Kinetics of leaching valuable metals from layered NCM811 cathode materials using lactic acid

The rapid electrification of the automotive industry has accelerated the demand for high-energy-density lithium-ion batteries, establishing nickel-rich layered oxides like LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) as a dominant cathode chemistry. While hydrometallurgical recycling using organic acids offers an eco-friendly alternative to inorganic processes, its industrial adoption is often hindered by inherently slow reaction kinetics. This study presents a process intensification strategy for the rapid recovery of valuable metals from NCM811 using a biodegradable lactic acid and hydrogen peroxide (H 2 O 2 ) system. Unlike previous studies that focused solely on final yields, the kinetic trade-off between reduction power and the “gas blocking effect” was investigated. It was found that while H₂O₂ is essential for reducing insoluble Co 3+ /Ni 3+ /Mn 4+ , an excessive dosage (3.0 vol%) generates vigorous oxygen evolution that physically blocks the solid-liquid interface, reducing Co leaching efficiency from 88.6% (at 2.0 vol%) to 79.5%. Kinetic analysis using the Avrami model confirmed a surface reaction-controlled mechanism with high activation energies (75–95 kJ/mol). Based on this mechanistic insight, the process was intensified by optimizing the solid-to-liquid (S/L) ratio to 10 g/L. This adjustment was not merely for dilution but to maximize the “space-time yield” of the reactor. Under the optimized conditions (90 °C, 2.0 vol% H 2 O 2 , S/L 10 g/L), a remarkable Co leaching efficiency of 96.6% was achieved within only 20 min. These findings demonstrate that overcoming kinetic barriers through precise reductant control and process intensification can make organic acid leaching competitively fast for industrial application. • Eco-friendly leaching of spent NCM811 cathode using lactic acid was investigated. • Gas blocking effect by H 2 O 2 decomposition was identified and optimized. • Leaching kinetics were well-fitted to the Avrami equation model. • High recovery efficiency (>99%) of all metals was achieved within 20 min.