In this work, flexible Cu2−xS films on nylon membranes are prepared by combining a simple hydrothermal synthesis and vacuum filtration followed by hot pressing. The films consist of Cu2S and Cu1.96S two phases with grain sizes from nano to submicron. Doping Se on the S site not only increases the Cu1.96S content in the Cu2−xS to increase carrier concentration but also modifies electronic structure, thereby greatly improves the electrical properties of the Cu2−xS. Specifically, an optimal composite film with a nominal composition of Cu2−xS0.98Se0.02 exhibits a high power factor of ~150.1 μW m−1 K−2 at 300 K, which increases by ~138% compared to that of the pristine Cu2−xS film. Meanwhile, the composite film shows outstanding flexibility (~97.2% of the original electrical conductivity is maintained after 1500 bending cycles with a bending radius of 4 mm). A four-leg flexible thermoelectric (TE) generator assembled with the optimal film generates a maximum power of 329.6 nW (corresponding power density of 1.70 W m−2) at a temperature difference of 31.1 K. This work provides a simple route to the preparation of high TE performance Cu2−xS-based films.

Manganese-based aqueous zinc-ion batteries (AZIBs) are considered promising cathode materials for large-scale energy storage applications due to their low cost and high safety. However, the primary constraints on achieving high specific capacity and cycling stability are the inherent low conductivity and suboptimal structural stability of the AZIB cathodes. Herein, we report a high-performance poly(3,4-ethylenedioxythiophene) (PEDOT)-coated vanadium-doped MnO2 nanorod (NR) electrode for AZIBs. First, vanadium-doped MnO2 (V-MnO2) NRs were synthesized by a simple hydrothermal synthesis method. The V-MnO2 NRs were further encapsulated with a nanolayer of PEDOT through an in situ polymerization process, which was subsequently treated with sulfuric acid to achieve a smooth surface. The V doping creates oxygen vacancies within the MnO2, allowing for the rapid embedding and diffusion of Zn2+. The PEDOT nanolayer greatly enhances the conductivity and structural stability of the V-MnO2. Benefiting from the unique features, an optimal composite NRs electrode exhibits a high specific capacity of 250 mAh g(-1) at 0.4 A g(-1), a high energy density (388 Wh kg(-1) at 151 W kg(-1)), and excellent stability over 5000 cycles at 3 A g(-1). In addition, the flexible pouch cell assembled with the electrode shows good stability under bending. Given the positive outcomes, the material holds great potential for use as a cathode in next-generation flexible energy storage systems.

Flexible Ag2Se thermoelectric (TE) films are promising for wearable applications near room temperature (RT). Herein, a Ag2Se film on a nylon membrane with high TE performance was fabricated by a facile method. First, Ag2Se powders were prepared by a microwave-assisted synthesis method using Ag nanowires as a template. Second, the Ag2Se powders were deposited onto nylon via vacuum filtration followed by hot pressing. Through modulating the Ag/Se molar ratio for synthesizing the Ag2Se powders, an optimized Ag2Se film demonstrates a high power factor of 1577.1 μW m−1 K−2 and good flexibility at RT. The flexibility of the Ag2Se film is mainly attributed to the flexible nylon membrane. In addition, a six-leg flexible TE generator (f-TEG) fabricated with the optimized Ag2Se film exhibits a maximum power density of 18.4 W m−2 at a temperature difference of 29 K near RT. This work provides a new solution to prepare high-TE-performance flexible Ag2Se films for f-TEGs.

Correction for 'Ultrahigh power factor and flexible silver selenide-based composite film for thermoelectric devices' by Yao Lu et al., Energy Environ. Sci., 2020, DOI: ; 10.1039/c9ee01609k.

A highly flexible Ag2Se based composite film on nylon with a record power factor is prepared for thermoelectric generators.

Correction for ‘Ultrahigh power factor and flexible silver selenide-based composite film for thermoelectric devices’ by Yao Lu et al., Energy Environ. Sci., 2020, DOI: 10.1039/c9ee01609k.

In this work, Te/poly(3,4-ethylenedioxythiophene) (PEDOT):poly(styrenesulfonate) (PSS)/Cu7Te4 ternary thermoelectric (TE) nanocomposite films were successfully fabricated by physical mixing and then drop casting. An optimum power factor of 65.3 μW/mK2 was acquired from a composite film containing 95 wt % PEDOT:PSS-coated Te (PC/Te) nanorods at 300 K, which was about 5 times as large as that of the PC/Cu7Te4 nanorod film and about 3 times as large as that of the PC/Te nanorod film. The power factor reached 112.3 μW/mK2 when the temperature was 380 K. Scanning transmission electron microscopy (STEM) and high-resolution STEM were used to observe the detailed internal microstructure of the composite film, revealing that the Te nanorods were single crystalline and the Cu7Te4 rods polycrystalline. The composite film was in fact a three-dimensional network interconnected with the PC/Te and PC/Cu7Te4 nanorods. The enhancement of the TE properties was ascribed to the synergetic effect of the two kinds of nanorods and the double-carrier filtering effect at the two heterointerfaces of Te/PEDOT:PSS and Cu7Te4/PEDOT:PSS. An eight single-leg flexible TE device consisting of the optimized composite film was fabricated, which produced a voltage of 31.2 mV and a maximum output power of 94.7 nW at a temperature gradient of 39 K.

In this work, three-dimensional (3D) tubular molybdenum disulfide (MoS2)/PPy composites have been prepared, in which the MoS2 is as the framework to promote the insertion and extraction of electrolyte ions, and PPy spherical particles or nanowires are synthesized by an in-situ oxidative polymerization method in the presence of the MoS2. FT-IR, XRD, XPS, FESEM and HRTEM are used to characterize the structures and morphologies of the as-prepared materials. The combination of conductive PPy and 3D tubular MoS2 leads to a significant synergistic effect. For MoS2/PPy particle composites, the best performance (specific capacitance of 350F/g at a current density of 1A/g) is obtained from a sample prepared with the mass ratio of pyrrole to MoS2 being 2:1. While for MoS2/PPy nanowire composites, the best performance (specific capacitance of 462F/g at 1A/g and a good cycling stability of 82% after 2000 cycles at 3A/g) is obtained from a sample prepared with the mass ratio of pyrrole to MoS2 being 5:1, which shows much better supercapacitor performance than the MoS2/PPy composite. Moreover, the composite electrode material delivers an energy density as high as 25.5 Wh/kg at a power density of 266.3W/kg and maintains 14.5 Wh/kg at a high power density of 4002W/kg. These performances feature the composite as advanced negative electrode materials and are superior to previous reports.

We investigated the influence of particle size on the microstructure and magnetocaloric effect of Fe-based alloy powders (11 μm to 100 μm in diameter). The degree of structure order varies with the powder size. The 11 μm to 18 μm powders show the largest peak magnetic entropy change (MEC). Increasing the degree of structure order tends to decrease the maximum MEC. Nevertheless, enhancement of refrigerant capacity and MEC (above 70 K) is achieved when the crystalline phase content is ∼50% (above 75 μm) in the 75 μm to 100 μm powders. Exponent n of the field dependence of MEC increases with the decrease in powder size above 22.5 K. The size dependence of the structure and properties is associated with the fact that a larger particle has a slower cooling rate and takes a longer time to form medium-to-long range ordered structures.