Recent research advances of self-discharge in supercapacitors: Mechanisms and suppressing strategies

Hydrogels with highly concentrated salt solution as electrolytes for solid-state supercapacitors with a suppressed self-discharge rate

“…Such SSSCs (or quasi-solidstate supercapacitors) have shown improved energy densities and additional functions such as self-healing capability, shape memory, and stretchability. 1 However, less attention has been paid on the self-discharge of SSSCs, [2][3][4] even though fast selfdischarge has seriously limited their applications in energy storage, especially for devices used for 'standby'purposes. [5][6][7][8] Typical SSSCs with hydrogel electrolytes have exhibited fast self-discharge, leading to rapid decay of open-circuit voltages (OCVs) to one-half of their charging voltages mostly within a few hours [9][10][11][12] or even just tens of minutes.…”

Three-Dimensional Porous Network Electrodes with Cu(OH)2 Nanosheet/Ni3S2 Nanowire 2D/1D Heterostructures for Remarkably Cycle-Stable Supercapacitors

“… 9 − 11 According to the charge storage mechanisms, electrode materials of SCs are divided into electric double-layer capacitors (EDLCs) and pseudocapacitors. 6 , 12 − 15 The latter stores energy by the adsorption of near-surface ions, and the fast reversible Faradic reactions lead to additional contribution taking place on the electrode materials’ surface. This makes the latter have much higher electrochemical capacities and energy densities than the EDLCs.…”

Regulating the Self‐Discharge of Flexible All‐Solid‐State Supercapacitors by a Heterogeneous Polymer Electrolyte

“…[ 4–6 ] However, the crucial challenges for practical application of supercapacitors are their relatively lower energy densities and rapider self‐discharge than various metal ion batteries. [ 2,3,7 ] Great efforts have been made to enhance the energy densities of supercapacitors by designing novel electrode materials with high electrochemical activity and novel electrolytes with a wide potential window. [ 8–14 ] On the other hand, the charged supercapacitors at a high energy state often discharge spontaneously (self‐discharge) even in an open circuit, which results in a reduction of voltage and loss of stored energy in a short time (typically tens of minutes).…”

“…[ 8–14 ] On the other hand, the charged supercapacitors at a high energy state often discharge spontaneously (self‐discharge) even in an open circuit, which results in a reduction of voltage and loss of stored energy in a short time (typically tens of minutes). [ 7,15 ] Unfortunately, the crucial problem of rapid self‐discharge is usually ignored in most research on supercapacitors. In view of practical applications, the significant issue of fast self‐discharge must be well addressed.…”

“…Associated with the electrochemical storage mechanism at the interface between electrode and electrolyte, the self‐discharge of supercapacitors is often ascribed to the following three main processes: charge redistribution, faradaic reactions, and ohmic leakage. [ 7,15 ] To suppress the self‐discharge of supercapacitors, various strategies have been demonstrated by modifying nanostructures of electrode materials, [ 16–19 ] designing novel separators, [ 20,21 ] and introducing redox compounds or liquid crystals in electrolytes. [ 11–14,22 ] It should be noted that more effects are required to understand the fundamental mechanism of how they work.…”