Title : Neutral pH Gel Electrolytes for V2O5·0.5H2O‑Based Energy Storage Devices
Authors : Aniu Qian, Kai Zhuo, Padmanathan Karthick Kannan, and Chan-Hwa Chung

Journal : ACS APPLIED MATERIALS & INTERFACES
Vol/No/Page : 8/50/34455-34463
DOI : 10.1021/acsami.6b12672

Abstract :
 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 V2O5·0.5H2O-based redox-type capacitors, effectively avoiding electrochemical oxidation and structural breakdown of layered V2O5·0.5H2O during 10 000 charge−.discharge cycles (98% capacitance retention at 400 mV s−.1). With the gel electrolyte, symmetric V2O5·0.5H2O-reduced graphene oxide (V2O5·0.5H2O-rGO) devices exhibited a volumetric capacitance of 136 mF cm−.3, which was much higher than that of 68 mF cm−.3 for PVA-NaCl and 45 mF cm−.3 for PVA-LiCl. Additionally, hybrid full cells of activated carbon cloth//V2O5·0.5H2O-rGO delivered an energy density of 102 μμWh cm−.3 and a power density of 73.38 mW cm−.3 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.