A Fluorination Method for Improving Cation‐Disordered Rocksalt Cathode Performance. Issue 35 (28th July 2020)

• Record Type: Journal Article
• Authors: Ahn, Juhyeon; Chen, Dongchang; Chen, Guoying
• Is Part Of: Advanced energy materials. Volume 10:Issue 35(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-07-28
• Subjects: cation‐disordered rocksalt cathodes -- fluorinated polymeric precursors -- fluorination -- lithium‐ion batteries -- oxygen redox; Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.202001671
• Languages: English
• ISSNs: 1614-6832

Abstract

Abstract: In Li‐rich cation‐disordered rocksalt oxide cathodes (DRX), partial fluorine substitution in the oxygen anion sublattice can increase the capacity contribution from transition‐metal (TM) redox while reducing that from the less reversible oxygen redox. To date, limited fluorination substitution has been achieved by introducing LiF precursor during the solid‐state synthesis. To take full advantage of the fluorination effect, however, a higher F content is desired. In the present study, the successful use of a fluorinated polymeric precursor is reported to increase the F solubility in DRX and the incorporation of F content up to 10–12.5 at% into the rocksalt lattice of a model Li‐Mn‐Nb‐O (LMNO) system, largely exceeding the 7.5 at% limit achieved with LiF synthesis. Higher F content in the fluorinated‐DRX (F‐DRX) significantly improves electrochemical performance, with a reversible discharge capacity of ≈255 mAh g −1 achieved at 10 at% of F substitution. After 30 cycles, up to a 40% increase in capacity retention is achieved through the fluorination. The study demonstrates the feasibility of using a new and effective fluorination process to synthesize advanced DRX cathode materials. Abstract : Cation‐disordered Li‐excess rocksalts are promising high‐energy and cobalt‐free cathode materials for next‐generation lithium‐ion batteries. This study reports a new and effect fluorination method that utilizes a fluorinated polymer precursor, alternative to the commonly used LiF precursor, to increase F solubility in the rocksalt lattice. Advanced materials with much improved cathode performance are developed.