Work

Host–Guest Inversion Engineering Induced Superionic Composite Solid Electrolytes for High-Rate Solid-State Alkali Metal Batteries

Year: 2025

Type: article

Abstract: Composite solid electrolytes (CSEs) are promising for solid-state Li metal batteries but suffer from inferior room-temperature ionic conductivity due to sluggish ion transport and high cost due to expensive active ceramic fillers. Here, a host–guest inversion engineering strategy is proposed to develop superionic CSEs using cost-effective SiO2 nanoparticles as passive ceramic hosts and poly(vinylidene fluoride-hexafluoropropylene) (PVH) microspheres as polymer guests, forming an unprecedented “polymer guest-in-ceramic host” (i.e., PVH-in-SiO2) architecture differing from the traditional “ceramic guest-in-polymer host”. The PVH-in-SiO2 exhibits excellent Li-salt dissociation, achieving high-concentration free Li+. Owing to the low diffusion energy barriers and high diffusion coefficient, the free Li+ is thermodynamically and kinetically favorable to migrate to and transport at the SiO2/PVH interfaces. Consequently, the PVH-in-SiO2 delivers an exceptional ionic conductivity of 1.32 × 10−3 S cm−1 at 25 °C (vs. typically 10−5–10−4 S cm−1 using high-cost active ceramics), achieved under an ultralow residual solvent content of 2.9 wt% (vs. 8–15 wt% in other CSEs). Additionally, PVH-in-SiO2 is electrochemically stable with Li anode and various cathodes. Therefore, the PVH-in-SiO2 demonstrates excellent high-rate cyclability in LiFePO4|Li full cells (92.9% capacity-retention at 3C after 300 cycles under 25 °C) and outstanding stability with high-mass-loading LiFePO4 (9.2 mg cm−1) and high-voltage NCM622 (147.1 mAh g−1). Furthermore, we verify the versatility of the host–guest inversion engineering strategy by fabricating Na-ion and K-ion-based PVH-in-SiO2 CSEs with similarly excellent promotions in ionic conductivity. Our strategy offers a simple, low-cost approach to fabricating superionic CSEs for large-scale application of solid-state Li metal batteries and beyond.

Source: Nano-Micro Letters

DOI: 10.1007/s40820-025-01691-7