Cellulose nanofiber-reinforced solid polymer electrolytes with high ionic conductivity for lithium batteries

Lithium-metal electrodes are promising for developing next-generation lithium-based batteries with high energy densities. However, their implementation is severely limited by dendritic growth during battery cycling, which eventually short-circuits the battery. Replacing conventional liquid electrolytes with solid polymer electrolytes (SPEs) can suppress dendritic growth. Unfortunately, in SPEs the high stiffness required for suppressing dendrites comes at the expense of efficient lithium-ion transport. Some polymer-based composite electrolytes, however, enable the decoupling of stiffness and ionic conductivity. This study introduces a composite SPE comprised of a relatively soft poly(ethylene oxide-co-epichlorohydrin) (EO-co-EPI) statistical copolymer with high ionic conductivity and cellulose nanofibers (CNFs), a filler with extraordinary stiffness sourced from abundant cellulose. CNF-reinforcement of EO-co-EPI increases the storage modulus up to three orders of magnitude while essentially maintaining the SPE's high ionic conductivity. The composite SPE exhibits good cycling ability and electrochemical stability, demonstrating its utility in lithium metal batteries.

Automated summary

Replacing liquid electrolytes with solid polymer electrolytes in lithium-based batteries can inhibit dendritic growth, but it often compromises the efficiency of lithium-ion transport. This study introduces a composite solid polymer electrolyte that combines a soft copolymer with high ionic conductivity and cellulose nanofibers, which enhances the hardness without sacrificing the ionic conductivity. The composite electrolyte demonstrates good cycling ability and electrochemical stability, showing great potential for application in lithium metal batteries.