Recycling the waste LiMn2O4 of spent Li-ion batteries by pH gradient in neutral water electrolyser

The rapid development of electric vehicles powered by Li-ion batteries poses a challenge for the supply of raw materials, and will also generate significant battery waste. Recycling the spent Li-ion batteries not only mitigates the pressure on resource supply but also reduces environmental pollution. Herein, we present a comprehensive study on using pH gradient generated in neutral water electrolyser for recycling waste LiMn 2 O 4 cathodes without addition of external acid, base or chemical reductant. Li + and Mn 2+ are leached from LiMn 2 O 4 at low pH in the anode chamber, and manganese oxide is precipitated at high pH in the cathode chamber. H 2 and O 2 are also valuable byproducts of the process. Li + can be recovered in the form of Li 2 CO 3 . Finally, the LiMn 2 O 4 is re-synthesized, closing the loop. The exact roles of multiple variables on the leaching of LiMn 2 O 4 as well as the associated phase evolution are carefully examined. In addition, γ -MnO 2 is deposited on the anode during the process, and it is characterized to be a stable and relatively effective catalyst for oxygen evolution reaction in acid. The process demonstrated represents a promising approach for recovering waste LiMn 2 O 4 of waste Li-ion batteries in an environmentally friendly way. • Waste LiMn 2 O 4 was recycled by pH gradient generated in neutral water electrolyser. • The leaching of waste LiMn 2 O 4 and the associated phase evolution were studied. • The γ -MnO 2 deposited on anode was acid-stable and relatively effective for catalyzing oxygen evolution reaction. • New LiMn 2 O 4 was re-synthesized, closing the loop. • This recycling method shows promise in reducing the chemical consumption and avoiding waste by-products.