WO2018214211A1 - Lithium-ion battery non-aqueous electrolyte and lithium-ion battery - Google Patents

Abstract

A lithium-ion battery non-aqueous electrolyte for resolving the problem in which, with conventional lithium-ion battery non-aqueous electrolytes, it is difficult to obtain both good discharge performance at low temperatures and good performance at high temperatures. The lithium-ion battery non-aqueous electrolyte comprises compound A represented by structural formula I and compound B represented by structural formula B. In the structural formula I, R1 is a C1-C4 alkyl group, and m is 1 or 2. In the structural formula II, R2, R3, R4, R5, R6, and R7 are independently selected from at least one of a hydrogen atom, a halogen atom, or a C1-C5 group. The lithium-ion battery non-aqueous electrolyte provided by the invention uses the combination of compound A and compound B, and thereby achieves each of cycling performance, storage performance at high temperatures, and discharge performance at low temperatures for a lithium-ion battery containing the non-aqueous electrolyte.

Description

Lithium-ion battery non-aqueous electrolyte and lithium-ion battery Technical field

The invention belongs to the field of lithium ion batteries, and in particular relates to a lithium ion battery non-aqueous electrolyte and a lithium ion battery.

Background technique

A lithium ion battery is a secondary battery that operates by moving lithium ions between a positive electrode and a negative electrode. Lithium-ion batteries have significant advantages such as high operating voltage, high energy density, low self-discharge rate, and no memory effect. They are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power plants, as well as power tools, electric bicycles, and electric motorcycles. Cars, electric vehicles, military equipment, aerospace and many other fields. With the rapid development of new energy vehicles and energy storage, people have put forward higher requirements for the performance of lithium-ion power batteries. At present, lithium-ion power batteries have insufficient high-temperature cycle life, and cannot meet high and low temperature performance.

Non-aqueous electrolytes are the key factors affecting the cycle and high and low temperature performance of the battery. In particular, the additives in the electrolyte play a decisive role in the performance of the electrolyte. Currently, a practical lithium ion battery nonaqueous electrolyte is usually a conventional film forming additive such as vinylene carbonate (VC). In order to ensure the excellent cycle performance of the battery, especially to ensure long life, it is generally necessary to add a larger amount of VC. However, too high VC content can degrade the performance of the battery in many aspects, such as easy gas production during high temperature storage, resulting in battery bulging; and high content of VC will significantly increase the battery interface impedance, degrading the low temperature performance of the battery. The patent discloses an electrolyte containing an RSO ₃ Si(C _m H _2m+1 ) ₃ compound which can improve the low temperature discharge performance and the normal temperature cycle performance of the battery. However, it has been found that the electrolyte containing RSO ₃ Si(C _m H _2m+1 ) ₃ compound can improve the low-temperature discharge performance of the battery and reduce the battery impedance, but the high-temperature performance of the battery is not ideal, and the battery cannot be put into practical use.

Summary of the invention

The object of the present invention is to provide a high temperature performance (including high temperature cycle performance and high The non-aqueous electrolyte of lithium ion battery with good temperature storage performance and low impedance is designed to solve the problem that the existing lithium ion battery electrolyte is difficult to achieve good low temperature discharge performance and high temperature performance.

Another object of the present invention is to provide a lithium ion battery.

The present invention is achieved by a lithium ion battery nonaqueous electrolyte comprising the compound A represented by the following structural formula I and the compound B represented by the structural formula II,

In the formula I, R ₁ is a C1-C4 hydrocarbon group, and m is 1 or 2;

In the formula II, R ₂ , R ₃ , R ₄ , R ₅ , R ₆ and R ₇ are each independently selected from a hydrogen atom, a halogen atom or a C1-C5 group.

Preferably, the C1-C5 group is selected from the group consisting of a C1-C5 hydrocarbon group, a halogenated hydrocarbon group, an oxygen-containing hydrocarbon group, a silicon-containing hydrocarbon group, and a cyano-substituted hydrocarbon group.

Preferably, the R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , and R ₇ are each independently selected from a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, and a trimethyl group. One of a siloxy group, a cyano group or a trifluoromethyl group.

Preferably, the compound B is selected from one or more of the compounds 1-9 shown by the following structures.

Preferably, the compound B has a mass percentage of 0.1 to 5% based on 100% of the total mass of the lithium ion battery nonaqueous electrolyte.

Preferably, R ₁ is _one of methyl, ethyl, propyl, isopropyl, butyl, allyl, propargyl, trifluoromethyl, trifluoroethyl.

Preferably, the compound A is selected from the group consisting of trimethylsilyl methanesulfonate, trimethylsilylethanesulfonate, trimethylsilylpropanesulfonate, trimethylsilylisopropylsulfonate , trimethylsilyl butyl sulfonate, trimethylsilyl propyl sulfonate, trimethylsilyl propargyl sulfonate, trimethylsilyl trifluoromethanesulfonate, top three One or more of a silyl trifluoroethyl sulfonate and a triethylsilyl methanesulfonate.

Preferably, the compound A has a mass percentage of 0.1 to 2% based on 100% of the total mass of the lithium ion battery nonaqueous electrolyte.

Preferably, the lithium ion nonaqueous electrolytic solution further includes at least one of an unsaturated cyclic carbonate compound, a fluorinated cyclic carbonate compound, and a sultone compound.

Preferably, the unsaturated cyclic carbonate compound comprises at least one of vinylene carbonate (VC) and ethylene carbonate (VEC).

Preferably, the fluorocyclic carbonate compound comprises fluoroethylene carbonate (FEC).

Preferably, the sultone compound comprises 1,3-propane sultone (PS), 1,4-butane sultone (BS), and 1,3-propene sultone (PST). At least one.

Preferably, the lithium ion battery nonaqueous electrolyte comprises a lithium salt selected from the group consisting of LiPF ₆ , LiBF ₄ , LiBOB, LiDFOB, LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , one or more of LiC(SO ₂ CF ₃ ) ₃ and LiN(SO ₂ F) ₂ .

And a lithium ion battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte solution, wherein the electrolyte solution is the lithium ion battery non-aqueous electrolyte solution described above.

Preferably, the positive electrode comprises a positive active material, and the active material of the positive electrode is LiNi _x Co _y Mn _z L _(1-xyz) O ₂ , LiCo _x' L _(1-x') O ₂ , LiNi _x" L At least one of ' _{y '} Mn _(2-x"-y') O ₄ , Li _{z '} MPO ₄ , wherein L is in Al, Sr, Mg, Ti, Ca, Zr, Zn, Si or Fe At least one, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, 0 < x + y + z ≤ 1, 0 <x' ≤ 1, 0.3 ≤ x" ≤ 0.6, 0.01 ≤ y' ≤ 0.2, L' is at least one of Co, Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, Fe; 0.5 ≤ z' ≤ 1, M is at least one of Fe, Mn, and Co .

The nonaqueous electrolyte of the lithium ion battery of the invention simultaneously contains the compound A and the compound B, which can effectively improve the high temperature storage performance and high temperature cycle performance of the battery, and the cycle performance, high temperature storage performance and low temperature of the lithium ion battery containing the nonaqueous electrolyte. The discharge performance is balanced.

The lithium ion battery provided by the present invention has both high temperature performance (including high temperature cycle performance and high temperature storage performance) and low temperature discharge performance because it contains the above nonaqueous electrolyte.

detailed description

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clear, the present invention will be further described in detail below with reference to the embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

An embodiment of the present invention provides a nonaqueous electrolyte for a lithium ion battery, comprising the compound A represented by the following structural formula I and the compound B represented by the structural formula II,

In the formula I, R ₁ is a C1-C4 hydrocarbon group, and m is 1 or 2;

In the formula II, R ₂ , R ₃ , R ₄ , R ₅ , R ₆ and R ₇ are each independently selected from a hydrogen atom, a halogen atom or a C1-C5 group.

In the examples of the present invention, C1-C4 means that the number of carbon atoms is 1-4, and similarly, C1-C5 means that the number of carbon atoms is 1-5.

Ⅰ the structural formula, it is preferred, of R ₁ as a methyl, ethyl, propyl, isopropyl, butyl, allyl, propenyl, trifluoromethyl, trifluoroethyl of . Particularly preferably, the compound A is selected from the group consisting of trimethylsilyl methanesulfonate, trimethylsilylethanesulfonate, trimethylsilylpropanesulfonate, trimethylsilylisopropylsulfonic acid Ester, trimethylsilyl butyl sulfonate, trimethylsilyl propargyl sulfonate, trimethylsilyl propyl sulfonate, trimethylsilyl trifluoromethane sulfonate, top three One or more of a silyl trifluoroethyl sulfonate and a triethylsilyl methanesulfonate.

Further preferably, the compound A has a mass percentage of 0.1 to 2% based on 100% by mass of the total mass of the lithium ion battery nonaqueous electrolyte. When the mass percentage of the compound A is less than 0.1% At the time, the film forming effect on the negative electrode is lowered, which is disadvantageous for improving the low-temperature discharge performance of the non-aqueous electrolyte lithium ion battery. When the mass percentage of the compound A is more than 2%, the passivation film formed on the surface of the negative electrode of the lithium ion battery is too thick, which may lower the high temperature performance of the battery; and the excessive content of the compound A may cause nonaqueous electrolysis. The liquid is easily discolored, which in turn affects the stability of the non-aqueous electrolyte.

It should be understood that when the lithium ion battery non-aqueous electrolyte contains one of the above substances, the content is the content of the one substance; when the lithium ion battery non-aqueous electrolyte contains a plurality of the above substances; The content is the sum of the contents of various substances.

The nonaqueous electrolyte of the lithium ion battery provided by the embodiment of the present invention contains the compound A as shown in the structural formula I, which is reductively decomposed in preference to the solvent in the formation of the lithium ion battery, and forms the SEI film in the negative electrode. The compound A has a low impedance of the SEI film formed on the negative electrode, which not only enables the lithium ion battery to obtain excellent low temperature discharge performance, but also imparts excellent normal temperature cycle performance to the lithium ion battery, but has high temperature circulation and high temperature for the lithium ion battery. The storage performance is not improved, and the high-temperature cycle and high-temperature storage performance of the lithium ion battery are poor.

In the embodiment of the present invention, in the lithium ion battery non-aqueous electrolyte solution, the compound B represented by the above formula II is added to the compound A represented by the above formula I. Compound A and Compound B can be decomposed together on the surface of the negative electrode to form a composite passivation film which is advantageous for the conduction of lithium ions and stably exists on the surface of the negative electrode, thereby improving the cycle and high-temperature storage performance of the lithium ion battery. At the same time, the impedance of the passivation film is small, which can give the lithium ion battery excellent power performance, so that the lithium ion battery has excellent comprehensive performance.

In the formula II, preferably, the C1-C5 group is selected from a C1-C5 hydrocarbon group, a halogenated hydrocarbon group, an oxygen-containing hydrocarbon group, a silicon-containing hydrocarbon group, and a cyano-substituted hydrocarbon group. Further preferably, the R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , and R ₇ are each independently selected from a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, and a trimethyl group. One of a silyloxy group, a cyano group or a trifluoromethyl group.

Particularly preferably, the compound B is selected from one or more of the compounds 1-9 shown by the following structures.

The above preferred specific compounds are better able to complex with the compound A to improve the cycle and high temperature storage properties of the lithium ion battery.

The synthesis method of the compound B represented by the above structural formula V is conventional. For example, the compound B may be a polyol (such as erythritol, xylitol, etc.) and a carbonate (such as dimethyl carbonate, diethyl carbonate or ethylene carbonate). Etc.) The transesterification reaction takes place under the action of a basic catalyst, and is obtained by recrystallization or column chromatography. An example of its synthetic route is as follows:

The preparation of the fluorine-containing compound in the compound B is carried out by fluorinating a mixture of the corresponding carbonate and F ₂ /N ₂ , followed by purification by recrystallization or column chromatography. An example of its synthetic route is as follows:

The preparation of the cyano group-containing compound in the compound B is carried out by reacting the corresponding carbonate with a sulfonyl chloride, reacting with NaCN or KCN, and purifying by recrystallization or column chromatography. An example of its synthetic route is as follows:

The preparation of the trimethylsiloxy compound in the compound B is carried out by subjecting the corresponding hydroxycarbonate to a substitution reaction with a nitrogen silane, followed by recrystallization or column chromatography. An example of its synthetic route is as follows:

Further preferably, the compound B has a mass percentage of 0.1 to 5% based on 100% of the total mass of the lithium ion battery nonaqueous electrolyte. When the content of the compound B is less than 0.1%, it is disadvantageous for forming a passivation film on the negative electrode, and the effect of improving the cycle performance of the lithium ion battery is lowered; When the content of the compound B is more than 5%, the film formation at the negative electrode interface of the lithium ion battery is thick, and the battery resistance is increased. The nonaqueous lithium ion battery electrolyte of the embodiment of the present invention can make the lithium ion battery have excellent cycle performance, high temperature storage performance and power performance by the combination of the compound A and the compound B.

It should be understood that when the lithium ion battery non-aqueous electrolyte contains one of the above substances, the content is the content of the one substance; when the lithium ion battery non-aqueous electrolyte contains a plurality of the above substances; The content is the sum of the contents of various substances.

In addition to the above embodiments, preferably, the lithium ion non-aqueous electrolyte further includes at least one of an unsaturated cyclic carbonate compound, a fluorinated cyclic carbonate compound, and a sultone compound. .

The unsaturated cyclic carbonate compound includes at least one of vinylene carbonate (VC) and ethylene carbonate (VEC). The fluorinated cyclic carbonate compound includes fluoroethylene carbonate (FEC). The sultone compound is at least one selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone (BS), and 1,3-propene sultone (PST). Kind. The content of the unsaturated cyclic carbonate compound is from 0.1 to 5% based on 100% by mass of the total mass of the nonaqueous electrolyte of the lithium ion battery.

The content of the fluorinated cyclic carbonate compound is 0.1 to 30% based on 100% of the total mass of the nonaqueous electrolyte of the lithium ion battery.

The sulfonate lactone compound has a mass percentage of 0.1 to 5% based on 100% by mass of the total mass of the lithium ion battery nonaqueous electrolyte.

Of course, it should be understood that the lithium ion nonaqueous electrolytes of the above three cases may be combined with each other to form a new embodiment. That is, the lithium ion non-aqueous electrolyte solution may contain at least one of a fluorinated cyclic carbonate compound and/or a sulfonic acid, in addition to at least one of the unsaturated cyclic carbonate-based compounds. At least one of the lactone compounds. The lithium ion nonaqueous electrolytic solution may contain at least one of unsaturated cyclic carbonate compounds and/or sulfonic acid, in addition to at least one of fluorinated cyclic carbonate compounds. At least one of the lactone compounds. The lithium ion nonaqueous electrolyte may further contain unsaturated on the basis of at least one of a sultone compound At least one of the cyclic carbonate compounds and/or at least one of the fluorocyclic carbonate compounds. The lithium ion non-aqueous electrolyte solution may contain at least one of an unsaturated cyclic carbonate compound and at least one of a fluorinated cyclic carbonate compound, and further contains a sultone compound. At least one of them.

In the embodiment of the present invention, the non-aqueous electrolyte of the lithium ion battery contains the compound A and the compound B at the same time, which can effectively improve the high-temperature storage performance and high-temperature cycle performance of the battery, and the cycle performance and high-temperature storage performance of the lithium ion battery containing the non-aqueous electrolyte. The low-temperature discharge performance can be taken into consideration.

As is well known to those skilled in the art, the main components in the nonaqueous electrolyte of lithium ion batteries are nonaqueous organic solvents, lithium salts and additives. In the present invention, the compound A and the compound B are additives. The content of the non-aqueous organic solvent and the lithium salt is conventional, and the content thereof can be specifically adjusted after the content of the additive including the compound A and the compound B is determined.

Preferably, the lithium salt is selected from _{LiPF 6, LiBF 4, LiBOB,} LiDFOB, LiN (SO 2 CF 3) 2, LiN (SO 2 C 2 F 5) 2, LiC (SO 2 CF 3) 3, LiN ( One or more of SO ₂ F) ₂ . In the nonaqueous electrolyte of the lithium ion battery, the content of the lithium salt is 0.1 to 15%.

Preferably, the non-aqueous electrolyte of the lithium ion battery comprises a non-aqueous organic solvent, and the non-aqueous organic solvent is ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and carbonic acid. At least one of ethyl ester and methyl propyl carbonate. More preferably, the non-aqueous organic solvent is a combination of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate.

In addition, the embodiment of the present invention further provides a lithium ion battery, comprising: a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein the electrolyte is a lithium ion battery Electrolyte.

Preferably, the positive electrode comprises a positive active material, and the active material of the positive electrode is LiNi _x Co _y Mn _z L _(1-xyz) O ₂ , LiCo _x' L _(1-x') O ₂ , LiNi _x" L At least one of ' _{y '} Mn _(2-x"-y') O ₄ , Li _{z '} MPO ₄ , wherein L is in Al, Sr, Mg, Ti, Ca, Zr, Zn, Si or Fe At least one, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, 0 < x + y + z ≤ 1, 0 <x' ≤ 1, 0.3 ≤ x" ≤ 0.6, 0.01 ≤ y' ≤ 0.2, L' is at least one of Co, Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, Fe; 0.5 ≤ z' ≤ 1, M is at least one of Fe, Mn, and Co .

In the embodiment of the present invention, the positive electrode, the negative electrode, and the separator are not specifically limited, and a positive electrode, a negative electrode, and a separator which are conventional in the art may be used.

The lithium ion battery provided by the embodiment of the present invention has both high temperature performance (including high temperature cycle performance and high temperature storage performance) and low temperature discharge performance because it contains the above nonaqueous electrolyte.

The following description will be made in conjunction with specific embodiments.

Examples 1-17, Comparative Examples 1-4

A 4.2V LiNi _0.5 Co _0.2 Mn _0.3 O ₂ /artificial graphite battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein the electrolyte is non-aqueous The electrolyte solution and the components of Examples 1-17 and Comparative Examples 1-4 and their contents are shown in Table 1 based on 100% by weight of the total weight of the non-aqueous electrolyte.

Examples 18-22, Comparative Example 5

A 4.4V LiCoO ₂ /artificial graphite battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein the electrolyte is a non-aqueous electrolyte, and The total weight of the non-aqueous electrolyte was 100%, and the components and their contents in Examples 18-22 and Comparative Example 5 are shown in Table 2.

The performance test of the LiNi _0.5 Co _0.2 Mn _0.3 O ₂ /artificial graphite battery of Examples 1-17 and Comparative Examples 1-4, and the LiCoO ₂ /artificial graphite batteries of Examples 18-22 and Comparative Example 5 were tested. The indicators and test methods are as follows:

(1) High-temperature cycle performance, which is demonstrated by testing the capacity retention rate of the 45 °C 1C cycle for 500 weeks. The specific method is: at 45 ° C, the formed battery is charged to 4.2 V with a constant current of 1 C (Examples 1-14). Comparative Example 1-4) / 4.4 V (Examples 15-19, Comparative Example 5), the off current was 0.01 C, and then discharged to 3.0 V with a constant current of 1 C. After 500 cycles of charging/discharging, the capacity retention after the 500th cycle was calculated to evaluate the high temperature cycle performance.

The formula for calculating the capacity retention rate of the 150°C 1C cycle for 500 times is as follows:

The 500th cycle capacity retention ratio (%) = (500th cycle discharge capacity / first cycle discharge capacity) × 100%.

(2) Low-temperature discharge performance, expressed by -20 °C 0.5C discharge efficiency, the specific method is: at 25 ° C, the formed battery is charged to 4.2V with 1C constant current and constant voltage (Examples 1-17, Comparative Example) 1-4) / 4.4 V (Examples 18-22, Comparative Example 5), the off current was 0.01 C, and then discharged to 3.0 V with a constant current of 1 C, and the discharge capacity was recorded. Then 1C constant current constant voltage charging to 4.2V (Examples 1-17, Comparative Examples 1-4) / 4.4V (Examples 18-22, Comparative Example 5), the current is 0.01C, and then the battery is placed - After leaving for 12 hours in an environment of 20 ° C, a constant current of 0.5 C was discharged to 2.5 V, and the discharge capacity was recorded.

The calculation formula of -20 °C0.5C discharge efficiency is as follows:

Low-temperature discharge efficiency (%) at -20 ° C = 0.5 C discharge capacity (-20 ° C) / 1 C discharge capacity (25 ° C).

(3) Test method for capacity retention rate, capacity recovery rate, and thickness expansion ratio after storage for 30 days at 60 ° C: The battery after the formation was charged to 4.2 V at a normal temperature with a constant current of 1 C (Examples 1-17, Comparative Example 1-4) / 4.4 V (Examples 18-22, Comparative Example 5), the off current was 0.01 C, and then discharged with a constant current of 1 C to 3.0 V, and the initial discharge capacity of the battery was measured, and then a constant current of 1 C was used. Charging to 4.2V (Examples 1-17, Comparative Examples 1-4) / 4.4V (Examples 18-22, Comparative Example 5), the cut-off current was 0.01 C, the initial thickness of the battery was measured, and then the battery was at 60 ° C. After storage for 30 days, the thickness of the battery was measured, and then discharged to 3.0 V with a constant current of 1 C. The holding capacity of the battery was measured, and then charged to 4.2 V with a constant current constant voltage of 1 C (Examples 1-17, Comparative Examples 1-4)/ 4.4 V (Examples 18-22, Comparative Example 5), the off current was 0.01 C, and then discharged to 3.0 V with a constant current of 1 C, and the recovery capacity was measured. The formula for calculating the capacity retention rate and capacity recovery rate is as follows:

Battery capacity retention rate (%) = retention capacity / initial capacity × 100%;

Battery capacity recovery rate (%) = recovery capacity / initial capacity × 100%;

Battery thickness expansion ratio (%) = (thickness after 30 days - initial thickness) / initial thickness × 100%.

The test results of Examples 1-17 and Comparative Examples 1-4 are shown in Table 1 below, and the test results of Examples 18-22 and Comparative Example 5 are shown in Table 2 below.

Table 1

Table 2

As is well known to those skilled in the art, in the examples and comparative examples of Tables 1 and 2 above, in addition to the substances listed, conventional solvents and lithium salts are also included, and no special description is given in the present invention. Further, the weight of the electrolytic solution other than the above-mentioned substances is the content of the solvent and the lithium salt.

In combination with Table 1, Comparative Examples 1-17 and Comparative Examples 1-4, the lithium ion nonaqueous electrolyte of Example 1-17 contained both Compound A and Compound B, and Comparative Example 1-4 was only used in the lithium ion nonaqueous electrolyte. Contains Compound A. The results show that the lithium ion non-aqueous electrolyte containing Compound A alone has better low-temperature discharge performance, but the high-temperature cycle performance and high-temperature storage performance of the lithium ion battery are poor. When compound A and compound B are used at the same time, since the composite passivation film is formed on the surface of the negative electrode, the obtained lithium ion battery can effectively improve the high temperature cycle performance and the high temperature storage performance without affecting the low temperature cycle performance.

In combination with Table 1, Comparative Examples 1, 13, and 14, Comparative Examples 1, 3, Comparative Example 1 lithium ion non-aqueous electrolyte was only added with Compound A, and Comparative Example 3 lithium ion non-aqueous electrolyte was added with Compound A and VC. In the first embodiment of the present invention, the lithium ion nonaqueous electrolyte was added with the compound A and the compound B, and the lithium ion nonaqueous electrolyte of the example 13 was added with the compound A, the compound B and the VC, and the lithium ion nonaqueous electrolyte of the example 14 was added with the compound. A, compound B and lithium bis(fluorosulfonyl)imide. The results show that the addition of VC alone on the basis of Compound A has no significant improvement effect on the high temperature cycle performance and high temperature storage performance of the lithium ion battery. However, the addition of VC or bis(fluorosulfonyl)imide lithium after the combination of Compound A and Compound B not only does not lower the low-temperature discharge performance, high-temperature cycle performance and high-temperature storage performance of the lithium ion battery, but also slightly improves the above properties.

Referring to Table 1, comparing Examples 1, 10-12, the number of carbon atoms in the structure of the compound A in the lithium ion non-aqueous electrolyte is increased from 1 to 4, and the high-temperature storage performance and high-temperature cycle performance are improved, and the low-temperature discharge performance is changed. Poor trend. This is mainly due to the fact that as the number of carbon atoms increases, the passivation film formed by compound A becomes denser, and the cycle performance and storage performance are improved. However, the composition of the SEI film which is not conducive to lithium ion conduction increases, resulting in an increase in internal resistance of the battery and deterioration. Low temperature performance.

In combination with Table 2, Comparative Examples 18-22 and Comparative Example 5, Example 18-22, the lithium ion nonaqueous electrolytic solution contained both Compound A and Compound B, and Comparative Example 5 contained only the Compound A in the lithium ion nonaqueous electrolytic solution. The results show that the lithium ion non-aqueous electrolyte containing Compound A alone has better low-temperature discharge performance, but the high-temperature cycle performance and high-temperature storage performance of the lithium ion battery are poor. When compound A and compound B are used at the same time, since the composite passivation film is formed on the surface of the negative electrode, the obtained lithium ion battery can effectively improve the high temperature cycle performance and the high temperature storage performance without affecting the low temperature cycle performance.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. Within the scope.

Claims (10)

1. A nonaqueous electrolyte for a lithium ion battery, comprising: a compound A represented by the following structural formula I and a compound B represented by the formula II,

   

   In the formula I, R ₁ is a C1-C4 hydrocarbon group, and m is 1 or 2;

   In the formula II, R ₂ , R ₃ , R ₄ , R ₅ , R ₆ and R ₇ are each independently selected from a hydrogen atom, a halogen atom or a C1-C5 group.
2. A nonaqueous electrolyte for a lithium ion battery according to claim 1, wherein said C1-C5 group is selected from the group consisting of a C1-C5 hydrocarbon group, a halogenated hydrocarbon group, an oxygen-containing hydrocarbon group, a silicon-containing hydrocarbon group, and a cyano group. Hydrocarbyl group.
3. The nonaqueous electrolyte for a lithium ion battery according to claim 1, wherein said R ₂ , R ₃ , R ₄ , R ₅ , R ₆ and R ₇ are each independently selected from a hydrogen atom, a fluorine atom, and a One of a group, an ethyl group, a methoxy group, an ethoxy group, a trimethylsiloxy group, a cyano group or a trifluoromethyl group.
4. The nonaqueous electrolyte for a lithium ion battery according to claim 1, wherein the compound B is one or more selected from the group consisting of the compounds 1-9 shown below.

   
5. The nonaqueous electrolyte for a lithium ion battery according to claim 1, wherein the mass percentage of the compound B is 0.1 to 5 based on 100% of the total mass of the nonaqueous electrolyte of the lithium ion battery. %; the compound A has a mass percentage of 0.1 to 2%.
6. A nonaqueous electrolyte for a lithium ion battery according to any one of claims 1 to 5, wherein said R _{1 is} selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, allyl, and alkyne. One of a propyl group, a trifluoromethyl group, and a trifluoroethyl group.
7. The nonaqueous electrolyte for a lithium ion battery according to any one of claims 1 to 5, wherein the compound A is selected from the group consisting of trimethylsilyl methanesulfonate, trimethylsilylethanesulfonate, and three Methylsilyl propane sulfonate, trimethylsilyl isopropyl sulfonate, trimethylsilyl butyl sulfonate, trimethylsilyl propyl sulfonate, trimethylsilyl propargyl One or more of a sulfonate, trimethylsilyltrifluoromethanesulfonate, trimethylsilyltrifluoroethylsulfonate, and triethylsilylsulfonate.
8. The lithium ion battery nonaqueous electrolyte according to any one of claims 1 to 5, wherein the lithium ion nonaqueous electrolyte further comprises an unsaturated cyclic carbonate compound or a fluorinated cyclic carbonate compound. And at least one of the sultone compounds.
9. The lithium ion battery nonaqueous electrolyte according to any one of claims 1 to 5, wherein the lithium ion battery nonaqueous electrolyte comprises a lithium salt, and the lithium salt is selected from the group consisting of LiPF ₆ , LiBF ₄ , LiBOB, One or more of LiDFOB, LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiC(SO ₂ CF ₃ ) ₃ , and LiN(SO ₂ F) ₂ .
10. A lithium ion battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein the electrolyte is the lithium ion according to any one of claims 1-9 Battery non-aqueous electrolyte.