Interface-Optimized Composite Electrolytes Enabling Dendrite-Free Lithium Metal Batteries

Composite solid electrolytes (CSEs) have garnered significant attention due to their low cost and high safety. However, their practical application is significantly hindered by a low ionic conductivity and poor interfacial compatibility. Therefore, optimizing the structural design is critical for overcoming these challenges. This study designed a multilayer-nested composite solid electrolyte poly(ethylene oxide) (PEO)–polyacrylonitrile (PAN)–lithium lanthanum zirconium oxide (LLZO) to enhance the interfacial stability between the polymer electrolyte and lithium metal. Furthermore, the interactions between the functional groups in poly(ethylene oxide) and polyacrylonitrile suppressed the formation of ordered crystalline domains in poly(ethylene oxide). The prepared electrolyte demonstrates efficient Li+ transport and a robust mechanical network, which not only improves the transport efficiency of lithium ions but also ensures a uniform distribution of current density and stress, effectively suppressing dendrite growth. Remarkably, this composite structural design exhibits excellent ionic conductivity (1.79 × 10–4 S cm–1) and outstanding interfacial compatibility at 30 °C, allowing the Li/PPZO/LFP cell to deliver an initial discharge specific capacity of 145 mAh g–1 at a rate of 1C, along with a capacity retention of 89.6% after 1000 cycles. This work offers important references and directions for the further development of high-energy-density composite solid electrolyte (CSE) research.