Scalable Hydrometallurgical Process for LFP Battery Recycling with Selective Lithium Extraction and Iron Stabilization

The expanding electric vehicle market is driving a critical demand for lithium-ion battery materials, positioning spent batteries as a strategic urban resource. Conventional hydrometallurgical studies are typically constrained by low solid-to-liquid (S/L) ratios (e.g., 1:50 g/mL), which limits their industrial relevance. This work adapted and optimized the MONOLITHOS-patented HCl–H2O2 leaching system to achieve in situ oxidative delithiation and selectively extract lithium (Li) from spent lithium iron phosphate (LFP) black mass under intensified S/L ratios (1:10 to 1:2 g/mL) relevant to scalable applications. Leaching parameters were optimized using response surface methodology based on a Box–Behnken design. High solids loadings introduced mass-transfer limitations and proton depletion, while LFP delithiation was governed by competitive iron dissolution. Under optimized ambient leaching conditions at intensified pulp density, selective leaching achieved 86.0% Li extraction efficiency while suppressing iron dissolution to 19.2% through solid-state FePO4 fixation. Downstream purification at a controlled acidic pH precipitated 99.7% of the dissolved iron, with minimal lithium co-precipitation (<0.55%). Subsequent oxidative polishing removed residual iron, and thermal preconcentration enabled carbonate precipitation, yielding technical-grade Li2CO3 with an estimated mass-balance purity of 97.3%. The results demonstrate an efficient, low-energy, intensified route for sustainable LFP recycling at industrially relevant pulp densities.