Graphitic Co-Products of Clean Hydrogen Production Enabling High-Rate-Performance Dual-Carbon Batteries

Methane pyrolysis (CH4 -> 2H(2) + C) is a promising H-2 production process with zero CO2 emissions. Utilizing its solid carbon co-products can make it economically more competitive. Herein, this work demonstrates that graphitic carbon from methane pyrolysis can work as both cathodes and anodes to enable high-rate-performance dual-carbon batteries (DCBs), outperforming commercial natural and synthetic graphite. The graphite purity can reach 99.32 and 97.59 wt%, respectively, using a standard high-temperature thermal treatment or a room-temperature electrochemical method. Compared to graphite, they have smaller crystalline sizes and larger surface areas, enabling faster surface redox reactions and better structural stability upon electrolyte ion intercalation. DCB full cells with LiPF6 ethyl methyl carbonate electrolyte deliver energy storage capacities of 75.1 and 74.7 mAh g(-1) at 500 mA g(-1) with capacity retentions of 79.2% and 93.4% after the high-rate charge-discharge over 5000 mA g(-1), respectively. They can also be cycled at 500 mA g(-1) over 300 cycles without capacity decay, demonstrating excellent cycling stability. They show energy densities of 168.7 and 159.7 Wh kg(-1) at power densities of 10.6 and 10.8 kW kg(-1), outperforming recently reported DCBs. These findings open a new application of graphite co-product from the emission-free H-2 production process.