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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. [ABSTRACT FROM AUTHOR]

The design of supercapacitor materials with both high mass loading and high areal capacity is a major strategy to overcome relatively low energy density of supercapacitors. Herein, NiCo‐layered double hydroxide (NiCo‐LDH)/NiCoOOH composite films with both ultrahigh mass loading and high areal capacity are prepared by a two‐step cyclic voltammetry method. The films consist of NiCo‐LDH/NiCoOOH microspheres assembled with ultrafine nanosheets with highly ordered pore distribution from macropores to micropores and abundant defect active sites, which are conducive to the transport of electrolyte ions, increasing the reaction kinetics, and greatly improving the utilization of active material. The optimal film with hierarchical microstructure featuring an ultrahigh mass loading of 80 mg cm−2 not only exhibits a state‐of‐the‐art high areal capacity of 14.7 mAh cm−2, but also shows a record‐high energy density of 10.7 mWh cm−2 , as well as presents remarkable mechanical stabilityand superior capacity retention of 99% after 20000 galvanostatic charge‐discharge cycles. Moreover, by combining the experimental analysis and theoretical calculations, the mechanism of preferential conversion of the NiCo‐LDH in the subtle defect region to NiCoOOH by electrochemistry and the synergistic effect in electrochemical energy storage of the NiCo‐LDH and NiCoOOH phases is proposed. [ABSTRACT FROM AUTHOR]

Copper-sulfide-based materials have attracted noteworthy attention as thermoelectric materials due to rich elemental reserves, non-toxicity, low thermal conductivity, and adjustable electrical properties. However, research on the flexible thermoelectrics of copper sulfide has not yet been reported. In this work, we developed a facile method to prepare flexible Mn-doped Cu2−xS films on nylon membranes. First, nano to submicron powders with nominal compositions of Cu2−xMnyS (y = 0, 0.01, 0.03, 0.05, 0.07) were synthesized by a hydrothermal method. Then, the powders were vacuum-filtrated on nylon membranes and finally hot-pressed. Phase composition and microstructure analysis revealed that the films contained both Cu2S and Cu1.96S, and the size of the grains was ~20–300 nm. By Mn doping, there was an increase in carrier concentration and mobility, and ultimately, the electrical properties of Cu2−xS were improved. Eventually, the Cu2−xMn0.05S film showed a maximum power factor of 113.3 μW m−1 K−2 and good flexibility at room temperature. Moreover, an assembled four-leg flexible thermoelectric generator produced a maximum power of 249.48 nW (corresponding power density ~1.23 W m−2) at a temperature difference of 30.1 K, and had good potential for powering low-power-consumption wearable electronics. [ABSTRACT FROM AUTHOR]

A facile preparation method for flexible p-type CuI/polyvinylpyrrolidone (PVP) nanocomposite thermoelectric (TE) film is developed. First, CuI powder was synthesized by a one-pot method; second, PVP was coated in situ with the CuI powder; third, the CuI/PVP nanocomposite film was prepared on a nylon membrane by vacuum filtration and then hot-pressing. Transmission electron microscopy (TEM) observation indicates that the film consists of CuI nanograins with an average size of ~15 nm and PVP distributed at the inner wall of nanopores and the surface of the CuI nanograins. The composite film shows a large Seebeck coefficient of ~605 µVK−1 and a power factor of ~8.05 µWm−1K−2 at 300 K. The nanocomposite film also exhibits excellent flexibility (~96% of initial electrical conductivity retention after being bent 1000 times along a 4 mm radius rod). A single-leg TE module outputs a voltage of ~3.6 mV when the temperature difference is 6 K. This work provides a fast, simple, and environmentally friendly method by which to prepare flexible CuI/PVP nanocomposite TE film with a large Seebeck coefficient, which could be used as a wearable sensor. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]