Ba, Nb Co-Doped LLZO Reinforced PEO Composite Solid Electrolyte for High-Performance Solid-State Lithium Batteries

Owing to its high lithium-ion conductivity, the cubic garnet-phase material Li 7 La 3 Zr 2 O 12 (LLZO) is a widely adopted key component in the fabrication of composite solid-state electrolytes (CSSEs). Nevertheless, the advancement of all-solid-state lithium batteries (ASSLBs) is still hindered by two major challenges: the high intrinsic crystallinity of poly(ethylene oxide) (PEO) and poor interfacial stability. Herein, cubic garnet Li 6.3 La 2.7 Ba 0.3 ZrNbO 12 (LLBZNO) featuring Ba and Nb co-doping was first prepared by a conventional solid-state method. Following this, the material was dispersed within a PEO matrix to construct composite solid-state electrolytes. Adding LLBZNO served to decrease PEO's crystallinity while enhancing its mechanical flexibility and bolstering its interfacial compatibility with lithium metal. The optimized membrane demonstrated superior properties, including a high Li + transference number of 0.75 (at 60°C) and an extended electrochemical stability window of up to 5.1 V (vs. Li/Li + ) under the present testing conditions. It also showed an excellent ability to suppress dendrites, facilitating stable cycling at 0.1 mA cm −2 for 1500 h without short-circuiting. Furthermore, the LFP/LLBZNO–PEO/Li battery delivered a high discharge capacity of 101.6 mA h g −1 after 300 cycles at 1°C with nearly 99% coulombic efficiency. These findings highlight that LLBZNO-PEO composite solid electrolytes possess superior ionic transport, electrochemical stability, and mechanical robustness, providing a viable pathway toward the advancement of next-generation high-performance ASSLBs.