Advancing High-Energy Solid-State Batteries with High-Entropy NASICON-type Solid Electrolytes

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Herein, we have developed a High-Entropy ( ∼1.52 R, calculated at M-site) lithium-stuffed NASICON-type solid electrolyte [Li 1.3 Sn 1.7/3 Zr 1.7/3 Ti 1.7/3 Al 0.1 Sc 0.1 Y 0.1 (PO 4 ) 3 ] with a total (grain + grain-boundary) ionic conductivity of ∼1.42 × 10 –4 S cm –1 (highest reported among NASICONs containing Zr–Sn–Ti) and a low activation energy of ∼0.33 eV with a relative density of Conventionally Sintered pellet ∼94%. Symmetric cells with a PVDF-HFP/LiTFSI buffer layer showed stable performance for 500 cycles at 0.2 mA cm –2 without short-circuiting. Full cells with LiFePO 4 retained ∼99% capacity after 100 cycles at 1C, while those with NMC811 delivered ∼140 mAh g –1 at C/3.