Phytoremediation of Soil Contaminated with Lithium Ion Battery Active Materials—A Proof-of-Concept Study

The lithium-ion battery is the most powerful energy storage technology for portable and mobile devices. The enormous demand for lithium-ion batteries is accompanied by an incomplete recycling loop for used lithium-ion batteries and excessive mining of Li and transition metals. The hyperaccumulation of plants represents a low-cost and green technology to reduce environmental pollution of landfills and disused mining regions with low environmental regulations. To examine the capabilities of these approaches, the hyperaccumulation selectivity of Alyssum murale for metals in electrode materials (Ni, Co, Mn, and Li) was evaluated. Plants were cultivated in a conservatory for 46 days whilst soils were contaminated stepwise with dissolved transition metal species via the irrigation water. Up to 3 wt% of the metals was quantified in the dry matter of different plant tissues (leaf, stem, root) by means of inductively coupled plasma-optical emission spectroscopy after 46 days of exposition time. The lateral distribution was monitored by means of micro X-ray fluorescence spectroscopy and laser ablation-inductively coupled plasma-mass spectrometry, revealing different storage behaviors for low and high metal contamination, as well as varying sequestration mechanisms for the four investigated metals. The proof-of-concept regarding the phytoextraction of metals from LiNi_0.33Co_0.33Mn_0.33O₂ cathode particles in the soil was demonstrated.