Electrolyte and battery containing the electrolyte

Abstract

PURPOSE: To provide an electrolyte and a battery containing the electrolyte.SOLUTION: An electrolyte includes a solvent, a lithium salt, and an additive. The solvent is composed of a fluorinated solvent. The additive includes tetravinylsilane. Based on a total mass of the electrolyte, a content of the tetravinylsilane is 0.01% to 1%. The fluorinated solvent in combination with a specific content of the tetravinylsilane is used in the electrolyte of the present invention, so that a battery has both excellent high-temperature storage capacity performance and high-temperature cycle performance on the basis that the battery has excellent high-voltage resistance performance.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention is in the field of lithium-ion battery technology and relates to electrolytes and batteries containing such electrolytes. [Background technology]

[0002] In recent years, the rapid development of the new energy vehicle market has led to an explosive growth in the market value of power batteries, primarily secondary alkali metal ion batteries. However, the energy density of currently commercially available secondary lithium ion batteries is already approaching its theoretical limit. Increasing the battery voltage has become an intuitive and feasible way to fundamentally address the driving range concerns of electric vehicle buyers.

[0003] However, as the battery voltage increases, the oxidative activity of the cathode material also increases, making the structure more susceptible to destruction. The electrolyte is prone to decomposition at high voltages, and side reactions within the electrolyte and at the interfaces between the electrolyte and the positive and negative electrodes intensify, especially under high-temperature conditions, resulting in rapid battery expansion, capacity loss, and deterioration of cycle performance. Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, how to make a battery have both high voltage and excellent high temperature performance has become a technical problem to be solved urgently in this field. [Means for solving the problem]

[0005] The present invention provides an electrolyte that uses a fluorinated solvent in combination with a specific content of tetravinyl silane (TVSI) to provide a battery with excellent high-voltage endurance performance, as well as excellent high-temperature storage performance and high-temperature cycling performance.

[0006] The present invention further provides a battery containing the above-described electrolyte, which has excellent high-voltage resistance, high-temperature storage performance, and high-temperature cycle performance.

[0007] A first aspect of the present invention provides an electrolyte solution comprising a solvent, a lithium salt, and an additive, wherein the solvent is a fluorinated solvent and the additive comprises tetravinylsilane. The content of the tetravinylsilane is 0.01% to 1% based on the total mass of the electrolyte solution.

[0008] In one alternative embodiment, the additive further comprises 1-propene 1,3-sultone (PST).

[0009] In one alternative embodiment, the content of the 1-propene-1,3-sultone is 0.01% to 1% based on the total mass of the electrolyte.

[0010] In one alternative embodiment, the mass ratio of the tetravinylsilane to the 1-propene-1,3-sultone is (50 to 1):(1 to 2).

[0011] In one alternative embodiment, the fluorinated solvent includes fluoroethyl methyl carbonate (FEMC) and fluoroethylene carbonate (FEC).

[0012] In one alternative embodiment, the mass ratio of the fluoroethyl methyl carbonate to the fluoroethylene carbonate is (15 to 2):(1 to 6).

[0013] In one alternative embodiment, the content of the lithium salt is 12% to 20% based on the total mass of the electrolyte solution.

[0014] In one alternative embodiment, the lithium salt comprises lithium hexafluorophosphate. The content of the lithium hexafluorophosphate relative to the total mass of the electrolyte solution is 8% to 20%.

[0015] A second aspect of the present invention provides a battery comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the electrolyte is the electrolyte provided by the first aspect of the present invention.

[0016] In one alternative embodiment, the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes a lithium manganese nickel oxide material having a carbon coating layer. The chemical formula of the lithium manganese nickel oxide material is Li a Ni x Mn y O4, where 0.90≦a≦1.10, 0.4≦x≦0.6, and 1.4≦y≦1.6. [Effects of the Invention]

[0017] The embodiments of the present invention have at least the following beneficial effects. The electrolyte of the present invention uses a combination of a fluorinated solvent and a specific content of tetravinylsilane. The fluorinated solvent provides the electrolyte with a relatively high fluorine content. The strong electron-withdrawing ability of fluorine atoms is advantageous for providing the electrolyte with high oxidation stability, thereby significantly improving the high-voltage endurance performance of the electrolyte. Furthermore, the specific content of tetravinylsilane forms a silicon-rich CEI film on the positive electrode side. This CEI film has excellent thermal stability and is resistant to swelling, reducing side reactions between the electrolyte and the positive electrode material at high temperatures and preventing gas generation, capacity loss, and increased direct current resistance (DCR) at high temperatures. This allows the battery to combine excellent high-voltage endurance performance, high-temperature storage performance, and high-temperature cycling performance. DETAILED DESCRIPTION OF THE INVENTION

[0018] In order to clarify the purpose, technical solutions and advantages of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in combination with the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, but not all of the embodiments. Any other embodiments that can be obtained based on the embodiments of the present invention without requiring creative work by those skilled in the art are also within the scope of protection of the present invention.

[0019] A first aspect of the present invention provides an electrolyte solution comprising a solvent, a lithium salt, and an additive, wherein the solvent comprises a fluorinated solvent and the additive comprises tetravinylsilane. The content of tetravinylsilane is 0.01% to 1% of the total mass of the electrolyte solution.

[0020] Fluorinated solvents can provide electrolytes with a relatively high fluorine content. The strong electron-withdrawing ability of fluorine atoms can provide electrolytes with relatively high oxidation stability, thereby significantly improving the high-voltage capability of the electrolyte. However, the carbon-fluorine bonds in fluorinated solvents are easily broken at high temperatures. The broken fluorine atoms react with active hydrogen in the electrolyte to generate hydrofluoric acid, which increases the acidity of the electrolyte and corrodes the alkaline materials in the SEI and CEI films, causing destruction of the positive and negative electrode interfaces and continuous side reactions. As a result, batteries are prone to gas generation at high temperatures, resulting in increased capacity loss and direct current resistance (DCR). The present invention adds a specific amount of tetravinylsilane (TVSI, structural formula shown in Formula I) to the electrolyte. Due to its molecular structure containing multiple unsaturated olefin groups, TVSI is preferentially oxidized and decomposed at the cathode, contributing to the formation of a CEI film. The resulting CEI film is a silicon-rich polymer that is resistant to solvent swelling and has excellent thermal stability, thereby suppressing side reactions between the electrolyte and the cathode material at high temperatures, thereby preventing gas generation, capacity loss, and increased DCR. The resulting electrolyte not only has high voltage resistance, but also excellent high-temperature storage and cycling performance. [ka]

[0021] Although the high-voltage stability of fluorinated solvents is superior to that of carbonate ester solvents, oxidative decomposition still exists without the protection of a stable CEI film. When the TVSI content is less than 0.01%, the resulting CEI film is too thin or uneven, resulting in insufficient protection of some interfaces. This leads to oxidative decomposition of the fluorinated solvent, resulting in the formation of side reaction products that cause insufficient interface stability. Further decomposition occurs during subsequent cycles and high-temperature storage, leading to continuous side reactions and reduced battery performance. Furthermore, when the TVSI content is greater than 1%, the CEI film grows excessively thick, significantly deteriorating the high-temperature performance of the battery.

[0022] For example, the content of tetravinylsilane relative to the total mass of the electrolyte may be 0.01%, 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1.0%, 1.2%, or a range consisting of any two of these values.

[0023] The present invention does not specifically limit the type of fluorinated solvent, and fluorinated carbonate esters and / or fluorinated carboxylic acid esters commonly used in this field can be selected.

[0024] In some specific embodiments, the fluorinated carbonate ester is fluoroethylene carbonate (FEC, CAS No.: 114435-02-8), difluoroethylene carbonate (DFEC (difluoroethylene carbonate), CAS No.: 311810-76-1), fluoropropylene carbonate (FPC (fluoropropylene carbonate), also known as 3-fluoropropylene carbonate, CAS No.: 127213-73-4), difluoropropylene carbonate (DFPC (difluoropropylene carbonate), also known as 3,3-difluoropropylene carbonate, CAS No.: 186098-91-9), trifluoropropylene carbonate (TFPC (trifluoropropylene carbonate), also known as 3,3,3-trifluoropropylene carbonate, CAS No.: 167951-80-6), methyl 2,2,2-trifluoroethyl carbonate (FEMC (methyl

[0033] The present invention is not limited to one or more of the following: ethyl 2,2,2-trifluoroethyl carbonate (CAS No.: 156783-95-8), ethyl 2,2,2-trifluoroethyl carbonate (CAS No.: 156783-96-9), bis(2,2,2-trifluoroethyl) carbonate (CAS No.: 1513-87-7).

[0025] In some specific embodiments, the fluorinated carboxylic acid ester includes one or more of 2,2-difluoroethyl acetate (DFEA, CAS No.: 1550-44-3), 2-fluoroethyl acetate (CAS No.: 462-26-0), 2,2,2-trifluoroethyl acetate (CAS No.: 406-95-1), 2,2-difluoroethyl propionate (CAS No.: 1133129-90-4), 2,2,2-trifluoroethyl propionate (CAS No.: 82259-34-5), 2,2,2-trifluoroethyl butyrate (CAS No.: 371-27-7), and 2,2-difluoroethyl butyrate (CAS No.: 1309602-59-2), but the present invention is not limited thereto.

[0026] The present invention does not specifically limit the content of the fluorinated solvent in the electrolyte, and the conventional content of the solvent in the electrolyte can be used as reference.

[0027] In one preferred embodiment, the additive further comprises 1-propene-1,3-sultone (PST). The structural formula of PST is shown in Formula II, which contains an unsaturated carbon-carbon double bond and a sulfonate ester structure. The unsaturated carbon-carbon double bond can participate in the oxidation reaction on the positive electrode side and cooperate with TVSI to form a more stable CEI film on the positive electrode. The sulfur-containing sulfonate ester structure in the PST structure is advantageous for forming a thermally stable sulfur-containing SEI film on the negative electrode side, thereby effectively reducing gas generation by the electrolyte on the negative electrode surface and further improving the high-temperature storage performance of the battery. [ka]

[0028] Research has revealed that if the content of 1-propene-1,3-sultone is too low, it becomes difficult to produce a more stable CEI film in cooperation with TVSI, and it also becomes difficult to form a stable sulfur-containing SEI film on the anode side. If the content of 1-propene-1,3-sultone is too high, the thickness of the formed CEI and SEI films becomes too large, resulting in an increase in the DCR of the battery. Therefore, if the content is too high or too low, it is detrimental to the high-temperature storage performance and high-temperature cycle performance of the battery. Preferably, the content of 1-propene-1,3-sultone is 0.01% to 1% by weight of the total electrolyte. For example, the content of 1-propene-1,3-sultone is 0.01%, 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1.0%, or a range consisting of any two of these values, relative to the total weight of the electrolyte.

[0029] Furthermore, the mass ratio of tetravinylsilane to 1-propene-1,3-sultone is (50 to 1):(1 to 2). By mixing tetravinylsilane and 1-propene-1,3-sultone within the above mass ratio range, the two are advantageous in combining to form higher quality and thinner CEI and SEI films, thereby reducing the DCR of the battery and providing the battery with better high-temperature cycle performance and high-temperature storage performance.

[0030] In one preferred embodiment, the fluorinated solvent includes fluoroethyl methyl carbonate (FEMC) and fluoroethylene carbonate (FEC). FEC decomposes to form an SEI film on the negative electrode surface, protecting the negative electrode interface. It has strong solubility for lithium salts, a wide liquid range, and good stability. However, its relatively high viscosity makes it difficult to provide the electrolyte with excellent fluidity and wettability. FEMC is a linear fluorinated carbonate solvent with a low viscosity, which is advantageous for mobility in lithium ion electrolytes. However, its low solubility in lithium salts makes it difficult to form a film at the negative electrode interface to protect the negative electrode. While FEMC alone is advantageous for improving the oxidative stability of the electrolyte on the positive electrode side, it must be used in combination with a large amount of additives; otherwise, there is a risk of continued electrolyte decomposition. While FEC alone can protect the negative electrode to some extent, it suffers from problems such as excessive viscosity and severe decomposition on the positive electrode side. The present invention utilizes a combination of FEMC and FEC to achieve a synergistic effect. After the SEI film is formed, a small amount of FEC can suppress the continued reaction of FEC when it is used as the main solvent component of the electrolyte due to the oxidation resistance of FEMC, and when used in combination with an additive, it can improve battery performance.

[0031] Furthermore, the mass ratio of fluoroethyl methyl carbonate to fluoroethylene carbonate is (15 to 2):(1 to 6). Within the above mass ratio range, the high-temperature storage performance and high-temperature cycle performance of the battery can be further improved.

[0032] The present invention does not specifically limit the type of lithium salt, and lithium salts commonly used in this field can be selected, including one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium hexafluoroarsenate, but the present invention is not limited thereto. Furthermore, the content of the lithium salt is 12% to 20% of the total mass of the electrolyte. Illustratively, the content of the lithium salt is 12%, 14%, 16%, 18%, 20%, or a range consisting of any two of these values, relative to the total mass of the electrolyte.

[0033] In one preferred embodiment, the lithium salt includes lithium hexafluorophosphate, and the content of lithium hexafluorophosphate is 8% to 20% relative to the total mass of the electrolyte. Illustratively, the content of lithium hexafluorophosphate relative to the total mass of the electrolyte is 8%, 10%, 12%, 14%, 16%, 18%, 20%, or a range consisting of any two of these values. Compared to other types of lithium salts, lithium hexafluorophosphate is less susceptible to corrosion even at high voltages.

[0034] A second aspect of the present invention provides a battery comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the electrolyte is the electrolyte provided by the first aspect of the present invention.

[0035] The battery of the present invention contains the above-mentioned electrolyte solution, and therefore can withstand high voltages and also have excellent high-temperature cycle performance and high-temperature storage performance.

[0036] The positive electrode sheet of the present invention includes a current collector and a positive electrode active material layer disposed on the current collector surface. Here, the positive electrode active material layer mainly contains a positive electrode active material, and further contains usual components such as a binder and a conductive agent.

[0037] The present invention does not specifically limit the type of positive electrode active material, and positive electrode active materials commonly used in this field can be selected, including one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese nickel oxide material, and lithium iron phosphate, but the present invention is not limited thereto.

[0038] In one preferred embodiment, the positive electrode active material comprises a lithium manganese nickel oxide material having a carbon coating layer, and the chemical formula of the lithium manganese nickel oxide material is Li a Ni x Mn y O4, where 0.90≦a≦1.10, 0.4≦x≦0.6, and 1.4≦y≦1.6.

[0039] The present invention does not limit the form in which the surface of the lithium manganese nickel oxide inner core is coated with the carbon coating layer, and therefore, the surface of the inner core may be partially coated, or the entire surface may be coated.

[0040] It should be understood that if the mass ratio of the carbon coating layer in the lithium manganese nickel oxide material is too low, it is difficult to effectively protect the inner core, and if the mass ratio is too high, it is detrimental to the energy density of the battery. In one preferred embodiment, the mass of the carbon coating layer accounts for 1% to 3% of the mass of the lithium manganese nickel oxide material. Here, the mass of the lithium manganese nickel oxide material refers to the mass of the inner core and does not include the mass of the carbon coating layer.

[0041] In one specific embodiment, the carbon source of the carbon coating layer includes one or more of fructose, polyethylene glycol, galactose, polyvinylpyrrolidone, and tannic acid. The carbon coating layer formed by the above carbon sources can effectively protect the surface of the inner core and at the same time form a large number of conductive carbon dots on the surface of the inner core, which is advantageous for improving the conductive performance of the material.

[0042] In one specific embodiment, the lithium manganese nickel oxide positive electrode material having a carbon coating layer can be prepared by the following method: A carbon source is pre-sintered under a nitrogen atmosphere to obtain an object to be coated, and then the object to be coated and a lithium manganese nickel oxide material are mixed together and then subjected to a secondary sintering process to obtain the lithium manganese nickel oxide positive electrode material having a carbon coating layer.

[0043] Furthermore, the temperature of the preliminary sintering treatment is 500°C to 700°C, and the time is 2 to 8 hours, and the temperature of the secondary sintering treatment is 350°C to 500°C, and the time is 12 to 20 hours.

[0044] The present invention does not particularly limit the conductive agent in the positive electrode sheet, and conductive agents commonly used in this field can be selected, including one or more of acetylene black, conductive carbon black, Ketjen black, conductive graphite, carbon nanotubes, conductive carbon fibers, and graphene, but the present invention is not limited thereto.

[0045] The present invention does not particularly limit the binder in the positive electrode sheet, and binders commonly used in this field can be selected, including one or more of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene butadiene rubber, and polyethylene oxide, but the present invention is not limited thereto.

[0046] The present invention does not particularly limit the current collector in the positive electrode sheet, and a positive electrode current collector commonly used in this field, such as aluminum foil, can be selected.

[0047] The positive electrode sheet of the present invention can be produced by a conventional method in this field, for example, by dispersing a positive electrode active material, a conductive agent, and a binder in a solvent to obtain a positive electrode active material layer slurry, applying the slurry onto a positive electrode current collector, and drying the slurry to obtain a positive electrode sheet.

[0048] In the present invention, the negative electrode sheet can be selected from the negative electrode sheets commonly used in this field. Here, the negative electrode sheet includes a current collector and a negative electrode active material layer provided on the surface of the current collector.

[0049] The negative electrode current collector can be selected from the negative electrode current collectors commonly used in this field, for example, a copper foil.

[0050] The negative electrode active material layer is mainly composed of a negative electrode active material, and further includes ordinary components such as a binder, a thickener, and a conductive agent.

[0051] The present invention does not particularly limit the type of the negative electrode active material, and the negative electrode active material commonly used in this field can be selected, including artificial graphite, natural graphite, hard carbon, soft carbon, nano-silicon (Si), silicon oxide negative electrode material (SiO x (0 < x < 2)), and one or more types of silicon-carbon negative electrode materials are included, but the present invention is not limited thereto).

[0052] The present invention does not particularly limit the types of the conductive agent and the binder in the negative electrode sheet, and the selection range can refer to the types of the conductive agent and the binder in the positive electrode sheet, so the description will not be repeated here.

[0053] The present invention does not particularly limit the type of the thickener in the negative electrode sheet, and the thickener commonly used in this field can be selected, including one or more types of sodium carboxymethyl cellulose, sodium polyacrylate, or polyvinyl alcohol, but the present invention is not limited thereto).

[0054] The negative electrode sheet of the present invention can be manufactured by using the ordinary methods in this field. For example, after dispersing a negative electrode active material, a conductive agent, a thickener, and a binder in a solvent to form a negative electrode active material layer slurry, the negative electrode active material layer slurry is coated on the negative electrode current collector, and a negative electrode sheet can be obtained after drying.

[0055] The function of the separator is to separate the positive and negative electrode sheets and provide a path for lithium ions to move. The present invention does not specifically limit the type of separator, and separators commonly used in this field, such as polypropylene separators and polyethylene separators, can be selected.

[0056] The present invention does not specifically limit the manufacturing method of a lithium ion battery, and a lithium ion battery can be manufactured using a manufacturing method commonly used in this field. For example, a positive electrode sheet, a separator, and a negative electrode sheet are stacked in order so that the separator is located between the positive electrode sheet and the negative electrode sheet, and a battery cell is obtained by a stacking or winding process, and then the lithium ion battery of the present invention can be obtained by processes such as firing, liquid injection, chemical conversion, and packaging.

[0057] The electrolyte and battery provided by the present invention will be described in more detail below with reference to specific examples.

[0058] Unless otherwise specified, the reagents, materials, and equipment used in the following examples are all common reagents, materials, and equipment in the art, and are all commercially available. Related reagents can also be synthesized by common methods in the art. [Example]

[0059] The lithium ion batteries of Examples 1 to 15 and Comparative Examples 1 to 9 are all fabricated according to the following method.

[0060] 1. Preparation of the electrolyte In a glove box with an argon gas atmosphere and a moisture content of less than 10 ppm, the lithium salt and additives are added to the solvent and mixed uniformly to obtain an electrolyte solution. Here, the lithium salt is lithium hexafluorophosphate, and its mass is 13% of the total mass of the electrolyte. The specific types and contents of the solvents and additives used in the electrolyte are as shown in Table 1. In Table 1, the content of the additive is expressed as mass % based on the total mass of the electrolyte. The mass percentage content of the solvent in the electrolyte solution is 100% - mass percentage content of the lithium salt - mass percentage content of the additive, but is not listed in Table 1.

[0061] 2. Preparation of the positive electrode sheet Positive electrode active material Li with carbon coating structure 0.98 Ni 0.45 Mn 1.55 O4, binder polyvinylidene fluoride, and conductive agent Super P are mixed in a weight ratio of 98:1:1, N-methylpyrrolidone is added, and the mixture is stirred under a vacuum mixer until the mixture becomes uniform and transparent to obtain a positive electrode slurry. The positive electrode slurry is then evenly applied to aluminum foil, which is then dried at room temperature and then transferred to an oven for drying. The aluminum foil is then cold-pressed and cut to obtain a positive electrode sheet.

[0062] 3. Preparation of negative electrode sheet The negative electrode active material, artificial graphite, conductive agent Super P, thickener carboxymethylcellulose sodium CMC-Na, and binder styrene butadiene rubber SBR are mixed in a mass ratio of 96:1:1:2, and deionized water is added to obtain negative electrode slurry under the action of a vacuum mixer. The negative electrode slurry is evenly coated onto the negative electrode current collector copper foil, which is then dried at room temperature and then transferred to a drying oven for drying. The negative electrode sheet is then obtained through cold pressing and cutting.

[0063] 4. Lithium-ion battery assembly A 12 μm thick polypropylene film was used as the separator. The positive electrode sheet, separator, and negative electrode sheet obtained above were stacked in order, with the separator positioned between the positive and negative electrode sheets to act as an insulator, to obtain a laminated core. The laminated core was then placed in an aluminum plastic film package and transferred to a vacuum oven where it was dried at 120°C. 3 g of the electrolyte obtained above was then injected, sealed, and the electrolyte was converted, resulting in a soft-pack lithium-ion battery with a capacity of 1 Ah.

[0064] [Table 1] In Table 1, DMC is dimethyl carbonate, DEC is diethyl carbonate, DTD is ethylene sulfate, and VC is vinylene carbonate.

[0065] Test Example The lithium ion batteries of the above examples and comparative examples were subjected to the following performance tests.

[0066] (1) 25°C DC resistance (DCR) test for lithium-ion batteries Place the battery in a thermostatic chamber and adjust the temperature to 25°C. Use a current of 0.33C to charge and discharge the battery three times, and record the discharge capacity of the last cycle as C0. At the specified temperature (25°C), discharge the battery to 50% SOC (State of Charge, reflecting the remaining capacity of the battery) at a current of 1C0. When the current is increased to 4C0 and maintained for 30 seconds, measure the difference between the updated stable voltage and the original plateau voltage. The ratio of this value to the 4C0 current value is the battery's DC resistance. The DCR test result after the first full charge of the battery is the initial DCR of the battery.

[0067] (2) Capacity retention rate of lithium-ion batteries when stored at high temperatures (60°C) At room temperature, the battery is discharged at a rate of 0.3C to the cut-off voltage, and the discharged capacity is designated as the initial discharge capacity C0. The battery is then fully charged and stored in a constant temperature bath at 60°C for 15 days. After storage, it is removed and cooled to room temperature, and then discharged at a rate of 0.3C to the cut-off voltage, and the discharge capacity is designated as C1. The storage capacity retention rate of this battery at a high temperature of 60°C is C1 / C0 × 100%.

[0068] (3) High temperature 45℃ cycle test The battery is cycled at 45°C. The voltage range is 3.4V to 4.85V, and the charge / discharge rate is 1C / 1C. The discharge capacity for each cycle is recorded. The test is terminated when the remaining battery capacity is 80% SOC, and the number of cycles actually achieved is recorded.

[0069] The test results are shown in Table 2.

[0070] [Table 2] In Table 2, "dead" indicates that the battery was not able to discharge normally.

[0071] From the data in Table 2, the following conclusions can be drawn from the analysis: 1) Comparing Examples 1-3 and Comparative Examples 1, 4, and 5, it can be seen that, compared to the case without TVSI, when the TVSI content in the electrolyte was within the range of 0.01% to 1%, the 25°C DCR of the battery was significantly reduced, and the 60°C storage capacity retention and the number of high-temperature 45°C cycles were also significantly improved. Among these, the overall battery performance was best when the TVSI content was 0.5%. However, when the TVSI content was less than 0.01%, it became difficult to form a complete SEI film at the negative electrode interface to protect the entire surface, resulting in a deterioration in the 25°C DCR, 60°C storage capacity retention, and high-temperature 45°C cycle performance of the battery. When the TVSI content exceeded 1%, the SEI film formed was too thick, resulting in a rapid increase in the battery's internal resistance and a significant deterioration in high-temperature storage performance and cycle performance.

[0072] 2) As can be seen from a comparison of Examples 2, 4-6, and 10-11, when TVSI and PST were used in combination and the PST content was controlled to 0.01% to 1%, the 25°C DCR of the battery was further reduced, and the 60°C storage capacity retention rate and the number of high-temperature 45°C cycles were further improved. This is because PST also participates in the film formation reaction on the negative electrode, further supporting the formation of a stable SEI film. However, when the added content was too high, the SEI film grew too thick, increasing the DCR of the battery and degrading its high-temperature storage performance and cycle performance.

[0073] 3) Comparing Examples 5, 7-9, and 12-15, using a solvent obtained by mixing FEMC and FEC in a mass ratio range of (15-2):(1-6) significantly reduced the 25°C DCR of the battery compared to using FEMC or FEC alone as the solvent, thereby enabling the battery to achieve both excellent 60°C storage performance and 45°C high-temperature cycling performance. When the mass ratio of FEMC to FEC was 4:3, the battery's performance in all aspects was the best.

[0074] 4) As can be seen from Comparative Examples 2 and 3, when conventional VC and DTD were used as electrolyte additives, the 25°C DCR of the battery was relatively large, and its 60°C storage capacity retention rate and high-temperature 45°C cycle performance were also relatively poor.

[0075] 5) As can be seen from Comparative Examples 6 to 9, when DMC was used alone, a large amount of electrolyte oxidation occurred during the formation stage, preventing the battery from cycling normally. Furthermore, when DEC was used alone as the solvent, or when DMC or DEC was mixed with a fluorinated carbonate solvent, the electrolyte was unable to withstand high voltages, its oxidation resistance deteriorated, and it showed a very large initial impedance. Therefore, the 60°C storage performance and high-temperature 45°C cycle performance of the battery were both relatively poor. [Industrial Applicability]

[0076] The electrolyte solution of the present invention uses a combination of a fluorinated solvent and a specific content of tetravinylsilane, which not only provides a battery with good high-voltage resistance, but also allows the battery to have excellent high-temperature storage performance and high-temperature cycle performance.

[0077] The above embodiments are merely for explaining the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art will understand that modifications can still be made to the technical solutions described in the above embodiments, or that equivalent replacements can be made for some or all of the technical features. Furthermore, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte solution comprising a solvent, a lithium salt, and an additive, wherein the solvent is a fluorinated solvent and the additive comprises tetravinylsilane; The content of the tetravinylsilane is 0.01% to 1% based on the total mass of the electrolyte solution.

2. 2. The electrolyte solution of claim 1, wherein the additive further comprises 1-propene 1,3-sultone.

3. 3. The electrolyte solution according to claim 2, wherein the content of the 1-propene-1,3-sultone is 0.01% to 1% based on the total mass of the electrolyte solution.

4. 4. The electrolyte solution according to claim 2, wherein the mass ratio of the tetravinylsilane to the 1-propene-1,3-sultone is (50 to 1):(1 to 2).

5. 10. The electrolyte of claim 1, wherein the fluorinated solvent comprises fluoroethyl methyl carbonate and fluoroethylene carbonate.

6. 6. The electrolytic solution according to claim 5, wherein the mass ratio of the fluoroethyl methyl carbonate to the fluoroethylene carbonate is (15 to 2):(1 to 6).

7. 2. The electrolyte solution according to claim 1, wherein the content of the lithium salt is 12% to 20% based on the total mass of the electrolyte solution.

8. the lithium salt comprises lithium hexafluorophosphate; 8. The electrolyte solution according to claim 7, wherein the content of the lithium hexafluorophosphate is 8% to 20% based on the total mass of the electrolyte solution.

9. A battery comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte solution, wherein the electrolyte solution is the electrolyte solution according to any one of claims 1 to 8.

10. The positive electrode sheet includes a positive electrode active material, the positive electrode active material including a lithium manganese nickel oxide material having a carbon coating layer, and the lithium manganese nickel oxide material has a chemical formula of Li ａ Ni ｘ Mn ｙ O ４ 10. The battery of claim 9, wherein 0.90≦a≦1.10, 0.4≦x≦0.6, and 1.4≦y≦1.6.

Images