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 Ti 2 SC with abundant oxygen vacancies by a facile surface engineering method. When using as a lithium storage anode, this oxygen-deficient Ti 2 SC 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 Ti 2 SC 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 Ti 2 SC 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. The surface oxides have been partially reduced and abundant oxygen vacancies are generated after reduction process, thus the obtained OV-Ti 2 SC show enhanced lithum-ion uptake due to the fast Li-ion transport and small charge transfer resistance.