Recent Development of Flexible and Stretchable Supercapacitors Using Transition Metal Compounds as Electrode Materials

Abstract

Flexible and stretchable supercapacitors (FS‐SCs) are promising energy storage devices for wearable electronics due to their versatile flexibility/stretchability, long cycle life, high power density, and safety. Transition metal compounds (TMCs) can deliver a high capacitance and energy density when applied as pseudocapacitive or battery‐like electrode materials owing to their large theoretical capacitance and faradaic charge‐storage mechanism. The recent development of TMCs (metal oxides/hydroxides, phosphides, sulfides, nitrides, and selenides) as electrode materials for FS‐SCs are discussed here. First, fundamental energy‐storage mechanisms of distinct TMCs, various flexible and stretchable substrates, and electrolytes for FS‐SCs are presented. Then, the electrochemical performance and features of TMC‐based electrodes for FS‐SCs are categorically analyzed. The gravimetric, areal, and volumetric energy density of SC using TMC electrodes are summarized in Ragone plots. More importantly, several recent design strategies for achieving high‐performance TMC‐based electrodes are highlighted, including material composition, current collector design, nanostructure design, doping/intercalation, defect engineering, phase control, valence tuning, and surface coating. Integrated systems that combine wearable electronics with FS‐SCs are introduced. Finally, a summary and outlook on TMCs as electrodes for FS‐SCs are provided.

Experimental and Theoretical Insights of Anion Regulation in MOF-Derived Ni–Co-Based Nanosheets for Supercapacitors and Anion Exchange Membrane Water Electrolyzers

“…Hence, developing multifunctional electrode materials with desired morphology, composition, crystallinity, and defects can fine-tune the physicochemical characteristics for successful application in SCs and EEW. Over the last few years, transition metal phosphides (TMPs), selenides (TMSes), and sulfides (TMSs), with higher electrical conductivity, excellent electronic structure, and unique physicochemical properties than that of TM layered double hydroxides (LDH), have been captivated as fascinating electrode candidates for energy conversion/storage systems. ,− In particular, the TM chalcogenides (TMCs; TMSes and TMSs) and TMPs consisting of both Ni and Co cations have attracted wide attention as preeminent electroactive materials for SCs and OER electrocatalysts due to their excellent redox chemistry, good durability, high electrochemical activity, high theoretical capacity, and earth-abundant nature. ,,− Tailoring the chemical composition and structure of TM-based materials using appropriate metal cations is a useful method to tune the electrochemical performance. However, the relationship between the substitution of different anionic species and their inherent electrochemical performance in TM-based materials is still unclear.…”

MOF-Derived Ultrathin NiCo-S Nanosheet Hybrid Array Electrodes Prepared on Nickel Foam for High-Performance Supercapacitors

“…The electrode materials, as the key component of supercapacitors, produce an essential effect on their service performance. Transition metal compounds (oxides, hydroxides, and sulfides) as promising electrode materials have attracted extensive attention owing to their low manufacturing cost, simple synthesis process, high theoretical specific capacity, and high energy density [ 4 , 5 , 6 , 7 ]. Moreover, they could provide enough storage charge during their contact reactions with the electrolyte owing to their varieties of chemical valence states [ 8 ].…”

Single and Double Layer of Monoclinic VO2 Ink‐Based Printed and Interdigitated Supercapacitors

“…The electrode materials for supercapacitors can be categorized into carbon-based materials, [1][2][3] conductive polymers, [4][5][6] MXenes, [7][8][9] metal and covalent organic frameworks, [10][11][12] and transition metal compounds. [13][14][15] In particular, vanadium-based materials such as vanadium oxides [16] and vanadium nitrides [17] have emerged as attractive electrode candidates due to the multiple valence states of the vanadium (V), its cost-effectivity, good conductivity, high theoretical capacitance, wide potential window, robust chargedischarge stability, and active redox reversibility. [18,19] Vanadium dioxide (VO 2 ) is nontoxic and compatible with a wide range of electrolytes.…”