Reinforced structural stability of Li-rich Mn-based cathodes by constructing multifunctional heterostructure using Nb-based MXenes

Lithium rich manganese based materials (LMR) have promised the likeliest   candidate for next generation lithium-ion battery cathodes owing to its high energy density and low materials cost. However, severe capacity decline and voltage decay hinder their practical application, which is closely concerned with the structure degradation and irreversible oxygen release. Herein, a simple strategy to reinforce the structural stability of LMR materials by constructing heterostructure with Nb-based MXenes (Nb 2 CT x / Nb 4 C 3 T x ) is proposed. A small amount of spinel phase and pseudo-bonding between Nb and O ions as well as extra oxygen vacancies can be induced by the MXenes addition in LMR, effectively inactivating the surface oxygen and suppressing the structure distortion. In addition, MXene can also alleviate the volume change during cycling process and provide additional transport channels for electrons. The ably designed 3 wt% LMR/Nb 2 CT x cathode presented high initial Coulombic efficiency of 85.6% at 0.1C (vs. 77.4% for the pristine material) and excellent cycling performance with a capacity retention of 83.8% after 200 cycles at 0.5C (vs. 66.6% for the pristine material). This work sheds some light on stabilizing the structure of lithium-rich manganese materials and provides a new idea for the design of other high performance cathode materials.