High thermal stability and tensile-strength bacterial cellulose–silica–PEO composite solid polymer electrolyte for long-life and dendrite-free lithium metal batteries

The increasing demand for high-energy-density and safe energy storage systems has driven the advancement of solid-state lithium metal batteries (LMBs). However, conventional liquid electrolytes face serious challenges such as dendrite growth, low thermal stability, and flammability, which limit their practical application. Solid polymer electrolytes (SPEs) have emerged as promising alternatives due to their improved safety and flexibility, but they still suffer from low ionic conductivity and insufficient mechanical and thermal robustness. In this study, we report a novel SPE composed of SiO₂-coated bacterial cellulose and polyethylene oxide (BC/PEO@SiO₂), synthesized <i>via</i> a facile and cost-effective sol-gel method. The incorporation of SiO₂-coated BC nanofibers significantly enhanced the composite's mechanical strength and thermal resistance, achieving a nearly sevenfold increase in tensile strength compared to neat PEO. Moreover, the membrane maintained its structural integrity even at 150 °C. Electrochemical testing confirmed the excellent performance of the BC/PEO@SiO₂ as a SPE. The Li|BC/PEO@SiO₂|Li symmetric cell maintained stable lithium plating and stripping behavior for over 700 hours, indicating superior interfacial stability. Furthermore, the LFP|BC/PEO@SiO₂|Li full cell exhibited a high reversible capacity of 113 mA h g^-1 and retained 94% of its initial capacity after 200 cycles. These results demonstrate that BC/PEO@SiO₂ is a promising and scalable SPE platform for next-generation, safe and high-performance solid-state lithium batteries.