Polyoxometalate Li₃ PW₁₂ O₄₀ and Li₃ PMo₁₂ O₄₀ Electrolytes for High-energy All-solid-state Lithium Batteries

Solid-state lithium (Li) batteries promise both high energy density and safety while existing solid-state electrolytes (SSEs) fail to satisfy the rigorous requirements of battery operations. Herein, novel polyoxometalate SSEs, Li₃ PW₁₂ O₄₀ and Li₃ PMo₁₂ O₄₀ , are synthesized, which exhibit excellent interfacial compatibility with electrodes and chemical stability, overcoming the limitations of conventional SSEs. A high ionic conductivity of 0.89 mS cm^-1 and a low activation energy of 0.23 eV are obtained due to the optimized three-dimensional Li⁺ migration network of Li₃ PW₁₂ O₄₀ . Li₃ PW₁₂ O₄₀ exhibits a wide window of electrochemical stability that can both accommodate the Li anode and high-voltage cathodes. As a result, all-solid-state Li metal batteries fabricated with Li/Li₃ PW₁₂ O₄₀ /LiNi_0.5 Co_0.2 Mn_0.3 O₂ display a stable cycling up to 100 cycles with a cutoff voltage of 4.35 V and an areal capacity of more than 4 mAh cm^-2 , as well as a cost-competitive SSEs price of $5.68 kg^-1 . Moreover, Li₃ PMo₁₂ O₄₀ homologous to Li₃ PW₁₂ O₄₀ was obtained via isomorphous substitution, which formed a low-resistance interface with Li₃ PW₁₂ O₄₀ . Applications of Li₃ PW₁₂ O₄₀ and Li₃ PMo₁₂ O₄₀ in Li-air batteries further demonstrate that long cycle life (650 cycles) can be achieved. This strategy provides a facile, low-cost strategy to construct efficient and scalable solid polyoxometalate electrolytes for high-energy solid-state Li metal batteries.