Effect of Pyrolysis Temperature on the Leaching Behaviour of Spent Lithium Iron Phosphate Batteries with Sulfuric Acid and Sodium Hydroxide Solution

Greenhouse gas emissions from fossil fuel combustion account for approximately 68% of total global emissions, making their reduction essential to mitigating global climate change and achieving Net Zero Emissions by 2050. The transition to electric vehicles has accelerated the demand for lithium-ion batteries, particularly lithium iron phosphate (LFP) types, which are favoured for their reduced dependence to nickel and cobalt. This study explores the recycling of cylindrical spent LFP batteries through a processing involving seawater discharging, pyrolysis at 400–700 °C for 120 minutes, mechanical shredding, particle sieving, and leaching using 2.5 M H2SO4 and 5 M NaOH. Samples were characterized using scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), and LECO carbon analyser. Pyrolysis at 500 °C produced the highest lithium content in the -45 mesh fraction, reaching 4.11 wt%, and resulted in optimal lithium recovery in the leachate, with 4561.51 mg Li per cell using H2SO4 and 1719.32 mg Li per cell using NaOH. Although H2SO4 achieved higher lithium extraction, NaOH demonstrated greater selectivity against iron. These findings indicate that 500 °C is an effective pyrolysis temperature for enhancing lithium recovery from spent LFP battery.