Improved Electrode Reversibility of Nanosized Li_1.15Nb_0.15Mn_0.7O₂ through Li₃PO₄ Integration

Abstract

A lithium-excess cation-disordered rocksalt oxide, Li1.15Nb0.15Mn0.7O2, is synthesized and tested as positive electrode materials for battery applications. Although nanosized Li1.15Nb0.15Mn0.7O2 delivers a large reversible capacity using cationic/anionic redox reaction, the inferior capacity retention hinders its use for practical applications. Such degradation of electrode reversibility, including electrochemical and structural reversibility, is anticipated to originate from the gradual oxygen loss for the electrode materials with anionic redox. Herein, Li3PO4 is integrated into Li1.15Nb0.15Mn0.7O2 by high-energy mechanical milling, and 7 mol% Li3PO4 integrated Li1.15Nb0.15Mn0.7O2, Li1.2P0.06Nb0.13Mn0.61O2, shows much improved cyclability when compared with the sample without Li3PO4. Approximately 80% of reversible capacity is retained after 100cycle test at a rate of 200 mA g -1 . Moreover, electrode kinetics are significantly improved by Li3PO4 integration, and Li1.2P0.06Nb0.13Mn0.61O2 delivers a discharge capacity of 200 mA h g -1 at a rate of 640 mA g -1 . Li1.2P0.06Nb0.13Mn0.61O2 also shows improved thermal stability at elevated temperatures. From these results, the effectiveness of Li3PO4 integration into nanosized disordered rocksalt oxides with anionic redox is discussed, and this finding leads to the development of metastable high-capacity positive electrode materials for advanced Li-ion batteries.

A methodology to synthesize easily oxidized materials containing Li ions in an inert atmosphere

“…, V 3+ /V 5+ , Cr 3+ /Cr 6+ , Mo 3+ /Mo 6+ and Mn 3+ /Mn 4+ with oxygen redox (O 2− /O n − ). 13–17 For instance, nanosized Li 8/7 V 4/7 Ti 2/7 O 2 , which is a solid solution oxide between LiVO 2 and Li 1.33 Ti 0.67 O 2 (Li 2 TiO 3 ), has been recently proposed as a potential positive electrode material. 18 Nanosized Li 8/7 V 4/7 Ti 2/7 O 2 delivers a reversible capacity of 300 mA h g −1 based on V 3+ /V 5+ two-electron redox with excellent reversibility and no capacity fading.…”