Comprehensively-upgraded polymer electrolytes by multifunctional aramid nanofibers for stable all-solid-state Li-ion batteries

Satisfactory ionic conductivity and mechanical stability are the prerequisites for the applications of solid polymer electrolytes in Li-ion batteries. Herein, by using aramid nanofibers (ANFs) as multifunctional nano-additives, comprehensively-upgraded polyethylene oxide (PEO)-LiTFSI electrolytes with 3D ANF network frames are achieved through the hydrogen-bond interactions between the 1D ANFs. The hydrogen-bond interactions between the ANFs and the PEO chains and TFSI‒ anions can greatly prevent the ANF agglomeration, suppress the PEO crystallization, facilitate the LiTFSI dissociation, and prolong the ion transport paths at the 3D ANF framework/PEO-LiTFSI interfaces. Thus, the ANF-modified electrolytes show superior room-temperature conductivity of 8.8 × 10−5 S cm−1. The ANF-containing composite electrolytes also display greatly-enhanced mechanical strength, thermostability, electrochemical stability and interfacial resistance against Li dendrites, attributed to the 3D ANF framework. In consequence, the composite electrolyte-based LiFePO4/Li cells exhibit better rate performance and cycling stability (e.g., 135 mAh g−1 after 100 cycles at 0.4 C). This work offers a novel and effective strategy to comprehensively upgrade polymer electrolytes by employing organic nanofillers in the composite electrolyte design and revealing the ion transport mechanism for promising all-solid-state Li-ion battery applications.