Electrolyte and use thereof

Abstract

Provided in the present application are an electrolyte and the use thereof. The electrolyte comprises a first additive as shown in formula 1, vinylene carbonate and a boron-containing compound. Applying the electrolyte to a battery can not only reduce the content of PF5 and HF in the electrolyte, but can also improve the electrochemical performance of the lithium-ion battery.

Description

An electrolyte and its application

[0001] This application requests priority to the Chinese patent application filed with the China Patent Office on November 10, 2023, with application number 202311497329.9 and invention name “A kind of electrolyte and its application”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to an electrolyte and its application, belonging to the field of energy technology. Background Art

[0003] The electrolyte of a lithium-ion battery is generally composed of a lithium salt, a solvent, and additives. However, some lithium salts have poor thermal stability and easily decompose at high temperatures to form phosphorus pentafluoride (PF5), which then reacts with trace impurities in the electrolyte to form hydrofluoric acid (HF). PF5, as a strong Lewis acid, catalyzes the decomposition of carbonate-based solvents in the electrolyte, exacerbating gassing in lithium-ion batteries. HF, on the other hand, corrodes the cathode material, causing its structure to collapse and rapidly reducing the capacity of the lithium-ion battery.

[0004] In order to reduce the content of PF5 and HF in the electrolyte, CN113711413A discloses a sulfonyl / sulfonate compound containing an imidazole group. The nitrogen-containing five-membered heterocyclic ring in the compound has Lewis basicity and can form a complex with PF5, thereby reducing the Lewis acidity and reactivity of PF5, and thus effectively inhibiting its reaction with trace impurities in the electrolyte to form HF and increase the color. However, the nitrogen-containing five-membered heterocyclic ring in the sulfonyl / sulfonate compound containing an imidazole group can promote the ring-opening decomposition reaction of cyclic carbonate solvents (especially ethylene carbonate), thereby causing gas production in lithium-ion batteries and affecting the storage performance of lithium-ion batteries under high temperature conditions.

[0005] Therefore, it is necessary to provide an electrolyte with low PF5 and HF content and which can improve the electrochemical performance of lithium-ion batteries.

[0006] Summary of the Invention

[0007] The present application provides an electrolyte, which, when used in a lithium-ion battery, can not only reduce the content of PF5 and HF in the electrolyte, but also improve the electrochemical performance of the lithium-ion battery.

[0008] The present application also provides a lithium-ion battery containing the above-mentioned electrolyte, so that the lithium-ion battery has relatively excellent electrochemical performance.

[0009] [Corrected 08.07.2025 in accordance with Rule 26] The present application provides an electrolyte solution comprising a first additive represented by Formula 1, vinylene carbonate, and a boron-containing compound;

[0010] In the electrolyte as described above, based on the total mass of the electrolyte, the mass percentage W1 of the first additive satisfies: 0<W1≤1%.

[0011] The electrolyte as described above, wherein, based on the total mass of the electrolyte, the mass percentage W2 of the vinylene carbonate satisfies: 0<W2≤3%.

[0012] The electrolyte as described above, wherein, based on the total mass of the electrolyte, the mass percentage W3 of the boron-containing compound satisfies: 0<W3≤2%.

[0013] In the electrolyte as described above, the boron-containing compound is selected from boron-containing lithium salts and / or borate ester compounds.

[0014] In the electrolyte as described above, the boron-containing lithium salt is selected from at least one of lithium tetrafluoroborate, lithium bis(oxalatoborate) and lithium difluorooxalatoborate; and / or the borate ester compound is selected from trimethyl borate and / or tris(trimethylsilyl)borate.

[0015] The electrolyte as described above, wherein, in the electrolyte, the mass percentage content W1 of the first additive, the mass percentage content W2 of the vinylene carbonate, and the mass percentage content W3 of the boron-containing compound satisfy the following relationship:

[0016] W1 / W2=(0.16-2):1;

[0017] W1 / W3=(0.5-2.5):1.

[0018] The electrolyte as described above, wherein the electrolyte further comprises lithium hexafluorophosphate.

[0019] The electrolyte as described above, wherein the water content in the electrolyte is ≤20ppm and the acidity is ≤50ppm.

[0020] The present application provides a lithium-ion battery, wherein the lithium-ion battery includes the electrolyte as described above.

[0021] The electrolyte composition of the present application is simple. When used in lithium-ion batteries, the content of PF5 and HF in the electrolyte can be reduced, the gas production and capacity decay of the lithium-ion battery during the charge and discharge process can be reduced, and the electrochemical performance of the lithium-ion battery (for example, high-temperature cycle performance and low-temperature cycle performance) can be improved.

[0022] The lithium-ion battery of the present application includes the aforementioned electrolyte, so the lithium-ion battery is not prone to gas generation during the charge and discharge process, and the electrolyte is not prone to corroding the positive electrode material, and the lithium-ion battery has excellent electrochemical properties. DETAILED DESCRIPTION

[0023] To make the purpose, technical solutions, and advantages of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0024] [Corrected 08.07.2025 in accordance with Rule 26] In view of this, a first aspect of the present application provides an electrolyte comprising a first additive represented by Formula 1, vinylene carbonate (VC), and a boron-containing compound;

[0025] In the present application, the first additive, vinylene carbonate, and the boron-containing compound can be any of the commonly used first additives, vinylene carbonate, and boron-containing compounds in the art. The first additive, vinylene carbonate, and the boron-containing compound can be purchased commercially or prepared by a commonly used preparation method in the art.

[0026] In the electrolyte of the present application, the first additive has Lewis alkalinity, which can inhibit the reaction of PF5 generated by the decomposition of lithium salts with trace impurities in the electrolyte to produce HF, and inhibit the reaction of PF5 generated by the decomposition of lithium salts with trace impurities in the electrolyte to cause the chromaticity of the electrolyte to increase; and the first additive in the electrolyte will form an SEI film rich in lithium alkyl sulfonate and inorganic sulfide components during the charge and discharge process of the lithium-ion battery, thereby improving the thermal stability of the SEI film and thereby improving the high-temperature performance of the lithium-ion battery;

[0027] Compared to ethylene carbonate (EC), VC in the electrolyte has a higher reactivity with Lewis bases and can preferentially bind to the imidazole groups on the first additive, thereby inhibiting the imidazole groups of the first additive from catalyzing the ring-opening decomposition of EC and suppressing the phenomenon of bulging in lithium-ion batteries. VC also reacts with the imidazole groups of the first additive to form a denser SEI film, further inhibiting side reactions at the interface between the electrode and the electrolyte at high temperatures, thereby improving the high-temperature storage and high-temperature cycling performance of lithium-ion batteries.

[0028] The central boron atom of the boron-containing compound is electron-deficient, which can improve the problems of reduced lithium ion transport performance and increased lithium ion battery impedance caused by the carbonate component in the dense SEI film produced by VC regulation, thereby improving the low-temperature performance of lithium ion batteries. In addition, the electron-deficient nature of the boron atom makes the boron-containing compound Lewis acidic. The Lewis acidic boron-containing compound easily combines with the Lewis basic first additive, weakening the Lewis basicity of the imidazole group on the first additive, further inhibiting the imidazole group of the first additive from catalyzing the ring-opening decomposition of EC, and inhibiting the gas production of the lithium ion battery. At the same time, the boron atom on the boron-containing compound can also interact with the oxygen on the carbon-oxygen double bond in the EC molecule, which can stabilize the EC.

[0029] Therefore, the electrolyte comprising the first additive, VC and the boron-containing compound in the present application can not only improve the high-temperature storage and high-temperature cycle performance of the lithium-ion battery, but also enable it to have good low-temperature performance.

[0030] It can be understood that the content of the first additive, VC and boron-containing compound in the electrolyte will have a crucial impact on the comprehensive performance of the electrolyte. Therefore, the present application can further improve the comprehensive performance of the electrolyte by further selecting the content of the first additive, VC and boron-containing compound in the electrolyte.

[0031] In some embodiments of the present application, when the mass percentage W1 of the first additive satisfies the following conditions, based on the total mass of the electrolyte: 0 < W1 ≤ 1%, the reaction of PF5 generated by the decomposition of the lithium salt with trace impurities in the electrolyte can be effectively suppressed, and a SEI film with improved thermal stability can be formed, thereby improving the high-temperature performance of the lithium-ion battery. Furthermore, when 0.1 ≤ W1 ≤ 0.5%, gassing of the lithium-ion battery can be avoided, further improving the high-temperature performance of the lithium-ion battery.

[0032] In some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage content W2 of vinylene carbonate satisfies: 0<W2≤3%. Further, 0.3≤W2≤2.5%.

[0033] When the content of vinylene carbonate is within the above range, it is possible to better suppress the occurrence of gas production by the catalytic decomposition of EC by the imidazole group of the first additive while ensuring that the carbonate content in the SEI film is moderate and does not affect the low-temperature performance of the lithium-ion battery, thereby avoiding obvious expansion of the lithium-ion battery during use.

[0034] In some embodiments of the present application, based on the total mass of the electrolyte, when the mass percentage W3 of the boron-containing compound satisfies the following conditions: 0<W3≤2%, the transmission of lithium ions can be further enhanced, the problem of increased impedance caused by VC film formation can be alleviated, and the low-temperature performance of the lithium-ion battery can be improved. In addition, the VC can assist in inhibiting the decomposition of EC catalyzed by the imidazole group on the first additive, thereby inhibiting the gas production of the lithium-ion battery.

[0035] Furthermore, the boron-containing compound is selected from boron-containing lithium salts and / or borate ester compounds.

[0036] The boron-containing lithium salt may be a boron-containing lithium salt commonly used in the art, for example, the boron-containing lithium salt is selected from at least one of lithium tetrafluoroborate, lithium bis(oxalatoborate) and lithium difluorooxalatoborate.

[0037] The borate compound can be a borate compound commonly used in the art, for example, the borate compound is selected from trimethyl borate and / or tris(trimethylsilyl)borate.

[0038] In the present application, when the boron-containing compound is a boron-containing lithium salt, the boron-containing lithium salt can also participate in the formation of the SEI film, introduce lithium ions into the SEI film, improve the lithium ion transport of the SEI film, and thereby improve the electrochemical performance of the lithium-ion battery, especially the cycle performance and low-temperature discharge performance of the lithium-ion battery.

[0039] When the boron-containing compound is selected from borate compounds, a boron-containing SEI film can be formed to improve the ionic conductivity of the lithium-ion battery. In addition, the borate compounds selected in this application have a simple structure and produce fewer by-products in the reaction, which helps to further improve the electrochemical performance of the electrolyte.

[0040] In some embodiments of the present application, in the electrolyte, the mass percentage W1 of the first additive, the mass percentage W2 of vinylene carbonate, and the mass percentage W3 of the boron-containing compound satisfy the following relationship: W1 / W2 = (0.16-2): 1; W1 / W3 = (0.5-2.5): 1.

[0041] In the present application, when the mass percentages of the first additive, VC and the boron-containing compound in the electrolyte respectively satisfy the above relationship, the first additive, VC and the boron-containing compound can further match each other to improve the overall performance of the lithium-ion battery.

[0042] In some embodiments of the present application, the electrolyte includes lithium hexafluorophosphate.

[0043] In the present application, when the electrolyte includes lithium hexafluorophosphate, the first additive, VC and boron-containing compound are matched with each other to reduce the content of phosphorus pentafluoride generated by lithium hexafluorophosphate at high temperature, and reduce the content of HF in the electrolyte, thereby improving the electrochemical performance of the lithium-ion battery.

[0044] It is understood that the electrolyte may further include at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(fluorosulfonyl)imide (LiFSI).

[0045] In the electrolyte, the sum of the mass percentages of lithium hexafluorophosphate, LiTFSI, and LiFSI may be 12.5%.

[0046] The electrolyte includes a solvent. The solvent may include a cyclic carbonate and a linear carbonate. The cyclic carbonate may be selected from at least one of ethylene carbonate, propylene carbonate, and fluoroethylene carbonate, and the linear carbonate may be selected from at least one of diethyl carbonate, dimethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate. Based on the total mass of the solvent, the mass percentage of the cyclic carbonate is 10-30%, and the mass percentage of the linear carbonate is 70-90%.

[0047] In some embodiments of the present application, when the water content in the electrolyte is ≤20 ppm and the acidity is ≤50 ppm, the obtained electrolyte can further improve the electrochemical performance of the lithium-ion battery when applied to the lithium-ion battery.

[0048] A second aspect of the present application provides a lithium-ion battery, wherein the lithium-ion battery includes the above-mentioned electrolyte.

[0049] It can be understood that the lithium-ion battery of the present application includes a positive electrode sheet, a negative electrode sheet, a separator and an outer packaging.

[0050] The present application does not impose any particular limitations on the positive electrode sheet, and may be any common positive electrode sheet in the art. In some embodiments, the positive electrode active material in the positive electrode sheet may be at least one of lithium cobalt oxide, lithium iron phosphate, and a ternary material. Furthermore, the positive electrode active material may be a ternary material.

[0051] The present application does not impose any particular limitations on the negative electrode sheet, and may be any common negative electrode sheet in the art. In some embodiments, the negative electrode active material in the negative electrode sheet may be selected from at least one of artificial graphite, natural graphite, lithium titanate, silicon, silicon-carbon, silicon-oxygen, and a silicon-metal compound. Furthermore, the negative electrode active material may be silicon-carbon and / or silicon-oxygen.

[0052] In particular, when high-nickel ternary positive electrode materials and silicon-carbon negative electrode materials are used together to prepare lithium-ion batteries, the advantages of 4680 batteries can be fully utilized.

[0053] The lithium-ion battery of the present application includes the aforementioned electrolyte, so the lithium-ion battery is not prone to gas generation during the charge and discharge process, and the electrolyte is not prone to corroding the positive electrode material, and the lithium-ion battery has excellent electrochemical properties.

[0054] The electrolyte of the present application and its application are described in detail below through specific examples. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0055] Example 1

[0056] The lithium-ion battery of this embodiment is prepared by a method comprising the following steps:

[0057] (1) Preparation of positive electrode sheet

[0058] The positive electrode active material NCM523, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black were mixed in a mass ratio of 96.5:2:1.5, and N-methylpyrrolidone (NMP) was added. The mixture was stirred under the action of a vacuum mixer until the raw materials were mixed into a positive electrode slurry with uniform fluidity to obtain a positive electrode slurry with a solid content of 70wt%;

[0059] The positive electrode slurry is evenly coated on both surfaces of a 7μm thick aluminum foil. After drying, it is rolled, trimmed, cut, slit, sheeted, welded, and then glued to the tabs to obtain a positive electrode sheet with a size of 55mm×600mm. The compacted density of the positive electrode active layer is 3.5g / cm 3 .

[0060] (2) Preparation of negative electrode sheet

[0061] Graphite, conductive carbon black, carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) were dispersed in deionized water at a mass ratio of 95:1.5:2:1.5 to form a negative electrode slurry (solid content of the negative electrode slurry was 49 wt%). The negative electrode slurry was coated on the upper and lower surfaces of a 9 μm thick copper foil and dried. The negative electrode sheet was then cold pressed, trimmed, cut, slit, produced, and welded to the tabs to obtain a 60 mm × 700 mm negative electrode sheet. The compacted density of the negative electrode material layer was 1.6 g / cm 3 .

[0062] (3) Preparation of electrolyte

[0063] In an argon-filled glove box (moisture <1 ppm, oxygen <1 ppm), ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) were uniformly mixed in a mass ratio of 3:2:5 to obtain a base solvent. Thoroughly dried lithium salt, a first additive, VC, and a boron-containing compound were quickly added to the base solvent to obtain an electrolyte. The mass percentages of the lithium salt, first additive, VC, and boron-containing compound, based on the total mass of the electrolyte, are shown in Table 1. The remainder was the base solvent.

[0064] The water content in the electrolyte was tested using the Karl Fischer moisture test method, and the testing instrument was a Swiss Metrohm moisture tester; the acidity of the electrolyte was tested using the triethylamine potentiometric titration method, and the testing instrument was a Swiss Metrohm potentiometric titrator.

[0065] (4) Preparation of lithium-ion batteries

[0066] The positive electrode sheet of step (1), the separator, and the negative electrode sheet of step (2) are stacked in sequence, with the separator being located between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet and the negative electrode sheet are isolated, and the positive electrode tab is connected to the positive electrode sheet, and the negative electrode tab is connected to the negative electrode sheet, to obtain a bare battery cell without liquid injection;

[0067] The bare battery cell is placed in an aluminum-plastic film outer packaging foil, and the positive and negative electrode tabs are led out from the inner space of the packaging bag to the outer space of the outer packaging foil. After drying at 80°C for 72 hours to remove moisture, the battery cell is heat-pressed and sealed to obtain a battery cell ready for liquid injection. The electrolyte from step (3) is injected into the dried battery cell, and the lithium-ion battery is produced through vacuum packaging, static standing, formation, shaping, and sorting processes.

[0068] The separator is a coated polyethylene separator with a thickness of 8 μm, wherein the coating is a boehmite coating with a thickness of 0.5 μm.

[0069] Examples 2-30, Comparative Examples 1-23

[0070] The compositions of the electrolytes of Examples 2-30 and Comparative Examples 1-23 are substantially the same as those of Example 1, with the differences shown in Table 1. When the values ​​of W1, W2, and W3 in the electrolyte change, the mass percentage of the base solvent changes accordingly, while the mass percentage of the lithium salt remains unchanged.

[0071] The electrolyte in Example 1 was replaced with the electrolytes in Example 2-30 and Comparative Example 1-23, respectively, to obtain the lithium ion batteries of Example 2-30 and Comparative Example 1-23, respectively.

[0072] Table 1

[0073] As can be seen from Table 1, the water content of the electrolyte in the embodiment of the present application and the comparative example is basically the same, and both can be used normally; when the electrolyte includes the first additive, the acidity of the obtained electrolyte is reduced. This is because the Lewis basicity of the imidazole ring in the first additive can combine with HF and PF5 in the electrolyte, thereby reducing the acidity in the electrolyte and improving the quality of the electrolyte.

[0074] Performance Testing

[0075] The following performance tests were performed on the lithium-ion batteries in the examples and comparative examples, and the test results are shown in Table 2.

[0076] 1) 25℃ 1.0C / 1.0C cycle test

[0077] At 25°C, charge at a constant current of 1.0C to 4.4V, charge at a constant voltage of 4.4V to a cutoff current of 0.05C, and then discharge the lithium-ion battery at a constant current of 1.0C to a voltage of 3.0V. The discharge capacity is recorded as C0. Repeat the charge and discharge steps until the capacity decays to 80% of C0, and record the number of cycles.

[0078] 2) 45℃ 1.0C / 1.0C cycle test

[0079] Charge at 45°C at a constant current of 1.0C to 4.4V, charge at a constant voltage to a cutoff current of 0.05C, and then discharge the lithium-ion battery at a constant current of 1.0C to a voltage of 3.0V. The discharge capacity is recorded as C1. Repeat the charge and discharge steps until the capacity decays to 80% of C1, and record the number of cycles.

[0080] 3) Performance test at 60℃ for 15 days

[0081] At 25°C, charge the lithium-ion battery to 4.4V at a constant current of 1.0C, charge it to a cutoff current of 0.05C at a constant voltage of 4.4V, and then discharge it at a constant current of 0.5C to a voltage of 3.0V. The discharge capacity is recorded as C2. Remove the lithium-ion battery and use a thickness tester to measure its initial thickness, which is T1. At 25°C, charge it to 4.4V at a constant current of 1.0C, charge it to a cutoff current of 0.05C at a constant voltage of 4.4V, and then transfer the lithium-ion battery to 60°C for 15 days. Use a thickness tester to measure its thickness after 15 days, which is T2. Then discharge the lithium-ion battery at a constant current of 1.0C, and record the discharge capacity as C3. After 15 days of storage at 60°C, the capacity retention rate = C3 / C2×100%, and the thickness expansion rate = 100%×(T2-T1) / T1.

[0082] 4) -20℃ low temperature discharge capacity retention test

[0083] At 25°C, charge the battery to 4.4V at a constant current of 1.0C, charge it to a cutoff current of 0.05C at a constant voltage of 4.4V, and then discharge the lithium-ion battery at a constant current of 0.5C to a voltage of 3.0V. The discharge capacity is recorded as C4. At -20°C, leave it for 4 hours, then discharge the lithium-ion battery at a constant current of 0.5C to a voltage of 3.0V. The discharge capacity is recorded as C5. The -20°C low-temperature discharge capacity retention rate = C5 / C4×100%.

[0084] Table 2

[0085] As can be seen from Table 2, the electrolyte of the embodiment of the present application, when applied to a lithium-ion battery, can further improve the room temperature cycle performance, high temperature cycle performance, and low temperature cycle performance of the lithium-ion battery.

[0086] Furthermore, it can be seen from Examples 1-5 that as the content of the boron-containing additive increases, the low-temperature performance of the lithium-ion battery gradually improves. This is because the central boron atom of the boron-containing compound is electron-deficient, which can improve the problem of reduced lithium ion transport performance and increased lithium ion battery impedance caused by the carbonate component in the dense SEI film produced by VC regulation, thereby improving the low-temperature performance of the lithium-ion battery.

[0087] It can be seen from Examples 5-8, Examples 9-11, and Examples 12-14 that when the mass ratio of the first additive to VC and the mass ratio of the first additive to the boron-containing compound in the electrolyte remain unchanged, as the mass percentage of each additive (the first additive, VC, and the boron-containing compound) increases, the electrochemical performance of the lithium-ion battery becomes increasingly excellent, proving that increasing each additive in equal proportion contributes to improving the electrochemical performance of the lithium-ion battery.

[0088] It can be seen from Examples 15-20 that as the VC content in the electrolyte increases, the high-temperature stability and high-temperature storage performance of the lithium-ion battery become better. The reason is that compared with ethylene carbonate (EC), the VC in the electrolyte has higher reactivity with Lewis bases and can preferentially combine with the imidazole groups on the first additive, thereby inhibiting the imidazole groups of the first additive from catalyzing the ring-opening decomposition of EC and inhibiting the occurrence of bulging in the lithium-ion battery; and VC reacts with the imidazole groups of the first additive to form a denser SEI film, further inhibiting the occurrence of side reactions at the interface between the electrode and the electrolyte at high temperatures, thereby improving the high-temperature storage and high-temperature cycle performance of the lithium-ion battery.

[0089] It can be seen from Examples 20-22 and Examples 23-24 that when the boron-containing compound is a boron-containing lithium salt, the obtained lithium-ion battery has more excellent electrochemical properties. The reason is that the boron-containing lithium salt can also participate in the formation of the SEI film, introduce lithium ions into the SEI film, and improve the lithium ion transport of the SEI film, thereby improving the electrochemical properties of the lithium-ion battery, especially the cycle performance and low-temperature discharge performance of the lithium-ion battery.

[0090] It can be seen from Examples 1-24 and Examples 25-27 that the comprehensive performance of the lithium-ion battery can be improved by specifically selecting the contents of the boron-containing compound, VC and the first additive in the electrolyte. The reason is that by further selecting the contents of the boron-containing compound, VC and the first additive in the electrolyte, the boron-containing compound, VC and the first additive in the electrolyte can be better matched, and the advantages of the boron-containing compound, VC and the first additive can be fully utilized to improve the comprehensive performance of the lithium-ion battery.

[0091] It can be seen from Examples 28-30 that the selection of different types of boron-containing compounds in the electrolyte can improve the overall performance of lithium-ion batteries. The reason is that the boron-containing compounds selected within the scope of this application can participate in the formation of the SEI film and improve the ionic conductivity of the lithium-ion battery.

[0092] It can be seen from Comparative Examples 2 and 3 that the use of the first additive alone leads to severe gas generation, which is attributed to the Lewis base-catalyzed solvent decomposition of the imidazole group thereof to generate gas.

[0093] It can be seen from Comparative Examples 4 and 5 that when VC is used alone, the high-temperature performance of the lithium-ion battery is good, but the low-temperature performance is poor. The reason is that although VC can form a long carbon chain SEI film through polymerization reaction, the SEI film will hinder the conduction of lithium ions.

[0094] It can be seen from Comparative Examples 6-10 that the use of boron-containing additives alone will not significantly improve the high-temperature cycling and high-temperature storage performance of lithium-ion batteries. The reason is that the electrode-electrolyte interface film formed by the boron-containing additives is discontinuous and has poor stability.

[0095] Comparative Examples 11-13 show that when the electrolyte contains only the first additive and VC, without the boron-containing compound, both the high-temperature and low-temperature performance of the lithium-ion battery are affected. As the second additive content decreases, the second additive is unable to suppress the degradation of the first additive, resulting in a decrease in the lithium-ion battery's high-temperature storage capacity retention and severe gassing. Increasing the second additive content increases impedance, affecting lithium ion transmission and resulting in poor low-temperature discharge performance.

[0096] Comparative Examples 14-18 show that combining VC and a boron-containing additive can alleviate the high impedance problem associated with VC film formation. However, due to the poor stability of boron-containing additives after film formation, it is not advisable to add too much. Only a small amount of boron-containing additive can be added to reduce impedance. Therefore, using only boron-containing additives to reduce impedance is effective, but far from sufficient for practical application.

[0097] It can be seen from Comparative Examples 19-23 that it is far from sufficient to merely use the boron-containing additive to suppress the Lewis alkalinity of the first additive, which can easily lead to poor high-temperature performance of the lithium-ion battery.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. [Corrected 08.07.2025 according to Rule 26] An electrolyte, characterized in that It includes a first additive shown in Formula 1, vinylene carbonate and a boron-containing compound; 2. The electrolyte according to claim 1, characterized in that Based on the total mass of the electrolyte, the mass percentage W1 of the first additive satisfies: 0<W1≤1%.

3. The electrolyte according to claim 1 or 2, characterized in that Based on the total mass of the electrolyte, the mass percentage W2 of the vinylene carbonate satisfies: 0<W2≤3%.

4. The electrolyte according to any one of claims 1 to 3, characterized in that Based on the total mass of the electrolyte, the mass percentage W3 of the boron-containing compound satisfies: 0<W3≤2%.

5. The electrolyte according to any one of claims 1 to 4, characterized in that The boron-containing compound is selected from boron-containing lithium salts and / or borate ester compounds.

6. The electrolyte according to claim 5, characterized in that The boron-containing lithium salt is selected from at least one of lithium tetrafluoroborate, lithium bis(oxalatoborate) and lithium difluorooxalatoborate; and / or, The borate compound is selected from trimethyl borate and / or tris(trimethylsilyl)borate.

7. The electrolyte according to any one of claims 1 to 6, characterized in that In the electrolyte, the mass percentage W1 of the first additive, the mass percentage W2 of vinylene carbonate, and the mass percentage W3 of the boron-containing compound satisfy the following relationship: W1 / W2=(0.16-2):1; W1 / W3=(0.5-2.5):

1.

8. The electrolyte according to any one of claims 1 to 7, characterized in that The electrolyte also includes lithium hexafluorophosphate.

9. The electrolyte according to any one of claims 1 to 8, characterized in that The electrolyte has a water content of ≤20 ppm and an acidity of ≤50 ppm.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the electrolyte according to any one of claims 1 to 9.

Images