Wide-temperature electrolyte and lithium-ion battery

Abstract

Provided is a wide-temperature electrolyte. The wide-temperature electrolyte comprises a non-aqueous organic solvent, a lithium salt, and an additive. The additive comprises an additive A. The structural formula of the additive A is as shown in formula (I), where R is a nitro group, hydrogen, or a hydrocarbon group having 1 to 6 carbon atoms. Adding the additive A to the electrolyte enables the battery to have both good high-temperature and low-temperature performance; the electrolyte has improved wide-temperature performance, which is beneficial to broadening the application scenarios of the lithium-ion battery.

Description

A wide-temperature electrolyte and lithium-ion battery Technical Field

[0001] This disclosure relates to the field of lithium-ion battery technology, specifically to a wide-temperature electrolyte and a lithium-ion battery. Background Technology

[0002] This section is intended to provide background or context for the embodiments of this disclosure set forth in the claims. The description herein is not, by virtue of its inclusion in this section, an admission that it is prior art.

[0003] Lithium-ion batteries possess advantages such as high energy density, high power density, and long cycle life, and have been widely used in consumer electronics and electric vehicles. However, currently commercially available lithium-ion batteries have poor adaptability to ambient temperature. At excessively high temperatures (>45°C), internal side reactions occur rapidly, while at excessively low temperatures (<0°C), kinetic transport is sluggish. Both excessively high and low temperatures negatively impact battery performance and can even lead to safety issues, severely limiting their application in a wider range of temperature scenarios.

[0004] In existing high / low temperature performance solutions for lithium-ion batteries, ethylene sulfate and propylene sulfate can improve the battery's high or low temperature performance to some extent, but they cannot simultaneously achieve both high and low temperature performance. Therefore, there is an urgent need to develop a wide-temperature electrolyte that combines both high and low temperature performance. Summary of the Invention

[0005] The purpose of this disclosure is to provide a wide-temperature electrolyte and lithium-ion battery that take into account both high-temperature and low-temperature performance.

[0006] To achieve the above objectives, the technical solution adopted in this disclosure is as follows:

[0007] This disclosure provides a wide-temperature electrolyte, comprising a non-aqueous organic solvent, a lithium salt, and an additive, wherein the additive includes additive A, and the structural formula of additive A is as follows:

[0008] Wherein, R is a nitro group, hydrogen, or a hydrocarbon group having 1 to 6 carbon atoms.

[0009] This disclosure introduces a nitro group and an R at the β-C site of the six-membered ring of propylene sulfate, enabling the formation of a more stable SEI component on the graphite anode surface. This effectively avoids direct contact between the electrolyte and the electrode material, thereby suppressing side reactions (such as gas generation and lithium dendrite formation) and enhancing interfacial stability. Simultaneously, it provides a uniform transport channel for lithium ions. This series of mechanisms helps improve the cycle performance of lithium-ion batteries at room temperature, their storage stability at high temperatures, and their charge-discharge efficiency at low temperatures.

[0010] In this disclosure, the hydrocarbon group includes saturated or unsaturated alkyl, alkenyl, alkynyl, and phenyl groups. The hydrocarbon group includes chain hydrocarbon groups and cyclic hydrocarbon groups, wherein the chain hydrocarbon groups include straight-chain hydrocarbon groups and branched-chain hydrocarbon groups.

[0011] In some embodiments, the hydrocarbon group is an alkyl or phenyl group having 1 to 6 carbon atoms.

[0012] Furthermore, the alkyl group is methyl, ethyl, propyl, butyl, pentyl, or hexyl.

[0013] Furthermore, the propyl group includes n-propyl and isopropyl, the butyl group includes n-butyl, sec-butyl, tert-butyl and isobutyl, the pentyl group includes n-pentyl and isopentyl, and the hexyl group includes cyclohexyl.

[0014] In some embodiments, R is nitro, hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, or isobutyl.

[0015] In some embodiments, R is nitro, hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, or isobutyl.

[0016] In some embodiments, R is nitro, hydrogen, methyl, ethyl, n-propyl, isopropyl, or isobutyl.

[0017] In some embodiments, R is a nitro group or an alkyl group having 1 to 3 carbon atoms.

[0018] In some specific embodiments, additive A is one or more of the substances shown in the following structural formula:

[0019] In some embodiments, the additive A accounts for 0.1% to 5% of the total mass of the electrolyte, more specifically 0.5% to 2.5%, for example 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, and 2.5%.

[0020] In some implementations, structural formula I is used. The substance shown reacts with thionyl chloride in the presence of chloroform. After the reaction is complete, the pH of the system is adjusted to neutral or alkaline. After extraction and washing, an intermediate is obtained. The intermediate is then reacted with periodic acid in the presence of a catalyst to obtain additive A. In this case, R in structural formula I is the same as R in additive A.

[0021] Furthermore, the reaction temperature of the substance shown in structural formula I with thionyl chloride is controlled to be 60–80°C, more preferably 65–75°C.

[0022] Furthermore, the reaction temperature between the intermediate and the periodic acid is controlled to be -10 to 10°C, more preferably -5 to 5°C.

[0023] Furthermore, the catalyst is ruthenium trichloride trihydrate.

[0024] Furthermore, the molar ratio of the substance shown in structural formula I to the catalyst is 1:(0.1 to 0.5), and more preferably 1:(0.2 to 0.3).

[0025] Furthermore, the molar ratio of the substance shown in structural formula I to the thionyl chloride is 1:(0.9~1.2).

[0026] Furthermore, the molar ratio of the substance shown in structural formula I to the periodic acid is 1:(0.9~1.2).

[0027] Furthermore, the pH of the system was adjusted using a saturated sodium bicarbonate solution.

[0028] Furthermore, the pH of the system is adjusted to 7-8.

[0029] Furthermore, the extraction was performed using chloroform.

[0030] Further, the washing is performed using the saturated sodium chloride solution.

[0031] Further, after the intermediate reacts with the periodic acid, it is allowed to stand and separate into layers. Then, it is extracted with chloroform, washed with saturated sodium sulfite, washed with saturated sodium chloride, and dried to obtain the additive A.

[0032] Furthermore, the additive also includes additive B, which is one or more of lithium difluorophosphate, lithium difluorodioxarate phosphate, and fluoroethylene carbonate.

[0033] Further, the additive B accounts for 1 to 10% of the total mass of the electrolyte, more preferably 2.5 to 6%.

[0034] In some embodiments, additive B is lithium difluorophosphate, lithium difluorodioxarate phosphate, and fluoroethylene carbonate, wherein the mass content of fluoroethylene carbonate in the electrolyte is greater than the sum of the mass contents of lithium difluorophosphate and lithium difluorodioxarate phosphate in the electrolyte.

[0035] Further, the mass ratio of the lithium difluorophosphate, the lithium difluorodioxarate phosphate, and the fluoroethylene carbonate is (0.3-1):(0.3-0.8):(2-8).

[0036] Furthermore, the lithium difluorophosphate accounts for 0.3-1% of the total mass of the electrolyte, the lithium difluorodioxanol phosphate accounts for 0.1-1% of the total mass of the electrolyte, and the fluoroethylene carbonate accounts for 2-4% of the total mass of the electrolyte.

[0037] Furthermore, the lithium salt is lithium hexafluorophosphate and / or lithium bisfluorosulfonylimide.

[0038] Furthermore, the lithium salt is lithium hexafluorophosphate and lithium difluorosulfonylimide.

[0039] Furthermore, the molar content of lithium hexafluorophosphate in the electrolyte is greater than the molar content of lithium difluorosulfonylimide in the electrolyte.

[0040] In some embodiments, the concentration of lithium hexafluorophosphate in the electrolyte is 0.8–1.5 M, more specifically 0.8–1.2 M, for example 0.8 M, 0.9 M, 1 M, 1.1 M, or 1.2 M.

[0041] In some embodiments, the concentration of the lithium difluorosulfonylimide in the electrolyte is 0.01 to 0.5 M, more specifically 0.1 to 0.3 M, for example 0.1 M, 0.2 M, or 0.3 M.

[0042] Furthermore, the organic solvent includes cyclic carbonates, linear carbonates, and linear carboxylic esters.

[0043] Furthermore, the mass ratio of the cyclic carbonate, the chain carbonate and the chain carboxylic acid ester is (15-50):(5-20):(30-80), and even more specifically (20-40):(5-15):(50-70).

[0044] In some embodiments, the cyclic carbonate is one or more of ethylene carbonate and propylene carbonate.

[0045] In some embodiments, the chain carbonate is ethyl methyl carbonate.

[0046] In some embodiments, the chain carboxylic acid ester is one or more of ethyl propionate and propyl propionate.

[0047] In some specific embodiments, the organic solvent is composed of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, propyl propionate, and ethyl propionate.

[0048] Further, the mass ratio of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, propyl propionate and ethyl propionate is (10-30):(5-20):(5-20):(20-50):(10-30), even further it is (10-20):(10-20):(5-15):(30-50):(15-25), and even further it is (12-18):(12-18):(8-12):(35-45):(18-22).

[0049] This disclosure also provides a lithium-ion battery, including a positive electrode, a separator, a negative electrode, and an electrolyte as described above.

[0050] Furthermore, the active material of the positive electrode is lithium cobalt oxide positive electrode material.

[0051] Furthermore, the active material of the negative electrode is artificial graphite.

[0052] Due to the application of the above technical solution, this disclosure has the following advantages compared with the prior art:

[0053] This disclosure discloses that by using additive A, a more stable SEI component is formed on the surface of the negative electrode, which can effectively suppress the occurrence of side reactions, improve interface stability, and provide a faster lithium-ion transport channel. This helps to improve the wide-temperature performance of the electrolyte and is beneficial to expanding the application scenarios of lithium-ion batteries. Detailed Implementation

[0054] The present disclosure will be further described below with reference to embodiments. However, the present disclosure is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present disclosure can be combined with each other as long as they do not conflict with each other.

[0055] Unless otherwise specified, the reagents, instruments, etc. used in the following examples and comparative examples are all commercially available products commonly used in the art, or can be prepared by conventional preparation methods in the art.

[0056] [Matter Synthesis]

[0057] 1. Synthesis of Compound 1

[0058] 1 mol of 2-nitro-1,3-propanediol was mixed thoroughly with 300 mL of chloroform. 1.1 mol of sulfoxide was slowly added dropwise at 10 °C, and the temperature was raised to 70 °C. The reaction mixture was stirred for 2 hours. Stirring was stopped after the reaction of the starting 2-nitro-1,3-propanediol was detected as complete by thin-layer chromatography (TLC). Saturated sodium bicarbonate solution was added to the reaction mixture for neutralization, adjusting the pH to 7-8. After the reaction mixture was allowed to stand and separate into layers, it was extracted with chloroform, followed by washing and separation with saturated sodium chloride solution to obtain the intermediate product solution.

[0059] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The temperature was lowered to 0°C, and the reaction was stirred for another 2 hours. After the intermediate product was detected by TLC and the reaction was complete, stirring was stopped. After the reaction solution was allowed to stand and separate into layers, it was extracted with chloroform, washed with saturated sodium sulfite, then washed with saturated sodium chloride, filtered, and dried to obtain compound 1, whose structural formula is [insert structural formula here]. The yield was 84.35%. 1 H NMR (400MHz, CDCl3-d1) δ4.121~4.305(m,2H), 4.012~4.115(m,H), 3.932~3.983(m,2H)).

[0060] 2. Synthesis of Compound 2

[0061] 1 mol of 2-nitro-2-methyl-1,3-propanediol was mixed thoroughly with 300 mL of chloroform. 1.1 mol of sulfoxide was slowly added dropwise at 10 °C, and the temperature was raised to 70 °C. The reaction mixture was stirred for 2 hours. Stirring was stopped after TLC confirmed the complete reaction of the 2-nitro-2-methyl-1,3-propanediol. Saturated sodium bicarbonate solution was added to the reaction mixture for neutralization, adjusting the pH to 7-8. After the reaction mixture was allowed to stand and separate into layers, it was extracted with chloroform, then washed and separated with saturated sodium chloride solution to obtain an intermediate product solution.

[0062] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The temperature was lowered to 0°C, and the reaction was stirred for another 2 hours. After the intermediate product was detected by TLC and the reaction was complete, stirring was stopped. After the reaction solution was allowed to stand and separate into layers, it was extracted with chloroform, washed with saturated sodium sulfite, then washed with saturated sodium chloride, filtered, and dried to obtain compound 2, whose structural formula is [insert structural formula here]. The yield was 85.13%. 1 H NMR (400MHz, CDCl3-d1) δ4.143~4.186(d,2H),3.843~3.9235(d,2H),1.678(s,3H)).

[0063] 3. Synthesis of Compound 3

[0064] 1 mol of 2-nitro-2-ethyl-1,3-propanediol was mixed thoroughly with 300 mL of chloroform. 1.1 mol of sulfoxide was slowly added dropwise at 10 °C, and the temperature was raised to 70 °C. The reaction mixture was stirred for 2 hours. Stirring was stopped after TLC confirmed the complete reaction of the 2-nitro-2-ethyl-1,3-propanediol. Saturated sodium bicarbonate solution was added to the reaction mixture for neutralization, adjusting the pH to 7-8. After the reaction mixture was allowed to stand and separate into layers, it was extracted with chloroform, then washed and separated with saturated sodium chloride solution to obtain an intermediate product solution.

[0065] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution, the temperature was lowered to 0°C, and the reaction was stirred for another 2 hours. After the intermediate product was detected by TLC and the reaction was complete, stirring was stopped. The reaction solution was allowed to stand and separate into layers, then extracted with chloroform, washed with saturated sodium sulfite, then washed with saturated sodium chloride, filtered, and dried to obtain compound 3, whose structural formula is [insert structural formula here]. The yield was 86.17%. 1 H NMR (400MHz, CDCl3-d1) δ4.148~4.183(d,2H), 3.886~3.932(d,2H), 1.812~1.854(m,2H), 0.872~0.917(t,3H)).

[0066] 4. Synthesis of Compound 4

[0067] 1 mol of 2-nitro-2-propyl-1,3-propanediol was mixed thoroughly with 300 mL of chloroform. 1.1 mol of sulfoxide was slowly added dropwise at 10 °C, and the temperature was raised to 70 °C. The reaction mixture was stirred for 2 hours. Stirring was stopped after TLC confirmed the complete reaction of the 2-nitro-2-propyl-1,3-propanediol. Saturated sodium bicarbonate solution was added to the reaction mixture for neutralization, adjusting the pH to 7-8. After the reaction mixture was allowed to stand and separate into layers, it was extracted with chloroform, followed by washing and separation with saturated sodium chloride solution to obtain an intermediate product solution.

[0068] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The temperature was lowered to 0°C, and the reaction was stirred for another 2 hours. After the intermediate product was detected by TLC and the reaction was complete, stirring was stopped. After the reaction solution was allowed to stand and separate into layers, it was extracted with chloroform, washed with saturated sodium sulfite, then washed with saturated sodium chloride, filtered, and dried to obtain compound 4, whose structural formula is [insert structural formula here]. The yield was 85.23%. 1H NMR (400MHz, CDCl3-d1) δ4.141~4.189(d,2H), 3.882~3.927(d,2H), 1.753~1.795(t,2H), 1.275~1.346(m,2H), 0.875~0.913(t,3H)).

[0069] 5. Synthesis of Compound 5

[0070] 1 mol of 2-nitro-2-butyl-1,3-propanediol was mixed thoroughly with 300 mL of chloroform. 1.1 mol of sulfoxide was slowly added dropwise at 10 °C, and the temperature was raised to 70 °C. The reaction mixture was stirred for 2 hours. Stirring was stopped after TLC confirmed the complete reaction of the 2-nitro-2-butyl-1,3-propanediol. Saturated sodium bicarbonate solution was added to the reaction mixture for neutralization, adjusting the pH to 7-8. After the reaction mixture was allowed to stand and separate into layers, it was extracted with chloroform, followed by washing and separation with saturated sodium chloride solution to obtain an intermediate product solution.

[0071] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution, the temperature was lowered to 0°C, and the reaction was stirred for another 2 hours. After the intermediate product was detected by TLC and the reaction was complete, stirring was stopped. The reaction solution was allowed to stand and separate into layers, then extracted with chloroform, washed with saturated sodium sulfite, then washed with saturated sodium chloride, filtered, and dried to obtain compound 5, whose structural formula is [insert structural formula here]. The yield was 84.32%. 1 H NMR (400MHz, CDCl3-d1) δ4.143~4.184(d,2H), 3.882~3.925(d,2H), 1.753~1.796(t,2H), 1.265~1.302(m,4H), 0.863~0.903(t,3H)).

[0072] 6. Synthesis of Compound 6

[0073] 1 mol of 2-isopropyl-2-nitro-1,3-propanediol was mixed thoroughly with 300 mL of chloroform. 1.1 mol of thionyl chloride was slowly added dropwise at 10 °C, and the temperature was raised to 70 °C. The reaction mixture was stirred for 2 hours. Stirring was stopped after TLC confirmed the complete reaction of the starting material 2-isopropyl-2-nitro-1,3-propanediol. Saturated sodium bicarbonate solution was added to the reaction mixture for neutralization, adjusting the pH to 7-8. After the reaction mixture was allowed to stand and separate into layers, it was extracted with chloroform, followed by washing and separation with saturated sodium chloride solution to obtain an intermediate product solution.

[0074] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution, the temperature was lowered to 0°C, and the reaction was stirred for another 2 hours. After the intermediate product was detected by TLC and the reaction was complete, stirring was stopped. The reaction solution was allowed to stand and separate into layers, then extracted with chloroform, washed with saturated sodium sulfite, then washed with saturated sodium chloride, filtered, and dried to obtain compound 6, whose structural formula is [insert structural formula here]. The yield was 85.27%. 1 H NMR (400MHz, CDCl3-d1) δ4.142~4.187(d,2H), 3.883~3.931(d,2H), 1.482~1.527(m,H), 0.863~0.907(d,6H)).

[0075] 7. Synthesis of Compound 7

[0076] 1 mol of 2-isobutyl-2-nitro-1,3-propanediol was mixed thoroughly with 300 mL of chloroform. 1.1 mol of sulfoxide was slowly added dropwise at 10 °C, and the temperature was raised to 70 °C. The reaction mixture was stirred for 2 hours. Stirring was stopped after TLC confirmed the complete reaction of the 2-isobutyl-2-nitro-1,3-propanediol. Saturated sodium bicarbonate solution was added to the reaction mixture for neutralization, adjusting the pH to 7-8. After the reaction mixture was allowed to stand and separate into layers, it was extracted with chloroform, followed by washing and separation with saturated sodium chloride solution to obtain an intermediate product solution.

[0077] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The temperature was lowered to 0°C, and the reaction was stirred for another 2 hours. After the intermediate product was detected by TLC and the reaction was complete, stirring was stopped. After the reaction solution was allowed to stand and separate into layers, it was extracted with chloroform, washed with saturated sodium sulfite, then washed with saturated sodium chloride, filtered, and dried to obtain compound 7, whose structural formula is [insert structural formula here]. The yield was 83.12%. 1 H NMR (400MHz, CDCl3-d1) δ4.143~4.193(d,2H), 3.878~3.937(d,2H), 1.485~1.736(m,2H), 1.597~1.652(m,H), 0.886~0.942(d,6H)).

[0078] 8. Synthesis of Compound 8

[0079] 1 mol of 2-cyclohexyl-2-nitro-1,3-propanediol was mixed thoroughly with 300 mL of chloroform. 1.1 mol of sulfoxide was slowly added dropwise at 10 °C, and the temperature was raised to 70 °C. The reaction mixture was stirred for 2 hours. Stirring was stopped after TLC confirmed the complete reaction of the starting material 2-cyclohexyl-2-nitro-1,3-propanediol. Saturated sodium bicarbonate solution was added to the reaction mixture for neutralization, adjusting the pH to 7-8. After the reaction mixture was allowed to stand and separate into layers, it was extracted with chloroform, followed by washing and separation with saturated sodium chloride solution to obtain an intermediate product solution.

[0080] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The temperature was lowered to 0°C, and the reaction was stirred for another 2 hours. After the intermediate product was detected by TLC and the reaction was complete, stirring was stopped. After the reaction solution was allowed to stand and separate into layers, it was extracted with chloroform, washed with saturated sodium sulfite, then washed with saturated sodium chloride, filtered, and dried to obtain compound 8, whose structural formula is [insert structural formula here]. The yield was 82.13%. 1 H NMR (400MHz, CDCl3-d1) δ4.138~4.185(d,2H),3.884~3.928(d,2H),1.598~1.645(m,2H) ), 1.501~1.558(m,2H), 1.405~1.485(m,4H), 1.365~1.396(m,2H), 1.153~1.223(m,H)).

[0081] 9. Synthesis of Compound 9

[0082] 1 mol of 2-nitro-2-phenylpropane-1,3-diol was mixed thoroughly with 300 mL of chloroform. 1.1 mol of sulfoxide was slowly added dropwise at 10 °C, and the temperature was raised to 70 °C. The reaction mixture was stirred for 2 hours. Stirring was stopped after TLC confirmed the complete reaction of the 2-nitro-2-phenylpropane-1,3-diol. Saturated sodium bicarbonate solution was added to the reaction mixture for neutralization, adjusting the pH to 7-8. After the reaction mixture was allowed to stand and separate into layers, it was extracted with chloroform, followed by washing and separation with saturated sodium chloride solution to obtain the intermediate product solution.

[0083] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution, the temperature was lowered to 0°C, and the reaction was stirred for another 2 hours. After the intermediate product was detected by TLC and the reaction was complete, stirring was stopped. The reaction solution was allowed to stand and separate into layers, then extracted with chloroform, washed with saturated sodium sulfite, then washed with saturated sodium chloride, filtered, and dried to obtain compound 9, whose structural formula is [insert structural formula here]. The yield was 83.46%. 1H NMR (400MHz, CDCl3-d1) δ7.218~7.335(m,5H), 4.468~4.725(d,2H), 4.227~4.276(d,2H)).

[0084] 10. Synthesis of Compound 10

[0085] 1 mol of 2,2-dinitro-1,3-propanediol was mixed thoroughly with 300 mL of chloroform. 1.1 mol of sulfoxide was slowly added dropwise at 10 °C, and the temperature was raised to 70 °C. The reaction mixture was stirred for 2 hours. Stirring was stopped after TLC confirmed the complete reaction of the 2,2-dinitro-1,3-propanediol. Saturated sodium bicarbonate solution was added to the reaction mixture for neutralization, adjusting the pH to 7-8. After the reaction mixture was allowed to stand and separate into layers, it was extracted with chloroform, then washed and separated with saturated sodium chloride solution to obtain an intermediate product solution.

[0086] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The temperature was lowered to 0°C, and the reaction was stirred for another 2 hours. After the intermediate product was detected by TLC and the reaction was complete, stirring was stopped. After the reaction solution was allowed to stand and separate into layers, it was extracted with chloroform, washed with saturated sodium sulfite, then washed with saturated sodium chloride, filtered, and dried to obtain compound 10, whose structural formula is [insert structural formula here]. The yield was 87.28%. 1 H NMR (400MHz, CDCl3-d1) δ4.67 (s, 4H)).

[0087] [positive electrode]

[0088] Weigh out LCO (positive electrode material), acetylene black (conductive agent), and PVDF (binder) in a mass ratio of 95:2.5:2.5, add an appropriate amount of N-methylpyrrolidone, and mix thoroughly to obtain a positive electrode slurry. Coat the positive electrode slurry onto aluminum foil, dry it, and then roll and slit it to obtain positive electrode sheets. The compacted density of the positive electrode is 4.2 g / cm³. 3 .

[0089] [negative electrode]

[0090] Graphite, conductive agent acetylene black, carboxymethyl cellulose, and styrene-butadiene rubber were weighed according to a mass ratio of 95:2.5:2:0.5. An appropriate amount of deionized water was added, and the mixture was stirred thoroughly to obtain the negative electrode slurry. The negative electrode slurry was coated onto copper foil, dried, and then rolled and slit to obtain the negative electrode sheet. The compacted density of the negative electrode was 1.8 g / cm³. 3 .

[0091] Electrolyte

[0092] Example 1

[0093] Dissolve 1M lithium hexafluorophosphate and 0.2M lithium difluorosulfonylimide in a mixed solvent of ethylene carbonate / propylene carbonate / methyl ethyl carbonate / ethyl propionate / propyl propionate in a mass ratio of 15 / 15 / 10 / 20 / 40, and add the following additives in the following mass proportions: 0.8% lithium difluorophosphate, 0.5% lithium difluorodioxarate phosphate, and 3% fluoroethylene carbonate. Mix well, and then add 1% of compound 10.

[0094] Example 2-10

[0095] The experiment was basically the same as in Example 1, except that compound 10 was replaced with compounds 1, 2, 3, 4, 5, 6, 7, 8 and 9, respectively.

[0096] Examples 11-14

[0097] The method is basically the same as in Example 1, except that the amount of compound 10 added is replaced with 0.3%, 0.5%, 1.5%, and 2%, respectively.

[0098] Comparative Example 1

[0099] It is essentially the same as Example 1, except that 1% of compound 10 is not added.

[0100] Comparative Examples 2-5

[0101] It is basically the same as Example 1, except that compound 10 is replaced with the same amount of propylene sulfate, vinyl sulfate, 1,3-propanesulfonate lactone, and 1,3-propenesulfonate lactone.

[0102] [Battery Manufacturing]

[0103] Using the above-mentioned positive and negative electrodes and the electrolytes prepared in Examples 1-14 and Comparative Examples 1-5, a PE separator with a thickness of 12 micrometers was selected, and a pouch cell was manufactured using a stacking process, with a designed capacity of 2050 mAh.

[0104] [Battery Cycle Performance Test]

[0105] Battery cycle performance tests were conducted at -20℃ and 55℃, with a voltage range of 2.75-4.25V. The battery was cycled at 1C at 55℃ and at 0.2C at -20℃, and the capacity retention was tested after 500 cycles. Capacity retention (%) = (Discharge capacity after 500 cycles / Discharge capacity in the first cycle) × 100%.

[0106] [Battery Discharge Performance Test at -40℃]

[0107] The battery was fully charged at room temperature using a 0.2C rate, then placed at -40°C for 4 hours. The battery was then discharged at a 0.2C rate, and the charge and discharge capacities were recorded. The -40°C discharge percentage was calculated. Discharge percentage (%) = (-40°C discharge capacity / room temperature charge capacity) × 100%.

[0108] The test results of the above embodiments and comparative examples are shown in Table 1.

[0109] Table 1

[0110] As can be seen from Comparative Examples 1-5, the introduction of five-membered ring sulfur-containing additives commonly used in commercial electrolytes, such as vinyl sulfate (Comparative Example 3), 1,3-propanesulfonyl lactone (Comparative Example 4), and 1,3-propenesulfonyl lactone (Comparative Example 5), while improving the low-temperature performance of the battery, leads to a rapid deterioration in the high-temperature cycle capacity retention rate at 55°C. This is due to the poor thermal stability of the SEI film formed on the negative electrode surface. After introducing six-membered ring propylene sulfate (Comparative Example 2), the SEI film formed on the negative electrode surface exhibits stronger thermal stability, resulting in a significant improvement in high-temperature performance. However, the cycle performance at -20°C and the discharge performance at -40°C show a decline.

[0111] As can be seen from Comparative Example 2 and Examples 1-10, introducing a nitro functional group at the β-C site of propylene sulfate improves both the high-temperature and low-temperature performance of the battery. Further introduction of groups other than hydrogen (e.g., hydrocarbon groups or nitro groups, where the hydrocarbon group can be a saturated alkyl group or an unsaturated phenyl, cycloalkanes, etc.) at this site further improves both low-temperature and high-temperature performance. In particular, when two nitro groups are introduced simultaneously at this site, the battery exhibits optimal performance in both high-temperature and low-temperature conditions. When a hydrocarbon group is further introduced at this site, the improvement in high- and low-temperature performance initially increases and then decreases with the increase in the number of carbon atoms in the hydrocarbon group introduced at the para site. Therefore, when a hydrocarbon group is further introduced at this site, the number of carbon atoms in the hydrocarbon group is preferably 1-6, and more preferably 1-3. Furthermore, when the number of carbon atoms in the introduced hydrocarbon group is the same, branched hydrocarbon groups show a more significant improvement in battery performance compared to straight-chain hydrocarbon groups.

[0112] As can be seen from Examples 1 and 11-14, as the amount of additive A increases, the high and low temperature performance of the battery shows a trend of first increasing and then decreasing, with the best performance at an addition amount of 1%.

[0113] The above detailed description of this disclosure is intended to enable those skilled in the art to understand and implement its contents, but it should not be construed as limiting the scope of protection of this disclosure. All equivalent changes or modifications made in accordance with the spirit and essence of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A wide-temperature electrolyte, comprising a non-aqueous organic solvent, a lithium salt, and additives, characterized in that: The additive includes additive A, and the structural formula of additive A is as follows: Wherein, R is a nitro group, hydrogen, or a hydrocarbon group having 1 to 6 carbon atoms.

2. The wide-temperature electrolyte according to claim 1, characterized in that: R can be nitro, hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, isobutyl, n-pentyl, isopentyl, or cyclohexyl.

3. The wide-temperature electrolyte according to claim 2, characterized in that: R can be nitro, hydrogen, methyl, ethyl, n-propyl, isopropyl, or isobutyl.

4. The wide-temperature electrolyte according to claim 3, characterized in that: R is a nitro group or an alkyl group having 1 to 3 carbon atoms.

5. The wide-temperature electrolyte according to claim 1, characterized in that: Additive A is one or more substances with the following structural formula:

6. The wide-temperature electrolyte according to claim 1, characterized in that: The additive A accounts for 0.1% to 5% of the total mass of the electrolyte.

7. The wide-temperature electrolyte according to claim 1, characterized in that: The additive A accounts for 0.5% to 2.5% of the total mass of the electrolyte.

8. The wide-temperature electrolyte according to claim 1, characterized in that: The additive also includes additive B, which is one or more of lithium difluorophosphate, lithium difluorodioxarate phosphate, and fluoroethylene carbonate.

9. The wide-temperature electrolyte according to claim 8, characterized in that: The additive B accounts for 1 to 10% of the total mass of the electrolyte.

10. The wide-temperature electrolyte according to claim 8, characterized in that: Additive B is lithium difluorophosphate, lithium difluorodioxarate phosphate, and fluoroethylene carbonate, wherein the mass content of fluoroethylene carbonate in the electrolyte is greater than the sum of the mass contents of lithium difluorophosphate and lithium difluorodioxarate phosphate in the electrolyte.

11. The wide-temperature electrolyte according to claim 10, characterized in that: The mass ratio of lithium difluorophosphate, lithium difluorodioxarate phosphate, and fluoroethylene carbonate is (0.3-1):(0.3-0.8):(2-8).

12. The wide-temperature electrolyte according to claim 1, characterized in that: The lithium salt is lithium hexafluorophosphate and / or lithium bis(fluorosulfonyl)imide; and / or, The organic solvents include cyclic carbonates, linear carbonates, and linear carboxylic esters.

13. The wide-temperature electrolyte according to claim 12, characterized in that: The lithium salt is lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, wherein the molar content of lithium hexafluorophosphate in the electrolyte is greater than the molar content of lithium bis(fluorosulfonyl)imide in the electrolyte; and / or, The concentration of lithium hexafluorophosphate in the electrolyte is 0.8–1.5 M; and / or, The concentration of lithium difluorosulfonylimide in the electrolyte is 0.01–0.5 M; and / or, The cyclic carbonate is one or more of ethylene carbonate and propylene carbonate; and / or The chain carbonate is ethyl methyl carbonate; and / or, The chain-like carboxylic acid ester is one or more of ethyl propionate and propyl propionate; and / or, The mass ratio of the cyclic carbonate, the chain carbonate and the chain carboxylic acid ester is (15-50):(5-20):(30-80).

14. The wide-temperature electrolyte according to claim 13, characterized in that: The organic solvent is composed of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, propyl propionate and ethyl propionate, and the mass ratio of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, propyl propionate and ethyl propionate is (10-30):(5-20):(5-20):(20-50):(10-30).

15. A lithium-ion battery, comprising a positive electrode, a separator, and a negative electrode, characterized in that: The lithium-ion battery further includes the electrolyte as described in any one of claims 1 to 14.

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