High energy Li-ion capacitors using two-dimensional TiSe0.6S1.4 as insertion host

Abstract

A remarkable improvement in energy density was found using Se-substituted two-dimensional TiS₂ (TiSe_0.6S_1.4) as the insertion matrix in a Li-ion capacitor (LIC) assembly with activated carbon (AC) as the counter electrode. Chemical vapor transport was successfully used to synthesize high quality TiSe_0.6S_1.4 with near-100% crystallinity and subsequently employed as a battery component in LICs. Prior to LIC fabrication, the Li-insertion properties were assessed in single-electrode configuration with metallic Li. Single-electrode performance is crucial for adjusting the mass loading of AC and TiSe_0.6S_1.4 to realize the maximum energy density. Accordingly, an AC/TiSe_0.6S_1.4-based LIC delivered an energy density of ∼50 W h kg⁻¹ with a good cyclability of 5000 cycles. Few undesirable side reactions with the electrolyte counterpart were observed for TiSe_0.6S_1.4, as supported by the impedance measurements.