Optimization of structural expansion and contraction for TiS2 by controlling the electrochemical window of intercalation/delithiation

Abstract

A reversible layered structure of TiS₂ with relaxation like a spring, can be achieved by controlling the optimized potential range to 0.9–2.8 V (vs. Li⁺/Li) to yield a high discharge capacity, long cycling life, and excellent rate performance. The discharge capacity density and Coulombic efficiency for TiS₂ at the 100th cycle at 0.1 mA cm⁻¹ and 0.9–2.8 V are 321 mA h g⁻¹ and ∼100%, respectively, which are more effective and better than those over potential ranges of 0.8–2.8 V and 1.0–2.8 V. In response to this, the deeper lithiation of TiS₂ at 0.8 V leads to the formation of irreversible Ti₂S and results in poor cycling performance. The reduced lithiation of TiS₂ at 1.0 V results in low capacity density. Therefore, the relationship between the lithiation depth, structural stability, and electrochemical characteristics of TiS₂ as an electrode material is clarified. Controlling the optimized potential range for structural stability during discharge/charge is thus an effective way of improving electrochemical performance.