Continuous Flow Electrochemical Synthesis of Olivine‐Structured NaFePO4 Cathode Material for Sodium‐Ion Batteries from Recycle LiFePO4

Abstract To mitigate the environmental impact of the improper disposal of spent LiFePO 4 batteries and reduce resource waste, the development of LiFePO 4 recycling technologies is of paramount importance. Meanwhile, olivine‐structured NaFePO 4 in sodium‐ion batteries has received great attention, due to its high theoretical specific capacity of 154 mAh g −1 and excellent stability. However, olivine NaFePO 4 only can be synthesized from olivine LiFePO 4 . Accordingly, in this proposal, developing the continuous flow electrochemical solid‐liquid reactor‐based metal ion insertion technology is to utilize the olivine FePO 4 , recycled from LiFePO 4 , and to synthesize NaFePO 4 . Additionally, by employing I − as the reducing agent, NaFePO 4 is successfully synthesized with a discharge‐specific capacity of 134 mAh g −1 at 0.1C and a remarkable capacity retention rate of 86.5% after 100 cycles at 0.2C. And the reasons for sodium deficiency in the synthesized NFP are elucidated through first‐principles calculations. Furthermore, the kinetics of the solid‐solution reaction 2 (Na 2/3+β PO 4 → Na 1‐α FePO 4 ) mechanism improve with cycling and are sensitive to temperature. Utilizing a minimal amount of reducing agent in the electrochemical reactor, NaFePO 4 synthesis is successfully achieved. This innovative approach offers a new, cost‐effective, and environmentally friendly strategy for preparing NaFePO 4 from recycling LiFePO 4 .