Stable and fast Na-ion storage of recovered carbon from the spent carbon cathode of aluminum electrolysis

Abstract

The spent carbon cathode (SCC) generated in the aluminium electrolysis process is considered as hazardous solid waste; so, large amounts of research are conducted to study the environmental and economical purifying methods to separate the carbon and then make use of it effectively. This study treats SCC with a low-temperature and short-time sulfation roast process. The product, recovered carbon (RC), has a purity of 96.22 wt%, with the structural characteristic of a disordered and expanded crystal lattice. To take advantage of these features, and reuse the high value-added carbon material, the RC is used as the anode for Na-ion batteries directly, and the Na⁺ storage performance and mechanism are explored and stated. The RC electrode exhibits appreciable electrochemical performance in DME electrolyte solvent. It maintains a discharge plateau at 0.5 V to 1.0 V and discharges a specific capacity of 134 mA h g⁻¹ at a current density of 5000 mA g⁻¹. And for the stability, it exhibits ∼100% capacity retention after 2000 cycles at 1000 mA g⁻¹. The outstanding electrochemical performance comes from the capacitive behavior of Na⁺ in RC material. This “turning waste into wealth” strategy provides a reliable solution for the reuse of carbon-containing solid waste.