Hydrothermal nanocasting: Synthesis of hierarchically porous carbon monoliths and their application in lithium–sulfur batteries

Abstract

This manuscript reports a hydrothermal nanocasting method using hierarchically meso-macroporous silica monolith templates to synthesize hierarchically porous carbon monoliths. Abundant and cheap carbohydrates (i.e. sucrose, glucose and xylose) can be used as precursors for the synthesis of such monolithic carbons. The development of porosity at different post-calcination temperatures is investigated. Upon removal of the silica template after hydrothermal carbonization only (180°C, 10bars), the polymer-like furan-rich structure is too “soft”, blocking the mesopores and exhibiting a low porosity. Increasing the post-treatment temperature up to 950°C increases both BET surface area and pore volume up to 1426m2g−1 and 3.097cm3g−1, respectively. Further thermal treatment induces also a loss of surface functional groups and an increase in the conductivity, while preserving the initial monolithic aspect. Such a versatile control over porosity at different length scales, functionality and conductivity offers the opportunity to adapt the synthetic parameters to the aimed application. Herein, we used our highly porous monolithic carbons as sulfur hosts for lithium–sulfur batteries. With this aim, we infiltrated a large amount of sulfur within the carbonaceous scaffolds reaching an initial discharge capacity of 1305mAhg−1 at a current density of 167.5mAg−1.