Uniform Na3V2(PO4)2O2F microcubes enhanced by ionic liquid-modified multi-walled carbon nanotubes as a superior cathode for Sodium-Ion Batteries

• Published in: Electrochimica acta 2023-01, Vol.439, p.141671, Article 141671
• Main Authors: Yan, Rui-Bo, Zhan, Guang-Hao, Liao, Wen-Hua, Hu, Qian-Qian, Huang, Xiao-Ying, Wu, Xiao-Hui
• Format: Article
• Language: English
• Subjects: Ionic liquids; Multi-walled carbon nanotubes; Na3V2(PO4)2O2F; NASICON structure; Sodium-ion battery
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2022.141671

Na3V2(PO4)2O2F with a typical Na+ superionic conductor (NASICON) structure is a promising cathode material for sodium-ion batteries (SIBs) due to its unique layered structure, high energy density and fast ionic conductivity. However, the low intrinsic electronic conductivity seriously hinders the practical application of Na3V2(PO4)2O2F. In this work, ionic liquid-modified multi-walled carbon nanotubes (MWCNT-IL) were applied as a conductive network to form Na3V2(PO4)2O2F-based cathode. The highly dispersed MWCNT-IL can hinder the agglomeration growth of Na3V2(PO4)2O2F crystal and can result in the formation of uniform Na3V2(PO4)2O2F cubes of ∼1 μm which are covered evenly by conductive MWCNT-IL through COP/V bonds (denoted as NVOPF@MWCNT-IL). Relying on the synergistic effect of conductive MWCNT-IL and uniform Na3V2(PO4)2O2F cubes, NVOPF@MWCNT-IL cathode for SIBs can exhibit improved cycling stability and superior rate performance. The specific capacity of NVOPF@MWCNT-IL can reach 107 mA h g−1 with high retention of 96.7% after 900 cycles at a current density of 1C (1C=130 mA h g−1). At a high current density of 30C, NVOPF@MWCNT-IL maintains a high discharge capacity of 79 mA h g−1 after 1500 cycles. The above results provide an effective and simple method to construct advanced NASICON cathodes for SIBs. [Display omitted]