High-precision analysis of toxic metals in lithium-ion battery materials across various complex media

Background

Present regulations regarding the management and recycling of spent Lithium-ion batteries (LIBs) are inadequate, which may lead to the pollution of lithium (Li) and heavy metals in water and soil during the informal disposal of such batteries. To comprehend the distribution of toxic metals within spent LIBs and contaminated environmental media, precise analytical methods for toxic metals in these materials are crucial. However, due to the chemical complexity of LIBs materials (e.g., lithium iron phosphate, graphite, separators, and electrolytes), there is still a lack of research on developing and validating analytical techniques for toxic metals in LIB materials across various environmental media.

Results

This study establishes a comprehensive and highly precise analytical method for assessing toxic metal constituents in LIBs across various complex media, including sewage, soil, and biological matrices. We assessed the selection of digestion solutions for different LIB materials and identified the most suitable internal standard elements in the mass spectrometric analysis workflow. The devised digestion schemes for all components of LIBs are as follows: aqua regia for all cathode materials (excluding LiMn_0.6Fe_0.4PO₄ (LMFP)), nitric acid for diaphragm materials, aqua regia with hydrofluoric acid for the anode material Li₄Ti₅O₁₂ (LTO), and NaOH fusion for graphite and LMFP. LiPF₆ electrolyte can be directly dissolved in ultrapure water. By employing this method, the analysis of cathode materials of LIBs within diverse environmental matrices (sewage, soil, plants, animals) yields recovery rates ranging from 83.6 % to 115.5 %. Furthermore, this research reveals the remarkable accumulation of Li and heavy metals in anode (graphite) of spent LIBs.

Significance

This is the first to develop and validate analytical techniques for toxic metals in LIB materials across various environmental media, incorporating both acid digestion and alkaline fusion techniques. This methodology offers comprehensive support for conducting environmental risk assessments of spent LIBs. Using this method, the research elucidates the occurrence characteristics of toxic metals within different parts of commercial spent LIBs, providing valuable insights to enhance recycling efforts and facilitate risk management of spent LIBs.