Fabrication of Single-Ion\nConductors Based on Liquid\nCrystal Polymer Network for Quasi-Solid-State Lithium Ion Batteries

Single-ion conductive polymer electrolytes can improve\nthe safety\nof lithium ion batteries (LIBs) by increasing the lithium transference\nnumber (<i>t</i><sub>Li</sub><sup>+</sup>) and avoiding\nthe growth of lithium dendrites. Meanwhile, the self-assembled ordered\nstructure of liquid crystal polymer networks (LCNs) can provide specific\nchannels for the ordered transport of Li ions. Herein, single-ion\nconductive nematic and cholesteric LCN electrolyte membranes (denoted\nas NLCN-Li and CLCN-Li) were successfully prepared. NLCN-Li was then\ncoated on commercial Celgard 2325 while CLCN-Li was coated on poly(vinylidene\nfluoride-hexafluoropropylene) film, coupled with plasticizer, to make\nNLCN-Li/Cel and CLCN-Li/Pv quasi-solid-state electrolyte membranes,\nrespectively. Their electrochemical properties were evaluated, and\nit was found that they possessed benign thermal stability and electrolyte/electrode\ncompatibility, high <i>t</i><sub>Li</sub><sup>+</sup> up\nto 0.98 and high electrochemical stability window up to 5.2 V. A small\namount (0.5M) of extra Li salt added to the plasticizer could improve\nthe ion conductivity from 1.79 × 10<sup>–5</sup> to 5.04\n× 10<sup>–4</sup> S cm<sup>–1</sup>, while the <i>t</i><sub>Li</sub><sup>+</sup> remained 0.85. The assembled\nLFP|Li batteries also exhibited excellent cycling and rate performances.\nThe orderliness of the LCN layer played an important role in the distribution\nand movement of Li ions, thereby affecting the Li deposition and growth\nof Li dendrites. As the first report of nematic and cholesteric LCN\nsingle-ion conductors, this work sheds light on the design and fabrication\nof ordered quasi-solid-state electrolytes for high-performance and\nsafe LIBs.