Electrolyte, battery, and electricity-using device

Abstract

The present application provides an electrolyte, a battery, and an electrical device, relating to the field of battery technology. The solvent of the electrolyte includes a compound having both a phosphite group and a cyclic ether group, so that the electrolyte has excellent safety and flame retardant properties when used in an alkali metal battery, and has good stability with the metal negative electrode, thereby significantly improving the cycle stability and safety of the battery.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to an electrolyte, a battery, and an electrical device. Background Art

[0002] Carbonates and ethers are common solvents in alkali metal battery electrolytes. However, when conventional carbonate and ether solvents are used with alkali metal battery electrodes (such as sodium battery electrodes), they can lead to problems such as lithium dendrite growth, electrolyte decomposition, and low Coulombic efficiency at the metal anode. These issues lead to significant safety risks and short cycle life for alkali metal batteries. Currently, the safety of electrolytes is often improved by adding flame-retardant solvents, such as phosphate compounds.

[0003] However, conventional phosphate ester compounds have poor solubility in electrolyte salts used in electrolytes, such as sodium salts. Therefore, the added content of these solvents is usually less than 10%. When the electrolyte is exposed to flames or high temperatures, the phosphate ester flame retardant is easily consumed quickly, and the remaining electrolyte is easily ignited, which has limited improvement in electrolyte safety. In addition, common phosphate ester compounds have high LUMO energy levels, poor reduction stability, high polarity, strong interactions with sodium ions, and a high proportion of the solvation shell. During charging, the solvated sodium ions migrate to the negative electrode for reduction. When the solvation structure is removed, the phosphate ester solvation shell is easily decomposed. Therefore, excessive addition of phosphate esters can also lead to a rapid decline in battery cycle life. Moreover, due to the high polarity of phosphate ester compounds, they also have poor wettability with common separators used in alkali metal batteries, such as ordinary PP and PE separators.

[0004] Therefore, the flame retardant effect of phosphate compounds added to the electrolyte is limited, and alkali metal batteries still have problems such as short battery cycle life and poor safety performance. Summary of the Invention

[0005] The purpose of this application is to provide an electrolyte to improve the problems of short battery cycle life and poor safety performance.

[0006] To achieve the above objectives, this application provides the following technical solutions:

[0007] The present application provides an electrolyte solution, including an organic solvent and an electrolyte salt. The electrolyte solution also includes a second solvent, and the second solvent is a phosphite compound having a structure shown in Formula I:

[0008]

[0009] Formula I

[0010] R1 and R2 are each independently selected from a C1-C5 alkyl group, a partially fluorinated or perfluorinated C1-C5 alkyl group, and a substituted or unsubstituted benzene ring.

[0011] Furthermore, in some embodiments of the present application, the phosphite compound represented by Formula I includes at least one of compounds 1-8.

[0012]

[0013]

[0014]

[0015] Furthermore, in some embodiments of the present application, the molar ratio of the organic solvent to the phosphite compound is (6:1) to (1:3).

[0016] Furthermore, in some embodiments of the present application, the organic solvent includes one or more of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl acetate (EA), 2,2-difluoroethyl acetate (DFEA), acetonitrile (AN), ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether or tetrahydrofuran.

[0017] Furthermore, in some embodiments of the present application, based on the mass of the electrolyte being 100%, the total content of the organic solvent and the phosphite compound is 55% to 95%.

[0018] Furthermore, in some embodiments of the present application, the electrolyte salt includes one or more of XPF6, XClO4, XBF4, XAsF6, XFSI, XTFSI, XBOB, XODFB, XCF3SO3, XPO2F2 or XOTFB, wherein X is selected from Li, Na or K.

[0019] Furthermore, in some embodiments of the present application, the concentration of the electrolyte salt relative to the electrolyte is 0.8-1.2 mol / L.

[0020] Furthermore, in some embodiments of the present application, the electrolyte also includes functional additives.

[0021] Furthermore, in some embodiments of the present application, based on the mass of the electrolyte being 100%, the content of the functional additive is 0.5% to 4.5%.

[0022] Furthermore, in some embodiments of the present application, the functional additives include one or more of vinylene carbonate (VC), 1,3-propane sultone (1,3-PS), fluoroethylene carbonate (FEC), phthaleinsulfathiazole (PST), diethyl sulfate (DTD), and difluorooxaloyl borate (XODFB, where X is selected from Li, Na, and K).

[0023] The present application also provides a battery comprising a positive electrode sheet, a negative electrode sheet, a separator and the above-mentioned electrolyte.

[0024] Furthermore, in some embodiments of the present application, the battery is an alkali metal battery.

[0025] Furthermore, in some embodiments of the present application, the battery may be a lithium metal battery, a sodium metal battery, or a potassium metal battery.

[0026] The present application also provides an electrical device comprising a battery containing the above-mentioned electrolyte.

[0027] The present application provides an electrolyte solution, in which a phosphite compound is added to the solvent. The phosphite compound includes a phosphite group and a cyclic ether group, and has the following excellent effects:

[0028] (1) The electrolyte provided in the present application adds a compound containing both a cyclic ether group and a phosphite group to the solvent, so that the phosphite compound has better compatibility with the electrolyte system and the electrode. The amount of the phosphite compound added can exceed the upper limit of the addition amount of conventional phosphate compounds due to their poor solubility in electrolytic salts, thereby providing the electrolyte with better safety and flame retardant properties. In addition, the phosphite compound also has better safety and flame retardant properties than the phosphate compound.

[0029] (2) The phosphite groups in the phosphite compounds contained in the electrolyte provided by the present application can not only improve the oxidative stability of the cyclic ether groups, but also avoid the problem of fluorination reducing the lithium / sodium salt solubility of ether solvents.

[0030] (3) Conventional phosphite compounds have weak film-forming ability, while the phosphite compounds contained in the electrolyte provided by this application introduce cyclic ether groups on the phosphite groups, which can enable the compounds to have certain film-forming ability and can achieve ring-opening polymerization under electrophilic attack to form low-chain polyethers, so that the formed negative electrode interface has better ability to adapt to the drastic changes in volume under the metal system, thereby improving the cycle stability of the battery cell.

[0031] (4) The phosphite compounds contained in the electrolyte provided in this application can neutralize the Lewis acid PF5, reduce HF corrosion, and alleviate the decomposition and gas production of components such as sodium carbonate at the positive and negative electrode interfaces.

[0032] (5) When R1 and R2 in the structure of the phosphite compound contained in the electrolyte provided by the present application are replaced by phenyl groups, the electrolyte has a lower surface tension. The low surface tension makes it easier for the electrolyte to spread between the electrode micropores and the diaphragm fibers, reducing the solid-liquid contact angle, accelerating the capillary-driven penetration process, shortening the wetting time, and facilitating industrial production. When R1 and R2 in the structure of the phosphite compound contained in the electrolyte provided by the present application are replaced by fluorophenyl groups, the fluorophenyl groups can reduce the continuous decomposition of the solvent during the cycle by optimizing the SEI composition (such as increasing the LiF or NaF content), thereby alleviating the problem of late wettability degradation caused by electrolyte consumption.

[0033] (6) The electrolyte provided in this application uses phosphite compounds as solvents, which have good compatibility with ether solvents and can achieve complementary advantages with commonly used ethers. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0035] Figure 1 is the mass spectrum of compound 1 of the present application;

[0036] Figure 2 This is the mass spectrum of compound 2 of the present application;

[0037] Figure 3 This is the nuclear magnetic resonance image of compound 1 of the present application;

[0038] Figure 4 This is the nuclear magnetic resonance image of compound 2 of the present application. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions of this application in conjunction with the embodiments. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0040] Both phosphate and phosphite compounds can provide a certain degree of flame retardancy when used as electrolyte solvents. However, phosphate compounds have problems such as poor solubility in electrolyte salts, which limits their inclusion rate and leads to poor flame retardancy. Traditional phosphites (such as trimethyl phosphite and triethyl phosphite) are highly destructive to graphite, hard carbon, and metal systems, and also have weak film-forming ability, resulting in poor battery cycling stability. Therefore, while phosphite compounds can improve the safety and flame retardancy of electrolytes to a certain extent, they are not commonly used in electrolytes.

[0041] Ether solvents are commonly used as electrolyte solvents due to their excellent reduction stability, but their poor oxidation resistance hinders their widespread application in high-voltage systems. Currently, conventional improvement methods mainly involve fluorination of ether compounds, but fluorination reduces the ether solvent's ability to dissolve lithium / sodium salts. For example, fluorinated ether diluents exhibit almost no solubility for lithium / sodium salts.

[0042] Based on this, in order to solve the above problems, the applicant in this application uses phosphite groups and cyclic ether groups to form a new type of phosphite compound as an electrolyte solvent, which improves the safety, flame retardancy and stability of the electrolyte, thereby improving the cycle stability and safety performance of the battery.

[0043] In a first aspect, an embodiment of the present application provides an electrolyte solution comprising an organic solvent and an electrolyte salt. The electrolyte solution further comprises a second solvent, wherein the second solvent is a phosphite compound having a structure shown in Formula I:

[0044]

[0045] Formula I

[0046] R1 and R2 are each independently selected from a C1-C5 alkyl group, a partially fluorinated or perfluorinated C1-C5 alkyl group, and a substituted or unsubstituted benzene ring.

[0047] The electrolyte described in this application has good safety and flame retardant properties because the solvent contains phosphite groups. When a fire occurs, the phosphite groups achieve gas-phase flame retardancy by capturing free radicals in the combustion chain reaction, significantly shortening the self-extinguishing time (SET) of the electrolyte. At the same time, the phosphite groups can increase the flash point of the electrolyte, thereby suppressing fire and explosion caused by thermal runaway of the battery.

[0048] The electrolyte solvent described in the present application further introduces a cyclic ether group on the basis of the phosphite structure, which can enable the compound to have a certain film-forming ability, and can achieve ring-opening polymerization under electrophilic attack to form a low-chain polyether, so that the formed negative electrode interface has a good ability to adapt to the drastic change in volume under the metal system, thereby improving the cycle stability of the battery cell; and the simultaneous presence of the phosphite group and the cyclic ether group, the phosphite group can not only improve the oxidative stability of the cyclic ether group, but also avoid the reduction of the lithium / sodium salt solubility of the ether solvent by fluorination. For example, fluoroether diluents show almost no solubility in lithium / sodium salts, while the phosphite compound described in the present application has a certain degree of lithium / sodium salt solubility.

[0049] In addition, the phosphite compounds described in this application can be used as electrolyte solvents to neutralize Lewis acid PF5, reduce HF corrosion, and alleviate the decomposition and gas production of components such as sodium carbonate at the positive and negative electrode interfaces.

[0050] In some embodiments, the phosphite compound represented by Formula I includes at least one of Compounds 1-8.

[0051]

[0052]

[0053]

[0054] Preferably, when R1 and R2 in the compound structure described in the present application are replaced by phenyl groups (such as compound 2), they have lower surface tension. The low surface tension makes it easier for the electrolyte to spread between the electrode micropores and the diaphragm fibers, reduces the solid-liquid contact angle, accelerates the capillary action-driven penetration process, shortens the infiltration time, and is beneficial to industrial production.

[0055] Preferably, when R1 and R2 in the compound structure described in the present application are replaced by fluorophenyl groups (such as compounds 5-8), the fluorophenyl group can reduce the continuous decomposition of the solvent during the cycle by optimizing the SEI composition (such as increasing the LiF or NaF content), thereby alleviating the problem of late wettability degradation caused by electrolyte consumption.

[0056] In some embodiments, the molar ratio of the organic solvent to the phosphite compound is (6:1) to (1:3).

[0057] Preferably, the molar ratio of the organic solvent to the phosphite compound is (5:1) to (1:2).

[0058] A molar ratio of organic solvent to phosphite compound exceeding 6:1 in the electrolyte results in a low proportion of phosphite, resulting in poor flame retardancy. A molar ratio below 1:3 can lead to poor cycling performance. However, a molar ratio of organic solvent to phosphite compound between 5:1 and 1:2 can lower the resistance of the battery cell while maintaining the electrolyte's flame retardancy and cycling stability.

[0059] In some embodiments, the organic solvent includes at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl acetate (EA), 2,2-difluoroethyl acetate (DFEA), acetonitrile (AN), ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether or tetrahydrofuran.

[0060] Preferably, the organic solvent includes one or more ether solvents such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether or tetrahydrofuran.

[0061] The compounds described in this application have good compatibility with ether solvents, complementing the advantages of commonly used ethers. For example, diethylene glycol dimethyl ether primarily dissolves lithium salts, while the compounds described in this application focus on multifunctionality, complementing the advantages.

[0062] In some embodiments, based on the mass of the electrolyte being 100%, the total content of the organic solvent and the phosphite compound is 55% to 95%.

[0063] In some embodiments, the electrolyte salt includes one or more of XPF6, XClO4, XBF4, XAsF6, XFSI, XTFSI, XBOB, XODFB, XCF3SO3, XPO2F2 or XOTFB, wherein X is selected from Li, Na or K.

[0064] In some embodiments, the concentration of the electrolyte salt relative to the electrolyte solution is 0.8-1.2 mol / L.

[0065] In some embodiments, the electrolyte further includes a functional additive.

[0066] In some embodiments, based on the mass of the electrolyte being 100%, the content of the functional additive is 0.5-4.5%.

[0067] In some embodiments, the functional additives include one or more of vinylene carbonate (VC), 1,3-propane sultone (1,3-PS), fluoroethylene carbonate (FEC), phthaleinsulfathiazole (PST), dithiodifluoroethane (DTD), and difluorooxalatoborate (XODFB, where X is selected from Li, Na, and K).

[0068] Secondly, embodiments of the present application further provide a battery comprising a positive electrode sheet, a negative electrode sheet, a separator, and the aforementioned electrolyte. The positive electrode sheet material may be any material that can be used as a positive electrode sheet for an alkali metal battery. The selection of the positive electrode sheet material is not a novelty of the present application, and those skilled in the art can select the positive electrode sheet based on existing techniques. Therefore, this is not specifically limited in the present application.

[0069] The negative electrode plate material can be any material that can be used as the negative electrode plate of an alkali metal battery, and the selection of the negative electrode plate material is not the innovation of this application. Those skilled in the art can select the negative electrode plate based on the existing technology, so it is not specifically limited in this application.

[0070] As a commonly used negative electrode plate material, it can be modified by using any one of the following technologies: three-dimensional porous structure construction, lithium / sodium / potassium-philic coating, artificial solid electrolyte interface membrane carbon-based material coating, gradient / composite functional coating, and alloying layer.

[0071] The diaphragm can be made of any material that can be used as an alkali metal battery diaphragm, and the selection of the diaphragm material is not the innovation of this application. Those skilled in the art can select the diaphragm based on the existing technology, so it is not specifically limited in this application.

[0072] As a commonly used separator, any one of polyethylene membrane, polypropylene membrane or composite ceramic membrane may be considered.

[0073] In some embodiments, the battery is an alkali metal battery.

[0074] In some embodiments, the battery may be a lithium metal battery, a sodium metal battery, a potassium metal battery, or the like.

[0075] In a third aspect, the present application also provides an electrical device comprising a battery containing the above-mentioned electrolyte.

[0076] In order to make the above implementation details and operations of this application clearly understood by those skilled in the art, and to significantly demonstrate the improved performance of the electrolyte provided by the embodiments of this application, the above technical solution is illustrated by examples below.

[0077] 1. Raw materials

[0078] Diethylene glycol dimethyl ether, tetrahydrofuran, and sodium hexafluorophosphate were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; additives were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. or Shanghai Myrel Biochemical Technology Co., Ltd., and other reagents were commercially available; raw materials such as 3,4-difluorophenol were purchased from Beijing Inokai Technology Co., Ltd.; and anhydrous ethanol was purchased from Shanghai Adamas Reagent Co., Ltd.

[0079] 2. Synthesis steps of phosphite compounds

[0080] Synthesis steps of compound 1: At a low temperature of -78°C, tetrahydrofuran (THF) and a strong base (n-BuLi) are used with the assistance of a directing group (DMG) (-CONEt2) to generate 2-lithiated tetrahydrofuran. The temperature is raised to 0°C, and anhydrous ethanol, a solvent (petroleum ether), and an acid-binding agent (such as N,N-dimethylaniline) are added to the reactor. The petroleum ether solution of PCl3 is added dropwise under negative pressure. After the addition is completed, the temperature is raised to finally obtain the product.

[0081] The synthetic route is as follows:

[0082]

[0083] Synthesis steps of compound 2: At a low temperature of -78°C, THF and a strong base (n-BuLi) are used with the assistance of a directing group (DMG) (-CONEt2) to generate 2-lithiated tetrahydrofuran. The temperature is raised to 30°C while PCl3 and molten phenol are added dropwise. MgCl2 needs to be added continuously during the process to finally obtain the product.

[0084] The synthetic route is as follows:

[0085]

[0086] The synthesis steps of compound 3 are the same as those of compound 1, except that anhydrous ethanol is replaced by anhydrous butanol.

[0087] The synthesis steps of compound 4 are the same as those of compound 1, except that anhydrous ethanol is replaced by anhydrous methanol.

[0088] Synthesis steps of compound 5: Same as the synthesis steps of compound 2, except that molten phenol was replaced with 3,4-difluorophenol (CAS No.: 2713-33-9).

[0089] Synthesis steps of compound 6: Same as the synthesis steps of compound 2, except that molten phenol was replaced with 3,5-difluorophenol (CAS No.: 2713-34-0).

[0090] Synthesis steps of compound 7: Same as the synthesis steps of compound 2, except that molten phenol was replaced with 4-fluorophenol (CAS No.: 371-41-5).

[0091] Synthesis steps of compound 8: Same as the synthesis steps of compound 2, except that molten phenol was replaced with 3-fluorophenol (CAS No.: 206-748-6).

[0092] 3. Compound detection

[0093] Some of the above compounds were selected for mass spectrometry testing, and the mass spectra are shown in Figure 1 and Figure 2 , see NMR images Figure 3 and Figure 4 .

[0094] 4. Electrolyte preparation steps

[0095] In a glove box filled with argon (H2O < 0.1 ppm, O2 < 0.1 ppm), a certain mass of diethylene glycol dimethyl ether and the above-prepared phosphite compound were weighed and mixed evenly. After cooling, NaPF6 and additives were added and stirred evenly to obtain an electrolyte.

[0096] 5. Battery preparation steps

[0097] The battery described in this application is an alkali metal battery, and the preparation steps of a sodium battery are listed below as an example.

[0098] (1) Preparation of positive electrode sheet: Sodium iron pyrophosphate, carbon black and PVDF are homogenized in NMP solution at a mass ratio of 94:3:3. The positive electrode slurry is coated on the current collector, and then dried, rolled and striped to obtain a positive electrode sheet that can be directly stacked.

[0099] (2) Preparation of negative electrode sheet: die-cut aluminum foil.

[0100] (3) Cell production: The positive and negative electrodes after stripping are stacked on a stacking machine. The separator is made of a three-layer material of PP / PE / PP to form a soft-pack cell.

[0101] (4) Liquid injection, formation and aging:

[0102] After the battery cells were dried at high temperature, the electrolytes of the embodiment and the comparative example were injected into the soft-pack battery cells.

[0103] After the electrolyte is injected, the sodium battery undergoes initial packaging, surface cleaning and other processes to complete the preliminary work, and is placed at room temperature for one day.

[0104] The formation was carried out by a step-by-step formation method. The first step was a formation current of 0.05C, and constant current charging was performed for 2 h. The second step was a formation current of 0.1C, and constant current charging was performed until the voltage reached 3.4 V.

[0105] After the formation, it is aged at 50℃ for one day and then cooled to room temperature for final sealing.

[0106] 6. Performance Testing

[0107] NFPP soft-pack batteries were used to conduct 25°C and 45°C cycling and safety performance tests. The above tests were performed with the help of the Xinwei charge and discharge test system.

[0108] (1) 25℃ cycle performance test

[0109] At 25° C., the sodium batteries obtained in the examples and comparative examples were charged to 3.4 V at a constant current and constant voltage of 0.5 C, allowed to stand for 5 minutes, and then discharged to 2.0 V at a constant current of 1 C. The above is one charge / discharge cycle.

[0110] Capacity retention rate (%) of sodium battery after 150 cycles at 25℃ = (discharge capacity at the 150th cycle / first discharge capacity) × 100%.

[0111] (2) 45℃ high temperature cycle performance test

[0112] At 45° C., the sodium batteries obtained in the examples and comparative examples were charged to 3.4 V at a constant current and constant voltage of 0.5 C. After standing for 5 minutes, they were discharged to 2.0 V at a constant current of 1 C. The above is one charge / discharge cycle.

[0113] Capacity retention rate of 45℃ sodium battery after 150 cycles (%) = (discharge capacity at the 150th cycle / first discharge capacity) × 100%.

[0114] (3) DC resistance after 150 cycles at 45°C

[0115] At 45°C, after 150 cycles, the sodium batteries of the embodiment and comparative example were placed in a constant temperature box at 25°C for 30 minutes, charged to 3.4V at 1C constant current and constant voltage, left standing for 30 minutes, and discharged to 50% SOC at 1C. After standing for 60 minutes, the corresponding voltage value U1 was recorded; finally, the battery was charged at 4C (the current was set to I 4C ) Discharge for 30 seconds and record the corresponding voltage value U2. Calculate the DCR value R according to the following formula:

[0116] R=(U1-U2) / (I 4C ).

[0117] (4) Needle puncture, 130℃ hot box test

[0118] Acupuncture: At 25°C, the sodium batteries obtained in the examples and comparative examples were charged to 3.4V at a constant current and constant voltage of 0.5C, left for 30 min, and then penetrated the battery cells perpendicular to the steel plate with a φ5mm steel needle at a speed of (25±2)mm / s. The needle remained in the battery cells and was observed for 1 hour. The pass rate was calculated (three battery cells in each group).

[0119] 130℃ hot box: At 25℃, the sodium batteries obtained in the examples and comparative examples were charged to 3.4V at 0.5C constant current and constant voltage, and left for 30 minutes. The batteries were then transferred to a test box, which was heated at a temperature rise rate of 5℃ / min. When the temperature in the box reached 130℃, it was kept at a constant temperature for 30 minutes. If the battery cell did not fail, it was heated at a rate of 5℃ / min, and each temperature was maintained for 30 minutes until the battery cell failed. The limit temperature was 150℃, and the pass rate was counted (three battery cells in each group).

[0120] Examples 1-12 and Comparative Examples 1-7

[0121] According to the above electrolyte preparation steps, the electrolytes of Examples 1-10 and Comparative Examples 1-4 were prepared respectively with reference to the electrolyte components and contents in Table 1.

[0122] Table 1 Electrolyte composition

[0123]

[0124] The electrolytes obtained in Examples 1-12 and Comparative Examples 1-7 were applied to sodium ion batteries and tested according to the room temperature (25°C) cycle performance test and 45°C high temperature cycle performance test methods, as well as the needle penetration and 130°C hot box test methods in the above performance tests. The cycle test results shown in Table 2 and the hot box and needle penetration test results shown in Table 3 were obtained.

[0125] Table 2 Cyclic test results

[0126]

[0127] Table 3 Acupuncture and 130℃ hot box test results

[0128]

[0129] It can be seen from Table 2 and Table 3 that, compared with Comparative Example 1, Examples 1-13 containing the phosphite compounds described in the present application have better cycle capacity retention and safety performance, and do not increase the DC impedance of the battery within a suitable addition range.

[0130] By comparing Examples 1-5, it can be seen that when ether compounds, phosphate compounds and / or ether compounds, phosphite compounds and ether solvents are used as solvents to prepare electrolytes respectively and applied to batteries, the cycle performance and safety performance of the batteries are improved poorly. Combined with Examples 1-13, it can be seen that the compounds described in the present application contain both phosphite groups and cyclic ether groups, and exhibit relatively excellent cycle performance and safety performance.

[0131] Comparison of Examples 1, 9, and 10 with Comparative Example 6 demonstrates that when the molar ratio of the organic solvent to the phosphite compound in the electrolyte described herein is controlled between (6:1) and (1:3), the resulting battery exhibits excellent room temperature cycling performance, 45°C high-temperature cycling performance, and safety. A molar ratio exceeding 6:1 (i.e., an excessive proportion of organic solvent) significantly degrades the safety of the battery cell.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An electrolyte solution comprising an organic solvent and an electrolyte salt, characterized in that: The electrolyte further includes a second solvent, which is a phosphite compound having a structure shown in Formula I: Formula I In formula I, R1 and R2 are each independently selected from a C1-C5 alkyl group, a partially fluorinated or perfluorinated C1-C5 alkyl group, or a substituted or unsubstituted benzene ring.

2. The electrolyte according to claim 1, characterized in that The phosphite compound shown in formula I includes at least one of compounds 1-8, 。 3. The electrolyte according to claim 1 or 2, characterized in that The molar ratio of the organic solvent to the phosphite compound is (6:1) to (1:3).

4. The electrolyte according to claim 1 or 2, characterized in that The organic solvent includes one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, ethyl acetate, 2,2-difluoroethyl acetate, acetonitrile, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether or tetrahydrofuran.

5. The electrolyte according to claim 4, characterized in that Based on the mass of the electrolyte being 100%, the total content of the organic solvent and the phosphite compound is 55% to 95%.

6. The electrolyte according to any one of claims 1 or 2, characterized in that The electrolyte salt includes one or more of XPF6, XClO4, XBF4, XAsF6, XFSI, XTFSI, XBOB, XODFB, XCF3SO3, XPO2F2 or XOTFB, wherein X is selected from Li, Na or K, and / or Based on 100% of the mass of the electrolyte, the concentration of the electrolyte salt relative to the electrolyte is 0.8-1.2 mol / L.

7. The electrolyte according to any one of claims 1 or 2, characterized in that The electrolyte further comprises a functional additive, wherein the content of the functional additive is 0.5% to 4.5% based on the mass of the electrolyte as 100%, and / or The electrolyte further includes functional additives, which include one or more of vinylene carbonate, 1,3-propane sultone, fluoroethylene carbonate, phthaleinsulfathiazole, vinyl sulfate, and difluorooxalate borate.

8. A battery, characterized in that: The invention comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the electrolyte comprises the electrolyte according to any one of claims 1 to 7. 9 . The battery according to claim 8 , which is an alkali metal battery.

10. An electrical device, characterized in that: Comprising a battery according to claim 8 or 9.

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