Supercapacitors Research Articles

Silicon Nanowires via Metal-Assisted Chemical Etching for Energy Storage Applications.

Silicon nanowires (SiNWs) have demonstrated great potential for energy storage due to their exceptional electrical conductivity, large surface area, and wide compositional range. Metal-assisted chemical etching (MACE) is a widely used top-down technique for fabricating silicon micro/nanostructures. SiNWs fabricated by MACE exhibit significant surface areas and diverse surface chemistry. Since the material composition and surface chemistry have a significant impact on the electrochemical energy storage performance, integrating SiNWs with diverse materials like porous carbon, metal oxides/sulfides, and polymers, can establish composites with excellent properties. Hence, it is imperative to meticulously fabricate SiNW-based materials with customizable morphologies and enhanced electrochemical energy-storage performance. This review provides an in-depth study of recent advancements in SiNW-based materials with enhanced performance for energy storage systems, such as supercapacitors (SCs) and lithium-ion batteries (LIBs). It includes a concise overview of the history, MACE synthesis, and characteristics of SiNWs. Further, it also explores the key elements that influence the MACE process of SiNWs and delves into structural engineering. Additionally, we introduce recent advances in SiNW-based materials for the design of high-performance energy-storage devices, namely SCs and LIBs. Finally, we present the crucial future prospects of SiNW-based materials for energy-storage applications.

Fabrication of modified laser-induced graphene using activated carbon and polyamic acid coating for flexible and high-performance microsupercapacitors

In this study, we developed a method to combine polyamic acid (PAA) and activated carbon (AC), which were then coated on laser-induced graphene (LIG). The material was heated to facilitate the conversion of PAA–AC into polyimide (PI)–AC. Then, the resulting material was subjected to a second laser irradiation process to obtain AC–LIG composite materials. The resulting material features a robust and flexible electrode architecture with a high surface area, improved ion accessibility, and enhanced charge transfer kinetics. In tests conducted with a three-electrode setup, the AC–LIG configuration exhibited a considerably high specific capacitance, reaching 97.2 mF cm−2 at 0.2 mA cm−2, which is approximately fourteen times larger than that of pristine LIG (7.1 mF cm−2). When integrated into a flexible microsupercapacitor using a polyvinyl alcohol (PVA)–H2SO4 (sulfuric acid) gel-type electrolyte, AC–LIG exhibited a higher specific capacitance (68.4 mF cm−2 at 0.3 mA cm−2) than d-LIG (17.1 mF cm−2 at 0.3 mA cm−2). Furthermore, AC–LIG showed good Coulombic efficiency (98.5 %) and capacitance retention (90.0 %) after 10,000 cycles. These results highlight the potential of AC–LIG as a viable alternative for advanced supercapacitor (SC) applications, providing improved energy storage capacities and a reliable performance.

Green synthesised Mn3O4 and poly (o-phenylenediamine) for antimicrobial textile-based supercapacitor applications

The advancement of wearable supercapacitors (SCs) has recently garnered a lot of attention owing to their ease of fabrication into textiles, low cost, long cycle life, fast charging and discharging, high efficiency, and ability to bridge the energy and power gap between conventional capacitors and batteries. The present study focuses on the development of wearable textile-based SC electrodes using green-synthesised manganese oxide nanoparticles functionalised on poly(o-phenylenediamine) reinforced to a polymer nanocomposite. The prepared nanocomposite was characterized using spectroscopic techniques such as UV-visible spectroscopy, Fourier transform infrared spectroscopy, x-ray diffraction studies, and scanning electron microscopy to validate the incorporation of metal oxide nanoparticles into the polymer matrix. The thermal properties were studied using thermogravimetric analysis and differential scanning calorimetry. The electrochemical performance of the bare polymer and the nanocomposite was evaluated using cyclic voltammetry, galvanostatic charge-discharge, and impedance spectroscopy techniques. An impressive specific capacitance of 213 Fg-1was achieved at a current density of 1 Ag-1for the polymer nanocomposite and even after 1000 cycles a capacitance retention of 89% was observed. Enhanced antimicrobial activity was also observed for the nanocomposite against both gram-negative and gram-positive bacteria. Based on these attributes, the fabricated device can be used as an efficient antimicrobial wearable SC.

Nickel aluminum selenide wrapped by NiCoAl-layered double hydroxide enables a robust structure for supercapacitors

To explore a simple and convenient strategy for the construction of hybrid composites as advanced electrode materials for supercapacitors (SCs), this research realized the construction of nickel − aluminium selenide (NiAlSe)@NiCoAl-layered double hydroxide (NiCoAl-LDH) heterostructure. In-situ hybridization of NiCoAl-LDH nanosheets onto NiAlSe nanoparticles anchored on carbon cloth generates a special core–shell heterostructure, which enhances the exposure of active centers and increases the surface area. The formation of heterogeneous interfaces between NiAlSe and NiCoAl-LDH alters the electronic architecture and accelerates the electron/ion migration. By making full use of the structural benefits and the cooperative effect, the NiAlSe@NiCoAl-LDH composite electrode delivered a large capacitance (Cs) of 1789.2F/g at 1 A/g along with a high retention rate of 94.7 % over 5,000 cycles, which outperforms the bare NiAlSe and NiCoAl-LDH. Meanwhile, the assembled NiAlSe@NiCoAl-LDH hybrid supercapacitor (HSC) attained maximum specific energy (Es) of 71.5 Wh kg−1. This HSC device exhibits superior cyclic durability of 92.1 % after 30,000 cycles. Thereby, this research offers valuable insights into the construction of robust electrode materials for advanced HSC devices.

Self-sulfur doped mesoporous novel carbon electrodes derived from poly-anthraquinone sulfide for high-performance supercapacitors! A comparative study

Carbon materials are suitable electrode candidates in supercapacitors (SCs) because of their availability, well-defined microstructures, and ultrahigh surface areas. Herein, a universal chemical activation method was utilized to obtain activated carbon (C-KOH) from poly-anthraquinone sulfide (PAQS) at 850 °C and reduced activated carbon (C-KOH-H) from C-KOH via a mild hydrogen reduction process at low temperature. The electrochemical performances of the PAQS derived activated carbon electrodes were investigated by assembling electric double-layer capacitors (EDLCs). Electrodes fabricated from C-KOH and C-KOH-H showed 174 and 182.3 F g−1 specific capacitances at 0.5 A g−1 current density, respectively. Whereas their energy densities were 44 and 46 Wh kg−1 at 350 and 423 W kg−1 power densities, respectively. SCs assembled from C-KOH-H showed excellent rate performance, that retained 140 F g−1 even at high current density (20 A g−1), while the one assembled with C-KOH stored 54 F g−1. Furthermore, the C-KOH-H electrode retained 98 % of the initial capacitance at 1 A g−1 over 20,000 continuous cycles. The experimental results revealed that C-KOH-H showed the best electrochemical performance in SCs, which is attributed to the presence of less sulfur and oxygen than C-KOH after the mild reduction. These results prove that PAQS show excellent activation with KOH to produce well-organized porous activated carbons having high specific surface areas, which can be utilized as high-performance electrode materials in SCs.

An environment-friendly method to prepare fulvic acid-based porous carbon for high energy density supercapacitors

Low energy density (Eg) of supercapacitors (SCs) severely limits their industrial applications. Enhancing the voltage window of SCs is an effective method to achieve a square-fold increase in Eg. 3D hierarchical porous carbons (FPs) with high yield (14.5 %) and high conductivity (87 S m−1) were prepared by an interfacial self-assembly method using low-cost biomass fulvic acid (FA) as a carbon resource and employs P123 as a structure-directing agent. The soft template P123 establishes a key role in the formation of FPs. It not only enhances the pore connectivity of FPs but also induces an interfacial orientation of the carbon micro-domains in FA. Furthermore, high-temperature annealing can repair the carbon network of FPs, thus FPs are endowed with high electrical conductivity, low carbon defects and low oxygen content (4.1 at.%), which leads to superior voltage-withstanding properties. By exploiting its structural advantages, the optimized sample FP800 exhibits a specific surface area of 1938 m2 g−1, sp2 carbon (88.5 %), a high mesopore ratio of 30.76 % and a high voltage of 3.2 V in commercial TEABF4/PC electrolyte. It gets high Cg of 107 F g−1 at 1 A g−1, high rate performance (C10/0.05) of 82.0 % and maximum Eg of 39.1 Wh kg−1. Furthermore, it also obtains an ultra-stable lifespan with 90.6 % capacity retention after 60,000 cycles. Compared to FP750 and FP850, FP800 has a more reasonable electrochemical performance.

Facile synthesis of MWCNT hexagonal needles grown on interconnected honeycombs like MnCo2O4/MnO2 nanoporous electrode for high-performance asymmetric supercapacitor

The construction of a honeycomb-like structure composed of MnCo2O4/MnO2was effectively achieved using a combination of hydrothermal processing and heat treatment. The whole surface of the MnCo2O4/MnO2 honeycomb is coated with neatly arranged hexagonal nano needles made of MWCNT, leading to a substantial enhancement in the specific surface area. At 1 A/g, the supercapacitor electrode composed of MnCo2O4/MnO2@MWCNT composite exhibited an exceptional specific capacitance of around 1539 F/g. Furthermore, it maintained approximately 95.5 % of its capacity even after undergoing 10,000 cycles. The asymmetric capacitor device, with MnCo2O4/MnO2@MWCNT and AC electrode, has a power density of 1537.8 W kg−1 and an energy density of 48.78 Wh kg−1. The MnCo2O4/MnO2composite exhibits exceptional rate performance, significant capacitance, and excellent cycle performance due to the synergistic effect between MnCo2O4/MnO2 and MWCNT, as well as the high specific surface area and unique structure. Consequently, it presents a viable option for the advancement of high-efficiency electrochemical super capacitors in the next generation.

Surface engineered covalent bridging strategy to in-situ fabricate MXene-based core-sheath fiber for flexible supercapacitors with ultrahigh volumetric energy density and mechanical properties

MXene fiber-based supercapacitors (SCs) are expected to make a major contribution to the ongoing development of wearable electronics and metaverse technologies in future. However, to fabricate fiber electrodes with high energy density and strong mechanical properties remains a major challenge for their usage in SCs. Herein, we fabricated a flexible core-sheath structural Ti3C2Tx MXene@polyaniline (MX@PA) fiber electrode with ultrahigh volumetric energy density and good tensile strength through surface engineered covalent bridging strategy via wet spinning and in situ oxidant-freepolymerization processes. Benefiting from the high-order core-sheath structure and strong Ti-O-N covalent bonds between MXene and PANI, an ultrahigh tensile strength (∼168.1 MPa) and super-toughed (∼1.75 MJ cm−3) fiber electrode was achieved. The assembled SC provided much higher volumetric capacitance of 631F cm−3 (based on the SC device) at a current density of 0.5 A cm−3 and ultralong-term cycling stability with 92.6 % capacitance retention after 10000 cycles due to the rapid electron conduction of core (MXene) and large pseudocapacitive charge transfer of the sheath (PANI). As a result, the SC delivers excellent volumetric energy density of 56.1 mWh cm−3 at a power density of 204.9 mW cm−3. The integrated SC found actual application to power a 2.5 V red LED.

Optimal techno-economic assessment of isolated microgrid integrated with fast charging stations using radial basis deep learning

The global transportation electrification commerce sector is now booming. Stakeholders are paying an increased attention to the integration of electric vehicles and electric buses into the transportation networks. As a result, there is an urgent need to invest in public charging infrastructure, particularly for fast charging facilities. Consequently, and to complete the portfolio of the green environment, these fast-charging stations (FCSs) are designed using 100% of renewable energy sources (RESs). Thus, this paper proposes an optimization model for the techno-economic assessment of FCSs comprising photovoltaic and wind turbines with various energy storage devices (ESDs). In this regard, the FCS performance is evaluated using flywheels and super capacitors due to their high-power density and charging/discharging cycles and rates. Then, optimal sizing of these distributed generators is attained considering diverse technical and economical key performance indicators. Afterwards, the problem gets more sophisticated by investigating the effect of RES’s uncertainties on the selection criterion of the FCS’s components, design and capacity. Eventually, as an effort dedicated to an online energy management approach, a deep learning methodology based on radial basis network (RBN) is implemented, validated, and carried out. In stark contrast to conventional optimization approaches, RBN demonstrates its superiority by obtaining the optimum solutions in a relatively short amount of time.

Investigating the suitability of pristine and defective C3N monolayer as supercapacitor electrodes: DFT calculations

The possibility of utilizing defected C3N monolayers as the electrodes of supercapacitors (SCs) was investigated in the current study by performing DFT computations. A single-vacancy C3N monolayer (SC3NML), a double-vacancy C3N monolayer (DC3NM) and a pure C3N monolayer (PC3NML) were investigated. The charge plots, quantum capacitance (QC) and the density of state of SC3NML, DC3NM and PC3NML were also studied. Based on the results, the QC of SC3NML and DC3NM at voltages between -0.80 and 0.80 V was more compared to the QC of PC3NML. It was possible to use SC3NML as a negative electrode and DC3NM as a positive electrode, both of which were p-type semi-conductors. The stored charge in the SC3NML and DC3NM was higher compared to the stored charge in PC3NML at voltages 0 to 0.8 V. The charge stored in DC3NM was higher than the stored charge in SC3NML and PC3NML. Finally, DC3NML layer can be regarded as an encouraging electrode for application in SCs.

Optimizing nickel-aluminium layered double hydroxides for supercapacitors: The role of 3D structural assembly

Nickel-aluminium layered double hydroxides (NiAl-LDHs) have emerged as promising electrode materials for supercapacitors (SCs) due to their inherently high specific surface area and theoretical specific capacitance, which are primarily attributed to the rapid pseudocapacitive response at the surface. However, NiAl-LDHs typically form agglomerated nanosheets, leading to a significant reduction in specific surface area, which is crucial for enhancing the number of active sites and improving the capacitive properties of the materials. To overcome this limitation, 2D nanostructures were assembled into 3D architectures by synthesizing NiAl-LDHs with distinct morphologies in a one-step hydrothermal process using an alkaline agent (NH4F). This approach resulted in the formation of 3D NiAl-LDH/HN4F structures, which exhibit a larger contact area and a greater number of redox-active sites. Consequently, the 3D NiAl-LDH/HN4F electrodes demonstrated a significantly higher specific surface area, leading to remarkable improvements in specific capacitance (1219 ± 30F g−1) and energy density (61 ± 1 Wh kg−1) compared to their 2D counterparts. This structural enhancement increases both the surface area and active site density while providing a new framework for designing high-performance LDH-based electrodes.

Enhanced Dynamic Droop Control for Microgrid Frequency and Voltage Stabilization Using Hybrid Energy Storage Systems: A SECANT Method Approach

Due to their variable and intermittent nature, the integration of renewable energy sources poses control challenges related to voltage and frequency stability in isolated microgrids. This paper proposes an enhanced dynamic droop control strategy optimized in active time along with a Hybrid Energy Storage System (HESS) comprising Battery Energy Storage System (BESS), supercapacitors (SUPCA), and Superconducting Magnetic Energy Storage (SMES) to improve microgrid stability. The Dynamic Droop Gains (DDG) are continuously tuned using the rapid-converging SECANT numerical method to enhance transient response and steady-state performance, this was achieved using MATLAB/Simulink. The HESS combines the complementary characteristics of BESS, SUPCA and SMES to balance steady power supply and temporary overload capacity. Detailed simulation studies on a microgrid test system verify that the proposed control strategy significantly enhances voltage/frequency regulation, power sharing accuracy, BESS lifespan and overall stability compared to conventional droop techniques. The SUPCA further improves the transient performance and power quality by mitigating fluctuations. The research demonstrates an innovative way to harness advanced control algorithms and emerging storage technologies for next-generation resilient and sustainable microgrids.

Fabrication of NbTe2@rGO nanosheet by hydrothermal route for cost-effective supercapacitor electrode

The expansion of energy storage devices with extensive stability and high energy density is a crucial area of research that requires immediate attention. In light of these requirements, it was worth noting that supercapacitor (SCs) exhibit great potential as viable options for achieving these demands. Supercapacitor (SCs) despite their potential currently exhibit energy density levels that fall short of the necessary threshold for long-term applications. This limitation primarily stems from the challenge of identifying the ideal materials to enhance their performance. However, transition metal tellurides have a well-studied group of materials that have garnered noticeable consideration because of high energy density. Herein, we present a novel hydrothermal method that involves the fabrication of reduced graphene oxide (rGO) nanosheet combined with niobium telluride (NbTe2) material. However, the NbTe2@rGO nanohybrid's specific capacitance (Csp) was 1475 F g−1, which was approximately twice as high as the specific capacitance of the NbTe2 (667 F g−1) electrode with a specific capacity of 826 C/g at 1 A g−1 which could be ascribed to interconnection between nanoparticles and nanosheets in the NbTe2@rGO nanohybrid with lower Rct = 0.02 Ω and outstanding cycling stability even after undergoing 7000th cycles with a capacitance retention of (97 %). The NbTe2@rGO nanohybrid demonstrated an impressive power density of 285 W kg−1 and energy density of 22 Wh kg−1 at 1 A g−1 in its symmetric two-electrode performance. The findings of this investigation suggested that NbTe2@rGO nanohybrid exhibits promising material for future energy storing devices.

Metallic 1T-MoS2 boosts the kinetics for NiS2-based hybrid supercapacitors with superb rate performance

NiS2 with high theoretical capacitance shows great potential for supercapacitors (SCs). However, the poor cycling stability and sluggish redox kinetics have limited the development of high-rate NiS2-based SCs. Integrating materials with high conductivity potentially reinforces its structure and improves its rate capability. 1T-MoS2 featuring extended interlayer spacing and superior electronic conductivity emerges as an ideal candidate. Therefore, we designed a hybrid material with an alternating interconnected structure of NiS2 and MoS2 with adjustable content of 1T-MoS2. Owing to the improved ion/electron transmittability and the mutual shielding effect, an obvious positive correlation between rate capability and stability with 1T-MoS2 content was established. The optimized 1T-MoS2/NiS2 nanosheets (NMS-2) with 1T phase purity of up to 67.6% in MoS2 demonstrated exceptional specific capacity (579.4 C g−1 at 1 A g−1) and impressive rate capability (345.0 C g−1 at 30 A g−1), which suggests much faster kinetics compared to pure NiS2. Notably, the hybrid supercapacitor (HSC) assembled with NMS-2 as the cathode and activated carbon as the anode (NMS-2//AC HSC) exhibited a maximum specific capacitance of 137.4 F g−1 at 1 A g−1. Furthermore, this HSC can deliver a high energy density of 45.9 Wh kg−1 at 774.9 W kg−1, and could retain 17.7 Wh kg−1 even at a high power density of 7731.7 W kg−1. After 5000 cycles at a high current density of 5 A g−1, the HSC still remained 93.23% of its initial capacitance with an extremely low fading rate of 0.0014% per cycle.

Cobalt-ions pre-intercalation MnO2 nanosheet arrays on nickel foam achieving boosted electrochemical pseudocapacitance for supercapacitors

Metal oxide have attracted much attention as a pseudocapacitive electrode for high energy density supercapacitors (SCs). However, the battery-like charge storage mechanism based on ions diffusion and valence change for metal oxide would lead to a poor cycling stability and unsatisfied rate performance. Herein, cobalt ions pre-intercalation MnO2 nanosheet arrays on Ni foam (Co-MnO2/NF) was prepared as the cathode for SCs. The capacitive behavior of MnO2 was enhanced via cobalt introduction. The optimized Co-MnO2/NF-2 demonstrated improved pseudocapacitance and stability, with a specific capacitance of 405.6 mF cm−2 at 1 mA cm−2. It retained 90.5 % of its initial capacitance at 10 mA cm−2 after 5000 cycles, which was superior to that of pristine MnO2 (222.4 mF cm−2, 65.0 % after 1000 cycles), Co-MnO2/NF-1 (295.2 mF cm−2, 85.9 % after 1000 cycles), and Co-MnO2/NF-3 (349.9 mF cm−2, 84.9 % after 1000 cycles). The asymmetric aqueous supercapacitor consisted of Co-MnO2/NF-2 and N-doped porous carbon fiber (NPCF) electrodes with an operating potential of 2.0 V reaches a high areal energy density of 0.06 mWh cm−2 at a power density of 0.5 mWh cm−2.

Faradaic-dominated intercalation pseudocapacitance in bimetallic ultrathin NiMn-MOF nanosheet electrodes for high-performance asymmetric supercapacitors

Specialized electrochemical characteristics of layered materials are concentrated in the interlayer regions. However, total performance is limited by slow kinetics and unstable cycles. Interfacial alteration of layered materials can significantly enhance charge storage by allowing the development of intercalation pseudocapacitance. The emergence of intercalation pseudocapacitance represents a new energy storage mechanism that bridges the gap between supercapacitors (SCs) and batteries in terms of energy and power density. In this study, bimetallic MOFs of Ni and Mn are synthesized to create a NiMn-MOF electrode with a unique 2D layered structure with ample voids and pores that enable rapid intercalation of electrolyte ions followed by Faradaic redox reactions to promote intercalation pseudocapacitance. Especially, the multiple oxidation states of the metal-ions facilitate better electrochemical activity. The NiMn-MOF electrode material is synthesized by a simple hydrothermal route. The resulting electrode exhibits a high specific capacity of 502 C/g (1025 F/g) at 1 A/g current density, along with 97.5 % capacity retention over 10,000 GCD cycles. Furthermore, an asymmetric supercapacitor (ASC), constructed using NiMn-MOF as the positive electrode and commercially available activated carbon (AC) as the negative electrode, demonstrates a high specific capacitance of 160 F/g, an energy density of 55.0 Wh/kg and a power density of 785 W/kg with a capacitance retention of 94 % over 5000 GCD cycles. This innovative nanocomposite electrode with a novel charge storage mechanism shows great potential for advancing energy density, power density, and rate performance in advanced energy storage systems.

Development of Binder–free Ni3S2/CoS2 nano–composite as electrode material for Energy Storage Application

Global energy crisis imposes immense obstacles leading towards development of innovative devices, and supercapacitors (SCs) are thought to be a viable energy storage technology. The engineering of nanostructured materials with a distinct and consistent morphological design is seen as a better option for various range of electrochemical energy sources. This study reports novel binder-free Ni3S2/CoS2 electrode material that acquires higher energy, higher energy density, as well as its simple preparation method, low cost, and earth–abundant resources. The morphological, structural, and textural characteristics resulted in surface area of 46 m2 g–1 of Ni3S2/CoS2 that will increase active sites also. The synthesized nanocomposite has particle size of 41.1 nm that leads to enhanced active sites and greater surface area as confirmed through BET analysis. Ni3S2/CoS2 nanocomposite has high specific capacity around 828.14 F g–1 at 5 mV s–1 sweep rate using 2 M KOH, a high energy density around 115.01 Wh kg–1, and power density of 1000 Wh kg–1. Ni3S2/CoS2 acquires higher ionic conductivity of 5 S m-1, this will enhance the inter-layer transference of electrons, and these results perfectly correlates with EIS, resulting in charge transfer resistance value of 0.9 Ω for nano-composite. These enhanced electrochemical capabilities of Ni3S2/CoS2 hold significant potential in practical viability.

Integration and Optimization of Multisource Electric Vehicles: A Critical Review of Hybrid Energy Systems, Topologies, and Control Algorithms

Electric vehicles (EVs) are pivotal in addressing the escalating environmental crisis. While EV drivetrains excel compared to those of vehicles with internal combustion engines (ICEs), their energy storage systems are hampered by limited range, lifespan, and lengthy charging times. Hybrid energy storage systems (HESSs) present a viable current solution to these issues. This review thoroughly explores the state of the art in the emerging field of multisource EVs that utilize HESSs, incorporating any combination of batteries (BTs), supercapacitors (SCs), flywheels (FWs), fuel cells (FCs), and/or transmotors. In addition, the paper systematically categorizes and evaluates different hybrid configurations, detailing potential topologies and their respective advantages and limitations. Moreover, the paper examines diverse control algorithms used to manage these complex systems, focusing on their effectiveness and operational efficiency. By identifying current research gaps and technological challenges, this study aims to delineate future research directions that could enhance the deployment and optimization of multisource EVs, thereby addressing critical challenges such as energy density, system reliability, and cost-effectiveness.

Integrating self-hygroscopic hydrogel electrolyte and porous electrode for supercapacitor operating in variable humidity environments

The application of supercapacitors (SCs) based on the conventional polyvinyl alcohol‑potassium hydroxide (PVA-KOH) polymer electrolyte is challenged in variable humidity environments, especially in low relative humidity (RH) environments. Herein, taking advantage of the high ionic conductivity and strong hygroscopicity of highly concentrated KOH solutions, we have prepared a hygroscopic hydrogel polymer electrolyte composed of sodium alginate (SA)/PVA/poly(acrylic acid) (PAA)-KOH. The SA/PVA/PAA-KOH gel electrolyte exhibits high ionic conductivity, superior water retention and even water adsorption capability. A three-dimensional CoCu-layered double hydroxide/zeolitic imidazole framework-67 (CuCo-LDH/ZIF-67) porous electrode has also been prepared for the construction of the high-performance SC operating in variable RH environments. The CuCo-LDH/ZIF-67 porous electrode allows deep penetration of the self-hygroscopic electrolyte, facilitating electron/ion diffusion and providing fast water transport channels. As a result, our asymmetric SC show significantly improved electrochemical performance than that of SC based on conventional PVA-KOH electrolyte under different RH environments. This integration strategy can advance the practical application of SC in extreme environments.

A novel design for conversion and storage of solar thermal energy into electrical energy using a solar thermoelectric device‐coupled supercapacitor

AbstractThe conversion of solar‐thermal (ST) power into electrical power along with its efficient storage represents a crucial and effective approach to address the energy crisis. The thermoelectric (TE) generator can absorb ST power and transform it into electrical energy, making it a highly viable technology to achieve photo‐thermal conversion (PTC). However, the practical application of the pristine TE generator devices on a larger scale is still facing several challenges. On the one hand, the pristine TE generator device has low inherent PTC efficiency, thereby leading to low power conversion. On the other hand, such solar‐thermoelectric (STE) conversion does not provide the functionality of electric energy storage. Herein, an effective strategy has been proposed that employs a CoAl2O4 PTC coating to decorate the pristine TE generator for developing the STE generator device with the remarkable STE performance and then coupling this device with a supercapacitor (SC) for effective storage power. In comparison to the pristine TE generator, the developed STE device exhibited considerable enhancement in both the open‐circuit voltage (Voc) and its maximum power density, displaying more than a 4‐ and 15‐fold improvement, respectively. In addition, the feasibility of coupling this solar‐driven STE generator device in series with a SC for ST conversion and storage was verified, and the working mechanism has been elucidated. This work presents a promising approach to effectively convert and store clean solar power into electrical energy, enabling practical applications of STE generator devices in conjunction with other electrochemical energy storage devices.