Tuning Work Function of Fe ₂ N@C Nanosheets by Co Doping for Enhanced Lithium Storage

Abstract 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 Fe ₂ N for instance, Co doping is utilized to enhance the work function of Fe ₂ N, which accelerates the charge transfer and strengthens the adsorption of Li ⁺ ions. The Fe ₂ N nanoparticles with various Co dopants are anchoring on the surface of honeycomb porous carbon foam (named Co _x ‐Fe ₂ N@C). Co‐doping can enlarge the work function of pristine Fe ₂ N and thereby optimize the charging/discharging kinetics. The work function can be increased from 5.23 eV (pristine Fe ₂ N) to 5.67 eV for Co _0.3 ‐Fe ₂ N@C and 5.56 eV for Co _0.1 ‐Fe ₂ N@C. As expected, the Co _0.1 ‐Fe ₂ N@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.