Stretchable Supercapacitors: From Materials and Structures to Devices

Abstract

Stretchable supercapacitors have received widespread attention due to their potential applications in wearable electronics and health monitoring. Stretchable supercapacitors not only possess advantages such as high power density, long cycle life, safety, and low cost of conventional supercapacitors but also have excellent flexibility and stretchability, which make them well integrated with other wearable systems. In this review, various strategies to fabricate stretchable supercapacitors are focused. The preparation methods for stretchable electrodes/devices in the literature are carefully classified and analyzed. Three strategies for preparing stretchable electrodes/devices are summarized in detail—the design of elastic polymer substrates, stretchable electrode structures, and composite electrodes combined with elastic polymers and stretchable structures. Meanwhile, the interface problem of electrodes/devices in the stretching process is studied in depth. The research progress of multifunctional stretchable supercapacitors is also introduced. Finally, challenges and possible solutions that still need to be addressed in the future development of stretchable supercapacitors are highlighted and prospected. This review comprehensively discusses the latest research progress in the field of stretchable supercapacitors and systematically elucidates the electrochemical and mechanical properties of these devices, hoping to improve the roadmap for scientists and engineers to develop supercapacitors with high electrochemical performance and good stretchability.

Stretchable Ionic Conductors for Soft Electronics

“…The unique combination of ionic conductivity, stretchability, elasticity, and/or transparency allows the stretchable ionic conductors to be widely used in the development of different types of soft electronics, including electrically driven DE actuators, [87,88,[114][115][116][117][118] mechanical sensors, [49][50][51][52][53][54][55][119][120][121] EL devices, [21][22][23][24] capacitive touchpads, [18][19][20] , TENGs, [20,[122][123][124][125][126][127][128][129] and energy storage devices. [10,[130][131][132][133] Stretchable ionic conductors with high deformability and low Young's modulus can be exploited to develop electrically driven DE actuators that can convert electrical signals into mechanical responses (e.g., contraction, expansion, movement). [87,88,[114][115][116][117]…”

“…To supply power for soft electronics, soft and stretchable energy storage devices, such as supercapacitors and lithium-ion batteries, have been designed and constructed to withstand various mechanical deformations (e.g., bending, twisting, stretching, compression). [130][131][132]142] Stretchable ionic conductors, acting as the carriers of ions, generally serve as the solid-state electrolytes for supercapacitors and lithium-ion batteries, which allow ions to transport across the electrodes during charging and discharging. [133] For example, PVA-based ion-conductive hydrogels, such as PVA/H 2 SO 4 , PVA/H 3 PO 4 , PVA/KOH, and PVA/LiCl hydrogels, have been widely used as the solid-state electrolytes for the fabrication of soft supercapacitors that exhibit stable and long-term electrochemical properties under mechanical deformations.…”

“…The unique combination of ionic conductivity, stretchability, elasticity, and/or transparency allows the stretchable ionic conductors to be widely used in the development of different types of soft electronics, including electrically driven DE actuators, [ 87,88,114–118 ] mechanical sensors, [ 49 –55, 119–121 ] EL devices, [ 21–24 ] capacitive touchpads, [ 18–20 ] , TENGs, [ 20,122–129 ] and energy storage devices. [ 10,130–133 ] Stretchable ionic conductors with high deformability and low Young's modulus can be exploited to develop electrically driven DE actuators that can convert electrical signals into mechanical responses (e.g., contraction, expansion, movement). [ 87,88,114–118 ] Electrically driven DE actuators can be fabricated by sandwiching a dielectric elastomer between two stretchable ionic conductors connected with a power source that provides a voltage ( Figure a).…”

Device-Scaled Controlled Crumpling of MXene-Based Ultrathin Supercapacitors as Stretchable Power Sources

“…The ever-growing demand for wearable and biomedical electronics has triggered the pursuance of stretchable devices that can maintain their functions under strain . The rapid development of materials science and fabrication technologies enables the creation of functional devices tolerant to stretching deformation, including intelligent textiles, e-skins with diverse sensing abilities, − and implantable bioelectronics. , Consequently, to power these devices, compatible energy storage units have become indispensable. , Supercapacitors have attracted significant attention owing to their excellent electrochemical performance of high power density, fast charge–discharge rate, and long cycle life. − In particular, stretchable supercapacitors with outstanding mechanical stability are of great interest for wearable electronics. , …”

“…10−14 In particular, stretchable supercapacitors with outstanding mechanical stability are of great interest for wearable electronics. 15,16 Recently, two-dimensional transition-metal carbide (MXene) Ti 3 C 2 T x (T x represents surface functional groups such as −O, −OH, and −F) has been intensively evaluated for developing high-performance supercapacitors due to its high conductivity (up to 9880 S cm −1 ) and high volumetric capacitance (up to 1500 F cm −3 ). 17−19 Furthermore, the hydrophilic surface makes it highly dispersible in an abundance of solvents, which favors solution processing.…”