Electrolyte and lithium ion battery

Abstract

The application relates to the technical field of lithium ion batteries, in particular to an electrolyte and a lithium ion battery, wherein the lithium ion battery electrolyte contains a compound with a structure shown in formula I, and the compound with the structure shown in formula I is a phenyl isothiocyanate compound. The phenyl isothiocyanate compound in the electrolyte can improve the structural stability of an electrode / electrolyte interface, and can improve the high-temperature storage gas production performance of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to an electrolyte and a lithium ion battery. BACKGROUND

[0002] In order to solve the range anxiety and charging anxiety of electric vehicle consumers, the follow-up development of lithium ion batteries needs to be oriented to high energy density, high power, high safety and long service life. The ternary layered metal oxide positive electrode material and the silicon-carbon negative electrode material have attracted widespread attention due to their high theoretical specific capacity, but still face many challenges in actual use. For example, lithium ion batteries have the defects of poor structural stability of the electrode / electrolyte interface and easy occurrence of side reactions, which leads to serious gas production during high-temperature storage of the battery.

[0003] How to improve the structural stability of the electrode / electrolyte interface and inhibit the occurrence of side reactions to achieve a safe and reliable battery is a problem that researchers in the field need to solve urgently. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to overcome the defects of poor structural stability of the electrode / electrolyte interface and easy occurrence of side reactions of the lithium ion battery in the prior art, which leads to serious gas production during high-temperature storage of the battery, so as to provide an electrolyte and a lithium ion battery.

[0005] To this end, the present application provides an electrolyte, which comprises an organic solvent, a lithium salt and a compound having the structure shown in Formula I:

[0006]

[0007] wherein R1-R5 are independently selected from a hydrogen atom, a halogen, a cyano group, an isothiocyanate group, a substituted or unsubstituted C1-C5 alkyl group, a substituted or unsubstituted C1-C5 alkoxy group, a substituted or unsubstituted C1-C3 alkylthioether group, a substituted or unsubstituted C6-C10 aryloxy group, or a substituted or unsubstituted C1-C5 ester group, and R1-R5 are not hydrogen at the same time. 10 10 10

[0008] wherein when substituted, the substituent is selected from at least one of an alkyl group, an alkoxy group, an alkylthioether group, a halogen, an isothiocyanate group.

[0009] The term "1-3 hydrogen atoms are substituted by at least one selected from a halogen, an isothiocyanate group" means that 1-3 hydrogen atoms can be substituted by a halogen only, or substituted by an isothiocyanate group only, or substituted by a halogen and an isothiocyanate group at the same time.

[0010] ​​​Furthermore, R1-R5 are independently selected from hydrogen atoms, fluorine atoms, cyano groups, isothiocyanate groups, C1-C2 groups which are unsubstituted or substituted with 1-3 fluorine atoms or substituted with phenyl isothiocyanate. 10 Alkyl, unsubstituted C1–C 10 The present invention further comprises an alkoxy group, a C1-C3 alkylthioether group which is unsubstituted or substituted by 1-3 fluorine atoms, a phenoxy group substituted by 1-2 isothiocyanate groups, or an unsubstituted C1-C5 ester group, and R1-R5 are not hydrogen at the same time.

[0011] Further, R1-R5 are independently selected from hydrogen atom, fluorine atom, cyano group, isothiocyanate group, methyl group, ethyl group, n-decyl group, -CF3, -OCH3, -OCH2CH3, -SCH3, -SCF3, -COOCH3, or

[0012] Preferably, the compound having the structure shown in Formula I is selected from at least one of the compounds having the structures shown below:

[0013]

[0014]

[0015] Furthermore, the mass of the compound having the structure represented by Formula I accounts for 0.1%-6.0%, preferably 0.2-1.0%, of the total mass of the electrolyte.

[0016] Furthermore, the organic solvent includes chain ester and cyclic ester, the mass of chain ester accounts for 30-80% of the total mass of the electrolyte; the mass of cyclic ester accounts for 15%-50% of the total mass of the electrolyte, and the mass ratio of chain ester to cyclic ester is (5-9):(2-4).

[0017] Furthermore, the chain ester includes one or more of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methylpropyl carbonate (MPC), diphenyl carbonate (DPhC), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), and ethyl butyrate (EB); the cyclic ester includes one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC), and γ-butyrolactone (γ-GBL).

[0018] Further, the lithium salt includes lithium hexafluorophosphate (LiPF6) and a second lithium salt; the second lithium salt includes one or more of lithium tetrafluoroborate (LiBF4), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorodioxalate phosphate (LiDFOP), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).

[0019] Further, the mass of LiPF6 accounts for 12-15% of the total mass of the electrolyte, and the mass of the second lithium salt accounts for 0-10% of the total mass of the electrolyte; LiPF6 accounts for 80-100% of the total mass of LiPF6 and the second lithium salt, and the second lithium salt accounts for 0-15% of the total mass of LiPF6 and the second lithium salt.

[0020] The present application also provides a preparation method of the electrolyte described above, including the following steps:

[0021] The lithium salt is mixed in the organic solvent, and the compound with the structure shown in Formula I is mixed in the mixed solution to prepare the electrolyte; further, the lithium salt and the organic solvent are mixed under the condition that the temperature is increased by no more than 2℃.

[0022] Since the lithium salt will release heat when added to cause the temperature of the electrolyte to increase, the lithium salt will be decomposed to a certain extent by heat, and therefore, the mixing of the lithium salt and the solvent needs to be controlled at a lower temperature.

[0023] In another aspect of the present application, a lithium ion battery using the electrolyte described above is provided.

[0024] Further, the lithium ion battery further includes a positive electrode active material, a negative electrode active material, and the electrolyte described above.

[0025] Further, the chemical formula of the positive electrode active material includes LiaNi x Co y Mn z O2, wherein 0.9≤a≤1.1, 0.6≤x≤0.8, 0.1≤y≤0.2, 0.1≤z≤0.2, and x+y+z=1.

[0026] Further, the negative electrode active material includes one or more of silicon, silicon-carbon, silicon-oxygen, and silicon-metal compounds.

[0027] The technical solution of the present application has the following advantages:

[0028] 1. The electrolyte provided by the present invention comprises an organic solvent, a lithium salt and a compound having a structure shown in Formula I. The compound having a structure shown in Formula I is a phenyl isothiocyanate compound. Compared with the case where R1-R5 are all hydrogen, the hydrogen atoms in the phenyl isothiocyanate compound are replaced by halogen, cyano, isothiocyanate, substituted or unsubstituted C1-C 10 Alkyl, substituted or unsubstituted C1–C 10 Alkoxy, substituted or unsubstituted C1-C3 alkylthioether, substituted or unsubstituted C6-C 10 The stability of the passivation layer can be improved by replacing the aryloxy group or the substituted or unsubstituted C1-C5 ester group.

[0029] The electrolyte containing the compound of formula I forms a thin and uniform passivation film on the positive and negative electrodes, and the decomposition products (Li2SO3, Li2S and ROSO2Li) are stable, which can effectively inhibit the continuous decomposition of the electrolyte solvent. At the same time, the electrode / electrolyte interface impedance formed is low, which is beneficial to Li + conduction; secondly, the compound of the structure shown in Formula I can react with trace water in the electrolyte to avoid the generation of HF and corrosion of the positive and negative electrode interfaces, thereby inhibiting the dissolution of transition metal ions and irreversible phase changes in the positive electrode and the particle breakage of the silicon-carbon negative electrode to achieve stable battery circulation; thirdly, under the synergistic effect of stabilizing the interface and absorbing water, the side reactions of the electrolyte solvent at the interface are effectively suppressed, thereby improving the gas production risk of the battery and reducing the high-temperature volume expansion rate.

[0030] Among them, when R1-R5 is selected from halogen (preferably fluorine atom), or selected from alkyl, alkoxy, alkyl thioether, aryloxy, and ester groups containing halogen (preferably fluorine atom), the interfacial energy in the formed passivation layer can be further improved; and the alkoxy, ester, and cyano groups can form long-chain organic polymers to increase the mechanical properties of the passivation layer; the thioether group can increase the content of sulfur-containing compounds in the passivation layer, thereby better improving the stability of the passivation layer.

[0031] 2. The electrolyte provided by the present invention, the mass of the compound of the structure shown in formula I accounts for 0.1%-6.0% (preferably 0.2-1.0%) of the total mass of the electrolyte. If the content of the compound of the structure shown in formula I in the electrolyte is insufficient, it may not be able to form a strong interface passivation layer and effectively absorb trace water in the electrolyte, affecting its effect. If there is too much electrolyte, the passivation layer may be too thick, thereby causing Li + The diffusion resistance is too large and the polarization is increased. By controlling the mass of the compound of the structure shown in formula I to 0.1%-6.0% (preferably 0.2-1.0%) of the total mass of the electrolyte, the Li+ can be reduced while ensuring the stability of the interface passivation layer. + Diffusion resistance can improve the cycle performance of the battery and reduce gas production during high-temperature storage.

[0032] 3. The electrolyte provided by the present invention comprises a lithium salt comprising LiPF6 and one or more of the following other lithium salts: LiBF4, LiBOB, LiDFOB, LiDFOP, LiFSI, and LiTFSI. LiPF6 has a moderate ion transference number, a moderate dissociation constant, good oxidation resistance, and excellent aluminum foil passivation ability in common organic solvents. It is also compatible with a variety of positive and negative electrode materials and is the most important lithium salt in lithium-ion batteries.

[0033] By controlling the mass of LiPF6 to 12-15% of the total mass of the electrolyte, the conductivity of the electrolyte can be improved and a suitable viscosity can be obtained. The other lithium salts can act as auxiliary lithium salts to further improve the stability of the electrolyte and the lithium ion transference number.

[0034] 4. The method for preparing the electrolyte provided by the present invention is simple and reliable. By controlling the mixing of the lithium salt and the organic solvent under the condition that the temperature rise does not exceed 2°C, the situation in which the electrolyte temperature rises due to the heat release of the lithium salt and causes the lithium salt to decompose due to heat can be improved. DETAILED DESCRIPTION

[0035] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0036] The present invention relates to the technical field of lithium-ion batteries, and in particular to an electrolyte and a lithium-ion battery. The electrolyte comprises an organic solvent, a lithium salt and a compound having a structure shown in Formula I. The present application has found that the electrolyte comprising the compound having a structure shown in Formula I can form a thin and uniform passivation film at the positive and negative electrodes, and the decomposition products (Li2SO3, Li2S and ROSO2Li) are stable, which can effectively inhibit the continuous decomposition of the electrolyte solvent. At the same time, the formed electrode / electrolyte interface impedance is low, which is beneficial to Li + conduction; secondly, the compound of the structure shown in Formula I can react with trace water in the electrolyte to avoid the generation of HF and corrosion of the positive and negative electrode interfaces, thereby inhibiting the dissolution of transition metal ions and irreversible phase changes in the positive electrode and the particle breakage of the silicon-carbon negative electrode to achieve stable battery circulation; thirdly, under the synergistic effect of stabilizing the interface and absorbing water, the side reactions of the electrolyte solvent at the interface are effectively suppressed, thereby improving the gas production risk of the battery and reducing the high-temperature volume expansion rate.

[0037] In some embodiments of the present invention, the compound having the structure shown in Formula I in the lithium ion electrolyte of the present invention is

[0038] wherein, wherein, R1-R5 are independently selected from a hydrogen atom, a halogen, a cyano group, an isothiocyanate group, a substituted or unsubstituted C1-C5 alkyl group, a substituted or unsubstituted C1-C3 alkoxy group, a substituted or unsubstituted C1-C3 alkyl sulfide group, a substituted or unsubstituted C6-C10 aryloxy group, or a substituted or unsubstituted C1-C5 ester group, and R1-R5 are not simultaneously a hydrogen atom; 10 10 10

[0039] wherein, when substituted, the substituent is selected from at least one of an alkyl group, an alkoxy group, an alkyl sulfide group, a halogen, an isothiocyanate group.

[0040] The term "1-3 hydrogen atoms are substituted by at least one selected from a halogen, an isothiocyanate group" means that 1-3 hydrogen atoms can be substituted by a halogen only, or by an isothiocyanate group only, or by both a halogen and an isothiocyanate group.

[0041] In some embodiments of the present application, R1-R5 are independently selected from a hydrogen atom, a fluorine atom, a cyano group, an isothiocyanate group, a C1-C5 alkyl group which is unsubstituted or substituted by 1-3 fluorine atoms or substituted by a phenyl isothiocyanate, a C1-C3 alkoxy group which is unsubstituted, a C1-C3 alkyl sulfide group which is unsubstituted or substituted by 1-3 fluorine atoms, a C6-C10 aryloxy group which is unsubstituted or substituted by 1-2 isothiocyanate groups, or a C1-C5 ester group which is unsubstituted, and R1-R5 are not simultaneously a hydrogen atom. 10 10

[0042] In some embodiments of the present application, R1-R5 are independently selected from a hydrogen atom, a fluorine atom, a cyano group, an isothiocyanate group, a methyl group, an ethyl group, a n-decyl group, -CF3, -OCH3, -OCH2CH3, -SCH3, -SCF3, -COOCH3,

[0043] In some embodiments of the present application, preferably, the compound having the structure of Formula I is selected from at least one of the compounds having the structures as shown below:

[0044]

[0045]

[0046] ​​​​​​In some embodiments of the present application, the compound having the structure of Formula I accounts for 0.1%-6.0% of the total mass of the electrolyte, preferably 0.2%-1.0%. If the content of the compound having the structure of Formula I is insufficient, it can not form a solid interface passivation layer and effectively absorb trace water in the electrolyte, affecting its effect. If the content of the compound having the structure of Formula I is too high, it can cause the passivation layer to be too thick, resulting in excessive diffusion resistance and increased polarization. +

[0047] In some embodiments of the present application, the organic solvent includes a chain ester and a cyclic ester.

[0048] Optionally, the chain ester includes one or more of DMC, EMC, DEC, MPC, DPhC, EA, ethyl PA, MP, EP, PP, MB, and EB.

[0049] When selecting the organic solvent, it is necessary to consider whether the selected organic solvent meets the requirements of high dielectric constant, low viscosity, low melting point, high boiling point, low cost, etc. The chain ester has a lower viscosity and good electrochemical stability, which can improve the low-temperature performance of the electrolyte. Although the chain ester used as the organic solvent of the lithium ion electrolyte has the above advantages, the performance of a single organic solvent cannot meet the market needs, and therefore it needs to be mixed with other organic solvents. The cyclic ester has a high dielectric constant and high ionic conductivity, and can form a stable SEI film on the negative electrode surface, but its viscosity is relatively large. Therefore, mixing the chain ester and the cyclic ester to be used as the organic solvent of the lithium ion battery electrolyte can make the chain ester and the cyclic ester fully play a synergistic effect and improve the performance of the electrolyte together.

[0050] Optionally, the cyclic ester in the organic solvent includes one or more of carbon EC, PC, BC, FEC, and γ-GBL.

[0051] Specifically, in some embodiments of the present application, the chain ester is selected from EC, and the cyclic ester is selected from DEC or DMC or a combination of DEC and DMC.

[0052] In some embodiments of the present application, the mass of the chain ester accounts for 30-80% of the total mass of the electrolyte, and the mass of the cyclic ester accounts for 15%-50% of the total mass of the electrolyte, and the mass ratio of the chain ester to the cyclic ester is (5-9):(2-4).

[0053] Preferably, the mass ratio of the chain ester to the cyclic ester can be (5-7):(2-3), (7-9):(3-4), etc. Reasonably controlling the mass ratio of the chain ester to the cyclic ester can make the organic solvent have the advantages of relatively optimal dielectric constant and viscosity, relatively low melting point, and relatively high boiling point, etc.

[0054] ​In some embodiments of the present application, the lithium salt comprises LiPF6 and a second lithium salt; the second lithium salt comprises one or more of LiBF4, LiBOB, LiDFOB, LiDFOP, LiFSI and LiTFSI.

[0055] LiPF6 has suitable solubility and high ionic conductivity in organic solvents; can form a stable passivation film on the surface of Al foil current collector; can cooperate with carbonate solvents to generate a stable SEI film on the surface of graphite electrode. However, LiPF6 has poor thermal stability and is prone to decomposition reaction. Therefore, the use of a second lithium salt can improve the performance of the lithium salt.

[0056] In some embodiments of the present application, the second lithium salt is preferably LiFSI, LiBF4 or LiBOB, and more preferably LiFSI. Because LiFSI has the advantages of high conductivity, low water sensitivity and good thermal stability.

[0057] In some embodiments of the present application, the mass of LiPF6 accounts for 12-15% of the total mass of the electrolyte, and preferably can be 12%-13%, 13%-14%, 14%-15%, etc.

[0058] In some embodiments of the present application, the second lithium salt accounts for 0-10% of the total mass of the electrolyte, and preferably can be 0-3%, and more preferably 0.5%-1%.

[0059] In some embodiments of the present application, LiPF6 accounts for 80%-100% of the total mass of LiPF6 and the second lithium salt, and the second lithium salt accounts for 0-15% of the total mass of LiPF6 and the second lithium salt. By adjusting the ratio of the lithium salt and the second lithium salt, the performance of the lithium ion battery electrolyte is optimized.

[0060] The present application also provides a preparation method of the electrolyte described above, comprising the following steps:

[0061] The lithium salt is mixed with the organic solvent, and the compound having the structure shown in Formula I is mixed in the mixed solution to prepare the electrolyte. Further, the lithium salt and the organic solvent are mixed under the condition that the temperature is increased by no more than 2°C.

[0062] Since the addition of lithium salt will cause heat release and cause the electrolyte temperature to rise, the lithium salt will be heated to a certain extent and decomposed. Therefore, the mixing of the lithium salt and the solvent needs to be carried out at a low temperature.

[0063] In another aspect of the present application, a lithium ion battery using the electrolyte described above is provided.

[0064] In some embodiments of the present application, the lithium ion battery further comprises a positive active material, a negative active material and the electrolyte described above.

[0065] In some embodiments of the present application, the positive electrode active material chemical formula includes LiaNi x Co y Mn z O2, where 0.9≤a≤1.1, 0.6≤x≤0.8, 0.1≤y≤0.2, 0.1≤z≤0.2, and x+y+z=1.

[0066] In some embodiments of the present invention, the negative electrode active material includes one or more of silicon, silicon-carbon, silicon-oxygen, and silicon-metal compounds.

[0067] The electrolyte and lithium-ion battery provided by the present invention will be described in detail below with reference to specific embodiments.

[0068] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0069] Wherein, B is phenyl isothiocyanate, and the structural formula is as follows:

[0070]

[0071] Examples 1-16 and Comparative Examples 1-4 respectively provide an electrolyte and a lithium-ion battery containing the electrolyte. The composition of the electrolyte and the performance of the battery are shown in Table 1.

[0072] Among them, the preparation method of the above-mentioned electrolyte is as follows: at room temperature, in a glove box filled with argon (H2O<1ppm, O2<1ppm), weigh the organic solvent according to the mass ratio and mix them evenly, then add the lithium salt, continue stirring and use dry ice to cool, ensuring that the electrolyte temperature does not rise by more than 2°C during the addition of the lithium salt, then add the compound of the structure shown in Formula I or B, stir evenly to obtain the electrolyte.

[0073] The lithium-ion battery includes a positive electrode sheet, a negative electrode sheet, and an electrolyte prepared in each group. The preparation method is as follows: the positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive and negative electrode sheets. The process is followed by winding, hot pressing, and tab welding to obtain a bare cell. The bare cell is then placed in an outer packaging aluminum-plastic film and baked in an 85°C oven for 24 hours. The prepared electrolyte is then injected into the dried battery, and the battery is allowed to stand, undergo formation, and volume separation to complete the preparation of the lithium-ion soft-pack battery.

[0074] The positive electrode sheet is prepared by the following method: the positive electrode active material Li (Ni 0.8 Mn 0.1 Co 0.1)O2(NMC811), conductive agent acetylene black (Super P) and binder polyvinylidene fluoride (PVDF) were mixed uniformly in a mass ratio of NMC811:Super P:PVDF = 94:3:3, and uniformly dispersed in 1-methyl-2-pyrrolidone (NMP) to prepare a uniform black slurry. After the mixed slurry was coated on both sides of an aluminum foil, baking, rolling, and cutting, a positive electrode sheet was obtained.

[0075] The negative electrode sheet was prepared by mixing negative electrode active material components silicon monoxide (SiO), artificial graphite, conductive agent acetylene black (Super P) and binder (SBR) uniformly in a mass ratio of silicon monoxide:artificial graphite:Super P:SBR = 11:83:3:3, and uniformly dispersing in deionized water to prepare a uniform black slurry. After the mixed slurry was coated on both sides of a copper foil, baking, rolling, and cutting, a negative electrode sheet was obtained.

[0076] Battery performance test

[0077] 1. Normal temperature direct current resistance (DCR) test: at 25±2℃, the soft package battery obtained by the examples and the comparative examples was charged to 4.4V at 1C, and then discharged for 30min at 1C capacity. After adjusting to 50% SOC, 5C constant current pulse discharge was carried out for 10s, and then charged for 10s. The DCR value of the battery was calculated, recorded as initial DCR. DCR=(voltage before pulse discharge-voltage after pulse discharge) / discharge current x 100%. After the battery was stored at 60℃ for 30 days, the battery was completely cooled to 25±2℃, and the DCR was tested again, recorded as DCR after storage. DCR change rate=(DCR after storage-initial DCR) / initial DCR x 100%, and the recorded results are shown in Table 1.

[0078] 2. Normal temperature cycle performance test: at 25±2℃, the soft package battery of the examples and the comparative examples was subjected to charge-discharge cycle test at 2.8-4.4V with charge-discharge rate of 1C / 1C, and the initial discharge specific capacity and the discharge specific capacity after 1000 cycles were recorded. The capacity retention rate of 1000 cycles=discharge specific capacity of 1000 cycles / initial discharge specific capacity x 100%, and the recorded data are shown in Table 1.

[0079] 3. High temperature storage performance: the soft package battery of the examples and the comparative examples was placed at 60±2℃, and subjected to charge-discharge test at 2.8-4.4V with charge-discharge rate of 1C / 1C. The initial discharge specific capacity was recorded, and then stored at 60±2℃ for 30 days. The charge-discharge test was carried out again and the discharge specific capacity was recorded. The 60℃ storage capacity retention rate=discharge specific capacity after 7 days / initial discharge specific capacity x 100%, and the recorded data are shown in Table 1.

[0080] 4. High temperature gas generation test: the pouch cells of examples and comparative examples were charged at 1C rate to 4.4V at 25±2℃, then charged at 4.4V constant voltage until the current was lower than 0.05C, so that the cells were in 4.4V full charge state. The volume of the full charged cell before storage was measured and recorded as V0; then the full charged cell was put into an oven at 70±2℃, after two days the cell was taken out, and immediately the volume of the cell after storage was measured and recorded as V1. The volume expansion rate at 70℃ storage = (V1-V0) / V0x100%, the results were shown in Table 1.

[0081] Table 1. Battery performance results

[0082]

[0083]

[0084]

[0085] In the table, the ratio of organic solvents is mass ratio.

[0086] From the above table, it can be seen that compared with Comparative Example 1, Examples 1-7 can effectively reduce the volume expansion rate at 70℃ storage, compared with Comparative Example 2, Examples 8-12 can effectively reduce the volume expansion rate at 70℃ storage, compared with Comparative Example 3, Examples 13-16 can effectively reduce the volume expansion rate at 70℃ storage. It shows that the addition of A1-A3 can improve the high temperature storage gas generation performance of the battery.

[0087] Examples 1-7 compared with Comparative Example 1, Examples 8-12 compared with Comparative Example 2, Examples 13-16 compared with Comparative Example 3, show that by limiting the percentage of the mass of the compound having the structure shown in Formula I to the total mass of the electrolyte to the preferred range, the DCR of the battery can be further reduced, and the effect of high temperature storage on DCR is significantly improved, while the normal temperature cycle performance and high temperature storage gas generation performance of the battery are improved. By comparing the electrolyte systems with different contents of A1, A2 or A3, the performance of the electrolyte with 0.5wt% addition of A1, A2 or A3 is better.

[0088] Obviously, the above examples are only examples for clarity, and not a limitation on the embodiments. Based on the above description, other different forms of changes or variations can be made by those of ordinary skill in the art. Here, it is not necessary and impossible to exhaust all embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. An electrolyte, characterized in that: Composed of an organic solvent, a lithium salt and a compound A1: The mass of the compound A1 accounts for 0.5%-1.0% of the total mass of the electrolyte.

2. The electrolyte according to claim 1, characterized in that The organic solvent includes a chain ester and a cyclic ester, the mass of the chain ester accounts for 30-80% of the total mass of the electrolyte, the mass of the cyclic ester accounts for 15%-50% of the total mass of the electrolyte, and the mass ratio of the chain ester to the cyclic ester is (5-9):(2-4).

3. The electrolyte according to claim 2, characterized in that The chain ester includes one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methylpropyl carbonate, diphenyl carbonate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate; the cyclic ester includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, and γ-butyrolactone.

4. The electrolyte according to claim 1, characterized in that The lithium salt includes lithium hexafluorophosphate and a second lithium salt; the second lithium salt includes one or more of lithium tetrafluoroborate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium difluorobisoxalatophosphate, lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide.

5. The electrolyte according to claim 4, characterized in that The mass of LiPF6 accounts for 12-15% of the total mass of the electrolyte, and the mass of the second lithium salt accounts for 0-10% of the total mass of the electrolyte; the LiPF6 accounts for 80%-100% of the total mass of the LiPF6 and the second lithium salt, and the second lithium salt accounts for 0-15% of the total mass of the LiPF6 and the second lithium salt.

6. A lithium-ion battery, characterized in that: The electrolyte comprises a positive electrode active material, a negative electrode active material and the electrolyte according to any one of claims 1 to 5.

7. The lithium-ion battery according to claim 6, characterized in that: The positive electrode active material chemical formula includes LiaNi x Co y Mn z O2, where 0.9≤a≤1.1, 0.6≤x≤0.8, 0.1≤y≤0.2, 0.1≤z≤0.2, and x+y+z=1.

8. The lithium-ion battery according to claim 6, characterized in that: The negative electrode active material includes one or more of silicon, silicon-carbon, silicon-oxygen, and silicon-metal compounds.

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