Electrolyte and lithium secondary battery comprising same

Abstract

The present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery comprising same. More specifically, the present invention relates to an electrolyte fora lithium secondary battery which maintains a uniform concentration of lithium ions on the surface of a lithium metal anode even if the electrolyte contains only a small amount of an additive comprising a functional group forming a bond with a lithium metal and a polyethylene oxide chain interacting with lithium ions, such that growth of lithium dendrites can be suppressed.

Description

technical field [0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2018-0054612 filed on May 14, 2018 and Korean Patent Application No. 10-2019-0054060 filed on May 9, 2019, and The entire contents disclosed in the references of these Korean patent applications are hereby incorporated as a part of this specification. [0002] The present invention relates to an electrolyte capable of suppressing growth of lithium dendrites and improving performance of the battery in a lithium secondary battery including lithium metal as a negative electrode, and a lithium secondary battery including the same. Background technique [0003] With the rapid development of electrical, electronic, communication and computer industries, the demand for secondary batteries with high performance and high stability is rapidly increasing in recent years. In particular, in accordance with the trends of weight reduction, thinning, miniaturization, and portabi...

AI Technical Summary

Problems solved by technology

[0007] However, due to the high chemical / electrochemical reactivity of lithium metal, lithium metal batteries easily react with electrolytes, impurities, lithium salts, etc. to form a passivation layer (solid electrolyte interfacial layer; SEI) on the surface of the electrode, and such passivation The dendritic layer leads to localized current density differences to form dendritic dendrites on the surface of Li metal

Lithium dendrites not only shorten the life of lithium secondary batteries, but also cause internal failure of the battery and inert lithium (dead lithium), thereby aggravating the physical and chemical instability of lithium secondary batteries, reducing the capacity of the battery, and shortening the cycle life. and adversely affect the stability of the battery

Besides, since the passivation layer is thermally unstable, when the battery is continuously charged / discharged or stored at a high temperature especially in a fully charged state, the passivation layer may be damaged due to increased electrochemical and thermal energy gradually collapsed

The side reaction in which the lithium metal surface exposed due to the collapse of the passivation layer directly reacts with the electrolytic solvent to decompose continuously occurs, thereby increasing the resistance of the negative electrode and reducing the charge / discharge efficiency of the battery

In addition, there is a problem that the electrolytic solvent is consumed at the time of the formation of the passivation layer, and the battery life is reduced due to by-products and gases generated during various side reactions such as the formation and collapse of the passivation layer and the decomposition of the electrolyte

[0010] For example, Korean Patent Application Publication No. 10-2014-0027206 relates to an electrolyte composition in the form of a colloidal dispersion containing a binder such as poly(ethylene glycol) dimercapto to reduce its presence in the electrolyte. It has the effect of reducing the mobility of the electrolyte due to the binder and improving the ion conductivity and / or cycle performance, but there are the following disadvantages: due to the use of all solid batteries, a large amount must be included in the electrolyte composition the binder

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