Lithium ion battery nonaqueous electrolyte and lithium ion battery

Abstract

The application relates to the technical field of electrochemistry, in particular to a lithium ion battery nonaqueous electrolyte and a lithium ion battery. The lithium ion battery nonaqueous electrolyte provided by the application comprises a nonaqueous organic solvent, a lithium salt and a spirocyclic ester compound. The application further provides a lithium ion battery comprising the lithium ion battery nonaqueous electrolyte. The spirocyclic ester compound in the lithium ion battery nonaqueous electrolyte provided by the application helps to form a stable SEI film in the charging and discharging process of the lithium ion battery, so that the prepared lithium ion battery also has excellent electrochemical performance under high-temperature conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemistry, in particular to a lithium ion battery non-aqueous electrolyte and a lithium ion battery. BACKGROUND

[0002] Lithium ion batteries have made great progress in the field of portable electronic products due to their high working voltage, high safety, long life, no memory effect and other characteristics. With the development of new energy vehicles, lithium ion batteries have great application prospects in new energy vehicle power supply systems.

[0003] The lithium ion battery cell is mainly composed of a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is a key factor affecting the high temperature performance of the battery. The commonly used electrolyte in lithium ion batteries is non-aqueous electrolyte, and the additives in the non-aqueous electrolyte are particularly important for the performance of the battery at high temperature. During the initial charging of the lithium ion battery, lithium ions in the positive electrode material are deintercalated and inserted into the carbon negative electrode through the electrolyte. Because lithium has high reactivity, the electrolyte reacts on the surface of the carbon negative electrode to produce Li2CO3, Li2O, LiOH and other compounds, thereby forming a passivation film on the surface of the negative electrode. The passivation film is called solid electrolyte interface film (SEI). The SEI film formed during the initial charging process can prevent the electrolyte from further decomposing on the surface of the carbon negative electrode, and also serves as a lithium ion tunnel, allowing only lithium ions to pass through. However, during the charging and discharging process of the lithium battery, the volume change of the electrode may cause the SEI film to break, which may cause the negative electrode of the battery to be exposed again and react with the electrolyte, while generating gas, thereby increasing the internal pressure of the lithium battery and reducing the cycle life of the battery. When the battery is stored or reacted at high temperature, the SEI film is more likely to break, thereby causing the cycle performance of the lithium battery to decrease more obviously under high temperature conditions. Therefore, the SEI film determines the performance of the lithium ion battery.

[0004] In order to improve the performance of lithium ion batteries, many researchers have added different negative electrode film-forming additives to the electrolyte, such as vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, 1,3-propane sulfone lactone and other additives to improve the quality of the SEI film and thus improve the performance of the battery. However, the high temperature storage and cycle performance of the lithium ion battery is still poor after adding the above substances to the electrolyte. Therefore, it is crucial to develop a non-aqueous electrolyte that can ensure excellent electrochemical performance of lithium ion batteries at high temperature. SUMMARY

[0005] To solve the above technical problems, the present application provides a lithium ion battery non-aqueous electrolyte which can improve the high temperature storage and cycle performance of the lithium ion battery.

[0006] The present application adopts the following technical solutions:

[0007] A non-aqueous electrolyte for lithium-ion batteries includes a non-aqueous organic solvent, a lithium salt, and a spirocyclic ester compound, as shown in structural formula 1:

[0008]

[0009] Where X1 is One of the groups; R9 is a halogen atom, a halogenated or non-halogenated alkoxy group with 1-10 carbon atoms;

[0010] Preferably, the halogen atom is selected from one of fluorine, chlorine, bromine, and iodine;

[0011] Preferably, R9 is selected from one of fluoromethoxy, fluoroethoxy, fluoropropoxy, fluorobutoxy, fluoropentoxy, fluorohexoxy, fluoroheptoxy, fluorooctoxy, fluorononoxy, fluorodecoxy, methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, octoxy, nonoxy, and decoxy.

[0012] Preferably, R9 is one of a halogen atom or a halogenated or non-halogenated alkoxy group having 1-6 carbon atoms;

[0013] Preferably, the halogen atom is selected from one of fluorine, chlorine, bromine, and iodine;

[0014] Preferably, R9 is selected from one of fluoromethoxy, fluoroethoxy, fluoropropoxy, fluorobutoxy, fluoropentoxy, fluorohexoxy, methoxy, ethoxy, propoxy, butoxy, pentoxy, and hexoxy.

[0015] X2 is One of the groups; R 10 It is one of the halogen atom and a halogenated or non-halogenated alkoxy group having 1-10 carbon atoms;

[0016] Preferably, the halogen atom is selected from one of fluorine, chlorine, bromine, and iodine;

[0017] Preferred, R 10 It is selected from one of the following: fluoromethoxy, fluoroethoxy, fluoropropoxy, fluorobutoxy, fluoropentoxy, fluorohexoxy, fluoroheptoxy, fluorooctoxy, fluorononoxy, fluorodecoxy, methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, octoxy, nonoxy, and decoxy.

[0018] Preferred, R 10 It is one of the halogen atom and a halogenated or non-halogenated alkoxy group having 1-6 carbon atoms;

[0019] Preferably, the halogen atom is selected from one of fluorine, chlorine, bromine, and iodine;

[0020] Preferred, R 10 It is selected from one of fluoromethoxy, fluoroethoxy, fluoropropoxy, fluorobutoxy, fluoropentoxy, fluorohexoxy, methoxy, ethoxy, propoxy, butoxy, pentoxy, and hexoxy.

[0021] R1, R2, R3, R4, R5, R6, R7, and R8 are each independently selected from one of the following: hydrogen atom, halogen atom, or halogenated or non-halogenated alkoxy group with 1 to 10 carbon atoms.

[0022] Preferably, the halogen atom is selected from one of fluorine, chlorine, bromine, and iodine;

[0023] Preferably, R1, R2, R3, R4, R5, R6, R7, and R8 are each independently selected from one of the following: fluoromethoxy, fluoroethoxy, fluoropropoxy, fluorobutoxy, fluoropentoxy, fluorohexoxy, fluoroheptoxy, fluorooctoxy, fluorononoxy, fluorodecoxy, methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, octoxy, nonoxy, and decoxy.

[0024] Preferably, R1, R2, R3, R4, R5, R6, R7, and R8 are each independently selected from one of hydrogen atoms, halogen atoms, and halogenated or non-halogenated alkoxy groups with 1 to 3 carbon atoms;

[0025] Preferably, the halogen atom is selected from one of fluorine, chlorine, bromine, and iodine;

[0026] Preferably, R1, R2, R3, R4, R5, R6, R7, and R8 are each independently selected from one of fluoromethoxy, fluoroethoxy, fluoropropoxy, methoxy, ethoxy, and propoxy.

[0027] Furthermore, spirocyclic esters include one of categories 1-4:

[0028]

[0029]

[0030] Where X1 is One of the groups; R9 is one of the halogen atom and one of the halo- or non-halogenated alkoxy groups with 1-10 carbon atoms;

[0031] Preferably, the halogen atom is selected from one of fluorine, chlorine, bromine, and iodine;

[0032] Preferably, R9is selected from one of fluoro-methoxy, fluoro-ethoxy, fluoro-propoxy, fluoro-butanoyl, fluoro-pentanoyl, fluoro-hexanoyl, methoxy, ethoxy, propoxy, butanoyl, pentanoyl, hexanoyl;

[0033] Preferably, R9is one of a halogen atom, a halogenated or non-halogenated alkyl group having 1 to 6 carbon atoms;

[0034] Preferably, the halogen atom is selected from one of fluorine, chlorine, bromine, iodine;

[0035] Preferably, R9is selected from one of fluoro-methoxy, fluoro-ethoxy, fluoro-propoxy, fluoro-butanoyl, fluoro-pentanoyl, fluoro-hexanoyl, methoxy, ethoxy, propoxy, butanoyl, pentanoyl, hexanoyl.

[0036] X2is one of a halogen atom, a halogenated or non-halogenated alkyl group having 1 to 10 carbon atoms; 10

[0037] Preferably, the halogen atom is selected from one of fluorine, chlorine, bromine, iodine;

[0038] Preferably, R 10 is selected from one of fluoro-methoxy, fluoro-ethoxy, fluoro-propoxy, fluoro-butanoyl, fluoro-pentanoyl, fluoro-hexanoyl, methoxy, ethoxy, propoxy, butanoyl, pentanoyl, hexanoyl.

[0039] Preferably, R 10 is one of a halogen atom, a halogenated or non-halogenated alkyl group having 1 to 6 carbon atoms;

[0040] Preferably, the halogen atom is selected from one of fluorine, chlorine, bromine, iodine;

[0041] Preferably, R 10 is selected from one of fluoro-methoxy, fluoro-ethoxy, fluoro-propoxy, fluoro-butanoyl, fluoro-pentanoyl, fluoro-hexanoyl, methoxy, ethoxy, propoxy, butanoyl, pentanoyl, hexanoyl.

[0042] R1, R2, R3, R4, R5, R6, R7, R8are each independently selected from one of a hydrogen atom, a halogen atom, a halogenated or non-halogenated alkyl group having 1 to 10 carbon atoms;

[0043] ​Preferably, the halogen atom is selected from one of fluorine, chlorine, bromine, iodine;

[0044] Preferably, R1, R2, R3, R4, R5, R6, R7, R8are each independently selected from one of fluoromethoxy, fluoroethoxy, fluoropropoxy, fluorobutanoxyl, fluoropentanoxyl, fluorohexanoxyl, fluorohexanoxyl, fluorooctanoxyl, fluorononanoxyl, fluorodecanoxyl, methoxy, ethoxy, propoxy, butanoxyl, pentanoxyl, hexanoxyl, heptanoxyl, octanoxyl, nonanoxyl, decanoxyl.

[0045] Preferably, R1, R2, R3, R4, R5, R6, R7, R8are each independently selected from one of hydrogen atom, halogen atom, halogenated or non-halogenated alkyl of 1-3 carbon atoms.

[0046] Preferably, the halogen atom is selected from one of fluorine, chlorine, bromine, iodine;

[0047] Preferably, R1, R2, R3, R4, R5, R6, R7, R8are each independently selected from one of fluoromethoxy, fluoroethoxy, fluoropropoxy, methoxy, ethoxy, propoxy.

[0048] Further, the spirocyclic ester compound comprises one of compounds 1-65:

[0049]

[0050]

[0051]

[0052]

[0053]

[0054] Further, the mass of the spirocyclic ester compound is 0.01%-5.0% of the total mass of the non-aqueous electrolyte of the lithium ion battery. When the mass of the spirocyclic ester compound is less than 0.01% of the total mass of the non-aqueous electrolyte, the content of the compound in the electrolyte is too low to form a complete passivation film on the surface of the negative electrode, thus it is difficult to significantly improve the high-temperature performance of the non-aqueous electrolyte battery, and the internal resistance of the battery is not significantly reduced. When the mass of the spirocyclic ester compound is more than 5.0% of the total mass of the non-aqueous electrolyte, a too thick SEI passivation film is easily formed on the surface of the negative electrode, which in turn increases the internal resistance of the battery, and the capacity retention rate of the battery is significantly deteriorated. Preferably, the mass of the spirocyclic ester compound is 0.5%-3.0% of the total mass of the non-aqueous electrolyte of the lithium ion battery. At this time, the electrochemical performance of the prepared lithium ion battery is more excellent.

[0055] Further, the non-aqueous electrolyte of the lithium ion battery of the present application can further comprise a sulfonate or a carbonate.

[0056] Preferably, the sulfonate is selected from one or more of 1,3-propane sultone (1,3-PS), 1,4-butane sultone (BS), 1,3-propene sultone (PST).

[0057] Preferably, the carbonate is selected from one or more of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC).

[0058] Further, the amount of the additive is 0.01% to 5.0% of the total mass of the non-aqueous electrolyte. Preferably, the amount of the additive is 0.2% to 3.0% of the total mass of the non-aqueous electrolyte. More preferably, the amount of the additive is 0.5% to 3.0% of the total mass of the non-aqueous electrolyte.

[0059] Further, the lithium salt is one or more of LiPF6, LiBOB, LiDFOB, LiBF4, LiSbF6, LiAsF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, or LiN(SO2F)2.

[0060] Preferably, the lithium salt is LiPF6or a mixture of LiPF6and other lithium salts.

[0061] Further, the mass of the lithium salt is 0.1% to 15% of the total mass of the non-aqueous electrolyte.

[0062] Preferably, the mass of the lithium salt is 1% to 13% of the total mass of the non-aqueous electrolyte.

[0063] Preferably, the mass of the lithium salt is 5% to 13% of the total mass of the non-aqueous electrolyte.

[0064] Preferably, the mass of the lithium salt is 10% to 12% of the total mass of the non-aqueous electrolyte.

[0065] Further, the non-aqueous organic solvent comprises at least one cyclic carbonate and at least one chain carbonate.

[0066] Further, the cyclic carbonate comprises one or more of vinyl carbonate, propylene carbonate, or butylene carbonate.

[0067] Further, the chain carbonate comprises one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, or methyl propyl carbonate.

[0068] The present application also provides a lithium ion battery comprising the non-aqueous electrolyte of the lithium ion battery of the present application, a positive electrode, a negative electrode, and a separator.

[0069] Further, the positive electrode includes a positive electrode active material, the positive electrode active material includes one or more of LiCoO2, LiNiO2, LiMn2O4, LiCo 1-y M y O2, LiNi 1-y M y O2, LiMn 2-y M y O4, and LiNi x Co y Mn z M 1-x-y-z O2, wherein M is selected from one or more of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, or Ti, and 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1.

[0070] Further, the active material of the positive electrode includes LiFe 1-x M x PO4, wherein M is selected from one or more of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, or Ti, and 0≤x<1.

[0071] Further, the positive electrode further includes a positive electrode current collector for leading out current, and the positive electrode active material is coated on the positive electrode current collector.

[0072] Further, the negative electrode includes a negative electrode active material, and the negative electrode active material includes one of carbon material, metal alloy, lithium-containing oxide, and silicon-containing material.

[0073] Further, the negative electrode further includes a negative electrode current collector for leading out current, and the negative electrode active material is coated on the negative electrode current collector.

[0074] Further, a separator is arranged between the positive electrode and the negative electrode, and the separator can be a polyethylene porous film.

[0075] (1) The lithium ion battery non-aqueous electrolyte provided by the application, by adding the spiro ester compound shown in structural formula 1 in the electrolyte, the spiro ester compound shown in structural formula 1 will undergo reduction reaction on the negative electrode to crack into open ring multi-valent anion radicals, the generated radical end group will further react to form cross-linked multi-valent salt, and this cross-linked multi-valent salt will form a dense network structure SEI film on the negative electrode surface. In addition, the ring tension of the compound shown in structural formula 1 makes the SEI film surface have greater flexibility, even at high temperature, the increase of the electrode interface film impedance is relatively slow, which can effectively reduce the decomposition of the electrolyte solvent on the negative electrode and reduce the generation of gas, thereby improving the electrochemical performance of the lithium ion battery under high temperature conditions.

[0076] (2) The cross-linked multivalent salt also has better anti-oxidation property, slows down the oxidation process of electrolyte, and can significantly improve the cycle performance and high-temperature storage performance of the lithium ion battery. DETAILED DESCRIPTION

[0077] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0078] Embodiment 1

[0079] 1) Preparation of non-aqueous electrolyte:

[0080] Vinyl carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) were mixed in a mass ratio of EC:DEC:EMC = 1:1:1, then lithium hexafluorophosphate (LiPF6) was added to a molar concentration of 1 mol / L, and the compound 1 was added in the mass percentage shown in Table 2 in Example 1, based on 100% of the total weight of the non-aqueous electrolyte.

[0081] 2) Preparation of positive plate:

[0082] The positive active material lithium nickel cobalt manganese oxide LiNi 0.5 Co 0.2 Mn 0.3 O2, conductive carbon black Super-P and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 93:4:3, and then they were dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a positive slurry. The slurry was uniformly coated on both sides of an aluminum foil, and then the aluminum foil was dried, calendered and vacuum dried, and then an aluminum lead wire was welded on the aluminum foil by an ultrasonic welding machine to obtain a positive plate, and the thickness of the plate was between 120-150 μm.

[0083] 3) Preparation of negative plate:

[0084] The negative active material artificial graphite, conductive carbon black Super-P, binder styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) were mixed in a mass ratio of 94:1:2.5:2.5, and then they were dispersed in deionized water to obtain a negative slurry. The slurry was coated on both sides of a copper foil, and then the copper foil was dried, calendered and vacuum dried, and then a nickel lead wire was welded on the copper foil by an ultrasonic welding machine to obtain a negative plate, and the thickness of the plate was between 120-150 μm.

[0085] 4) Preparation of battery cell:

[0086] A three-layer separator with a thickness of 20 μm is placed between the positive and negative plates. Then, the sandwich structure composed of the positive plate, negative plate and separator is wound up, and the wound body is flattened and placed in an aluminum foil packaging bag. It is then vacuum baked at 75°C for 48 hours to obtain the cell to be injected with electrolyte.

[0087] 5) Electrolyte injection and formation of the battery cell:

[0088] In a glove box where the dew point is controlled below -40°C, the electrolyte prepared above is injected into the battery cell, vacuum sealed, and left to stand for 24 hours.

[0089] The initial formation was then performed as follows: constant current charging at 0.05C for 180 minutes, constant current charging at 0.2C to 3.95V, followed by a second vacuum sealing. Then, it was further charged at a constant current of 0.2C to 4.2V, left to stand at room temperature for 24 hours, and finally discharged at a constant current of 0.2C to 3.0V to obtain a LiNi alloy. 0.5 Co 0.2 Mn 0.3 O2 / artificial graphite lithium-ion battery.

[0090] 6) Performance testing of lithium-ion batteries prepared in the examples and comparative examples

[0091] To verify the effect of the non-aqueous electrolyte on the performance of the lithium-ion battery of the present invention, relevant performance tests were conducted on the lithium-ion batteries prepared in the following embodiments and comparative examples. The performance tests included high-temperature cycle performance tests and high-temperature storage performance tests, and the specific test methods are as follows:

[0092] (1) High-temperature cycling performance test

[0093] The lithium-ion batteries prepared in the examples and comparative examples were placed in an oven at a constant temperature of 45°C and charged at a constant current of 1C to 4.2V (LiNi). 0.5 Co 0.2 Mn 0.3 The O2 / artificial graphite lithium-ion battery is charged at a constant voltage until the current drops to 0.02C, and then discharged at a constant current of 1C to 3.0V. This cycle is repeated, and the discharge capacity of the first and last discharge cycles is recorded.

[0094] Calculate the capacity retention rate during the cycle using the following formula:

[0095] Battery capacity retention rate (%) = Last discharge capacity / First discharge capacity × 100%.

[0096] (2) High-temperature storage performance test

[0097] The lithium-ion batteries prepared in the examples and comparative examples were charged to 4.2V (LiNi) at room temperature using a 1C constant current and constant voltage method after formation.0.5 Co 0.2 Mn 0.3 (O2 / artificial graphite lithium-ion battery), the initial discharge capacity and initial battery thickness were measured. Then, after storing the battery at 60℃ for 30 days, it was discharged at 1C to 3V, and the retention capacity, recovery capacity, and battery thickness after storage were measured. The calculation formula is as follows:

[0098] Battery capacity retention rate (%) = Retained capacity / Initial capacity × 100%;

[0099] Battery capacity recovery rate (%) = Recovered capacity / Initial capacity × 100%;

[0100] Thickness expansion rate (%) = (Battery thickness after storage - Initial battery thickness) / Initial battery thickness × 100%.

[0101] Example 2

[0102] As shown in Table 2, except that 1.0% of compound 1 was replaced with 1.0% of compound 3 in the preparation of the non-aqueous electrolyte, the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 3.

[0103] Example 3

[0104] As shown in Table 2, except that 1.0% of compound 1 was replaced with 1.0% of compound 4 in the preparation of the non-aqueous electrolyte, the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 3.

[0105] Example 4

[0106] As shown in Table 2, except that 1.0% of compound 1 was replaced with 1.0% of compound 5 in the preparation of the non-aqueous electrolyte, the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 3.

[0107] Example 5

[0108] As shown in Table 2, except that 1.0% of compound 1 was replaced with 1.0% of compound 6 in the preparation of the non-aqueous electrolyte, the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 3.

[0109] Example 6

[0110] As shown in Table 2, except that 1.0% of compound 1 was replaced with 1.0% of compound 7 in the preparation of the non-aqueous electrolyte, the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 3.

[0111] Example 7

[0112] As shown in Table 2, except that 1.0% of compound 1 was replaced with 1.0% of compound 8 in the preparation of the non-aqueous electrolyte, the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 3.

[0113] Example 8

[0114] As shown in Table 2, except that 1.0% of compound 1 was replaced with 1.0% of compound 9 in the preparation of the non-aqueous electrolyte, the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 3.

[0115] Comparative Example 1

[0116] As shown in Table 2, except that 1.0% of compound 1 was not added in the preparation of the electrolyte, everything else was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 3.

[0117] Comparative Example 2

[0118] As shown in Table 2, except that 1.0% of compound 1 was replaced with 1.0% of vinylene carbonate (VC) in the preparation of the electrolyte, the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 3.

[0119] Comparative Example 3

[0120] As shown in Table 2, except that 1.0% of compound 1 was replaced with 1.0% of vinyl sulfate (DTD) in the preparation of the electrolyte, the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 3.

[0121] Comparative Example 4

[0122] As shown in Table 2, except that 1.0% of compound 1 was replaced with 1.0% of 1,3-propanesulfonate lactone (PS) in the preparation of the electrolyte, the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 3.

[0123] Table 1. Structural formulas of spirocyclic ester compound 1 and compounds 3-9 used in the embodiments of the present invention.

[0124]

[0125] Table 2 shows the content of spirocyclic esters and other additives in Examples 1-8 and Comparative Examples 1-4.

[0126]

[0127]

[0128] Table 3 shows the electrochemical performance test results of the batteries prepared in Examples 1-8 and Comparative Examples 1-4.

[0129]

[0130] Comparing the test results of Examples 1-8 and Comparative Examples 1 and 4, it can be seen that, compared with not adding the spirocyclic ester compounds of this invention or adding DTD sulfate compounds to the electrolyte, adding 1.0% of compounds 1-8 to the non-aqueous electrolyte can significantly improve the high-temperature storage and cycle performance of lithium-ion batteries. After being stored at 60°C for 30 days, the battery's capacity retention rate and capacity recovery rate can both reach over 87%.

[0131] Example 9

[0132] As shown in Table 4, except that in the preparation of the non-aqueous electrolyte, 1.0% of compound 1 was replaced with 0.01% of compound 1, everything else was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 5.

[0133] Example 10

[0134] As shown in Table 4, except that in the preparation of the non-aqueous electrolyte, 1.0% of compound 1 was replaced with 0.1% of compound 1, everything else was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 5.

[0135] Example 11

[0136] As shown in Table 4, except that in the preparation of the non-aqueous electrolyte, 1.0% of compound 1 was replaced with 0.5% of compound 1, everything else was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 5.

[0137] Example 12

[0138] As shown in Table 4, except that 1.0% of compound 1 was replaced with 2.0% of compound 1 in the preparation of the non-aqueous electrolyte, the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 5.

[0139] Example 13

[0140] As shown in Table 4, except that 1.0% of compound 1 was replaced with 3.0% of compound 1 in the preparation of the non-aqueous electrolyte, the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 5.

[0141] Example 14

[0142] As shown in Table 4, except that 1.0% of compound 1 was replaced with 5.0% of compound 1 in the preparation of the non-aqueous electrolyte, the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 5.

[0143] Table 4 shows the content of spirocyclic esters and other additives in Examples 9-14.

[0144] Example Compounds and levels Other additives and levels Example 9 Compound 1 : 0.01% - Example 10 Compound 1 : 0.1% - Example 11 Compound 1 : 0.5% - Example 12 Compound 1 : 2% - Example 13 Compound 1 : 3% - Example 14 Compound 1 : 5% -

[0145] Table 5. Electrochemical performance test results of the batteries prepared in Examples 9-14

[0146]

[0147]

[0148] According to the test results in Examples 1, 9-14, and Comparative Example 1, adding 0.1%-5.0% of the compound shown in Structural Formula 1 to the electrolyte can improve battery performance. When 0.5%, 1.0%, 2.0%, and 3.0% of Compound 1 are added, the battery capacity retention rate is further improved to over 90% after 500 cycles at 45°C and 1C. After storage at 60°C for 30 days, the capacity retention rate and capacity recovery rate of the battery can both reach over 90%, and the thickness expansion rate is further reduced. Therefore, the present invention limits the content of the added spirocyclic ester compound to 0.1%-5.0%, preferably 0.5%-3.0%.

[0149] Example 15

[0150] As shown in Table 6, except that in the preparation of the non-aqueous electrolyte, 1.0% of compound 1 was replaced with 0.1% of compound 1 and 1.0% of vinylene carbonate (VC), the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 7.

[0151] Example 16

[0152] As shown in Table 6, except that in the preparation of the non-aqueous electrolyte, 1.0% of compound 1 was replaced with 0.5% of compound 1 and 1.0% of vinylene carbonate (VC), the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 7.

[0153] Example 17

[0154] As shown in Table 6, except that in the preparation of the non-aqueous electrolyte, 1.0% of compound 1 was replaced with 1.0% of compound 1 and 1.0% of vinylene carbonate (VC), the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 7.

[0155] Example 18

[0156] As shown in Table 6, except that in the preparation of the non-aqueous electrolyte, 1.0% of compound 1 was replaced with 5.0% of compound 1 and 1.0% of vinylene carbonate (VC), the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 7.

[0157] Example 19

[0158] As shown in Table 6, except that in the preparation of the non-aqueous electrolyte, 1.0% of compound 1 was replaced with 0.1% of compound 1 and 1.0% of vinylene carbonate (VC), the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 7.

[0159] Example 20

[0160] As shown in Table 6, except that in the preparation of the non-aqueous electrolyte, 1.0% of compound 1 was replaced with 0.5% of compound 1 and 1.0% of 1,3-propanesulfonate lactone (PS), the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 7.

[0161] Example 21

[0162] As shown in Table 6, except that in the preparation of the non-aqueous electrolyte, 1.0% of compound 1 was replaced with 1.0% of compound 1 and 1.0% of 1,3-propanesulfonate lactone (PS), the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 7.

[0163] Example 22

[0164] As shown in Table 6, except that in the preparation of the non-aqueous electrolyte, 1.0% of compound 1 was replaced with 5.0% of compound 1 and 1.0% of 1,3-propanesulfonate lactone (PS), the rest was the same as in Example 1. The high-temperature performance data obtained by the test are shown in Table 7.

[0165] Table 6 shows the content of spirocyclic esters and other additives in Examples 15-22.

[0166]

[0167]

[0168] Table 7 shows the electrochemical performance test results of the batteries prepared in Examples 15-22.

[0169]

[0170] Data from Examples 15-18, compared to Examples 10, 11, 1, 14 and Comparative Example 2, show that the simultaneous addition of the compound shown in Structural Formula 1 and VC results in superior high-temperature cycle performance and high-temperature storage performance compared to the addition of either the compound shown in Structural Formula 1 or VC alone. The electrolyte provided in this invention, containing 1% spirocyclic ester compound and 1% vinylene carbonate (VC), enables the assembled battery to achieve a capacity retention rate of 92.6% after 500 cycles at 45°C, a capacity retention rate of 93.5% after 30 days of storage at 60°C, a capacity recovery rate of 93.8%, and a thickness expansion rate reduced to 6.3%. Data from Examples 19-22, compared to Examples 10, 11, 1, 14 and Comparative Example 4, show that the simultaneous addition of the compound shown in Structural Formula 1 and PS results in superior high-temperature cycle performance and high-temperature storage performance compared to the addition of either the compound shown in Structural Formula 1 or PS alone. The electrolyte provided in this invention contains 1% spirocyclic ester compound and 1% 1,3-propanesulfonate lactone (PS), which enables the assembled battery to achieve a capacity retention rate of 92.8% after 500 cycles at 45°C, a capacity retention rate of 93.8% after 30 days of storage at 60°C, a capacity recovery rate of 93.9%, and a thickness expansion rate of 6.0%.

[0171] In summary, the present invention adds spirocyclic ester compounds to the electrolyte, and the prepared electrolyte can ensure that a stable SEI film can be formed in the lithium-ion battery during charging and discharging, thereby ensuring that the lithium-ion battery has excellent electrochemical performance.

[0172] The present invention has been further described above with reference to specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the nature and scope of the present invention. Various modifications made to the above embodiments by those skilled in the art after reading this specification are all within the scope of protection of the present invention.

Claims

1. A non-aqueous electrolyte for lithium-ion batteries, characterized in that, This includes non-aqueous organic solvents, lithium salts, and spirocyclic esters, as shown in structural formula 1: Where X1 is One of the groups; R9 is one of the halogen atom and one of the halo- or non-halogenated alkoxy groups with 1-10 carbon atoms; X2 is One of the groups; R 10 It is one of the halogen atom and a halogenated or non-halogenated alkoxy group having 1-10 carbon atoms; R1, R2, R3, R4, R5, R6, R7, and R8 are each independently selected from one of the following: hydrogen atom, halogen atom, or halogenated or non-halogenated alkoxy group with 1 to 10 carbon atoms. The spirocyclic ester compounds include one of categories 1-3: Among them, R9 is one of the halogen atom and the number of carbon atoms in the halogen or non-halogenated alkoxy group; R 10 It is one of the halogen atom and a halogenated or non-halogenated alkoxy group having 1-10 carbon atoms; R1, R2, R3, R4, R5, R6, R7, and R8 are each independently selected from one of the following: hydrogen atom, halogen atom, or halogenated or non-halogenated alkoxy group with 1 to 10 carbon atoms.

2. The non-aqueous electrolyte for lithium-ion batteries according to claim 1, characterized in that, The halogen atom is selected from fluorine, chlorine, bromine, and iodine; the halogenated or non-halogenated alkoxy group of the 1-10 carbon atoms is selected from one of fluoromethoxy, fluoroethoxy, fluoropropoxy, fluorobutoxy, fluoropentoxy, fluorohexoxy, fluoroheptoxy, fluorooctoxy, fluorononoxy, fluorodecoxy, methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, octoxy, nonoxy, and decoxy.

3. The non-aqueous electrolyte for lithium-ion batteries according to claim 1, characterized in that, The spirocyclic ester compounds include one of compounds 1-6 and compounds 10-45:

4. The non-aqueous electrolyte for lithium-ion batteries according to claim 1, characterized in that, The mass of the spirocyclic ester compound is 0.01%-5.0% of the total mass of the non-aqueous electrolyte in the lithium-ion battery.

5. The non-aqueous electrolyte for lithium-ion batteries according to claim 1, characterized in that, It also includes sulfonates or carbonates; The sulfonate esters include one or more of 1,3-propanesulfonyl lactone (1,3-PS), 1,4-butanesulfonyl lactone (BS), and 1,3-propenesulfonyl lactone (PST); The carbonate includes one or more of vinylene carbonate (VC), ethylene ethylene carbonate (VEC), and fluoroethylene carbonate (FEC).

6. The non-aqueous electrolyte for lithium-ion batteries according to claim 1, characterized in that, The lithium salt is selected from one or more of LiPF6, LiBOB, LiDFOB, LiBF4, LiSbF6, LiAsF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3 or LiN(SO2F)2.

7. The non-aqueous electrolyte for lithium-ion batteries according to claim 1, characterized in that, The non-aqueous organic solvent includes at least one cyclic carbonate and at least one chain carbonate.

8. The non-aqueous electrolyte for lithium-ion batteries according to claim 7, characterized in that, The cyclic carbonates include one or more of ethylene carbonate, propylene carbonate, or butene carbonate; the chain carbonates include one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, or methyl propyl carbonate.

9. A lithium-ion battery, characterized in that, Includes the non-aqueous electrolyte, positive electrode, negative electrode, and separator of the lithium-ion battery as described in any one of claims 1-8.

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