Ordered mesogenic units-containing hyperbranched star liquid crystal all-solid-state polymer electrolyte for high-safety lithium-ion batteries

Abstract

Functional liquid crystal polymers have attracted much attention as new all-solid-state polymer electrolytes due to their ability of orientation. In this paper, a hyperbranched star liquid crystal polymer (HSLCP) electrolyte for lithium-ion batteries (LIBs) is developed for the first time. This type of HSLCP bears a hyperbranched poly(glycidol) (HPG) as core, poly-ε-caprolactone (PCL) and poly (4-cyano-biphenyl methylmethacrylate) ((LC)x) compose the block arms of the HSLCP. (LC)x segments, one part of the arms, are assisted to promote transmission of Li-ion via orientation and PCL segments are used to dissociate lithium salt and efficiently migrate charge carriers. The good self-standing all-solid-state polymer electrolyte film composed of HSLCP and lithium bis(trifluoromethanesulfonimide (LiTFSI) can be formed by solution casting method. It is demonstrated that such a HSLCP exhibits good thermal stability (368°C), the HSLCP-based electrolyte shows high ionic conductivity (5.98 × 10−5 S cm−1 at 30°C), outstanding ion transference number (0.63), and wide electrochemical window (5.12 V). In addition, LiFePO4/Li batteries employing the electrolyte deliver good cycling performance and rate capability. Simultaneously, the corresponding half-cell can still power a LED lamp at room temperature. Thus, this is a great progress for liquid crystal-based polymer electrolytes to be applied to high energy LIBs.