5-Nitroisosorbitol derivatives, their preparation methods, and their applications in batteries

Abstract

This invention provides a 5-nitroisosorbide derivative, its preparation method, and its application in batteries. The 5-nitroisosorbide derivative is compound 1, compound 2, or compound 3. The preparation method of the 5-nitroisosorbide derivative includes the following steps: performing an electrophilic addition reaction of 5-mononitroisosorbide ester and a first reagent under a certain solvent and an acid-binding agent to obtain a primary product; or, performing an acylation reaction of 5-mononitroisosorbide ester and a second reagent under a certain solvent and an acid-binding agent to obtain a primary product; purifying and drying the primary product. This 5-nitroisosorbide derivative can be used as an additive in lithium-ion batteries, forming a good protective film at the interface of positive and negative electrode materials, while having low internal resistance, thus improving the low-temperature and rate performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of materials synthesis technology, and more particularly to a compound used in batteries, and even more particularly to 5-nitroisosorbide derivatives, their preparation methods, and their applications in batteries. Background Technology

[0002] 5-Nitroisosorbitol derivatives refer to a series of compounds derived from the 5-nitroisosorbitol group. Currently, 5-nitroisosorbitol derivatives are widely used clinically as nitric oxide donors in the treatment of cardiovascular diseases. As nitric oxide donors, 5-nitroisosorbitol derivatives can rapidly release high concentrations of nitric oxide under physiological conditions, thus exerting the physiological effects of nitric oxide.

[0003] Current 5-nitroisosorbitol derivatives are mainly based on 5-nitroisosorbitol and combine some drug active ingredients with groups. They can release some drug active agents and nitric oxide donor drugs 5-mononitroisosorbitol ester under the stimulation of high concentration of reactive oxygen species at the site of inflammation. While delivering nitric oxide, they can also clear high concentrations of reactive oxygen species at the site of inflammation, thus achieving the multifunctionality of nitric oxide donors.

[0004] Therefore, current substances of this type are targeted and not applicable to other technical fields. In order to expand the application of 5-nitroisosorbide derivatives, the derivatizing groups of 5-nitroisosorbide derivatives can be improved to seek more 5-nitroisosorbide derivatives that can be applied to other technical fields. Summary of the Invention

[0005] Based on the above problems, the purpose of this invention is to provide a new 5-nitroisosorbide derivative and its preparation method. This 5-nitroisosorbide derivative can be used in lithium-ion batteries to form a good protective film at the interface of positive and negative electrode materials, while having low internal resistance, which can improve the low temperature and rate performance of the battery.

[0006] To achieve the above objectives, the first aspect of the present invention provides a 5-nitroisosorbide derivative, which is compound 1, compound 2 or compound 3.

[0007]

[0008] The 5-nitroisosorbitol derivatives of the present invention, including compounds 1, 2 or 3, are novel 5-nitroisosorbitol derivatives with smaller molecules. They can form a good nitride protective film with lower solubility at the interface of positive and negative electrode materials, and have lower interfacial impedance. They can be used in electrolytes to improve the low-temperature and rate performance of batteries.

[0009] A second aspect of this invention provides a method for preparing 5-nitroisosorbide derivatives, comprising the steps of:

[0010] (1) 5-mononitroisosorbitol ester and the first reagent are subjected to an electrophilic addition reaction under certain solvent and acid-binding agent to obtain the primary product, or 5-mononitroisosorbitol ester and the second reagent are subjected to an acylation reaction under certain solvent and acid-binding agent to obtain the primary product.

[0011] (2) The primary product is purified and dried.

[0012] The preparation method of this invention is simple, utilizing an electrophilic addition reaction of 5-mononitroisosorbitol ester and a first reagent under the catalysis of an acid-binding agent, or an acylation reaction of 5-mononitroisosorbitol ester and a second reagent under the catalysis of an acid-binding agent. The obtained 5-nitroisosorbitol derivatives can improve the low-temperature and rate performance of batteries.

[0013] As a technical solution of the present invention, the first reagent is acrylonitrile, and the second reagent is a compound shown in structural formula one, wherein R is CF3 or OCH3, R' is OH, OCOR or OR'', and R'' is a C1 to C3 alkyl group.

[0014] As one technical solution of the present invention, the solvent includes at least one selected from water, dichloromethane, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, 1,4-dioxane, diethyl ether, benzene, toluene, acetonitrile, diethyl ether, cyclohexane, petroleum ether, tetrahydrofuran, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and propylene carbonate.

[0015] As a technical solution of the present invention, the acid-binding agent includes at least one of triethylamine, pyridine, 1,8-diazabicyclo[5.4.0]undec-7-ene, sodium hydroxide, potassium hydroxide, potassium carbonate and cesium carbonate.

[0016] As a technical solution of the present invention, the molar ratio of 5-mononitroisosorbide ester to the first reagent is 1:1 to 6, the molar ratio of 5-mononitroisosorbide ester to the second reagent is 1:1 to 6, and the molar ratio of the acid-binding agent to the 5-mononitroisosorbide ester is 1:0.5 to 6.0.

[0017] As one technical solution of the present invention, the reaction temperature of the addition reaction is 10-40°C, the reaction time of the addition reaction is 1-10h, the reaction temperature of the acylation reaction is 10-100°C, and the reaction time of the acylation reaction is 1-10h.

[0018] As one technical solution of the present invention, the purification method is washing, filtering or recrystallization.

[0019] A third aspect of the present invention provides the application of 5-nitroisosorbide derivatives in batteries.

[0020] A fourth aspect of the present invention provides an electrolyte comprising a non-aqueous organic solvent, an electrolyte salt, and an additive, wherein the additive comprises the aforementioned 5-nitroisosorbitol derivatives, and the 5-nitroisosorbitol derivatives account for 0.1 to 2.0% of the mass of the electrolyte. Attached Figure Description

[0021] Figure 1 This is the mass spectrum (hydrogen spectrum) of the product of Example 1.

[0022] Figure 2 This is the mass spectrum (hydrogen spectrum) of the product of Example 3.

[0023] Figure 3 This is the mass spectrum (fluorine spectrum) of the product of Example 3.

[0024] Figure 4 This is the mass spectrum (hydrogen spectrum) of the product of Example 5.

[0025] Figure 5 This is the mass spectrum (carbon spectrum) of the product of Example 5. Detailed Implementation

[0026] The 5-nitroisosorbitol derivatives of this invention can be used in material synthesis, pharmaceutical intermediates, and batteries. In particular, the 5-nitroisosorbitol derivatives, when used in secondary batteries such as lithium-ion or sodium-ion batteries, can improve the low-temperature and rate performance of secondary batteries as electrolyte additives.

[0027] Secondary batteries consist of a positive electrode active material, a negative electrode active material, and an electrolyte. In lithium-ion batteries, the positive electrode active material can be a layered transition metal lithium oxide or an olivine-type lithium compound. Layered transition metal lithium oxides can be, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (with the chemical formula LiNi). x Co y Mn (1-x-y) M zO₂, wherein 0.6≤x<0.9, x+y<1, 0≤z<0.08, and M is at least one selected from the group consisting of Al, Mg, Zr and Ti), and coatings and dopants of the above materials. The olivine-type lithium compound is lithium-containing phosphate having an olivine structure, which can be, but is not limited to, lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and coatings and dopants of the above materials. These positive electrode active materials may be used alone in only one type, or two or more types may be used in combination. When the secondary battery is a sodium-ion battery, the positive electrode active material may be a layered oxide, and the chemical formula of the layered oxide is Na x M (1-y-z) Fe y Mn z O₂, wherein M comprises at least one selected from the group consisting of Co, Ni, Cu, Mg, Zn, Al, Sn, Ga, Cr, Sr, V and Ti, 0<x≤1, 0≤y<1, 0≤z<1, and y+z≤1. Of course, the positive electrode material can also be other materials capable of producing ion deintercalation with sodium ions.

[0028] A negative active material comprises at least one selected from the group consisting of carbon-based materials, silicon-based materials and tin-based materials. Wherein, the carbon-based material can be, but is not limited to, at least one selected from the group consisting of artificial graphite, natural graphite, hard carbon, soft carbon, graphene and mesocarbon microspheres. The silicon-based material can be, but is not limited to, at least one selected from the group consisting of elemental silicon, silicon-oxygen composites, silicon-carbon composites and silicon alloy materials. The tin-based material can comprise elemental tin, tin-carbon composites, tin-oxygen composites, and tin alloy compounds.

[0029] An electrolyte comprises an electrolyte salt, a non-aqueous organic solvent and an additive.

[0030] If the secondary battery is a lithium-ion battery, then the electrolyte salt is a lithium salt. Furthermore, the electrolyte salt may be, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium di(oxalate)borate (C4BLiO8), lithium di(fluorooxalate)borate (C2BF2LiO4), lithium difluorophosphate (LiPO2F2), and lithium di(fluorobis(oxalate))phosphate (LiDFBP). If the secondary battery is a sodium-ion battery, then the electrolyte salt is a sodium salt. Furthermore, the electrolyte salt may be, but is not limited to, at least one of NaPF6, NaBF4, NaClO4, NaBOB (sodium difluoroborate), NaODFB (sodium difluoroborate), NaAsF6, NaSbF6, NaCF3SO3, NaN(SO2CF3)2, NaN(SO2C2F5)2, NaN(SO2C4F9)2, NaC(SO2CF3)3, NaPF2(C2O4)2, NaPF4(C2O4), NaB(CF3)4, and NaBF3(C2F5).

[0031] The non-aqueous organic solvent is selected from carbonates and / or carboxylic esters. Further, the non-aqueous organic solvent is selected from at least one of ethylene carbonate (PC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, and butyl propionate.

[0032] The additive is a 5-nitroisosorbide derivative, and further, the additive is compound 1, compound 2, or compound 3. The 5-nitroisosorbide derivative accounts for 0.1% to 2.0% of the electrolyte mass. As an example, the percentage of the 5-nitroisosorbide derivative may be, but is not limited to, 0.1%, 0.3%, 0.5%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, or 2.0%.

[0033]

[0034] The preparation method of 5-nitroisosorbide derivatives includes the following steps:

[0035] (1) 5-mononitroisosorbitol ester and the first reagent are subjected to an electrophilic addition reaction under certain solvent and acid-binding agent to obtain the primary product, or 5-mononitroisosorbitol ester and the second reagent are subjected to an acylation reaction under certain solvent and acid-binding agent to obtain the primary product.

[0036] (2) The primary product is purified and dried.

[0037] The first reagent is acrylonitrile, and the second reagent is the compound shown in structural formula 1, wherein R is CF3 or OCH3, R` is OH, OCOR or OR``, and R`` is a C1 to C3 alkyl group.

[0038]

[0039] If compound 1 is prepared, in step (1), 5-mononitroisosorbide ester and acrylonitrile undergo an electrophilic addition reaction, and the reaction formula is as follows.

[0040]

[0041] If compound 2 or 3 is to be prepared, in step (1), 5-mononitroisosorbide ester and the compound shown in structural formula 1 undergo an acylation reaction, the reaction formula of which is as follows.

[0042]

[0043] The solvent in step (1) includes at least one of water, dichloromethane, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, 1,4-dioxane, diethyl ether, benzene, toluene, acetonitrile, diethyl ether, cyclohexane, petroleum ether, tetrahydrofuran, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and propylene carbonate. The acid-binding agent includes at least one of triethylamine, pyridine, 1,8-diazabicyclo[5.4.0]undec-7-ene, sodium hydroxide, potassium hydroxide, potassium carbonate, and cesium carbonate. The molar ratio of 5-mononitroisosorbide ester to the first reagent is 1:1 to 6. For example, the molar ratio can be, but is not limited to, 1:1, 1:2, 1:3, 1:4, 1:5, or 1:6. The molar ratio of 5-mononitroisosorbide ester to the second reagent is 1:1 to 6. For example, the molar ratio can be, but is not limited to, 1:1, 1:2, 1:3, 1:4, 1:5, or 1:6. The molar ratio of the acid-binding agent to 5-mononitroisosorbide ester is 1:0.5 to 6.0. For example, the molar ratio can be, but is not limited to, 1:0.5, 1:1.0, 1:1.5, 1:2.0, 1:2.5, 1:3.0, 1:3.5, 1:4.0, 1:4.5, 1:5.0, 1:5.5, or 1:6.0. The addition reaction temperature is 10–40°C. For example, the reaction temperature can be, but is not limited to, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, or 40°C. The addition reaction time is 1–10 h. For example, the reaction time can be, but is not limited to, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, or 10 h. The acylation reaction temperature is 10–100°C. For example, the reaction temperature can be, but is not limited to, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C. The acylation reaction time is 1–10 h. For example, the reaction time can be, but is not limited to, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, or 10 h.

[0044] In step (2), the purification process involves washing, filtration, or recrystallization. Washing can be performed using hydrochloric acid solution, saturated saline solution, or water, and can be repeated multiple times. Filtration can be performed using centrifugation, vacuum filtration, or ordinary filtration. Recrystallization can be performed using a mixed solvent of ethanol and water, and drying can be performed using anhydrous sodium sulfate.

[0045] To better illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below with reference to specific embodiments. It should be noted that the methods described below are further explanations of this invention and should not be construed as limiting it.

[0046] Part 1: Preparation of 5-nitroisosorbide derivatives

[0047] Example 1

[0048] This embodiment describes the preparation of compound 1, which includes the following steps.

[0049] (1) In a 500ml three-necked flask, add 4.6g of sodium hydroxide, dissolve it in 200ml of water, place it in an ice bath and cool it to 0-5℃, add 20g of 5-mononitroisosorbide ester, stir for 30min, then slowly add 9.2ml of acrylonitrile, remove the ice bath after the addition is complete, react at room temperature for 3h, and after the reaction is complete, let it stand to separate into layers to obtain the lower layer of oily crude product.

[0050] (2) The lower layer of oily crude product was diluted with dichloromethane, washed successively with saturated brine and water, and the organic phases were combined. The product was then dried with anhydrous sodium sulfate to remove the dichloromethane, yielding 21.0 g of colorless and clear oily substance.

[0051] The yield of the colorless, clear oil was 82.0%. Mass spectrometry analysis of the obtained colorless, clear oil yielded the following results: Figure 1 As shown, the proton NMR spectrum contains 12 hydrogen atoms, consistent with the target structure. The characteristic triplet of the methylene group adjacent to the cyano group indicates that compound 1 has been synthesized.

[0052] Example 2

[0053] This embodiment describes the preparation of compound 1, which includes the following steps.

[0054] (1) In a 500ml three-necked flask, add 7.9g of potassium carbonate, dissolve it in 200ml of water, place it in an ice bath and cool it to 0-5℃, add 20g of 5-mononitroisosorbide ester, stir for 30min, then slowly add 9.2ml of acrylonitrile, remove the ice bath after the addition is complete, react at room temperature for 3h, and after the reaction is complete, let it stand to separate into layers to obtain the lower layer of oily crude product.

[0055] (2) The lower oily crude product was diluted with dichloromethane, washed successively with saturated brine and water, and the organic phases were combined. The product was then dried with anhydrous sodium sulfate to remove the dichloromethane, yielding a colorless and clear oily substance with a yield of 81.4%.

[0056] Example 3

[0057] This embodiment describes the preparation of compound 2, and the preparation method includes the following steps.

[0058] (1) In a 500ml three-necked flask, add 20g of 5-mononitroisosorbide ester and 200mL of dichloromethane as solvent, stir well, then add 10.12mL of pyridine, and then slowly add 17.7mL of trifluoroacetic anhydride under an ice bath. After the addition is complete, remove the ice bath and react at room temperature for 5h. After the reaction is complete, pour the solution into the prepared ice water.

[0059] (2) Wash the organic phases several times with 1N hydrochloric acid, saturated saline solution and water, combine the organic phases, dry with anhydrous sodium sulfate to remove dichloromethane and crystallize with ethanol to obtain a white solid.

[0060] The yield of the white solid obtained was 91.0%. Mass spectrometry analysis of the obtained white solid yielded the following results: Figure 2 and Figure 3 As shown, the proton spectrum contains 8 hydrogen atoms, consistent with the target structure. Figure 3 The characteristic peaks in the fluorine spectrum indicate that compound 2 has been synthesized.

[0061] Example 4

[0062] This embodiment describes the preparation of compound 2, and the preparation method includes the following steps.

[0063] (1) In a 500ml three-necked flask, add 20g of 5-mononitroisosorbide ester and 200mL of 1,4-dioxane as solvent, stir well, then add 10.12mL of pyridine, and then slowly add 17.7mL of trifluoroacetic anhydride under an ice bath. After the addition is complete, remove the ice bath and react at room temperature for 5h. After the reaction is complete, pour the solution into the prepared ice water.

[0064] (2) The mixture was washed several times with 1N hydrochloric acid, saturated saline solution and water, the organic phases were combined and dried with anhydrous sodium sulfate to remove dichloromethane and crystallized with ethanol to obtain a white solid. The yield of the white solid was 87.3%.

[0065] Example 5

[0066] This embodiment describes the preparation of compound 3, and the preparation method includes the following steps.

[0067] (1) In a 500ml three-necked flask, add 20g of 5-mononitroisosorbide ester, about 8.6g of potassium carbonate, and 200ml of dimethyl carbonate. Dimethyl carbonate is used as both a solvent and a second reagent in the reaction. The temperature is raised to 90℃ and kept at that temperature for 5h to obtain the reactants.

[0068] (2) The reactants were filtered to remove potassium carbonate, and then the excess dimethyl carbonate was removed under reduced pressure. The mixture was then recrystallized with a ethanol / water (1:4, v / v) mixed solvent and dried under vacuum (60℃, 4h) to obtain a white powder.

[0069] The yield of the obtained white powder was 92.0%. Mass spectrometry analysis of the obtained white powder yielded the following results: Figure 4 and Figure 5 As shown, the proton NMR spectrum contains 11 hydrogen atoms, consistent with the target structure. The chemical shift at 3.75 ppm is a characteristic singlet for a terminal methyl group. Figure 5The carbon spectrum showed a total of 8 carbons, consistent with the target structure. The characteristic peak of the carbonate carbonyl group at a chemical shift of 154 ppm further confirmed the synthesis of compound 3.

[0070] Example 6

[0071] This embodiment describes the preparation of compound 3, and the preparation method includes the following steps.

[0072] (1) In a 500ml three-necked flask, add 20g of 5-mononitroisosorbide ester, about 5g of sodium hydroxide, and 200ml of dimethyl carbonate. Dimethyl carbonate is used as both a solvent and a second reagent in the reaction. Stir well, heat to 90℃ and keep warm for 5h to obtain the reactant.

[0073] (2) The reactants were filtered to remove sodium hydroxide, and then excess dimethyl carbonate was removed under reduced pressure. The mixture was then recrystallized with a ethanol / water (1:4, v / v) mixed solvent and dried under vacuum (60°C, 4h) to obtain a white powder. The yield of the white powder was 87.0%.

[0074] Part Two: Applications of 5-Nitroisosorbitol Derivatives in Batteries

[0075] 1.1 Preparation of non-aqueous electrolyte:

[0076] In a nitrogen-filled glove box (O2 < 1 ppm, H2O < 1 ppm), 87 g of a mixed solvent obtained by uniformly mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a mass ratio of 3:7 was used as the organic solvent. Then, 1 g of compound 1 obtained in Example 1, compound 2 obtained in Example 3, and compound 3 obtained in Example 5 were added to obtain mixed solutions. The mixed solutions were sealed and packaged and frozen in a freezer (-4°C) for 2 hours. After being removed, 12 g of lithium hexafluorophosphate (LiPF6) was slowly added to the mixed solutions in a nitrogen-filled glove box (O2 < 1 ppm, H2O < 1 ppm). After uniform mixing, non-aqueous electrolyte 1#, non-aqueous electrolyte 2#, and non-aqueous electrolyte 3# were prepared.

[0077] In a nitrogen-filled glove box (O2 < 1 ppm, H2O < 1 ppm), 87 g of a mixed solvent obtained by thoroughly mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a mass ratio of 3:7 was used as the organic solvent. 88 g of another mixed solvent obtained by thoroughly mixing these were then used as the organic solvent. The organic solvent was sealed and packaged, then frozen in a freezer (-4°C) for 2 hours. After removal, 12 g of lithium hexafluorophosphate (LiPF6) was slowly added to the mixed solution in a nitrogen-filled glove box (O2 < 1 ppm, H2O < 1 ppm). After thorough mixing, non-aqueous electrolyte #4 was prepared.

[0078] 1.2 Preparation of the positive electrode:

[0079] A lithium-ion battery positive electrode slurry of a certain viscosity was prepared by uniformly mixing lithium iron phosphate material LiFePO4, conductive agent SuperP, binder PVDF, and carbon nanotubes (CNT) in a mass ratio of 96.5:1.5:1:1. This slurry was then coated onto aluminum foil used for current collectors, with a coating weight of 165.5 g / m². 2 After drying at 85℃, the material is cold-pressed; then it is trimmed, cut into pieces, and slit. After slitting, it is dried at 85℃ for 4 hours under vacuum conditions, and then the tabs are welded to produce a lithium-ion battery positive electrode sheet that meets the requirements.

[0080] 1.3 Preparation of the negative electrode:

[0081] Artificial graphite, conductive agent SuperP, thickener CMC, and binder SBR (styrene-butadiene rubber latex) are mixed in a mass ratio of 95:1.5:1.0:2.5 to form a slurry. The mixture is then coated on both sides of a copper foil, dried, and rolled to obtain a negative electrode sheet, thus producing a lithium-ion battery negative electrode sheet that meets the requirements.

[0082] 1.4 Preparation of lithium-ion batteries:

[0083] The positive electrode, negative electrode, and separator prepared according to the above process are stacked to form lithium-ion batteries with a thickness of 4.7 mm, a width of 55 mm, a length of 60 mm, and a total capacity of 2 Ah. These batteries are then vacuum-baked at 75°C for 10 hours, and non-aqueous electrolytes 1#, 2#, 3#, and 4# are injected respectively. After standing for 24 hours, the batteries are charged to 3.65V using a constant current of 0.1C (200 mA), and then charged at a constant voltage of 3.65V until the current drops to 0.05C (100 mA). They are then discharged to 2.5V at 0.2C (400 mA), and this charge-discharge cycle is repeated twice. Finally, the batteries are charged to 3.65V at 0.1C (200 mA), completing the fabrication of lithium-ion batteries 1#, 2#, 3#, and 4#.

[0084] Performance tests were conducted on lithium-ion batteries #1, #2, #3, and #4. The test results are shown in Table 1. The test conditions are as follows.

[0085] (1) High-rate cycling performance test

[0086] Under normal temperature (25℃) conditions, the lithium-ion battery was subjected to one 3.0C / 3.0C charge and discharge cycle (the battery discharge capacity was recorded as C0), with an upper limit voltage of 4.1V; then, it was subjected to 500 cycles of 3.0C / 3.0C charge and discharge, and the capacity retention rate was calculated.

[0087] Capacity retention rate = (Battery capacity after 500 cycles C1 / Initial battery capacity C0) * 100%

[0088] (2) Low-temperature discharge test

[0089] Under normal temperature (25℃) conditions, a lithium-ion battery is subjected to a 0.5C / 0.5C charge-discharge cycle (battery cutoff voltage 3.0V, discharge capacity C0), with an upper limit voltage of 4.1V (cutoff current 0.05C). Then, the battery is fully charged to 4.1V at 0.5C (cutoff current 0.05C) at room temperature (25℃), and then transferred to -20℃ for 4 hours. It is then discharged at 0.5C to 3.0V, with a discharge capacity of C1. The capacity retention rate is calculated.

[0090] Capacity retention rate = (C1 / C0) * 100%

[0091] Table 1. Electrochemical performance test results for each example.

[0092]

[0093] As shown in Table 1, the cycle, low-temperature and rate performance of lithium-ion batteries 1# to 3# are better than that of lithium-ion battery 4#. This is because lithium-ion batteries 1# to 3# use 5-nitroisosorbide derivatives as additives, which can form a good nitride protective film with lower solubility at the interface of positive and negative electrode materials, resulting in lower interface impedance and thus improving the low-temperature and rate performance of the battery.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An electrolyte comprising a non-aqueous organic solvent, an electrolyte salt, and additives, characterized in that, The additive includes a 5-nitroisosorbide derivative, which accounts for 0.1-2.0% of the electrolyte by mass, and the 5-nitroisosorbide derivative is compound 2. Compound 2.

2. The electrolyte according to claim 1, characterized in that, The preparation method of the 5-nitroisosorbide derivative includes the following steps: (1) The 5-mononitroisosorbitol ester with the following structural formula and the second reagent were subjected to an acylation reaction under certain solvent and acid-binding agent to obtain the primary product; (2) The primary product is purified and dried. 。 3. The electrolyte according to claim 2, characterized in that, The second reagent is a compound shown in structural formula 1, wherein R is CF3, R' is OH, OCOR or OR'', and R'' is a C1~C3 alkyl group. Structure 1.

4. The electrolyte according to claim 2, characterized in that, The solvent includes at least one of water, dichloromethane, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, 1,4-dioxane, diethyl ether, benzene, toluene, acetonitrile, diethyl ether, cyclohexane, petroleum ether, tetrahydrofuran, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and propylene carbonate.

5. The electrolyte according to claim 2, characterized in that, The acid-binding agent includes at least one of triethylamine, pyridine, 1,8-diazabicyclo[5.4.0]undec-7-ene, sodium hydroxide, potassium hydroxide, potassium carbonate, and cesium carbonate.

6. The electrolyte according to claim 2, characterized in that, The molar ratio of the 5-mononitroisosorbide ester to the second reagent is 1:1 to 6, and the molar ratio of the acid-binding agent to the 5-mononitroisosorbide ester is 1:0.5 to 6.

0.

7. The electrolyte according to claim 2, characterized in that, The acylation reaction is carried out at a temperature of 10~100℃ and for a time of 1~10h.

8. The electrolyte according to claim 2, characterized in that, The purification methods include washing, filtration, or recrystallization.

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