Lithium ion battery

Abstract

The invention discloses a lithium ion battery, and relates to the technical field of new energy batteries. The lithium ion battery comprises a positive electrode, a negative electrode, a diaphragm and an electrolyte, the material of the negative electrode comprises a silicon-containing compound, the electrolyte comprises a lithium salt, an organic solvent and an additive, and the additive comprises a carbonic ester additive, a lithium salt additive, a silane additive and a sulfonic acid additive. According to the lithium ion battery provided by the invention, the material of the negative electrode comprises the silicon-containing compound, silicon is introduced, and the gram volume of the negative electrode is relatively large, so that the lithium ion battery has relatively high energy density; the components in the electrolyte have a synergistic effect, so that the negative influence of the volume change of silicon in the negative electrode on the battery can be effectively relieved, the performance of the electrolyte is comprehensively improved, and the stability, the service life and the cycle performance of the battery are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy battery, and particularly relates to a lithium ion battery. BACKGROUND

[0002] The lithium ion battery is a kind of secondary battery which works by moving lithium ions between the positive electrode and the negative electrode. With the continuous widening of the application field of the lithium ion battery, people have put forward higher demands on improving the energy density of the lithium ion battery. The current commercial negative electrode material graphite has a theoretical specific capacity of 372 mAh g -1 , which is difficult to meet the demand of high energy density lithium ion battery. Silicon can effectively improve the energy density of the battery due to its high theoretical capacity (4200 mAh g -1 ) and low lithium intercalation potential, and is considered to be one of the most promising negative electrode materials that can replace graphite.

[0003] However, the poor conductivity of silicon leads to low lithium ion diffusion and poor performance. At the same time, the volume change of silicon during charging and discharging is close to 300%, and the generated solid electrolyte interphase (SEI) is unstable, which leads to the collapse, rupture and pulverization of silicon particles in the electrode, and ultimately causes the cycle life to decay. The current commercial negative electrode has a silicon content of 5% to 15%, and the gram capacity is about 500 to 600 mAh g -1 . To further improve the energy density of the battery, the gram capacity should be about 800 to 1200 mAh g -1 , and a higher content of silicon or even pure silicon negative electrode should be considered in the graphite, which also brings new challenges to the adaptation of the electrolyte.

[0004] The electrolyte is an important part of the silicon-carbon system lithium ion battery, and has an important influence on the cycle and interface stability of the silicon-carbon system battery. In order to improve the cycle life of the silicon-carbon system battery, most of the current electrolyte design is based on two aspects, one is to optimize the solvent to enhance its conductivity and improve the high and low temperature performance, and the other is to optimize the electrolyte additive to enhance the SEI stability. Among the currently published additives, fluoroethylene carbonate (FEC) and vinylene carbonate (VC) are indispensable due to their good film forming performance. However, the SEI formed by VC is relatively thick, which leads to high battery impedance and more irreversible capacity loss. Although FEC can form a uniform, stable and relatively thin SEI, a large amount of FEC is needed in the silicon-carbon system, which is prone to gas generation during high temperature storage, and cannot meet the high temperature demand. Moreover, with the further increase of the silicon content of the negative electrode, the amount of FEC needs to be limited, which cannot meet the demand of high energy density.

[0005] In the related art, the cycle performance of the lithium ion battery is poor and needs to be further improved. SUMMARY

[0006] Therefore, the application provides a lithium ion battery.

[0007] The application is implemented in the following manner. In one aspect, the application provides a lithium ion battery, which comprises a positive electrode, a negative electrode, a separator and an electrolyte.

[0008] Optionally, in some embodiments of the application, the silicon-containing compound comprises one or more of silicon oxide, silicon carbide and silicon; and / or

[0009] The material of the negative electrode further comprises graphite; and / or

[0010] The mass fraction of the silicon-containing compound in the negative electrode is greater than or equal to 50 wt%; and / or

[0011] The specific capacity of the negative electrode is 800 mAh / g to 1200 mAh / g.

[0012] Optionally, in some embodiments of the application, the lithium salt comprises one or more of lithium phosphate salt, lithium borate salt and lithium sulfonimide salt; the lithium phosphate salt comprises one or more of lithium hexafluorophosphate and lithium difluoro(oxalato)phosphate; the lithium borate salt comprises one or more of lithium tetrafluoroborate, lithium bis(oxalato)borate and lithium difluoro(oxalato)borate; the lithium sulfonimide salt comprises one or more of lithium bis(trifluoromethanesulfonyl)imide and lithium bis(difluorosulfonyl)imide; and / or

[0013] The molar concentration of the lithium salt in the organic solvent is 0.5 mol / L to 1.5 mol / L.

[0014] Optionally, in some embodiments of the application, the organic solvent has a donor number greater than 12; and / or

[0015] The organic solvent comprises one or more of carbonate solvent, carboxylic acid ester solvent, amine solvent, heterocyclic solvent, nitrile solvent, ketone solvent and sulfone solvent; the carbonate solvent comprises one or more of cyclic carbonate solvent and chain carbonate solvent; the carboxylic acid ester solvent comprises one or more of cyclic carboxylic acid ester solvent and chain carboxylic acid ester solvent.

[0016] Optionally, in some embodiments of the application, the cyclic carbonate solvent comprises one or more of vinyl carbonate and propylene carbonate; and / or

[0017] The chain carbonate solvent comprises one or more of dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate; and / or

[0018] The cyclic carboxylic acid ester solvent comprises γ-butyrolactone; and / or

[0019] The chain carboxylic acid ester solvent comprises one or more of ethyl acetate, methyl acetate, ethyl propionate; and / or

[0020] The amine solvent comprises one or more of dimethylformamide, triethylamine; and / or

[0021] The heterocyclic solvent comprises one or more of tetrahydrofuran, pyridine; and / or

[0022] The nitrile solvent comprises acetonitrile; and / or

[0023] The ketone solvent comprises acetone; and / or

[0024] The sulfone solvent comprises dimethyl sulfoxide; and / or

[0025] In the organic solvent, the volume fraction of the cyclic carbonate solvent is 10vol% to 20vol%; and / or

[0026] In the organic solvent, the volume fraction of the cyclic carboxylic acid ester solvent is 20vol% to 40vol%; and / or

[0027] In the organic solvent, the volume fraction sum of the chain carbonate solvent and the chain carboxylic acid ester solvent is 30vol% to 50vol%.

[0028] Optionally, in some embodiments of the present application, the carbonate additive comprises one or more of fluoroethylene carbonate, vinylene carbonate; and / or

[0029] In the electrolyte, the mass fraction of the carbonate additive is 3wt% to 20wt%.

[0030] Optionally, in some embodiments of the present application, the lithium salt additive comprises one or more of inorganic lithium salt additives, organic lithium salt additives; the inorganic lithium salt additive comprises lithium nitrate; the organic lithium salt additive comprises one or more of lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate phosphate; and / or

[0031] In the electrolyte, the mass fraction of the lithium salt additive is 0.1wt% to 3wt%.

[0032] Optionally, in some embodiments of the present application, the silane additive comprises one or more of tris(trimethylsilyl) phosphate, (trimethylsilyl) borate, dimethoxydimethylsilane, tetraethenylsilane; and / or

[0033] The mass fraction of the silane additive in the electrolyte is 0.1wt%-5wt%.

[0034] Optionally, in some embodiments of the present application, the sulfonic acid additive includes one or more of 1,3-propane sulfonate lactone, 1,4-butane sulfonate lactone, methane disulfonate methylene, vinyl sulfate, vinyl sulfite; and / or

[0035] The mass fraction of the sulfonic acid additive in the electrolyte is 0.1wt%-5wt%.

[0036] Optionally, in some embodiments of the present application, the material of the positive electrode includes one or more of lithium manganate, ternary lithium nickel cobalt manganate, lithium iron phosphate, lithium cobaltate, lithium titanate; and / or

[0037] The separator includes one or more of woven film, non-woven film, microporous film, separator paper, calendered film, single-layer polypropylene film, single-layer polyethylene film, polypropylene / ceramic-coated composite film, polyethylene / ceramic-coated composite film, polypropylene / polyethylene composite film, polypropylene / polyethylene / polypropylene composite film, polyester film, cellulose film, polyimide film, polyamide film, spandex film, aramid film.

[0038] The lithium ion battery provided by the present application has the following advantages: the material of the negative electrode includes a silicon-containing compound, silicon is introduced, and the capacity of the negative electrode is large, so that the lithium ion battery has high energy density; however, the volume of silicon changes greatly during lithium ion charging and discharging, the solid electrolyte interphase produced is unstable, the negative electrode is prone to cracking and pulverization, and the lithium ion battery is unstable and has poor cycle performance, so the electrolyte containing an organic solvent and multiple additives is applied to the lithium ion battery, the organic solvent can dissolve the unstable components in the solid electrolyte interphase, so that the interface film formed is more dense, and the organic solvent can anchor the additives, the carbonate additive can form a stable solid electrolyte interface film, the lithium salt additive has good solubility in the organic solvent and can provide necessary ion conductivity, the silane additive can further enhance the stability and interface adhesion of the solid electrolyte interface film, and the sulfonic acid additive can improve the quality of the solid electrolyte interface film and reduce the degradation of the negative electrode material, the components in the electrolyte synergistically act on each other, the negative effects of the volume change of silicon in the negative electrode on the battery can be effectively alleviated, the performance of the electrolyte is comprehensively improved, and the stability, service life and cycle performance of the battery are improved. DETAILED DESCRIPTION

[0039] 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. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Furthermore, it should be understood that the specific implementation methods described herein are only for illustration and explanation of this application and are not intended to limit this application.

[0040] In the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc. are used merely as illustrative purposes and do not impose numerical requirements or establish an order.

[0041] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0042] In this application, "at least one" means one or more, and "more than one" means two or more. "One or more", "at least one of the following", or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0043] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0044] The technical solution of this application is as follows:

[0045] This application provides a lithium-ion battery, comprising: a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode is made of a silicon-containing compound, and the electrolyte comprises a lithium salt, an organic solvent, and additives, wherein the additives include carbonate additives, lithium salt additives, silane additives, and sulfonic acid additives.

[0046] It should be noted that the carbonate additives mentioned are those containing a carbonate structure. The compound, wherein the lithium salt additive is a salt containing lithium ions, the silane additive is a compound containing silane groups, and the sulfonic acid additive is a compound containing... Compounds.

[0047] The lithium-ion battery provided in this application uses a silicon-containing compound as the negative electrode material. The introduction of silicon results in a large specific capacity of the negative electrode, leading to a high energy density in the lithium-ion battery. However, silicon undergoes significant volume changes during lithium-ion charging and discharging, resulting in an unstable solid electrolyte interphase. This makes the negative electrode prone to cracking and pulverization, causing instability and poor cycle performance in the lithium-ion battery. Therefore, this solution further applies an electrolyte containing organic solvents and various additives to the lithium-ion battery. The organic solvents can dissolve unstable components in the solid electrolyte interphase, resulting in a denser interfacial film. The organic solvents can also anchor the additives. Carbonate additives can form a stable solid electrolyte interfacial film, while lithium salt additives have good solubility in organic solvents and provide necessary ionic conductivity. Silane additives can further enhance the stability and interfacial adhesion of the solid electrolyte interfacial film, and sulfonic acid additives can improve the quality of the solid electrolyte interfacial film and reduce the degradation of the negative electrode material. The synergistic effect of the various components in the electrolyte effectively mitigates the negative impact of silicon volume changes in the negative electrode on the battery, comprehensively improving the performance of the electrolyte and enhancing the battery's stability, lifespan, and cycle performance.

[0048] In some embodiments, the silicon-containing compound includes silicon oxide (SiO2). x One or more of silicon carbide and silicon.

[0049] In some embodiments, the silicon-containing compound in the negative electrode has a mass fraction greater than or equal to 50 wt%, for example, it can be 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, or any range between two values. Within the mass fraction range of the silicon-containing compound, silicon can significantly improve the energy density of lithium-ion batteries, but it also causes side effects such as instability, reduced cycle performance, and decreased lifespan. These side effects can be reduced and the overall performance of lithium-ion batteries improved through the synergistic effect of organic solvents and various additives.

[0050] In some embodiments, the silicon-containing compound has a mass fraction of 100 wt% in the negative electrode; in other words, the negative electrode contains no other materials besides the silicon-containing compound, and the battery has a high energy density.

[0051] In some embodiments, the negative electrode material further includes graphite. Graphite has high electrical conductivity, a stable layered structure, good cycle stability, low volume expansion, and good thermal stability, which can improve the stability of the lithium-ion battery.

[0052] Furthermore, the mass fraction of graphite in the negative electrode is less than or equal to the mass fraction of the silicon-containing compound in the negative electrode.

[0053] In some embodiments, the specific capacity of the negative electrode is ≥800mAh / g.

[0054] Furthermore, the specific capacity of the negative electrode is between 800 mAh / g and 1200 mAh / g, for example, it can be 850 mAh / g, 900 mAh / g, 950 mAh / g, 1000 mAh / g, 1150 mAh / g, or any range between two values. Within this specific capacity range, the lithium-ion battery can have a higher energy density, thus improving the performance of the lithium-ion battery.

[0055] In some embodiments, the lithium salt includes one or more of lithium phosphate, lithium borate, and lithium sulfonylimide.

[0056] Specifically, the lithium phosphate salt includes one or more of lithium hexafluorophosphate and lithium difluorooxalate phosphate.

[0057] The lithium borate salt includes one or more of lithium tetrafluoroborate, lithium bis(oxalate)borate, and lithium difluorooxalateborate.

[0058] The lithium sulfonylimide salt includes one or more of lithium bis(trifluoromethanesulfonylimide) and lithium bis(difluorosulfonylimide).

[0059] In some embodiments, the molar concentration of the lithium salt in the organic solvent is 0.5 mol / L to 1.5 mol / L, for example, it can be 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, or any range between two values. It is understood that within the aforementioned molar concentration range of the lithium salt, the electrolyte is a low-concentration electrolyte, which can improve the safety, stability, and environmental friendliness of the lithium-ion battery.

[0060] In some embodiments, the number of organic solvent donors is greater than 12.

[0061] It should be noted that the solvent donor number (DN) is a parameter used to describe the ability of positively charged atoms or molecular groups in a solvent molecule. It is primarily used to assess the polarity and coordination ability of a solvent in solution. The solvent donor number can be used to measure the ability of a solvent molecule to donate lone pairs of electrons to other molecules; solvents with higher solvent donor numbers generally have stronger polarity and coordination energy.

[0062] The organic solvent provided in this application has a high solvent donor number and high solubility. When applied to lithium-ion batteries containing silicon anodes, it can dissolve unstable components in the solid electrolyte intermediate phase, resulting in a denser interfacial film. Furthermore, the organic solvent provided in this application exhibits good solubility for various additives, forming a stable solvation structure.

[0063] In some embodiments, the organic solvent includes one or more of carbonate solvents, carboxylic acid ester solvents, amine solvents, heterocyclic solvents, nitrile solvents, ketone solvents, and sulfone solvents.

[0064] Furthermore, the carbonate solvent includes one or more of cyclic carbonate solvents and chain carbonate solvents. The cyclic carbonate solvent includes one or more of ethylene carbonate and propylene carbonate, and the chain carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0065] The carboxylic acid ester solvents include one or more of cyclic carboxylic acid ester solvents and chain carboxylic acid ester solvents. The cyclic carboxylic acid ester solvents include γ-butyrolactone, and the chain carboxylic acid ester solvents include one or more of ethyl acetate, methyl acetate, and ethyl propionate.

[0066] The amine solvent includes one or more of dimethylformamide and triethylamine.

[0067] The heterocyclic solvents include one or more of tetrahydrofuran and pyridine.

[0068] The nitrile solvents include acetonitrile.

[0069] The ketone solvents include acetone.

[0070] The sulfone solvents include dimethyl sulfoxide.

[0071] In some embodiments, the volume fraction of the cyclic carbonate solvent in the organic solvent is 10 vol% to 20 vol%, for example, it can be 11 vol%, 12 vol%, 13 vol%, 14 vol%, 15 vol%, 16 vol%, 17 vol%, 18 vol%, 19 vol%, or any range between two values.

[0072] In some embodiments, the volume fraction of the cyclic carboxylic acid ester solvent in the organic solvent is 20 vol% to 40 vol%, for example, it can be 22 vol%, 25 vol%, 28 vol%, 30 vol%, 32 vol%, 35 vol%, 38 vol%, or any range between two values.

[0073] In some embodiments, the sum of the volume fractions of the chain carbonate solvent and the chain carboxylic acid ester solvent in the organic solvent is 30 vol% to 50 vol%, for example, it can be 32 vol%, 35 vol%, 38 vol%, 40 vol%, 42 vol%, 45 vol%, 48 vol%, or any range between two values.

[0074] Thus, within the volume fraction range of the various solvents mentioned above, it is beneficial to keep the impedance of the lithium-ion battery within a suitable range and reduce irreversible capacity loss.

[0075] In some embodiments, the carbonate additive includes one or more of fluoroethylene carbonate and vinylene carbonate. It should be noted that the carbonate solvent in the organic solvent can effectively dissolve lithium salts, giving the battery higher ionic conductivity and a wider voltage window; while the carbonate additive can form a good interfacial film, reducing interfacial side reactions.

[0076] In some embodiments, the mass fraction of the carbonate additive in the electrolyte is 3wt% to 20wt%, for example, it can be 4wt%, 5wt%, 6wt%, 8wt%, 10wt%, 12wt%, 14wt%, 15wt%, 16wt%, 18wt%, or any range between two values.

[0077] Thus, under the conditions of the above-mentioned carbonate additives and their mass fractions, a solid electrolyte interface film can be formed on the negative electrode surface, which enhances the stability of the electrolyte under high voltage and reduces the risk of thermal runaway.

[0078] In some embodiments, the lithium salt additive includes one or more of inorganic lithium salt additives and organic lithium salt additives. Further, the inorganic lithium salt additive includes lithium nitrate. The organic lithium salt additive includes one or more of lithium trifluoromethanesulfonate, lithium difluorophosphate, and lithium difluorobis(oxalato)phosphate.

[0079] Lithium nitrate not only provides good ionic conductivity, but also has good solubility in organic solvents with high DN values. It can participate in the formation of solvation structures to generate solid electrolyte interfacial films mainly composed of inorganic nitrides, thereby improving the stability of solid electrolyte interfacial films.

[0080] It should be noted that the lithium salt in the electrolyte has good solubility and can improve the ionic conductivity, while the lithium salt additives have poorer solubility than lithium salts and are mainly used to participate in the formation of the interfacial film.

[0081] In some embodiments, the mass fraction of the lithium salt additive in the electrolyte is 0.1 wt% to 3 wt%, for example, it can be 0.2 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, 2 wt%, 2.2 wt%, 2.5 wt%, 2.8 wt%, or any range between two values.

[0082] Thus, under the aforementioned conditions of lithium salt additives and their mass fractions, efficient lithium-ion conduction can be provided, the chemical stability of the electrolyte can be improved, and side reactions inside the lithium-ion battery can be reduced.

[0083] In some embodiments, the silane additives include one or more of tris(trimethylsilyl)phosphate, (trimethylsilyl)borate, dimethoxydimethylsilane, and tetravinylsilane.

[0084] In some embodiments, the mass fraction of the silane additive in the electrolyte is 0.1 wt% to 5 wt%, for example, it can be 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or any range between two values.

[0085] Thus, under the aforementioned conditions of silane additives and their mass fractions, silane additives, as positive electrode film-forming agents, can remove excessive HF generated during the decomposition of carbonate and lithium salt additives during cycling, thereby reducing gas production.

[0086] In some embodiments, the sulfonic acid additives include one or more of 1,3-propanesulfonate lactone, 1,4-butanesulfonate lactone, methylene disulfonate, vinyl sulfate, and vinyl sulfite.

[0087] In some embodiments, the sulfonic acid additive in the electrolyte has a mass fraction of 0.1 wt% to 5 wt%, for example, it can be 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or any range between two values.

[0088] Thus, under the conditions of the above-mentioned sulfonic acid additives and their mass fractions, electrode materials can be protected, electrolyte decomposition can be reduced, electrolyte stability under high voltage and high temperature can be enhanced, and the capacity retention and cycle performance of lithium-ion batteries can be improved.

[0089] In some embodiments, the positive electrode material includes one or more of lithium manganese oxide (LiMn2O4), ternary nickel cobalt manganese oxide (LiNiCoMnO2, NCM), lithium iron phosphate, lithium cobalt oxide, and lithium titanate.

[0090] In some embodiments, the diaphragm includes one or more of the following: woven membrane, nonwoven membrane (non-woven fabric), microporous membrane, diaphragm paper, rolled membrane, single-layer polypropylene membrane (PP), single-layer polyethylene membrane (PE), PP / ceramic coated composite membrane, PE / ceramic coated composite membrane, PP / PE composite membrane, PP / PE / PP composite membrane, polyester membrane (PET), cellulose membrane, polyimide membrane (PI), polyamide membrane (PA), spandex membrane, and aramid membrane.

[0091] It is understood that the lithium-ion battery provided in this application can be prepared by mixing lithium salt, organic solvent and various additives using conventional methods in the art to obtain an electrolyte, and then assembling the electrolyte with a positive electrode, a negative electrode and a separator using conventional methods in the art to obtain a lithium-ion battery.

[0092] The present application will be specifically described below through specific embodiments. The following embodiments are only some embodiments of the present application and are not intended to limit the present application.

[0093] Example 1

[0094] This embodiment provides a lithium-ion battery, including:

[0095] Electrolyte preparation: γ-Butyrolactone, methyl ethyl carbonate, and propylene carbonate were mixed in a volume ratio of 4:5:1 to obtain an organic solvent; lithium hexafluorophosphate was added, with a molar concentration of 1 mol / L in the organic solvent; then 7 wt% fluoroethylene carbonate, 0.2 wt% lithium nitrate, 2 wt% tris(trimethylsilyl)phosphate, and 2 wt% 1,3-propanesulfonic acid lactone were added to obtain the electrolyte.

[0096] Preparation of lithium-ion batteries: Doping graphite with 70 wt% SiO x The negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0097] Example 2

[0098] This embodiment provides a lithium-ion battery, including:

[0099] Electrolyte preparation: γ-Butyrolactone, methyl ethyl carbonate, and propylene carbonate were mixed in a volume ratio of 4:5:1 to obtain an organic solvent; lithium bis(difluorosulfonyl)imide was added, with a molar concentration of 1 mol / L in the organic solvent; then 7 wt% fluoroethylene carbonate, 0.2 wt% lithium nitrate, 2 wt% tris(trimethylsilyl)phosphate, and 2 wt% 1,3-propanesulfonate lactone were added to obtain the electrolyte;

[0100] Preparation of lithium-ion batteries: Doping graphite with 70 wt% SiO x The negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0101] Example 3

[0102] This embodiment provides a lithium-ion battery, including:

[0103] Electrolyte preparation: γ-Butyrolactone, ethyl propionate, and ethylene carbonate were mixed in a volume ratio of 4:5:1 to obtain an organic solvent; lithium hexafluorophosphate was added, with a molar concentration of 1 mol / L in the organic solvent; then 7 wt% fluoroethylene carbonate, 0.2 wt% lithium nitrate, 2 wt% tris(trimethylsilyl)phosphate, and 2 wt% 1,3-propanesulfonic acid lactone were added to obtain the electrolyte.

[0104] Preparation of lithium-ion batteries: Doping graphite with 70 wt% SiO x The negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0105] Example 4

[0106] This embodiment provides a lithium-ion battery, including:

[0107] Electrolyte preparation: Dimethylimide, acetone, and ethylene carbonate were mixed in a volume ratio of 4:5:1 to obtain an organic solvent; lithium hexafluorophosphate was added, with a molar concentration of 1 mol / L in the organic solvent; then 7 wt% fluoroethylene carbonate, 0.2 wt% lithium nitrate, 2 wt% tris(trimethylsilyl)phosphate, and 2 wt% 1,3-propanesulfonic acid lactone were added to obtain the electrolyte.

[0108] Preparation of lithium-ion batteries: Doping graphite with 70 wt% SiO xThe negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0109] Example 5

[0110] This embodiment provides a lithium-ion battery, including:

[0111] Electrolyte preparation: Tetrahydrofuran, acetonitrile, dimethyl sulfoxide, and ethylene carbonate were mixed in a volume ratio of 3:3:3:1 to obtain an organic solvent; lithium hexafluorophosphate was added, with a molar concentration of 1 mol / L in the organic solvent; then 7 wt% fluoroethylene carbonate, 0.2 wt% lithium nitrate, 2 wt% tris(trimethylsilyl)phosphate, and 2 wt% 1,3-propanesulfonic acid lactone were added to obtain the electrolyte.

[0112] Preparation of lithium-ion batteries: Doping graphite with 70 wt% SiO x The negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0113] Example 6

[0114] This embodiment provides a lithium-ion battery, including:

[0115] Electrolyte preparation: γ-Butyrolactone, methyl ethyl carbonate, and propylene carbonate were mixed in a volume ratio of 4:5:1 to obtain an organic solvent; lithium hexafluorophosphate was added, with a molar concentration of 1 mol / L in the organic solvent; then 5 wt% vinylene carbonate, 0.2 wt% lithium nitrate, 2 wt% tris(trimethylsilyl)phosphate, and 2 wt% 1,3-propanesulfonate lactone were added to obtain the electrolyte.

[0116] Preparation of lithium-ion batteries: Doping graphite with 70 wt% SiO x The negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0117] Example 7

[0118] This embodiment provides a lithium-ion battery, including:

[0119] Electrolyte preparation: γ-Butyrolactone, methyl ethyl carbonate, and propylene carbonate were mixed in a volume ratio of 4:5:1 to obtain an organic solvent; lithium hexafluorophosphate was added, with a molar concentration of 1 mol / L in the organic solvent; then 7 wt% fluoroethylene carbonate, 0.2 wt% lithium difluorobis(oxalato) phosphate, 2 wt% tris(trimethylsilyl) phosphate, and 2 wt% 1,3-propanesulfonic acid lactone were added to obtain the electrolyte.

[0120] Preparation of lithium-ion batteries: Doping graphite with 70 wt% SiO x The negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0121] Example 8

[0122] This embodiment provides a lithium-ion battery, including:

[0123] Electrolyte preparation: γ-Butyrolactone, methyl ethyl carbonate, and propylene carbonate were mixed in a volume ratio of 4:5:1 to obtain an organic solvent; lithium hexafluorophosphate was added, with a molar concentration of 1 mol / L in the organic solvent; then 7 wt% fluoroethylene carbonate, 0.2 wt% lithium nitrate, 2 wt% dimethoxydimethylsilane, and 2 wt% 1,3-propanesulfonic acid lactone were added to obtain the electrolyte.

[0124] Preparation of lithium-ion batteries: Doping graphite with 70 wt% SiO x The negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0125] Example 9

[0126] This embodiment provides a lithium-ion battery, including:

[0127] Electrolyte preparation: γ-Butyrolactone, methyl ethyl carbonate, and propylene carbonate were mixed in a volume ratio of 4:5:1 to obtain an organic solvent; lithium hexafluorophosphate was added, with a molar concentration of 1 mol / L in the organic solvent; then 7 wt% fluoroethylene carbonate, 0.2 wt% lithium nitrate, 2 wt% tris(trimethylsilyl)phosphate, and 2 wt% methanedisulfonate were added to obtain the electrolyte.

[0128] Preparation of lithium-ion batteries: Doping graphite with 70 wt% SiO xThe negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0129] Example 10

[0130] This embodiment provides a lithium-ion battery, including:

[0131] Electrolyte preparation: γ-Butyrolactone, methyl ethyl carbonate, and propylene carbonate were mixed in a volume ratio of 4:5:1 to obtain an organic solvent; lithium hexafluorophosphate was added, with a molar concentration of 1 mol / L in the organic solvent; then 7 wt% fluoroethylene carbonate, 0.2 wt% lithium nitrate, 2 wt% tris(trimethylsilyl)phosphate, and 2 wt% 1,3-propanesulfonic acid lactone were added to obtain the electrolyte.

[0132] Preparation of lithium-ion batteries: Doping graphite with 90 wt% SiO x The negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0133] Example 11

[0134] This embodiment provides a lithium-ion battery, including:

[0135] Electrolyte preparation: γ-Butyrolactone, methyl ethyl carbonate, and propylene carbonate were mixed in a volume ratio of 4:5:1 to obtain an organic solvent; lithium hexafluorophosphate was added, with a molar concentration of 1 mol / L in the organic solvent; then 7 wt% fluoroethylene carbonate, 0.2 wt% lithium nitrate, 2 wt% tris(trimethylsilyl)phosphate, and 2 wt% 1,3-propanesulfonic acid lactone were added to obtain the electrolyte.

[0136] Preparation of lithium-ion batteries: Doping graphite with 50 wt% SiO x The negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0137] Comparative Example 1

[0138] This embodiment provides a lithium-ion battery, including:

[0139] Electrolyte preparation: Lithium hexafluorophosphate (LiPF6) is added to propylene carbonate organic solvent, with a molar concentration of 1 mol / L; then 7 wt% fluoroethylene carbonate, 0.2 wt% lithium nitrate, 2 wt% tris(trimethylsilyl) phosphate and 2 wt% 1,3-propanesulfonic acid lactone are added to obtain the electrolyte.

[0140] Preparation of lithium-ion batteries: Doping graphite with 70 wt% SiO x The negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0141] Comparative Example 2

[0142] This embodiment provides a lithium-ion battery, including:

[0143] Electrolyte preparation: Lithium hexafluorophosphate (LiPF6) salt was added to chlorobenzene (DN < 10) organic solvent, with a molar concentration of 1 mol / L in the organic solvent; then 7 wt% fluoroethylene carbonate, 0.2 wt% lithium nitrate, 2 wt% tris(trimethylsilyl) phosphate and 2 wt% 1,3-propanesulfonic acid lactone were added to obtain the electrolyte.

[0144] Preparation of lithium-ion batteries: Doping graphite with 70 wt% SiO x The negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0145] Comparative Example 3

[0146] This embodiment provides a lithium-ion battery, including:

[0147] Electrolyte preparation: Lithium hexafluorophosphate (LiPF6) is added to propylene carbonate organic solvent, with a molar concentration of 1 mol / L; then 7 wt% fluoroethylene carbonate is added to obtain the electrolyte.

[0148] Preparation of lithium-ion batteries: Doping graphite with 70 wt% SiO x The negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0149] Comparative Example 4

[0150] This embodiment provides a lithium-ion battery, including:

[0151] Electrolyte preparation: Lithium hexafluorophosphate (LiPF6) is added to propylene carbonate organic solvent, with a molar concentration of 1 mol / L; then 0.2 wt% lithium nitrate is added to obtain the electrolyte.

[0152] Preparation of lithium-ion batteries: Doping graphite with 70 wt% SiO x The negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0153] Comparative Example 5

[0154] This embodiment provides a lithium-ion battery, including:

[0155] Electrolyte preparation: Lithium hexafluorophosphate (LiPF6) salt was added to propylene carbonate organic solvent, with a molar concentration of 1 mol / L in the organic solvent; then 2 wt% tris(trimethylsilyl)phosphate was added to obtain the electrolyte.

[0156] Preparation of lithium-ion batteries: Doping graphite with 70 wt% SiO x The negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0157] Comparative Example 6

[0158] This embodiment provides a lithium-ion battery, including:

[0159] Electrolyte preparation: Lithium hexafluorophosphate (LiPF6) salt was added to propylene carbonate organic solvent, with a molar concentration of 1 mol / L in the organic solvent; then 2 wt% of 1,3-propanesulfonic acid lactone was added to obtain the electrolyte.

[0160] Preparation of lithium-ion batteries: Doping graphite with 70 wt% SiO x The negative electrode and the positive electrode are prepared as ternary nickel-cobalt-manganese oxide. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, after forming for 3 cycles at 25°C and 0.1C rate, a lithium-ion battery is obtained.

[0161] Comparative Example 7

[0162] This embodiment provides a lithium-ion battery, including:

[0163] Electrolyte preparation: Lithium hexafluorophosphate (LiPF6) is added to propylene carbonate organic solvent, with a molar concentration of 1 mol / L; then 7 wt% fluoroethylene carbonate, 0.2 wt% lithium nitrate, 2 wt% tris(trimethylsilyl) phosphate and 2 wt% 1,3-propanesulfonic acid lactone are added to obtain the electrolyte.

[0164] Preparation of lithium-ion batteries: Graphite is used to prepare the negative electrode and ternary lithium nickel cobalt manganese oxide is used as the positive electrode. The negative electrode, positive electrode, PP separator and electrolyte are assembled and placed at 25°C for 12 hours. Then, the lithium-ion battery is obtained after 3 cycles of formation at 25°C and 0.1C rate.

[0165] The specific capacity of the negative electrodes of Examples 1-11 and Comparative Examples 1-7 was calculated. The lithium-ion batteries of Examples 1-11 and Comparative Examples 1-7 were subjected to cycle tests to obtain the cycle life or capacity retention rate. The results are shown in Table 1.

[0166] The specific capacity is calculated as follows: 100% SiO x The specific capacity of the negative electrode is 1350 mAh / g, and the specific capacity of the negative electrode of 100% graphite is 378 mAh / g. Based on the SiO content in the negative electrode... x The specific capacity is calculated by combining the ratio of graphite to the specific material.

[0167] The test method for cycle life and capacity retention (cycle curve) is as follows: the battery is charged to 4.3V at 0.33C constant current and constant voltage at 25℃, and then discharged to 2.5V at 0.5C constant current. This constitutes one cycle. The remaining capacity is the capacity retention. The cycle number or capacity retention of each battery is compared.

[0168] Table 1

[0169]

[0170]

[0171] As shown in Table 1, the battery provided in this application embodiment is doped with a large amount of silicon, which significantly improves the specific capacity of the negative electrode compared with Comparative Example 7. Furthermore, in this application, the synergistic combination of carbonate additives, lithium salt additives, silane additives, and sulfonic acid additives effectively mitigates the negative impact of silicon volume change in the negative electrode on the battery. By improving the performance of the electrolyte, it promotes the formation of a uniform and dense interface film, thereby improving the stability, lifespan, and cycle performance of the battery.

[0172] The technical solutions provided by the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A lithium-ion battery, characterized by, Comprise: a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the material of the negative electrode comprises a silicon-containing compound, the electrolyte comprises a lithium salt, an organic solvent, and an additive, the additive comprises a carbonate-based additive, a lithium salt-based additive, a silane-based additive, and a sulfonic acid-based additive.

2. The lithium ion battery according to claim 1, wherein: the silicon-containing compound comprises one or more of silicon oxide, silicon carbide, and silicon; and / or the material of the negative electrode further comprises graphite; and / or the mass fraction of the silicon-containing compound in the negative electrode is greater than or equal to 50wt%; and / or the specific capacity of the negative electrode is 800mAh / g-1200mAh / g.

3. The lithium ion battery according to claim 1, wherein: the lithium salt comprises one or more of a lithium phosphate salt, a lithium borate salt, and a lithium sulfonimide salt; the lithium phosphate salt comprises one or more of lithium hexafluorophosphate and lithium difluoro(oxalato)phosphate; the lithium borate salt comprises one or more of lithium tetrafluoroborate, lithium bis(oxalato)borate, and lithium difluoro(oxalato)borate; the lithium sulfonimide salt comprises one or more of lithium bis(trifluoromethanesulfonyl)imide and lithium bis(difluorosulfonyl)imide; and / or the molar concentration of the lithium salt in the organic solvent is 0.5mol / L-1.5mol / L.

4. The lithium ion battery according to claim 1, wherein: the donor number of the organic solvent is greater than 12; and / or the organic solvent comprises one or more of a carbonate-based solvent, a carboxylate-based solvent, an amine-based solvent, a heterocyclic solvent, a nitrile-based solvent, a ketone-based solvent, and a sulfone-based solvent; the carbonate-based solvent comprises one or more of a cyclic carbonate-based solvent and a chain carbonate-based solvent; the carboxylate-based solvent comprises one or more of a cyclic carboxylate-based solvent and a chain carboxylate-based solvent.

5. The lithium ion battery according to claim 4, wherein: the cyclic carbonate-based solvent comprises one or more of vinyl carbonate and propylene carbonate; and / or the chain carbonate-based solvent comprises one or more of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; and / or the cyclic carboxylate-based solvent comprises gamma-butyrolactone; and / or the chain carboxylate-based solvent comprises one or more of ethyl acetate, methyl acetate, and ethyl propionate; and / or the amine-based solvent comprises one or more of dimethylformamide and triethylamine; and / or the heterocyclic solvent comprises one or more of tetrahydrofuran and pyridine; and / or the nitrile-based solvent comprises acetonitrile; and / or the ketone-based solvent comprises acetone; and / or the sulfone-based solvent comprises dimethyl sulfoxide; and / or the volume fraction of the cyclic carbonate-based solvent in the organic solvent is 10vol%-20vol%; and / or the volume fraction of the cyclic carboxylate-based solvent in the organic solvent is 20vol%-40vol%; and / or the volume fraction of the chain carbonate-based solvent and the chain carboxylate-based solvent in the organic solvent is 30vol%-50vol%.

6. The lithium ion battery according to claim 1, wherein: The carbonate-based additive comprises one or more of fluoroethylene carbonate, vinylene carbonate; and / or The mass fraction of the carbonate-based additive in the electrolyte is 3wt%-20wt%. 7.The lithium ion battery of claim 1, wherein, The lithium salt-based additive comprises one or more of inorganic lithium salt additives, organic lithium salt additives; the inorganic lithium salt additive comprises lithium nitrate; the organic lithium salt additive comprises one or more of lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate phosphate; and / or The mass fraction of the lithium salt-based additive in the electrolyte is 0.1wt%-3wt%. 8.The lithium ion battery of claim 1, wherein, The silane-based additive comprises one or more of tris(trimethylsilyl)phosphate, (trimethylsilyl)borate, dimethoxydimethylsilane, tetraethenylsilane; and / or The mass fraction of the silane-based additive in the electrolyte is 0.1wt%-5wt%. 9.The lithium ion battery of claim 1, wherein, The sulfonic acid-based additive comprises one or more of 1,3-propanesulfonic acid lactone, 1,4-butane sulfonic lactone, methanedi sulfonic acid methylene ester, vinyl sulfonic acid, vinyl sulfite; and / or The mass fraction of the sulfonic acid-based additive in the electrolyte is 0.1wt%-5wt%. 10.The lithium ion battery of any one of claims 1-9, wherein, The material of the positive electrode comprises one or more of lithium manganate, ternary lithium nickel cobalt manganese acid, lithium iron phosphate, lithium cobaltate, lithium titanate; and / or The separator comprises one or more of woven membranes, non-woven membranes, microporous membranes, separator paper, calendered membranes, single-layer polypropylene membranes, single-layer polyethylene membranes, polypropylene / ceramic-coated composite membranes, polyethylene / ceramic-coated composite membranes, polypropylene / polyethylene composite membranes, polypropylene / polyethylene / polypropylene composite membranes, polyester membranes, cellulose membranes, polyimide membranes, polyamide membranes, spandex membranes, aramid membranes.

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