Green upcycling of spent Li-ion battery cathode via transient thermal defluorination

Abstract

The direct regeneration of end-of-life lithium-ion batteries (LIBs) is a promising avenue for achieving sustainability in the electric vehicle industry. However, it is challenging to separate cathode material intact from a highly reactive aluminum (Al) foil firmly bonded with polyvinylidene fluoride (PVDF), often resulting in the downgraded recovery in their elemental form. Herein, we develop a non-destructive stripping strategy enabling the simplest solid-phase sintering to upcycle spent LiCoO₂ cathodes into new electrode materials. Specifically, we introduce an alkaline medium to modify the carbothermal-shock (CTS) method, where acts as a temperature buffer to minimize lithium loss to 1.76 %; as a catalyst to induce PVDF deactivation by oxidative dehydrogenation; and as a trapping agent to absorb up to 98 % of HF gas with acid-base neutralization. This improved CTS strategy allows for instantaneous stripping of ∼95 % of LiCoO₂ cathodes (∼900 °C and ∼1 s) with the separated Al foil remaining in its zero-valent state, which has also demonstrated effectiveness with waste LiFePO₄ and LiNi_0.6Co_0.2Mn_0.2O₂ cathodes. Due to the well-preserved crystal structure and unobstructed lithium replenishment channels, the regenerated LiCoO₂ cathodes easily regain excellent electrochemical cycling performance. All these efforts have contributed to a 52.74 % reduction in carbon footprint compared to conventional pyrometallurgy processes.