Enhancing Lithium-Ion Transport in Polymer Plastic Crystal Electrolytes via Formation of Physically Dynamic Networks

Solid polymer electrolytes (SPEs) are promising for lithium-metal batteries (LMBs), but they often suffer from low room-temperature ionic conductivity. Although polymer plastic crystal electrolytes (PPCEs) incorporating succinonitrile (SN) offer high ionic conductivity, their practical applications are limited owing to the mechanical softness and chemical reactivity of SN. In this study, PPCE formed by polyrotaxane (PR) networks is reported, wherein ring-shaped α-cyclodextrin (α-CD) units serve as sliding movable crosslinking points to form physically dynamic networks. This dynamic network preserves the intrinsic molecular mobility of SN while enhancing lithium-ion transport and maintaining mechanical integrity. Acrylate-funtionalized PR (APR)-PPCE exhibits high ionic conductivity of 2.0 × 10⁻³ S cm⁻ at 25 °C, a lithium transference number of 0.66, and tensile toughness of 34 kJ m⁻³. Li|APR-PPCE|LiFePO₄ (LFP) full cells exhibit stable cycling with 94% capacity retention over 250 cycles at 0.5 C and 98% over 220 cycles at 1.0 C. These cells deliver 101 mAh g⁻¹ even at 4.0 C, demonstrating that the sliding crosslinked network sustains rapid lithium-ion transport and preserves interfacial stability under high current densities. The proposed polymer-architecture strategy with a slidable PR network can help in the fabrication of high-performance SPE for LMBs.