Wide-temperature electrolyte and lithium ion battery

Abstract

In order to solve the problem that a commercialized lithium ion battery electrolyte cannot give consideration to both high-temperature performance and low-temperature performance, the invention provides 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, and the structural formula of the additive A is shown in the specification, r1 and R2 are respectively and independently selected from nitro, substituted or unsubstituted alkyl, cyano, halogen or hydrogen, at least one of R1 and R2 is not hydrogen, and when one of R1 and R2 is hydrogen, the other one is nitro. By adding the additive A into the electrolyte, the battery can have good high-temperature and low-temperature performance at the same time, the wide-temperature performance of the electrolyte is more excellent, and the use scene of the lithium ion battery can be widened.

Description

Technical Field

[0001] This invention 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 the invention set forth in the claims. The description herein is not an admission that it is prior art simply because it is included in this section.

[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 invention is to provide a wide-temperature electrolyte and lithium-ion battery that takes into account both high-temperature and low-temperature performance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention 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]

[0009] R1 and R2 are independently selected from nitro, substituted or unsubstituted hydrocarbon, cyano, halogen or hydrogen, respectively, at least one of R1 and R2 is not hydrogen, and when one of R1 and R2 is hydrogen, the other is nitro.

[0010] This invention introduces R1 and R2 at the para site of the six-membered ring of propylene sulfate, which can form a more stable SEI component on the surface of graphite anode, thereby improving the high-temperature and low-temperature performance of the battery.

[0011] In this document, the hydrocarbon groups include saturated or unsaturated alkyl, alkenyl, alkynyl, and phenyl groups.

[0012] Preferably, R1 and R2 are independently selected from nitro, substituted or unsubstituted hydrocarbon groups with 1 to 6 carbon atoms, or hydrogen, wherein the substituent of the hydrocarbon group is a halogen.

[0013] In some embodiments, the hydrocarbon group is selected from alkyl or phenyl groups having 1 to 6 carbon atoms.

[0014] Furthermore, the alkyl group is selected from methyl, ethyl, propyl, butyl, pentyl, and hexyl.

[0015] 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.

[0016] Preferably, the halogen is fluorine.

[0017] In some embodiments, R1 is a nitro group, and R2 is selected from nitro, hydrogen, alkyl or phenyl groups having 1 to 6 carbon atoms.

[0018] In some embodiments, R1 and R2 are each independently selected from alkyl groups or halogens having 1 to 3 carbon atoms.

[0019] In some specific embodiments, additive A is selected from one or more substances with the following structural formulas:

[0020]

[0021]

[0022] Furthermore, at least one of R1 and R2 is a nitro group, and when only one is a nitro group, the other is selected from an alkyl group having 1 to 3 carbon atoms.

[0023] Preferably, the additive A accounts for 0.1% to 5% of the total mass of the electrolyte, more preferably 0.5% to 2.5%, for example 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, and 2.5%.

[0024] Preferably, structural formula I 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. R1 and R2 in structural formula I are the same as R1 and R2 in additive A.

[0025] Preferably, the reaction temperature of the substance shown in structural formula I with thionyl chloride is controlled at 60-80°C, and more preferably 65-75°C.

[0026] Preferably, the reaction temperature between the intermediate and the periodic acid is controlled at -10 to 10°C, and more preferably -5 to 5°C.

[0027] Preferably, the catalyst is ruthenium trichloride trihydrate.

[0028] More preferably, 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).

[0029] Preferably, the molar ratio of the substance represented by structural formula I to the thionyl chloride is 1:(0.9 to 1.2).

[0030] Preferably, the molar ratio of the substance shown in structural formula I to the periodic acid is 1:(0.9-1.2).

[0031] Preferably, the pH of the system is adjusted using a saturated sodium bicarbonate solution.

[0032] More preferably, the pH of the system is adjusted to 7-8.

[0033] Preferably, chloroform is used for the extraction.

[0034] Preferably, the washing is performed using the saturated sodium chloride solution.

[0035] Preferably, after the intermediate reacts with the periodic acid, it is allowed to stand and separate into layers, then extracted with chloroform, washed with saturated sodium sulfite, washed with saturated sodium chloride, and dried to obtain the additive A.

[0036] Preferably, the additive further includes additive B, which is selected from one or more of lithium difluorophosphate, lithium difluorodioxarate phosphate, and fluoroethylene carbonate.

[0037] Preferably, the additive B accounts for 1 to 10% of the total mass of the electrolyte, more preferably 2.5 to 6%.

[0038] 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.

[0039] 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).

[0040] 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.

[0041] Preferably, the lithium salt is lithium hexafluorophosphate and lithium difluorosulfonylimide.

[0042] More preferably, the molar content of lithium hexafluorophosphate in the electrolyte is greater than the molar content of lithium difluorosulfonylimide in the electrolyte.

[0043] In some embodiments, the concentration of lithium hexafluorophosphate in the electrolyte is 0.8–1.5 M, more preferably 0.8–1.2 M, such as 0.8 M, 0.9 M, 1 M, 1.1 M, or 1.2 M; and the concentration of lithium difluorosulfonylimide in the electrolyte is 0.01–0.5 M, more preferably 0.1–0.3 M, such as 0.1 M, 0.2 M, or 0.3 M.

[0044] Preferably, the organic solvent includes cyclic carbonates, chain carbonates, and chain carboxylic esters.

[0045] More preferably, 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 preferably (20-40):(5-15):(50-70).

[0046] In some embodiments, the cyclic carbonate is selected from one or more of ethylene carbonate and propylene carbonate.

[0047] In some embodiments, the chain carbonate is ethyl methyl carbonate.

[0048] In some embodiments, the chain carboxylic acid ester is selected from one or more of ethyl propionate and propyl propionate.

[0049] In some specific embodiments, the organic solvent is composed of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, propyl propionate, and ethyl propionate.

[0050] 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).

[0051] The present invention also provides a lithium-ion battery, comprising a positive electrode, a separator, a negative electrode, and an electrolyte as described above.

[0052] Preferably, the active material of the positive electrode is a lithium cobalt oxide positive electrode material, such as 4.25V LCO.

[0053] Preferably, the active material of the negative electrode is artificial graphite.

[0054] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0055] This invention enables the battery to have both good high-temperature and low-temperature performance by adding additive A to the electrolyte, and the electrolyte has a better wide temperature range, which is beneficial to expanding the application scenarios of lithium-ion batteries. Detailed Implementation

[0056] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific applications, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0057] 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.

[0058] [Matter Synthesis]

[0059] 1. Synthesis of Compound 1

[0060] 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 TLC confirmed the complete reaction of the 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.

[0061] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The mixture was cooled to 0°C and 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. Extraction was performed with chloroform, followed by washing with saturated sodium sulfite and then saturated sodium chloride. After filtration and drying, compound 1 was obtained with a yield of 84.35%. (¹H NMR (400 MHz, CDCl₃-d₁) δ 4.121–4.305 (m, 2H), 4.012–4.115 (m, H), 3.932–3.983 (m, 2H))

[0062] 2. Synthesis of Compound 2

[0063] 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.

[0064] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The mixture was cooled to 0°C and stirred for another 2 hours. TLC analysis showed that the intermediate product had completely reacted, at which point 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, with a yield of 85.13%. (1H NMR (400MHz, CDCl3-d1) δ 4.143–4.186 (d, 2H), 3.843–3.9235 (d, 2H), 1.678 (s, 3H))

[0065] 3. Synthesis of Compound 3

[0066] 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.

[0067] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The mixture was cooled to 0°C and stirred for another 2 hours. TLC analysis showed that the intermediate product had completely reacted, after which stirring was stopped. The reaction solution was allowed to stand and separate into layers. Extraction was performed with chloroform, followed by washing with saturated sodium sulfite and then saturated sodium chloride. After filtration and drying, compound 3 was obtained, with a yield of 86.17%. (¹H NMR (400 MHz, CDCl₃-d₁) δ 4.148–4.183 (d, 2H), 3.886–3.932 (d, 2H), 1.812–1.854 (m, 2H), 0.872–0.917 (t, 3H))

[0068] 4. Synthesis of Compound 4

[0069] 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.

[0070] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The mixture was cooled to 0°C and stirred for another 2 hours. TLC analysis showed that the intermediate product had completely reacted, after which stirring was stopped. The reaction solution was allowed to stand and separate into layers. Extraction was performed with chloroform, followed by washing with saturated sodium sulfite and then saturated sodium chloride. After filtration and drying, compound 4 was obtained with a yield of 85.23%. (¹H NMR (400 MHz, CDCl₃-d₁) δ 4.141–4.189 (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))

[0071]

[0072] 5. Synthesis of Compound 5

[0073] 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.

[0074] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The mixture was cooled to 0°C and stirred for another 2 hours. TLC analysis showed that the intermediate product had completely reacted, after which stirring was stopped. The reaction solution was allowed to stand and separate into layers. Extraction was performed with chloroform, followed by washing with saturated sodium sulfite and then saturated sodium chloride. After filtration and drying, compound 5 was obtained with a yield of 84.32%. (¹H NMR (400 MHz, CDCl₃-d₁) δ 4.143–4.184 (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))

[0075]

[0076] 6. Synthesis of Compound 6

[0077] 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.

[0078] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The mixture was cooled to 0°C and stirred for another 2 hours. TLC analysis showed that the intermediate product had completely reacted, after which stirring was stopped. The reaction solution was allowed to stand and separate into layers. Extraction was performed with chloroform, followed by washing with saturated sodium sulfite and then saturated sodium chloride. After filtration and drying, compound 6 was obtained, with a yield of 85.27%. (¹H NMR (400 MHz, CDCl₃-d₁) δ 4.142–4.187 (d, 2H), 3.883–3.931 (d, 2H), 1.482–1.527 (m, H), 0.863–0.907 (d, 6H))

[0079] 7. Synthesis of Compound 7

[0080] 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.

[0081] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The mixture was cooled to 0°C and stirred for another 2 hours. After the intermediate product was confirmed to be completely reacted by TLC, stirring was stopped. The reaction solution was allowed to stand and separate into layers. Extraction was performed with chloroform, followed by washing with saturated sodium sulfite and then saturated sodium chloride. After filtration and drying, compound 7 was obtained with a yield of 83.12%. (¹H NMR (400 MHz, CDCl₃-d₁) δ 4.143–4.193 (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))

[0082]

[0083] 8. Synthesis of Compound 8

[0084] 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.

[0085] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The mixture was cooled to 0°C and stirred for another 2 hours. TLC analysis showed that the intermediate product had completely reacted, after which stirring was stopped. The reaction solution was allowed to stand and separate into layers. Extraction was performed with chloroform, followed by washing with saturated sodium sulfite and then saturated sodium chloride. After filtration and drying, compound 8 was obtained, with a yield of 82.13%. (¹H NMR (400 MHz, CDCl₃-d₁) δ 4.138–4.185 (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))

[0086]

[0087] 9. Synthesis of Compound 9

[0088] 1 mol of 2-nitro-2-phenylpropane-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-nitro-2-phenylpropane-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 the intermediate product solution.

[0089] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The mixture was cooled to 0°C and stirred for another 2 hours. TLC analysis showed that the intermediate product had completely reacted, after which stirring was stopped. The reaction solution was allowed to stand and separate into layers. Extraction was performed with chloroform, followed by washing with saturated sodium sulfite and then saturated sodium chloride. After filtration and drying, compound 9 was obtained, with a yield of 83.46%. (¹H NMR (400 MHz, CDCl₃-d₁) δ 7.218–7.335 (m, 5H), 4.468–4.725 (d, 2H), 4.227–4.276 (d, 2H))

[0090]

[0091] 10. Synthesis of Compound 10

[0092] 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.

[0093] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The mixture was cooled to 0°C and stirred for another 2 hours. TLC analysis showed that the intermediate product had completely reacted, at which point 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 in 87.28% yield. (1H NMR (400MHz, CDCl3-d1) δ 4.67 (s, 4H))

[0094] 11. Synthesis of Compound 11

[0095] 1 mol of 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. The temperature was raised to 70 °C, and the reaction was continued with stirring for 2 hours. Stirring was stopped after TLC confirmed the complete reaction of the 2-methyl-1,3-propanediol. Saturated sodium bicarbonate solution was added to the reaction solution for neutralization, adjusting the pH to 7-8. After the reaction solution 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.

[0096] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The mixture was cooled to 0°C and stirred for another 2 hours. TLC analysis showed that the intermediate product had completely reacted, at which point 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 11, with a yield of 88.67%. (¹H NMR (400 MHz, CDCl₃-d₁) δ 3.558–3.607 (m, 2H), 3.301–3.347 (m, 2H), 1.865–1.912 (m, H), 0.857–0.898 (d, 3H))

[0097]

[0098] 12. Synthesis of Compound 12

[0099] 1 mol of 2,2-dimethyl-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-dimethyl-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.

[0100] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The mixture was cooled to 0°C and stirred for another 2 hours. TLC analysis showed that the intermediate product had completely reacted, at which point 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 12, with a yield of 87.24%. (1H NMR (400MHz, CDCl3-d1) δ 3.39 (s, 4H), 0.89 (s, 6H))

[0101]

[0102] 13. Synthesis of Compound 13

[0103] 1 mol of 2-fluoro-1,3-propanediol was mixed thoroughly with 300 mL of chloroform. 1.1 mol of thionyl chloride was slowly added dropwise at 10 °C. The temperature was raised to 70 °C, and the reaction was continued with stirring for 2 hours. Stirring was stopped after TLC confirmed the complete reaction of the 2-fluoro-1,3-propanediol. Saturated sodium bicarbonate solution was added to the reaction solution for neutralization, adjusting the pH to 7-8. After the reaction solution 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.

[0104] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The mixture was cooled to 0°C and stirred for another 2 hours. After the intermediate product was confirmed to be completely reacted by TLC, stirring was stopped. The reaction solution was allowed to stand and separate into layers. Extraction was performed with chloroform, followed by washing with saturated sodium sulfite and then saturated sodium chloride. After filtration and drying, compound 13 was obtained with a yield of 85.12%. (¹H NMR (400 MHz, CDCl₃-d₁) δ 3.582–3.636 (m, H), 3.774–3.818 (m, 2H), 3.513–3.571 (m, 2H))

[0105]

[0106] 14. Synthesis of Compound 14

[0107] 1 mol of 2-fluoro-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-fluoro-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.

[0108] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The mixture was cooled to 0°C and stirred for another 2 hours. TLC analysis showed that the intermediate product had completely reacted, after which stirring was stopped. The reaction solution was allowed to stand and separate into layers. Extraction was performed with chloroform, followed by washing with saturated sodium sulfite and then saturated sodium chloride. After filtration and drying, compound 14 was obtained, with a yield of 87.12%. (¹H NMR (400 MHz, CDCl₃-d₁) δ 3.463–3.513 (m, 2H), 3.708–3.762 (m, 2H), 1.348–1.403 (d, 3H))

[0109]

[0110] 15. Synthesis of Compound 15

[0111] 1 mol of 2,2-difluoro-1,3-propanediol was mixed thoroughly with 300 mL of chloroform. 1.1 mol of thionyl chloride was slowly added dropwise at 10 °C. The temperature was raised to 70 °C, and the reaction was continued with stirring for 2 hours. Stirring was stopped after TLC confirmed the complete reaction of the 2,2-difluoro-1,3-propanediol. Saturated sodium bicarbonate solution was added to the reaction solution for neutralization, adjusting the pH to 7-8. After the reaction solution 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.

[0112] Further, 0.23 mol of ruthenium trichloride trihydrate and 1.1 mol of periodic acid were added to the above solution. The mixture was cooled to 0°C and stirred for another 2 hours. TLC analysis showed that the intermediate product had completely reacted, at which point 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 15 in 87.73% yield. (1H NMR (400MHz, CDCl3-d1) δ 3.621–3.934 (t, 4H))

[0113]

[0114] [positive electrode]

[0115] Weigh out 4.25V positive electrode material LCO, conductive agent acetylene black, and binder PVDF 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 .

[0116] [negative electrode]

[0117] 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 .

[0118] [Electrolytes]

[0119] Example 1

[0120] Dissolve 1M lithium hexafluorophosphate and 0.2M lithium difluorosulfonylimide in a solvent with a mass ratio of ethylene carbonate / propylene carbonate / methyl ethyl carbonate / ethyl propionate / propyl propionate = 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.

[0121] Example 2-10

[0122] The experiment was essentially the same as in Example 1, except that the 1% compound 10 was replaced with compounds 1, 2, 3, 4, 5, 6, 7, 8 and 9, respectively.

[0123] Examples 11-14

[0124] The method is basically the same as in Example 1, except that the amount of compound 1 added is replaced with 0.3%, 0.5%, 1.5%, and 2%, respectively.

[0125] Examples 15-17

[0126] It is basically the same as Example 1, except that the 1% compound 10 added is replaced with compound 12, compound 14 and compound 15 respectively.

[0127] Comparative Example 1

[0128] It is essentially the same as Example 1, except that 1% of compound 10 is not added.

[0129] Comparative Examples 2-7

[0130] The experiment was basically the same as in Example 1, except that the 1% compound 10 was replaced with the same amount of propylene sulfate, vinyl sulfate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, compound 11, and compound 13.

[0131] Comparative Example 8

[0132] It is basically the same as Example 1, except that 0.8% lithium difluorophosphate, 0.5% lithium difluorodioxarate phosphate and 3% fluoroethylene carbonate are not added.

[0133] [Battery Manufacturing]

[0134] Using the above-mentioned positive and negative electrodes and the electrolytes prepared in Examples 1-17 and Comparative Examples 1-8, 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.

[0135] [Battery Cycle Performance Test]

[0136] 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 rate at 55℃ and at 0.2C rate 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%.

[0137] [Battery Discharge Performance Test at -40℃]

[0138] The battery was fully charged at room temperature using a 0.2C rate, then placed at -40°C for 4 hours and discharged using a 0.2C rate. The charge and discharge capacities were recorded, and the -40°C discharge percentage was calculated. Discharge percentage (%) = (-40°C discharge capacity / room temperature charge capacity) × 100%.

[0139] The test results of the above embodiments and comparative examples are shown in Table 1.

[0140] Table 1

[0141]

[0142]

[0143] 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), can improve the low-temperature performance of the battery, but it 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 has stronger thermal stability, and the high-temperature performance is significantly improved. However, the cycle performance at -20°C and the discharge performance at -40°C are somewhat reduced.

[0144] As can be seen from Comparative Example 2 and Examples 1-10, introducing a nitro group at the para site of propylene sulfate improves both the high-temperature and low-temperature performance of the battery. Further introducing 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 the para site further improves both low-temperature and high-temperature performance. In particular, when two nitro groups are introduced at the para site, the battery exhibits optimal performance in both high-temperature and low-temperature conditions. When hydrocarbon groups are further introduced at the para 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 introduced hydrocarbon group. Therefore, when further introducing hydrocarbon groups at the para site, the preferred number of carbon atoms in the hydrocarbon group is 1-6, more preferably 1-3. Furthermore, when the number of carbon atoms in the introduced hydrocarbon groups is the same, branched hydrocarbon groups show a more significant improvement in battery performance compared to straight-chain hydrocarbon groups.

[0145] As can be seen from Comparative Examples 2, 6, 7 and Examples 15-17, introducing only one hydrocarbon group (Comparative Example 6) or fluorine group (Comparative Example 7) at the para site of propylene sulfate does not significantly improve the high and low temperature performance of the battery. However, when two hydrocarbon groups, two fluorine groups, or one hydrocarbon group and one fluorine group are introduced at the para site, the high and low temperature performance of the battery can be further improved.

[0146] 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%.

[0147] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be included within the scope of protection of the invention.

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: R1 and R2 are independently selected from nitro, substituted or unsubstituted hydrocarbon, cyano, halogen or hydrogen, respectively, at least one of R1 and R2 is not hydrogen, and when one of R1 and R2 is hydrogen, the other is nitro.

2. The wide-temperature electrolyte according to claim 1, characterized in that: R1 and R2 are independently selected from nitro, substituted or unsubstituted hydrocarbon groups with 1 to 6 carbon atoms, or hydrogen, wherein the substituent of the hydrocarbon group is a halogen.

3. The wide-temperature electrolyte according to claim 2, characterized in that: R1 is a nitro group, and R2 is selected from nitro, hydrogen, alkyl or phenyl groups having 1 to 6 carbon atoms; or, R1 and R2 are each independently selected from alkyl groups or halogens having 1 to 3 carbon atoms.

4. The wide-temperature electrolyte according to claim 3, characterized in that: Additive A is selected from one or more substances with the following structural formulas:

5. The wide-temperature electrolyte according to any one of claims 1 to 4, characterized in that: At least one of R1 and R2 is a nitro group, and when only one is a nitro group, the other is selected from an alkyl group having 1 to 3 carbon atoms.

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 also includes additive B, which is selected from one or more of lithium difluorophosphate, lithium difluorodioxarate phosphate, and fluoroethylene carbonate.

8. The wide-temperature electrolyte according to claim 7, characterized in that: The additive B accounts for 1 to 10% of the total mass of the electrolyte.

9. The wide-temperature electrolyte according to claim 1, 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 organic solvents include cyclic carbonates, linear carbonates, and linear carboxylic esters.

10. The wide-temperature electrolyte according to claim 9, characterized in that: 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 selected from one or more of ethylene carbonate and propylene carbonate; and / or, The chain carbonate is ethyl methyl carbonate; and / or, The chain-like carboxylic ester is selected from 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).

11. 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 10.

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