Applying multi-scale silica-like three-dimensional networks in a PEO matrix via in situ crosslinking for high-performance solid composite electrolytes

Abstract

For a higher safety and energy density, solid-state electrolytes with a better mechanical strength and thermal and electrochemical stability are a perfect choice. To improve the performance of PEO, using low-cost inert fillers may bring amorphous regions but limits easily appear. This paper aims to promote a network of SiO₂ nanowires by applying a novel in situ crosslinking structure composed of PEA, γ-GPS and mPEG with siloxane segments as the junctions. The modified network can significantly reduce the crystallinity and glass transformation temperature, which also reduces the activation energy of ion transfer. Crosslinking can be highly influential as a comprehensive function of segment relaxation and ion complexation. The optimal sample (PEO–SNWAKP20) possesses a conductivity of 2.52 × 10⁻⁴ at 40 °C and a wide electrochemical window of 5.1 V. This unique structure also brings ideal shape stability under high temperatures, thus realizing stable cycling for 800 h at 0.1 mA cm⁻². The rate and cycling performance of the LiFePO₄ cell are also improved, achieving a maximum of 131.2 mAh g⁻¹ under 0.5C with 89.3% retention after 50 cycles at 50 °C, realizing 24% improvement compared with single SNW reinforcement. By modifying the electrode, its performance can be further raised to 154 and 130.4 mAh g⁻¹ under 0.5C and 1C, respectively, reserving 97.9% of its capacity after 100 cycles. This may inspire new strategies for synthesizing high-performance composite electrolytes.