Preparation of flake graphite through molten-salt electrochemical graphitization of waste coffee ground carbon for lithium-ion battery anodes

Waste coffee grounds are used as a precursor to produce high-crystallinity graphite (CGG) via electrochemical graphitization of the high-temperature carbonized coffee grounds (CGC). Electrochemical graphitization is performed by cathodic polarization of the solid pellet of CGC in a molten salt electrolyte of CaCl₂. Under optimal conditions (850 °C, -1.7 V vs. Ag/AgCl, 8 h), the resulting CGG showed a high degree of crystallinity, with an I_D/I_G ratio as low as 0.14. When tested as an anode material for lithium-ion batteries, CGG exhibited excellent electrochemical performance. At a rate of 0.2C, it maintained a reversible capacity of 361.2 mAh g^-1 after 500 cycles. Concurrently, it exhibited an excellent rate capability, achieving a capacity retention of 33.3% at 10C relative to that at 0.1C. These results indicate that the molten salt electrochemical graphitization method offers a green and efficient route for the value-added utilization of waste coffee grounds.