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ACS Appl Mater Interfaces. 2019 Feb 6;11(5):5123-5128. doi: 10.1021/acsami.8b20112. Epub 2019 Jan 24.

Suppressing Self-Discharge of Vanadium Diboride by Zwitterionicity of the Polydopamine Coating Layer.

Wang F1,2, Wu M1,2, Zhang T3,2, Wen Z1,2.

Author information

1
CAS Key Laboratory of Materials for Energy Conversion, Shanghai Institute of Ceramics , Chinese Academy of Sciences , Shanghai 200050 , P. R. China.
2
University of Chinese Academy of Sciences , Beijing 100049 , P. R. China.
3
State Key Lab of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics , Chinese Academy of Sciences , 1295 Dingxi Road , Shanghai 200050 , P. R. China.

Abstract

The vanadium boride (VB2) air battery is currently known as a primary battery with the highest theoretical specific capacity, 4060 mA h g-1, which originates from an extraordinary 11 electrons per VB2 molecule oxidation process. However, the parasitical reaction between VB2 and hydroxide ions in the alkaline electrolyte leads to obvious self-discharge, which results in severe capacity loss during discharge. In this work, we applied the polydopamine (PDA) membrane to modify the surface of VB2 particles, which contains amine groups and phenolic hydroxyl groups exhibiting fully reversible, pH-switchable permselectivity. The "smart" membrane with pH-switching characteristics successfully coordinated the conflict between the electrolyte and VB2 in the open circuit to avoid corrosion but also ensured that the hydroxide ions can enter the VB2 particle surface to participate in the reaction during discharge. According to the corrosion suppression test, the remaining amount of VB2@PDA is 90 wt % stored at 65 °C for 2 weeks, which is 10 wt % more than the uncoated VB2. The assembled pouch cell with the VB2@PDA anode can deliver a high capacity of 325 mA h at 250 mA g-1, retaining an improved Coulombic efficiency of 86.3%, which is 18.7% higher than that of the cell with the raw VB2 anode. Moreover, the 0.05 V higher discharge voltage of the VB2@PDA-based cell further shows that the PDA membrane can effectively conduct hydroxide ions during discharge.

KEYWORDS:

VB2 anode; pH-switching characteristics; self-discharge; the polydopamine (PDA) membrane; vanadium diboride air battery

PMID:
30633494
DOI:
10.1021/acsami.8b20112

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