited to, at least one of an ether compound or other organic solvents. The above-mentioned ether compound can include, but is 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. The above-mentioned other organic solvents can include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. The content of the non-aqueous solvent in the electrolyte solution is not particularly limited in the present application as long as the object of the present application can be achieved. For example, the mass percentage of the non-aqueous solvent is 0% to 66% based on the total mass of the electrolyte solution.

[0049] In an embodiment of the present application, the electrolyte solution includes the first component, the second component, the electrolyte salt, and the non-aqueous solvent. Wherein, the mass percentages of the first component, the second component, and the electrolyte salt are as described above, and the mass percentage of the non-aqueous solvent is 0% to 66% based on the total mass of the electrolyte solution. The electrolyte solution includes the first component and the second component, and the cycle stability and the low-temperature discharge performance of the secondary battery using the electrolyte solution of the present application are improved.

[0050] In an embodiment of the present application, the electrolyte solution includes the first component, the second component, the fluoroethylene carbonate, the electrolyte salt, and the non-aqueous solvent. Wherein, the mass percentages of the first component, the second component, the fluoroethylene carbonate, and the electrolyte salt are as described above, and the mass percentage of the non-aqueous solvent is 0% to 64% based on the total mass of the electrolyte solution. The electrolyte solution includes the first component, the second component, and the fluoroethylene carbonate, and the cycle stability and the low-temperature discharge performance of the secondary battery using the electrolyte solution of the present application are further improved.

[0051] In an embodiment of the present application, the electrolyte comprises the first component, the second component, the third component, the electrolyte salt, and the nonaqueous solvent. The mass percentage of the first component, the second component, the third component, and the electrolyte salt is as described above, and the mass percentage of the nonaqueous solvent is 0% to 65% based on the total mass of the electrolyte. The electrolyte comprises the first component, the second component, and the third component, and the cycle stability and low-temperature discharge performance of the secondary battery using the electrolyte of the present application are further improved.

[0052] In an embodiment of the present application, the electrolyte comprises the first component, the second component, the fourth component, the electrolyte salt, and the nonaqueous solvent. The mass percentage of the first component, the second component, the fourth component, and the electrolyte salt is as described above, and the mass percentage of the nonaqueous solvent is 0% to 65% based on the total mass of the electrolyte. The electrolyte comprises the first component, the second component, and the fourth component, and the cycle stability and low-temperature discharge performance of the secondary battery using the electrolyte of the present application are further improved.

[0053] In an embodiment of the present application, the electrolyte comprises the first component, the second component, the nitrogen-containing lithium salt, the electrolyte salt, and the nonaqueous solvent. The mass percentage of the first component, the second component, the nitrogen-containing lithium salt, and the electrolyte salt is as described above, and the mass percentage of the nonaqueous solvent is 0% to 65% based on the total mass of the electrolyte. The electrolyte comprises the first component, the second component, and the nitrogen-containing lithium salt, and the cycle stability and low-temperature discharge performance of the secondary battery using the electrolyte of the present application are further improved.

[0054] In an embodiment of the present application, the electrolyte comprises the first component, the second component, the fluorinated ethylene carbonate, the third component, the electrolyte salt, and the nonaqueous solvent. The mass percentage of the first component, the second component, the fluorinated ethylene carbonate, the third component, and the electrolyte salt is as described above, and the mass percentage of the nonaqueous solvent is 0% to 63% based on the total mass of the electrolyte. The electrolyte comprises the first component, the second component, the fluorinated ethylene carbonate, and the third component, and the cycle stability and low-temperature discharge performance of the secondary battery using the electrolyte of the present application are further improved.

[0055] In an embodiment of the present application, the electrolyte comprises the first component, the second component, the fluorinated ethylene carbonate, the fourth component, the electrolyte salt, and the nonaqueous solvent. The mass percentage of the first component, the second component, the fluorinated ethylene carbonate, the fourth component, and the electrolyte salt is as described above, and the mass percentage of the nonaqueous solvent is 0% to 63% based on the total mass of the electrolyte. The electrolyte comprises the first component, the second component, the fluorinated ethylene carbonate, and the fourth component, and the cycle stability and low-temperature discharge performance of the secondary battery using the electrolyte of the present application are further improved.

[0056] In an embodiment of the present application, the electrolyte comprises the first component, the second component, the fluorinated ethylene carbonate, the nitrogen-containing lithium salt, the electrolyte salt, and the non-aqueous solvent. The mass percentage of the first component, the second component, the fluorinated ethylene carbonate, the nitrogen-containing lithium salt, and the electrolyte salt is as described above, and the mass percentage of the non-aqueous solvent is 0% to 63% based on the total mass of the electrolyte. The electrolyte comprises the first component, the second component, the fluorinated ethylene carbonate, and the nitrogen-containing lithium salt, and the cycle stability and low-temperature discharge performance of the secondary battery using the electrolyte of the present application are further improved.

[0057] In an embodiment of the present application, the electrolyte comprises the first component, the second component, the third component, the fourth component, the electrolyte salt, and the non-aqueous solvent. The mass percentage of the first component, the second component, the third component, the fourth component, and the electrolyte salt is as described above, and the mass percentage of the non-aqueous solvent is 0% to 65% based on the total mass of the electrolyte. The electrolyte comprises the first component, the second component, the third component, and the fourth component, and the cycle stability and low-temperature discharge performance of the secondary battery using the electrolyte of the present application are further improved.

[0058] In an embodiment of the present application, the electrolyte comprises the first component, the second component, the third component, the nitrogen-containing lithium salt, the electrolyte salt, and the non-aqueous solvent. The mass percentage of the first component, the second component, the third component, the nitrogen-containing lithium salt, and the electrolyte salt is as described above, and the mass percentage of the non-aqueous solvent is 0% to 65% based on the total mass of the electrolyte. The electrolyte comprises the first component, the second component, the third component, and the nitrogen-containing lithium salt, and the cycle stability and low-temperature discharge performance of the secondary battery using the electrolyte of the present application are further improved.

[0059] In an embodiment of the present application, the electrolyte comprises the first component, the second component, the fourth component, the nitrogen-containing lithium salt, the electrolyte salt, and the non-aqueous solvent. The mass percentage of the first component, the second component, the fourth component, the nitrogen-containing lithium salt, and the electrolyte salt is as described above, and the mass percentage of the non-aqueous solvent is 0% to 65% based on the total mass of the electrolyte. The electrolyte comprises the first component, the second component, the fourth component, and the nitrogen-containing lithium salt, and the cycle stability and low-temperature discharge performance of the secondary battery using the electrolyte of the present application are further improved.

[0060] In an embodiment of the present application, the electrolyte includes the first component, the second component, the fluoroethylene carbonate, the third component, the fourth component, the electrolyte salt, and the non-aqueous solvent. The mass percentage of the first component, the second component, the fluoroethylene carbonate, the third component, the fourth component, and the electrolyte salt is as described above, and the mass percentage of the non-aqueous solvent is 0% to 63% based on the total mass of the electrolyte. The electrolyte includes the first component, the second component, the fluoroethylene carbonate, the third component, and the fourth component, and the cycle stability and the low-temperature discharge performance of the secondary battery using the electrolyte of the present application are further improved.

[0061] In an embodiment of the present application, the electrolyte includes the first component, the second component, the fluoroethylene carbonate, the third component, the nitrogen-containing lithium salt, the electrolyte salt, and the non-aqueous solvent. The mass percentage of the first component, the second component, the fluoroethylene carbonate, the third component, the nitrogen-containing lithium salt, and the electrolyte salt is as described above, and the mass percentage of the non-aqueous solvent is 0% to 63% based on the total mass of the electrolyte. The electrolyte includes the first component, the second component, the fluoroethylene carbonate, the third component, and the nitrogen-containing lithium salt, and the cycle stability and the low-temperature discharge performance of the secondary battery using the electrolyte of the present application are further improved.

[0062] In an embodiment of the present application, the electrolyte includes the first component, the second component, the fluoroethylene carbonate, the fourth component, the nitrogen-containing lithium salt, the electrolyte salt, and the non-aqueous solvent. The mass percentage of the first component, the second component, the fluoroethylene carbonate, the fourth component, the nitrogen-containing lithium salt, and the electrolyte salt is as described above, and the mass percentage of the non-aqueous solvent is 0% to 63% based on the total mass of the electrolyte. The electrolyte includes the first component, the second component, the fluoroethylene carbonate, the fourth component, and the nitrogen-containing lithium salt, and the cycle stability and the low-temperature discharge performance of the secondary battery using the electrolyte of the present application are further improved.

[0063] In an embodiment of the present application, the electrolyte includes the first component, the second component, the third component, the fourth component, the nitrogen-containing lithium salt, the electrolyte salt, and the non-aqueous solvent. The mass percentage of the first component, the second component, the third component, the fourth component, the nitrogen-containing lithium salt, and the electrolyte salt is as described above, and the mass percentage of the non-aqueous solvent is 0% to 65% based on the total mass of the electrolyte. The electrolyte includes the first component, the second component, the third component, the fourth component, and the nitrogen-containing lithium salt, and the cycle stability and the low-temperature discharge performance of the secondary battery using the electrolyte of the present application are further improved.

[0064] In an embodiment of the present application, the electrolyte comprises the first component, the second component, the fluoroethylene carbonate, the third component, the fourth component, the lithium salt containing nitrogen, the electrolyte salt, and the non-aqueous solvent. The mass percentage content of the non-aqueous solvent is 0% to 63% based on the total mass of the electrolyte. The electrolyte comprises the first component, the second component, the fluoroethylene carbonate, the third component, the fourth component, and the lithium salt containing nitrogen. The secondary battery using the electrolyte of the present application has further improved cycle stability and low-temperature discharge performance.

[0065] In the present application, the negative electrode tab comprises a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The "negative electrode material layer 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 the thickness direction of the negative electrode current collector, or can be disposed on two surfaces of the negative electrode current collector along the thickness direction of the negative electrode current collector. It should be noted that the "surface" herein can be the entire area of the surface of the negative electrode current collector, or can be part of the area of the surface of the negative electrode current collector, and the present application does not have a particular limitation as long as the purpose of the present application can be achieved.

[0066] The negative electrode current collector is not particularly limited in the present application as long as the purpose of the present application can be achieved, for example, it can comprise a copper foil, a copper alloy foil, a nickel foil, a stainless steel foil, a titanium foil, a foamed nickel, a foamed copper, or a composite current collector, and exemplarily, the composite current collector can be a lithium-copper composite current collector, a carbon-copper composite current collector, a nickel-copper composite current collector, a titanium-copper composite current collector, etc.

[0067] The negative electrode material layer can further comprise other negative electrode active materials, and the present application does not have a particular limitation on the other negative electrode active materials as long as the purpose of the present application can be achieved, for example, the other negative electrode active materials can comprise but are not limited to at least one of natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, soft carbon, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithiated TiO2-Li4Ti5O 12 or Li-Al alloy.

[0068] In the present application, the mass percentage content of silicon in the negative electrode material layer can also be regulated by regulating the mass ratio of the silicon-containing active material and the other negative electrode active material.

[0069] In some embodiments of the present application, the negative electrode material layer can further include a conductive agent and a binder, and the kind of the conductive agent and the binder is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the conductive agent can include, but is not limited to, at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, a metal material, or a conductive polymer, and the conductive carbon black can include, but is not limited to, at least one of acetylene black or Ketjen black. The above-mentioned carbon nanotubes can include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers can include, but are not limited to, vapor grown carbon fibers (VGCF) and / or nanocarbon fibers. The above-mentioned metal material can include, but is not limited to, metal powder and / or metal fibers, and in particular, the metal can include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The above-mentioned conductive polymer can include, but is not limited to, at least one of polyphenylene derivative, polyaniline, polythiophene, polyacetylene, or polypyrrole. For example, the binder can 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, butadiene-styrene rubber, or polyvinylidene fluoride. The mass ratio of the negative active material, the conductive agent, and the binder in the negative electrode material layer is not particularly limited in the present application, and a person skilled in the art can select according to actual needs as long as the purpose of the present application can be achieved. The negative electrode material layer can further include a thickening agent, and the content and kind of the thickening agent is not particularly limited in the present application, and a conventional kind and content known in the art can be used as long as the purpose of the present application can be achieved.

[0070] The thickness of the negative electrode material layer is not particularly limited in the present application as long as the purpose of the present application can be achieved, and for example, the thickness of the negative electrode material layer is 30 μm to 120 μm. The thickness of the negative electrode current collector is not particularly limited in the present application as long as the purpose of the present application can be achieved, and for example, the thickness of the negative electrode current collector is 4 μm to 15 μm.

[0071] Optionally, the negative electrode sheet can further include a conductive layer between the negative electrode current collector and the negative electrode material layer. The composition of the conductive layer is not particularly limited in the present application, and can be a conventional conductive layer used in the art. For example, the conductive layer includes a conductive agent and a binder. The conductive agent and the binder in the conductive layer are not particularly limited in the present application, and for example, can be at least one of the above-mentioned conductive agent and the above-mentioned binder.

[0072] In the present application, the positive electrode tab includes a positive current collector and a positive material layer disposed on at least one surface of the positive current collector. The "positive material layer disposed on at least one surface of the positive current collector" means that the positive material layer can be disposed on one surface of the positive current collector along the thickness direction of the positive current collector, or can be disposed on two surfaces of the positive current collector along the thickness direction of the positive current collector. It should be noted that the "surface" herein can be the entire area of the surface of the positive current collector, or can be part of the area of the surface of the positive current collector, which is not particularly limited in the present application as long as the purpose of the present application can be achieved.

[0073] The positive current collector is not particularly limited in the present application as long as the purpose of the present application can be achieved, for example, it can include an aluminum foil, an aluminum alloy foil, or a composite current collector (for example, an aluminum-carbon composite current collector), etc.

[0074] The positive material layer includes a positive active material, which is not particularly limited in the present application as long as the purpose of the present application can be achieved, for example, the positive active material can include but is not limited to at least one of nickel-cobalt-manganese lithium (for example, NCM811, NCM622, NCM523, NCM111), nickel-cobalt-aluminum lithium, lithium iron phosphate, lithium-rich manganese-based material, lithium cobaltate (LiCoO2), lithium manganate, lithium manganese iron phosphate, or lithium titanate.

[0075] The positive material layer can further include a conductive agent and a binder, which are not particularly limited in the present application as long as the purpose of the present application can be achieved, for example, it can be at least one of the above-mentioned conductive agent and the above-mentioned binder. The mass ratio of the positive active material, the conductive agent, and the binder in the positive material layer is not particularly limited in the present application, which can be selected by a person skilled in the art according to actual needs as long as the purpose of the present application can be achieved.

[0076] The thickness of the positive current collector and the positive material layer is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the thickness of the positive current collector is 5 μm to 20 μm, and the thickness of the positive material layer is 30 μm to 120 μm.

[0077] Optionally, the positive electrode tab can further include a conductive layer, which is located between the positive current collector and the positive material layer. The composition of the conductive layer is not particularly limited and can be a commonly used conductive layer in the art. The conductive layer includes a conductive agent and a binder. The conductive agent and the binder in the conductive layer are not particularly limited in the present application, for example, it can be at least one of the above-mentioned conductive agent and the above-mentioned binder.

[0078] In the present application, the secondary battery further includes a separator. The separator according to the present application is not particularly limited as long as the object of the present application can be achieved. For example, the material of the separator can include, but is not limited to, at least one of polyethylene (PE), polyolefin (PO) based on polypropylene (PP), polyester (for example, polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The type of the separator can include at least one of a woven film, a nonwoven film, a microporous film, a composite film, a calendered film, or a spunlaced film.

[0079] In some embodiments of the present application, the separator can include a base layer and a surface treatment layer. The base layer can be a nonwoven fabric, a film, or a composite film having a porous structure, and the material of the base layer can include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used.

[0080] Optionally, the surface treatment layer is provided on at least one surface of the base layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance.

[0081] In some embodiments of the present application, the inorganic layer includes inorganic particles and a binder. The inorganic particles according to the present application are not particularly limited, and for example, the inorganic particles can include at least one of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. The binder according to the present application is not particularly limited, and for example, the binder can be at least one of the above-described binders. In some embodiments of the present application, the polymer layer includes a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylic acid salt, polyvinylpyrrolidone, polyvinyl ether, or polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0082] In the present application, the thickness of the separator is not particularly limited as long as the object of the present application can be achieved, and for example, the thickness of the separator can be 3 μm to 30 μm.

[0083] In the present application, the secondary battery further comprises a housing for accommodating the positive electrode sheet, the separator, the negative electrode sheet, the electrolyte, and other components known in the art of secondary batteries, and the present application does not limit the above-mentioned other components. The housing is not particularly limited in the present application and can be a housing known in the art as long as the purpose of the present application can be achieved. For example, the housing can be a hard-shell housing or a flexible housing. The material of the hard-shell housing can be metal, and the type of metal is not limited in the present application, and a metal hard-shell housing known in the art can be used as long as the purpose of the present application can be achieved. The flexible housing can be a metal plastic film, such as an aluminum plastic film, a steel plastic film, etc.

[0084] The preparation process of the secondary battery of the present application is well known to those skilled in the art, and the present application is not particularly limited, for example, the preparation process of the secondary battery can include but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding, etc. according to the need to obtain the electrode assembly with a winding structure, placing the electrode assembly into the housing, injecting the electrolyte into the housing and sealing, to obtain the secondary battery. Alternatively, the positive electrode sheet, the separator and the negative electrode sheet are stacked in order, and then the four corners of the entire stack structure are fixed with adhesive tape to obtain the electrode assembly with a stack structure, the electrode assembly is placed into the housing, the electrolyte is injected into the housing and sealed, to obtain the secondary battery. In addition, the overcurrent prevention element, the guide plate, etc. can also be placed in the housing according to the need, so as to prevent the pressure rise in the secondary battery and overcharge and discharge.

[0085] The type of secondary battery is not particularly limited in the present application, which can include any device that undergoes an electrochemical reaction. For example, the secondary battery can include but is not limited to: lithium metal secondary battery, lithium ion battery, sodium ion battery, lithium polymer secondary battery, lithium ion polymer secondary battery.

[0086] The second aspect of the present application provides an electronic device comprising the secondary battery of any one of the preceding embodiments. The secondary battery provided in the present application has good cycle stability and low-temperature discharge performance, so that the electronic device of the present application has a longer service life.

[0087] The kind of the electronic device is not particularly limited in the present application, and it can be any electronic device known in the art. In some embodiments of the present application, the electronic device can include, but is not limited to, a notebook computer, a pen input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile, a portable copying machine, a portable printer, a head-mounted stereo headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio recorder, a radio, a backup power supply, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, an illuminating appliance, a toy, a game machine, a timepiece, an electric tool, a flash, a camera, a household large storage battery, and a lithium ion capacitor, etc.

[0088] Examples

[0089] Hereinafter, examples and comparative examples are given to more specifically describe the embodiments of the present application. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are on a mass basis.

[0090] Test methods and apparatus:

[0091] Test of mass percentage of silicon element:

[0092] A lithium ion battery discharged at 0.5C to 3.0V was disassembled, and the negative electrode sheet was removed. The negative electrode sheet was soaked in dimethyl carbonate (DMC) for 20 minutes, and then rinsed with DMC and acetone in turn. Then the negative electrode sheet was placed in an oven and baked at 80°C for 12 hours to obtain a negative electrode sheet. The negative electrode sheet was dried in a vacuum oven at 100°C for 24 hours. The negative electrode material layer on the negative electrode sheet was scraped off with a blade, and then an ICP (Inductively coupled plasma) analyzer was used to test the mass percentage of silicon element in the negative electrode material layer.

[0093] Test of room temperature cycle performance:

[0094] The lithium ion battery was charged at 1.2C constant current to 4.25V at 25℃, charged at 4.25V constant voltage to the current of 0.7C, then charged at 0.7C constant current to 4.5V, charged at 4.5V constant voltage to the current of 0.05C, and then rested for 5min, and then discharged at 0.5C constant current to 3.0V. At this time, it was the first cycle, and the discharge capacity was recorded. The lithium ion battery was cycled according to the above conditions, and the discharge capacity of the lithium ion battery was measured each time. Taking the first discharge capacity as 100%, the charge and discharge cycle was repeated until the discharge capacity retention rate decayed to 80% of the first discharge capacity, the cycle number was recorded, and was used as an index for evaluating the room temperature cycle capacity retention rate of the lithium ion battery. Among them, the discharge capacity retention rate = (the capacity after each discharge / first discharge capacity) x 100%.

[0095] Low-temperature discharge performance test:

[0096] The lithium ion battery was charged at 0.5C constant current to 4.5V at 25℃, and then charged at 4.5V constant voltage to the current of 0.025C. At 25℃, it was discharged at 0.2C constant current to 3.0V, and the discharge capacity was recorded and marked as C0. Then the lithium ion battery was charged at 0.5C constant current to 4.5V at 25℃, and then charged at 4.5V constant voltage to the current of 0.025C. At-20℃, it was discharged at 0.2C constant current to 3.0V, and the discharge capacity was recorded and marked as C1. The low-temperature discharge capacity retention rate = C1 / C0 x 100%.

[0097] Example 1-1

[0098] <Preparation of silicon-containing active material>

[0099] The silicon oxide material SiO2 and lithium nitrate were dispersed in ethanol, uniformly mixed, and then dried to obtain a powder material. Then the powder material was heat treated in methane to obtain a silicon-containing active material with amorphous carbon on the surface. The drying temperature was 100℃; the heat treatment temperature was 450℃, the heat treatment heating rate was 5℃ / min, and the heat treatment holding time was 3.2h; the mass ratio of SiO2 to lithium nitrate was 36:1; and the mass ratio of the powder material to methane was 30:1. The silicon element mass percentage content of the silicon-containing active material was 65%.

[0100] <Preparation of negative electrode sheet>

[0101] The above-mentioned silicon-containing active material, artificial graphite, conductive agent carbon nanotube (CNT), conductive carbon black (Super P), and binder lithium polyacrylate (PAA-Li) were mixed in a mass ratio of 1.54:88.46:1.5:0.5:8, and then deionized water was added as a solvent to prepare a negative electrode slurry with a solid content of 54%, which was stirred in a vacuum stirrer until the system became a uniform negative electrode slurry. The negative electrode slurry was uniformly coated on one surface of a negative current collector copper foil with a thickness of 8 μm, and was dried at 85°C to obtain a single-sided coated negative electrode sheet with a negative electrode material layer thickness of 100 μm. Then, the above steps were repeated on the other surface of the negative electrode sheet to obtain a double-sided coated negative electrode sheet. After the coating was completed, the negative electrode sheet was cold-pressed and cut into a specification of 76 mm x 851 mm for use. The compaction density of the negative electrode sheet was 1.4 g / cm 3 .

[0102] <Manufacture of a positive electrode sheet>

[0103] The above-mentioned silicon-containing active material, artificial graphite, conductive agent carbon nanotube (CNT), conductive carbon black (Super P), and binder lithium polyacrylate (PAA-Li) were mixed in a mass ratio of 1.54:88.46:1.5:0.5:8, and then deionized water was added as a solvent to prepare a negative electrode slurry with a solid content of 54%, which was stirred in a vacuum stirrer until the system became a uniform negative electrode slurry. The negative electrode slurry was uniformly coated on one surface of a negative current collector copper foil with a thickness of 8 μm, and was dried at 85°C to obtain a single-sided coated negative electrode sheet with a negative electrode material layer thickness of 100 μm. Then, the above steps were repeated on the other surface of the negative electrode sheet to obtain a double-sided coated negative electrode sheet. After the coating was completed, the negative electrode sheet was cold-pressed and cut into a specification of 76 mm x 851 mm for use. The compaction density of the negative electrode sheet was 1.4 g / cm 3 .

[0104] <Manufacture of an electrolyte>

[0105] In an argon atmosphere glove box with a water content of less than 10 ppm, methyl ethyl carbonate was used as a non-aqueous solvent, and then a first component I-3, a second component propyl propionate, and an electrolyte salt LiPF6 were added to the non-aqueous solvent and mixed uniformly to obtain an electrolyte. The mass percentage content B% of the first component was 40%, the mass percentage content C% of the second component was 8%, and the mass percentage content of the electrolyte salt was 12.5% based on the total mass of the electrolyte, and the balance was the non-aqueous solvent.

[0106] <Separator>

[0107] A polyethylene (PE) porous film with a thickness of 5 μm (provided by Shanghai Enjie Company) was used.

[0108] <Manufacture of lithium ion battery>

[0109] The positive electrode sheet, the separator, and the negative electrode sheet prepared above were stacked in order with the separator between the positive electrode sheet and the negative electrode sheet to play a role of separation, and then wound to obtain an electrode assembly. After welding the tab, the electrode assembly was put into an aluminum plastic film packaging shell, placed in a vacuum oven at 85°C for 12h to remove water, injected with the electrolyte prepared above, and subjected to vacuum packaging, standing, formation (0.02C constant current charging to 3.5V, and then 0.1C constant current charging to 3.9V), shaping, capacity test, and other processes to obtain a lithium ion battery.

[0110] Example 1-2 to Example 1-5

[0111] Except that the mass percentage content A% of silicon element in the negative electrode material layer was as shown in Table 1 by adjusting the mass ratio of the silicon-containing active material and artificial graphite in the <Manufacture of negative electrode sheet>, the rest was the same as Example 1-1.

[0112] Example 1-6 to Example 1-19

[0113] Except that the types and mass percentage contents B% of the first component, the types and mass percentage contents C% of the second component were adjusted according to Table 1 in the <Manufacture of electrolyte>, the mass percentage content of the non-aqueous solvent changed accordingly, and the mass percentage content of the electrolyte salt remained unchanged, the rest was the same as Example 1-3.

[0114] Example 1-20

[0115] Except that the mass percentage content A% of silicon element in the negative electrode material layer was as shown in Table 1 by adjusting the mass ratio of the silicon-containing active material and artificial graphite in the <Manufacture of negative electrode sheet>, the rest was the same as Example 1-6.

[0116] Example 1-21

[0117] Except that the types of the silicon-containing active material were as shown in Table 1 by adjusting the mass ratio of the silicon material to the silicon carbon material SiC and lithium nitrate in the <Manufacture of silicon-containing active material>, the rest was the same as Example 1-3.

[0118] Example 2-1 to Example 2-38

[0119] The rest is the same as Example 1-3 except that the fluorinated ethylene carbonate, the third component, the fourth component, the nitrogen-containing lithium salt are added according to Table 2 in the preparation of electrolyte, the mass percentage content D% of fluorinated ethylene carbonate, the type and mass percentage content E% of the third component, the type and mass percentage content F% of the fourth component, the type and mass percentage content G% of the nitrogen-containing lithium salt are adjusted according to Table 2, the mass percentage content of the non-aqueous solvent is changed accordingly, the mass percentage content of the first component, the second component and the electrolyte salt remains unchanged.

[0120] Comparative Examples 1-1 to 1-13

[0121] The rest is the same as Example 1-1 except that the relevant preparation parameters are adjusted according to Table 1. When the silicon element is not contained, the silicon-containing active material in the negative electrode active material is replaced by artificial graphite. When the mass percentage content B% of the first component and / or the mass percentage content C% of the second component changes, the mass percentage content of the non-aqueous solvent changes accordingly, and the mass percentage content of the electrolyte salt remains unchanged. The mass percentage content A% of the silicon element in the negative electrode material layer is adjusted by adjusting the mass ratio of the silicon-containing active material and artificial graphite in the preparation of the negative electrode sheet as shown in Table 1.

[0122] As can be seen from Example 1-1 to Example 1-21 and Comparative Examples 1-1 to 1-13, when the negative electrode sheet includes a silicon-containing active material, the value of the content A of the silicon element in the negative electrode material layer is regulated within the range of the present application, the electrolyte includes the first component and the second component, and the values of B and C / B are regulated within the range of the present application, the lithium ion battery can have both high normal temperature cycle number and low temperature discharge capacity retention rate, indicating that the lithium ion battery has both good cycle stability and low temperature discharge performance.

[0123] The value of A / (B+C) generally affects the cycle stability and low temperature discharge performance of the lithium ion battery. As can be seen from Example 1-1 to Example 1-6 and Example 1-20, when the value of A / (B+C) is regulated within the range of the present application, the lithium ion battery can have both high normal temperature cycle number and low temperature discharge capacity retention rate, indicating that the lithium ion battery has both good cycle stability and low temperature discharge performance.

[0124] The first component, the second component, and the type of silicon-containing active material generally affect the cycle stability and low-temperature discharge performance of the lithium ion battery. As can be seen from Examples 1-3, Examples 1-15 to 1-19, and Example 21, the lithium ion battery selected from the first component, the second component, and the type of silicon-containing active material within the scope of the present application can have both a high number of cycles at room temperature and a high capacity retention rate at low temperature, indicating that the lithium ion battery has both good cycle stability and low-temperature discharge performance.

[0125] The content of fluoroethylene carbonate generally affects the cycle stability and low-temperature discharge performance of the lithium ion battery. As can be seen from Examples 1-3, Examples 2-1 to 2-5, when the electrolyte includes fluoroethylene carbonate within the content range of the present application, the lithium ion battery can have a higher number of cycles at room temperature and a higher capacity retention rate at low temperature, indicating that the lithium ion battery has both better cycle stability and low-temperature discharge performance.

[0126] The type and content of the third component, the type and content of the fourth component, and the type and content of the nitrogen-containing lithium salt generally affect the cycle stability and low-temperature discharge performance of the lithium ion battery. As can be seen from Examples 1-3, Examples 2-6 to 2-28, when the electrolyte includes the third component, the fourth component, or the nitrogen-containing lithium salt within the type and content range of the present application, the lithium ion battery can have both a higher number of cycles at room temperature and a higher capacity retention rate at low temperature, indicating that the lithium ion battery has both better cycle stability and low-temperature discharge performance.

[0127] Different types of electrolyte generally affect the cycle stability and low-temperature discharge performance of the lithium ion battery. As can be seen from Examples 1-3, Examples 2-1 to 2-38, when the electrolyte is selected from the fluoroethylene carbonate, the third component, the fourth component, and the nitrogen-containing lithium salt of the present application, the number of cycles at room temperature and the capacity retention rate at low temperature of the lithium ion battery can be further improved, indicating that the cycle stability and low-temperature discharge performance of the lithium ion battery are further improved.

[0128] It should be noted that in this document, relational terms such as first and second and the like can only be used to distinguish one entity or action from another entity or action, without necessarily requiring or implying that there is any such actual relationship or order between these entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof are intended to cover non-exclusive inclusions, so that a process, method, article, or apparatus that includes a list of elements does not only include those elements, but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0129] The use of the terms "one or more of," "at least one of," or "one or more of A, B, and C, " or other similar terms, means that any single one of A, B, or C can be used, or any combination of A, B, and C can be used. For example, "at least one of A or B" means that A alone can be used, B alone can be used, or that both A and B can be used.

[0130] Each of the embodiments in the present specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other. Each of the embodiments focuses on the difference from other embodiments.

[0131] The above only describes the preferred embodiments of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of protection of the present application.

Claims

1. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte solution; the negative electrode sheet comprising a negative electrode material layer, the negative electrode material layer comprising a silicon-containing active material, the silicon-containing active material comprising a silicon element, a mass percentage content of the silicon element being A% based on a total mass of the negative electrode material layer, 1 ≤ A ≤ 20; the electrolyte solution comprising: (1) a first component comprising at least one of ethylene carbonate, propylene carbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, or fluoroethylene carbonate; (2) a second component comprising at least one of ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, dimethyl carbonate, or diethyl carbonate; a mass percentage content of the first component being B% and a mass percentage content of the second component being C% based on a total mass of the electrolyte solution, wherein 25 ≤ B ≤ 70 and 0.07 ≤ C / B ≤ 1. (1) a first component comprising at least one of a compound of Formula I or a compound of Formula II: wherein R 11 and R 12 are each independently a fluorine-substituted or unsubstituted C1to C10alkyl, at least one of R 11 and R 12 is fluorine-substituted; R 21 and R 22 are each independently a fluorine-substituted or unsubstituted C1to C10alkyl, at least one of R 21 and R 22 is fluorine-substituted; and The secondary battery satisfies at least one of the following conditions: a) 30 ≤ B ≤ 60; b) 0.1 ≤ C / B ≤ 0.

9. 0.01 ≤ A / (B+C) ≤ 0.

5.

2. The secondary battery according to claim 1, wherein 3≤A≤15。 3. The secondary battery according to claim 1, wherein The electrolyte solution further comprises fluoroethylene carbonate, a mass percentage content of the fluoroethylene carbonate being D% based on a total mass of the electrolyte solution, 2 ≤ D ≤ 12. The electrolyte solution further comprises a third component, the third component comprising at least one of succinonitrile, glutaronitrile, methylglutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelonitrile, sebaconitrile, 1,2-bis(cyanoethoxy)ethane, 1,2,3-tris(2-cyanoethoxy)propane, 1,3,5-pentanetrione, or 1,3,6-hexanetrione; a mass percentage content of the third component being E% based on a total mass of the electrolyte solution, 0.5 ≤ E ≤ 6. The electrolyte solution further comprises a fourth component, the fourth component comprising at least one of ethylene sulfate, vinylene carbonate, 1,3-propane sultone, or propenyl-1,3-sultone; a mass percentage content of the fourth component being F% based on a total mass of the electrolyte solution, 0.01 ≤ F ≤ 5.

4. The secondary battery according to claim 1, wherein The silicon-containing active material comprises at least one of silicon-oxygen composite material or silicon-carbon composite material.

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

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

7. The secondary battery according to any one of claims 1 to 6, wherein The electrolyte solution further comprises a nitrogen-containing lithium salt, the nitrogen-containing lithium salt comprising at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bisfluorosulfonylimide, or lithium nitrate; a mass percentage content of the nitrogen-containing lithium salt being G% based on a total mass of the electrolyte solution, 0.1 ≤ G ≤ 7.

8. The secondary battery according to any one of claims 1 to 6, wherein 12.An electronic device comprising the secondary battery according to any one of claims 1 to 11. ​ 9. The secondary battery according to any one of claims 1 to 6, wherein ​ ​ 10. The secondary battery according to any one of claims 1 to 6, wherein ​ 11. The secondary battery according to any one of claims 1 to 6, wherein ​ ​ ​

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