Deionized Water Pretreated Polyimide Nanofiber Membranes as Framework for Polymer Electrolytes Applied to Solid-State Lithium Metal Batteries

Incorporating a water-immersed polyimide membrane (WPI) as a framework into a polymer electrolyte PEO/SN/LiTFSI (PSL) can address the challenges faced by solid-state polymer electrolytes in practical applications for all-solid-state lithium-ion batteries (ASSLIBs) used in flexible and wearable electronics. The inferior mechanical performance and inadequate ionic conductivity of polymer electrolytes have hampered their widespread use. By utilizing a matrix of polyethylene oxide (PEO) along with succinonitrile (SN) and lithium bis(trifluoromethane)sulfonimide (LiTFSI) as additives, the WPI enhances the stability of the PSL electrolyte structure through reinforced internal hydrogen bonds of poly(amic acid), its precursor, post-thermal imidization in the presence of deionized water. This structural enhancement leads to improved mechanical properties, evidenced by a tensile strength of 12.2 MPa at a high porosity of 85.6%. The WPI-PSL electrolyte exhibits favorable ionic conductivity, thermal stability, and electrochemical compatibility with lithium metal. As a result, the WPI-PSL configuration demonstrates exceptional performance in a LiFePO₄/Li ASSLIBs system, showcasing outstanding cycling performance at both 30 and 60 °C, with capacity retention ratios reaching 94.6% and 96% after 100 cycles at 0.3 C, respectively. This research significantly advances the development of polymer solid-state electrolytes, propelling their use in flexible power sources for ASSLIBs.