Chemical Formation of Self-Healing Solid Electrolyte Layers on Lithium Anode

Abstract

All solid state batteries have potential to solve safety issues over the current state of lithium ion batteries (LIBs) due to the absence of flammable organic electrolytes [1,2]. Among many components of them, solid electrolyte layer is considered as a key factor enabling all solid chemistries, which can enable high energy density and stable post LIBs. Further, the mechanical strength of solid electrolyte can suppress lithium dendrite growth during cycling and its stable interface can prevent the continuous side reactions caused by organic electrolytes. Finally, solid electrolyte can be a promising solution for the prevailing shuttle problem of post Li-S batteries [3]. Solid electrolytes have so far failed to achieve its great promise and the practical use of all solid batteries have been restricted due to their poor stability and complex synthesis process. Indeed, it has been observed that the penetration of dendrite through the electrolyte layer of mm level thickness lead to a cell failure. Furthermore, fabrication methods for solid electrolyte developed so far are expensive and complex, which commonly requires repeated high temperature heat treatments and compression under high pressure. These limitations are major huddles for current solid electrolyte and all-solid batteries. Here, we propose a new approach to develop a self-forming and -healing solid electrolyte that can be fabricated by solution processing. We target to form the LPS (Li2S-P2S5) electrolyte layer directly on lithium through the in-situ formation of the solid electrolyte layer, which can eliminate both the complex synthesis process used for the conventional sold electrolytes and the need for high temperature sintering process. Furthermore, by the addition of an oxidant in the solution layer, lithium dendrite growth, even if it ever penetrates the LPS layer, can be prevented, serving as a self-healing mechanism. This design can greatly simplify cell fabrication process of solid electrolyte and the inherent self-healing capabilities can offer a new path for post Li batteries with performance advantage over LIBs. [1] P. G. Bruce et al., Nat. Mater. 2012, 11, 19-29. [2] X. Ji et al., Nat. Mater. 2009, 8, 500-506. [3] Z. Lin et al., J. Maters. Chem. A 2015, 3, 936-958.