Application of oxadiazolone compounds, electrolyte and preparation method thereof, solid electrolyte membrane, lithium ion battery and electrical equipment

Abstract

The present invention relates to the field of lithium batteries, and discloses an application of an oxadiazolone compound in an electrolyte, an electrolyte and a preparation method thereof, a lithium ion battery, and an electrical device. The oxadiazolone compound has a structure shown in formula (1): #imgabs0# wherein R1 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C1 to C 10 Keto or ester group; R2 is selected from H or substituted or unsubstituted C1 to C 10 The electrolyte containing the oxadiazolone compound is applied to lithium batteries to improve the stability of the SEI film, ion conductivity and high-temperature performance of silicon-carbon negative electrode batteries.

Description

Technical Field

[0001] The present invention relates to the field of lithium batteries, and in particular to an application of an oxadiazolone compound, an electrolyte and a preparation method thereof, a solid electrolyte membrane, a lithium ion battery and electrical equipment. Background Art

[0002] As one of the main materials in lithium-ion batteries, the electrolyte plays a crucial role. One of its functions is to form a solid electrolyte interface (SEI) layer at the anode through an electrochemical reduction reaction. This layer protects the electrolyte while also transporting lithium ions. However, how to form an excellent SEI layer that is dense, stable, and elastic has always been a major bottleneck in the field of electrolyte additives, especially in silicon-carbon anode systems.

[0003] Silicon is a highly potential negative electrode material and is a rich geological resource on Earth, accounting for 26.4% of the total mass of the earth's crust. It has a very high specific capacity (about 4000mAh / g) and a very low lithium insertion potential (about 0.2VvsLi / Li + However, silicon experiences severe volume expansion (approximately 400%) during the lithium ion insertion and extraction process, which can lead to severe damage to the electrode structure and excessive growth of the SEI film, causing battery capacity degradation and greatly hindering the application of silicon materials.

[0004] At present, the use of silicon-carbon composite materials is one of the solutions, which can slow down the volume expansion problem to a certain extent, thereby slowing down the attenuation of battery capacity. At the same time, the addition of negative electrode conductive agents can also improve the conductivity of silicon materials.

[0005] The main solution to the problem of repeated rupture and growth of SEI film is to add suitable negative electrode film-forming additives to the electrolyte, so that it can preferentially form a stable SEI film on the surface of the silicon-carbon negative electrode, which can adapt to the volume expansion of the silicon-carbon negative electrode, thereby preventing the continuous reduction of the electrolyte. The most effective electrolyte additive at present is fluoroethylene carbonate (FEC). As a derivative compound of cyclic carbonate, it has a higher reduction potential and can be reduced at the negative electrode before the solvent, forming a relatively stable SEI film, which plays a protective role for the silicon-carbon negative electrode and the electrolyte.

[0006] However, due to the substitution of F atoms on the five-membered ring, FEC is prone to elimination reactions at high temperatures, producing hydrofluoric acid, which triggers the decomposition of lithium salts and solvents, causing changes in the electrolyte composition and even dissolving metal elements in the positive electrode, degrading battery performance. Therefore, although the addition of FEC to silicon negative electrode batteries improves the cycle performance at room temperature, it also greatly degrades the high-temperature performance.

[0007] Therefore, it is necessary to develop an electrolyte that can form a more stable SEI film and improve its ionic conductivity, thereby improving the high-temperature performance of silicon-carbon negative electrode batteries. Summary of the Invention

[0008] The purpose of the present invention is to overcome the problems of the prior art, such as the insufficient stability and poor ionic conductivity of the SEI film, and the poor high-temperature performance of the silicon-carbon negative electrode battery, and to provide an application of an oxadiazolone compound, an electrolyte and a preparation method thereof, a solid electrolyte membrane, a lithium-ion battery and electrical equipment.

[0009] In order to achieve the above object, the first aspect of the present invention provides an application of an oxadiazolone compound in an electrolyte, wherein the oxadiazolone compound has a structure shown in formula (1):

[0010]

[0011] wherein R1 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C1 to C 10 Keto or ester group; R2 is selected from H, substituted or unsubstituted C1 to C 10 alkyl.

[0012] A second aspect of the present invention provides an electrolyte, wherein the electrolyte comprises solvent A, solvent B, a lithium salt, an oxadiazolone compound and an optional additive F;

[0013] The oxadiazolone compound has a structure shown in formula (1):

[0014]

[0015] wherein R1 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C1 to C 10 Keto or ester group; R2 is selected from H or substituted or unsubstituted C1 to C 10 alkyl.

[0016] A third aspect of the present invention provides a method for preparing an electrolyte, the method comprising:

[0017] Mixing a lithium salt, an oxadiazolone compound, an optional additive F, and a solvent to obtain an electrolyte;

[0018] The oxadiazolone compound has a structure shown in formula (1):

[0019]

[0020] wherein R1 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C1 to C 10 Keto or ester group; R2 is selected from H, substituted or unsubstituted C1 to C 10 alkyl.

[0021] The fourth aspect of the present invention provides an electrolyte prepared by the preparation method described in the third aspect of the present invention.

[0022] A fifth aspect of the present invention provides a solid electrolyte membrane, comprising organic matter and inorganic matter; wherein the organic matter comprises: polymer, LiOR2, LiOCO2R2; the inorganic matter comprises LiF, Li2O, Li2CO3, LiOH;

[0023] Wherein, the polymer contains a structural unit as shown in formula (2) derived from an oxadiazolone compound,

[0024] wherein R1 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C1 to C 10 Keto or ester group; R2 is selected from H, substituted or unsubstituted C1 to C 10 alkyl.

[0025] A sixth aspect of the present invention provides a lithium battery, comprising the electrolyte described in the second and fourth aspects of the present invention, or the solid electrolyte membrane of the fifth aspect.

[0026] The seventh aspect of the present invention provides an electrical device, which includes the lithium-ion battery described in the fifth aspect of the present invention; wherein the electrical device includes transportation tools and digital products, preferably selected from pure electric vehicles, hybrid vehicles, electric bicycles, and laptop computers.

[0027] Through the above technical solution, the present invention can produce the following beneficial effects:

[0028] 1. Since the electrolyte provided by the present invention uses oxadiazolone compounds, cyclic voltammetry experiments have also proved that the oxadiazolone compounds used in the present invention can have a higher reduction potential than ethylene carbonate. The results are shown in the attached Figure 1 Therefore, the oxadiazolone compound contained in the electrolyte provided by the present invention can be reduced at the negative electrode before EC, thereby protecting the electrolyte.

[0029] 2. Due to their carbon-nitrogen double bonds, the double bonds of the oxadiazolone compounds of the present invention can capture electrons on the negative electrode surface during the initial battery formation cycle, forming an SEI film composed of polymer chain segments through electrochemical reduction polymerization. The polymer segments have good elasticity, allowing the SEI film to withstand volume changes of the silicon-carbon material without breaking, effectively preventing the continuous reduction of the electrolyte, significantly reducing the consumption of electrolyte and active lithium, and effectively improving the battery's capacity and cycle performance.

[0030] 3. Due to the introduction of heteroatoms (nitrogen) in the five-membered ring, when the prepared electrolyte of the oxadiazolone compound of the present invention is used to assemble a lithium battery and is charged, a polymerization reaction occurs to form a solid electrolyte membrane. The lone electron pairs of the three heteroatoms (nitrogen, nitrogen, and oxygen) in its chemical structure can be delocalized to the entire five-membered ring and conjugated to form a large π bond. Then, the Lewis acid transport mechanism can better help lithium ions to be transported in the SEI membrane, thereby improving the ionic conductivity of the SEI membrane.

[0031] 4. The oxadiazolone compounds of the present invention have been shown to have better high-temperature stability than FEC through high-temperature storage experiments, thereby improving the high-temperature performance of the battery.

[0032] 5. The oxadiazolone compounds of the present invention can be used in different electrolyte systems and have universal applicability.

[0033] The combined effects listed above enable the oxadiazolone compounds of the present invention to effectively improve the battery performance after being added to the electrolyte of silicon-carbon material batteries.

[0034] The additive of the present invention is aimed at the silicon negative electrode, which can be pure silicon, silicon oxide or silicon carbon composite material. The positive electrode is a ternary nickel-cobalt-manganese material, such as LiNi 0.33 Co 0.33 Mn 0.33 O2 (NCM111 type), LiNi 0.4 Co 0.2 Mn 0.4 O2 (NCM424 type), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523 type), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622 type), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811 type). BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1These are the cyclic voltammetry test results of Example 1 (3,5-dimethyl-1,3,4-oxadiazol-2(3H)-one, electrolyte L1) of the present invention and Comparative Example 1.

[0036] Figure 2 yes Figure 1 The middle voltage (abscissa) is the cyclic voltammetry test results in the range of 0.6-2.0V. DETAILED DESCRIPTION

[0037] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0038] As mentioned above, the first aspect of the present invention provides an application of an oxadiazolone compound in an electrolyte, wherein the oxadiazolone compound has a structure shown in formula (1):

[0039]

[0040] wherein R1 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C1 to C 10 Keto or ester group; R2 is selected from H or substituted or unsubstituted C1 to C 10 alkyl.

[0041] Preferably, R1 is selected from phenyl, methyl, ethoxycarbonyl or acetonyl; and R2 is selected from H or methyl.

[0042] Preferably, the oxadiazolone compound is selected from at least one of 3,5-dimethyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-3-phenyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-2-oxo-1,3,4-oxadiazole-3-carboxylic acid ethyl ester, 5-methyl-3-(2-oxopropyl)-2,3-dihydro-1,3,4-oxadiazol-2-one, 3-(3-methylphenyl)-1,3,4-oxadiazol-2(3H)-one, 3-phenyl-1,3,4-oxadiazol-2(3H)-one and 3-(2-oxopropyl)-1,3,4-oxadiazol-2(3H)-one.

[0043] The presence of hydrogen ions in the electrolyte provided by the present invention increases its acidity, leading to hydrolysis of the lithium salt and the generation of hydrogen gas. Therefore, active hydrogen is not suitable for the R1 additive. Furthermore, the electropolymerization reaction occurring at the battery's negative electrode requires electrons to attack the carbon-nitrogen double bond to form free radicals. Therefore, R2 should not be too long or too large to prevent excessive steric hindrance that would hinder the double bond from capturing electrons. Therefore, more preferably, the oxadiazolone compound is selected from at least one of 3,5-dimethyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-3-phenyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-2-oxo-1,3,4-oxadiazole-3-carboxylic acid ethyl ester, 5-methyl-3-(2-oxopropyl)-2,3-dihydro-1,3,4-oxadiazol-2-one and 3-(2-oxopropyl)-1,3,4-oxadiazol-2(3H)-one.

[0044] More specifically, in the present invention, the oxadiazolone compound is selected from at least one of the compounds represented by the following chemical formula:

[0045]

[0046] A second aspect of the present invention provides an electrolyte, wherein the electrolyte comprises solvent A, solvent B, a lithium salt, an oxadiazolone compound and an optional additive F;

[0047] The oxadiazolone compound has a structure shown in formula (1):

[0048]

[0049] wherein R1 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C1 to C 10 Keto or ester group; R2 is selected from H, substituted or unsubstituted C1 to C 10 alkyl.

[0050] Preferably, the oxadiazolone compound is selected from at least one of 3,5-dimethyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-3-phenyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-2-oxo-1,3,4-oxadiazole-3-carboxylic acid ethyl ester, 5-methyl-3-(2-oxopropyl)-2,3-dihydro-1,3,4-oxadiazol-2-one, 3-(3-methylphenyl)-1,3,4-oxadiazol-2(3H)-one, 3-phenyl-1,3,4-oxadiazol-2(3H)-one, 3-(2-oxopropyl)-1,3,4-oxadiazol-2(3H)-one and 3-methyl-5-phenyl-1,3,4-oxadiazol-2(3H)-one.

[0051] More preferably, the oxadiazolone compound is selected from at least one of 3,5-dimethyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-3-phenyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-2-oxo-1,3,4-oxadiazole-3-carboxylic acid ethyl ester, 5-methyl-3-(2-oxopropyl)-2,3-dihydro-1,3,4-oxadiazol-2-one and 3-(2-oxopropyl)-1,3,4-oxadiazol-2(3H)-one.

[0052] The oxadiazolone compounds are as described above and will not be described in detail herein.

[0053] Wherein, the lithium salt is selected from lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate or lithium perchlorate; preferably lithium hexafluorophosphate.

[0054] Preferably, the solvent A is selected from cyclic carbonates, preferably at least one selected from ethylene carbonate, propylene carbonate or 1,2-butene carbonate.

[0055] Preferably, the solvent B is selected from linear carbonates, preferably at least one selected from dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate or methylpropyl carbonate.

[0056] Preferably, the additive F is selected from at least one of vinylene carbonate, fluoroethylene carbonate, and difluoroethylene carbonate; more preferably, fluoroethylene carbonate.

[0057] Wherein, based on the total amount of the electrolyte, the mass concentration of the solvent A is 25-35%, and this mass concentration range can make the electrolyte have a good dielectric constant and viscosity; the mass concentration of the solvent B is 50-65%, and this mass concentration range can make the electrolyte have a good dielectric constant and viscosity; the mass concentration of the lithium salt is 6-15%, and this mass concentration range can make the electrolyte have good conductivity and viscosity; the mass concentration of the oxadiazolone compound is 0.1-10%, and this mass concentration range can make the electrolyte have a significant negative electrode film-forming effect and high battery first-cycle efficiency. The technical effect is preferably 0.5-3%; the mass concentration of the additive F is 0-5%, and this mass concentration range can make the electrolyte have a suitable battery impedance. Wherein, the mass ratio of the solvent A to the solvent B is 1:(1-3), and this mass ratio range can make the electrolyte system have a suitable dielectric constant; preferably 1:(2-2.5).

[0058] Wherein, the film forming potential of the electrolyte is 1.30-1.80V, preferably 1.35-1.55V.

[0059] A third aspect of the present invention provides a method for preparing an electrolyte, the method comprising:

[0060] Mixing a lithium salt, an oxadiazolone compound, an optional additive F, and a solvent to obtain an electrolyte;

[0061] The oxadiazolone compound has a structure shown in formula (1):

[0062]

[0063] wherein R1 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C1 to C 10 Keto or ester group; R2 is selected from H or substituted or unsubstituted C1 to C 10 alkyl.

[0064] In some embodiments of the present invention, preferably, the oxadiazolone compound is selected from at least one of 3,5-dimethyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-3-phenyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-2-oxo-1,3,4-oxadiazole-3-carboxylic acid ethyl ester, 5-methyl-3-(2-oxopropyl)-2,3-dihydro-1,3,4-oxadiazol-2-one, 3-(3-methylphenyl)-1,3,4-oxadiazol-2(3H)-one, 3-phenyl-1,3,4-oxadiazol-2(3H)-one and 3-(2-oxopropyl)-1,3,4-oxadiazol-2(3H)-one.

[0065] More preferably, it is at least one of 3,5-dimethyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-3-phenyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-2-oxo-1,3,4-oxadiazole-3-carboxylic acid ethyl ester, 5-methyl-3-(2-oxopropyl)-2,3-dihydro-1,3,4-oxadiazol-2-one and 3-(2-oxopropyl)-1,3,4-oxadiazol-2(3H)-one.

[0066] In some embodiments of the present invention, preferably, the lithium salt is selected from lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate or lithium perchlorate; more preferably, lithium hexafluorophosphate.

[0067] In some embodiments of the present invention, preferably, the additive F is selected from at least one of vinylene carbonate, fluoroethylene carbonate or difluoroethylene carbonate; more preferably, fluoroethylene carbonate.

[0068] In some embodiments of the present invention, preferably, the solvent is a mixed solvent made of solvent A and solvent B.

[0069] In some embodiments of the present invention, preferably, the mass ratio of the solvent A to the solvent B is 1:(1-3), more preferably 1:(2-2.5).

[0070] In some embodiments of the present invention, preferably, the solvent A is selected from cyclic carbonates, preferably at least one selected from ethylene carbonate, propylene carbonate and 1,2-butene carbonate.

[0071] In some embodiments of the present invention, preferably, the solvent B is selected from linear carbonates, preferably at least one selected from dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and methyl propyl carbonate.

[0072] In some embodiments of the present invention, preferably, in parts by weight, the solvent A is 25-35 parts by weight; the solvent B is 50-65 parts by weight; the oxadiazolone compound is 0.1-10 parts by weight, preferably 0.5-3 parts by weight; the lithium salt is 6-15 parts by weight, and the additive F is 0-5 parts by weight.

[0073] The fourth aspect of the present invention provides an electrolyte prepared by the preparation method described in the third aspect of the present invention.

[0074] A fifth aspect of the present invention provides a solid electrolyte membrane, wherein the organic matter includes: polymer, LiOR2, LiOCO2R2; the inorganic matter includes LiF, Li2O, Li2CO3, LiOH;

[0075] Wherein, the polymer contains a structural unit as shown in formula (2) derived from an oxadiazolone compound,

[0076] wherein R1 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C1 to C 10 Keto or ester group; R2 is selected from H, substituted or unsubstituted C1 to C 10 alkyl.

[0077] In some embodiments of the present invention, preferably, the content of the polymer is 10-50 wt % based on the total amount of the solid electrolyte membrane.

[0078] The polymer contained in the solid electrolyte membrane is formed by a polymerization reaction of the oxadiazolone compound contained in the electrolyte of the present invention in a lithium battery under the conditions of the film-forming potential. Specifically, it is formed by an electrochemical reduction polymerization reaction of the C=N double bond contained in the oxadiazolone compound. Furthermore, the presence of the formed polymer can be confirmed by XPS or TOF-SIMS interface characterization techniques. This polymer can form a SEI film on the negative electrode surface of the lithium battery.

[0079] A sixth aspect of the present invention provides a lithium battery, comprising the electrolyte described in the second and fourth aspects of the present invention, or the solid electrolyte membrane of the fifth aspect of the present invention.

[0080] The seventh aspect of the present invention provides an electrical device, which includes the lithium-ion battery described in the sixth aspect of the present invention; wherein the electrical device includes transportation tools and digital products, preferably selected from pure electric vehicles, hybrid vehicles, electric bicycles, and laptop computers.

[0081] The present invention will be described in detail below through examples. In the following examples, ethylene carbonate and ethyl methyl carbonate are commercially available products from Xinzhoubang Company; lithium hexafluorophosphate is commercially available from Duofuduo Company; and oxadiazolone is commercially available from Honest Joy Holdings Limited.

[0082] Example 1

[0083] (1) Preparation of electrolyte

[0084] 30g of ethylene carbonate (EC) and 70g of ethyl methyl carbonate (EMC) were mixed to form a mixed solvent. 14.4g of lithium hexafluorophosphate was added to the mixed solvent. Then, 1.16g (1% by mass) of 3,5-dimethyl-1,3,4-oxadiazol-2(3H)-one (as shown in Formula 3) was added. This electrolyte was designated L1.

[0085]

[0086] (2) Preparation of batteries

[0087] The carbon-coated silicon material, conductive agent super-p, thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) were mixed evenly in a mass ratio of 100:2:2:3. The resulting paste was evenly coated on a copper foil serving as the negative electrode current collector and dried in a vacuum oven at 60°C for 24 hours to obtain a negative electrode sheet.

[0088] The positive electrode uses LiNi 0.33 Co 0.33 Mn 0.33O2 (i.e., NCM111 type), NCM1111, carbon nanotubes (CNTs), and polyvinylidene fluoride (PVDF) were uniformly mixed in a mass ratio of 100:2:2, and the resulting paste was evenly coated on aluminum foil as the positive electrode current collector, and dried in a vacuum oven at 60°C for 24 hours to obtain a positive electrode sheet.

[0089] Preparation of soft-pack batteries: A cell, model SL523450, with a silicon anode soft-pack lithium battery, was prepared by winding. In an argon glove box with water and oxygen concentrations below 5 ppm, 3 g of electrolyte L1 was injected into the air-filled soft-pack battery to prepare cell P1 for cycling testing.

[0090] Formation process: The soft-pack battery is first charged to 1.5V at 45mA (0.05C) and held at 1.5V for 10 hours to allow the electrolyte to fully penetrate the battery electrodes. After sufficient aging, the battery is first charged at a lower current of 9mA (C / 100) for 15 hours to form a stable and complete SEI film. It is then charged to 4.2V at 45mA (0.05C) and discharged to 3V. The formation of the SEI film is confirmed using XPS or TOF-SIMS interface characterization techniques.

[0091] Preparation of button cell: The coated silicon-carbon negative electrode sheet was used on a lithium sheet, model CR2016, with an injection volume of about 100 μg to obtain battery C1 for electrolyte reduction potential test.

[0092] Example 2

[0093] An electrolyte was prepared in the same manner as in Example 1, except that the additive was 1.16 g (1% by mass) of 5-methyl-3-phenyl-1,3,4-oxadiazol-2(3H)-one (as shown in Formula 4), to obtain electrolyte L2.

[0094] The battery preparation and formation process were the same as in Example 1, and soft-pack battery P2 and button battery C2 were prepared.

[0095]

[0096] Example 3

[0097] An electrolyte was prepared in the same manner as in Example 1, except that 1.16 g (1% by mass) of ethyl 5-methyl-2-oxo-1,3,4-oxadiazole-3-carboxylate (as shown in Formula 5) was used as the additive to obtain electrolyte L3.

[0098] The battery preparation and formation process were the same as in Example 1, and soft-pack battery P3 and button battery C3 were prepared.

[0099]

[0100] Example 4

[0101] An electrolyte was prepared in the same manner as in Example 1, except that the additive was 1.16 g (1% by mass) of 5-methyl-3-(2-oxypropyl)-2,3-dihydro-1,3,4-oxadiazol-2-one (as shown in Formula 6), to obtain electrolyte L4.

[0102] The battery preparation and formation process were the same as in Example 1, and soft-pack battery P4 and button battery C4 were prepared.

[0103]

[0104] Example 5

[0105] An electrolyte was prepared in the same manner as in Example 1, except that the additive was 1.16 g (1% by mass) of 3-(2-oxypropyl)-1,3,4-oxadiazol-2(3H)-one (as shown in Formula 7), to obtain electrolyte L5.

[0106] The battery preparation and formation process were the same as in Example 1, and soft-pack battery P5 and button battery C5 were prepared.

[0107]

[0108] Comparative Example 1

[0109] An electrolyte was prepared in the same manner as in Example 1, except that no oxadiazolone compound was present, to obtain electrolyte R1.

[0110] The battery preparation and formation process were the same as in Example 1, and a soft-pack battery RP1 and a button battery RC1 were prepared.

[0111] Comparative Example 2

[0112] An electrolyte was prepared in the same manner as in Example 1, except that no oxadiazolone compound was present and the additive F was 1.16 g (1% by mass) of fluoroethylene carbonate, to obtain electrolyte R2 for use in high-temperature storage experiments.

[0113] Comparative Example 3

[0114] An electrolyte was prepared in the same manner as in Example 1, except that the oxadiazolone compound was 1.16 g (1% by mass) of 5-methyl-1,3,4-oxadiazolone (as shown in Formula 8), to obtain electrolyte R3.

[0115] The battery preparation and formation process were the same as in Example 1 to prepare a soft-pack battery RP3.

[0116]

[0117] Comparative Example 4

[0118] An electrolyte was prepared in the same manner as in Example 1, except that the oxadiazolone compound was 1.16 g (1% by mass) of 3-methyl-5-phenyl-1,3,4-oxadiazol-2(3H)-one (as shown in Formula 9), to obtain electrolyte R4.

[0119] The battery preparation and formation process were the same as in Example 1 to prepare battery RP4.

[0120]

[0121] Additive reduction potential test

[0122] The button cells in Examples 1-5 and Comparative Example 1 were subjected to cyclic voltammetry tests with a scan rate of 0.2 mV / s and a scan range of 0.005-2.5 V. The test equipment was a Chenhua model CHI600C electrochemical workstation. A higher film-forming potential enables the electrolyte to be reduced to form a film at the negative electrode in advance, thereby protecting the solvent in the electrolyte. The film-forming potential of the electrolyte in the prior art is about 0.75-1.15 V, which is significantly lower than the electrolyte described in the present invention. The film-forming potential test results are shown in Table 1, and the cyclic voltammetry test results of Example 1 (3,5-dimethyl-1,3,4-oxadiazol-2(3H)-one, electrolyte L1) and Comparative Example 1 are shown in Table 1. Figure 1 .

[0123] Table 1

[0124] Electrolyte number <![CDATA[Film-forming potential (vs. Li + / Li, V)]]> L1 1.51 L2 1.38 L3 1.61 L4 1.55 L5 1.52 Comparative Example 1R1 0.80

[0125] From Table 1 and Figure 1 It can be seen that the reduction potential of the oxadiazolone compounds of the present invention is 1.35-1.60V (~Li / Li + ), which is higher than the reduction potential of the comparative example (0.80 V, carbonate solvent), indicating that this type of oxadiazolone compound will be reduced to form a film preferentially over the electrolyte solvent during the battery cycle.

[0126] Electrolyte high temperature storage test

[0127] Electrolytes L1-5 from the examples and electrolyte R2 from comparative example 2 were sealed in square aluminum-plastic bags with silicon-carbon anode plates and stored in a 60°C thermostat for 7 days. The volume expansion ratios were calculated using the volume exclusion method. A smaller volume expansion ratio indicates less gas generation during storage, indicating that the solid electrolyte interphase (SEI) film formed by the oxadiazolone compound at the anode effectively prevents side reactions between the electrolyte and the anode.

[0128] The volume expansion rate of the square aluminum-plastic bag (%) = (the volume of the square aluminum-plastic bag after high-temperature storage / the volume of the square aluminum-plastic bag before storage) × 100%. The results are shown in Table 2.

[0129] Table 2

[0130] Electrolyte number Volume expansion rate (%) L1 23 L2 34 L3 25 L4 28 L5 28 R2 160

[0131] As can be seen from Table 2, the electrolyte containing the additive of the present invention has a greatly reduced gas production during storage under high temperature conditions, indicating that the high-temperature performance of the oxadiazolone compound of the present invention is far superior to that of fluoroethylene carbonate.

[0132] Silicon anode battery cycle test and SEI film elasticity test on the anode surface after cycling

[0133] Soft-pack batteries P1-P5 of the examples and RP1, RP3, and RP4 of the comparative examples (10 batteries for each condition, the results are averaged) were cycled 400 times at 900 mA (1C) between 3.0 V and 4.2 V. The test instrument can be a domestically produced Blue Electric CT2001C test cabinet, and the capacity retention rate was calculated.

[0134] Capacity retention (%) = (discharge capacity at the 150th cycle ÷ initial discharge capacity at the first cycle) × 100%. The results are shown in Table 3.

[0135] After the cycle is completed, the batteries in the embodiment and the comparative example are disassembled and the silicon negative electrode 1×1 cm 2 The Young's modulus of the small piece was measured by atomic force microscopy (AFM, Bruker Dimension Icon) probe method. The Young's modulus is used to characterize the elasticity of the SEI film on the negative electrode surface. A smaller Young's modulus indicates a better SEI film elasticity. Young's modulus calculation method F = (2 / π)(E / (1-v 2 ))δ 2 tan(σ), where F is the force applied to the probe, E is the Young's modulus, v is the Poisson coefficient (here 0.5), δ is the SEI film thickness, and σ is half the cone apex angle. This method has been reported in the literature (ACS Appl. Mater. Interfaces 2015, 7, 23554-23563). The results are shown in Table 3.

[0136] Table 3

[0137] Battery number Capacity retention rate (%) SEI film Young's modulus (GPa) P1 91 9.15 P2 82 14.4 P3 88 9.84 P4 85 10.1 P5 86 9.97 RP1 72 20.3 RP3 68 19.5 RP4 75 17.8

[0138] It can be seen from the cycle results in Table 3 that the battery cycle performance to which the film-forming additive F of the present invention is added is better than that of Comparative Example 1 and Comparative Examples 3 and 4 of similar structures. This shows that the addition of additive F can form a SEI film containing polymer chain segments on the surface of the silicon-carbon negative electrode, thereby adapting to the volume change of the silicon-carbon negative electrode during the cycle without breaking, thereby improving the cycle performance of the battery. The smaller Young's modulus of Examples 1-5 also proves this. Among them, the Young's modulus of Example 2 is relatively large, which may be due to the substitution of the phenyl group on the five-membered ring, which makes its steric hindrance larger, and has a certain adverse effect on the additive forming the SEI film, but it is still significantly lower than the Young's modulus of Comparative Examples 1-3, which reflects the superiority of the oxadiazolone compounds described in the present invention in terms of Young's modulus. The cycle results of Comparative Example 3 show that the presence of active hydrogen will induce the decomposition of lithium salts, greatly reduce the capacity retention rate of the battery, and is not conducive to battery cycling. The Young's modulus of Comparative Example 4 shows that the presence of large-volume substituent groups on the carbon-nitrogen double bond will greatly hinder the double bond from polymerizing into a film on the negative electrode surface, thereby affecting the cycle performance of the battery.

[0139] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. An application of an oxadiazolone compound in an electrolyte, wherein: The oxadiazolone compound has a structure shown in formula (1): Formula (1), wherein R1 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C1 to C 10 Keto or ester group; R2 is selected from H, substituted or unsubstituted C1 to C 10 alkyl.

2. The use according to claim 1, wherein The oxadiazolone compound is selected from at least one of 3,5-dimethyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-3-phenyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-2-oxo-1,3,4-oxadiazole-3-carboxylic acid ethyl ester, 5-methyl-3-(2-oxopropyl)-2,3-dihydro-1,3,4-oxadiazol-2-one, 3-(3-methylphenyl)-1,3,4-oxadiazol-2(3H)-one, 3-phenyl-1,3,4-oxadiazol-2(3H)-one and 3-(2-oxopropyl)-1,3,4-oxadiazol-2(3H)-one.

3. The use according to claim 1, wherein: The oxadiazolone compound is selected from at least one of 3,5-dimethyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-3-phenyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-2-oxo-1,3,4-oxadiazole-3-carboxylic acid ethyl ester, 5-methyl-3-(2-oxopropyl)-2,3-dihydro-1,3,4-oxadiazol-2-one and 3-(2-oxopropyl)-1,3,4-oxadiazol-2(3H)-one.

4. An electrolyte, wherein The electrolyte comprises solvent A, solvent B, lithium salt, and oxadiazolone compound; The oxadiazolone compound has a structure shown in formula (1): Formula (1), wherein R1 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C1 to C 10 Keto or ester group; R2 is selected from H, substituted or unsubstituted C1 to C 10 alkyl; The solvent A is a cyclic carbonate; the solvent B is a linear carbonate.

5. The electrolyte according to claim 4, wherein The oxadiazolone compound is selected from at least one of 3,5-dimethyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-3-phenyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-2-oxo-1,3,4-oxadiazole-3-carboxylic acid ethyl ester, 5-methyl-3-(2-oxopropyl)-2,3-dihydro-1,3,4-oxadiazol-2-one, 3-(3-methylphenyl)-1,3,4-oxadiazol-2(3H)-one, 3-phenyl-1,3,4-oxadiazol-2(3H)-one and 3-(2-oxopropyl)-1,3,4-oxadiazol-2(3H)-one.

6. The electrolyte according to claim 5, wherein The oxadiazolone compound is selected from at least one of 3,5-dimethyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-3-phenyl-1,3,4-oxadiazol-2(3H)-one, 5-methyl-2-oxo-1,3,4-oxadiazole-3-carboxylic acid ethyl ester, 5-methyl-3-(2-oxopropyl)-2,3-dihydro-1,3,4-oxadiazol-2-one and 3-(2-oxopropyl)-1,3,4-oxadiazol-2(3H)-one.

7. The electrolyte according to any one of claims 4 to 6, wherein The lithium salt is selected from lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate or lithium perchlorate; And / or, the solvent A is selected from at least one of ethylene carbonate, propylene carbonate, and 1,2-butene carbonate; And / or, the solvent B is at least one selected from dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate.

8. The electrolyte according to claim 7, wherein The lithium salt is lithium hexafluorophosphate.

9. The electrolyte according to any one of claims 4 to 6, wherein The electrolyte further includes an additive F; the additive F is selected from at least one of vinylene carbonate, fluoroethylene carbonate, and difluoroethylene carbonate.

10. The electrolyte according to claim 9, wherein The additive F is fluoroethylene carbonate.

11. The electrolyte according to claim 10, wherein Based on the total amount of the electrolyte, the mass concentration of the additive F is 0-5%.

12. The electrolyte according to any one of claims 4 to 6, wherein Based on the total amount of the electrolyte, the mass concentration of the solvent A is 25-35%; the mass concentration of the solvent B is 50-65%; the mass concentration of the lithium salt is 6-15%; and the mass concentration of the oxadiazolone compound is 0.1-10%.

13. The electrolyte according to claim 12, wherein Based on the total amount of the electrolyte, the mass concentration of the oxadiazolone compound is 0.5-3%.

14. The electrolyte according to any one of claims 4 to 6, wherein The mass ratio of the solvent A to the solvent B is 1:(1-3).

15. The electrolyte according to claim 14, wherein The mass ratio of the solvent A to the solvent B is 1:(2-2.5).

16. The electrolyte according to any one of claims 4 to 6, wherein The film forming potential of the electrolyte is 1.30-1.80V.

17. The electrolyte according to claim 16, wherein The film forming potential of the electrolyte is 1.35-1.55V.

18. A method for preparing an electrolyte, the method comprising: mixing a lithium salt, an oxadiazolone compound, and a solvent to obtain an electrolyte; The oxadiazolone compound has a structure shown in formula (1): Formula (1), wherein R1 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C1 to C 10 Keto or ester group; R2 is selected from H, substituted or unsubstituted C1 to C 10 alkyl.

19. The preparation method according to claim 18, wherein The method comprises: mixing the lithium salt, the oxadiazolone compound, the additive F and the solvent to obtain an electrolyte.

20. The preparation method according to claim 19, wherein The additive F is selected from at least one of vinylene carbonate, fluoroethylene carbonate, and difluoroethylene carbonate.

21. A solid electrolyte membrane, wherein: Including organic matter and inorganic matter; wherein the organic matter includes: polymer, LiOR2, LiOCO2R2; the inorganic matter includes LiF, Li2O, Li2CO3, LiOH; The polymer contains a structural unit as shown in formula (2) derived from an oxadiazolone compound. Formula (2); wherein R1 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C1 to C 10 Keto or ester group; R2 is selected from H, substituted or unsubstituted C1 to C 10 alkyl.

22. The solid electrolyte membrane according to claim 21, wherein In the solid electrolyte membrane, the content of the polymer is 10-50 wt%.

23. A lithium ion battery, wherein: The invention comprises the electrolyte according to any one of claims 4 to 17, or the solid electrolyte membrane according to claim 21 or 22.

24. An electrical device, wherein: Including the lithium ion battery according to claim 23.

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