Carbon polyhedra encapsulated Si derived from Co-Mo bimetal MOFs as anode materials for lithium-ion batteries

Abstract

Silicon (Si) holds promise as an anode material for lithium-ion batteries (LIBs) as it is widely available and characterized by high specific capacity and suitable working potential. However, the relatively low electrical conductivity of Si and the significantly high extent of volume expansion realized during lithiation hinder its practical application. We prepared N-doped carbon polyhedral micro cage encapsulated Si nanoparticles derived from Co-Mo bimetal metal-organic framework (MOFs) (denoted as Si/CoMo@NCP) and explored their lithium storage performance as anode materials to address these problems. The Si/CoMo@NCP anode exhibited a high reversible lithium storage capacity (1013 mAh g−1 at 0.5 A g−1 after 100 cycles), stable cycle performance (745 mAh g−1 at 1 A g−1 after 400 cycles), and excellent rate performance (723 mAh g−1 at 2 A g−1). Also, the constructed the full-cell NCM811//Si/CoMo@NCP exhibited well reversible capacity. The excellent electrochemical performances of Si/CoMo@NCP were attributed to two unique properties. The encapsulation of NCP with doped nitrogen and porous structural carbon improves the electrical conductivity and cycling stability of the molecules. The introductions of metallic cobalt and its oxides help to improve the rate capability and lithiation capacity of the materials following multi-electron reaction mechanisms.