CAS Key Laboratory of Materials for Energy Conversion, Shanghai Institute of Ceramics , Chinese Academy of Sciences , Shanghai 200050 , P. R. China.
University of Chinese Academy of Sciences , Beijing 100049 , P. R. China.
ACS Appl Mater Interfaces. 2019 Feb 6;11(5):5123-5128. doi: 10.1021/acsami.8b20112. Epub 2019 Jan 24.
The vanadium boride (VB) air battery is currently known as a primary battery with the highest theoretical specific capacity, 4060 mA h g, which originates from an extraordinary 11 electrons per VB molecule oxidation process. However, the parasitical reaction between VB 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 VB 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 VB in the open circuit to avoid corrosion but also ensured that the hydroxide ions can enter the VB particle surface to participate in the reaction during discharge. According to the corrosion suppression test, the remaining amount of VB@PDA is 90 wt % stored at 65 °C for 2 weeks, which is 10 wt % more than the uncoated VB. The assembled pouch cell with the VB@PDA anode can deliver a high capacity of 325 mA h at 250 mA g, retaining an improved Coulombic efficiency of 86.3%, which is 18.7% higher than that of the cell with the raw VB anode. Moreover, the 0.05 V higher discharge voltage of the VB@PDA-based cell further shows that the PDA membrane can effectively conduct hydroxide ions during discharge.
氮化硼（VB）空气电池目前被认为是理论比容量最高的原电池，可达 4060 mA h g，源于 VB 分子非凡的 11 电子每 VB 分子氧化过程。然而，VB 与碱性电解质中氢氧根离子之间的寄生反应导致明显的自放电，从而导致在放电过程中严重的容量损失。在这项工作中，我们应用聚多巴胺（PDA）膜对 VB 颗粒表面进行改性，PDA 膜含有伯胺基和酚羟基，表现出完全可逆的 pH 值切换选择透过性。具有 pH 值切换特性的“智能”膜成功协调了开路状态下电解质与 VB 之间的冲突，既能避免腐蚀，又能确保在放电过程中，氢氧根离子能进入 VB 颗粒表面参与反应。根据腐蚀抑制测试，在 65°C 下储存 2 周后，VB@PDA 的剩余量为 90wt%，比未包覆的 VB 多 10wt%。用 VB@PDA 作为阳极组装的软包电池可提供 325 mA h 的高容量，在 250 mA g 下，库仑效率提高到 86.3%，比原始 VB 阳极的电池提高了 18.7%。此外，VB@PDA 基电池的放电电压高出 0.05 V，进一步表明 PDA 膜在放电过程中能有效传导氢氧根离子。
