Non-aqueous electrolyte and non-aqueous electrolyte secondary battery

Abstract

The application provides a nonaqueous electrolyte and a nonaqueous electrolyte secondary battery, and the nonaqueous electrolyte comprises: an electrolyte salt, a nonaqueous solvent, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane and allyl allyl sulfonate. The flexible network formed by 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane can enhance the mechanical resistance of the interface film, the allyl allyl sulfonate optimizes the ion conductivity and compactness of the interface film, the 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane and the allyl allyl sulfonate synergistically control the electrode interface, synergistically inhibit the electrode / electrolyte interface side reaction, reduce the battery impedance growth, and significantly improve the high-temperature cycle stability, storage performance and safety of the ternary battery.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery. Background Technology

[0002] With the increasing demands for energy density and cycle life of power batteries in fields such as new energy vehicles and energy storage power stations, ternary lithium batteries (such as NCM and NCA systems) have become the mainstream choice due to their high specific capacity. However, the insufficient stability of their electrode / electrolyte interface severely restricts their performance. Transition metal ions such as nickel, cobalt, and manganese in ternary cathode materials are prone to dissolving during charging and discharging, which leads to electrolyte decomposition and solid electrolyte interphase (SEI) film rupture and reconstruction. At the same time, under high temperature conditions, the main solvent of the electrolyte (such as carbonates) is prone to oxidation-reduction and gas generation, resulting in rapid capacity decay, a surge in impedance, and even safety hazards.

[0003] In existing technologies, electrolyte additives are used to optimize interfacial performance. However, while traditional additives such as fluoroethylene carbonate (FEC) and vinylene carbonate (VC) can improve SEI film formation, they suffer from a single-function limitation—organic additives result in films with low ion conductivity, while inorganic additives create films with insufficient mechanical flexibility, making it difficult to simultaneously address multiple issues such as metal ion dissolution, lithium dendrite growth, and electrolyte decomposition. Furthermore, some combined additive schemes, due to their non-complementary mechanisms, still suffer from imbalances in interfacial film density and mechanical stability, and limited improvement in high-temperature cycling performance, failing to meet the long-term service requirements of high-energy-density ternary batteries under harsh operating conditions. Summary of the Invention

[0004] The technical problem to be solved by this application is to provide a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery. The non-aqueous electrolyte of this application can suppress the dissolution of metal ions, suppress the side reactions at the electrode / electrolyte interface, reduce the increase of battery impedance, and significantly improve the high-temperature cycle stability, storage performance and safety of ternary batteries.

[0005] To address the aforementioned technical problems, this application provides a non-aqueous electrolyte comprising: an electrolyte salt, a non-aqueous solvent, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, and allyl allyl sulfonate.

[0006] Furthermore, the mass fraction of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane in the non-aqueous electrolyte is 0.1%-5%.

[0007] Furthermore, the mass fraction of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane in the non-aqueous electrolyte is 0.2%-3%.

[0008] Furthermore, the mass fraction of allyl sulfonate in the non-aqueous electrolyte is 0.2%-3%.

[0009] Furthermore, allyl allyl sulfonate accounts for 0.7%-2% of the mass fraction of the non-aqueous electrolyte.

[0010] Furthermore, the non-aqueous electrolyte also includes a sulfur-containing additive, wherein the sulfur-containing additive accounts for 0.5%-1% of the mass fraction of the non-aqueous electrolyte.

[0011] Furthermore, the non-aqueous electrolyte also includes a lithium salt additive, wherein the lithium salt additive accounts for 0.5%-1% of the mass fraction of the non-aqueous electrolyte.

[0012] Furthermore, the electrolyte salt accounts for 12.5% ​​to 15% of the mass fraction of the non-aqueous electrolyte, and the electrolyte salt is a lithium salt.

[0013] Furthermore, the non-aqueous solvent includes cyclic carbonates and chain carbonates, with cyclic carbonates including fluoroethylene carbonate and ethylene carbonate, and chain carbonates including diethyl carbonate and methyl ethyl carbonate.

[0014] This application also provides a non-aqueous electrolyte secondary battery, comprising: a positive electrode, a negative electrode, a separator, and the aforementioned non-aqueous electrolyte.

[0015] The beneficial effects of this application are: The non-aqueous electrolyte of this application utilizes 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, which, due to the high reactivity of its polyvinyl functional groups, can form a three-dimensional network structure with excellent mechanical flexibility and thermal stability through in-situ cross-linking on the electrode surface. This structure can withstand volume changes during electrode charging and discharging, inhibit lithium dendrite growth, and reduce the incidence of interfacial side reactions through the chemical stability of the siloxane structure. Allyl sulfonate, as a sulfonate additive, contains sulfonate groups that are strongly polar. These groups can preferentially undergo redox reactions with the solvent in the electrolyte. Through the alkenyl groups at both ends, a dense solid electrolyte interphase (SEI) film mainly composed of inorganic components such as Li2SO3 and Li2S is formed on the negative electrode surface. At the same time, the interaction between the polar groups and the transition metal ions of the positive electrode can inhibit the dissolution of metal ions and reduce the gas generation problem caused by electrolyte decomposition. The flexible network constructed from 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane enhances the mechanical resistance of the interfacial membrane, while allyl allyl sulfonate optimizes the ionic conductivity and compactness of the interfacial membrane. 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane and allyl allyl sulfonate synergistically regulate the electrode interface, synergistically suppress side reactions at the electrode / electrolyte interface, reduce battery impedance growth, and significantly improve the high-temperature cycle stability, storage performance, and safety of ternary batteries. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure.

[0017] Figure 1 This is a comparison chart showing the amount of transition metal ions dissolved after 7 days of storage in the batteries prepared in Examples 5, 10, and Comparative Examples 1 to 3 of this disclosure. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0019] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components.

[0020] Definitions of other specific words and phrases are provided throughout this disclosure. Those skilled in the art will understand that, in many, if not most, cases, such definitions apply to the prior and future use of the words and phrases thus defined.

[0021] This disclosure provides a non-aqueous electrolyte comprising: an electrolyte salt, a non-aqueous solvent, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, and allyl allyl sulfonate.

[0022] The structural formula of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane is shown in Formula (I), and the structural formula of allyl sulfonate is shown in Formula (II).

[0023]

[0024] Formula (I)

[0025] Formula (II) The non-aqueous electrolyte provided in the above embodiments of this disclosure uses 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, which, due to the high reactivity of its polyvinyl functional groups, can form a three-dimensional network structure with excellent mechanical flexibility and thermal stability through in-situ cross-linking on the electrode surface. This structure can withstand volume changes during electrode charging and discharging, inhibit lithium dendrite growth, and reduce the incidence of interfacial side reactions through the chemical stability of the siloxane structure. Allyl sulfonate, as a sulfonate additive, contains sulfonate groups that are strongly polar. These groups can preferentially undergo redox reactions with the solvent in the electrolyte. Through the alkenyl groups at both ends, a dense solid electrolyte interphase (SEI) film mainly composed of inorganic components such as Li2SO3 and Li2S is formed on the negative electrode surface. At the same time, the interaction between the polar groups and the transition metal ions of the positive electrode can inhibit the dissolution of metal ions and reduce the gas generation problem caused by electrolyte decomposition. The flexible network constructed from 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane enhances the mechanical resistance of the interfacial membrane, while allyl allyl sulfonate optimizes the ionic conductivity and compactness of the interfacial membrane. 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane and allyl allyl sulfonate synergistically regulate the electrode interface, synergistically suppress side reactions at the electrode / electrolyte interface, reduce battery impedance growth, and significantly improve the high-temperature cycle stability, storage performance, and safety of ternary batteries.

[0026] In some embodiments, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane comprises 0.1%-5% of the non-aqueous electrolyte by mass. For example, the mass fraction of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane in the non-aqueous electrolyte can be 0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, etc. Excessive amounts of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane will lead to an increase in the interfacial film thickness, thereby hindering Li... + Transmission increases impedance, leading to decreased cycling performance; when there is too little 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, the mechanical resistance of the generated SEI film is insufficient, and its ability to withstand electrode volume changes and inhibit lithium dendrite growth is limited.

[0027] Preferably, the mass fraction of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane in the non-aqueous electrolyte is 0.2%-3%. Within this range, a uniform and flexible three-dimensional siloxane network film can be formed in situ on the electrode surface, which can withstand changes in electrode volume, inhibit lithium dendrite growth, and does not significantly increase interfacial impedance.

[0028] In some embodiments, allyl sulfonate accounts for 0.2%-3% of the mass fraction of the non-aqueous electrolyte. For example, the mass fraction of allyl sulfonate in the non-aqueous electrolyte can be 0.2%, 0.4%, 0.6%, 0.8%, 1%, 2%, 3%, etc. When the mass fraction of allyl sulfonate is less than 0.2%, the generated SEI film is incomplete, and the effect of inhibiting dissolution and side reactions is limited. When the addition amount of allyl sulfonate reaches saturation (i.e., after the mass fraction is greater than 1%), the membrane structure tends to stabilize, and performance improvement enters a plateau period; further increasing the addition amount will not improve the performance of the SEI film. Excessive allyl sulfonate (content exceeding 2wt%) will instead lead to an excessively thick SEI film, hindering Li + Embedding in the negative electrode reduces cycle and storage performance.

[0029] Preferably, the mass fraction of allyl sulfonate in the non-aqueous electrolyte is 0.7%-2%. Within this range, the density and coverage of the solid electrolyte interface (SEI) film can effectively block the contact between the electrolyte and the electrode, and have the best effect in inhibiting the dissolution of metal ions and the decomposition of electrolyte to produce gas.

[0030] In some embodiments, the non-aqueous electrolyte further includes a sulfur-containing additive, wherein the sulfur-containing additive accounts for 0.5%-1% of the mass fraction of the non-aqueous electrolyte. As an example, the mass fraction of the sulfur additive in the non-aqueous electrolyte may be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc.

[0031] Preferably, the sulfur-containing additive is selected from at least one of 1,3-propenesulfonate lactone (PST) and 1,3-propanesulfonate lactone (PS). For example, the sulfur-containing additive is PST, or a mixture of PST and PS.

[0032] In some embodiments, the non-aqueous electrolyte further includes a lithium salt additive, wherein the lithium salt additive accounts for 0.5%-1% of the mass fraction of the non-aqueous electrolyte. As an example, the mass fraction of the lithium salt additive in the non-aqueous electrolyte can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc.

[0033] Preferably, the lithium salt additive is selected from at least one of lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(oxalato)borate. For example, the lithium salt additive is lithium difluorophosphate, the lithium salt additive is a mixture of lithium difluorophosphate and lithium bis(fluorosulfonyl)imide, or the lithium salt additive is a mixture of lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(oxalato)borate.

[0034] In some embodiments, the electrolyte salt accounts for 12.5% ​​to 15% of the mass fraction of the non-aqueous electrolyte, and the electrolyte salt is a lithium salt. As an example, the mass fraction of the electrolyte salt in the non-aqueous electrolyte can be 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, etc. Preferably, the lithium salt is lithium hexafluorophosphate (LiPF6).

[0035] In some embodiments, the non-aqueous solvent includes cyclic carbonates and chain carbonates, the cyclic carbonates including fluoroethylene carbonate and ethylene carbonate, and the chain carbonates including diethyl carbonate and methyl ethyl carbonate.

[0036] Preferably, the ratio of the total mass of fluoroethylene carbonate and ethylene carbonate to the mass of diethyl carbonate to the mass of methyl ethyl carbonate is (20-24):(20-25):(55-65). As an example, the ratio of the total mass of fluoroethylene carbonate and ethylene carbonate to the mass of diethyl carbonate to the mass of methyl ethyl carbonate can be 20:20:55, 20:23:60, 24:25:65, 22:22:57, etc.

[0037] This application also provides a non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery includes: a positive electrode, a negative electrode, a separator, and the aforementioned non-aqueous electrolyte.

[0038] Specifically, the positive electrode (positive electrode sheet) includes: positive electrode active material, conductive agent, binder and positive electrode current collector.

[0039] Specifically, the positive electrode active material is a ternary positive electrode material, for example, lithium nickel cobalt manganese oxide (LiNiO). x Co y Mn z O) system, for example, the positive electrode active material is NCM811.

[0040] There are no particular limitations on the conductive agent, and conductive agents commonly used by those skilled in the art can be used. For example, the conductive agent may be superconducting carbon black (Super P), acetylene black, Ketjen black, single-arm carbon nanotubes, or multi-arm carbon nanotubes. These conductive agents can be used alone or in any combination and proportion.

[0041] There are no particular limitations on the adhesive, and any adhesive commonly used by those skilled in the art can be used. For example, adhesives such as polyvinylidene fluoride, styrene-butadiene rubber, sodium carboxymethyl cellulose, or polyacrylic acid can be used. These adhesives can be used alone or in any combination and proportion.

[0042] There are no particular limitations on the positive electrode current collector, and current collectors commonly used by those skilled in the art can be used. As an example, the positive electrode current collector can be a metal foil such as aluminum foil, nickel foil, or a composite current collector. A composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0043] The positive electrode sheet can be prepared according to methods commonly used in the art. For example, the positive electrode sheet can be formed by uniformly dispersing the positive electrode active material, conductive agent, and binder in a solvent (e.g., N-methylpyrrolidone (NMP)) at a predetermined mass ratio to obtain a positive electrode slurry; coating the positive electrode slurry onto a positive electrode current collector, vacuum drying, and then rolling and cutting to obtain the positive electrode sheet.

[0044] Specifically, the negative electrode (negative electrode sheet) includes: negative electrode active material, conductive agent, binder and negative electrode current collector.

[0045] Specifically, the negative electrode active material is selected from one or more of graphite, silicon oxide, and silicon carbon materials. For example, the negative electrode active material is graphite or 90% graphite + 10% silicon carbon.

[0046] There are no particular limitations on the conductive agent, and conductive agents commonly used by those skilled in the art can be used. For example, the conductive agent may be superconducting carbon black (Super P), acetylene black, Ketjen black, single-arm carbon nanotubes, or multi-arm carbon nanotubes. These conductive agents can be used alone or in any combination and proportion.

[0047] There are no particular limitations on the adhesive, and any adhesive commonly used by those skilled in the art can be used. For example, adhesives such as polyvinylidene fluoride, styrene-butadiene rubber, sodium carboxymethyl cellulose, or polyacrylic acid can be used. These adhesives can be used alone or in any combination and proportion.

[0048] There are no particular limitations on the negative electrode current collector, and any negative electrode current collector commonly used by those skilled in the art can be used. As an example, the negative electrode current collector can be a metal foil such as copper foil or a composite current collector. Composite current collectors typically employ a "sandwich" structure, using an insulating polymer film (such as PET, PP, PE) as the intermediate substrate, and depositing a certain thickness of metallic copper layer on both its upper and lower surfaces through a combination of magnetron sputtering and electroplating processes.

[0049] The negative electrode sheet can be prepared according to methods commonly used in the art. For example, the negative electrode sheet can be formed by uniformly dispersing the negative electrode active material, conductive agent, and binder in a solvent (e.g., water) at a predetermined mass ratio to obtain a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, drying it, and then rolling and cutting it to obtain the negative electrode sheet.

[0050] Specifically, there are no particular restrictions on the membrane, and commonly used porous membranes with electrochemical and chemical stability can be used, such as single-layer or multi-layer films of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0051] The present application will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application. Where no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in the art or the product instructions shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0052] Example 1 Preparation of non-aqueous electrolyte 0.2 parts by mass of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane (first additive), 0.2 parts by mass of allyl sulfonate (second additive), 0.8 parts by mass of lithium difluorophosphate, 0.5 parts by mass of 1,3-propanesulfonate lactone (PS), and 15 parts by mass of lithium hexafluorophosphate were added to an organic solvent and stirred until homogeneous to obtain a non-aqueous electrolyte. The total amount of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, allyl sulfonate, lithium difluorophosphate, 1,3-propanesulfonate lactone, lithium hexafluorophosphate, and the organic solvent was 100 parts by mass. The organic solvent consisted of fluoroethylene carbonate, ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate. Based on the total mass of the organic solvent, the mass fractions of fluoroethylene carbonate were 6%, ethylene carbonate 15%, diethyl carbonate 22%, and methyl ethyl carbonate 57%.

[0053] Preparation of lithium secondary batteries 1. NCM811, acetylene black and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 96.5:2.2:1.3 and added to N-methylpyrrolidone (NMP) solvent for high-speed shear dispersion to obtain a homogenized positive electrode slurry. The positive electrode slurry is coated on an aluminum foil current collector, vacuum dried, and then rolled and cut to obtain a positive electrode sheet. 2. Graphite, acetylene black, sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are mixed in a mass ratio of 95.4:1.5:1.4:1.7, and then added to a solvent of water for high-speed shear dispersion to obtain a homogenized negative electrode slurry. The negative electrode slurry is coated onto a copper foil current collector, vacuum dried, and then rolled and cut to obtain the negative electrode sheet.

[0054] 3. Select a PE / PE / PP three-layer polymer separator with a thickness of 20μm as the battery separator, and place the separator, positive electrode and negative electrode in the order of positive electrode / separator / negative electrode / separator / positive electrode... from top to bottom, stack them to form the battery core, inject non-aqueous electrolyte, seal, and prepare a soft pack battery.

[0055] Example 2 The parts of Example 2 that are the same as those in Example 1 are omitted. The differences between Example 2 and Example 1 are as follows: When preparing the non-aqueous electrolyte, the amount of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane (the first additive) added is 0.1 parts by mass.

[0056] Example 3 The parts of Example 3 that are the same as those in Example 1 are omitted. The differences between Example 3 and Example 1 are as follows: When preparing the non-aqueous electrolyte, the amount of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane (the first additive) added is 0.3 parts by mass.

[0057] Example 4 The parts of Example 4 that are the same as those in Example 1 are omitted. The differences between Example 4 and Example 1 are as follows: When preparing the non-aqueous electrolyte, the amount of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane (the first additive) added is 0.5 parts by mass.

[0058] Example 5 The parts of Example 5 that are the same as those in Example 1 are omitted. The differences between Example 5 and Example 1 are as follows: When preparing the non-aqueous electrolyte, the amount of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane (the first additive) added is 0.7 parts by mass.

[0059] Example 6 The parts of Example 6 that are the same as those in Example 1 are omitted. The differences between Example 6 and Example 1 are as follows: When preparing the non-aqueous electrolyte, the amount of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane (the first additive) added is 1 part by mass.

[0060] Example 7 The parts of Example 7 that are the same as those in Example 1 are omitted. The differences between Example 7 and Example 1 are as follows: When preparing the non-aqueous electrolyte, the amount of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane (first additive) added is 3 parts by mass.

[0061] Example 8 The parts of Example 8 that are the same as those in Example 1 are omitted. The differences between Example 8 and Example 1 are as follows: When preparing the non-aqueous electrolyte, the amount of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane (the first additive) added is 5 parts by mass.

[0062] Example 9 The parts of Example 9 that are the same as those in Example 1 are omitted. The differences between Example 9 and Example 1 are as follows: When preparing the non-aqueous electrolyte, the amount of allyl sulfonate (second additive) added is 0.5 parts by mass.

[0063] Example 10 The parts of Example 10 that are the same as those in Example 1 are omitted. The differences between Example 10 and Example 1 are as follows: When preparing the non-aqueous electrolyte, the amount of allyl sulfonate (second additive) added is 0.7 parts by mass.

[0064] Example 11 The parts of Example 11 that are the same as those in Example 1 are omitted. The differences between Example 11 and Example 1 are as follows: When preparing the non-aqueous electrolyte, the amount of allyl sulfonate (second additive) added is 1 part by mass.

[0065] Example 12 The parts of Example Twelve that are the same as those in Example One are omitted. The differences between Example Twelve and Example One are: When preparing the non-aqueous electrolyte, the amount of allyl sulfonate (second additive) added is 2 parts by mass.

[0066] Example 13 The parts of Example 13 that are the same as those in Example 1 are omitted. The differences between Example 13 and Example 1 are as follows: When preparing the non-aqueous electrolyte, the amount of allyl sulfonate (second additive) added is 3 parts by mass.

[0067] Example 14 The parts of Example 14 that are the same as those in Example 1 are omitted. The differences between Example 14 and Example 1 are as follows: When preparing the non-aqueous electrolyte, the sulfur-containing additive is 1,3-propenesulfonyl lactone (PST), and the amount of PST added is 0.7 parts by mass. The lithium salt additive is lithium bisfluorosulfonylimide, and the amount of lithium bisfluorosulfonylimide added is 0.5 parts by mass. The amount of lithium hexafluorophosphate added is 12.5 parts by mass.

[0068] Example 15 The parts of Example 15 that are the same as those in Example 1 are omitted. The differences between Example 15 and Example 1 are as follows: In preparing the non-aqueous electrolyte, the sulfur-containing additive is a mixture of 1,3-propanesulfonate lactone (PS) and 1,3-propenesulfonate lactone (PST), with a mass ratio of PS to PST of 1:1, and the amount of sulfur-containing additive added is 1 part by mass. The lithium salt additive is a mixture of lithium difluorosulfonylimide, lithium difluorophosphate, and lithium bis(oxalato)borate, with a mass ratio of lithium difluorosulfonylimide, lithium difluorophosphate, and lithium bis(oxalato)borate of 3:3:4, and the amount of lithium salt additive added is 1 part by mass. The amount of lithium hexafluorophosphate added is 14 parts by mass.

[0069] Example 16 The parts of Example 16 that are the same as those in Example 1 are omitted. The differences between Example 16 and Example 1 are as follows: No sulfur-containing additives were added when preparing the non-aqueous electrolyte.

[0070] Example 17 The parts of Example 17 that are the same as those in Example 1 are omitted. The differences between Example 17 and Example 1 are as follows: No lithium salt additives were added when preparing the non-aqueous electrolyte.

[0071] Example 18 The parts of Example 18 that are the same as those in Example 1 are omitted. The differences between Example 18 and Example 1 are as follows: No sulfur-containing additives or lithium salt additives were added during the preparation of the non-aqueous electrolyte.

[0072] Comparative Example 1 The parts that are the same as those in Comparative Example 1 and Example 1 are omitted. The differences between Comparative Example 1 and Example 1 are as follows: 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane and allyl sulfonate were not added when preparing the non-aqueous electrolyte.

[0073] Comparative Example 2 The parts of Comparative Example 2 that are the same as those in Example 1 are omitted. The differences between Comparative Example 2 and Example 1 are as follows: Allyl allyl sulfonate was not added during the preparation of the non-aqueous electrolyte.

[0074] Comparative Example 3 The parts of Comparative Example 3 that are the same as those in Example 1 are omitted. The differences between Comparative Example 3 and Example 1 are as follows: 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane was not added when preparing the non-aqueous electrolyte.

[0075] The amounts of each substance added in Examples 1 to 18 and Comparative Examples 1 to 3 are shown in Table 1.

[0076] Table 1.

[0077] Electrochemical performance testing Electrochemical performance tests were conducted on the lithium secondary batteries of Examples 1 to 18 and Comparative Examples 1 to 3.

[0078] 1. Cyclic performance test at 25℃ In a constant temperature chamber at 25°C, the lithium secondary batteries prepared in Examples 1 to 18 and Comparative Examples 1 to 3 were charged to 4.2V at a constant current of 1C, then charged to 0.05C at a constant voltage, and then discharged to 2.8V at a constant current of 1C. This charge / discharge cycle was performed, and the capacity retention rate of the battery after 1000 cycles was recorded.

[0079] 2. Cyclic performance test at 45℃ In a constant temperature chamber at 45°C, the lithium secondary batteries prepared in Examples 1 to 18 and Comparative Examples 1 to 3 were charged at a constant current of 1C to 4.2V, then charged at a constant voltage to a current of 0.05C, and then discharged at a constant current of 1C to 2.8V. This charge / discharge cycle was performed, and the capacity retention rate of the battery after 500 cycles was recorded.

[0080] 3. Capacity retention test after 7 days of storage at 60℃ The lithium secondary batteries prepared in Examples 1 to 18 and Comparative Examples 1 to 3 were charged at a constant current of 1C to 4.2V at room temperature, then charged at a constant voltage to a current of 0.05C, and then discharged at a constant current of 1C to 2.8V. The initial discharge capacity was recorded as C0. Afterwards, the lithium secondary batteries were charged at a constant current of 1C to 4.2V at room temperature, then charged at a constant voltage to a current of 0.05C. They were then placed in a constant temperature chamber at 60°C and stored for 7 days. The lithium secondary batteries were then removed and discharged at a constant current of 1C to 2.8V at room temperature. The discharge capacity was recorded as C1.

[0081] The capacity retention rate of a lithium secondary battery stored at 60°C for 15 days is calculated as C1 / C0 × 100%.

[0082] 4. Gas production rate test after 7 days of storage at 60℃ The gas production rate of lithium secondary batteries prepared in Examples 1 to 18 and Comparative Examples 1 to 3 was measured by the water displacement gas collection method after storage at 60°C for 7 days.

[0083] 5. Transition metal ion leaching test after 7 days of storage The amount of transition metal ions dissolved after 7 days of storage was measured using a simulated battery static test on lithium secondary batteries prepared in Examples 1 to 18 and Comparative Examples 1 to 3.

[0084] Figure 1 This is a comparison chart showing the amount of transition metal ions dissolved after 7 days of storage in the batteries prepared in Examples 5, 10, and Comparative Examples 1 to 3 of this disclosure.

[0085] from Figure 1 As can be seen, the leaching amounts of nickel (Ni), cobalt (Co), and manganese (Mn) in Examples 5 and 10 were significantly lower than those in Comparative Examples 1 to 3. This indicates that the synergistic effect of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane and allyl allyl sulfonate can effectively inhibit the leaching of metal ions.

[0086] The test data of lithium secondary batteries in Examples 1 to 18 and Comparative Examples 1 to 3 are shown in Table 2.

[0087] Table 2.

[0088] According to the data in Table 2 of Examples 1 to 18 and Comparative Examples 1 to 3, the batteries prepared in Examples 1 to 18 have significantly higher capacity retention rates after 1000 cycles at 25°C, 500 cycles at 45°C, and after 7 days of storage at 60°C than the batteries prepared in Comparative Examples 1 to 3. The gas generation rate after 7 days of storage at 60°C is significantly lower than that of the batteries prepared in Comparative Examples 1 to 3.

[0089] In Comparative Example 1, due to the lack of interfacial regulation by 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane and allyl allyl sulfonate, the SEI membrane was formed by the decomposition of the electrolyte solvent. The membrane layer was loose and uneven, and prone to cracking and reconstruction. As a result, the interfacial side reactions were severe, the capacity decayed rapidly, the impedance surged, and gas production was serious.

[0090] Comparative Example 2 contains only 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane. Based on the data from Comparative Examples 1 and 2, the battery prepared in Comparative Example 2 exhibits significantly higher cycle retention at 25°C for 1000 cycles, higher capacity retention at 45°C for 500 cycles, and higher capacity retention after 7 days of storage at 60°C compared to the battery prepared in Comparative Example 1. However, its gas generation rate after 7 days of storage at 60°C is significantly lower than that of the battery prepared in Comparative Example 1. This indicates that the uniform and flexible three-dimensional siloxane network film formed in situ on the electrode surface by 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane not only withstands electrode volume changes and inhibits lithium dendrite growth but also does not significantly increase interfacial impedance, thus improving the battery's cycle retention, high-temperature capacity retention, and gas generation rate. However, due to the lack of allyl sulfonate, the resulting flexible organic membrane lacks dense inorganic components and cannot effectively block metal ion dissolution and electrolyte permeation. Interfacial side reactions remain significant, therefore, the cycle retention rate, high-temperature capacity retention rate, and gas generation rate are all significantly lower than those of Examples 1 to 18. Comparative Example 2 verifies the crucial role of allyl sulfonate in SEI membrane density and dissolution inhibition.

[0091] Comparative Example 3 contains only allyl allyl sulfonate. Based on the data from Comparative Examples 1 and 3, the battery prepared in Comparative Example 3 exhibits significantly higher cycle retention rate after 1000 cycles at 25°C, higher capacity retention rate after 500 cycles at 45°C, and higher capacity retention rate after 7 days of storage at 60°C compared to the battery prepared in Comparative Example 1. Conversely, the battery with a significantly lower gas generation rate after 7 days of storage at 60°C is also significantly lower than that of the battery prepared in Comparative Example 1. This indicates that the dense SEI film formed by allyl allyl sulfonate effectively blocks contact between the electrolyte and the electrode, inhibits metal ion dissolution and electrolyte decomposition gas generation, and improves the battery's cycle retention rate, high-temperature capacity retention rate, and gas generation rate. However, due to the lack of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, the resulting dense inorganic SEI film lacks sufficient mechanical flexibility and cannot withstand the volume changes during electrode charging and discharging. The film is prone to rupture, leading to increased interfacial impedance and continuous electrolyte decomposition. Consequently, the cycle retention rate, high-temperature capacity retention rate, and gas generation rate are significantly lower than those of Examples 1 to 18. Comparative Example 3 verified the indispensability of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane for the mechanical stability of the interfacial film.

[0092] According to the data from Examples 1 to 8 in Table 2, when the content of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane is in the range of 0.1 wt%-0.7 wt%, as the content of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane increases, the battery's capacity retention rate after 1000 cycles at 25°C, capacity retention rate after 500 cycles at 45°C, and capacity retention rate after 7 days of storage at 60°C all gradually increase, while the gas production rate after 7 days of storage at 60°C gradually decreases. When the content of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane increases to 0.7 wt%, the battery's capacity retention rate after 1000 cycles at 25°C... The battery exhibits the following performance characteristics: 1000-cycle retention at 25°C, 500-cycle capacity retention at 45°C, and maximum capacity retention after 7 days of storage at 60°C, followed by a minimum gas generation rate after 7 days of storage at 60°C. Further increasing the content of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane results in decreased capacity retention after 1000 cycles at 25°C, 500-cycle capacity retention at 45°C, and a decrease in capacity retention after 7 days of storage at 60°C, while the gas generation rate begins to increase after 7 days of storage at 60°C. This is because 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, as a polyvinyl crosslinking additive, when added in appropriate amounts, can form a uniform and flexible three-dimensional siloxane network film in situ on the electrode surface. This network film is resistant to electrode volume changes, inhibits lithium dendrite growth, and does not significantly increase interfacial impedance. However, when the addition amount exceeds 0.7 wt%, excessive 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane leads to an increase in interfacial film thickness, which in turn hinders Li-24% lithium production. + Transmission causes impedance to rise, leading to a decrease in cycling performance.

[0093] According to the data from Examples 1 and 9 to 13 in Table 2, when the content of allyl sulfonate is in the range of 0.2wt%-1wt%, with the increase of allyl sulfonate content, the battery's capacity retention rate after 1000 cycles at 25°C, capacity retention rate after 500 cycles at 45°C, and capacity retention rate after 7 days of storage at 60°C all gradually increase, while the gas generation rate after 7 days of storage at 60°C gradually decreases. When the content of allyl sulfonate exceeds 0.7wt%, the performance improvement slows down, and when the content of allyl sulfonate reaches 1wt%, all performance values ​​reach their optimal values. When the content of allyl sulfonate exceeds 1wt%, all performance values ​​decrease slightly; when the content of allyl sulfonate exceeds 2wt%, all performance values ​​begin to decrease significantly. Because the sulfonate groups in allyl sulfonate have strong polarity and high reactivity, they preferentially undergo oxidation-reduction on the electrode surface to form a dense SEI film mainly composed of inorganic components such as Li₂SO₃ and Li₂S. When the content of allyl sulfonate is low (below 0.2 wt%), the SEI film is incomplete, and its effect on inhibiting dissolution and side reactions is limited. As the content of allyl sulfonate gradually increases (0.2 wt%-1 wt%), the density and coverage of the SEI film significantly improve, effectively blocking the contact between the electrolyte and the electrode, inhibiting the dissolution of metal ions and the generation of gas from electrolyte decomposition. When the content of allyl sulfonate reaches saturation (1 wt%), the SEI film structure tends to stabilize, and the performance improvement enters a plateau period. Further increasing the content of allyl sulfonate will not improve the performance of the SEI film, and excessive addition of allyl sulfonate (more than 2 wt%) will instead lead to an excessively thick SEI film, hindering the Li₂S reaction. + Embedding in the negative electrode reduces cycle and storage performance.

[0094] The text and accompanying drawings in this disclosure are provided by way of example only to aid in understanding this disclosure. They should not be construed as limiting the scope of this disclosure in any way. Although certain embodiments and examples have been provided, it will be apparent to those skilled in the art, based on the content disclosed herein, that changes can be made to the illustrated embodiments and examples without departing from the scope of this disclosure.

[0095] Although this disclosure has been described with reference to exemplary embodiments, various changes and modifications may be suggested to those skilled in the art. This disclosure is intended to cover such changes and modifications that fall within the scope of the appended claims.

[0096] Nothing described in this disclosure should be construed as implying that any particular element, step, or function is an essential element that must be included within the scope of the claims. The scope of the patent subject matter is defined only by the claims.

Claims

1. A non-aqueous electrolyte, characterized in that, include: Electrolyte salts, non-aqueous solvents, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, and allyl allyl sulfonate.

2. The non-aqueous electrolyte according to claim 1, characterized in that, The mass fraction of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane in the non-aqueous electrolyte is 0.1%-5%.

3. The non-aqueous electrolyte according to claim 2, characterized in that, The mass fraction of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane in the non-aqueous electrolyte is 0.2%-3%.

4. The non-aqueous electrolyte according to claim 1, characterized in that, Allyl allyl sulfonate accounts for 0.2%-3% of the mass fraction of the non-aqueous electrolyte.

5. The non-aqueous electrolyte according to claim 4, characterized in that, Allyl allyl sulfonate accounts for 0.7%-2% of the mass fraction of the non-aqueous electrolyte.

6. The non-aqueous electrolyte according to claim 1, characterized in that, Also includes: The sulfur-containing additive accounts for 0.5%-1% of the mass fraction of the non-aqueous electrolyte.

7. The non-aqueous electrolyte according to claim 1, characterized in that, Also includes: The lithium salt additive accounts for 0.5%-1% of the mass fraction of the non-aqueous electrolyte.

8. The non-aqueous electrolyte according to claim 1, characterized in that, The electrolyte salt accounts for 12.5% ​​to 15% of the mass fraction of the non-aqueous electrolyte, and the electrolyte salt is a lithium salt.

9. The non-aqueous electrolyte according to claim 1, characterized in that, Non-aqueous solvents include cyclic carbonates and chain carbonates. Cyclic carbonates include fluoroethylene carbonate and ethylene carbonate, while chain carbonates include diethyl carbonate and methyl ethyl carbonate.

10. A non-aqueous electrolyte secondary battery, characterized in that, include: Positive electrode, negative electrode, separator, and non-aqueous electrolyte as described in any one of claims 1-9.

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