Flexible Supercapacitors Based on Graphene/Boron Nitride Nanosheets Electrodes and PVA/PEI Gel Electrolytes.

Chan Wang,Kuan Hu,Ming-Rong Zhang,Zhou Li,Ying Liu,Zhiwei Wang

doi:10.3390/ma14081955

Abstract

All-solid-state supercapacitors have gained increasing attention as wearable energy storage devices, partially due to their flexible, safe, and lightweight natures. However, their electrochemical performances are largely hampered by the low flexibility and durability of current polyvinyl alcohol (PVA) based electrolytes. Herein, a novel polyvinyl alcohol-polyethyleneimine (PVA-PEI) based, conductive and elastic hydrogel was devised as an all-in-one electrolyte platform for wearable supercapacitor (WSC). For proof-of-concept, we assembled all-solid-state supercapacitors based on boron nitride nanosheets (BNNS) intercalated graphene electrodes and PVA-PEI based gel electrolyte. Furthermore, by varying the electrolyte ions, we observed synergistic effects between the hydrogel and the electrode materials when KOH was used as electrolyte ions, as the Graphene/BNNS@PVA-PEI-KOH WSCs exhibited a significantly improved areal capacitance of 0.35 F/cm2 and a smaller ESR of 6.02 ohm/cm2. Moreover, due to the high flexibility and durability of the PVA-PEI hydrogel electrolyte, the developed WSCs behave excellent flexibility and cycling stability under different bending states and after 5000 cycles. Therefore, the conductive, yet elastic, PVA-PEI hydrogel represents an attractive electrolyte platform for WSC, and the Graphene/BNNS@PVA-PEI-KOH WSCs shows broad potentials in powering wearable electronic devices.

Highlights

Published: 14 April 2021The vigorous development of wearable smart devices presents new requirements for energy supply units [1,2]
The broad peak ranging from about 3208 cm−1 to 3362 cm−1, assochain Polyvinyl alcohol (PVA) and short-chain PEI formed−1a crosslinked network due to multiple physical ciated with a weak peak around 1097 cm, were assigned to the ν-OH stretching of PVA
Simand chemical intermolecular or intramolecular interactions, such as electrostatic attraction, ilarly, the −NH− stretching of PEI could be found as a weak peak at 1042 cm−1 [17]

Summary

Introduction

Published: 14 April 2021The vigorous development of wearable smart devices presents new requirements for energy supply units [1,2]. Many efforts were made to realize wearable supercapacitors with robust mechanical properties and excellent electrochemical performances, to ensure operation in complex and dynamic natural environments [6,7,8,9,10]. Polyvinyl alcohol (PVA) based hydrogel electrolytes were extensively studied due to their environment-friendly, accessible, and inexpensive attributes [15,16]. They usually exhibited poor water retention ability, easy fatigue under large deformation, and poor conductivity, which severely limits the performance of PVA-based supercapacitors. As demonstrated in our previous work, the PVA-PEI hydrogels are ultra-stretchable and mechanically robust [17].

Objectives

Methods

Results

Conclusion