ラジカル駆動表面予酸化による使用済みナトリウムイオン電池正極材の効率的な再生

The escalating accumulation of retired sodium-ion batteries (SIBs) has rendered efficient recycling a pressing imperative. Direct regeneration presents a compelling solution due to economic viability and high value-added output. However, severe surface degradation of spent cathode materials impedes Na⁺ replenishment, compromising regeneration efficacy. Herein, a novel pre-oxidation strategy is proposed that capitalizes on water-triggered Na⁺/H⁺ exchange in spent cathodes to establish an alkaline environment, which catalyzes the decomposition of Na₂S₂O₈ to generate highly reactive SO₄ ^-· and ·OH radicals. The potent radicals drive surface reconstruction from rock-salt phase into a Ni³⁺-layered configuration, optimizing Na⁺ transport channels. Furthermore, the treatment refines particle morphology and eliminates residual aluminum and fluoride impurities, enhancing interfacial reaction homogeneity, thereby enabling efficient solid-state regeneration. As a result, the pre-oxidation regenerated NaFe_1/3Mn_1/3Ni_1/3O₂ cathode exhibits an initial capacity of 134.33 mAh g^-1 and superior cycling stability with 84.4% retention after 150 cycles at 0.5 C, restoring performance comparable to commercial counterparts. This study provides an innovative and integrated strategy for efficient regeneration of highly degraded cathode materials.