Tuning Work Function of Fe₂N@C Nanosheets by Co Doping for Enhanced Lithium Storage

Transition metal nitrides (TMNs) with high theoretical capacity and excellent electrical conductivity have great potential as anode materials for lithium-ion batteries (LIBs), but suffer from poor rate performance due to the slow kinetics. Herein, taking the Fe₂N for instance, Co doping is utilized to enhance the work function of Fe₂N, which accelerates the charge transfer and strengthens the adsorption of Li⁺ ions. The Fe₂N nanoparticles with various Co dopants are anchoring on the surface of honeycomb porous carbon foam (named Co_x-Fe₂N@C). Co-doping can enlarge the work function of pristine Fe₂N and thereby optimize the charging/discharging kinetics. The work function can be increased from 5.23 eV (pristine Fe₂N) to 5.67 eV for Co_0.3-Fe₂N@C and 5.56 eV for Co_0.1-Fe₂N@C. As expected, the Co_0.1-Fe₂N@C electrode exhibits the highest specific capacity (673 mA h g^-1 at 100 mA g^-1) and remarkable rate capability (375 mA h g^-1 at 5 000 mA g^-1), outperforming most reported TMNs electrodes. Therefore, this work provides a promising strategy to design and regulate anode materials for high-performance and even commercially available LIBs.