Triconstituent co-assembly to hierarchically porous carbons as high-performance anodes for sodium-ion batteries

Hierarchically porous carbons were prepared through triconstituent co-assembly of resols, oligomer silicates from tetraethyl orthosilicate (TEOS) and triblock copolymer F127 template, followed by carbonization and removal of silica. The as-prepared carbons possess abundant micropores and two kinds of mesopore with sizes of 3.7 and 6.3 nm. Upon the electrochemical testing against sodium, the hierarchically porous carbon electrodes exhibit sloping voltage profile during the first charge and subsequent cycles with superior electrochemical performance, delivering a reversible capacity of 180 mAh g⁻¹ at 0.1 A g⁻¹ after 200 cycles, which is much higher than 120 mAh g⁻¹ of the hierarchically porous carbon electrode without the addition of TEOS during the synthesis. The improved electrochemical performance may be ascribed to the combined contribution from the finer graphitic domain, higher degree of structural disorder, more abundant surface functional groups and most importantly, interconnected hierarchically mesoporous structure.