Thermodynamic Simulations for Determining the Recycling Path of a Spent Lead-Acid Battery Electrolyte Sample with Ca(OH)2

Regeneration of NCM622 from end-of-life lithium-ion battery cathode materials

The boom of the electric vehicle industry significantly aggravates the demand for lithium-ion batteries (LIBs), especially the ternary cathode materials, however, the majority of end-of-life (EOL) LIBs on the market are batteries utilized in customer electronics. Here, we utilized the mixed EOL LIBs from cell phones and laptops to manufacture the LiNi_0.6Co0_.2Mn_0.2O₂ (NCM622) cathode material. A feasible, high efficiency (99.98% Co, 99.98% Ni, 99.99% Mn, and 99.99% Li), and ultra-fast leaching of EOL LIB cathodes was achieved. Thermodynamic calculations suggested that the coordination number, coordination species concentrations, and fractions have significant effects on the apparent activation energy and the equilibrium of the leaching reactions. The remanufactured NCM622 cathode material demonstrated a well-ordered layered hexagonal structure with a low Li⁺/Ni²⁺ mixing ratio, which facilitated reliable reversible capacity, low polarization, high rate capabilities (163.8 mA h g^-1), and capacity retention ratio (94.3%).

Simultaneous Removal of Residual Sulfate and Heavy Metals from Spent Electrolyte of Lead-Acid Battery after Precipitation and Carbonation

Spent electrolyte from lead-acid battery contains high concentrations of sulfate acid and heavy metals; therefore without proper handling, they might cause severe environmental pollution. A relatively high concentration of sulfate ions (approximately 3000 mg/L) and heavy metals still exists in the effluent even after precipitation with slaked lime and carbonation process, which need to be further processed to lower both the concentrations of sulfate and heavy metals for direct discharge. A process that involves the reduction of sulfate to sulfide with sulfate-reducing bacteria and precipitation of the excessive sulfide with Fe(OH)2 was adopted to dispose of the effluent after precipitation and carbonation for direct discharge. Thermodynamic calculations were adopted to narrow down the optimum experimental range and understand the precipitation mechanism. In the whole process, no new impurities nor ions were introduced and 99.2% of sulfate, 99.9% of sulfide, 99.1% of Ca and more than 94.6% of Pb and 99.8% of Cd were removed and the obtained effluent was safe to discharge.