CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based on International Application No. PCT/CN2017/093308, filed on Jul. 18, 2017, which claims priority to Chinese Patent Application No. 201710540923.X, filed on Jul. 5, 2017, the contents of which are incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates to the field of energy storage materials, and particularly, to an electrolyte and an electrochemical device.

BACKGROUND

Lithium-ion batteries are widely used in electric vehicles and consumer electronic products due to their advantages of high energy density, high output power, long cycle life and small environmental pollution. The current demand on lithium-ion batteries still includes: high voltage, high power, long cycle life, long storage life and excellent safety performance.

Most of the current lithium-ion batteries apply an electrolyte system, in which lithium hexafluorophosphate is used as conductive lithium salt and a cyclic carbonate and/or a chain carbonate is used as solvent. However, the above electrolyte system still has many deficiencies. For example, the cycle performance and storage performance of the above electrolyte system need to be improved under a condition of high voltage and high temperature.

The present disclosure aims to overcome the said deficiencies.

SUMMARY

In order to solve the above problems, the inventor conducted intensive researches and found that using a multi-cyano six-membered N-heterocyclic compound and a cyclic carbonate compound together as additives of the electrolyte can effectively inactivate the surface of a positive electrode material, inhibit the positive electrode material to oxidize the electrolyte, and reduce gas production of the battery, while an anode SEI film can be formed to avoid a contact between the anode and the electrode, thereby effectively reducing side reactions. In this way, the cycle performance at high temperature and high voltage and the storage performance of the battery can be improved. The present application is completed based on the above concept.

One purpose of the present disclosure is to provide an electrolyte including an additive A and an additive B, the additive A is selected from a group consisting of multi-cyano six-membered N-heterocyclic compounds represented by Formula I-1, Formula I-2 and Formula I-3, and combinations thereof:

wherein R1, R2, R3and R4are each independently selected from a group consisting of hydrogen, halogen, substituted or unsubstituted C1-C12alkyl, substituted or unsubstituted C1-C12alkoxy, substituted or unsubstituted C1-C12amine group, substituted or unsubstituted C2-C12alkenyl, substituted or unsubstituted C2-C12alkynyl, substituted or unsubstituted C6-C26aryl, and substituted or unsubstituted C4-C12heterocyclic group;the substituent for the above groups, if present, is independently selected from a group consisting of halogen, cyano, C1-C6alkyl, C2-C6alkenyl, C1-C6alkoxy, and combinations thereof;x, y and z are each an integer independently selected from 0-8;m, n and k are each an integer independently selected from 0-2; andwherein the additive B is at least one halogenated cyclic carbonate compound.

Another purpose of the present disclosure is to provide an electrochemical device including a positive electrode plate, a negative electrode plate, a separator positioned between the positive electrode plate and the negative electrode plate, and an electrolyte according to the present disclosure.

The technical solutions of the present disclosure at least have the following beneficial effects:

The addition of both the multi-cyano six-membered N-heterocyclic compound and the halogenated cyclic carbonate compound as additives of the electrolyte according to the present disclosure can effectively passivate surface activity of the positive electrode material, inhibit oxidation of the electrolyte, and effectively reduce gas production of the battery, while an anode SEI film can be formed to avoid a contact between the anode and the electrode, thereby effectively reducing side reactions.

The electrochemical device using the electrolyte according to the present disclosure has a good cycle performance at high temperature and high voltage and a good storage performance at high temperature.

