Cobalt-doped TiO2@C hierarchical nanocomposites derived from Ti3C2 MXene as cathodes for hybrid magnesium-lithium batteries

TiO2 has been explored in hybrid magnesium-lithium batteries (HMLBs) due to the advantages of low self-discharge and small volume expansion during ion insertion. However, how to improve the inherently low ionic and electrical conductivity of TiO2 is the problem that needs to be solved. In this work, a smart strategy is adopted to prepare cobalt-doped TiO2@C (Co4+-TiO2@C) hierarchical nanocomposite derived from Co(II)(OH)(n)@Ti3C2. Compared with TiO2@C (without cobalt doping), Co4+-TiO2@C shows the highest specific capacity (154.7 mAh center dot g(-)(1) at 0.1 A center dot g(-)(1) after 200 cycles) and extraordinary rate performance in HMLBs. The excellent electrochemical performance of Co4+-TiO2@C is ascribed to the synergistic effect of the hierarchical structure and cobalt-doping. Both experimental results and density functional theory (DFT) calculation reveal that the cobalt-doping has effectively improved the electronic conductivity and reduced the Li+ migration barrier. This work provides a new insight to design TiO2-based cathode materials with high-performance in HMLBs.