# Ultrasound enhances the recycling process and mechanism of lithium from spent LiFePO4 batteries by Acidithiobacillus ferrooxidans

## TL;DR

This study shows how ultrasound and a specific bacteria can efficiently recover lithium from old batteries.

## Contribution

The novel use of ultrasound with Acidithiobacillus ferrooxidans improves lithium leaching efficiency and reduces processing time.

## Key findings

- Ultrasound and microbial action together increased lithium leaching to 99.7%.
- Leaching time was reduced from 7 to 5 days using the new method.
- Contact leaching was confirmed as the main mechanism via filter bag experiments.

## Abstract

In this study, the ability of Acidithiobacillus ferrooxidans to oxidize Fe2+ to Fe3+ and recover battery black powder was investigated, establishing a system for leaching decommissioned lithium iron phosphate battery black powder from A. ferrooxidans. Black powder reduced the consumption of reagents and subsequent pressure for treating iron-bearing minerals using the iron source in waste LiFePO4 batteries. This study used ultrasonic waves to remove impurities on the surface and cracks in battery black powder, hindering the dissolution layer and enhancing the leaching effect through a cavitation reaction and microbial activation to promote the leaching process. A filter bag experiment was designed using the selective permeability of filter bags to investigate whether the leaching mechanism of A. ferrooxidans lithium iron phosphate is contact or non-contact. Under optimal leaching conditions, the lithium leaching rate reached 99.7%, and the leaching time was reduced from 7 to 5 days, achieving efficient leaching of lithium. The filter bag experiment concluded that A. ferrooxidans leaching of lithium iron phosphate was mainly a contact leaching mechanism.