Advancing High-Energy Solid-State Batteries with High-Entropy\nNASICON-type Solid Electrolytes

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