In situ constructed multilayer graphene structure enabling improved supercapacitive charge storage

Abstract

Designing controllable multilayer graphene (MLG) structure in amorphous carbons is crucial but still challenging to deliver durable supercapacitive energy storage. Herein, the lead is taken in in-situ nanoarchitecturing a 2–10 layered graphene structure within the amorphous carbon skeleton by the cobalt salt/sodium metal-assisted carbonization of starch. The rearrangement of graphite crystallites forms MLG structure, which shows a large specific surface area of 1917 m2 g−1 and a mesopore volume of 0.71 cm3 g−1. These two parameters are 1.64 and 1.46 times of the corresponding amorphous carbon. Such profitable structures promise a high specific capacitance of 312 F g−1 at 1 A g−1 and a durable cycle-life with 98.5% capacitance retention at 10 A g−1 over 100,000 cycles. The designed MLG structure in amorphous carbons matrix also exhibits an increased electrochemically active surface area from 392.5 to 599.5 m2 g−1, and a low ion-transport resistance (0.59 Ω s–0.5) as well as an ultrafast ion-response time (0.37 s), endowing the fabricated carbon supercapacitor with 67.7% capacitive contribution from fast-kinetics response at 10 mV s–1. Experiment characterization unravels the formation mechanism of MLG in amorphous carbons via the synergy of coalt salt and sodium metal. The elaborate design of MLG structure within amorphous carbon matrix provides an effective strategy to boost the electrochemical energy storage performances.