Embedding Fe-Based Redox Chemistry Into Low-Cost Oxyhalide Solid Electrolytes for High-Performance All-Solid-State Batteries.

Zhou, Zhimin; Lu, Pushun; Liang, Suzhe; Tuo, Kaiyong; Fu, Jiamin; Xia, Shengjie; Chen, Yilin; Wu, Zhiyun et al. · Adv Mater · 2026

basic_science · Level V

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Abstract

Halide solid electrolytes (SEs) with excellent ionic conductivity and wide electrochemical stability windows are promising for next-generation all-solid-state batteries (ASSBs). However, their intrinsic electrochemical inertness and high cost significantly constrain the attainable energy density and large-scale applicability of ASSBs. Here, we integrate Fe<sub>2</sub>O<sub>3</sub> into Li<sub>2</sub>ZrCl<sub>6</sub> (LZC) to construct an electrochemically active and cost-effective oxyhalide SE (Li<sub>1.6</sub>ZrFe<sub>0.8</sub>O<sub>1.2</sub>Cl<sub>5.6</sub>, denoted LiZrFeOCl-1604), which enables Fe-based redox chemistry while preserving cost-effectiveness. Benefiting from its amorphous framework comprising interconnected Zr─O/Cl, Fe─O/Cl, and Li─Cln (n ≤ 6) polyhedra,LiZrFeOCl-1604 exhibits a high ionic conductivity of 2.55 mS cm<sup>-1</sup> and a pronounced reversible capacity of 163 mAh g<sup>-1</sup>. Coupled with LiFePO<sub>4</sub> (LFP) cathode, the composite electrode delivers a high capacity of 321.6 mAh g<sup>-1</sup> and an energy density of 982.1 Wh kg<sup>-1</sup> (based on LFP mass), representing a 101.8% enhancement over electrochemically inactive LZC. Moreover, the ASSBs retain 92.7% of its initial capacity (205.7 mAh g<sup>-1</sup>) over 800 cycles at 1C rate. Notably, this asynchronous charge-discharge behavior not only boosts the practical energy density but also mitigates safety risks associated with overcharge and overdischarge of ASSBs.