Mechanistic Insight into Biosafe Upcycling of Spent NCM111 Cathodes: Microbial Metabolism and HA-Driven Metal Recovery

Abstract

The rapid growth in lithium-ion battery consumption necessitates eco-friendly and sustainable methods for recovering strategic metals from spent cathodes. In this study, a food-grade, biosafe strain, Lactiplantibacillus plantarum, was employed for the bioleaching of spent LiNi 0.33 Co 0.33 Mn 0.33 O 2 cathode material. Under optimized conditions (solid/liquid ratio of 5.0 g/L, pH 3.9–4.1), recovery efficiencies for Li, Ni, Co, and Mn reached 54.5%, 46.1%, 45.1%, and 45.5%, respectively. The introduction of 200 mg/L humic acid (HA) further elevated these yields to 62.7%, 60.7%, 53.0%, and 53.0%. Microstructural characterizations showed that the HA-supplemented system exhibited enhanced bacterial attachment and biofilm formation on cathode surfaces, which strengthened interfacial interactions. Results analysis revealed that HA could enhance bacterial metabolic activity. This work provides a safe and green route for resource recovery from waste batteries.