Fe 2 O 3 Catalysts Activating Size‐Regulated Li 2 C 2 O 4 for Efficient Cathode Prelithiation in Li Ion Hybrid Capacitors

Prelithiation is a strategy to address the active lithium loss in Li ion hybrid capacitors (LICs) during initial charge–discharge process. Lithium oxalate (Li 2 C 2 O 4 ) emerges as a promising prelithiation additive due to its high lithium content and superior atmospheric stability. However, its practical application is hindered by sluggish reaction kinetics and a high decomposition potential. Herein, we develop a Li 2 C 2 O 4 recrystallization strategy combined with Fe 2 O 3 catalysts (R‐LCO@Fe 2 O 3 ), enhancing the electrochemical activity of Li 2 C 2 O 4 and lowering its decomposition potential from approximately 4.76 to 4.28 V vs . Li + /Li. Also, the designed prelithiation additive facilitates the formation of a LiF‐rich and compact solid electrolyte interphase, which is beneficial for extending the cycling lifespan of LICs. In activated carbon//graphite LICs, the R‐LCO@Fe 2 O 3 additive increases the initial charge capacity to 288.27 mAh g −1 , while the discharge capacity is significantly improved from 23.67 to 42.15 mAh g −1 . As a result, LICs incorporating R‐LCO@Fe 2 O 3 exhibit stable cycling performance over 2500 cycles, with a capacity retention of 75.93%. In contrast, the LICs without additives suffer a more rapid capacity fade, retaining 31.59% after 325 cycles. Overall, this work demonstrates a simple, cost‐effective, and scalable strategy for preparing prelithiation materials in LIC applications.