Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, and School of Materials Science and Engineering, Jilin University, Changchun, 130022, China.
Beijing National Laboratory for Condensed Matter Physics, The Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
Nat Commun. 2018 Apr 10;9(1):1375. doi: 10.1038/s41467-018-03700-3.
Pseudocapacitance holds great promise for improving energy densities of electrochemical supercapacitors, but state-of-the-art pseudocapacitive materials show capacitances far below their theoretical values and deliver much lower levels of electrical power than carbon-based materials due to poor cation accessibility and/or long-range electron transferability. Here we show that in situ corundum-to-rutile phase transformation in electron-correlated vanadium sesquioxide can yield nonstoichiometric rutile vanadium dioxide layers that are composed of highly sodium ion accessible oxygen-deficiency quasi-hexagonal tunnels sandwiched between conductive rutile slabs. This unique structure serves to boost redox and intercalation kinetics for extraordinary pseudocapacitive energy storage in hierarchical isomeric vanadium oxides, leading to a high specific capacitance of ~1856 F g (almost sixfold that of the pristine vanadium sesquioxide and dioxide) and a bipolar charge/discharge capability at ultrafast rates in aqueous electrolyte. Symmetric wide voltage window pseudocapacitors of vanadium oxides deliver a power density of ~280 W cm together with an exceptionally high volumetric energy density of ~110 mWh cm as well as long-term cycling stability.
赝电容在提高电化学超级电容器的能量密度方面具有巨大的潜力，但最先进的赝电容材料的电容远低于其理论值，并且由于阳离子可及性差和/或长程电子迁移率低，其提供的电力水平比基于碳的材料低得多。在这里，我们表明，电子相关的三氧化二钒中尖晶石到金红石的原位相变可以产生非化学计量的金红石氧化钒层，该层由高度钠离子可及的氧缺陷类六方隧道夹在导电金红石片之间组成。这种独特的结构有助于提高氧化钒的氧化还原和嵌入动力学，从而在分层同构氧化钒中实现非凡的赝电容储能，比原始的三氧化二钒和二氧化钒的比电容高约 1856 F g（几乎是其六倍），在水溶液电解质中以超快速率具有双极性充放电能力。氧化钒的对称宽电压窗口赝电容器的功率密度约为 280 W cm，同时具有极高的体积能量密度约 110 mWh cm，以及长期循环稳定性。
