Ni-Assisted Catalytic/Electrochemical-Integrated Graphitization: Green Preparation and Mechanism Exploration of Energy-Storage Graphitized Carbon from Waste Charcoal

As the demand for efficient resource utilization continues growing, a green strategy for extracting high-value-added carbon materials from waste biomass has become imperative. This study proposed a Ni-catalyzed low-temperature electrochemical graphitization process for the first time: by cathodic polarization of woody biochar in molten CaCl2 (850–900 °C) with the assistance of Ni catalysis, it can be rapidly converted into high-performance energy-storage graphitized carbon. Ni-assisted catalysis not only substantially increased the graphitization rate but also significantly enhanced the graphitization effect (58.49% vs 79.01%). Additionally, the microstructure of the product could be precisely controlled through adjusting process parameters. Experiments and simulations revealed the kinetics of Ni-promoted deoxygenation reactions, the mechanism of electrolysis graphitization, and the role of Ni in enhancing key properties, such as the graphitization degree. When used as a negative electrode material for lithium-ion batteries, graphitized carbon exhibited excellent specific capacity (324.91 mAh g–1/1 C) and cycle life (331.59 mAh g–1/500 cycles at 0.2 C). This process provides a simple and sustainable method for the clean and high-value utilization of waste biomass, meanwhile widening feasible pathways for the disposal of carbon-containing solid waste, and can be extended to the graphitization conversion of other amorphous carbons.