Plastic crystal–solid biopolymer electrolytes for rechargeable lithium batteries

• Chitosan–LiTFSI films with different succinonitrile ratio were prepared using solution cast technique.
• The ionic conductivity of chitosan–LiTFSI films at room temperature were improved with the addition of succinonitrile.
• The improved ionic conductivity was attributed to the high lithium ions transference number value.
• The cell shows wide electrochemical window and excellent electrochemical performances.

In this paper, solid polymer electrolytes consisting of chitosan, lithium bis (trifluoromethylsulfonyl) imide (LiTFSI) as a salt and succinonitrile as a plastic crystal are prepared by using the solution casting method. Electrochemical impedance spectroscopy is used to examine the ionic conductivity of the films at the temperature range of 303–383 K. Chitosan–LiTFSI containing 50 wt% succinonitrile exhibits high ionic conductivity at a room temperature of 0.4×10−3 S cm−1, a high lithium ion transference number (0.598) and wide electrochemical window. The solid polymer electrolyte with LiFePO4 as a cathode displays a stable discharge capacity of 160 mAh g−1 for up to 50 cycles at a current density of 17 mA g−1. The results demonstrate the potential for the solid polymer electrolyte system to be used as an electrolyte in lithium rechargeable batteries.