An electrochemical device and an electronic device

Abstract

This application provides an electrochemical device and an electronic device. The electrochemical device includes a negative electrode and an electrolyte. The negative electrode includes a negative electrode material layer, which comprises a silicon-based material. The silicon-based material includes silicon element, and the mass percentage of silicon element is 30% to 60% based on the total mass of the negative electrode material layer. The electrolyte comprises a compound of formula I and fluoroethylene carbonate, wherein R1 and R2 are each independently selected from substituted or unsubstituted C1 to C5 alkyl groups and substituted or unsubstituted C6 to C5 alkyl groups. 10 The aryl group; when substituted, the substituent in the alkyl or aryl group is a fluorine atom, and A is selected from carbon-carbon double bonds, carbon-carbon triple bonds, or nitrogen-nitrogen double bonds. By selecting compound of formula I as a pre-film additive and combining it with fluoroethylene carbonate, the long-term cycling stability and high-temperature storage performance of the electrochemical device are improved.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to an electrochemical device and an electronic device. Background Technology

[0002] With the rapid development of electronic products, electrochemical devices (such as lithium-ion batteries) are widely used in mobile phones, laptops, tablets, drones, electric vehicles, power tools, and power storage systems due to their advantages such as high energy density, miniaturization, and lightweight design. Especially in the 3C product sector, consumer users still have a significant demand for improved battery life, thus placing higher requirements on the energy density of electrochemical devices.

[0003] To further improve the energy density of electrochemical devices, high-specific-capacity electrode materials are required. Silicon-based materials, as a type of alloyed anode material, can provide an ultra-high specific capacity of up to 4200 mAh / g, making them a highly promising material for improving energy density. However, lithiation of silicon-based materials forms lithium-silicon alloys, which are highly reactive and readily attack solvent molecules in the electrolyte, leading to rapid electrolyte consumption and loss of active lithium. This results in poor cycle performance and poor high-temperature storage performance of the electrochemical device. Summary of the Invention

[0004] The purpose of this application is to provide an electrochemical device and an electronic device to improve the long-term cycling stability and high-temperature storage performance of the electrochemical device.

[0005] A first aspect of this application provides an electrochemical device comprising a negative electrode and an electrolyte, wherein;

[0006] The negative electrode sheet includes a negative electrode material layer, which includes silicon-based material, which includes silicon element. Based on the total mass of the negative electrode material layer, the mass percentage of silicon element is 30% to 60%.

[0007] The electrolyte comprises a compound of formula I and fluoroethylene carbonate:

[0008]

[0009] R1 and R2 are each independently selected from substituted or unsubstituted C1 to C5 alkyl groups, and substituted or unsubstituted C6 to C5 alkyl groups. 10The aryl group; when substituted, the substituent in the alkyl or aryl group is a fluorine atom, and A is selected from carbon-carbon double bonds, carbon-carbon triple bonds, or nitrogen-nitrogen double bonds. The mass percentage of silicon in the negative electrode material layer is within the above range, and the electrolyte includes a compound of formula I and fluoroethylene carbonate. The compound of formula I is used as a pre-film-forming additive in combination with fluoroethylene carbonate. Through the interfacial film-forming properties of fluoroethylene carbonate, the electrolyte is protected to a certain extent from continuous decomposition at the interface, and the consumption rate of fluoroethylene carbonate is reduced by the compound of formula I, thereby simultaneously improving the long-term cycle stability and high-temperature storage performance of the electrochemical device.

[0010] In one embodiment of this application, the mass percentage of fluoroethylene carbonate is 1% to 30% based on the total mass of the electrolyte. Controlling the mass percentage of fluoroethylene carbonate within the above range enables the FEC to better meet the consumption requirements of long-term cycling, thereby improving the long-term cycling stability of the electrochemical device and also improving the high-temperature storage performance of the electrochemical device.

[0011] In one embodiment of this application, the mass percentage of fluoroethylene carbonate is 10% to 30% based on the total mass of the electrolyte. Controlling the mass percentage of fluoroethylene carbonate within the above range enables the FEC to better meet the consumption requirements of long-term cycling, further improving the long-term cycling stability and high-temperature storage performance of the electrochemical device.

[0012] In one embodiment of this application, the electrolyte further includes a first component, the first component comprising C2 to C3. 10 Linear carbonates or C2 to C 10 At least one of the linear carboxylic acid esters; C2 to C 10 Linear carbonates include at least one of dimethyl carbonate, diethyl carbonate, or dipropyl carbonate; C2 to C 10 The linear carboxylic acid esters include at least one selected from propyl acetate, butyl acetate, ethyl propionate, propyl propionate, butyl propionate, ethyl butyrate, propyl butyrate, butyl butyrate, ethyl isobutyrate, propyl isobutyrate, butyl isobutyrate, or isobutyl isobutyrate; based on the total mass of the electrolyte, the mass percentage of the first component is 20% to 60%. Linear carbonates or linear carboxylic acid esters have low viscosity; by adding them as co-solvents to the electrolyte and controlling their mass percentage within the scope of this application, the overall ionic conductivity of the electrolyte can be improved, thereby enhancing the long-term cycle stability and high-temperature storage performance of the electrochemical device.

[0013] In one embodiment of this application, the electrolyte further includes a dinitrile compound, which includes at least one selected from succinic anionyl nitrile, glutaronitrile, methylglutaronitrile, adiponitrile, heptacyanide, caprylyl nitrile, azelaic anionyl nitrile, or sebacate; the mass percentage of the dinitrile compound is 0.1% to 3% based on the total mass of the electrolyte. Controlling the mass percentage of the dinitrile compound within the above range can significantly improve the stability of the electrochemical interface film, reduce the reactivity of the positive electrode active material, thereby reducing the possibility of excessive electrolyte consumption, thus improving the stability of the positive electrode side of the electrochemical device, and improving the long-term cycle stability and high-temperature storage performance of the electrochemical device.

[0014] In one embodiment of this application, the electrolyte further includes a lithium salt additive, which includes at least one of lithium tetrafluoroborate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, or lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide; the mass percentage of the lithium salt additive is 0.1% to 5% based on the total mass of the electrolyte. Selecting the above-mentioned boron-containing lithium salt and / or phosphorus-containing lithium salt and controlling the mass percentage of the lithium salt additive within the above range is beneficial for the compound of Formula I to form a synergistic effect with the boron-containing lithium salt and / or phosphorus-containing lithium salt, resulting in a more stable protective SEI film, thereby effectively inhibiting the continuous decomposition of the electrolyte, and thus improving the long-term cycle stability and high-temperature storage performance of the electrochemical device.

[0015] In one embodiment of this application, the mass percentage of compound I is 0.01% to 5% based on the total mass of the electrolyte. By controlling the mass percentage of compound I within the above range, the integrity of the pre-formed film layer formed by compound I can be improved, and the problem of hindered ion transport at the interface of the electrochemical device can be mitigated, thereby improving the long-term cycle stability and high-temperature storage performance of the electrochemical device.

[0016] In one embodiment of this application, the compound of formula I includes at least one of the following compounds:

[0017]

[0018]

[0019] By selecting the above-mentioned compound of formula I, it is beneficial to further enhance the film-forming stability and flexibility of the formed protective SEI film, thereby further reducing the side reactions between the electrolyte and the negative electrode active material, and thus improving the long-term cycle stability of the electrochemical device.

[0020] In one embodiment of this application, the silicon-based material includes at least one of a silicon-oxygen composite material or a silicon-carbon composite material. The surface of the silicon-oxygen composite material or silicon-carbon composite material particles contains inorganic material, including at least one of LiF, NaF, KF, MgF2, CaF2, or AlF3. Based on the total mass of the silicon-based material, the mass percentage of the inorganic material is 0.1% to 2%. By selecting the above materials, particle stability is improved, thereby further buffering the volume expansion of silicon during the electrochemical process, and further enhancing the long-term cycling stability and expansion performance of the electrochemical device.

[0021] The second aspect of this application provides an electronic device that includes the electrochemical device provided in the first aspect of this application. Because the electrochemical device provided in this application has good long-term cycle stability and high-temperature storage performance, the electronic device provided in this application has a long service life.

[0022] The beneficial effects of this application are:

[0023] This application provides an electrochemical device whose electrolyte comprises a compound of formula I and FEC, wherein the compound of formula I includes unsaturated bonds, and the unsaturated bonds have a preferential decomposition characteristic due to their decomposition potential being earlier than that of FEC, enabling the pre-formation of a layer containing LiN. x O y The protective SEI film, and LiN x O y The stability and rapid ion transport characteristics of FEC can improve the stability of SEI film, thereby reducing the consumption rate of FEC. This improves the problem of long-term cycle stability and high-temperature storage performance of electrochemical devices when silicon-based materials are used as negative electrode active materials, which is caused by excessive or insufficient FEC content.

[0024] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Detailed Implementation

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

[0026] It should be noted that, in the specific embodiments of this application, lithium-ion batteries are used as an example of electrochemical devices to explain this application. However, the electrochemical devices of this application are not limited to lithium-ion batteries. There are no particular limitations on the electrochemical devices of this application, and they may include any device in which an electrochemical reaction occurs.

[0027] To address the problem of rapid electrolyte consumption in electrochemical devices containing silicon-based materials, existing technologies typically add fluoroethylene carbonate (FEC), which serves as an excellent film-forming additive to repair damage to the solid electrolyte interface (SEI) film on the surface of silicon particles. However, FEC is consumed rapidly, and excessive addition of FEC can lead to poor high-temperature performance of the electrochemical device.

[0028] This application provides an electrochemical device and an electronic device. The electrochemical device includes a pre-film additive that pre-stabilizes the SEI film, reduces the damage to the SEI film on the silicon particle surface, thereby reducing the consumption of FEC and improving the long-term cycling stability of the electrochemical device.

[0029] A first aspect of this application provides an electrochemical device comprising a negative electrode and an electrolyte, wherein;

[0030] The negative electrode includes a negative electrode material layer, which includes a silicon-based material, which includes silicon element. Based on the total mass of the negative electrode material layer, the mass percentage of silicon element is 30% to 60%. For example, the mass percentage of silicon element can be 30%, 33%, 35%, 37%, 40%, 43%, 45%, 47%, 50%, 53%, 55%, 57%, 60%, or a range of any two of the above values.

[0031] The electrolyte comprises a compound of formula I and fluoroethylene carbonate:

[0032]

[0033] R1 and R2 are each independently selected from substituted or unsubstituted C1 to C5 alkyl groups, and substituted or unsubstituted C6 to C5 alkyl groups. 10 The aryl group; when substituted, the substituent in the alkyl or aryl group is a fluorine atom, and A is selected from a carbon-carbon double bond, a carbon-carbon triple bond, or a nitrogen-nitrogen double bond. In this application, the C1 to C5 alkyl groups can be methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, or pentyl. C6 to C 10 The aryl group can be phenyl or benzyl.

[0034] By controlling the mass percentage of silicon within the aforementioned range, sufficient space can be provided for the expansion of nano-silicon particles during the charging and discharging processes of the electrochemical device. This effectively alleviates phenomena such as material cracking caused by the expansion of nano-silicon particles, thereby improving the energy density and long-term cycle stability of the electrochemical device. However, in electrochemical devices containing silicon-based materials, the lithium-silicon alloy formed after the lithiation of silicon-based materials has highly reactive properties, leading to rapid consumption of the electrolyte and affecting the cycle performance and high-temperature storage performance of the electrochemical device. To alleviate the aforementioned problems, the inventors discovered that by selecting compound I, which contains unsaturated bonds and thus exhibits preferential decomposition characteristics, the decomposition potential of compound I is earlier than that of FEC. Therefore, compound I can pre-form a protective SEI film, reducing the consumption rate of FEC. Furthermore, compound I also contains carboxylic acid ester functional groups, which have good ion conductivity, thus improving the ion transport performance of the negative electrode side surface. Therefore, the inventors selected compound I as a pre-film-forming additive to combine with fluoroethylene carbonate. Through the interfacial film-forming characteristics of fluoroethylene carbonate, the electrolyte is protected to a certain extent from continuous decomposition at the interface, and compound I reduces the consumption rate of fluoroethylene carbonate, thereby simultaneously improving the long-term cycle stability and high-temperature storage performance of the electrochemical device.

[0035] In one embodiment of this application, the mass percentage of fluoroethylene carbonate is 1% to 30% based on the total mass of the electrolyte; for example, the mass percentage of fluoroethylene carbonate can be 1%, 3%, 5%, 7%, 10%, 13%, 15%, 17%, 20%, 23%, 25%, 27%, 30%, or a range of any two of these values. Controlling the mass percentage of fluoroethylene carbonate within the above range allows the FEC to better meet the consumption requirements of long-term cycling, thereby improving the long-term cycling stability of the electrochemical device and also improving the high-temperature storage performance of the electrochemical device.

[0036] In one embodiment of this application, the mass percentage of fluoroethylene carbonate is 10% to 30% based on the total mass of the electrolyte. Controlling the mass percentage of fluoroethylene carbonate within the above range enables the FEC to better meet the consumption requirements of long-term cycling, further improving the long-term cycling stability and high-temperature storage performance of the electrochemical device.

[0037] In one embodiment of this application, the electrolyte further includes a first component, the first component comprising C2 to C3. 10 Linear carbonates or C2 to C 10 At least one of the linear carboxylic acid esters; C2 to C 10 Linear carbonates include at least one of dimethyl carbonate, diethyl carbonate, or dipropyl carbonate; C2 to C 10The linear carboxylic acid esters include at least one selected from propyl acetate, butyl acetate, ethyl propionate, propyl propionate, butyl propionate, ethyl butyrate, propyl butyrate, butyl butyrate, ethyl isobutyrate, propyl isobutyrate, butyl isobutyrate, or isobutyl isobutyrate; the mass percentage of the first component is 20% to 60% based on the total mass of the electrolyte. For example, the mass percentage of the first component can be 20%, 23%, 25%, 27%, 30%, 33%, 35%, 37%, 40%, 43%, 45%, 47%, 50%, 53%, 55%, 57%, 60%, or a range consisting of any two of these values. Linear carbonates or linear carboxylic acid esters have the characteristic of low viscosity. By adding them as co-solvents to the electrolyte and controlling their mass percentage within the scope of this application, the overall ionic conductivity of the electrolyte can be improved, thereby improving the long-term cycle stability and high-temperature storage performance of the electrochemical device.

[0038] In one embodiment of this application, the first component comprises C2 to C3. 10 The linear carbonate, based on the total mass of the electrolyte, has a mass percentage content of 20% to 60%. If the electrolyte includes the aforementioned first component, the electrochemical device exhibits good long-term cycling stability and high-temperature storage performance.

[0039] In one embodiment of this application, the first component comprises C2 to C3. 10 The linear carboxylic acid esters, based on the total mass of the electrolyte, have a mass percentage content of 20% to 60%. If the electrolyte includes the aforementioned first component, the electrochemical device exhibits good long-term cycling stability and high-temperature storage performance.

[0040] In one embodiment of this application, the first component comprises C2 to C3. 10 Linear carbonates and C2 to C 10 For linear carboxylic acid esters, there are no particular restrictions on the mass percentage of each component, as long as the total mass percentage of the first component meets the scope of this application.

[0041] In one embodiment of this application, the electrolyte further includes a dinitrile compound, which includes at least one selected from succinic anionyl nitrile, glutaronitrile, methylglutaronitrile, adiponitrile, heptacyanide, caprylyl nitrile, azelaic anionyl nitrile, or sebacate; the mass percentage of the dinitrile compound is 0.1% to 3% based on the total mass of the electrolyte. For example, the mass percentage of the dinitrile compound can be 0.1%, 1%, 1.5%, 2%, 2.5%, 3%, or a range consisting of any two of these values. Controlling the mass percentage of the dinitrile compound within the above range can significantly improve the stability of the chemical-electrochemical interface (CEI), reduce the reactivity of the positive electrode active material, thereby reducing the possibility of excessive electrolyte consumption, thus improving the stability of the positive electrode side of the electrochemical device, and improving the long-term cycle stability and high-temperature storage performance of the electrochemical device.

[0042] In one embodiment of this application, the electrolyte further includes a lithium salt additive, which includes at least one of lithium tetrafluoroborate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, or lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide. Based on the total mass of the electrolyte, the mass percentage of the lithium salt additive is 0.1% to 5%. For example, the mass percentage of the lithium salt additive can be 0.1%, 1%, 2%, 3%, 4%, 5%, or a range consisting of any two of these values. Selecting the aforementioned boron-containing lithium salt and / or phosphorus-containing lithium salt and controlling the mass percentage of the lithium salt additive within the above range is beneficial for the compound of Formula I to form a synergistic effect with the boron-containing lithium salt and / or phosphorus-containing lithium salt, resulting in a more stable protective SEI film, thereby effectively inhibiting the continuous decomposition of the electrolyte and improving the long-term cycle stability and high-temperature storage performance of the electrochemical device.

[0043] In one embodiment of this application, the mass percentage of compound I is 0.01% to 5% based on the total mass of the electrolyte; for example, the mass percentage of compound I can be 0.01%, 0.5%, 1%, 2%, 3%, 4%, 5%, or a range consisting of any two of these values. By controlling the mass percentage of compound I within the above range, the integrity of the pre-formed film layer formed by compound I can be improved, and the problem of impeded ion transport at the electrochemical device interface can be mitigated, thereby enhancing the long-term cycle stability and high-temperature storage performance of the electrochemical device.

[0044] In one embodiment of this application, the compound of formula I includes at least one of the following compounds:

[0045]

[0046] By selecting the above-mentioned compound of formula I, it is beneficial to further enhance the film-forming stability and flexibility of the formed protective SEI film, thereby further reducing the side reactions between the electrolyte and the negative electrode active material, and thus improving the long-term cycle stability of the electrochemical device.

[0047] In this application, the characteristics of the different components contained in the electrolyte can be combined, and the implementation methods covered by the above combinations are all within the protection scope of this application.

[0048] In this application, the electrolyte also includes lithium salts and other basic solvents. This application does not particularly limit the type of lithium salt; lithium salts known in the art can be used. Exemplarily, the lithium salt may include, but is not limited to, at least one of LiPF6, LiAsF6, LiClO4, LiB(C6H5)4, or LiCH3SO3. This application does not particularly limit other basic solvents, as long as they can achieve the purpose of this application. For example, other basic solvents may include at least one of non-fluorinated cyclic carbonates, ether compounds, other linear carbonates, other linear carboxylic acid esters, or other organic solvents; 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, ethoxymethoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran; the aforementioned other linear carbonates include at least one of methyl ethyl carbonate, methyl propyl carbonate (MPC), or ethyl propyl carbonate (EPC). The aforementioned non-fluorinated cyclic carbonates may include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or vinyl ethylene carbonate (VEC). Other linear carboxylic acid esters include, but are not limited to, at least one of ethyl acetate, tert-butyl acetate, methyl propionate, methyl tert-butyrate, ethyl tert-butyrate, 2,2-difluoroethyl acetate, 2,2,2-trifluoroethyl acetate, hexafluoroisopropyl acetate, 2,2-difluoroethyl propionate, 2,2,2-trifluoroethyl propionate, or hexafluoroisopropyl propionate. Other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or phosphate esters. This application does not impose any particular limitation on the mass percentage of lithium salt and other basic solvents in the electrolyte, as long as the purpose of this application can be achieved. For example, based on the total mass of the electrolyte, the mass percentage of lithium salt can be 8% to 20%, and the mass percentage of other basic solvents can be 0% to 90%.

[0049] The electrolyte may include a compound of formula I, FEC, lithium salt, and other basic solvents; the mass percentages of the compound of formula I, FEC, and lithium salt are as described above, and the mass percentages of other basic solvents are 45% to 90% based on the mass of the electrolyte. Electrochemical devices incorporating the above electrolytes also exhibit good long-term cycling stability and high-temperature storage performance.

[0050] The electrolyte may include a compound of formula I, FEC, lithium salt, dinitrile compound, and other basic solvents; the mass percentages of the compound of formula I, FEC, lithium salt, and dinitrile compound are as described above, and the mass percentages of other basic solvents are 42% to 90% based on the mass of the electrolyte. Electrochemical devices incorporating the above electrolytes also exhibit good long-term cycling stability and high-temperature storage performance.

[0051] The electrolyte may include a compound of formula I, FEC, lithium salt, lithium salt additive, and other base solvents; the mass percentages of the compound of formula I, FEC, lithium salt, and lithium salt additive are as described above, and the mass percentages of other base solvents are 40% to 90% based on the mass of the electrolyte. Electrochemical devices incorporating the above electrolytes also exhibit good long-term cycling stability and high-temperature storage performance.

[0052] The electrolyte may include a compound of formula I, FEC, lithium salt, dinitrile compound, lithium salt additive, and other basic solvents; the mass percentages of the compound of formula I, FEC, lithium salt, dinitrile compound, and lithium salt additive are as described above, and the mass percentages of other basic solvents are 37% to 90% based on the mass of the electrolyte. Electrochemical devices incorporating the above electrolytes also exhibit good long-term cycling stability and high-temperature storage performance.

[0053] In one embodiment of this application, the electrolyte may include a compound of formula I, FEC, lithium salt, a first component, and other base solvents; the mass percentages of the compound of formula I, FEC, lithium salt, and the first component are as described above, and the mass percentages of the other base solvents are 0% to 70% based on the mass of the electrolyte. The electrochemical device including the above-described electrolyte also exhibits good long-term cycling stability and high-temperature storage performance.

[0054] In one embodiment of this application, the electrolyte may include a compound of formula I, FEC, lithium salt, dinitrile compound, a first component, and other basic solvents; the mass percentages of the compound of formula I, FEC, lithium salt, dinitrile compound, and first component are as described above, and the mass percentages of other basic solvents are 0% to 70% based on the mass of the electrolyte. The electrochemical device including the above-described electrolyte also exhibits good long-term cycling stability and high-temperature storage performance.

[0055] In one embodiment of this application, the electrolyte may include a compound of formula I, FEC, lithium salt, lithium salt additive, a first component, and other base solvents; the mass percentages of the compound of formula I, FEC, lithium salt, lithium salt additive, and the first component are as described above, and the mass percentages of the other base solvents are 0% to 70% based on the mass of the electrolyte. The electrochemical device including the above-described electrolyte also exhibits good long-term cycling stability and high-temperature storage performance.

[0056] In one embodiment of this application, the electrolyte may include a compound of formula I, FEC, lithium salt, dinitrile compound, lithium salt additive, a first component, and other basic solvents; the mass percentages of the compound of formula I, FEC, lithium salt, dinitrile compound, lithium salt additive, and the first component are as described above, and the mass percentage of other basic solvents is 0% to 70% based on the mass of the electrolyte. The electrochemical device including the above-described electrolyte also exhibits good long-term cycling stability and high-temperature storage performance.

[0057] In this application, the electrochemical device further includes a negative electrode sheet, which 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 aforementioned "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 its thickness direction, or on two surfaces of the negative electrode current collector along its thickness direction. It should be noted that the "surface" here can be the entire area of ​​the negative electrode current collector or only a portion thereof; this application does not have any particular limitation, as long as the purpose of this application is achieved.

[0058] In one embodiment of this application, the negative electrode material layer comprises a silicon-based material, wherein the mass percentage of silicon element is 5% to 65% based on the mass of the silicon-based material; for example, the mass percentage of silicon element can be 5%, 13%, 15%, 17%, 20%, 23%, 25%, 27%, 30%, 33%, 35%, 37%, 40%, 43%, 45%, 47%, 50%, 53%, 55%, 57%, 60%, 63%, 65%, or a range of any two of these values. Controlling the mass percentage of silicon element within the above range ensures sufficient space for the expansion of the nano-silicon particles during the charging and discharging processes of the electrochemical device. This effectively mitigates material cracking caused by the expansion of the nano-silicon particles, improves the energy density of the electrochemical device, and further enhances its long-term cycle stability and high-temperature storage performance.

[0059] In one embodiment of this application, the silicon-based material includes at least one of a silicon-oxygen composite material or a silicon-carbon composite material. The surface of the silicon-oxygen composite material or silicon-carbon composite material particles contains inorganic material, including at least one of LiF, NaF, KF, MgF2, CaF2, or AlF3. Based on the total mass of the silicon-based material, the mass percentage of the inorganic material is 0.1% to 2%. By selecting the above materials, particle stability is improved, thereby further buffering the volume expansion of silicon during the electrochemical process, and further enhancing the long-term cycling stability and expansion performance of the electrochemical device.

[0060] This application does not impose any particular limitation on the preparation method of silicon-oxygen composite materials or silicon-carbon composite materials. Exemplarily, the preparation method of silicon-based materials may include, but is not limited to, the following steps: adding silicon-containing substances and inorganic materials to an organic solvent in a certain mass ratio to form a suspension, mixing to obtain a mixture, filtering, and drying to obtain a silicon-oxygen composite material or a silicon-carbon composite material. This application does not impose any particular limitation on the organic solvent, as long as it can achieve the purpose of this application; for example, the organic solvent can be ethanol. This application does not impose any particular limitation on the silicon-containing substances, as long as it can achieve the purpose of this application; for example, the silicon-containing substances can be selected from at least one of the following: microporous carbon materials loaded with nano-silicon, silicon-oxygen materials, micron-sized silicon, Si-Sn alloys, Si-Mg alloys, Si-Ge alloys, or Si-Zn alloys.

[0061] This application does not impose any particular limitation on the negative electrode current collector, as long as it achieves the purpose of this application. For example, the negative electrode current collector may include, but is not limited to, copper foil, aluminum foil, nickel foil, or carbon-based current collectors, and the thickness of the negative electrode current collector may be 4 μm to 12 μm. 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 a single-sided negative electrode material layer may be 30 μm to 150 μm. This application does not impose any particular limitation on the thickness of the negative electrode sheet, as long as it achieves the purpose of this application, for example, the thickness of the negative electrode sheet may be 50 μm to 300 μm. The negative electrode material layer of this application may also include a conductive agent and a binder.

[0062] The negative electrode material layer of this application includes a negative electrode active material, which may further include carbon material. The carbon material may be selected from at least one of natural graphite, artificial graphite, mesophase microcarbon spheres, hard carbon, and soft carbon. Based on the total mass of the negative electrode material layer, the mass percentage of carbon material may be from 10% to 70%.

[0063] The conductive agent and binder described above are not particularly limited, as long as they can achieve the purpose of this application. For example, the conductive agent may include at least one of conductive carbon black, sheet graphite, graphene, carbon nanotubes, carbon nanowires, or carbon fibers. The conductive carbon black may include at least one of acetylene black and Ketjen black. The binder may include at least one of lithium polyacrylate, polyvinylidene fluoride (PVDF), PVDF-hexafluoropropylene copolymer, styrene-acrylate copolymer, styrene-butadiene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose (CMC-Na), polyvinyl acetate, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyaniline, polyimide, polyamide-imide, polysiloxane, epoxy resin, polyester resin, polyurethane resin, or polyfluorene.

[0064] Optionally, the negative electrode sheet may further include a conductive layer, which is 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, and it can be a 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, and it can be at least one of the aforementioned conductive agents and binders. This application does not impose any particular limitation on the mass ratio of the conductive agent to the binder in the conductive layer; those skilled in the art can choose according to actual needs, as long as the purpose of this application is achieved. This application does not impose any particular limitation on the thickness of the conductive layer, as long as the purpose of this application is achieved; for example, the thickness of the conductive layer is 1 μm to 10 μm.

[0065] The electrochemical device of this application also includes a positive electrode and a separator.

[0066] In this application, the electrochemical device further includes a positive electrode sheet, which comprises a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The aforementioned "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 the "surface" here can be the entire area of ​​the positive current collector or only a portion thereof; this application does not have any particular limitation, as long as the purpose of this application is achieved. This application does not have any particular limitation on the positive current collector, as long as the purpose of this application is achieved; for example, it can include aluminum foil, aluminum alloy foil, or a composite current collector (e.g., an aluminum-carbon composite current collector), etc.

[0067] The cathode material layer of this application includes a cathode active material, which comprises a substance capable of reversibly inserting and extracting active ions such as lithium ions. The cathode material layer can be one or more layers, and each layer in a multilayer cathode material layer can contain the same or different cathode active materials. This application does not impose any particular limitation on the cathode active material, as long as it can achieve the purpose of this application. For example, the cathode active material can include, but is not limited to, at least one of 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. The cathode material layer of this application also includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the cathode material layer, as long as it can achieve the purpose of this application. For example, the conductive agent in the cathode material layer can include, but is not limited to, at least one of conductive carbon black, carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metallic materials, or conductive polymers. The aforementioned conductive carbon black may include, but is not limited to, Super P, 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 polymer may include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. The binder in the positive electrode material layer may include, but is not limited to, at least one of polyacrylate, polyimide, polyamide, polyamide-imide, polyvinylidene fluoride, polystyrene-butadiene copolymer (styrene-butadiene rubber, SBR), sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose (CMC-Na), potassium carboxymethyl cellulose, sodium carboxymethyl cellulose, or potassium carboxymethyl cellulose. This application does not impose any particular limitation 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 can be achieved.

[0068] This application does not impose any particular limitation on the thickness of the positive electrode current collector, as long as it achieves the purpose of this application. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm, preferably 6 μm to 18 μm. This application also does not impose any particular limitation on the thickness of the positive electrode material layer, as long as it achieves the purpose of this application. For example, the thickness of a single-sided positive electrode material layer is 30 μm to 120 μm.

[0069] This application does not impose any particular limitation on the separator membrane, as long as it achieves the purpose of this application. For example, the separator membrane may include at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. Polyethylene and polypropylene can prevent short circuits and can also improve the stability of the electrochemical device through a turn-off effect. For example, polyethylene may include at least one of high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene. The surface of the separator membrane may include a porous layer disposed on at least one surface of the separator membrane. The porous layer may include at least one of inorganic particles or a binder. The porous layer can improve the heat resistance, oxidation resistance, and electrolyte wetting performance of the separator membrane, and enhance the adhesion between the separator membrane and the electrode. The pore size is not particularly limited, as long as it achieves the purpose of this application. For example, the pore size may be from 0.01 μm to 1 μm. In this application, the thickness of the separator membrane may be from 5 μm to 30 μm. This application does not impose any particular limitation on the aforementioned inorganic particles, as long as they can achieve the purpose of this application. For example, the inorganic particles may include at least one of the following: alumina (Al2O3), silicon dioxide (SiO), magnesium oxide (MgO), titanium dioxide (TiO2), hafnium dioxide (HfO2), tin oxide (SnO2), cerium dioxide (CeO2), nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. For example, the binder of the porous layer may include at least one of the following: polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene.

[0070] The preparation process of electrochemical devices is well known to those skilled in the art, and this application does not impose any particular limitations. For example, it may include, but is not limited to, the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain the electrochemical device; or stacking the positive electrode, separator, and negative electrode 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 in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain the electrochemical device. Furthermore, overcurrent protection elements, conductive plates, etc., may be placed in the packaging bag as needed to prevent pressure rise and overcharging / discharging inside the electrochemical device. This application does not limit the packaging bag; those skilled in the art can choose one according to actual needs, as long as it achieves the purpose of this application. For example, an aluminum-plastic film packaging bag may be used.

[0071] The second aspect of this application provides an electronic device that includes the electrochemical device provided in the first aspect of this application. Because the electrochemical device provided in this application has good long-term cycle stability and high-temperature storage performance, the electronic device provided in this application has a long service life.

[0072] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, 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, household large-capacity batteries or lithium-ion capacitors, etc.

[0073] Example

[0074] 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.

[0075] Test methods and equipment:

[0076] Long-term cycling stability test:

[0077] The long-term cycle stability of lithium-ion batteries is evaluated by the cycle capacity retention rate. The lithium-ion battery is placed in a 25°C constant-temperature test chamber and allowed to stand for 30 minutes to reach a constant temperature. It is then charged at a constant current of 0.5C to 4.45V, followed by constant-voltage charging to 0.025C. After standing for 5 minutes, it is discharged at a constant current of 0.5C to 3.0V, and this initial discharge capacity is recorded as C1. This process is repeated for 200 cycles, and the discharge capacity C2 after 200 cycles is recorded. The cycle capacity retention rate of the lithium-ion battery is then calculated.

[0078] Cyclic capacity retention rate = C2 / C1 × 100%.

[0079] High-temperature storage performance test:

[0080] The high-temperature storage performance of lithium-ion batteries was evaluated by the storage expansion rate. The lithium-ion batteries were charged at a constant current of 4C to the upper limit voltage of 4.45V at 25℃, and then charged at a constant voltage of 0.025C at 4.45V, and the initial thickness L1 was recorded. The batteries were then placed in an 85℃ oven for 12 hours, and the thickness L2 of the lithium-ion batteries was measured again.

[0081] The storage expansion rate at 85℃ is T = (L2-L1) / L1×100%. T represents the high-temperature storage performance; the smaller the T value, the better the high-temperature storage performance.

[0082] Test for silicon elemental mass percentage:

[0083] 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℃ for 12 hours to obtain the negative electrode sheet. The negative electrode sheet was then placed in a vacuum oven and dried at 100℃ for 24 hours. One gram of powdered negative electrode material layer was scraped off the negative electrode sheet with a blade, and the mass percentage of silicon in the negative electrode material layer was determined using an ICP (Inductively Coupled Plasma) analyzer.

[0084] Example 1-1

[0085] <Preparation of the positive electrode>

[0086] Lithium cobalt oxide, conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 95:2.5:2.5. N-methylpyrrolidone (NMP) was then added as a solvent to prepare a positive electrode slurry with a solid content of 75 wt%, and the mixture was stirred thoroughly. The positive electrode slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil used as a positive electrode current collector, and dried at 90°C to obtain a positive electrode sheet with a coating thickness of 110 μm. This completes the single-sided coating of the positive electrode sheet. The above steps were then repeated on the other surface of the positive electrode sheet to obtain a double-sided coated positive electrode sheet. After coating, the positive electrode sheet was cold-pressed, cut into 74 mm × 867 mm dimensions, and electrode tabs were welded on. The thickness of the single-sided positive electrode layer after cold pressing was 75 μm, and the compaction density of the positive electrode layer was 4 g / cm³. 3 .

[0087] <Preparation of Silicon-Carbon Composite Materials>

[0088] Microporous carbon material loaded with nano-silicon was added to an ethanol solution at a mass ratio of 99:1 to form a suspension. The suspension was then ball-milled and mixed to ensure uniform dispersion. After filtration and drying, a silicon-carbon composite material with LiF on its surface was obtained. The microporous carbon material loaded with nano-silicon contained 50% carbon; the mass percentage of LiF was 1% based on the total mass of the silicon-based material.

[0089] <Preparation of Negative Electrode Sheets>

[0090] Silicon-carbon composite material, artificial graphite, carbon nanotubes, and lithium polyacrylate were mixed in a mass ratio of 80:10:2:8. 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 used as a negative electrode current collector and dried at 120°C to obtain a negative electrode sheet with a single-sided coating 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 of 143 μm. After cold pressing and slitting, a negative electrode sheet with a size of 78 mm × 875 mm was obtained. The silicon content was 39.6% by mass based on the mass of the negative electrode material layer. The thickness of the single-sided negative electrode material layer after cold pressing was 80 μm, and the compaction density of the negative electrode material layer was 1 g / cm³. 3 .

[0091] <Preparation of Electrolyte>

[0092] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate, methyl ethyl carbonate, and ethyl acetate were mixed in a mass ratio of 3:3:4 to obtain a base solvent. Then, lithium hexafluorophosphate (LiPF6), fluoroethylene carbonate, and compound I-1 were added and mixed thoroughly to obtain the electrolyte. Based on the total mass of the electrolyte, the mass percentages of lithium hexafluorophosphate were 12.5%, fluoroethylene carbonate 20%, and compound I-1 5%, with the remainder being the base solvent.

[0093] <Preparation of the separating membrane>

[0094] A 15μm thick polyethylene (PE) film (supplied by Celgard) was used.

[0095] <Preparation of Lithium-ion Batteries>

[0096] The negative electrode, separator, and positive electrode prepared above are stacked in sequence, with the separator positioned between the positive and negative electrode to provide isolation. The electrode assembly is then wound to obtain the electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, degassing, and edge trimming, a lithium-ion battery is obtained.

[0097] Examples 1-2 to Examples 1-6

[0098] Except for adjusting the mass percentage parameters of compound I and fluoroethylene carbonate according to Table 1 in the <Preparation of Electrolyte>, changing the mass percentage of the base solvent accordingly, keeping the mass ratio of each component of the base solvent unchanged, and keeping the mass percentage of LiPF6 unchanged, the rest is the same as in Example 1-1.

[0099] Examples 1-7 to Examples 1-8

[0100] Except for adjusting the silicon content ratio in the silicon-carbon composite material and / or the mass ratio of the silicon-carbon composite material to artificial graphite in the <Preparation of Negative Electrode Sheet> so that the mass percentage of silicon in the negative electrode material layer is as shown in Table 1, and keeping the mass of carbon nanotubes, lithium polyacrylate and negative electrode material layer unchanged, the rest is the same as in Examples 1-2.

[0101] Examples 1-9 to Examples 1-11

[0102] Except for adjusting the types of compounds of Formula I according to Table 1 in <Preparation of Electrolyte>, the rest is the same as in Examples 1-2.

[0103] Examples 2-1 to 2-3

[0104] Except for the addition of dinitrile compounds according to Table 2 and adjustment of their mass percentage in the <Preparation of Electrolyte>, the mass percentage of the base solvent is changed accordingly, the mass ratio of each component of the base solvent remains unchanged, and the mass percentages of Formula I compound, FEC and LiPF6 remain unchanged, the rest is the same as in Examples 1-2.

[0105] Examples 3-1 to 3-3

[0106] Except for the addition of lithium salt additives according to Table 3 and adjustment of their mass percentage in <Electrolyte Preparation>, the mass percentage of the base solvent is changed accordingly, the mass ratio of each component of the base solvent remains unchanged, and the mass percentages of Formula I compound, FEC and LiPF6 remain unchanged, the rest is the same as in Examples 1-2.

[0107] Examples 4-1 to 4-6

[0108] Except for the addition of lithium salt additives and dinitrile compounds according to Table 4 in the <Preparation of Electrolyte> and the adjustment of their mass percentage, the mass percentage of the base solvent is changed accordingly, the mass ratio of each component of the base solvent remains unchanged, and the mass percentages of Formula I compound, FEC and LiPF6 remain unchanged, the rest is the same as in Examples 1-2.

[0109] Examples 5-1 to 5-5

[0110] Except for adjusting the types of inorganic materials present on the surface and their mass percentage content according to Table 5 in the <Preparation of Silicon-Carbon Composite Materials>, the rest is the same as in Example 1-1.

[0111] Example 6-1

[0112] Except for the preparation of the electrolyte as described below, the rest is the same as in Examples 1-1.

[0113] <Preparation of Electrolyte>

[0114] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate, methyl ethyl carbonate, and ethyl acetate were mixed in a mass ratio of 3:3:4 to obtain a base solvent. Then, lithium hexafluorophosphate (LiPF6), fluoroethylene carbonate, compound I-1, and diethyl carbonate (the first component) were added and mixed thoroughly to obtain the electrolyte. Based on the total mass of the electrolyte, the mass percentages of lithium hexafluorophosphate (LiPF6), fluoroethylene carbonate (20%), compound I (3%), and the first component (20%) were all determined, with the remainder being the base solvent.

[0115] Examples 6-2 to 6-9

[0116] Except for the addition of the first component according to Table 6 and adjustment of its mass percentage in the <Preparation of Electrolyte>, the mass percentage of the base solvent is changed accordingly, the mass ratio of ethylene carbonate, methyl ethyl carbonate and ethyl acetate remains unchanged, and the mass percentages of Formula I compound, FEC and LiPF6 remain unchanged, the rest is the same as in Example 6-1.

[0117] Comparative Examples 1-1 to 1-6

[0118] Except for adjusting the content parameters of compound I and fluoroethylene carbonate according to Table 1 in <Preparation of Electrolyte>, changing the mass percentage of the base solvent accordingly, keeping the mass ratio of each component of the base solvent unchanged, and keeping the mass percentage of LiPF6 unchanged, the rest is the same as in Examples 1-2.

[0119] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Tables 1 to 6.

[0120] Table 1

[0121]

[0122] Note: (1) “ / ” in Table 1 indicates that there is no corresponding preparation parameter, substance or performance parameter; (2) Taking Examples 1-10 as an example, “Compound Type of Formula I” is “Formula I-13+Formula I-17”, and “Mass Percentage of Formula I Compound” is “1+2”, indicating that Formula I compound includes Formula I-13 and Formula I-17. Based on the total mass of the electrolyte, the mass percentage of Formula I-13 is 1% and the mass percentage of Formula I-17 is 2%. Other examples follow the same principle.

[0123] As can be seen from Examples 1-1 to 1-11 and Comparative Examples 1-1 to 1-6, the types and mass percentages of Formula I compounds, the mass percentages of fluoroethylene carbonate, and the mass percentages of silicon in the examples are within the scope of this application, while the comparative examples do not simultaneously meet the above characteristics. In the examples of this application, the lithium-ion battery has a high capacity retention rate and a low storage expansion rate, indicating that the lithium-ion battery has better long-term cycle stability and high-temperature storage performance.

[0124] In electrolytes, the mass percentage of compound I typically affects the long-term cycle stability and high-temperature storage performance of electrochemical devices. As seen in Examples 1-1 to 1-3 and Comparative Examples 1-2 to 1-6, by adjusting the mass percentage of compound I within the range specified in this application, lithium-ion batteries exhibit higher capacity retention and lower storage expansion rates, indicating better long-term cycle stability and high-temperature storage performance. Conversely, when compound I is not present, such as in Comparative Examples 1-6, the lithium-ion battery exhibits a higher storage expansion rate, indicating poorer high-temperature storage performance.

[0125] In electrolytes, the mass percentage of FEC typically affects the long-term cycle stability and high-temperature storage performance of electrochemical devices. As seen in Examples 1-2, 1-4 to 1-6, and Comparative Examples 1-1 to 1-5, by adjusting the mass percentage of FEC within the range specified in this application, lithium-ion batteries can exhibit higher capacity retention and lower storage expansion rates, indicating better long-term cycle stability and high-temperature storage performance. When the electrolyte does not contain FEC, such as in Comparative Example 1-1, the capacity retention of the lithium-ion battery is lower, indicating poorer long-term cycle stability.

[0126] Table 2

[0127]

[0128] Note: Taking Example 2-2 as an example, the "type of dinitrile compound" is "octanoic acid + adiponitrile", and the "mass percentage of dinitrile compound" is "1 + 0.5", indicating that the dinitrile compound includes octanoic acid and adiponitrile. Based on the total mass of the electrolyte, the mass percentage of octanoic acid is 1%, and the mass percentage of adiponitrile is 0.5%. Other examples follow the same principle.

[0129] The type and mass percentage of dinitrile compounds typically affect the high-temperature storage performance of lithium-ion batteries. As can be seen from Examples 1-2, 2-1 to 2-3, when dinitrile compounds are further added to the electrolyte, and the type and content of these compounds are within the scope of this application, the resulting lithium-ion battery exhibits a lower storage expansion rate. For example, in Example 2-2, because the dinitrile compounds can significantly improve the stability of the CEI film and reduce the reactivity of the positive electrode active material, thereby reducing excessive electrolyte consumption, the high-temperature storage performance of the lithium-ion battery is further improved.

[0130] Table 3

[0131]

[0132] Note: Taking Example 3-2 as an example, the “type of lithium salt additive” is “lithium difluorophosphate + lithium bis(trifluoromethanesulfonyl)imide”, and the “mass percentage of lithium salt additive” is “1+1.5”, indicating that the lithium salt additive includes lithium difluorophosphate and lithium bis(trifluoromethanesulfonyl)imide. Based on the total mass of the electrolyte, the mass percentage of lithium difluorophosphate is 1%, and the mass percentage of lithium bis(trifluoromethanesulfonyl)imide is 1.5%. Other examples follow the same principle.

[0133] The type and mass percentage of lithium salt additives typically affect the high-temperature storage performance of lithium-ion batteries. As can be seen from Examples 1-2, 3-1 to 3-3, when lithium salt additives are further added to the electrolyte, and the type and content of the lithium salt additives are within the scope of this application, the resulting lithium-ion battery exhibits a lower storage expansion rate. For example, in Example 3-3, due to the synergistic effect of the Formula I compound with boron-containing lithium salts and / or phosphorus-containing lithium salts, a stable protective SEI film is obtained, thereby inhibiting the continuous decomposition of the electrolyte. This results in a lower storage expansion rate for the lithium-ion battery, indicating that the high-temperature storage performance of the lithium-ion battery is further improved.

[0134] Table 4

[0135]

[0136] Note: Taking Examples 4-5 as examples, "type of dinitrile compound" is "octanilide + adiponitrile", "mass percentage of dinitrile compound" is "1 + 0.5", "type of lithium salt additive" is "lithium difluorophosphate + lithium bis(trifluoromethanesulfonyl)imide", and "mass percentage of lithium salt additive" is "1 + 1.5", indicating that the dinitrile compound includes octanilide and adiponitrile, the lithium salt additive includes lithium difluorophosphate and lithium bis(trifluoromethanesulfonyl)imide, based on the total mass of the electrolyte, the mass percentage of octanilide is 1%, the mass percentage of adiponitrile is 0.5%, the mass percentage of lithium difluorophosphate is 1%, and the mass percentage of lithium bis(trifluoromethanesulfonyl)imide is 1.5%, and other examples follow the same principle.

[0137] As can be seen from Examples 1-2 and Examples 4-1 to 4-6, by simultaneously adding dinitrile compounds and lithium salt additives to the electrolyte, and when their types and mass percentages are within the scope of this application, the lithium-ion battery has a high cycle capacity retention rate and a low storage expansion rate, indicating that the long-term cycle stability and high-temperature storage performance of the lithium-ion battery are further improved.

[0138] Table 5

[0139]

[0140] Note: Taking Example 5-3 as an example, "the type of inorganic material present on the surface of silicon-based material particles" is "NaF+MgF2", and "the mass percentage of inorganic material" is "0.4+0.5", indicating that the inorganic material present on the surface of silicon-based material particles includes NaF and MgF2. Based on the total mass of silicon-based material, the mass percentage of NaF is 0.4% and the mass percentage of MgF2 is 0.5%. Other examples follow the same principle.

[0141] From Examples 1-1, 5-1 to 5-5, it can be concluded that the presence of the aforementioned inorganic materials on the surface of silicon-based materials results in lithium-ion batteries exhibiting high capacity retention and storage expansion rates, indicating that the cycle stability and high-temperature storage performance of lithium-ion batteries are further improved.

[0142] Table 6

[0143]

[0144]

[0145] The composition and content of the first component typically affect the long-term cycle stability and high-temperature storage performance of lithium-ion batteries. As can be seen from Examples 6-1 to 6-9, when the composition and content of the first component are within the scope of this application, the lithium-ion battery exhibits good long-term cycle stability and high-temperature storage performance.

[0146] 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 inherent to such process, method, or article.

[0147] The various embodiments in this specification are described in a related manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0148] The above are merely preferred embodiments of this application and are 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. An electrochemical device comprising a negative electrode and an electrolyte, wherein; The negative electrode sheet includes a negative electrode material layer, the negative electrode material layer includes a silicon-based material, the silicon-based material includes silicon element, and based on the total mass of the negative electrode material layer, the mass percentage content of the silicon element is 30% to 60%. The electrolyte comprises a compound of formula I and fluoroethylene carbonate: in, R1 and R2 are each independently selected from substituted or unsubstituted C1 to C5 alkyl groups, and substituted or unsubstituted C6 to C5 alkyl groups. 10 The aryl group; when substituted, the substituent in the alkyl or aryl group is a fluorine atom, and A is selected from carbon-carbon double bond, carbon-carbon triple bond or nitrogen-nitrogen double bond.

2. The electrochemical device according to claim 1, wherein, Based on the total mass of the electrolyte, the mass percentage of the fluoroethylene carbonate is between 1% and 30%.

3. The electrochemical device according to claim 1, wherein, Based on the total mass of the electrolyte, the mass percentage of the fluoroethylene carbonate is 10% to 30%.

4. The electrochemical device according to claim 1, wherein, The electrolyte further includes a first component, the first component comprising C2 to C3. 10 Linear carbonates or C2 to C 10 At least one of the linear carboxylic acid esters; C2 to C 10 Linear carbonates include at least one of dimethyl carbonate, diethyl carbonate, or dipropyl carbonate. C2 to C 10 The linear carboxylic acid esters include at least one of propyl acetate, butyl acetate, ethyl propionate, propyl propionate, butyl propionate, ethyl butyrate, propyl butyrate, butyl butyrate, ethyl isobutyrate, propyl isobutyrate, butyl isobutyrate, or isobutyl isobutyrate. Based on the total mass of the electrolyte, the mass percentage of the first component is 20% to 60%.

5. The electrochemical device according to claim 1, wherein, The electrolyte further includes dinitrile compounds, including at least one selected from succinic anionyl nitrile, glutaronitrile, methylglutaronitrile, adiponitrile, heptacyanide, octanoic anionyl nitrile, anonadionitrile, or sebacate; the mass percentage of the dinitrile compounds is 0.1% to 3% based on the total mass of the electrolyte.

6. The electrochemical device according to claim 1, wherein, The electrolyte further includes lithium salt additives, which include at least one of lithium tetrafluoroborate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, or lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide; the lithium salt additives have a mass percentage content of 0.1% to 5% based on the total mass of the electrolyte.

7. The electrochemical device according to claim 1, wherein, Based on the total mass of the electrolyte, the mass percentage of the compound of formula I is 0.01% to 5%.

8. The electrochemical device according to claim 1, wherein, The compound of formula I includes at least one of the following compounds:

9. The electrochemical device according to claim 1, wherein, The silicon-based material includes at least one of silicon-oxygen composite material or silicon-carbon composite material, and the surface of the silicon-oxygen composite material or silicon-carbon composite material particles contains inorganic material, which includes at least one of LiF, NaF, KF, MgF2, CaF2 or AlF3; Based on the total mass of the silicon-based material, the inorganic material has a mass percentage content of 0.1% to 2%.

10. An electronic device comprising the electrochemical device according to any one of claims 1 to 9.

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