通过两步微波和离子交换的方法得到一种直径约为 1.5 μm 的微球形貌铜离子掺杂钒基配位聚合物 (V-Cu-HHTP). 聚合物中部分取代的 Cu$^{2+}$提高了配位聚合物的导电性和结构稳定性, 并提供 V、Cu 的协同效应, 在用于超级电容器电极材料时表现出良好的电化学性能. 在 1 A$\cdot$g$^{-1}$ 的电流密度下, V-Cu-HHTP 表现出 287 F$\cdot$g$^{-1}$ 的比容量, 在 10 A$\cdot$g$^{-1}$ 的大电流密度下循环 3 000 圈后, V-Cu-HHTP 的电容保持率仍有 98.6%, 比相同测试条件下未掺杂的 V-HHTP 电极表现优异 (比容量为 227 F$\cdot$g$^{-1}$, 电容保持率为 94.2%). 选取 V-Cu-HHTP 作为正极, 活性炭 (activated carbon, AC) 作为负极, 组装非对称超级电容器 V-Cu-HHTP//AC, 电压窗口达到 1.6 V. V-Cu-HHTP//AC 在功率密度为 795.0 W$\cdot$Kg$^{-1}$ 时, 最大能量密度为44.1 Wh$\cdot$Kg$^{-1}$, 优于许多钒基超级电容器. 优异的电化学性能归因于: 双金属配位聚合物的设计为体系提供了优异的协同效应, 提高了结构稳定性; Cu 离子掺杂提高了导电性; V-Cu-HHTP 的多孔特征为体系暴露更多活性位点, 提供优异的双电层电容特性.

The microspheres of copper-ion-doped vanadium-based coordination polymers (V-Cu-HHTP) with diameters of approximately 1.5 μm are prepared through two steps of microwave treatment. The introduction of Cu$^{2+}$ is achieved by cation exchange and is assumed to improve electronic conductivity and provide the synergic effect derived from the bimetallic feature of the vanadium-based coordination polymers. Results show that the V-Cu-HHTP exhibit good specific capacitance and cycle stability when used as electrode materials in supercapacitors. More specifically, V-Cu-HHTP show a capacitance of287 F$\cdot$g$^{-1}$ at 1 A$\cdot$g$^{-1}$ and have a 98.6% capacitance retention of 10 A$\cdot$g$^{-1}$ after 3 000 charging--discharging cycles. In comparison, the V-HHTP electrode shows a lower specific capacitance of 227 F$\cdot$g$^{-1}$ at 1 A$\cdot$g$^{-1}$ with a 94.2% capacitance retention of 10 A$\cdot$g$^{-1}$. An asymmetric supercapacitor is assembled with the V-Cu-HHTP as a cathode and activated carbon (AC) as an anode (denoted as V-Cu-HHTP//AC). The assembled V-Cu-HHTP//AC device can achieve a potential window of 1.6 V, and the energy density is as high as 44.1 Wh$\cdot$Kg$^{-1}$ when the power density is 795.0 W$\cdot$Kg$^{-1}$. We attribute these excellent electrochemical properties to the following. First, the bimetal-based coordination polymer provides an excellent synergistic effect derived from the two metallic elements. Second, Cu doping improves the electronic conductivity and structural stability of the vanadium-based coordination polymers. The porous characteristics of V-Cu-HHTP provide numerous active sites to the electrode, thus leading to improved energy storage properties.