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·g⁻¹ at 0.1 A·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.