Amorphous carbon monoliths with tunable microstructures are candidate anodes for future lithium-based energy storage. Enhancing lithium storage capability and solid-state diffusion kinetics are the precondition for practical applications. Transforming intrinsic oxygen-rich defects into active sites and engineering enlarged interlayer spacing are of great importance. Herein, a novel explosion strategy is designed based on oxalate pyrolysis producing CO and CO2 to successfully prepare lignin-derived carbon monolith (LSCM) with active carbonyl (C═O) groups and enlarged interlayer spacing. Explosion promotes the demethylation of methoxyl groups and cleavage of carboxyl groups to form C═O groups. CO2 etches carbon atoms in a short time to improve the heteroatom level, expanding the interlayer spacing. ZnC2O4 is decomposed at 400 °C, simultaneously producing CO and CO2, which constructs less C═O groups and large interlayer spacing. MgC2O4 is decomposed at 450 and 480 °C, staged-weakly producing CO and CO2, which constructs more C═O groups and larger interlayer spacing. CaC2O4 is decomposed at 480 and 700 °C, staged-uniformly producing CO and CO2, which constructs abundant C═O groups and largest interlayer spacing. The LSCM prepared by staged-uniform explosion exhibits high lithium storage capacity, superior rate capability, and cycling performance. The assembled lithium ion capacitor device achieves excellent energy/power densities of 78 Wh kg-1/100 W kg-1 and superior durability (capacitance retention of 8 4.6% after 20,000 cycles). This work gives a novel insight to engineer advanced oxygen-functionalized carbons for enhanced lithium storage.
Keywords: carbon anodes; carbonyl groups; explosion; lignin; lithium ion capacitor.