Dynamic Gradient Oxygen Layer Enables Stable Sn Anode for Lithium Storage.

Liu, Xi; Liu, Yang; Shao, Zerui; Pan, Guangyu; Peng, Yi; Wang, Xinying; Gao, Wanjie; Yang, Xiaohu et al. · Adv Mater · 2025

basic_science · Level V

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Abstract

Sn-based anodes are of significant interest due to their high capacity and resource abundance for lithium-ion batteries. However, incomplete lithiation and severe volume expansion result in their low capacity and electrode pulverization. Here, a rationally designed coating layer, composed of disordered SnO<sub>x</sub> (x = 1, 2) lamellar structures, on the Sn particles surface (Sn@SnO<sub>x</sub>) is proposed. This coating effectively mitigates volume expansion and minimizes lithium consumption owing to the intercalation behaviors of SnO<sub>x</sub>. During lithiation and delithiation, a dense, amorphous, mechanical coating with a dynamic gradient of oxygen forms in situ, providing excellent protection against continuous pulverization of the Sn particles. The intercalation-type dynamic gradient oxygen with high ionic conductivity enables rapid exchange of lithium ions, thus promoting the deep lithiation of Sn to form Li<sub>4.4</sub>Sn. Such gradient oxygen protection mechanism of the oxide layer in Sn@SnO<sub>x</sub> brings a high reversible capacity after 900 cycles with a capacity retention of 84%. This work offers a new strategy to design a protective coating layer on alloy-based anodes for high-performance lithium storage.