Surface oxygen-deficient Ti2SC for enhanced lithium-ion uptake

Recently, MAX phases show great potential in lithium-ion uptake due to their excellent electrical conductivity and unique lamellar-structure accommodating lithium ions. However, the reports about MAX electrodes for lithium-ion battery up to now are relatively low. Herein we report the preparation of surface oxygen-deficient Ti2SC with abundant oxygen vacancies by a facile surface engineering method. When using as a lithium storage anode, this oxygen-deficient Ti2SC delivers a high capacity of 350 mAh/g at a current density of 400 mA/g as well as excellent rate performance, doubling the capacity compared to that of Ti2SC without oxygen vacancies. Confirmed by electrochemical impedance spectroscopy (EIS) and kinetic mechanism analyses, after reducing surface oxides and generation of oxygen vacancies, the as-received Ti2SC exhibits higher electrical conductivity and faster lithium ion diffusion. Thus this work offers a facial and effective strategy of optimizing the surface structure of MAX phases, further to achieve an enhanced lithium-ion uptake for lithium-ion batteries or capacitors.