Electrolyte and secondary battery capable of reducing gas generation

Abstract

The application provides a kind of electrolyte that can reduce gas production, secondary battery.The electrolyte includes organic solvent, lithium salt, film-forming additive and quinuclidine additive.The application introduces quinuclidine into electrolyte, which can capture hydrofluoric acid produced by side reaction inside the battery through complexation, reduce the reactivity of hydrofluoric acid, slow down the rate of structural rupture of positive and negative electrode interface film due to continuous corrosion by hydrofluoric acid, and further slow down the rate of gas production due to the exposure of positive and negative electrode interface active sites and the catalysis of solvent decomposition, thereby reducing the rate of side reaction gas production during battery cycling, ensuring that the battery can still maintain a low gas production rate after long-term cycling, reducing the risk of battery swelling, and improving battery life and safety.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to an electrolyte and a secondary battery that can reduce gas production. Background Technology

[0002] Currently, lithium-ion battery technology is developing towards high nickel content in the positive electrode and high silicon content in the negative electrode. This change in the positive and negative electrodes makes the battery more prone to side reactions and gas generation during use. The gas generated by these side reactions accumulates inside the battery casing, which not only increases the battery's internal resistance, affecting its power and cycle performance, but also causes an increase in internal pressure. This significantly increases the risk of battery casing rupture after long-term use, thus increasing battery safety risks. These problems are more pronounced in cylindrical batteries. Due to the high internal space utilization and small gas chamber volume of cylindrical batteries, and the rigid casing, the accumulation of gaseous byproducts after long-term cycling leads to higher internal pressure. This often results in bulging of the cylindrical cover in the later stages of cycling, posing a safety hazard of casing cracking and leakage.

[0003] Existing technologies have documented methods to reduce battery gas production from the perspective of electrolyte. Generally, this involves adding high-temperature film-forming additives to improve the stability of the positive and negative electrode interfacial films and slow down the side reaction rate between the solvent and the positive and negative electrode interfaces. In the early stages of battery cycling, when the interfacial film maintains a normal structure, the side reaction rate is very low, and gas production is typically minimal. However, the positive and negative electrode interfacial films formed by film-forming additives are susceptible to hydrofluoric acid corrosion, leading to structural rupture. That is, during cycling, the interfacial film is continuously corroded by hydrofluoric acid. In the later stages of cycling, the interfacial film structure ruptures, exposing active sites that come into contact with the solvent. This causes a rapid increase in the side reaction gas production rate, resulting in battery swelling in the later stages of cycling. Summary of the Invention

[0004] The main objective of this invention is to provide an electrolyte and secondary battery that can reduce gas production, thereby solving the problem that lithium-ion batteries in the prior art produce a lot of gas, resulting in short battery life and poor safety performance.

[0005] To achieve the above objectives, according to one aspect of the present invention, an electrolyte that can reduce gas production is provided, comprising an organic solvent, a lithium salt, a film-forming additive, and a quinine ring additive.

[0006] By applying the technical solution of this invention, quinine cyclic substances are introduced into the electrolyte. Quinine cyclic substances can capture hydrofluoric acid produced by side reactions inside the battery through complexation, reduce the reactivity of hydrofluoric acid, slow down the rate of structural rupture of the positive and negative electrode interface film due to continuous corrosion by hydrofluoric acid, and thus slow down the rate of gas generation due to exposure of active sites at the positive and negative electrode interfaces and catalytic solvent decomposition. This reduces the gas generation rate of side reactions during battery cycling, ensuring that the battery can maintain a low gas generation rate even after long-term cycling, reducing the risk of battery swelling, and improving battery life and safety.

[0007] Furthermore, the quinine ring additive accounts for 0.01~10% of the electrolyte by weight; and / or the quinine ring additive has the structure shown in general formula (1):

[0008] (1);

[0009] R1 is selected from hydrogen, halogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkynyl, substituted or unsubstituted C6-C12 aromatic, substituted or unsubstituted C1-C6 alkylcyano, substituted or unsubstituted C2-C6 ester, or substituted or unsubstituted C1-C6 alkylamino. Under the above conditions, the corrosion of the positive and negative electrode interface film by hydrofluoric acid can be effectively suppressed. Even during long-term cycling, the structural integrity of the interface film can be maintained, significantly reducing the rate of solvent side reaction gas generation caused by film rupture, thereby reducing the sharp increase in internal battery pressure, effectively reducing the occurrence of battery swelling, and improving the overall safety performance of the battery.

[0010] Further, R1 is selected from hydrogen, halogen, substituted or unsubstituted C1-C3 alkyl, substituted or unsubstituted C2-C3 alkenyl, substituted or unsubstituted C2-C3 alkynyl, substituted or unsubstituted C6-C12 aromatic, substituted or unsubstituted C1-C3 alkylcyano, substituted or unsubstituted C2-C4 ester, or substituted or unsubstituted C1-C3 alkylamino; or R1 is selected from hydrogen, halogen, C1-C3 alkyl, C2-C3 alkenyl, C2-C3 alkynyl, C1-C3 alkylcyano, C2-C4 ester, or C1-C3 alkylamino; or R1 is selected from hydrogen, fluorine atom, methyl, ethyl, vinyl, ethynyl, cyanomethyl, cyanoethyl, methyl ester, ethyl ester, methylamino, or ethylamino. The above conditions are conducive to further enhancing the chemical stability of quinine ring additives and the complexing ability of hydrofluoric acid, effectively inhibiting the erosion effect of hydrofluoric acid on the positive and negative electrode interface film, thereby significantly reducing the gas generation rate during long-term battery cycling and improving the overall safety and cycle life of the battery.

[0011] Furthermore, quinine-based additives include one or more of the following compounds, which can effectively reduce the rate of side reaction gas generation during long-term battery cycling, thereby achieving simultaneous improvement in battery life and safety.

[0012]

[0013] Furthermore, the lithium salt accounts for 10-20% of the electrolyte by weight; and / or the lithium salt includes lithium hexafluorophosphate and / or lithium bisfluorosulfonylimide. These lithium salts not only possess excellent electrochemical stability and conductivity, but also synergistically work with quinine-based additives to improve gas generation in the battery.

[0014] Furthermore, the lithium salt accounts for 12-18% of the electrolyte by weight; and / or the lithium salt includes lithium hexafluorophosphate and lithium bisfluorosulfonylimide, with a weight ratio of lithium hexafluorophosphate to lithium bisfluorosulfonylimide of (30-90):(10-70). These conditions are beneficial for further optimizing the conductivity and stability of the electrolyte, enabling the battery to operate efficiently over a wide temperature range, while suppressing the occurrence of side reactions.

[0015] Furthermore, the film-forming additive accounts for 1-6% of the electrolyte by weight; and / or the film-forming additive is selected from one or more of carbonates, sulfonates, phosphates, tris(trimethylsilane)borate, vinyl sulfate, hexamethylene diisocyanate, adiponitrile, hexanetrionitrile, tetravinylsilane, hexafluorocyclotriphosphazene, toluenesulfonyl isocyanate, and supplementary lithium salts; and / or the organic solvent includes cyclic esters and chain esters. These conditions facilitate the synergistic effect of the film-forming additive and quinine-based additives to effectively inhibit the erosion of the positive and negative electrode interface films by hydrofluoric acid, thereby significantly slowing down the gas generation rate caused by interface film rupture during battery cycling.

[0016] Further, the film-forming additive accounts for 2-4% of the electrolyte by weight; and / or the carbonate includes one or more of vinylene carbonate, ethylene carbonate, and fluoroethylene carbonate; and / or the sulfonate includes one or more of 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, and methyl disulfonate; and / or the phosphate includes one or more of triargyl phosphate, triallyl phosphate, triargyl phosphate, and tris(trimethylsilane) phosphate; and / or supplemental lithium. The salt includes one or more of lithium difluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium bis(oxalate borate), lithium difluorobis(oxalate phosphate), and lithium tetrafluorooxalate phosphate; and / or cyclic esters include one or more of ethylene carbonate, propylene carbonate, and fluoroethylene carbonate; and / or chain esters include one or more of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; and / or the weight ratio of cyclic esters to chain esters is (10~30):(70~90). These conditions are beneficial for promoting the effective formation of the positive and negative electrode interface film while further reducing the increase in electrolyte viscosity and cost that may result from excessive additives, forming a stable protective film on the electrode surface, significantly inhibiting solvent decomposition, and reducing gas production.

[0017] Furthermore, the quinine ring additive accounts for 0.1% to 1% of the electrolyte by weight; and / or the quinine ring additive includes , and One or more of the following: Formula 1 lithium salt includes lithium hexafluorophosphate and lithium difluorosulfonylimide in a weight ratio of (70~90):(10~30), and the lithium salt accounts for 14~16% of the electrolyte by weight; it includes lithium difluorophosphate, lithium difluorooxalate borate, a third additive, and a fourth additive in a weight ratio of 1:(0.5~1):(0.5~1):(0.2~0.5); wherein the third additive includes one or more of vinylene carbonate, fluoroethylene carbonate, and vinyl sulfate; and / or the fourth additive includes one or more of 1,3-propanesulfonate lactone, triargyl phosphate, and methyl disulfonate. These conditions enable the formation of a more stable protective film inside the battery, significantly reducing the continuous corrosion of the positive and negative electrode interface film by hydrofluoric acid.

[0018] According to another aspect of the present invention, a secondary battery is provided, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is the electrolyte described above that can reduce gas production, thereby achieving a comprehensive improvement in battery performance and lifespan and enhanced safety. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0020] Figure 1 The NMR spectrum of the quinine ring additive according to Example 1 of the present invention is shown. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] As described in the background section of this invention, existing lithium-ion batteries suffer from excessive gas production, leading to short battery life and poor safety performance. To address these issues, in a typical embodiment of this invention, an electrolyte that reduces gas production is provided, comprising an organic solvent, a lithium salt, a film-forming additive, and a quinine-based additive.

[0023] The electrolyte of this invention incorporates quinine-based additives. These additives effectively complex hydrofluoric acid generated inside the battery, weakening its activity and significantly slowing down the structural degradation rate of the positive and negative electrode interface films during cycling. The presence of quinine-based additives reduces the continuous corrosion of the interface film by hydrofluoric acid, preventing the exposure of active sites due to interface film rupture and reducing the side reaction rate of solvent decomposition gas generation. Therefore, even in the later stages of long-term battery cycling, a low gas generation rate can be maintained, effectively preventing battery swelling, greatly reducing the safety hazards of casing cracking and leakage, and improving the overall safety and cycle stability of cylindrical lithium-ion batteries. This significantly improves battery cycle life and operational safety without sacrificing battery performance, meeting the needs of cylindrical lithium-ion batteries in high-energy-density and long-life applications.

[0024] In a preferred embodiment, the quinine ring additive accounts for 0.01~10% of the electrolyte by weight; and / or the quinine ring additive has the structure shown in general formula (1):

[0025] (1);

[0026] R1 is selected from hydrogen, halogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkynyl, substituted or unsubstituted C6-C12 aryl, substituted or unsubstituted C1-C6 alkylcyano, substituted or unsubstituted C2-C6 ester, or substituted or unsubstituted C1-C6 alkylamino.

[0027] When the weight percentage of quinine ring additives in the electrolyte is within the above-mentioned range, it helps to precisely control the internal chemical environment of the electrolyte, effectively balance the activity and efficiency of the additives, and thus significantly reduce the gas generation rate without sacrificing the basic performance of the battery, thereby enhancing the safety and extending the service life of the battery. Among them, quinine ring additives have the structure shown in general formula (1). The R1 group assists the core structure to enhance the hydrofluoric acid capture ability, which can effectively inhibit the erosion of the positive and negative electrode interface film by hydrofluoric acid. Even during long-term cycling, it can maintain the structural integrity of the interface film, significantly reduce the gas generation rate of solvent side reactions caused by film rupture, thereby reducing the sharp increase in internal pressure of the battery, effectively reducing the occurrence of battery swelling, and improving the overall safety performance of the battery. The above-mentioned quinine ring additives can exert significant effects at a low addition amount and are suitable for large-scale industrial production.

[0028] To further enhance the chemical stability of quinine ring additives and their complexing ability with hydrofluoric acid, effectively suppress the erosion effect of hydrofluoric acid on the positive and negative electrode interface films, thereby significantly reducing the gas generation rate during long-term battery cycling and improving the overall safety and cycle life of the battery, in a preferred embodiment, R1 is selected from hydrogen, halogen, substituted or unsubstituted C1-C3 alkyl, substituted or unsubstituted C2-C3 alkenyl, substituted or unsubstituted C2-C3 alkynyl, substituted or unsubstituted C6-C12... The aromatic group, substituted or unsubstituted C1-C3 alkylcyano group, substituted or unsubstituted C2-C4 ester group, or substituted or unsubstituted C1-C3 alkylamino group; or R1 is selected from hydrogen, halogen, C1-C3 alkyl, C2-C3 alkenyl, C2-C3 alkynyl, C1-C3 alkylcyano, C2-C4 ester group, or C1-C3 alkylamino group; or R1 is selected from hydrogen, fluorine atom, methyl, ethyl, vinyl, ethynyl, cyanomethyl, cyanoethyl, methyl ester, ethyl ester, methylamino, or ethylamino.

[0029] The aforementioned R1 group not only enhances the function of the film-forming additive, but also forms a dynamic equilibrium system inside the battery. The quinine ring additive continuously consumes the hydrofluoric acid produced by the decomposition of the electrolyte, preventing it from damaging the film formation at the positive and negative electrode interfaces. Even in the later stages of battery cycling, the interfacial film can maintain its structural integrity, reduce the direct contact between solvent molecules and active sites, and thus inhibit further side reactions and gas generation.

[0030] For similar reasons, most preferably, in a preferred embodiment, the quinine ring additive includes one or more of the following compounds, which can effectively reduce the rate of side reaction gas generation during long-term battery cycling, thereby achieving simultaneous improvement in battery life and safety.

[0031]

[0032] In a preferred embodiment, the lithium salt accounts for 10-20% of the electrolyte by weight; and / or the lithium salt includes lithium hexafluorophosphate and / or lithium bisfluorosulfonylimide. This proportion of lithium salt in the electrolyte is beneficial for ensuring good conductivity while preventing excessive interfacial film growth or increased electrolyte viscosity due to excessively high lithium salt concentration, which could negatively impact the battery's charge / discharge efficiency. Furthermore, the aforementioned lithium salt not only possesses excellent electrochemical stability and conductivity but also works synergistically with quinine-based additives to improve gas generation in the battery.

[0033] To further optimize the conductivity and stability of the electrolyte, enabling the battery to operate efficiently over a wide temperature range while suppressing side reactions, in a preferred embodiment, the lithium salt accounts for 12-18% of the electrolyte by weight; and / or the lithium salt includes lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, with a weight ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide of (30-90):(10-70), preferably (50-90):(10-50). This specific proportion of lithium salt can improve the ionic conductivity of the electrolyte, promoting rapid migration of lithium ions within the battery, thereby enhancing the overall battery performance. Simultaneously, limiting the proportion of lithium bis(fluorosulfonyl)imide can maintain good electrochemical performance while mitigating its potential aluminum foil corrosion effect, reducing negative impacts on quinine ring additives and other components, and further extending the battery's lifespan.

[0034] In a preferred embodiment, the film-forming additive accounts for 1-6% of the weight of the electrolyte; and / or the film-forming additive is selected from one or more of carbonates, sulfonates, phosphates, tris(trimethylsilane)borate, vinyl sulfate, hexamethylene diisocyanate, adiponitrile, hexanetrionitrile, tetravinylsilane, hexafluorocyclotriphosphazene, toluenesulfonyl isocyanate, and supplementary lithium salts; and / or the organic solvent includes cyclic esters and chain esters.

[0035] Film-forming additives and quinine-based additives can synergistically inhibit the erosion of the positive and negative electrode interfacial films by hydrofluoric acid, thereby significantly slowing down the gas generation rate caused by interfacial film rupture during battery cycling. The preferred weight percentage of film-forming additives in the electrolyte is within the range described above, providing a sufficient concentration to form a stable solid electrolyte interfacial (SEI) film while reducing the increase in electrolyte viscosity due to excessive addition, maintaining good ion transport efficiency. These types of film-forming additives not only enhance the corrosion resistance of the SEI film but also promote efficient repair of the interfacial film, improving the stability and durability of the battery under long-term cycling. Organic solvents include high-dielectric-constant cyclic esters and low-viscosity chain esters. Cyclic esters, due to their high dielectric constant, facilitate lithium salt dissolution and ion conduction; chain esters, due to their low viscosity, improve electrolyte wettability and promote uniform electrochemical reactions.

[0036] To promote the effective formation of the positive and negative electrode interface film while further reducing the increase in electrolyte viscosity and cost that may result from excessive additives, and to form a stable protective film on the electrode surface, significantly inhibiting solvent decomposition and reducing gas generation, in a preferred embodiment, the film-forming additive accounts for 2-4% of the electrolyte by weight; and / or the carbonate includes one or more of vinylene carbonate, ethylene ethylene carbonate, and fluoroethylene carbonate; and / or the sulfonate includes one or more of 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, and methyl disulfonate; and / or the phosphate includes triphosphate. One or more of propargyl ester, triallyl phosphate, triargyl phosphate, and tris(trimethylsilane) phosphate; and / or supplemental lithium salts including lithium difluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium bis(oxalate borate), lithium difluorobis(oxalate phosphate), and lithium tetrafluorooxalate phosphate; and / or cyclic esters including one or more of ethylene carbonate, propylene carbonate, and fluoroethylene carbonate; and / or chain esters including one or more of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; and / or the weight ratio of cyclic esters to chain esters is (10~30):(70~90).

[0037] The aforementioned organic solvent system enables the electrolyte to possess both good dielectric constant and low viscosity characteristics, promoting efficient lithium-ion transport between the positive and negative electrodes. Meanwhile, cyclic esters typically account for 5-50% of the organic solvent in lithium-ion battery electrolytes. Considering the difficulty of electrolyte wetting in cylindrical batteries, a low-viscosity electrolyte is beneficial for improving electrolyte wettability. Therefore, it is preferable that the cyclic esters account for 10-30% of the organic solvent in the electrolyte to balance the wettability of the electrolyte and the gas generation control requirements of the battery, thereby achieving dual optimization of battery performance and safety.

[0038] In some embodiments, the organic solvent includes ethylene carbonate and dimethyl carbonate in a weight ratio of 20:80; the organic solvent includes ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate in a weight ratio of 15:70:15; the organic solvent includes fluoroethylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate in a weight ratio of 10:10:75:5.

[0039] In a preferred embodiment, the quinine ring additive accounts for 0.1-1% of the weight of the electrolyte; and / or the quinine ring additive includes... , and One or more of the following: lithium salts include lithium hexafluorophosphate and lithium difluorosulfonylimide, with a weight ratio of (70~90):(10~30), and the lithium salt accounts for 14~16% of the electrolyte by weight; film-forming additives include lithium difluorophosphate, lithium difluorooxalate borate, a third additive, and a fourth additive, with a weight ratio of 1:(0.5~1):(0.5~1):(0.2~0.5); wherein the third additive includes one or more of vinylene carbonate, fluoroethylene carbonate, and vinyl sulfate; and / or the fourth additive includes one or more of 1,3-propanesulfonate lactone, triargyl phosphate, and methylene disulfonate.

[0040] The above conditions enable the formation of a more stable protective film inside the battery, significantly reducing the continuous corrosion of the positive and negative electrode interface films by hydrofluoric acid. The aforementioned quinine-based additives exhibit higher hydrofluoric acid capture efficiency, while the high dielectric constant cyclic esters help improve the electrolyte conductivity, and the low viscosity chain esters ensure good wettability. The presence of the lithium salt mixture balances the chemical stability and conductivity of the electrolyte. The film-forming additives work synergistically to create a corrosion-resistant environment that inhibits side reactions. By rapidly and persistently capturing and neutralizing hydrofluoric acid, the amount of gas generated by side reactions during battery cycling can be effectively reduced, slowing down the rate of interface film damage. This maintains the battery's stability under long-term use conditions, effectively reducing the corrosion of the positive and negative electrode interface films by hydrofluoric acid, thereby inhibiting battery gas production and improving battery safety and cycle life.

[0041] In another typical embodiment of the present invention, a secondary battery is also provided, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is the gas-reducing electrolyte described above. By employing the electrolyte with the specific composition of the present invention, the problem of battery swelling caused by gas generation from side reactions during long-term cycling of high-nickel positive and high-silicon negative electrodes can be solved, achieving a comprehensive improvement in battery performance and lifespan, as well as enhanced safety. In some embodiments, the secondary battery includes a cylindrical battery.

[0042] Typical, but not limiting, quinine ring additives constitute a weight percentage of 0.01%, 0.1%, 1%, 2%, 5%, 8%, 10% of the electrolyte, or a range of any two of these values.

[0043] Typical, but not limiting, lithium salts constitute a weight percentage of 10%, 12%, 15%, 18%, 20% of the electrolyte, or a range of any two of these values.

[0044] Typical, but not limiting, film-forming additives constitute a weight percentage of 1%, 2%, 3%, 4%, 5%, 6% of the electrolyte, or a range of any two of these values.

[0045] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0046] Example 1

[0047] The organic solvent, lithium salt, film-forming additive, and quinine ring additive were mixed according to Tables 1 and 2 to obtain the electrolyte.

[0048] Examples 2 to 6

[0049] The difference from Example 1 is that the types of organic solvents, lithium salts, film-forming additives and quinine ring additives are different, as detailed in Tables 1 and 2.

[0050] Examples 7 to 10

[0051] The difference from Example 1 is that the amounts of organic solvent, lithium salt, film-forming additive and quinine ring additive are different, as detailed in Table 2.

[0052] Comparative Example 1

[0053] The difference from Example 1 is that no quinine cyclic additives were added.

[0054] Performance testing:

[0055] (1) Battery fabrication: High-nickel ternary NCM811 material was used as the positive electrode, artificial graphite as the negative electrode, and a 9μm (base film) + 2μm single-sided ceramic-coated PE separator was used as the separator. The electrolytes of the above examples and comparative examples were assembled into lithium-ion batteries for testing. The following analysis and testing were carried out, and the results are shown in Table 3.

[0056] (2) Battery capacity and initial efficiency: After the battery is formed, it is aged at 45°C for 24 hours, then charged to 4.25V with constant current and constant voltage at 0.333C, with a cutoff current of 0.05C. After resting for 30 minutes, it is discharged to 2.75V with constant current at 0.333C. The initial discharge capacity and initial efficiency are calculated.

[0057] (3) High-temperature storage gas production: The 5Ah soft-pack battery was charged to 100% SOC, and the initial volume of the battery was tested by the water displacement method; then it was placed in a 70℃ oven for 15 days, and the volume of the battery after storage was tested. The difference between the volume after storage and the initial volume is the storage gas production.

[0058] (4) High temperature storage capacity retention rate: Charge the battery to 100% SOC, place it in a 55℃ oven for 30 days, and test the capacity retention rate before and after storage.

[0059] (5) High temperature cycle life test: At 45℃, a current of 1C / 1C is used to conduct a room temperature cycle test in the voltage range of 2.75~4.25V. After 500 cycles, the capacity retention rate is recorded.

[0060] Table 1

[0061]

[0062] Table 2

[0063]

[0064] Table 3

[0065]

[0066] The NMR spectrum of the quinine cyclic additive in Example 1 is shown below. Figure 1 .

[0067] Compared to the comparative example, the quinine-based additives in the examples had no significant impact on the battery's capacity and initial efficiency, but could significantly reduce gas generation during high-temperature storage, improving the battery's high-temperature storage and cycling performance. At high temperatures, lithium salts in the battery easily decompose to produce trace amounts of hydrofluoric acid, which corrodes the CEI film of the positive electrode and the SEI film of the negative electrode, leading to battery capacity loss. The tertiary nitrogen atoms of the quinine-based additives are rich in electrons and are weakly alkaline, capable of complexing with the hydrofluoric acid in the battery, reducing the activity of hydrofluoric acid in corroding the CEI and SEI films. Therefore, the examples with added quinine-based additives showed a significantly reduced gas generation compared to the comparative example without quinine-based additives, and both high-temperature cycling and high-temperature storage performance were improved.

[0068] As demonstrated in Examples 1 to 6, the combined use of lithium hexafluorophosphate and lithium difluorosulfonylimide results in lower high-temperature gas production compared to using only a single lithium salt. At high temperatures, lithium hexafluorophosphate decomposes more readily than lithium difluorosulfonylimide to produce hydrofluoric acid byproducts, while lithium difluorosulfonylimide corrodes aluminum foil more readily than lithium hexafluorophosphate. The combined use of these two materials synergistically leverages the passivating effect of lithium hexafluorophosphate on aluminum foil and the low hydrofluoric acid production characteristic of lithium difluorosulfonylimide, resulting in a superior effect.

[0069] As demonstrated in Examples 1 and 7 to 10, a moderate lithium salt content is beneficial for providing sufficient lithium-ion transport medium to improve cycle performance, while minimizing lithium salt decomposition side reactions, hydrofluoric acid production, and gas generation, thus improving high-temperature storage performance. A moderate content of film-forming additives is beneficial for forming dense SEI and CEI films, improving thermal stability and high-temperature storage performance. A moderate content of film-forming additives also helps reduce the erosion of SEI and CEI films by harmful substances generated from side reactions, reducing gas generation and improving high-temperature performance. A moderate content of quinine-based additives provides sufficient hydrofluoric acid complexing capacity, reducing gas generation, improving high-temperature storage performance, and maintaining low battery costs.

[0070] Furthermore, it can be seen that the overall effect is better when all process parameters are within the preferred range of the present invention.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electrolyte that can reduce gas production, characterized in that, This includes organic solvents, lithium salts, film-forming additives, and quinine ring additives.

2. The electrolyte for reducing gas production according to claim 1, characterized in that, The quinine cyclic additive accounts for 0.01~10% of the weight of the electrolyte; and / or The quinine ring additive has the structure shown in general formula (1): （1）； R1 is selected from hydrogen, halogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkynyl, substituted or unsubstituted C6-C12 aryl, substituted or unsubstituted C1-C6 alkylcyano, substituted or unsubstituted C2-C6 ester, or substituted or unsubstituted C1-C6 alkylamino.

3. The electrolyte for reducing gas production according to claim 2, characterized in that, R1 is selected from hydrogen, halogen, substituted or unsubstituted C1-C3 alkyl, substituted or unsubstituted C2-C3 alkenyl, substituted or unsubstituted C2-C3 alkynyl, substituted or unsubstituted C6-C12 aryl, substituted or unsubstituted C1-C3 alkylcyano, substituted or unsubstituted C2-C4 ester, or substituted or unsubstituted C1-C3 alkylamino; or R1 is selected from hydrogen, halogen, C1-C3 alkyl, C2-C3 alkenyl, C2-C3 alkynyl, C1-C3 alkylcyano, C2-C4 ester, or C1-C3 alkylamino; or R1 is selected from hydrogen, fluorine, methyl, ethyl, vinyl, ethynyl, cyanomethyl, cyanoethyl, methyl ester, ethyl ester, methylamino, or ethylamino.

4. The electrolyte with reduced gas production according to any one of claims 1 to 3, characterized in that, The quinine-based cyclic additives include one or more of the following compounds:

5. The electrolyte with reduced gas production according to any one of claims 1 to 3, characterized in that, The lithium salt accounts for 10-20% of the weight of the electrolyte; and / or The lithium salt includes lithium hexafluorophosphate and / or lithium difluorosulfonylimide.

6. The electrolyte for reducing gas production according to claim 5, characterized in that, The lithium salt accounts for 12-18% of the weight of the electrolyte; and / or The lithium salt includes lithium hexafluorophosphate and lithium difluorosulfonylimide, and the weight ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is (30~90):(10~70).

7. The electrolyte with reduced gas production according to any one of claims 1 to 3, characterized in that, The film-forming additive accounts for 1-6% of the weight of the electrolyte; and / or The film-forming additive is selected from one or more of carbonates, sulfonates, phosphates, tris(trimethylsilane)borate, vinyl sulfate, hexamethylene diisocyanate, adiponitrile, hexanetrionitrile, tetravinylsilane, hexafluorocyclotriphosphonium, toluenesulfonyl isocyanate, and supplementary lithium salts; and / or The organic solvents include cyclic esters and chain esters.

8. The electrolyte for reducing gas production according to claim 7, characterized in that, The film-forming additive accounts for 2-4% of the weight of the electrolyte; and / or The carbonate includes one or more of vinylene carbonate, ethylene ethylene carbonate, and fluoroethylene carbonate; and / or The sulfonate comprises one or more of 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, and methyl disulfonate methylene ester; and / or The phosphate ester includes one or more of triargyl phosphate, triallyl phosphate, and tris(trimethylsilane) phosphate; and / or The supplemental lithium salt includes one or more of lithium difluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium bis(oxalate borate), lithium difluorobis(oxalate phosphate), and lithium tetrafluorooxalate phosphate; and / or The cyclic esters include one or more of ethylene carbonate, propylene carbonate, and fluoroethylene carbonate; and / or The chain ester includes one or more of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; and / or The weight ratio of the cyclic ester to the chain ester is (10~30):(70~90).

9. The electrolyte with reduced gas production according to any one of claims 1 to 3, characterized in that, The quinine cyclic additive accounts for 0.1% to 1% of the weight of the electrolyte; and / or the quinine cyclic additive includes... , and One or more; The lithium salt comprises lithium hexafluorophosphate and lithium difluorosulfonylimide in a weight ratio of (70~90):(10~30), and the lithium salt accounts for 14~16% of the weight of the electrolyte. The film-forming additives include lithium difluorophosphate, lithium difluorooxalate borate, a third additive, and a fourth additive, in a weight ratio of 1:(0.5~1):(0.5~1):(0.2~0.5); wherein the third additive includes one or more of vinylene carbonate, fluoroethylene carbonate, and vinyl sulfate; and / or the fourth additive includes one or more of 1,3-propanesulfonate lactone, triargyl phosphate, and methylene disulfonate.

10. A secondary battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The electrolyte is any one of the electrolytes described in claims 1 to 9 that can reduce gas production.

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