Synergized N and P co-doped Ti₃C₂T_x mxene enabling high-performance Li-air batteries

Lithium-oxygen batteries (LOBs) with a theoretical energy density of up to 3500 Wh kg^-1 hold a promise for the next-generation high-energy-density batteries. However, the slow oxygen reduction/evolution kinetics at the cathode limits the performance of Li-air batteries. The rational design of efficient catalysts is essential for the improvement of oxygen electrode reaction kinetics. Herein, we report a facile strategy to co-dope N and P atoms simultaneously into Ti₃C₂T_x (NP-Ti₃C₂T_x) MXene via an electrostatic self-assembly approach. The co-doped NP-Ti₃C₂T_x layers expose abundant active sites, providing more space for accommodating the formed Li₂O₂. Moreover, the N and P co-doping facilitates efficient electron transport in Ti₃C₂T_x MXene. The LOB with NP-Ti₃C₂T_X catalyst delivers a high discharge capacity of 24,940 mAh/g at 1000 mA g^-1. At a cut-off capacity of 1000 mAh/g, this battery runs continuously for 159, 276, 185, and 229 cycles at current densities of 1000, 2000, 3000, and 5000 mA g^-1, respectively. Theoretical calculations unveil that N and P co-doping enables lower η^ORR and η^OER of only 0.26 V and 0.13 V on Ti₃C₂T_x MXene, respectively. This work offers a feasible approach for constructing efficient MXene electrocatalysts for Li-air batteries.