Size-Dependent Charge Storage Behavior of Mesoporous Hollow Carbon Spheres for High-Performance Li–Se Batteries

Hollow carbon spheres (HCSs) synthesized by a template-assisted hydrothermal carbonization approach have been evaluated as selenium cathode support in rechargeable lithium–selenium batteries. Homogenously formed hollow carbon microspheres upon selenium impregnation perform exceedingly well in lithium–selenium battery with a specific capacity of 500 mAh/g for 200 cycles. The unique carbon framework is capable of performing as a conducting medium as well as a polyselenide mediator, especially during charge/discharge cycles, owing to inherent benefits, such as a high surface area and porous nature. More importantly, the hollow nature of the carbon spheres is beneficial in reducing the volume expansion-related issues, resulting in good rate capability. Postcycling structural stability has been demonstrated by ex situ transmission electron microscopy studies of Se@HCS composite microsphere cathode, wherein no significant change has been noticed even after 200 cycles, thus substantiating the excellent electrochemical performance. The synergetic effect of the hollow structure, high surface area, and combination of meso/micropores of carbon, along with the high electronic conductivity of selenium promote facile diffusion of lithium ions and electrons, resulting in appreciable electrochemical performance.