Direct Regeneration of Industrial LiFePO4 Black Mass Through A Glycerol-Enabled Granule Reconstruction Strategy

Abstract

With the increasing sales of electric vehicles, lots of spent lithium-ion batteries (LIBs) assembled with LiFePO₄ (LFP) cathodes will retire in the next few years, posing a significant challenge for their effective and environmentally-friendly recycling. The main reason why spent LFP cathodes fail to re-utilize lies in the lattice defects caused by lithium loss and structural defects resulting from stress accumulation. In this work, we propose an in situ granule reconstruction strategy to directly regenerate spent LFP black mass (S−BM) using glycerol in industry settings. The hydroxyl groups abundant in glycerol serves as electron donor that help reduce Fe (III) and repair Fe−Li antisite defects (Fe_Li). Additionally, the chelating properties of glycerol intervene with structurally disintegrated particles, inhibiting Oswald ripening effect and promoting bonding of grain boundaries to generate lamellar microcrystals with homogeneous grain size, recover their morphology and crystal structure after a facile annealing procedure. Furthermore, the regenerated LFP restores Fe−O bonds which further inhibits structural distortion and improve Li⁺ migration kinetics. As a result, the regenerated industrial LFP black mass (R−BM) exhibits superior lithium storage performance with a discharge capacity of 123.2 mA h g⁻¹ after 500 cycles at 5.0 C (a capacity retention rate of 93.1 %).