Ketjen Black-Decorated Li 2 C 4 O 4 for LiF-Rich CEI Engineering and Mn Dissolution Suppression in Long-Life LiMn 0.6 Fe 0.4 PO 4 Cathodes

The limited cycling stability of LiMn 0.6 Fe 0.4 PO 4 (LMFP) cathodes, largely attributed to manganese dissolution and unstable interfaces, restricts their application. To address this, a conductive ketjen black-modified Li 2 C 4 O 4 prelithiation agent (KB-DLS, KD) is incorporated, which is not used as a conventional prelithiation agent but as a cathode functional additive. This work indicates that CO released from the decomposition of KB-DLS can react with lattice oxygen in LMFP, reduce highly oxidizing Mn 3+, and produce CO 2 . The reduction of Mn 3+ suppresses Mn dissolution and reduces harmful species in the CEI layer caused by its strong oxidizing property. Meanwhile, the locally acidic environment generated by CO 2 promotes the formation of a dense and stable LiF-rich CEI layer. This series of synergistic optimizations endows KD-LMFP with superior ion transport kinetics and excellent electrochemical performance. Consequently, the optimized KD-LMFP cathode delivers substantially improved capacity retention of 83.1% after 500 cycles at 1 C in half-cells (vs. 67.7% for bare LMFP) and superior rate capability. Meanwhile, the KD-LMFP‖graphite full cell achieves 98.4% capacity retention after 500 cycles at 1 C. This study provides a facile interfacial engineering strategy using a functional additive to develop high-performance, long-life LMFP cathodes.