Two-Dimensional Synergistic Interfacial Orientation on Tin Oxide-Reinforced Cobalt Carbonate Hydroxide Heterostructures for High-Performance Energy Storage.

A hierarchical cobalt carbonate hydroxide (CCH) nanostructure with outstanding electrochemical kinetics and structural stability for energy storage is largely unknown. Herein, we report tin oxide-functionalized CCH surface-enabled unique two-dimensional (2D) interlayered heterostructures that promote high conductivity with more electroactive sites to maximize redox reactions. A simple electrodeposition technique was utilized to construct the hierarchical 2D CCH electrode, while a surface-reinforced method was employed to fabricate the 2D interlayered SnO on CCH. The fabricated SnO@CCH-8 electrode showed a maximum areal capacity of 720 mC cm-2 (specific capacitance of 515 F g-1) at a current density of 1 mA cm-2 in 3 M KOH electrolyte. The obtained results indicate that the synergetic effect of SnO in the CCH network delivers an efficient charge transfer pathway to achieve high-performance energy storage. Moreover, SnO@CCH-8//AC was devised as a hybrid supercapacitor (HSC), ensuring a maximum specific capacitance of 129 F g-1 and maximum specific energy and power of 40.25 W h kg-1 and 9000 W kg-1, respectively, with better capacitance retention (94%) even beyond 10,000 cycles. To highlight the excellent performance in real-time studies, the HSC was constructed using a coin cell and displayed to power 21 light-emitting diodes (LEDs).

Interconnected Vanadyl Pyrophosphate Nanonetworks as a Flexible Electrode for High-Voltage and Long-Life Li-Ion Supercapacitors.

Engineering vanadium-based materials with high conductivity, superior redox performance, and high operating voltage has attracted widespread attention in energy storage devices. Herein, we demonstrated a simple and feasible phosphorization technique to design three-dimensional (3D) network-like vanadyl pyrophosphate ((VO)2P2O7) nanowires on flexible carbon cloth (CC) (VP-CC). The phosphorization process enabled the VP-CC to increase the electronic conductivity, and the interconnected nano-network of VP-CC opens pathways for fast charge storage during the energy storage processes. Specifically, the 3D VP-CC electrodes and LiClO4 electrolyte designed as a Li-ion supercapacitor (LSC) demonstrate a maximum operating window of 2.0 V with a superior energy density (Ed) of 96 µWh cm-2, power density (Pd) of 10,028 µW cm-2, and outstanding cycling retention (98%) even after 10,000 cycles. In addition, a flexible LSC assembled utilizing VP-CC electrodes with a PVA/Li-based solid-state gel electrolyte exhibits a high capacitance value of 137 mF cm-2 and excellent cycling durability (86%) with a high Ed of 27 µWh cm-2 and Pd of 7237 µW cm-2. Considering excellent energy storage features, the highly conductive vanadium-based material has been utilized as an ideal electrode for various flexible/wearable energy storage devices with superior performance.

Rationally Designed Bimetallic Co-Ni Sulfide Microspheres as High-Performance Battery-Type Electrode for Hybrid Supercapacitors.

Rational designing of electrode materials is of great interest for improving the performance of battery-type supercapacitors. The bimetallic NiCo2S4 (NCS) and CoNi2S4 (CNS) electrode materials have received much attention for supercapacitors due to their rich electrochemical characteristics. However, the comparative electrochemical performances of NCS and CNS electrodes were never studied for supercapacitor application. In this work, microsphere-like bimetallic NCS and CNS structures were synthesized via a facile one-step hydrothermal method by controlling the molar ratio of Ni and Co precursors. The physico-chemical results confirmed that microsphere-like structures with cubic spinel-type NCS and CNS materials were successfully fabricated by this method. When tested as the supercapacitor electrode materials, both NCS and CNS electrodes exhibited battery-type behavior in a three-electrode configuration with outstanding electrochemical performances such as specific capacity, rate performance and cycle stability. Impressively, the CNS electrode delivered a high specific capacity of 430.1 C g-1 at 1 A g-1, which is higher than 345.9 C g-1 of the NCS electrode. Furthermore, the NCS and CNS electrodes showed a decent cycling stability with 75.70 and 84.70% capacity retention after 10,000 cycles. Benefiting from the electrochemical advantage of CNS microspheres, we fabricated a hybrid supercapacitor (HSC) device based on CNS microspheres (positive electrode) and activated carbon (AC, negative electrode), which is named as CNS//AC. The assembled CNS//AC HSC device showed a large energy density of 41.98 Wh kg-1 at a power density of 800.04 W kg-1 and displayed a remarkable cycling stability with a capacity retention of 91.79% after 15,000 cycles. These excellent electrochemical performances demonstrate that both bimetallic NCS and CNS microspheres may provide potential electrode materials for high performance battery-type supercapacitors.

High Energy Density Heteroatom (O, N and S) Enriched Activated Carbon for Rational Design of Symmetric Supercapacitors.

Carbon-based symmetric supercapacitors (SCs) are known for their high power density and long cyclability, making them an ideal candidate for power sources in new-generation electronic devices. To boost their electrochemical performances, deriving activated carbon doped with heteroatoms such as N, O, and S are highly desirable for increasing the specific capacitance. In this regard, activated carbon (AC) self-doped with heteroatoms is directly derived from bio-waste (lima-bean shell) using different KOH activation processes. The heteroatom-enriched AC synthesized using a pretreated carbon-to-KOH ratio of 1:2 (ONS@AC-2) shows excellent surface morphology with a large surface area of 1508 m2 g-1 . As an SC electrode material, the presence of heteroatoms (N and S) reduces the interfacial charge-transfer resistance and increases the ion-accessible surface area, which inherently provides additional pseudocapacitance. The ONS@AC-2 electrode attains a maximum specific capacitance (Csp ) of 342 F g-1 at a specific current of 1 Ag-1 in 1 m NaClO4 electrolyte at the wide potential window of 1.8 V. Moreover, as symmetric SCs the ONS@AC-2 electrode delivers a maximum specific capacitance (Csc ) of 191 F g-1 with a maximum specific energy of 21.48 Wh kg-1 and high specific power of 14 000 W kg-1 and excellent retention of its initial capacitance (98 %) even after 10000 charge/discharge cycles. In addition, a flexible supercapacitor fabricated utilizing ONS@AC-2 electrodes and a LiCl/polyvinyl alcohol (PVA)-based polymer electrolyte shows a maximum Csc of 119 F g-1 with considerable specific energy and power.