Ion-Electron Coupling Strategy Induced by Interface Electric Field Enables High-Performance LiFePO₄ From Spent...

The direct regeneration of spent LiFePO₄ (LFP) is primarily constrained by the high energy barriers for concurrent Li⁺ and electron transport, which has rarely been systematically addressed. Herein, an ion-electron coupling (IEC) strategy is proposed, driven by an interfacial electric field (IEF), to achieve coordinated Li⁺ and electron flow, thereby overcoming these transport barriers. The strategy of constructing localized boron-carbon (B-C) dipoles clothing on the LFP surface establishes a work function (W_F) gradient with the exterior lower than the interior. This unique gradient drives spontaneous electron flow from the C@B to the LFP to form a directional IEF that simultaneously establishes efficient Li⁺ transport pathways. This synergistic process significantly lowers the energy barriers for both carriers, ensuring ample Li⁺ and electron supply for effective regeneration. Moreover, the IEF is maintained in the regenerated LFP, which also ensures rapid Li⁺ and electron transport and leads to the excellent electrochemical performance of the regenerated LFP, with an outstanding rate capacity of 111.4 mAh g^{- 1} at 10 C, a capacity retention of 86.6% after 1000 cycles at 1 C. This work provides a novel and universal strategy to upgrade the LFP cathode from spent lithium-ion batteries.