A strategy for the synthesis of three-dimensional (3D) porous VO₂(B) hierarchical spheres with different interiors (solid spheres and hollow spheres) was developed by a template-free method. 3D VO₂(B) solid spheres were synthesized by the precipitation of precursor spheres at room temperature and subsequent calcination, while 3D VO₂(B) hollow spheres were prepared by the hydrothermal treatment of precursor spheres and subsequent calcination. BET specific surface areas of VO₂(B) solid spheres and hollow spheres were measured to be 18 and 29 m² g⁻¹, respectively, and their porosity varied from mesoporous to macroporous with hierarchical structures. Electrochemical properties of 3D porous VO₂(B) hierarchical spheres were studied by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS). As electrode materials, the specific capacitances of 3D VO₂(B) hollow spheres and solid spheres reach as high as 1175 mF cm⁻² (336 F g⁻¹) and 951 mF cm⁻² (272 F g⁻¹) at 2 mA cm⁻², respectively. After 10 000 cycles, the capacitance retention of about 68% and 49% was observed for VO₂(B) hollow spheres and solid spheres, respectively. Furthermore, symmetric supercapacitor (SSC) devices using VO₂(B) hollow spheres and VO₂(B) solid spheres were assembled, and they exhibited good pseudocapacitive properties. VO₂(B) hollow sphere-SSC device delivered an areal capacitance of 246 mF cm⁻² at 1 mA cm⁻², while VO₂(B) solid sphere-SSC device delivered an areal capacitance of 122 mF cm⁻² at 1 mA cm⁻². VO₂(B) hollow spheres exhibit better electrochemical properties, including specific capacitance, areal energy density and cycling stability, compared with those of VO₂(B) solid spheres. The findings in this work demonstrate that 3D porous VO₂(B) hierarchical spheres with different interiors can improve the electrochemical properties of VO₂(B) and can be considered promising candidates for high-performance energy storage materials.

中文翻译：

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可控合成具有不同内部空间的3D多孔VO ₂（B）分层球体†

通过无模板方法开发了一种合成具有不同内部空间的三维（3D）多孔VO ₂（B）分层球的策略（实心球和空心球）。通过在室温下沉淀前体球并随后煅烧来合成3D VO ₂（B）固体球，而通过对前体球进行水热处理和随后的煅烧来制备3D VO ₂（B）空心球。VO ₂（B）固体球和空心球的BET比表面积经测量分别为18和29 m ² g ^-1孔隙度从中孔到具有层状结构的大孔不等。通过循环伏安法（CV），恒电流充放电（GCD）和电化学阻抗谱（EIS）研究了3D多孔VO ₂（B）分层球的电化学性能。作为电极材料，3D VO ₂（B）空心球和实心球的比电容在_2时高达1175 mF cm ^-2（336 F g ^-1）和951 mF cm ^-2（272 F g ^-1）。分别为mA cm ^-2。10000次循环后，VO ₂的电容保持率分别约为68％和49％（B）分别为空心球和实心球。此外，组装了使用VO ₂（B）空心球和VO ₂（B）实心球的对称超级电容器（SSC）器件，它们显示出良好的伪电容特性。VO ₂（B）空心球-SSC装置递送的246μF的厘米的面积电容^-2在1mA厘米^-2，而VO ₂（B）固体球体-SSC装置递送的122μF的厘米的面积电容^-2 1 mA cm ^-2。VO ₂（B）空心球表现出更好的电化学性质，包括具体的电容，分布区的能量密度和循环稳定性，与VO相比₂（B）实心球。这项工作中的发现表明，具有不同内部结构的3D多孔VO ₂（B）分层球可以改善VO ₂（B）的电化学性能，可以被认为是高性能储能材料的有希望的候选者。