Multiscale structural engineering of Co0.85Se@porous carbon composite enables highly reversible lithium/sodium storage

Abstract

Cobalt selenide (Co0.85Se) has been regarded as the most potential anode material for both lithium/sodium ion batteries (LIBs and SIBs) due to its high specific capacity and excellent pseudocapacitive effect. However, the inevitable volume expansion during conversion reaction and grievous dissolution of Se in electrolytes seriously undermine its reversibility and cycling stability. Combining the transition-metal chalcogenides with stable porous carbon networks is considered as one of the most effective strategies to improve electrochemical stability and conductivity of transition-metal chalcogenides. Here, we proposed a multiscale structural engineering strategy to encapsulate selenide nanoparticles in N-doped porous carbon to enable high-performance Co0.85Se@porous carbon composite for highly reversible lithium/sodium storage. Specifically, the Co0.85Se nanoparticles are tightly anchored to carbon network through substantial SeC bond, which effectively buffer volume expansion and inhibit the dissolution of Se in electrolytes. Additionally, the carbon pores with multilevel size help achieving the fast ions diffusion. The unique structure enables the Co0.85Se composite anode to exhibit excellent discharge capacities of 955.1 mAh g−1 at 100 mA g−1 after 100 cycles, 305.6 mAh g−1 at 1 A g−1 of full cells after 550 cycles in LIBs and 491.3 mAh g−1 at 100 mA g−1 after 100 cycles in SIBs.