Control the single-ion conductivity by tuning smectic liquid crystal polymer network for quasi-solid-state electrolytes

Single-ion conductive polymer electrolytes can effectively enhance the safety of lithium ion batteries (LIBs) by increasing the lithium transference number ( t Li + ) and avoiding the growth of lithium dendrites. Meanwhile, self-assembled ordered structure of liquid crystal polymer networks (LCNs) can form specific channels via the LC molecular orientation, benefiting the ordered transport of Li ions. Herein, two single-ion conductive smectic LCN electrolyte membranes coated on poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) film (denoted as SLCN-Li/Pv) were prepared by different ways. For comparison, one disordered polymer network electrolyte membrane coated on P(VDF-HFP) (denoted as DPN-Li/Pv) was also prepared. After coupling with plasticizer, three quasi-solid-state electrolyte membranes have been successfully produced. Their electrochemical properties were evaluated, and it was found that they possessed benign thermal stability and electrolyte/electrode compatibility. The high t Li + of 0.87 for SLCN-Li/Pv indicated their near-single-ion conductive characteristic. A small amount (0.5 M) of extra Li salt adding to the plasticizer could effectively improve the ion conductivity from 5.58 × 10 −6 to 1.58 × 10 −5 S cm −1 , while the t Li + remained 0.77. The assembled LFP|Li batteries also exhibited excellent cycling and rate performances. Compared with DPN-Li/Pv, SLCN-Li/Pv exhibited higher σ and t Li + , indicating that the orderliness of LC molecular orientation played an important role in the distribution and moving of Li ions, thereby affected the Li deposition and growth of Li dendrites. As the first report of smectic LCN single-ion conductors, this work throws light on the design and fabrication of ordered quasi-solid-state electrolytes for high-performance and safe LIBs.