Tuning Sodium Occupancy Sites in P2‐Layered Cathode Material for Enhancing Electrochemical Performance. Issue 13 (24th February 2021)

• Record Type: Journal Article
• Authors: Wang, Qin‐Chao; Shadike, Zulipiya; Li, Xun‐Lu; Bao, Jian; Qiu, Qi‐Qi; Hu, Enyuan; Bak, Seong‐Min; Xiao, Xianghui; Ma, Lu; Wu, Xiao‐Jing; Yang, Xiao‐Qing; Zhou, Yong‐Ning
• Is Part Of: Advanced energy materials. Volume 11:Issue 13(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-02-24
• Subjects: cathode materials -- Na+/vacancy -- P2‐structure -- sodium‐ion batteries -- X‐ray absorption spectroscopy; 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.202003455
• Languages: English
• ISSNs: 1614-6832

Abstract

Abstract: Different sodium occupancy sites in P2‐layered cathode materials can reorganize Na‐ion distribution and modify the Na + /vacancy superstructure, which have a vital impact on the Na‐ion transport and Na storage behavior during charge and discharge processes, but have not been investigated specifically and are not yet well understood. Herein, the occupancy ratio of two different Na sites (sites below transition metal ions and sites below oxygen ions along the c direction) in P2‐Na0.67 [Mn0.66 Ni0.33 ]O2 cathode is tuned successfully by inducing Sb 5+ ions with strong repulsion toward Na sites right below transition metals. It is found that the decrease of Na occupancy right below transition metal ions is beneficial to the electrochemical performance of P2‐layered cathode materials, regarding cycle stability and rate capability. In situ X‐ray absorption spectroscopy reveals that the reversible Mn 3.3+ /Mn 4+ and Ni 2+ /Ni 3+ redox couples provide charge compensation in different voltage regions of 1.8–2.3 and 2.3–4.2 V, respectively. The transmission X‐ray microscopy confirms the uniform redox reaction over the whole electrode particle. In addition, Sb substitution can suppress the "P2‐O2" phase transition in high voltage region by preventing oxygen gliding in a – b planes, thus ensuring robust structure stability during cycling. Abstract : The ratio of two different sodium occupancy sites (Nae and Naf ) in P2‐Na0.67 [Mn0.66 Ni0.33 ]O2 cathode is tuned successfully by Sb 5+ substitution. The decrease of Naf occupation breaks the Na + /vacancy ordering, makes the redox reaction over the whole electrode particles uniform, and suppresses the "P2‐O2" phase transition in the high‐voltage region, thus improving the overall electrochemical performance effectively.