Water‐Stabilized Vanadyl Phosphate Monohydrate Ultrathin Nanosheets toward High Voltage Al‐Ion Batteries

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 19; no. 18; pp. e2207619 - n/a
• Main Authors: Zheng, Jiening, Xu, Tian, Xia, Guanglin, Cui, Wen‐Gang, Yang, Yaxiong, Yu, Xuebin
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.05.2023
• Subjects: aluminum ion batteries; Batteries; Bonding strength; Cycles; Diffusion rate; Discharge; high discharge potential; high water stability; Nanosheets; Nanotechnology; Performance degradation; Steric hindrance; VOPO 4·H 2O; VOPO 4·H 2O@MXene; Water chemistry; high water stability; VOPO 4·H 2O@MXene; VOPO 4·H 2O; aluminum ion batteries; high discharge potential
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.202207619

Al ion batteries (AIBs) are attracting considerable attention owing to high volumetric capacity, low cost, and high safety. However, the strong electrostatic interaction between Al3+ and host lattice leads to discontented cycling life and inferior rate capability. Herein, a new strategy of employing water molecules contained VOPO4·H2O to boost Al3+ migration via the charge shielding effect of water is reported. It is revealed that VOPO4·H2O with water lubrication effect and smaller steric hindrance owns high capacity and fast Al3+ diffusion, while the loss of unstable water upon cycling leads to a rapid performance degradation. To address this problem, ultrathin VOPO4·H2O@MXene nanosheets are fabricated via the formed TiOV bond between VOPO4·H2O and MXene. The MXene aided exfoliation results in enhanced VOwater bond strength between H2O and VOPO4 that endows the obtained composite with strong water holding ability, contributing to the extraordinary cycling stability. Consequently, the VOPO4·H2O@MXene delivers a high discharge potential of 1.8 V and maintains discharge capacities of 410 and 374.8 mAh g−1 after 420 and 2000 cycles at the current densities of 0.5 and 1.0 A g−1, respectively. This work provides a new understanding of water‐contained AIBs cathodes and vital guidance for developing high‐performance AIBs. The water lubrication effect for Al3+ diffusion is uncovered using VOPO4·nH2O (n = 0, 1, 2) as model. The water stability of VOPO4·H2O is enhanced via hybridization with MXene, which can strengthen the VOwater bond via introduction of the abundant oxygen vacancies. The resulted VOPO4·H2O@MXene owns high capacity and excellent cycling stability.