基于三维多孔活性炭构筑安全、高性能以及长循环寿命的锌离子混合电容器

可充电水系锌离子电池因成本低、环境友好等优点,已经成为目前电化学储能领域的研究热点之一。然而锌离子电池中高容量、长循环寿命的阴极材料的开发仍然是一大难题。为了解决这一问题,本文中通过直接利用锌片做阳极和集流体,采用高比表面积的三维多孔活性炭(3DAC)做阴极构筑了一种锌离子混合电容器(ZIHC)。该ZIHC器件表现出了优异的电化学性能,具有目前文献报道的ZIHC最高的213 mAh·g~(-1)比容量,展示出164Wh·kg~(-1)的高能量密度和9.3kW·kg~(-1)的高功率密度以及优异的循环稳定性(10 A·g~(-1)下循环20000圈之后,容量保持率为90%,库伦效率接近100%)。我们认为这种采用高比表、三维多孔活性炭(3DAC)做阴极构筑的安全、高性能以及长寿命的水系锌离子混合电容器将为下一代高性能储能器件的开发提供新的研究思路。

A Safe,High-Performance,and Long-Cycle Life Zinc-Ion Hybrid Capacitor Based on Three-Dimensional Porous Activated Carbon

The rapid development of electronic products has increased the demand for safe, low-cost, and high-performance energy storage devices. Lithium-ion batteries have been commercialized owing to their high energy density. However, the limited lithium resources and their uneven distribution have triggered the search for alternative energy storage systems. In this context, rechargeable aqueous zinc-ion batteries have gained immense attention owing to their low cost and environmental friendliness. Nevertheless, it is highly challenging to develop zinc-ion battery cathode materials with both high capacity and long cycle life. Hence, in this study, we prepared three-dimensional porous activated carbon (3DAC) with high specific surface area by using ethylenediaminetetraacetic acid (EDTA) tetrasodium salt hydrate as the raw material. We developed a zinc-ion hybrid capacitor (ZIHC) in 1 mol∙L⁻¹ ZnSO₄ using 3DAC as the cathode and a zinc foil as the anode. The ZIHC stored charge by the reversible deposition/dissolution of Zn²⁺ on the zinc anode and rapid reversible adsorption/desorption of ions on the 3DAC cathode. Owing to the large specific surface area and highly porous structure of the 3DAC cathode, the assembled ZIHC exhibited excellent electrochemical performance. It worked well over the voltage range of 0.1–1.7 V, providing a high specific capacitance of 213 mAh·g⁻¹ at the current density of 0.5 A·g⁻¹ (the highest value reported till date). The ZIHC showed specific capacities of 182, 160, 139, 130, 127, 122, and 116 mAh·g⁻¹ at the current densities of 1, 2, 4, 6, 8, 10, and 20 A·g⁻¹, respectively. Meanwhile, it exhibited the highest energy density of 164 Wh·kg⁻¹ (at a power density of 390 W·kg⁻¹) and still delivered the highest power density of 9.3 kW·kg⁻¹ with a high energy density of 74 Wh·kg⁻¹. In addition, our ZIHC also exhibited excellent cycling stability. After 20000 cycles at 10 A·g⁻¹, it retained 90% of its initial capacity and exhibited high Coulombic efficiency (≈100%). In order to investigate the causes of capacity decay, we examined the cycled zinc foil by scanning electron microscopy and X-ray diffraction. The results showed that a large number of Zn₄SO₄(OH)₆⋅3H₂O disordered dendrites were formed on the surface of the zinc foil. These dendrites inhibited the reversible deposition/dissolution of zinc ions, resulting in the capacity decay of the ZIHC during the cycling process. This study will be helpful for developing next-generation high-performance energy storage devices.