Rock-Salt-Templated Mn₃O₄ Nanoparticles Encapsulated in a Mesoporous 2D Carbon Matrix: A High Rate 2 V Anode for Lithium-Ion Batteries with Extraordinary Cycling Stability

Metal oxide conversion electrodes suffer from low power density and cycling stability desired for high rate lithium-ion battery (LIB). Herein, we present a method of integrating nanoscale discrete Mn₃O₄ particles (20 nm) into a two-dimensional sheet-like N-incorporated mesoporous carbon by a simple synthetic protocol using NaCl crystallites as an exo-template. The encapsulated structure of Mn₃O₄@C greatly supresses the mechanical stress induced by repeated volumetric expansion/contraction and at the same time, N-incorporation in the carbon matrix facilitates charge transport. When tested as a 2.0 V LIB anode, Mn₃O₄@C showed an excellent rate performance (406 mAh g^-1 at 2.5 A g^-1 and 188 mAh g^-1 at 12.5 A g^-1) and outstanding cycling stability (capacity retention of 90% after 10000 cycles at 2.5 A g^-1). Such remarkable performance could be linked to fast charge transportation through the 2D carbon sheets and also, to the encapsulated structure avoiding direct contact with the electrolyte precluding growth of SEI layer upon cycling. Furthermore, a LiFePO₄//Mn₃O₄@C full cell delivers specific capacities of 136 mAh g^-1 and 92 mAh g^-1 (with respect to the mass of cathode) at current densities of 0.25 and 0.5 mA g^-1. The cell shows excellent cycling stability with 76% retention of capacity after 350 cycles demonstrating the practical viability.