Electrolyte and battery comprising same

Abstract

Provided are an electrolyte and a battery comprising same. A steric hindrance group and / or an electron donating group are added into a fluoroethylene carbonate (FEC) molecule to reduce the reaction between the FEC molecule and LiPF6, generating less HF acid, further improving the high-temperature performance of batteries; additionally, the problem of thermal failure of batteries possibly caused by existing FECs in a high-temperature environment can be solved, thereby further improving the electrochemical performance and the safety performance of lithium-ion batteries in a high-temperature environment. The electrolyte is expected to provide lithium-ion batteries having higher electrochemical performance and safety performance to electric vehicles, mobile electronic devices, and large-scale energy storage systems, thereby promoting further development in these fields.

Description

Electrolyte and battery comprising the same

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on July 4, 2023, with application number 2023108124444 and application name “An electrolyte and a battery comprising the electrolyte”, the entire contents of which are incorporated by reference into this application.

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on August 23, 2023, with application number 2023110677987 and application name “An electrolyte and a battery comprising the electrolyte”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application belongs to the technical field of electrolytes, and in particular relates to an electrolyte and a battery including the electrolyte. Background Art

[0004] Lithium-ion batteries (LIBs) are considered suitable power sources for mobile electronic devices, electric vehicles, and large-scale energy storage systems due to their high energy density and long cycle life. To improve the energy density of LIBs, researchers have developed electrode materials with high reversible capacity, including high-voltage cathode materials and low-operating-potential anode materials with a potential close to 0 V (vs. Li / Li+).

[0005] However, degradation of the electrode-electrolyte interface can lead to poor battery cycling performance. To stabilize the electrode-electrolyte interface, various approaches have been proposed, such as surface coatings on electrode materials and the use of electrolyte additives. One of the most effective strategies to improve the stability of the electrode-electrolyte interface is the formation of an artificial solid electrolyte interface (SEI) using reducible and oxidizable compounds.

[0006] Silicon (Si) is considered to be the most promising anode material for next-generation lithium-ion batteries due to its high theoretical capacity. However, due to the huge volume changes of the silicon anode during cycling, the silicon particles break and new active surface sites are generated, which may lead to further irreversible electrolyte decomposition. In order to improve the electrochemical performance of silicon anodes, fluoroethylene carbonate (FEC) is used as an efficient reducible additive introduced into batteries with silicon anode systems. Studies have shown that FEC as an additive can effectively change the properties of the SEI layer on the surface of the anode and improve the electrochemical performance of anodes such as graphite and silicon.

[0007] Although FEC has a beneficial effect on the negative electrode, its decomposition mechanism is still under investigation. FEC can decompose into components such as vinyl carbonate (VC) and hydrofluoric acid (HF). However, some studies have reported that FEC-derived SEI films may have adverse effects on electrochemical performance in some battery systems. Koeun Kim et al. studied the effects of FEC and EC-based electrolytes on the cycling performance of LCO-NCM / Si-C electrodes. The results showed that the capacity loss of FEC at 60°C was greater than that of EC-based electrolytes. They believe that at high temperatures, FEC will react with lithium hexafluorophosphate to produce a relatively large amount of hydrofluoric acid, which will lead to the dissolution of positive electrode metal ions and ultimately lead to a decrease in capacity.

[0008] Therefore, although FEC plays a positive role in improving the electrochemical performance of silicon negative electrodes, it decomposes to produce hydrofluoric acid (HF) under high temperature environment, which destroys the positive electrode material and reacts with some organic salts to cause thermal failure of the battery. Therefore, it is crucial to seek improved FEC.

[0009] Summary of the Invention

[0010] In order to improve the problem that fluoroethylene carbonate (FEC) may cause thermal failure of the battery in a high temperature environment, the purpose of this application is to provide an electrolyte and a battery comprising the electrolyte. This application adds steric groups and / or electron-donating groups to the FEC molecules to reduce the reaction between the fluoroethylene carbonate molecules and LiPF6, thereby producing less HF acid, further improving the high temperature performance of the battery. At the same time, it can also overcome the problem that existing fluoroethylene carbonate may cause thermal failure of the battery in a high temperature environment, and further improve the electrochemical performance and safety performance of lithium-ion batteries in a high temperature environment. The electrolyte is expected to provide lithium-ion batteries with higher electrochemical performance and safety performance for electric vehicles, mobile electronic devices and large-scale energy storage systems, thereby promoting further development in these fields.

[0011] The purpose of this application is achieved through the following technical solutions:

[0012] An electrolyte comprises an organic solvent, an electrolyte lithium salt and an additive; the additive comprises an R group-modified fluoroethylene carbonate compound; the R group is a steric hindrance group and / or an electron-donating group.

[0013] According to an embodiment of the present application, the electron-donating group refers to a group that can increase the electron cloud density on the ethylene carbonate ring.

[0014] According to the embodiment of the present application, the steric hindering group refers to a group that causes mutual repulsion of the internal molecular structure of fluoroethylene carbonate in spatial arrangement.

[0015] According to the embodiment of the present application, the R group is selected from -CHO, -OH, -NR1R2, -S(=O)NR1R2, -S(=O)2NR1R2, -CONR1R2, -OC(=O)H, -NHCOH, substituted or unsubstituted -SC 1-12 Alkyl, substituted or unsubstituted -OC(=O)C 1-12 Alkyl, substituted or unsubstituted -NHCOC 1-12 Alkyl, substituted or unsubstituted C 1-12 Alkyl, substituted or unsubstituted C 6-12 Aryl, substituted or unsubstituted C 2-12 alkenyl, substituted or unsubstituted 5-12 membered heteroaryl; if substituted, the substituent is C 1-12 Alkyl; R1 and R2 are the same or different and are independently selected from H, C 1-12 alkyl.

[0016] According to the embodiment of the present application, the R group is selected from -CHO, -OH, -NR1R2, -S(=O)NR1R2, -S(=O)2NR1R2, -CONR1R2, -OC(=O)H, -NHCOH, substituted or unsubstituted -SC 1-6 Alkyl, substituted or unsubstituted -OC(=O)C 1-6 Alkyl, substituted or unsubstituted -NHCOC 1-6 Alkyl, substituted or unsubstituted C 1-6 Alkyl, substituted or unsubstituted C 6-8 Aryl, substituted or unsubstituted C 2-6 alkenyl, substituted or unsubstituted 5-8 membered heteroaryl; if substituted, the substituent is C 1-6 Alkyl; R1 and R2 are the same or different and are independently selected from H, C 1-6 alkyl.

[0017] According to the embodiment of the present application, the R group is selected from -CHO, -OH, -NR1R2, -S(=O)NR1R2, -S(=O)2NR1R2, -CONR1R2, -OC(=O)H, -NHCOH, substituted or unsubstituted -SC 1-3 Alkyl, substituted or unsubstituted -OC(=O)C 1-3 Alkyl, substituted or unsubstituted -NHCOC 1-3 Alkyl, substituted or unsubstituted C 3-6 Alkyl, substituted or unsubstituted C 6-7 Aryl, substituted or unsubstituted C 3-6 alkenyl, substituted or unsubstituted 5-6 membered heteroaryl; if substituted, the substituent is C 1-3Alkyl; R1 and R2 are the same or different and are independently selected from H, C 1-3 alkyl.

[0018] According to an embodiment of the present application, the R group is selected from -CHO, -OH, -NH2, -S(=O)NH2, -S(=O)2N(CH3)2, -CONH2, -OC(=O)H, -NHCOH, -S-CH3, -OC(=O)CH3, -NHCOCH3, tert-butyl, benzyl, cyclopentadienyl, and pyridyl.

[0019] According to an embodiment of the present application, the additive is selected from at least one compound represented by Formula I:

[0020] Here, R is defined as above.

[0021] According to an embodiment of the present application, the additive is selected from at least one of the compounds represented by Formula 1 to Formula 5:

[0022] According to an embodiment of the present application, the electrolyte lithium salt is selected from lithium hexafluorophosphate (LiPF6) or a combination of lithium hexafluorophosphate (LiPF6) and at least one of the following electrolyte lithium salts: lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium bis(trifluoromethylsulfonylimide), lithium difluorobis(oxalatophosphate), lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, tris(trifluoromethylsulfonyl)methyllithium, and lithium bis(trifluoromethylsulfonyl)imide.

[0023] According to an embodiment of the present application, the organic solvent is selected from carbonates and / or carboxylates, the carbonate is selected from at least one of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC) and ethyl methyl carbonate; the carboxylate is selected from at least one of propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, propyl propionate (PP), ethyl propionate (EP), methyl butyrate and ethyl butyrate.

[0024] According to an embodiment of the present application, the weight of the additive is 5% to 20% of the total weight of the organic solvent in the electrolyte, preferably 10% to 15%, for example 10%, 12%, 13%, 14% or 15%.

[0025] According to an embodiment of the present application, the electrolyte is used in a battery, preferably a lithium-ion battery.

[0026] The present application also provides a battery, which includes the above-mentioned electrolyte.

[0027] According to an embodiment of the present application, the battery further includes a positive electrode sheet containing a positive electrode active material, a negative electrode sheet containing a negative electrode active material, and a separator.

[0028] According to an embodiment of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on one or both sides of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material, a conductive agent and a binder.

[0029] According to an embodiment of the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both sides of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material, a conductive agent and a binder.

[0030] According to an embodiment of the present application, the mass percentage of each component in the positive electrode active material layer is: 80-99.8 wt % of positive electrode active material, 0.1-10 wt % of conductive agent, and 0.1-10 wt % of binder.

[0031] Preferably, the mass percentage of each component in the positive electrode active material layer is: 90-99.6 wt % of positive electrode active material, 0.2-5 wt % of conductive agent, and 0.2-5 wt % of binder.

[0032] According to an embodiment of the present application, the mass percentage of each component in the negative electrode active material layer is: 80-99.8 wt % of negative electrode active material, 0.1-10 wt % of conductive agent, and 0.1-10 wt % of binder.

[0033] Preferably, the mass percentage of each component in the negative electrode active material layer is: 90-99.6 wt % of negative electrode active material, 0.2-5 wt % of conductive agent, and 0.2-5 wt % of binder.

[0034] According to an embodiment of the present application, the conductive agent is selected from at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.

[0035] According to an embodiment of the present application, the binder is selected from at least one of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.

[0036] According to an embodiment of the present application, the negative electrode active material includes a carbon-based negative electrode material and / or a silicon-based negative electrode material.

[0037] According to the embodiment of the present application, the silicon-based negative electrode material is selected from nano-silicon, silicon-oxygen negative electrode material (SiO x(0 < x < 2)) or at least one of silicon-carbon anode materials.

[0038] According to an embodiment of the present application, the carbon-based anode material is selected from at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon, and soft carbon.

[0039] According to an embodiment of the present application, the mass ratio of the silicon-based anode material to the carbon-based anode material in the negative electrode active material is 9:1 to 1:9, for example, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, or 9:1.

[0040] According to an embodiment of the present application, the positive electrode active material is selected from one or more of lithium cobaltate, lithium manganate, lithium iron phosphate, and ternary materials.

[0041] According to an embodiment of the present application, the battery satisfies at least one of the following relationships:

[0042] (1) When the positive electrode active material is lithium cobaltate, the mass ratio of the additive in the battery to the mass of lithium cobaltate is within the range of 0.01352 - 0.1352, and the preferred mass ratio is 0.027;

[0043] (2) When the negative electrode active material is a carbon-based anode material, the mass ratio of the additive in the battery to the mass of the carbon-based anode material is within the range of 0.025 - 0.25, and the preferred mass ratio is 0.049;

[0044] (3) When the negative electrode active material is a silicon-based anode material, the mass ratio of the additive in the battery to the mass of the silicon-based anode material is within the range of 0.02 - 0.3, and the preferred mass ratio is 0.049;

[0045] (4) When the negative electrode active material is a carbon-based anode material and a silicon-based anode material, the mass ratio of the additive in the battery to the total mass of the carbon-based anode material and the silicon-based anode material is between 0.034 - 0.34, and the preferred mass ratio is 0.068.

[0046] Advantages of the present application:

[0047] The present application provides an electrolyte and a battery including the electrolyte. The electrolyte of the present application can solve the problem of possible battery thermal failure in a high-temperature environment and bring at least one of the following beneficial effects to the lithium-ion battery:

[0048] 1. Improve battery safety: By reducing the possibility of generating HF by FEC in a high-temperature environment, the R-group modified fluorinated ethylene carbonate compounds help reduce the risk of battery thermal failure in a high-temperature environment. This beneficial effect is particularly important for battery systems operating in harsh environments, such as electric vehicles and large-scale energy storage systems.

[0049] 2. Enhanced Battery Performance: R-group-modified fluoroethylene carbonate compounds help maintain battery cycling performance and capacity retention at high temperatures, thereby improving the overall performance of lithium-ion batteries. This is important for meeting the demand for high-performance batteries in applications such as mobile electronic devices and electric vehicles.

[0050] 3. Optimizing the solid electrolyte interface (SEI) layer: The R-group-modified fluoroethylene carbonate compounds of this application help form a more stable SEI layer, thereby maintaining the electrochemical performance and safety of the battery in high-temperature environments. This has a positive impact on improving the cycle life and durability of lithium-ion batteries.

[0051] 4. Applicability to Various Anode Materials: The R-group-modified fluoroethylene carbonate compounds of this application can be applied to silicon-based and / or carbon-based anode materials to improve their electrochemical performance. This means that this application has broad application potential and can be used in various types of lithium-ion batteries.

[0052] 5. Promote the development of related fields: This application provides important support for the technological progress and market development of electric vehicles, mobile electronic devices and large-scale energy storage systems by providing a lithium-ion battery with higher electrochemical performance and safety performance.

[0053] In summary, the electrolyte of this application not only solves the problem of thermal failure of batteries in high-temperature environments, but also makes a significant contribution to improving the electrochemical performance and safety of lithium-ion batteries. This will help meet the growing demand for high-performance batteries and promote the development of related fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] FIG1 is a comparison chart of the cycle capacity retention rates of the batteries of Comparative Example 1 and Examples 1-2.

[0055] FIG2 is a comparison diagram of the impedance of the batteries of Comparative Example 1 and Examples 1-2 after 200 cycles.

[0056] FIG3 is a comparison chart of the cycle capacity retention rates of the batteries of Comparative Example 1 and Examples 3-5.

[0057] FIG4 is a comparison diagram of the impedance of the batteries of Comparative Example 1 and Examples 3-5 after 200 cycles. DETAILED DESCRIPTION

[0058] To facilitate understanding of the present application, the present application will be described in more detail below. However, it should be understood that the present application can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments or examples and are not intended to limit this application.

[0060] The additives represented by Formula 1 to Formula 5 of the present application can be prepared by methods known in the art, or can be prepared by the following method:

[0061] Two-step preparation:

[0062] (1) Based on the general formula (1), a fluoroepoxy compound is prepared by a nucleophilic epoxidation reaction.

[0063] X in the general formula (1) can be a group with a certain degree of steric hindrance such as tetraphenylmethoxy, sulfonimide, cyclopentadienyl, tert-butyl, or a group with a certain degree of electron donating property such as aldehyde, alcohol, benzyl, amino, methylthio, formamide, formyloxy, pyridyl, acetamido, etc.

[0064] Synthesis route: Take a certain amount of the compound represented by general formula (1) and dissolve it in DMF. Use 0.3 mol / L hydrogen peroxide or tert-butyl peroxide alkaline solution as catalyst, stir and add it dropwise to the above solution. Maintain the temperature at about 80°C and react for 12 hours to obtain general formula (2).

[0065] (2) The general formula (2) reacts with carbon dioxide to form a fluorinated saturated cyclic carbonate.

[0066] The general formula (2) is dissolved in ethyl acetate, an appropriate amount of AlCl3 catalyst is added, carbon dioxide is introduced, the temperature is maintained at 80°C, and after the reaction for 12 hours, water is added to reduce the reaction temperature to room temperature, and the target product dissolved in ethyl acetate is extracted. Finally, a relatively pure additive is obtained by centrifugation, washing, and centrifugation.

[0067] The present application will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanations of the present application and should not be construed as limiting the scope of protection of the present application. All technologies implemented based on the above content of the present application are included within the scope of protection intended by the present application.

[0068] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the reagents, materials, etc. used in the following examples are all commercially available unless otherwise specified.

[0069] The lithium ion batteries of Examples 1-10 and Comparative Example 1 were prepared by the following steps:

[0070] 1) Preparation of positive electrode sheet

[0071] The positive electrode active materials lithium cobalt oxide (LiCoO2), polyvinylidene fluoride (PVDF), and conductive carbon black (super P) are mixed in a mass ratio of 7:1:2, N-methylpyrrolidone (NMP) is added, and the mixture is stirred under the action of a vacuum mixer until the mixed system becomes a positive electrode active slurry with uniform fluidity; the positive electrode active slurry is evenly coated on both surfaces of a 10μm thick aluminum foil; the coated aluminum foil is placed in an oven at 60℃ and dried for 24h, and then the required positive electrode sheet is obtained by roller pressing and slitting.

[0072] 2) Negative electrode preparation

[0073] Silicon-carbon negative electrode active material, artificial graphite, conductive carbon black (SP) and styrene-butadiene rubber (SBR) were mixed in a mass ratio of 2:6:1:1, deionized water was added, and a negative electrode active slurry was obtained under the action of a vacuum mixer; the negative electrode active slurry was evenly coated on both surfaces of an 8μm thick copper foil; the coated copper foil was dried at room temperature, then transferred to a 60℃ oven for drying for 24h, and then cold pressed and slit to obtain the negative electrode sheet.

[0074] 3) Preparation of electrolyte

[0075] In an argon-filled glove box (H2O <0.1ppm, O2 <0.1ppm), EC / DMC were mixed uniformly in a volume ratio of 1:1, and then fully dried lithium hexafluorophosphate (LiPF6) was quickly added thereto to form a concentration of 1 mol / L. After dissolution, an additive accounting for Xwt% of the total mass of the organic solvent was added, and the electrolytes of the examples and comparative examples were prepared after uniform mixing.

[0076] 4) Preparation of lithium-ion batteries

[0077] The positive electrode sheet of step 1), the negative electrode sheet of step 2), and the separator are stacked in the order of positive electrode sheet, separator, and negative electrode sheet, and then wound to obtain a battery cell; the battery cell is placed in an outer packaging aluminum foil, and the electrolyte of step 3) is injected into the outer packaging. After vacuum packaging, standing, forming, shaping, sorting, and other processes, a lithium-ion battery is obtained. In the lithium-ion battery, the injection amount of electrolyte is 9.5g, the addition amount of lithium cobalt oxide is 35.34g, and the total mass of carbon-based negative electrode material and silicon-based negative electrode material is 13.9g. The mass ratio of additives to lithium cobalt oxide is shown in Table 1; the mass ratio of additives to the total mass of carbon-based negative electrode material and silicon-based negative electrode material is shown in Table 1.

[0078] 5) Performance testing

[0079] Capacity retention: Charge at 45°C for 30 minutes at a constant current of 1C to 4.5V, then charge at a constant voltage of 4.5V, then discharge at 0.3C to 3V. Perform 200 charge cycles using this schedule and calculate the capacity retention.

[0080] Oven temperature: Place a fully charged battery in the test chamber, and heat the chamber at a rate of 5°C / min. When the temperature inside the chamber reaches 130°C±2°C, maintain the constant temperature for 60 minutes. If the battery does not fail at 130°C, heat it at a rate of 1°C / min until the battery temperature suddenly changes.

[0081] Acidity: The battery was disassembled after 200 cycles, and the electrolyte was obtained and titrated with sodium formate to determine the free HF acid content in the electrolyte.

[0082] Example 11

[0083] The preparation process of the lithium-ion battery of this embodiment is substantially the same as that of embodiment 1, except that the injection amount of the electrolyte is 19.08 g.

[0084] Example 12

[0085] The preparation process of the lithium-ion battery of this embodiment is substantially the same as that of embodiment 1, except that the injection amount of the electrolyte is 9.5 g.

[0086] Example 13

[0087] The preparation process of the lithium-ion battery of this embodiment is substantially the same as that of embodiment 1, except that the injection amount of the electrolyte is 9.54 g.

[0088] Table 1 Performance test results of batteries of Examples and Comparative Examples

[0089] The results in Table 1 show that the furnace failure temperatures of Examples 1-2 are higher than those of Comparative Example 1, indicating that the introduction of sulfonyl imide and cyclopentadienyl groups into FEC significantly increases the furnace failure temperature, demonstrating that the increased steric hindrance caused by the sulfonyl imide and cyclopentadienyl groups can effectively enhance the thermal stability of the battery. The furnace failure temperatures of Examples 3-5 are also higher than those of Comparative Example 1, indicating that the introduction of electron-donating groups at the ortho position of the F element can effectively reduce the electron density of ortho-hydrogen atoms, lowering their acidity and making it more difficult for them to escape to form HF acid, thereby improving the furnace performance of the battery.

[0090] After 200 cycles, the battery was disassembled to obtain an electrolyte, which was then titrated with sodium formate to determine the free HF acid content. The results are shown in Table 1. The HF content in Examples 1-2 was significantly lower than that in Comparative Example 1, indicating that the addition of a sterically hindered group can block the Lewis acid attack on F and H. The HF content in Examples 3-5 was significantly lower than that in Comparative Example 1, indicating that the addition of an electron-donating group can reduce the possibility of FEC releasing hydrofluoric acid.

[0091] Figure 1 compares the cycle capacity retention rates of the batteries of Comparative Example 1 and Examples 1-2, specifically showing the cycle capacity curves at 45°C. As can be seen from Figure 1, after 200 cycles, the capacity retention rates of Examples 1 and 2 are significantly higher than that of Comparative Example 1, demonstrating that the introduction of sulfonyl imide and cyclopentadienyl groups effectively prevents capacity fade caused by side reactions associated with FEC.

[0092] Figure 2 shows the fully charged EIS graphs of the batteries of Comparative Example 1 and Examples 1-2 after 200 cycles. As can be seen from Figure 2, the membrane impedance and charge transfer impedance of the battery of Examples 1-2 are significantly lower than those of the battery of Comparative Example 1, indicating that the introduction of sulfonimide and cyclopentadienyl groups can form a lower-impedance SEI film.

[0093] Figure 3 compares the cycle capacity retention rates of the batteries of Comparative Example 1 and Examples 3-5, specifically showing the cycle capacity curves of the batteries at 45°C. As can be seen from Figure 3, after 200 cycles, the capacity retention rates of the batteries of Examples 3-5 are all higher than those of Comparative Example 1, indicating that the introduction of aldehyde, formamide, pyridyl, and acetamide groups at adjacent carbon positions can prevent their rapid decomposition through an electron-donating effect, thereby improving the capacity retention rate during cycling.

[0094] Figure 4 shows the fully charged EIS graphs of the batteries of Comparative Example 1 and Examples 3-5 after 200 cycles. As can be seen from Figure 4, the membrane impedance and charge transfer impedance of the batteries of Examples 3-5 are significantly lower than those of the battery of Comparative Example 1, indicating that the introduction of aldehyde, formamide, pyridyl, and acetamide groups can form a lower-impedance SEI film while also reducing charge transfer impedance.

[0095] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0096] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. An electrolyte, wherein The electrolyte comprises an organic solvent, an electrolyte lithium salt and an additive; the additive comprises an R group-modified fluoroethylene carbonate compound; the R group is a steric hindrance group and / or an electron-donating group.

2. The electrolyte according to claim 1, wherein The R group is selected from -CHO, -OH, -NR1R2, -S(=O)NR1R2, -S(=O)2NR1R2, -CONR1R2, -OC(=O)H, -NHCOH, substituted or unsubstituted -SC 1-12 Alkyl, substituted or unsubstituted -OC(=O)C 1-12 Alkyl, substituted or unsubstituted -NHCOC 1-12 Alkyl, substituted or unsubstituted C 1-12 Alkyl, substituted or unsubstituted C 6-12 Aryl, substituted or unsubstituted C 2-12 alkenyl, substituted or unsubstituted 5-12 membered heteroaryl; if substituted, the substituent is C 1-12 Alkyl; R1 and R2 are the same or different and are independently selected from H, C 1-12 alkyl.

3. The electrolyte according to claim 2, wherein The R group is selected from -CHO, -OH, -NR1R2, -S(=O)NR1R2, -S(=O)2NR1R2, -CONR1R2, -OC(=O)H, -NHCOH, substituted or unsubstituted -SC 1-6 Alkyl, substituted or unsubstituted -OC(=O)C 1-6 Alkyl, substituted or unsubstituted -NHCOC 1-6 Alkyl, substituted or unsubstituted C 1-6 Alkyl, substituted or unsubstituted C 6-8 Aryl, substituted or unsubstituted C 2-6 alkenyl, substituted or unsubstituted 5-8 membered heteroaryl; if substituted, the substituent is C 1-6 Alkyl; R1 and R2 are the same or different and are independently selected from H, C 1-6 alkyl.

4. The electrolyte according to claim 3, wherein The R group is selected from -CHO, -OH, -NR1R2, -S(=O)NR1R2, -S(=O)2NR1R2, -CONR1R2, -OC(=O)H, -NHCOH, substituted or unsubstituted -SC 1-3 Alkyl, substituted or unsubstituted -OC(=O)C 1-3 Alkyl, substituted or unsubstituted -NHCOC 1-3 Alkyl, substituted or unsubstituted C 3-6 Alkyl, substituted or unsubstituted C 6-7 Aryl, substituted or unsubstituted C 3-6 alkenyl, substituted or unsubstituted 5-6 membered heteroaryl; if substituted, the substituent is C 1-3 Alkyl; R1 and R2 are the same or different and are independently selected from H, C 1-3 alkyl.

5. The electrolyte according to any one of claims 1 to 4, wherein The R group is selected from -CHO, -OH, -NH2, -S(=O)NH2, -S(=O)2N(CH3)2, -CONH2, -OC(=O)H, -NHCOH, -S-CH3, -OC(=O)CH3, -NHCOCH3, tert-butyl, benzyl, cyclopentadienyl, and pyridyl.

6. The electrolyte according to any one of claims 1 to 5, wherein The additive is selected from at least one of the compounds shown in Formula I: Wherein, R is defined as described in any one of claims 1-5.

7. The electrolyte according to any one of claims 1 to 6, wherein: The additive is selected from at least one of the compounds represented by Formula 1 to Formula 5:

8. The electrolyte according to any one of claims 1 to 7, wherein: The electrolyte lithium salt is selected from lithium hexafluorophosphate (LiPF6) or a combination of lithium hexafluorophosphate (LiPF6) and at least one of the following electrolyte lithium salts: lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium bis(trifluoromethylsulfonylimide), lithium difluorobis(oxalatophosphate), lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, tris(trifluoromethylsulfonyl)methyl lithium, and lithium bis(trifluoromethylsulfonyl)imide.

9. The electrolyte according to any one of claims 1 to 8, wherein: The weight of the additive is 5% to 20% of the total weight of the organic solvent in the electrolyte.

10. The electrolyte according to claim 9, wherein The weight of the additive is 10% to 15% of the total weight of the organic solvent in the electrolyte.

11. A battery comprising the electrolyte according to any one of claims 1 to 10.

12. The battery according to claim 11, wherein The battery also includes a positive electrode sheet containing a positive electrode active material, a negative electrode sheet containing a negative electrode active material, and a separator; The negative electrode active material includes a carbon-based negative electrode material and / or a silicon-based negative electrode material. The silicon-based negative electrode material is selected from at least one of nano-silicon, silicon oxide negative electrode material (SiO x (0 < x < 2)), or silicon-carbon negative electrode material, and the carbon-based negative electrode material is selected from at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon, and soft carbon; The positive electrode active material is selected from one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and ternary materials.

13. The battery according to claim 10 or 11, wherein The battery satisfies at least one of the following relationships: (1) If the positive electrode active material is lithium cobalt oxide, the mass ratio of the additive in the battery to the mass ratio of the lithium cobalt oxide is in the range of 0.01352-0.1352; (2) If the negative electrode active material is a carbon-based negative electrode material, the mass ratio of the additive in the battery to the mass ratio of the carbon-based negative electrode material is in the range of 0.025-0.25; (3) If the negative electrode active material is a silicon-based negative electrode material, the mass ratio of the additive in the battery to the mass ratio of the silicon-based negative electrode material is in the range of 0.02-0.3; (4) If the negative electrode active material is a carbon-based negative electrode material and a silicon-based negative electrode material, the mass ratio of the additive in the battery to the total mass of the carbon-based negative electrode material and the silicon-based negative electrode material is between 0.034 and 0.34.

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