Hierarchical Design of Mn2P Nanoparticles Embedded in N,P-Codoped Porous Carbon Nanosheets Enables Highly Durable Lithium Storage

摘要

Although transition metal phosphide anodes possess high theoretical capacities, their inferior electronic conductivities and drastic volume variations during cycling lead to poor rate capability and rapid capacity fading. To simultaneously overcome these issues, we report a hierarchical heterostructure consisting of isolated Mn2P nanoparticles embedded into nitrogen- and phosphorus-codoped porous carbon nanosheets (denoted as Mn2P@NPC) as a viable anode for lithium-ion batteries (LIBs). The resulting Mn2P@NPC design manifests outstanding electrochemical performances, namely, high reversible capacity (598 mA h g(-1) after 300 cycles at 0.1 A g(-1)), exceptional rate capability (347 mA h g(-1) at 4 A g(-1)) and excellent cycling stability (99% capacity retention at 4 A g(-1) after 2000 cycles). The robust structure stability of Mn2P@NPC electrode during cycling has been revealed by the in situ and ex situ transmission electron microscopy (TEM) characterizations, giving rise to long-term cyclability. Using in situ selected area electron diffraction and ex situ high-resolution TEM studies, we have unraveled the dominant lithium storage mechanism and confirmed that the superior lithium storage performance of Mn2P@ NPC originated from the reversible conversion reaction. Furthermore, the prelithiated Mn2P@NPC parallel to LiFePO4 full cell exhibits impressive rate capability and cycling stability. This work introduces the potential for engineering high-performance anodes for next-generation high-energy-density LIBs.