School of Chemical Engineering, Sungkyunkwan University , Suwon 16419, Republic of Korea.
ACS Appl Mater Interfaces. 2016 Dec 21;8(50):34455-34463. doi: 10.1021/acsami.6b12672. Epub 2016 Dec 6.
Gel electrolytes are considered to be promising candidates for the use in supercapacitors. It is worthy to systematically evaluate the internal electrochemical mechanisms with a variety of cations (poly(vinyl alcohol) (PVA)-based Li, Na, and K) toward redox-type electrode. Herein, we describe a quasi-solid-state PVA-KCl gel electrolyte for VO·0.5HO-based redox-type capacitors, effectively avoiding electrochemical oxidation and structural breakdown of layered VO·0.5HO during 10 000 charge-discharge cycles (98% capacitance retention at 400 mV s). With the gel electrolyte, symmetric VO·0.5HO-reduced graphene oxide (VO·0.5HO-rGO) devices exhibited a volumetric capacitance of 136 mF cm, which was much higher than that of 68 mF cm for PVA-NaCl and 45 mF cm for PVA-LiCl. Additionally, hybrid full cells of activated carbon cloth//VO·0.5HO-rGO delivered an energy density of 102 μWh cm and a power density of 73.38 mW cm over a wide potential window of 2 V. The present study provides direct experimental evidence for the contribution of PVA-KCl gel electrolytes toward quick redox reactions for redox-type capacitors, which is also helpful for the development of neutral pH gel electrolytes for energy storage devices.
凝胶电解质被认为是用于超级电容器的有前途的候选物。值得系统地评估各种阳离子（聚乙烯醇（PVA）基 Li、Na 和 K）对氧化还原型电极的内部电化学机制。在此，我们为基于 VO·0.5HO 的氧化还原型电容器描述了一种准固态 PVA-KCl 凝胶电解质，有效地避免了层状 VO·0.5HO 在 10000 次充放电循环过程中的电化学氧化和结构破坏（在 400 mV s 时保持 98%的电容保持率）。使用凝胶电解质，对称的 VO·0.5HO-还原氧化石墨烯（VO·0.5HO-rGO）器件表现出 136 mF cm 的体积电容，远高于 PVA-NaCl 的 68 mF cm 和 PVA-LiCl 的 45 mF cm。此外，活性炭布//VO·0.5HO-rGO 的混合全电池在 2 V 的宽电位窗口下提供了 102 μWh cm 的能量密度和 73.38 mW cm 的功率密度。本研究为 PVA-KCl 凝胶电解质对氧化还原型电容器快速氧化还原反应的贡献提供了直接的实验证据，这也有助于开发用于储能设备的中性 pH 凝胶电解质。
