WO2018209752A1 - Lithium ion battery nonaqueous electrolyte and lithium ion battery - Google Patents

Abstract

A lithium ion battery nonaqueous electrolyte. The nonaqueous electrolyte comprises a substance A of a structural formula as shown in formula (I) and a substance B of a structural formula as shown in formula (II). In formula (I), R1 is a hydrocarbon group or a halogenated hydrocarbon group having one to four carbon atoms, wherein m is 1 or 2. In formula (II), R2, R3, and R4 are each independently selected from a hydrocarbon group or a halogenated hydrocarbon group having one to five carbon atoms and an unsaturated hydrocarbon group or an unsaturated halogenated hydrocarbon group having two to five carbon atoms, and at least one of R2, R3, and R4 is the unsaturated hydrocarbon group or the unsaturated halogenated hydrocarbon group. The nonaqueous electrolyte can form a composite passivation film at the positive and negative electrodes of lithium ion batteries through the synergistic action of the substance A and the substance B, thereby effectively improving high-temperature cycle performance, high-temperature storage performance, and low-temperature characteristics of lithium ion batteries.

Description

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

The invention belongs to the technical field of lithium ion battery electrolyte, and particularly relates to a lithium ion battery non-aqueous electrolyte and a lithium ion battery.

Background technique

With the rapid development of new energy fields, non-aqueous electrolyte lithium-ion batteries have shown great application prospects in power supply systems for new energy vehicles. Although these non-aqueous electrolyte batteries have been put into practical use, they have not been satisfactory in long-term use, especially in the case of a short life at a high temperature of 45 ° C, and a low-temperature discharge performance after the battery has been subjected to high-temperature storage. For power vehicles and energy storage systems, non-aqueous electrolyte lithium-ion batteries are required to work properly in cold regions, and more need to balance high and low temperature performance.

In the non-aqueous electrolyte lithium ion battery, the non-aqueous electrolyte is a key factor affecting the 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, commercial lithium-ion battery non-aqueous electrolytes use conventional film-forming additives such as vinylene carbonate (VC) to ensure excellent cycle performance of the battery through VC. In order to ensure the long life of the lithium ion battery, it is necessary to add a large amount of VC, but too high VC content will deteriorate the performance of the lithium ion battery, such as gas production during high temperature storage, resulting in battery swelling; and high content VC Will significantly increase the battery interface impedance, degrading the low temperature performance of the battery.

Chinese Patent Publication No. 1385919A discloses an electrolyte containing RSO ₃ Si(C _m H _2m+1 ) ₃ compound which can improve the low temperature discharge performance of the battery, but in the experiment we found that RSO ₃ Si was contained. Although the electrolyte of the (C _m H _2m+1 ) ₃ compound can improve the low-temperature discharge performance of the battery and lower the battery resistance, the high-temperature performance of the battery is not ideal, and therefore, it is not practical.

The Chinese Patent Application No. 201180037584.4 discloses an electrolyte solution containing an alkynyl phosphate compound, which is exposed on the crystal face of the graphite particles, and the graphite particles are bonded in parallel with each other. In combination, the electrolyte can be protected by the electrolyte, thereby increasing the battery capacity and ensuring a balance between battery power and capacity. This patent requires that the microscopic surface of the graphite particles and the electrolyte be simultaneously satisfied. If the orientation between the graphite particles is not satisfactory, the effect of improving the battery capacity of the phosphate compound electrolyte containing the alkynyl group cannot be achieved.

The application No. 00801010.2 discloses the electrolysis of a compound containing (R1a)P=(O)(OR2a)(OR3a) (wherein R1a, R2a, R3a represents an independent aliphatic hydrocarbon group having 7 to 12 carbon atoms) The liquid effectively controls a decrease in discharge capacity which occurs as the charge and discharge cycle progresses and a decrease in battery characteristics at the time of high temperature storage. However, it has been found through extensive experiments that although unsaturated phosphate esters can significantly improve the high temperature storage and high temperature cycle performance of the battery, unsaturated phosphate esters can seriously deteriorate the impedance and low temperature characteristics of the battery, especially the low temperature discharge performance after high temperature storage. This drawback will greatly limit its use in power batteries and energy storage systems.

Summary of the invention

The object of the present invention is to provide a non-aqueous electrolyte for a lithium ion battery, which aims to solve the present problem. There is a problem that the lithium ion battery electrolyte cannot simultaneously take care of high temperature cycle, storage characteristics, and low temperature characteristics.

Another object of the present invention is to provide a lithium ion battery comprising the above nonaqueous electrolyte of a lithium ion battery.

In order to achieve the above object, the present invention adopts the following technical solutions:

A lithium ion battery non-aqueous electrolyte comprising a substance A of the formula I and a substance B of the formula II:

Wherein, in the formula I, R _{1 is} selected from a hydrocarbon group having 1 to 4 carbon atoms or a halogenated hydrocarbon group, and m is 1 or 2;

In the formula II, R ₂ , R ₃ and R ₄ are each independently selected from a hydrocarbon group having 1 to 5 carbon atoms or a halogenated hydrocarbon group, an unsaturated hydrocarbon group having 2 to 5 carbon atoms or an unsaturated halogenated hydrocarbon group. And at least one of R ₂ , R ₃ , and R ₄ is an unsaturated hydrocarbon group or an unsaturated halogenated hydrocarbon group.

Preferably, the weight percentage of the substance A is from 0.1% to 2.0% based on 100% by total of the total weight of the lithium ion battery non-aqueous electrolyte.

Preferably, the weight percentage of the substance B is 0.1% to 2.0% based on 100% of the total weight of the nonaqueous electrolyte of the lithium ion battery.

Preferably, the hydrocarbon group in the R ₁ is selected from any one of a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an allyl group, a propargyl group, a trifluoromethyl group, and a trifluoroethyl group. .

Preferably, in the R ₂ , R ₃ , and R ₄ , the hydrocarbon group having 1 to 5 carbon atoms is selected from any one of a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group; The number of atoms having 2 to 5 unsaturated hydrocarbon groups is selected from the group consisting of vinyl, allyl, 3-butenyl, isobutenyl, 4-pentenyl, ethynyl, propargyl, 3-butynyl, 1-methyl Any one of -2 propynyl groups; the halogenated hydrocarbon group having 1 to 5 carbon atoms is selected from the group consisting of monofluoromethyl, difluoromethyl, trifluoromethyl, 2,2-difluoroethyl, Any of 2,2,2-trifluoroethyl, 3,3-difluoropropyl, 3,3,3-trifluoropropyl, hexafluoroisopropyl.

Preferably, the substance A is selected from the group consisting of trimethylsilyl methanesulfonate, trimethylsilylethanesulfonate, trimethylsilylpropanesulfonate, trimethylsilylisopropylsulfonate , trimethylsilyl butyl sulfonate, trimethylsilyl propyl sulfonate, trimethylsilyl propyl sulfonate, trimethylsilyl trifluoromethanesulfonate, trimethyl At least one of silyl trifluoroethyl sulfonate and triethylsilyl methanesulfonate.

Preferably, the substance B is selected from the group consisting of tripropargyl phosphate, dipropargyl methyl phosphate, dipropargylethyl phosphate, dipropargyl propyl phosphate, dipropargyl trifluoromethyl Phosphate ester, dipropargyl-2,2,2-trifluoroethyl phosphate, dipropargyl-3,3,3-trifluoropropyl phosphate, dipropargyl hexafluoroisopropyl phosphate , triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallylpropyl phosphate, diallyl trifluoromethyl phosphate, diallyl- At least one of 2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, and diallyl hexafluoroisopropyl phosphate.

Preferably, the nonaqueous electrolyte further includes at least one of an unsaturated cyclic carbonate, a fluorinated cyclic carbonate, and a cyclic sultone.

Preferably, the unsaturated carbonate comprises vinylene carbonate (VC), carbonate B At least one of ethylene carbonate (VEC).

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

Preferably, the cyclic sultone lactone 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 for isolating the separator of the positive electrode and the negative electrode, and an electrolyte solution, wherein the electrolyte solution is the lithium ion battery nonaqueous 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 lithium ion battery non-aqueous electrolyte provided by the invention comprises the substance A of the formula I and the substance B of the formula II, and the passivation film formed by the substance A has low impedance but insufficient thermal stability. Decomposition occurs under high temperature conditions, resulting in breakage of the passivation film, direct contact between the material and the electrolyte, promoting further decomposition of the lithium salt and solvent, increasing the interface impedance, thereby reducing the high temperature storage and cycle performance of the battery, especially the high temperature. Low temperature discharge performance after storage; substance B can form a dense passivation film on the surface of the material, but the membrane impedance is large, low temperature Poor discharge performance, while the high temperature storage performance of substance B can not meet the performance requirements of current batteries. Through the synergistic action of these two components, a dense and stable composite passivation film can be formed on the surface of the positive electrode and the negative electrode of the lithium ion battery, and the positive and negative electrodes can be well protected even at high temperatures. In addition, since the passivation film can be stably present on the surface of the positive electrode and the negative electrode, the lithium ion conduction effect is improved, and the cycle and high-temperature storage performance of the lithium ion battery are greatly improved, and the above-mentioned substance alone exists in the lithium ion battery electrolysis. The high and low temperature performance that cannot be achieved in the liquid can balance the characteristics, so that the lithium ion battery exhibits good high and low temperature performance at the same time. More importantly, the present invention, through the combination of the above two, produces an effect that is not a simple superposition of the conventional effects of the two, but produces a synergistic effect. As shown in the test data shown in Table 1, it can be seen that the phosphate ester B substance with poor low temperature performance after high temperature storage is used together with the silicon sulfonate A substance, and the low temperature performance of the electrolyte is not only better than when the substance B is used alone. Even better than using substance A alone. Similarly, the substance A, which is not ideal for high-temperature performance, is used together with the substance B. The high-temperature performance of the electrolyte is not only better than that of the substance A alone, but even better than when the substance B is used alone. That is, by using the two together, the effect of the two is not produced, but an unexpected synergistic effect with respect to the overall improvement in the use of the substance A and the substance B alone is produced.

The lithium ion battery provided by the present invention contains the nonaqueous electrolyte solution described above, and thus has high temperature cycle, storage performance and low temperature performance.

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 should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to Bright.

Embodiments of the present invention provide a lithium ion battery non-aqueous electrolyte, such as the substance A shown in Formula I and the substance B component shown in Formula II:

Wherein, in the formula I, R _{1 is} selected from a hydrocarbon group having 1 to 4 carbon atoms or a halogenated hydrocarbon group, and m is 1 or 2;

In the formula II, R ₂ , R ₃ and R ₄ are each independently selected from a hydrocarbon group having 1 to 5 carbon atoms or a halogenated hydrocarbon group, an unsaturated hydrocarbon group having 2 to 5 carbon atoms or an unsaturated halogenated hydrocarbon group. And at least one of R ₂ , R ₃ , and R ₄ is the unsaturated hydrocarbon group or the unsaturated halogenated hydrocarbon group.

Preferably, the hydrocarbon group represented by R ₁ in the above formula I may be methyl, ethyl, propyl, isopropyl, butyl, allyl, propenyl, trifluoromethyl or trifluoroethyl. Any of them.

Further preferably, the substance A represented by the formula I is selected from the group consisting of trimethylsilyl methanesulfonate, trimethylsilylethanesulfonate, trimethylsilylpropanesulfonate, trimethylsilyl Isopropyl sulfonate, trimethylsilyl butyl sulfonate, trimethylsilyl propyl sulfonate, trimethylsilyl propyl sulfonate, trimethylsilyl trifluoromethyl sulfonate At least one of an acid ester, trimethylsilyl trifluoroethyl sulfonate, and triethylsilyl methanesulfonate.

Preferably, the hydrocarbon group having 1 to 5 carbon atoms is selected from the group consisting of methyl, ethyl, propyl and iso Any one of a propyl group and a butyl group; the hydrocarbon group having 2 to 5 carbon atoms is selected from the group consisting of a vinyl group, an allyl group, a 3-butenyl group, an isobutenyl group, a 4-pentenyl group, an ethynyl group, Any one of a propargyl group, a 3-butynyl group, and a 1-methyl-2-propynyl group; and the halogenated hydrocarbon group having 1 to 5 carbon atoms is selected from the group consisting of a monofluoromethyl group and a difluoromethyl group. Trifluoromethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 3,3-difluoropropyl, 3,3,3-trifluoropropyl, hexafluoroisopropyl Any of them.

Further preferably, the substance B represented by the formula II may be selected from the group consisting of tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl propyl phosphate, and Propargyl trifluoromethyl phosphate, dipropargyl-2,2,2-trifluoroethyl phosphate, dipropargyl-3,3,3-trifluoropropyl phosphate, dipropargyl Hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallylethyl phosphate, diallylpropyl phosphate, diallyl trifluoromethyl phosphate Ester, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, diallyl hexafluoroisopropyl phosphate At least one of them.

Preferably, the substance A has a weight percentage of 0.1% to 2.0% based on 100% by weight of the total weight of the lithium ion battery non-aqueous electrolyte.

Preferably, the substance B has a weight percentage of 0.1% to 2.0% based on 100% of the total weight of the lithium ion battery non-aqueous electrolyte.

The nonaqueous electrolytic solution in the technical solution of the present invention includes at least one of an unsaturated carbonate, a fluorinated cyclic carbonate, and a cyclic sultone, in addition to the above two components.

Preferably, the unsaturated carbonate content is from 0.1 to 5% based on 100% by mass of the total mass of the lithium ion battery nonaqueous electrolyte. Further preferably, the unsaturated carbonate is carbon At least one of vinylene vinyl ester and ethylene carbonate.

Preferably, the fluorinated cyclic carbonate content is from 0.1 to 30% based on 100% of the total mass of the lithium ion battery nonaqueous electrolyte. Further preferably, the fluorocyclic carbonate is fluoroethylene carbonate.

Preferably, the cyclic sultone 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. Further preferably, the cyclic sultone is at least one of 1,3-propane sultone, 1,4-butane sultone, and 1,3-propene sultone.

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 . 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 the present invention, by the synergistic action of the substance A represented by the formula I and the substance B of the formula II, not only a uniform and dense composite passivation film is formed on the surface of the lithium ion negative electrode, but also a dense composite blunt is formed on the surface of the positive electrode. The film can not only form a good protection mechanism of the positive and negative electrodes under normal conditions, but also protect the positive and negative electrodes of the lithium ion battery even under high temperature conditions, since the formed passivation film belongs to the composite passivation film. And the composite passivation film can stably exist on the surface of the positive electrode and the negative electrode of the lithium ion battery, and the lithium is greatly improved. The conduction effect of ions. In addition, due to the small impedance of the formed composite passivation film, the cycle and high-temperature storage performance of the lithium ion battery can be greatly improved, and the high-low temperature performance which cannot be achieved when the above two substances are separately present in the lithium ion battery electrolyte is achieved. The lithium ion battery is made to exhibit good high and low temperature performance.

In the premise of the above lithium ion non-aqueous electrolyte of the present invention, an embodiment of the present invention further provides a lithium ion battery.

In one embodiment, the lithium ion battery includes a positive electrode, a negative electrode, a separator for isolating the positive electrode and the negative electrode, and an electrolyte, and the electrolyte is the lithium ion battery non-aqueous electrolyte described above.

Specifically, the positive electrode includes a positive electrode 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 active material of the negative electrode is selected from the group consisting of artificial graphite and natural graphite. Of course, it is not limited to the two listed.

The separator is a conventional separator in the field of lithium ion batteries, and thus the present invention is not required to be further limited.

The lithium ion battery provided by the embodiment of the invention has better high temperature cycle performance, high temperature storage performance and low temperature performance because it contains the above nonaqueous electrolyte.

In order to better illustrate the technical solutions of the present invention, the following description will be made in conjunction with specific embodiments.

It should be noted that, in order to control a single variable, an embodiment of the present invention uses a 4.2V LiNi _0.5 Co _0.2 Mn _0.3 O ₂ /artificial graphite battery as a test battery. Of course, the non-aqueous electrolyte of the present invention is not only applicable to 4.2V LiNi _0.5 Co _0.2 Mn _0.3 O ₂ / artificial graphite battery.

Example 1

One kind of 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 is provided, and the battery electrolyte between the positive electrode and the negative electrode, wherein the electrolyte is The non-aqueous electrolyte, and including the substance A and the substance B, containing the substance A and the substance B in the weight percentage shown in Example 1 of Table 1, based on 100% by weight of the total weight of the non-aqueous electrolyte.

Example 2

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 electrolytic solution, and including the substance A and the substance B, contained the substance A and the substance B in the weight percentage shown in Example 2 of Table 1 based on 100% by weight of the total weight of the non-aqueous electrolyte.

Example 3

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 electrolytic solution, and including the substance A and the substance B, contained the substance A and the substance B in the weight percentage shown in Example 3 of Table 1 based on 100% by weight of the total weight of the non-aqueous electrolyte.

Example 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 electrolytic solution, and including the substance A and the substance B, contained the substance A and the substance B in a weight percentage shown in Example 4 of Table 1 based on 100% by weight of the total weight of the non-aqueous electrolyte.

Example 5

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, and including the substance A and the substance B, contained the substance A and the substance B in the weight percentage shown in Example 5 of Table 1 based on 100% by weight of the total weight of the non-aqueous electrolyte.

Example 6

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 electrolytic solution, and including the substance A and the substance B, contained the substance A and the substance B in a weight percentage shown in Example 6 of Table 1 based on 100% by weight of the total weight of the non-aqueous electrolyte.

Example 7

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, and including the substance A and the substance B, contained the substance A and the substance B in a weight percentage shown in Example 7 of Table 1 based on 100% by weight of the total weight of the non-aqueous electrolyte.

Example 8

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 electrolytic solution, and including the substance A and the substance B, contained the substance A and the substance B in a weight percentage shown in Example 8 of Table 1 based on 100% by weight of the total weight of the non-aqueous electrolyte.

Example 9

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 electrolytic solution, and including the substance A and the substance B, contained the substance A and the substance B in the weight percentage shown in Example 9 of Table 1 based on 100% by weight of the total weight of the non-aqueous electrolyte.

Example 10

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 electrolytic solution, and including the substance A and the substance B, contained the substance A and the substance B in a weight percentage shown in Example 10 of Table 1 based on 100% by weight of the total weight of the non-aqueous electrolyte.

Example 11

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, and including the substance A and the substance B, contained the substance A and the substance B in a weight percentage shown in Example 11 of Table 1 based on 100% by weight of the total weight of the non-aqueous electrolyte.

Example 12

One kind of 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 non-aqueous electrolyte The electrolytic solution, and including the substance A and the substance B, contained the substance A and the substance B in the weight percentage shown in Example 12 of Table 1 based on 100% by weight of the total weight of the non-aqueous electrolyte.

Example 13

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, and including the substance A and the substance B, contained the substance A and the substance B in the weight percentage shown in Example 13 of Table 1 based on 100% by weight of the total weight of the non-aqueous electrolyte.

Example 14

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, and including the substance A and the substance B, contained the substance A and the substance B in the weight percentage shown in Example 14 of Table 1 based on 100% by weight of the total weight of the non-aqueous electrolyte.

Example 15

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 electrolytic solution, and including the substance A and the substance B, contained the substance A and the substance B in the weight percentage shown in Example 15 of Table 1 based on 100% by weight of the total weight of the non-aqueous electrolyte.

Comparative example 1

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, and including the substance A, containing the substance A in the weight percentage shown in the first aspect of Table 1, based on 100% by weight of the total weight of the non-aqueous electrolyte.

Comparative example 2

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, and including the substance A, containing the substance A in the weight percentage shown in the comparative example 2 of Table 1, based on 100% of the total weight of the non-aqueous electrolyte.

Comparative example 3

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, and including the substance A, contained the substance A in the weight percentage shown in Comparative Example 3 of Table 1, based on 100% by weight of the total weight of the non-aqueous electrolyte.

Comparative example 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 electrolytic solution, and including the substance A, contained the substance A in the weight percentage shown in Comparative Example 4 of Table 1, based on 100% by weight of the total weight of the non-aqueous electrolyte.

Comparative example 5

One kind of 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 non-aqueous electrolyte The electrolyte, and including the substance B, contained the substance B in the weight percentage shown in Comparative Example 5 of Table 1, based on 100% by weight of the total weight of the non-aqueous electrolyte.

Comparative example 6

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, and including substance B, contained B in the weight percentage shown in Comparative Example 6, Table 1, based on 100% by weight of the total weight of the non-aqueous electrolyte.

Comparative example 7

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, and including the substance B, contained the substance B in the weight percentage shown in Comparative Example 7, Table 1, based on 100% by weight of the total weight of the non-aqueous electrolyte.

The 4.2V LiNi _0.5 Co _0.2 Mn _0.3 O ₂ / artificial graphite batteries of Examples 1-13 and 1-7 of the present invention were tested for performance. The relevant test indexes and test methods are as follows:

(1) High-temperature cycle performance, testing capacity retention at 500 °C for 1 cycle at 45 °C. The specific method is as follows: at 45 ° C, the formed battery is charged to 4.2 V with a constant current of 1 C, the off current is 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) Capacity retention rate, capacity recovery rate, and thickness expansion ratio after storage for 30 days at 60 °C. The specific test method is as follows: the battery after the formation is charged to 4.2V at a normal temperature with a constant current of 1C, the current is 0.01C, and then discharged with a constant current of 1C to 3.0V, and the initial discharge capacity of the battery is measured, and then the constant discharge capacity is used. The current is charged to 4.4V, the current is 0.01C, the initial thickness of the battery is measured, and then the battery is stored at 60 ° C for 30 days, the thickness of the battery is measured, and then discharged at a constant current of 1 C to 3.0 V to measure the holding capacity of the battery. Then, the battery was charged to 4.2 V with a constant current of 1 C, the 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%.

(3) The low-temperature discharge performance after high-temperature storage is reflected by the -20 °C0.5C discharge efficiency after high-temperature storage. The specific method is as follows: at 25 ° C, the battery after storage at 60 ° C for 30 days 1C constant current and constant voltage were charged to 4.2V, the off current was 0.01C, and then discharged to 3.0V with a constant current of 1C, and the discharge capacity was recorded. Then 1C constant current constant voltage charging to 4.2V, the off current is 0.01C, and then the battery is placed in the environment of -20 ° C for 12h, 0.5C constant current discharge to 2.5V, recording discharge capacity.

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).

The test results are shown in Table 1 below.

Table 1

It can be seen from Table 1:

It can be seen from Comparative Examples 1-4 that the addition of the substance A alone has insufficient performance in high-temperature storage and high-temperature cycle performance of the battery, and low-temperature discharge performance after storage, because the film formed by the substance A at high temperature cannot effectively protect the positive and negative electrodes. Surface, performance after storage is significantly reduced.

It can be seen from Comparative Examples 5-7 that the addition of Substance B alone can improve the high temperature storage and cycle performance of the battery, but the low temperature discharge performance after storage of the battery is poor, mainly because the passivation film can effectively protect the electrode surface, but is not conducive to lithium. The conduction of ions has a large interface impedance.

It can be seen from Examples 1 to 15 that when the substance A and the substance B are used at the same time, since both of them can form an excellent composite passivation film to protect the positive and negative electrodes, it is also possible to obtain excellent battery high-temperature storage and high-temperature cycle performance. Ensure good low temperature discharge performance after battery storage. Further, since the substance B having a low-temperature property is not added to the substance A having a low-temperature property, the overall low-temperature performance is lowered as compared with the case where the substance A is used alone, but an improvement is unexpectedly caused. On the other hand, the addition of the substance A having a high temperature performance to the substance B having a high temperature performance does not result in a decrease in the overall high temperature performance as compared with the case of using the substance B alone, but an increase in the intention is not obtained. The combination of the two produced an unexpected synergistic effect.

At the same time, it can be seen that as the number of carbon atoms in the substance A increases from 1 to 4, the high-temperature storage and cycle performance becomes better, and the low-temperature discharge performance tends to be worse, mainly due to carbon. As the number of atoms increases, the passivation film formed is denser, and the cycle and storage properties are improved. However, the composition of the SEI film which is disadvantageous for lithium ion conduction increases, resulting in an increase in internal resistance of the battery and deterioration of low temperature performance. The more unsaturated bonds in the substance B, the better the high temperature performance of the battery, but the interface resistance is increased and the low temperature performance is deteriorated. Only when the substances A and B are validated and combined can the battery be considered for both high and low temperature performance.

From the data of Examples 1 to 5, 7 to 8, and 10 to 15, it can be seen that when the content of the substance A and the substance B is in the range of 0.1% to 2% with respect to the total weight of the nonaqueous electrolyte of the lithium ion battery, the battery Excellent cycle performance, high temperature storage performance, and low temperature discharge performance after storage. In Examples 6 and 9, when the content of the substance A or B reached 2%, the decrease in the low-temperature discharge performance was remarkable. Therefore, in the technical solution of the present invention, the content of the substance A or the substance B is in the range of 0.1% to 2.0%.

The addition of trimethylsilyl methanesulfonate and tripropargyl phosphate to other additive combinations can further improve the high temperature cycle, high temperature storage and low temperature discharge performance of the battery.

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, characterized in that the nonaqueous electrolyte comprises a substance A of the formula I and a substance B of the formula II:

   

   Wherein, in the formula I, R _{1 is} selected from a hydrocarbon group having 1 to 4 carbon atoms or a halogenated hydrocarbon group, and m is 1 or 2;

   In the formula II, R ₂ , R ₃ and R ₄ are each independently selected from a hydrocarbon group having 1 to 5 carbon atoms or a halogenated hydrocarbon group, an unsaturated hydrocarbon group having 2 to 5 carbon atoms or an unsaturated halogenated hydrocarbon group. And at least one of R ₂ , R ₃ and R ₄ is the unsaturated hydrocarbon group or the unsaturated halogenated hydrocarbon group.
2. The nonaqueous electrolyte for a lithium ion battery according to claim 1, wherein the weight percentage of the substance A is 0.1% by weight based on 100% of the total weight of the nonaqueous electrolyte of the lithium ion battery. 2.0%.
3. The nonaqueous electrolyte for a lithium ion battery according to claim 1, wherein the weight percentage of the substance B is 0.1% by weight based on 100% of the total weight of the nonaqueous electrolyte of the lithium ion battery. 2.0%.
4. A nonaqueous electrolyte for a lithium ion battery according to claim 1, wherein said hydrocarbon group in said R ₁ is selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, allyl, and propargyl Any one of a group, a trifluoromethyl group, and a trifluoroethyl group.
5. The nonaqueous electrolyte for a lithium ion battery according to claim 1, wherein in the R ₂ , R ₃ and R ₄ , the hydrocarbon group having 1 to 5 carbon atoms is selected from the group consisting of methyl, ethyl and propyl groups. Any one of isopropyl and butyl; the hydrocarbon group having 2 to 5 carbon atoms selected from the group consisting of vinyl, allyl, 3-butenyl, isobutenyl, 4-pentenyl, acetylene Any one of a group, a propargyl group, a 3-butynyl group, and a 1-methyl-2-propynyl group; and the halogenated hydrocarbon group having 1 to 5 carbon atoms is selected from the group consisting of a monofluoromethyl group and a difluoromethyl group. Base, trifluoromethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 3,3-difluoropropyl, 3,3,3-trifluoropropyl, hexafluoroiso Any of the propyl groups.
6. The nonaqueous electrolyte for a lithium ion battery according to any one of claims 1 to 2, wherein the substance A is selected from the group consisting of trimethylsilyl methanesulfonate and trimethylsilylethanesulfonate. Trimethylsilyl propane sulfonate, trimethylsilyl isopropyl sulfonate, trimethylsilyl butyl sulfonate, trimethylsilyl propyl sulfonate, trimethylsilyl propylene At least one of a sulfonate, trimethylsilyltrifluoromethanesulfonate, trimethylsilyltrifluoroethylsulfonate, and triethylsilylsulfonate.
7. The nonaqueous electrolyte for a lithium ion battery according to any one of claims 1 to 3, wherein the substance B is selected from the group consisting of tripropargyl phosphate, dipropargyl methyl phosphate, and dipropargyl B. Phosphate, dipropargyl propyl phosphate, dipropargyl trifluoromethyl phosphate, dipropargyl-2,2,2-trifluoroethyl phosphate, dipropargyl-3,3 , 3-trifluoropropyl phosphate, dipropargyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallylethyl phosphate, diallyl Propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate At least one of an ester and diallyl hexafluoroisopropyl phosphate.
8. The nonaqueous electrolyte for a lithium ion battery according to claim 1, wherein the nonaqueous electrolyte further comprises at least one of an unsaturated cyclic carbonate, a fluorinated cyclic carbonate, and a cyclic sultone. One.
9. The nonaqueous electrolyte for a lithium ion battery according to claim 8, wherein the unsaturated carbonate is at least one of vinylene carbonate and ethylene ethylene carbonate;

   The fluorocyclic carbonate is fluoroethylene carbonate;

   The cyclic sultone is at least one of 1,3-propane sultone, 1,4-butane sultone, and 1,3-propene sultone.
10. A lithium ion battery comprising a positive electrode, a negative electrode, a separator for isolating the positive electrode and the negative electrode, and an electrolyte, wherein the electrolyte is the lithium ion battery according to any one of claims 1-9 Non-aqueous electrolyte.