Synthesis of bimetallic nickel cobalt selenide particles for high-performance hybrid supercapacitors

Electrodeposition Synthesis of Coral-like MnCo Selenide Binder-Free Electrodes for Aqueous Asymmetric Supercapacitors

Bimetallic selenide compounds show great potential as supercapacitor electrode materials in energy storage and conversion applications. In this work, a coral-like MnCo selenide was grown on nickel foam using a facile electrodeposition method to prepare binder-free supercapacitor electrodes. The heating temperature was varied to tune the morphology and crystal phase of these electrodes. Excellent electrochemical performance was achieved due to the unique coral-like, dendritic- dispersed structure and a bimetallic synergistic effect, including high specific capacitance (509 C g-1 at 1 A g-1) and outstanding cycling stability (94.3% capacity retention after 5000 cycles). Furthermore, an asymmetric supercapacitor assembled with MnCo selenide as the anode and active carbon as the cathode achieved a high specific energy of 46.2 Wh kg-1 at 800 W kg-1. The work demonstrates that the prepared coral-like MnCo selenide is a highly promising energy storage material.

Iron Selenide Particles for High-Performance Supercapacitors

Nowadays, iron (II) selenide (FeSe), which has been widely studied for years to unveil the high-temperature superconductivity in iron-based superconductors, is drawing increasing attention in the electrical energy storage (EES) field as a supercapacitor electrode because of its many advantages. In this study, very small FeSe particles were synthesized via a simple, low-cost, easily scalable, and reproducible solvothermal method. The FeSe particles were characterized using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) measurements, and electrochemical impedance spectroscopy (EIS), revealing enhanced electrochemical properties: a high capacitance of 280 F/g at 0.5 A/g, a rather high energy density of 39 Wh/kg and a corresponding power density of 306 W/kg at 0.5 A/g, an extremely high cycling stability (capacitance retention of 92% after 30,000 cycles at 1 A/g), and a rather low equivalent series resistance (RESR) of ~2 Ω.

Nanoporous Conducting Polymer Nanowire Network-Encapsulated MnO2-Based Flexible Supercapacitor with Enhanced Rate Capability and Cycling Stability

Transition-metal-oxide-based electrochemical electrodes usually suffer from poor electron and ion transport, leading to deteriorated rate performance and cycling stability. Herein, we address these issues by developing a facile "conducting encapsulation" strategy toward a nanoporous PEDOT nanowire/MnO₂ nanoparticle/PEDOT nanowire composite electrode. Through encapsulation of the PEDOT nanowire network, the overall electrochemical performance of the resultant composite electrode is substantially enhanced. Specifically, the rate capability and capacitance retention are improved by ∼48.2 and ∼33%, respectively, which are 89.8% at 0.8-40 mA/cm² and 93% after 3000 charge/discharge cycles at 2.0 mA/cm², respectively. Moreover, the specific capacitance is increased by ∼6 times of that of the MnO₂@PEDOT NW electrode at ∼200 mA/cm². We find that a nanoporous conducting nanowire network that encapsulates a MnO₂ nanoparticle layer can provide efficient electron and ion transport paths and stabilize the structure of MnO₂ from collapse during charge/discharge cycling and mechanical deformation. This strategy can be applied to other pseudocapacitive material-based electrochemical electrodes, such as transition-metal oxides and conducting polymers.

Ni-soc-MOF derived carbon hollow sphere encapsulated Ni3Se4 nanocrystals for high-rate supercapacitors

Carbon hollow sphere encapsulated Ni₃Se₄ (Ni₃Se₄@CHS) nanocrystals are prepared using the Ni-soc-MOF by pyrolysis and further selenization. Ni₃Se₄@CHS exhibits a capacitance of 1720 F g^-1 at 1 A g^-1 and a capacitance retention of 97% after 6000 cycles at 5 A g^-1. Moreover, the asymmetric supercapacitor of Ni₃Se₄@CHS//AC displays a wide potential window of 1.6 V, an energy density of 45.2 W h kg^-1 at a power density of 800 W kg^-1, and excellent cycling stability (89% capacitance retention) after 5000 cycles. Overall, this work establishes a significant step to synthesize a new carbon-based material with appreciable capacitance and long cycling durability for potential applications in energy storage and beyond.