[en] The development of asymmetric supercapacitors (ASCs) with high power and energy density is greatly restricted by the low capacitance of the anode materials. V₂O₅ is a promising anode material with high theoretical capacity, but its low conductivity and high dissolution are not conducive to applications in energy storage. Herein, oxygen-vacancy PEDOT/V₂O₅ ultrathin nanosheets with a thickness of about 4.4 nm are fabricated by the oxidative polymerization of EDOT monomers on V₂O₅ nanosheets in the absence of other oxidants. The results of XPS and EPR confirm that the polymerization of PEDOT increases the oxygen vacancy concentration of V₂O₅. The PEDOT/V₂O₅ nanosheets exhibit a specific capacitance of 406 F g^-1 at 2 mV s^-1 and excellent cyclic stability in the mixed organic electrolyte of dimethyl carbonate and ethylene carbonate. The energy density of ASCs composed of PEDOT/V₂O₅ as the anode and activated carbon as the cathode reaches 65 W h kg^-1 at a power density of 1490 W kg^-1. This means that PEDOT/V₂O₅ has enormous potential in high-energy storage. (authors)

[en] Lithium-sulfur (Li-S) battery has been considered as one promising rechargeable battery with ultrahigh theoretical energy density. However, its practical application is mainly hindered by volume expansion during cycling and irreversible shuttle effect of soluble lithium polysulfides (LiPSs). Herein, we reported a rational design and fabrication of multi yolk-shell Co-NC@ nitrogen doped hollow carbon spheres (Co-NC@N-HCSs) as sulfur host for high performance Li-S batteries via a nano-confined synthesis strategy. The growth mechanism of multi yolk-shell ZIF-67s@N-HCSs nanostructure was studied and the ZIF-67 yolks were tunable by changing the reactant concentration. Regarding to multi yolk-shell Co-NC@N-HCSs hybrid, the nitrogen doped carbon shell provides effective physical confinement, abundant sulfur loading space and volume expansion alleviation, while the multi polar Co-NC yolks can enhance the internal electron conductivity inside the cavity and offer stronger chemisorption capability for LiPSs as well as catalytic effects on the redox reaction of LiPSs. Benefiting from the unique multi yolk-shell design, the S/Co-NC@N-HCSs electrode with sulfur content of 80.82 wt%, exhibits high discharge capacity of 1173 mAh g⁻¹ at 0.1C and 995.8 mAh g⁻¹ at 1C. It also shows long cycle life up to 450 cycles with a slow capacity decay rate of 0.13% per cycle. The electrochemical performance of S/Co-NC@N-HCSs is obviously promoted compared with S/N-HCSs, suggesting its potential to develop high performance lithium sulfur batteries.

[en] Two-dimensional MoS₂ materials have attracted more and more interest and been applied to the field of energy storage because of its unique physical, optical, electronic and electrochemical properties. However, there are no reports on high-stable transparent MoS₂ nanofilms as supercapacitors electrode. Here, we describe a transparent 1T-MoS₂ nanofilm electrode with super-long stability anchored on the indium tin oxide (ITO) glass by a simple alternate layer-by-layer (LBL) self-assembly of a highly charged cationic poly(diallyldimethylammonium chloride) (PDDA) and negative single-/few-layer 1T MoS₂ nanosheets. The ITO/(PDDA/MoS₂)₂₀ electrode shows a transmittance of 51.6% at 550 nm and obviously exhibits excellent transparency by naked eye observation. Ultrasonic damage test validates that the (PDDA/MoS₂)₂₀ film with the average thickness about 50 nm is robustly anchored on ITO substrate. Additionally, the electrochemical results indicate that the ITO/(PDDA/MoS₂)₂₀ film shows areal capacitance of 1.1 mF cm⁻² and volumetric capacitance of 220 F cm⁻³ at 0.04 mA cm⁻², 130.6% retention of the original capacitance value after 5000 cycles. Further experiments indicate that the formation of transparent (PDDA/MoS₂) _x nanofilm by LBL self-assembly can be extended to other substrates, e.g., slide glass and flexible polyethylene terephthalate (PET). Thus, the easily available (PDDA/MoS₂) _x nanofilm electrode has great potential for application in transparent and/or flexible optoelectronic and electronics devices. (paper)

[en] Highlights: • A monomer based on two EDOT units bridged by the oxygen capped alkylene was prepared. • The EDOT derivative was easily electrodeposited into free-standing PBEDTH paper. • The cyclic life of PBEDTH paper with 0.11 S cm⁻¹ was 86.7% after 5000 cycles. - Abstract: Free-standing conductive films are important for the application in organic electronics. However, PEDOT as one of the most promising CPs is difficult to be prepared into free-standing paper. Herein, a novel EDOT derivative, 1,6-bis((2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methoxy)hexane (BEDTH), was synthesized and easily electrodeposited into free-standing flexible conducting poly(1,6-bis((2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methoxy)hexane) (PBEDTH) in CH₂Cl₂ containing 0.1 M Bu₄NBF₄. The free-standing PBEDTH films with the conductivity of 0.11 S cm⁻¹ were characterized by FT-IR, UV–vis, SEM, TG, dynamic mechanical analysis and electrochemical method, respectively. Electrochemical results indicated that the specific capacitance of PBEDTH film was 40.8 F g⁻¹ at the current density of 0.5 A g⁻¹ in ionic liquid BmimBF₄ with the cycling capacitance retention of 86.7% after 5000 cycles. Additionally, the thermoelectric property of free-standing flexible PBEDTH film was also studied, showing the Seebeck coefficient was 37.2 μV K⁻¹ and the power factor was 0.015 μW K⁻² m⁻¹ at 300 K. Although the capacitive and thermoelectric performance is not satisfactory, the free-standing flexible PBEDTH films will still be promising in the areas of energies and sensors in the true sense.

[en] Highlights: • The synergies between energetics and defect passivation are systematically investigated. • The perovskite film surface transforms from p-type to n-type after TBAPF₆ modification, promoting charge transport. • TBAPF₆ not only reduces the surface defect-assisted recombination, but also restrains the interface carrier recombination. Nonradiative recombination losses are the predominant reason that limits the full thermodynamic potential of perovskite solar cells (PSCs), mainly originating from surface defects and interfacial energetics. However, their synergies between the two key factors are poorly understood. Herein, we systemically explore the energetic role of ionic liquid defect-passivator Tetrabutylammonium hexafluorophosphate (TBAPF₆) on n-i-p planar PSCs. The perovskite film surface has been transformed from p-type to n-type after TBAPF₆ modification, evidenced by a shift of Fermi level closer to the conduction band. The n-type energetics result in a higher density of electron carrier and a smaller electron extraction barrier at perovskite/PCBM interface, promoting charge transport. It is also shown that the perovskite film can undergo a clear transformation from n-type to p-type character as increasing work function of substrates. Further studies clearly illustrate that TBAPF₆ not only reduces the surface defect-assisted recombination, but also restrains the interface carrier recombination. These combined effects lead to the effective suppression of nonradiative recombination, attributing to a significant improvement in the device power conversion efficiency.

[en] Highlights: • Nanowire PProDTM free-standing film was prepared by template-free method. • The PProDTM achieved 99.6 F g⁻¹ at 1.0 A g⁻¹ in ACN containing 0.1 M Bu₄NBF₄. • The solid-state device based on PProDTM exhibited good redox property and stability. Nanowire poly (3,4-dihydro-2H-thieno [3,4-b] [1,4]dioxepin-3-yl)methanol (PProDTM) free-supporting films with conductivities around 1.92 S cm⁻¹ were prepared using a template-free electropolymerization method. The structure, morphology, mechanical properties, and thermal stability of the PProDTM films were characterized by Fourier transform infrared spectroscopy, UV–vis spectroscopy, scanning electron microscopy, dynamic mechanical analysis and thermogravimetric analysis. Moreover, the capacitance performances of PProDTM films were investigated in aqueous and organic electrolytes (acetonitrile (ACN) and dichloromethane (DCM)). In 0.1 M H₂SO₄, a symmetrical supercapacitor based on PProDTM exhibited specific capacitance of 89.2 F g⁻¹ at a current density of 1.0 A g⁻¹, an energy density of 3.1 Wh kg⁻¹ at power density of 0.5 kW kg⁻¹ and the cycling capacitance retention was 74.8% after 5000 cycles. As the scan rate and current density increased, the specific capacitance of PProDTM films clearly decreased in DCM, but no obvious changes occurred in water and ACN. In ACN containing 0.1 M Bu₄NBF₄, a symmetrical supercapacitor based on PProDTM exhibited specific capacitance of 99.6 F g⁻¹ at a current density of 1.0 A g⁻¹, an energy density of 3.5 Wh kg⁻¹ at power density of 0.5 kW kg⁻¹ and the cycling capacitance retention was 82.2% after 5000 cycles. These results imply that our flexible free-supporting PProDTM films are promising for future use in supercapacitors.