High-Valence-Cation-Induced Lattice Expansion for Activating Li<sub>2</sub>S Cathode in All-Solid-State Lithium-Sulfur Batteries.

Hong, Shuang; Cao, Yun; Qi, Jiangshan; Geng, Chuannan; Ye, Ruiqing; Wei, Lingjing; Wang, Yanyan; Zhang, Boya et al. · Adv Mater · 2026

basic_science · Level V

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Abstract

The practical deployment of lithium sulfide (Li<sub>2</sub>S) cathodes in all-solid-state lithium-sulfur batteries (ASSLSBs) is challenged by their poor innate conductivities and high activation barriers. Here, we demonstrate a lattice engineering strategy using Zr<sup>4+</sup> substitution to fundamentally activate Li<sub>2</sub>S. The introduced Zr<sup>4</sup> <sup>+</sup> expands the lattice, creating lithium vacancies that enhance ionic conductivity by two orders of magnitude. Simultaneously, Zr─S orbital hybridization narrows the bandgap for superior electronic conductivity and weakens Li─S bonds to lower the activation energy. This synergistic effect enables a highly reversible solid-state sulfur conversion. As a result, our ASSLSB delivers an ultrahigh energy density of 996.2 Wh kg<sup>-1</sup> based on the cathode with a record 65 wt.% electrode-level Li<sub>2</sub>S content and maintains stability for over 100 cycles, far exceeding the conventional configuration of ∼40 wt.% loading. This strategy establishes a viable pathway toward practical high-energy-density ASSLSBs by fundamentally activating Li<sub>2</sub>S electrochemistry.