Cellulose acetate-promoted polymer-in-salt electrolytes for solid-state lithium batteries

Despite their non-flammability, low processing cost and wide electrochemical stability window, solid-state polymer electrolytes still exhibit certain challenges, such as high operating temperature and low room-temperature ionic conductivity. Cellulose acetate (CA) is a common natural polymer derivative, which is promising as a filler in polymer electrolytes due to its rich surface functional groups, superior mechanical properties and high porosity. Herein, CA is incorporated into a unique polymer-in-salt electrolyte based on lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) to design a composite polymer electrolyte (PLCA). The influence of CA content on the overall performance of PLCA is investigated. With 10 wt% of CA, PLCA exhibits high room-temperature ionic conductivity of 4.33 × 10−4 S cm−1, high Li-ion transference number of 0.60 and a wide electrochemical stability window (4.8 V). The resulting LiFePO4|Li solid-state lithium battery delivers a specific discharge capacity of 160.17 mAh g−1 at 0.2 C, with stable cycling ability and good rate capability. CA is found to promote the dissociation of lithium salt, reduce the crystallinity of polymer and further create a new Li-ion transport pathway in PLCA, responsible for the battery performance improvement. Our work provides an opportunity to design high-performance composite polymer-in-salt electrolytes for advanced solid-state batteries.