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Tin disulfide (SnS2) is a highly promising anode material for sodium-ion batteries (SIBs) due to its substantial theoretical capacity stemming from alloying reactions and conversion mechanisms. Eliminating non-conductive binders and simplifying fabrication, the binder-free SnS2@carbon cloth (SnS2@CC) electrode is gaining attention. In this study, a one-step solvothermal synthesis was applied to fabricate binder-free SnS2@CC structures as SIB anodes. The electrochemical performance was enhanced by doping copper (Cu) into the SnS2 lattice. Solvothermal duration and Cu doping levels were systematically investigated to optimize the electrochemical properties of anodes. The Cu-doped SnS2@CC (Cu–SnS2@CC) electrodes exhibited superior electrical conductivity and sodium ion diffusion coefficients compared to those for the SnS2@CC electrodes. After 30 cycles, the Cu–SnS2@CC electrode prepared using a 15-h solvothermal process and 2% Cu doping achieved the highest capacity of 1092.8 mA h g−1 at 0.1 A g−1, while the SnS2@CC electrode yielded only 436.4 mA h g−1 under the same conditions. The optimized Cu–SnS2@CC electrode demonstrates excellent rate performance and cycling stability, with a capacity retention of 63% and Coulombic efficiency of 100% after 130 charge/discharge cycles. This research paves the way for high-performance, binder-free SnS2-based anodes in SIBs. [ABSTRACT FROM AUTHOR]

A Co-based metal organic framework derivative is considered to be a promising electroactive material for battery and supercapacitor hybrids (BSHs) for energy conservation, owing to the large surface area, high porosity and cobalt compound composition. Cobalt oxide generates numerous redox reactions and transfers abundant electricity during the charge/discharge process due to multiple redox states. A binder-free electrode is promising to reduce fabricating costs and avoid using non-conductive binders. In this work, a new oxidized zeolitic imidazolate framework-67 (O67) is synthesized on Ni foam without a binder at different temperatures as the electroactive material for BSHs for the first time. A unique four-leaf clover (FLC) morphology is obtained for O67, and more FLC is melted at higher oxidation temperatures. The highest specific capacitance (CF) of 221.5 F g−1 at 20 mV s−1 is obtained for the O67 electrode prepared at 350 °C (O67-350), while the unoxidized electrode only presents a CF value of 91.4 F g−1. The BSH is fabricated using an O67-350 electrode and a carbon electrode. At 500 W kg−1, a maximum energy density of 23.1 W h kg−1 is obtained. Also, the CF remains at 65% of the initial value after 5000 cycles. This study initiates new design routes to develop novel zeolitic imidazolate framework-67 derivatives on nickel foam directly as binder-free electrodes. [ABSTRACT FROM AUTHOR]

Metal-organic framework (MOF) derivatives with tunable pore structure and improved conductivity are intensively designed as electroactive materials. Incorporating structure directing agents (SDA) is beneficial for designing MOF derivatives with excellent electrochemical performances. Ammonium fluoroborate has been reported as an effective SDA, coupled with cobalt salt and 2-methylimidazole, to synthesize zeolitic imidazolate framework-67 (ZIF-67) derivatives for charge storage. However, the synthetic environment for growing cobalt-based active materials is relatively complex. In this study, cobalt tetrafluoroborate (Co(BF 4 ) 2 ) is proposed as a novel cobalt precursor, supplementing cobalt ions and acting as the SDA in a single chemical, to synthesize the cobalt-based electroactive material of energy storage electrodes. Interactions between solvent molecules and solutes play significant roles on the morphology, composition, and electrochemical performance of active materials. Deionized water, methanol and ethanol are used as precursor solvents to understand their effects on material and electrochemical properties. The optimal electrode presents a specific capacitance of 608.3 F/g at 20 mV/s, attributed to the highest electrochemical surface area and evident compositions of cobalt fluoride and hydroxide. A battery supercapacitor hybrid achieves the maximum energy density of 45 Wh/kg at 429 W/kg. The C F retention of 100% and Coulombic efficiency of 99% are achieved after 10,000 cycles., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)