Hierarchically Porous N,S-Codoped Carbon-Embedded Dual Phase MnO/MnS Nanoparticles for Efficient Lithium Ion Storage

An intriguingly nanostructured composite comprising of MnO/MnS nanoparticles embedded in an N,S-codoped carbon frame (MnO/MnS@C) is designed here and employed as a promising Li-ion storage electrode material to address the challenge of inferior conductivity and large volume change toward manganese chalcogenide-based anode. Combining with the merits of coherent MnO/MnS, elaborately hierarchical-porous architecture and N,S-codoped carbon frame, this composite exhibits high lithium-ion storage capacity (591 mAh g^-1 at 0.1 A g^-1) and remarkable cyclic performance (628 mAh g^-1 at 1 A g^-1 over 330 cycles). It is revealed via quantitative analysis that capacitive effect is also responsible for Li⁺ storage except ordinary diffusion-controlled mechanism, which consists of faradaic surface pseudocapacitance rooting from further oxidation of Mn²⁺ and nonfaradaic interfacial double-layer capacitance stemming from the charge separation at the MnO/MnS phase boundary. As a dynamic equilibrium for diffusion-controlled lithium storage, such capacitive contribution leads to ever-increasing Li-ion storage. The delicate construction endows an improved ion/electron transport kinetics, increased electrode/electrolyte contact area and plentifully heterogeneous interface, accounting for the high capacity and long-cycle stability.