阅读说明：本技术 腈类化合物在制备高压电池体系用电解液中的应用 (Application of nitrile compound in preparation of electrolyte for high-voltage battery system ) 是由 杨勇 杨雪蕊 廖颖 张忠如 于 2020-05-09 设计创作，主要内容包括：本发明公开了腈类化合物在制备高压电池体系用电解液中的应用,该腈类化合物结构式为<Image he="351" wi="542" file="DDA0002484485690000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>其中n<Sub>1</Sub>、n<Sub>2</Sub>和n<Sub>3</Sub>分别为0-10的整数,但不同时为0,R<Sub>f</Sub>为含氟官能团。本发明中含F吸电子官能团的取代,可以协同腈基官能团,对正极界面层很好的修饰,进一步提高电池的高压稳定性；本发明中含F官能团的取代,能有效的提高腈类分子的还原电位,在石墨或者锂金属负极形成一层稳定的LiF-rich的界面层,进而改善腈类添加剂对负极的不兼容性,提高软包全电池整体的高压稳定性。(The invention discloses an application of nitrile compounds in preparing electrolyte for a high-voltage battery system, wherein the nitrile compounds have a structural formula Wherein n is 1 、n 2 And n 3 Are each an integer of from 0 to 10,but not simultaneously 0, R f Is a fluorine-containing functional group. The substitution of the F-containing electron-withdrawing functional group can cooperate with a nitrile functional group to well modify an anode interface layer, so that the high-voltage stability of the battery is further improved; the substitution of the F-containing functional group can effectively improve the reduction potential of nitrile molecules, and a stable LiF-rich interface layer is formed on a graphite or lithium metal negative electrode, so that the incompatibility of nitrile additives to the negative electrode is improved, and the overall high-voltage stability of the soft package full cell is improved.)

1. The application of the nitrile compound in preparing the electrolyte for the high-voltage battery system is characterized in that: the nitrile compound has the structural formulaWherein n is₁、n₂And n₃Are each an integer of 0 to 10, and n₁、n₂And n₃Not simultaneously 0, R_fIs a fluorine-containing functional group.

2. The use of claim 1, wherein: the R is_fIs fluorine, trifluoromethanesulfonyl, trifluoromethyl, trifluoroacetyl, pentafluoroethyl or trifluoroethyl.

3. The use of claim 1, wherein: n is₁、n₂And n₃Are respectively an integer of 2 to 10.

4. Use according to claim 3, characterized in that: n is₁、n₂And n₃Are respectively an integer of 2 to 6.

5. The use according to any one of claims 1 to 4, wherein: (CH) in the formula₂)_nIs not linear, and is full alkyl linear.

6. An electrolyte for a high-voltage battery system, characterized in that: contains nitrile compound, organic solvent and non-aqueous electrolyte lithium salt, the structural formula of said nitrile compound isWherein n is₁、n₂And n₃Are respectively asAn integer of 0 to 10, and n₁、n₂And n₃Not simultaneously 0, R_fIs a fluorine-containing functional group.

7. The electrolyte for a high voltage battery system according to claim 6, wherein: and Rf is fluorine, trifluoromethanesulfonyl, trifluoromethyl, trifluoroacetyl, pentafluoroethyl or trifluoroethyl.

8. The electrolyte for a high voltage battery system according to claim 6, wherein: n is₁、n₂And n₃Are respectively an integer of 2 to 10.

9. The electrolyte for a high voltage battery system according to claim 8, wherein: n is₁、n₂And n₃Are respectively an integer of 2 to 6.

10. The electrolyte for a high-voltage battery system according to any one of claims 6 to 9, wherein: (CH) in the formula₂)_n1、(CH₂)_n2And (CH)₂)_n3All contain no branch chain and are all alkyl straight chain.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to an application of nitrile compounds in preparation of electrolyte for a high-voltage battery system.

Background

Increasing the energy density, especially the volumetric energy density, of batteries is the focus of current research. There are two methods for increasing the volumetric energy density, one is to develop a positive electrode material with high capacity or high operating voltage; and secondly, optimizing the design structure of the battery, such as improving the compression density and the mass ratio of the anode and the cathode, or reducing the mass fraction of the inactive components. In fact, the compacted density and the optimized mass ratio of the active material, as well as the thickness of the membrane and the current collector, are close to their limits. In particular, reducing the thickness of the separator and current collector increases the energy density of lithium batteries at the expense of safety, which may be one of the causes of recent cellular phone explosions. Therefore, the most feasible method for achieving high energy density of lithium ion batteries is to increase the capacities of the cathode and the anode and to increase the operating voltage of LIBs. However, the decomposition voltage of the currently commercialized carbonate system is 4.3V, and when the decomposition voltage is higher than 4.3V, the electrolyte is decomposed seriously, and a serious gas generation phenomenon is accompanied, so that the service life of the battery is greatly reduced, and a potential safety hazard is caused. In order to further widen the operating voltage of the electrolyte, some nitrile and sulfone additives or solvents having strong oxidation resistance are widely popularized. But the sulfone and nitrile solvents are easy to form a loose interface layer with low ionic conductivity on a negative electrode layer, so that the graphite and lithium metal negative electrodes cannot be well compatible.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides the application of nitrile compounds in preparing electrolyte for a high-voltage battery system.

Another object of the present invention is to provide an electrolyte for a high voltage battery system.

The technical scheme of the invention is as follows:

the application of nitrile compound in preparing electrolyte for high-voltage battery system, the structural formula of the nitrile compound isWherein n is₁、n₂And n₃Are each an integer of 0 to 10, and n₁、n₂And n₃Not simultaneously 0, Rf is a fluorine-containing functional group.

The other technical scheme of the invention is as follows:

an electrolyte for high-voltage battery system contains nitrile compound, organic solvent and non-aqueous electrolyte lithium salt, the nitrile compound has the structural formula

Wherein n is₁、n₂And n₃Are each an integer of 0 to 10, and n₁、n₂And n₃Not simultaneously 0, R_fIs a fluorine-containing functional group.

In a preferred embodiment of the present invention, the organic solvent includes at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC), Ethylene Carbonate (EC), Propylene Carbonate (PC), and 4-fluoroethylene carbonate (FEC).

Further preferably, the organic solvent is at least one of dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate and 4-fluoroethylene carbonate.

In a preferred embodiment of the present invention, the non-aqueous electrolyte lithium salt includes lithium hexafluorophosphate (LiPF)₆) Lithium tetrafluoroborate (LiBF)₄) Lithium perchlorate (LiClO)₄) Lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) and lithium bis (sulfonyl fluoride) imide (LiFSI).

Further preferably, the nonaqueous electrolyte lithium salt is lithium hexafluorophosphate

In a preferred embodiment of the invention, the content of the nitrile functional additive compound in the electrolyte is 0.1-5 wt%.

More preferably, the content of the nitrile functional additive compound in the electrolyte is 0.5-3 wt%.

The invention has the beneficial effects that:

1. the substitution of the F-containing electron-withdrawing functional group can cooperate with a nitrile functional group to well modify an anode interface layer, so that the high-voltage stability of the battery is further improved;

2. the substitution of the F-containing functional group can effectively improve the reduction potential of nitrile molecules, and a stable LiF-rich interface layer is formed on a graphite or lithium metal negative electrode, so that the incompatibility of nitrile additives to the negative electrode is improved, and the overall high-voltage stability of the soft package full cell is improved.

Drawings

FIG. 1 is LiCoO according to the present invention in example 1, comparative example 1 and comparative example 2₂Comparative plot of the cycle capacity retention rate of Li battery. The test temperature is 30 ℃, the charge-discharge multiplying power is 1C, and the charge-discharge voltage range is as follows: 3.0V-4.6V.

Fig. 2 is a graph comparing the cycle capacity retention rates of graphite/Li batteries of example 1, comparative example 1 and comparative example 2 of the present invention. The test temperature is 30 ℃, the charge-discharge multiplying power is 1C, and the charge-discharge voltage range is as follows: 2.5V-0.05V.

FIG. 3 is LiCoO according to the present invention in example 1, comparative example 1 and comparative example 3₂Comparative plot of the cycle capacity retention rate of Li battery. The test temperature is 30 ℃, the charge-discharge multiplying power is 1C, and the charge-discharge voltage range is as follows: 3.0V-4.6V.

Detailed Description

In a preferred embodiment of the present invention, said R_fIs fluorine, trifluoromethanesulfonyl, trifluoromethyl, trifluoroacetyl, pentafluoroethyl or trifluoroethyl.

In a preferred embodiment of the present invention, said n₁、n₂And n₃Are respectively an integer of 2 to 10.

Further preferably, n is₁、n₂And n₃Are respectively an integer of 2 to 6.

In a preferred embodiment of the present invention, (CH) in the formula₂)_n1、(CH₂)_n2And (CH)₂)_n3All contain no branch chain and are all alkyl straight chain.

The technical solution of the present invention will be further illustrated and described below with reference to the accompanying drawings by means of specific embodiments.

The preparation of the nitrile compounds in the following examples is described with reference to Synthesis and Structure of fluoronitrile.