A non-isothermal kinetic study on the extraction of metals from spent lithium iron phosphate batteries using the NH2SO3H roasting process

The non-isothermal kinetics of retired lithium iron phosphate (LiFePO₄) battery powder and amino sulfonic acid (NH₂SO₃H) roasting were studied using TG-DSC. The results show that there are three stages of weight loss: loss of adsorbed water, decomposition and reaction of NH₂SO₃H (stage Ⅱ), and formation and growth of Li and Fe sulfate nuclei (stage Ⅲ). The apparent activation energy (E) and pre-exponential factor (ln(A)) of NH₂SO₃H decomposition and reaction were 159.85 kJ/mol and 32.02 S⁻¹, respectively. Similarly, the apparent E and ln(A) formed by Li and Fe sulfate were 113.89 kJ/mol and 11.55 S⁻¹, respectively. Furthermore, the formation of new phases in the second stage reaction is controlled by nucleation and growth. The nucleation and growth of Li and Fe sulfates in the third stage not only occur at this stage, but their rates are also controlled by diffusion. The dynamic equations for the second and third stages are as follows:

$[{-\ln (1-\alpha )]}^{\frac{1}{3}}$=8.06$\times {10}^{13}$exp(-$\frac{1.60\times {10}^5}{\mathrm{RT}}$)t

$[{-\ln (1-\alpha )]}^{\frac{2}{3}}$=1.04$\times {10}^5$exp(-$\frac{1.14\times {10}^5}{\mathrm{RT}}$)t