Recycling the Cathode Scrap of Spent Lithium-Ion Batteries as an Easily Recoverable Peroxymonosulfate Catalyst with Enhanced Catalytic Performance

The cathode in spent lithium-ion batteries (LIBs) has intrinsic properties and a unique sandwich-like structure and contains transition metals. Moreover, the transition metal-based catalysts frequently used in sulfate radical-based advance oxidation processes (SR-AOPs) entail a complex synthesis process, expensive mass production, and difficult separation and recovery. Here, we propose that a cathode scrap from spent LIBs can be directly recycled as stable and reusable SR-AOP catalysts. Compared with pristine LiMn2O4, the catalytic performance of the recycled active LiMn2O4 component was enhanced by the prolonged lithiation/delithiation cycles in situ. As a result, the cathode scrap shows high efficiency for peroxymonosulfate (PMS) activation, and the ortho-phenylphenol (OPP) degradation still reached 94.8% after 10 cycles. Multiple important properties of the recycled cathode scrap, such as the oxidation state, surface oxygen species, pore structure, and structure factors, were investigated in details. The pore in the coating further offers the chances for PMS to efficiently make contact with the interior active LiMn2O4 and allow for the aqueous solution to diffuse to the interior Al foil, caused subsequently by the redox reaction of the Al foil. The synergistic effect between the Al foil and LiMn2O4-containing coating promotes the conversion of Mn(IV) to Mn(III) and electron transfer. The strong adhesion between the LiMn2O4-containing coating and Al foil through the binder enhances catalyst stability and endow the cathode scrap catalyst with easily recoverable characteristics. This work offers an attractive method for the recycling of spent LIBs and development of catalysts in SR-AOPs.