Neutral pH Gel Electrolytes for V₂O₅·0.5H₂O-Based Energy Storage Devices

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 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.

Design of Slidable Polymer Networks: A Rational Strategy to Stretchable, Rapid Self-Healing Hydrogel Electrolytes for Flexible Supercapacitors

“…The optical photographs of the hydrogel electrolytes formed from different electrolytes intuitively show the same appearance with the original PEI–PVA–Bn hydrogels (Figure a-(i)–(iv)). According to SEM pictures, no salt crystallization or aggregation occurs in the hydrogel electrolytes (Figure b–e) . Compared with PEI–PVA–Bn-NaCl and PEI–PVA–Bn-KCl hydrogel electrolytes, PEI–PVA–Bn-LiCl hydrogel electrolyte has a wrinkled frozen-dried fracture surface morphology, which is similar to that of PEI–PVA–Bn-2 hydrogel (Figure S11).…”

“…Compared with PEI–PVA–Bn-NaCl and PEI–PVA–Bn-KCl hydrogel electrolytes, PEI–PVA–Bn-LiCl hydrogel electrolyte has a wrinkled frozen-dried fracture surface morphology, which is similar to that of PEI–PVA–Bn-2 hydrogel (Figure S11). This microstructure may promote the transfer of lithium ions in the interior of the hydrogel electrolyte . In addition, XRD results show that LiCl can be stably dissolved in the hydrogel electrolytes without crystallization.…”

3D Printing Quasi‐Solid‐State Asymmetric Micro‐Supercapacitors with Ultrahigh Areal Energy Density

“…Energy Mater. The areal capacitance is significantly higher than other reported vanadium oxide-based MSCs, such as V 2 O 5 ·0.5H 2 O (10.9 mF cm −2 ), [20] V 2 O 5 ·H 2 O (11.7 mF cm −2 ), [21] and V 2 O 5 -rGO (52.5 mF cm −2 ). Schematic illustration of 3D printing an asymmetric MSC with interdigitated electrodes.…”

“…The printed VO x / rGO symmetric MSC delivers a highest areal capacitance of 133.2 mF cm −2 , corresponding to the volumetric capacitance of 3.2 F cm −3 . The areal capacitance is significantly higher than other reported vanadium oxide-based MSCs, such as V 2 O 5 ·0.5H 2 O (10.9 mF cm −2 ), [20] V 2 O 5 ·H 2 O (11.7 mF cm −2 ), [21] and V 2 O 5 -rGO (52.5 mF cm −2 ). [22] To form the asymmetric MSC, the G-VNQDs/rGO electrode was also 3D printed.…”

Conductive NiMn-based bimetallic metal–organic gel nanosheets for supercapacitors

“…17 Therefore, the MOGs have fascinated numerous attention as the potential energy storage application materials. 18,19 However, obtaining metal organic gels with special functions (high stability, great conductivity and so on) are sometimes difficult as only the single metal component is used. The bimetallic MOGs could be utilized by introducing another active unit to get over such a weakness.…”