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Abstract In this work, single-walled carbon nanotube (SWCNT)/PEDOT:PSS coated Te nanorod (PC-Te) composite films were prepared by a simple vacuum assisted filtration method, and H 2 SO 4 treatment was employed to improve the thermoelectric performance of the composite films. The addition of SWCNTs apparently improved the electrical conductivity while reduced the Seebeck coefficient of the composite films, resulting in a reduction of the power factor. After treated with H 2 SO 4 , the electrical conductivity of the composite films was further improved, and the Seebeck coefficient decreased slightly. As a consequence, an optimized power factor of 104 μW/mK2 (corresponding to the electrical conductivity of 332 S/cm and Seebeck coefficient of 56 μV/K, respectively) was obtained for the sample containing 70 wt% SWCNTs at 300 K. A flexible thermoelectric generator prototype was fabricated to demonstrate the output properties. The open circuit voltage and maximum output power delivered from the prototype were 5.6 mV and 53.6 nW, respectively, at a temperature difference of 44 K. Graphical abstract Image 1 Highlights • SWCNT/PEDOT:PSS coated Te nanorod composite films were prepared. • Electrical conductivity of the films increased with the addition of SWCNT. • Sulfuric acid treatment improved the thermoelectric performance of the composite films. • An optimized power factor of 104 μW/mK2 was obtained at 300 K. • A flexible thermoelectric power generator prototype was fabricated. [ABSTRACT FROM AUTHOR]

Flexible and lightweight thermoelectric (TE) generators have attracted increasing interest for powering wearable electronics using the temperature difference between human body and ambient air. Conducting polymers or their based composite materials are suitable for such applications; however, most conducting polymers show p-type conduction, hence, until now almost all reported flexible TE generators, which use conducting polymers or their based composite materials, are single-carrier-type (p-type) leg devices, connecting alternatively p-type legs electrically in series with silver or other metals. In this paper, both p- and n-type flexible TE materials have been developed using polymers and single-walled carbon nanotubes (SWCNTs). The p-type TE films are prepared by integrating SWCNTs into a high conductive poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) matrix, using a dilution-filtration method. N-type TE films with Seebeck coefficient about -35 μV/K are realized by treating SWCNTs with polyethyleneimine (PEI), and an encapsulation process has been employed to effectively preserve its n-type characteristics. Benefited from the flexibility of both the substrate and the composite films, a flexible TE prototype composed of six p-n junctions connected in series has been fabricated to demonstrate TE voltage output and power generation. The output power from the prototype is 220 nW for a 50 K temperature gradient. [ABSTRACT FROM AUTHOR]

High-performance, breathable, conductive, and flexible polypyrrole (PPy) coated paper electrodes are prepared by an interfacial polymerization method using air-laid paper as a substrate. Owing to the synergistic effect of superior electrical conductivity, high wettability, and the porous architecture, the prepared electrode not only shows an outstanding specific capacitance and rate abilities (3100 and 2579 mF cm−2 at 1 and 20 mA cm−2 for a PPy coated paper electrode), but also exhibits excellent flexibility, wearability, and breathability. Based on these superior features, an all-solid-state supercapacitor assembled with the PPy coated paper electrodes shows an outstanding energy density of 62.4 µW h cm−2, remarkable air permeability and excellent flexibility to sustain various deformations. Furthermore, large-scale fabrication of conductive flexible paper electrode can be easily achieved through this method. Therefore, this work offers a new vision for flexible energy storage. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) functionalized Te (PF-Te) nanorods were in situ synthesized. A simple and efficient vacuum-assisted filtration method was employed to integrate the PF-Te nanorods with PEDOT:PSS to form PEDOT:PSS/PF-Te composite films. By varying the content of PF-Te nanorods, the Seebeck coefficient of the composites increases from 15.6 to 51.6 μV/K, while the electrical conductivity decreases from 1262 to 122.4 S/cm. A maximum power factor of 51.4 μW/mK 2 is obtained from a sample containing 70 wt% PF-Te nanorods at room temperature. An 8 single-leg flexible thermoelectric generator prototype was fabricated using the as-prepared PEDOT:PSS/PF-Te composite film containing 70 wt% PF-Te on a polyimide substrate with Ag electrodes. The prototype produced an output voltage of 2.5 mV at a 13.4 K temperature difference between human body and the environment. [ABSTRACT FROM AUTHOR]

The poly(3,4-ethylenedioxythiophene)/single walled carbon nanotube (PEDOT/SWCNT) composite films with various SWCNT contents (0–50 wt.%) have been prepared by a vapor phase polymerization technique for the first time. The Seebeck coefficients of the composite films increase with the SWCNT contents. The maximum power factor is 37.8 μW mK −2 for a composite film with 35 wt% SWCNT, which is 1.7 times as high as that of the film without SWCNTs. The composite film with 35 wt% SWCNT has then been treated with a 0.04 wt% NaBH 4 /DMSO solution and the power factor increases to 44.1 μW mK −2 after the treatment. The PEDOT chains are more orderly arranged and with decreased doping level by forming composites with SWCNT and may be de-doped further after further treated with NaBH 4 /DMSO. Therefore, the Seebeck coefficient of the composite film has been further enhanced. [ABSTRACT FROM AUTHOR]

Cu 0.05 Bi 2 Se x Te 3−x (x=0.2, 0.3, 0.4) bulk samples were prepared by hot pressing corresponding nanopowders synthesized by a gas-induced reduction method. Se doping significantly increases the carrier concentrations and hence the electrical conductivities of the samples. Based on this, a Cu 0.05 Bi 2 Se 0.3 Te 2.7 sample with a higher power factor was chosen as a pristine sample; some of the Cu 0.05 Bi 2 Se 0.3 Te 2.7 nanopowders were mixed with various amounts of Bi nanoparticles (NPs) and then hot pressed into bulk samples. The addition of Bi NPs promotes the sintering of samples. When the content of Bi NPs added is low (≤1 wt%), the electrical conductivity is higher than the pristine sample, and all the Bi NPs added samples have higher Seebeck coefficient than the pristine sample, hence, the power factor has been improved. A maximum power factor, 30.6 µWcm −1 K −2 , has been obtained for the 2 wt% Bi NPs added sample. [ABSTRACT FROM AUTHOR]

MoS 2 nanosheets with size of several-hundred nanometers were prepared by a hydrothermal intercalation/exfoliation method, then MoS 2 /Bi 2 Te 3 composite nanopowders were prepared by a microwave-assisted wet chemical method using the MoS 2 nanosheets, TeO 2 , Bi(NO 3 ) 3 ·5H 2 O, KOH and ethylene glycol as raw materials. Bulk MoS 2 /Bi 2 Te 3 nanocomposites were prepared by hot pressing the MoS 2 /Bi 2 Te 3 composite nanopowders with MoS 2 nanosheet content ranging from 0 to 17 wt% at 80 MPa and 648 K in vacuum. X-ray photoelectron spectroscopy and X-ray diffraction analyses indicate that MoS 2 and Bi 2 Te 3 did not react each other during the hot pressing. FESEM observation reveals that the MoS 2 /Bi 2 Te 3 composite samples had a more compact microstructure than the pristine Bi 2 Te 3 bulk sample. The MoS 2 phase was relatively randomly dispersed in the composite. At a given temperature, the electrical conductivity of the composites increases first then decreases as the MoS 2 content increases, whereas the Seebeck coefficient of the bulk nanocomposites does not change much. A highest power factor, ~18.3 μW cm −1 K −2 which is about 30% higher than that of pristine Bi 2 Te 3 sample, at 319 K has been achieved from a nanocomposite sample containing 6 wt% MoS 2 . [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedioxythiophene)-tosylate-polyethylene glycol- polypropylene glycol-polyethylene glycol (PEDOT-Tos-PPP) films were prepared via a vapor phase polymerization (VPP) method. The thermoelectric (TE) properties of the films before and after treated with various concentrations of HI acid have been studied. The electrical conductivity and Seebeck coefficient of the films simultaneously increased after treated with dilute HI acid solutions (<5 wt%). The electrical conductivity of the film treated with 5 wt% HI acid increased from 1532 to 1690 S cm −1 and the Seebeck coefficient increased slightly from 14.9 to 20.3 μV K −1 . The maximum power factor value of the treated film is 69.6 μW m −1 K −2 at 304 K, which is about twice as high as that of the pristine film (33.8 μW m −1 K −2 ). Field emission scanning electron microscopy (FESEM), Raman spectroscopy analyses and the thickness measurement of the films indicate that the tri-block copolymer PPP have been removed by the HI acid treatment. The UV–vis-NIR absorption spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses reveal that iodine anions (I − , I 3 − and I 5 − ) exist as dopants in the film after the treatment. The TE properties enhancement are, therefore, attributed to the combined effects of the removal of the insulating PPP and Tos − and iodine ions doping by the HI acid treatment. [ABSTRACT FROM AUTHOR]

Multi-walled carbon nanotubes (MWCNTs)/polypyrrole (PPy) thermoelectric composites with MWCNT content ranging from 0 to 68 wt% have been prepared by in-situ polymerization or interfacial polymerization method. Both methods have enhanced the thermoelectric properties of PPy significantly. TEM observation shows that the in-situ polymerized composite consists of MWCNTs/PPy core/shell structures, while the interfacial polymerized composite is inhomogeneous: only a small amount of MWCNTs being coated with PPy and most of the MWCNTs aggregated into bundles and clusters. Due to the uniform dispersion of MWCNTs in the PPy matrix and therefore the stronger π–π interactions between MWCNTs and PPy, the in-situ polymerized composite shows higher electrical conductivity than the interfacial polymerized composite. Both of the composites have similar Seebeck coefficients. The power factor of an in-situ polymerized composite with 68 wt% MWCNTs reaches 2.20 μW/mK 2 , which is 26.5 times greater than that of pure PPy. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedioxythiophene)–tosylate–polyethylene glycol–polypropylene glycol–polyethylene glycol (PEDOT–Tos–PPP) films were prepared via a vapor phase polymerization (VPP) method. The films possess good electrical conductivity (1550 S cm −1 ), low Seebeck coefficient (14.9 μV K −1 ) and thermal conductivity (0.501 W m −1 K −1 ), and ZT ∼ 0.02 at room temperature (RT, 295 K). Then, the films were treated with NaBH 4 /DMSO solutions of different NaBH 4 concentrations to adjust the redox level. After the NaBH 4 /DMSO treatment (dedoping), the electrical conductivity of the films continuously decreased from 1550 to 5.7 S cm −1 , whereas the Seebeck coefficient steeply increased from 14.9 to 143.5 μV K −1 . A maximum power factor of 98.1 μW m −1 K −2 has been achieved at an optimum redox level. In addition, the thermal conductivity of the PEDOT–Tos–PPP films decrease from 0.501 to 0.451 W m −1 K −1 after treated with 0.04% NaBH 4 /DMSO solution. A maximum ZT value of 0.064 has been achieved at RT. The electrical conductivity and thermal conductivity (Seebeck coefficient) of the untreated and 0.04% NaBH 4 /DMSO treated PEDOT–Tos–PPP films decrease (increases) with increasing temperature from 295 to 385 K. And the power factor of the films monotonically increases with temperature. The ZT at 385 K of the 0.04% NaBH 4 /DMSO treated film is 0.155. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedioxythiophene)–tosylate–polyethylene glycol–polypropylene glycol–polyethylene glycol (PEDOT–Tos–PPP) films were prepared via a vapor phase polymerization (VPP) method. The thermoelectric (TE) properties of the films before and after treated with H 2 SO 4 at different concentrations were measured at 295 K. The TE properties of the films have been significantly improved by the H 2 SO 4 treatment. For example, after treated with H 2 SO 4 at 1 M, the electrical conductivity of the film has increased remarkably from 944 to 1750 S cm −1 , the Seebeck coefficient of the film reduced slightly from 16.5 to 14.6 μV K −1 , and the thermal conductivity decreased from 0.495 to 0.474 W/mK. Hence, the ZT value at 295 K has increased from 0.016 to 0.024. The electrical conductivity (Seebeck coefficient) of the untreated and 1 M H 2 SO 4 treated PEDOT-Tos-PPP films decreases (increases) with increasing temperature from 295 to 375 K. And the power factor of the films monotonically increases with temperature. The power factor at 375 K of the 1 M H 2 SO 4 treated film is almost twice as high as that at 295 K. Atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) analyses, and the thickness measurement of the films indicate that the tri-block copolymer PPP have been removed from the PEDOT-Tos-PPP films after the H 2 SO 4 treatment, and the UV–Vis-NIR absorption spectroscopy and Raman spectroscopy analyses reveal an increasing in the doping level in the PEDOT chains after the H 2 SO 4 treatment. Therefore, the TE properties enhancement may be attributed to the combined effects of the removal of the insulating PPP from the PEDOT-Tos-PPP film, increase the doping level and conformational change of the PEDOT chains resulted from the H 2 SO 4 treatment. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide/poly(3,4-ethylene-dioxythiophene):poly(4-styrenesulfonate) (r-GO/PEDOT:PSS) composite films have been prepared by in situ reducing graphene oxide (GO)/PEDOT:PSS films prepared via a simple wet-chemical route. The as-prepared films have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and field emission scanning electron microscopy (FESEM). The in-plane electrical conductivity and Seebeck coefficient of the films have been measured at room temperature, and a maximum power factor is ∼32.6 μW/m K 2 for a 3 wt% GO/PEDOT:PSS film after reduction, which is about 1.5 times as high as that of a neat PEDOT:PSS film prepared by the same method. [ABSTRACT FROM AUTHOR]

Ag-poly(3,4-ethylenedioxythiophene) (PEDOT) and Cu-PEDOT nanocomposites have been synthesized by an interfacial polymerization method, using 3,4-ethylenedioxythiophene (EDOT) and AgNO or Cu(NO) as starting materials. Ag-PEDOT or Cu-PEDOT nanocomposites prepared at an interface of n-hexane and acetonitrile are spherical Ag- or Cu- nanoparticle (0D)-modified PEDOT nanostructures, while a Cu-PEDOT nanocomposite prepared at an interface of n-hexane and a mixture of acetonitrile and glycol exhibits a different morphology: Cu nanostructures are needle-like (1D) and embedded in a PEDOT matrix. Ag- or Cu-nanoparticle contents in the composites can be tuned by changing oxidant (AgNO or Cu(NO))/EDOT molar ratios, and thermoelectric properties of the pellets cold pressed from composite powders with different Ag or Cu contents have been measured at room temperature. When the oxidant/EDOT molar ratio is 2, both Ag-PEDOT and Cu-PEDOT nanocomposites with spherical Cu nanoparticles reach their largest power factors of 1.49 and 7.07 μW mK, respectively, while Cu-PEDOT nanocomposite with needle-like Cu nanoparticles has consistently higher power factor than the above composites. When the oxidant/EDOT molar ratio is 1, it reaches its largest power factor of 12.47 μW mK and the highest ZT value of 0.01 at room temperature. [ABSTRACT FROM AUTHOR]

Highlights: [•] The electronic structure and some transport properties of Mn3Cu4Bi4 was studied used by DFT. [•] The result shows that the Seebeck coefficient of Mn3Cu4Bi4 is isotropic and reaches 30.9μV/K. [•] It is the first time to report the Seebeck coefficient of Mn3Cu4Bi4. [ABSTRACT FROM AUTHOR]

Abstract: SnSe1−x Te x (x=0, 0.0625) bulk materials were fabricated by melting Sn, Se and Te powders and then hot pressing them at various temperatures. The phase compositions of the materials were determined by X-ray diffraction (XRD) and the crystal lattice parameters were refined by the Rietveld method performed with DBWS. XRD analysis revealed that the grains in the materials preferentially grew along the (l00) directions. The structural behavior of SnSe1−x Te x (x=0, 0.0625) was calculated using CASTEP package provided by Materials Studio. We found that the band gap of SnSe reduced from 0.643 to 0.608eV after Te doping. The calculated results were in good agreement with experimental results. The electrical conductivity and the Seebeck coefficient of the as-prepared materials were measured from room temperature to 673K. The maximum power factor of SnSe is ∼0.7μWcm−1K−2 at 673K. [Copyright &y& Elsevier]

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]

Thermoelectric (TE) fibers are more suitable than films for portable or wearable devices. Herein, 2–3 nm thick poly (3,4‐ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS) layer‐coated tellurium nanowires (PC‐Te NWs) are in situ prepared by a hydrothermal method. Then a series of PEDOT: PSS/PC‐Te NWs composite fibers are prepared by wet spinning and post‐treatment. The nanolayer prevents the agglomeration of the Te NWs and makes the NWs and PEDOT:PSS matrix have good compatibility, which results in the PC‐Te NWs content to a high value of 70 wt% and the fibers still with flexibility. The high aspect ratio of the PC‐Te NWs and the stress from the inner wall of the needle during spinning make the NWs ordered align along the composite fiber. Due to the large content and orientational arrangement of the PC‐Te NWs, as well as effective post‐treatment, an optimized composite fiber shows a power factor of 385.4 µW m−1 K−2 at 300 K, which is ≈4.9 times as high as the highest value of previously reported PEDOT:PSS/Te NWs‐based composite fibers. In addition, the composite fiber has good flexibility. The flexible TE generators assembled have excellent output performance. This work provides an effective strategy for the preparation of high‐performance flexible TE composite fibers. [ABSTRACT FROM AUTHOR]

Solid‐state Li metal batteries (SSLMBs) are attractive due to their capability to simultaneously offer high energy density and high‐level safety when combining Li metal anodes, solid‐state electrolytes (SSEs), and high‐voltage cathodes together. However, SSLMBs may well incur short circuits caused by Li dendrites penetrations, which mainly originate from the instability and poor contact between Li metal and SSEs. Herein, by taking full advantage of the reaction products of Li and Li1.3Al0.3Ti1.7(PO4)3 (LATP), a lithium‐LATP composite anode (Li‐LATP) is obtained, in which a stable matrix is formed to enhance the contact between Li and the garnet‐type SSEs, alleviating the volume change and preserving an intact interface during the charge/discharge process. Consequently, the Li‐LATP/garnet/Li‐LATP symmetric cell displays a fairly low interfacial resistance of 6 Ω cm2 and stable cycling performance for over 2500 h with a low overpotential. Furthermore, the LiCoO2/garnet/Li‐LATP full cell also shows a high discharge capacity of 159 mAh g−1 and great cycling performance. [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]

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]

Abstract PEDOT:PSS coated Te (PC Te) nanorod/PEDOT:PSS composite films were prepared by a drop-casting technique. H 2 SO 4 treatment was employed to enhance thermoelectric (TE) properties of the composite films. The addition of PC Te nanorods increased both the electrical conductivity and the Seebeck coefficient of the composite films. An optimized power factor of 141.9 μW/mK2 was obtained for the film containing 90 wt% PC Te nanorods treated with 12 M H 2 SO 4 at room temperature, which was 2.75 times as high as that of the untreated composite film, corresponding to the electrical conductivity and Seebeck coefficient of 204.6 S/cm and 83.27 μV/K, respectively. XPS and GIWAXS analysis revealed the removal of insulating PSS units and the rearrangement of PEDOT chains after the H 2 SO 4 treatment. Finally, a 9-leg TE generator prototype was fabricated using the optimized composite film. The maximum output power and area output power density produced from the prototype were 47.7 nW and 57.2 μW/cm2, respectively, at the temperature difference of 40 K. Graphical abstract Image 1 Highlights • PEDOT:PSS coated Te (PC Te) nanorods were synthesized. • PC Te/PEDOT:PSS composite films were prepared by a drop-casting method. • H 2 SO 4 treatment was used to enhance TE properties of the composite films. • An optimized power factor of 141.9 μW/mK2 was obtained. • A flexible thermoelectric generator prototype was fabricated using the optimized film. [ABSTRACT FROM AUTHOR]

In this work, three-dimensional (3D) tubular molybdenum disulfide (MoS 2 )/PPy composites have been prepared, in which the MoS 2 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 MoS 2 . 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 MoS 2 leads to a significant synergistic effect. For MoS 2 /PPy particle composites, the best performance (specific capacitance of 350 F/g at a current density of 1 A/g) is obtained from a sample prepared with the mass ratio of pyrrole to MoS 2 being 2:1. While for MoS 2 /PPy nanowire composites, the best performance (specific capacitance of 462 F/g at 1 A/g and a good cycling stability of 82% after 2000 cycles at 3 A/g) is obtained from a sample prepared with the mass ratio of pyrrole to MoS 2 being 5:1, which shows much better supercapacitor performance than the MoS 2 /PPy composite. Moreover, the composite electrode material delivers an energy density as high as 25.5 Wh/kg at a power density of 266.3 W/kg and maintains 14.5 Wh/kg at a high power density of 4002 W/kg. These performances feature the composite as advanced negative electrode materials and are superior to previous reports. [ABSTRACT FROM AUTHOR]

Bi 2 Te 3 and Bi 2 Se 3 nanoplates were synthesized by a microwave-assisted wet chemical method, and Bi 2 Se x Te 3−x (x=1, 2, 3) bulk nanocomposites were then prepared by hot pressing the Bi 2 Te 3 and Bi 2 Se 3 nanoplates at 80 MPa and 723 K in vacuum. The phase composition and microstructures of the bulk samples were characterized by powder X-ray diffraction and field-emission scanning electron microscopy, respectively. The electrical conductivity of the Bi 2 Se x Te 3−x bulk nanocomposites increases with increasing Se content, and the Seebeck coefficient value is negative, showing n-type conduction. The absolute Seebeck coefficient value decreases with increasing Se content. A highest power factor, 24.5 µWcm −1 K −2 , is achieved from the sample of x=1 at 369 K among the studied samples. [ABSTRACT FROM AUTHOR]

Conductive poly( p -phenylenediamine) (PpPD) nanopowders doped with different-concentration hydrochloric acid (HCl) were synthesized by a typical chemical oxidative polymerization method. The PpPD powders were characterized by the Fourier transform infrared spectroscopy, UV–vis spectroscopy, 1 H nuclear magnetic resonance spectroscopy and transmission electron microscope. The results showed that the morphology of the products changed from mainly spherical nanoparticles of the pure PpPD to rod-like nanoparticles of HCl doped PpPD. The pure PpPD showed n-type conduction whereas the HCl doped PpPD exhibited p-type conduction. The PpPD doped by 1 M HCl showed a maximum power factor of about 0.56 μW m −1 K −2 at room temperature. The mechanism of the change of the conduction type has also been discussed. [ABSTRACT FROM AUTHOR]

A ternary composite fiber-shaped electrode for flexible supercapacitors. [Display omitted] Fiber-shaped supercapacitors (FSCs) are considered as the optimal candidate for wearable energy devices, due to their high safety, excellent electrochemical stability, workability and body adaptability. However, the specific capacitances of today's FSCs such as carbon nanotube fibers and graphene fibers, are still not high enough for practical applications due to the limitation of their energy storage mode. So, we design a ternary composite fiber-shaped electrode: First, a kind of metal organic framework (MOF), copper-catecholate (Cu-CAT) nanorods, are in-situ grown on a wet-spun poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) fiber at the ambient temperature. Second, polypyrrole (PPy) is electrodeposited on the surface of the Cu-CAT/PEDOT:PSS fiber to obtain PPy@Cu-CAT@PEDOT:PSS fiber (PPy@Cu-CAT@PF). The growing Cu-CAT with high porosity anchored on the fiber surface provides electrochemical activate sites and the encapsulation of PPy effectively provides a continuous charge transfer path and improve its cycling stability. Notably, the PPy@Cu-CAT@PF electrode exhibits a satisfactory areal capacitance of 669.93 mF cm−2 at 2 mA cm−2, which remains 61.66% even at a high current density of 20 mA cm−2. Furthermore, the assembled symmetric FSC displays excellent electrochemical properties and outstanding mechanical flexibility, demonstrating its feasibility as a wearable supercapacitor. [ABSTRACT FROM AUTHOR]

The nitrogen-doped porous carbon-coated V 2 O 3 (p-NVO@C) prepared by a one-step method exhibits high electron and ion conductivity, and the p-NVO@C exhibits excellent electrochemical performance after electrochemical activation. [Display omitted] • The use of N-containing organic ligands achieve one-step uniform nitrogen doping. • The N doping and carbon coating improve the electrical conductivity of the material. • The N atoms generate a locally enhanced electricfield to accelerate Zn2+ diffusion. • The p-NVO@C cathode demonstrates outstanding specific capacity and cycle stability. The discharge capacity and lifespan of zinc ion batteries currently remain impractical due to limitations in the cathode. Low-valence vanadium oxides are promising cathode material precursors that can be electrochemically converted into highly active hydrated amorphous oxides. However, the activation process itself suffers from structural instability or high local strain, due to the low electronic conductivity and the limited ion diffusion kinetics. To tackle this issue, herein, we synthesize porous carbon-coated nitrogen-doped V 2 O 3 (p-NVO@C) microparticles utilizing a nitrogen-containing vanadium-based metal–organic framework (MOF) as the precursor. The uniform N doping and carbon coating improve the electronic conductivity of the active material particles. The carbon coating also traps the active material to reduce its dissolution loss; the high porosity of the p-NVO@C alleviates the stress from Zn2+-intercalation-induced expansion and shortens the ion transport paths. Moreover, first-principles calculations indicate that the doped N atoms in vanadium oxides generate a locally enhanced electric field, which accelerates the diffusion of Zn2+. Given the above advantages, the p-NVO@C particles demonstrate an outstanding specific capacity of 501 mAh/g at a current density of 0.2 A/g and a remarkable rate performance after the initial activation. The capacity retention rate remains as high as 95.7 % after 2000 cycles at a current density of 10 A/g. Ex-situ characterizations confirm the robust structural stability during phase transition cycles. This work provides an excellent solution to developing cathode materials for high-performance aqueous zinc ion batteries. [ABSTRACT FROM AUTHOR]

Flexible thermoelectric (TE) generators (f-TEGs) are promising candidates to power explosively growing wearable electronics by continually converting body heat into electricity. However, intrinsic brittleness, unscalability, and high costs hinder high-performance bulk TE materials from application as f-TEGs. Herein, we report a flexible and self-healable Ag 2 Se/terpineol composite film on a nylon membrane prepared by first one-pot synthesis of Ag 2 Se powder, then screen-printing, and finally low-temperature (473 K) heat treatment. Microstructure observations reveal that the film is dense and that it consists of nano to micron Ag 2 Se grains with coherent- and semicoherent grain boundaries and a very small amount of terpineol at nanopores and/or grain boundaries. Because of the unique microstructure and synergistic effect of the two components, an optimal film exhibits a high power factor of 1550 μW m−1 K−2 (corresponding zT ∼ 0.8) at room temperature and good mechanical properties (flexibility, anti-tensile property, and self-healing ability). A six-leg f-TEG assembled with the film shows a power density of 16.23 W m−2 at a temperature difference of 34.1 K and excellent flexibility. • Ag 2 Se/terpineol nanocomposite films were prepared by a screen-printing technique. • An optimal film exhibits a power factor of 1550 μW m−1 K−2 at room temperature. • The film possesses good flexibility, anti-tensile property, and self-healing ability. • A six-leg f-TEG assembled shows a high output property and excellent flexibility. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ag/Ag 2 Se films were fabricated via vacuum filtration followed by hot-pressing. • A maximum power factor of 2436 μW m−1 K−2 is obtained from an optimized film. • The optimized Ag/Ag 2 Se film exhibited good flexibility and stability. • A flexible thermoelectric generator was assembled with the optimized film. • The generator outputs a power density ∼ 13.5 W m−2 at a Δ T of 29.6 K. Herein, we fabricate a high-performance Ag/Ag 2 Se thermoelectric (TE) film by a novel method. Firstly, Ag/Ag 2 Se nano-dendritic composite powders were synthesized by a microwave-assisted synthesis method, then the powders were vacuum filtrated on nylon filter membrane followed by hot-pressing. Through optimization of Ag:Se ratios, a maximum power factor of 2436 ± 240 μW m−1 K−2 at room temperature has been acquired. It is one of the best values reported for n-type flexible TE films to date. The high TE performance can be ascribed to the synergy effect between Ag and Ag 2 Se. Besides, the composite film also shows good flexibility: 94% and 87% of the electrical conductivity are maintained, respectively, when it is subjected to a compressive force and a tensile force after 1000 bending cycles along an 8-mm diameter rod. Meanwhile, the film also shows good stability in air and good moisture resistance. A 6-leg flexible TE generator assembled with the optimized film shows a low internal resistance of ∼ 5 Ω, mainly owing to high electrical conductivity of ∼ 3030 ± 132 S cm−1 of the film. It outputs a voltage and a maximum power of 16.1 mV and 6.08 μW (corresponding power density of ∼ 13.56 W m−2), respectively, at a temperature gradient of 29.6 K. This work provides a great path for the fabrication of exceptional high-performance n-type flexible TE films, which will certainly promote the practical applications of TE films. [ABSTRACT FROM AUTHOR]

A facile method to prepare flexible n‐type Ag2Se/Se/polypyrrole (PPy) composite films is developed. First, Ag2Se nanostructures (NSs) are wet chemically synthesized; PPy is then in situ polymerized at the surface of the Ag2Se NSs; and finally, the Ag2Se/Se/PPy composite film on a porous nylon membrane is fabricated by a vacuum‐assisted filtration process followed by hot pressing. An optimal composite film shows an exceptionally high power factor of ≈2240 µW m−1 K−2 at 300 K, mainly because of the synergistic effect between well‐developed crystalline Ag2Se grains and a small amount of Se and PPy. The film also possesses outstanding flexibility (only about 6.5% decrease in electrical conductivity after 1000 times bending along a rod with a radius of 4 mm). Moreover, a flexible thermoelectric generator composed of six legs of the film outputs a voltage of 21.2 mV and a maximum power of 4.04 µW (corresponding power density of 37.6 W m−2) at a temperature difference of 34.1 K, verifying exceptionally high thermoelectric properties. This work shows the promise of the as‐prepared composite film for practical applications in wearable devices and will surely promote the research and development of flexible TE generators. [ABSTRACT FROM AUTHOR]

N-type Ag 2 Se/PVP composite film on nylon membrane with ultrahigh thermoelectric performance and excellent flexibility. [Display omitted] • Ag nanoparticle decorated Ag 2 Se nanostructures coated with PVP are prepared. • Ag 2 Se/PVP composite films are formed by vacuum filtration and then hot pressing. • An optimal film shows ultrahigh thermoelectric power factor and flexibility. • A thermoelectric generator is assembled using the optimal flexible film. • The generator exhibits an excellent output performance. Flexible thermoelectric (TE) generators (F-TEGs), able to harvest heat energy from the human body, are considered to be competitive energy supply devices for wearable and implantable electronics. Herein, we fabricate Ag 2 Se/polyvinylpyrrolidone (PVP) films on nylon membranes via a novel nanoengineering approach: First, small amount Ag nanoparticles decorated Ag 2 Se nanowires (NWs) coated with a nanolayer of PVP are synthesized via a Se NW template method, and the Ag nanoparticles react with small amount Se residues at the core of the Ag 2 Se NWs during hot-pressing and form Ag 2 Se nanograins rich in defects embedded in big Ag 2 Se grains. The Ag 2 Se nanograin has a different orientation from the big Ag 2 Se grain; hence, the interface between the Ag 2 Se nanograin and the big Ag 2 Se grain enhances the phonon scattering but almost does not affect the transport of carriers. An optimized film exhibits a maximum power factor of 2478 ± 67 μW m−1 K−2 (corresponding ZT ∼ 1.05) at 300 K, which is one of the highest values reported for flexible Ag 2 Se films. The excellent TE properties of the film are attributed to its unique microstructure: highly densified, coherent/semi-coherent Ag 2 Se grains, embedded Ag 2 Se nanograins, and a very small amount of PVP located at nanopores. Besides, the film shows good flexibility: after 1500 times bending along a rod with a radius of 4.0 mm, the electrical conductivity still maintains 90.9 %. Furthermore, a 6-leg F-TEG assembled with the optimal film generates a maximum power of 4.58 μW (corresponding power density of ∼ 31.2 W m−2) at a temperature gradient of 38.7 K. This work provides an efficient strategy for the fabrication of ultrahigh-performance Ag 2 Se-based flexible TE films. [ABSTRACT FROM AUTHOR]

A self-supporting composite film consisting of ultra-long MnO 2 NWs, few-layer graphite nanosheets, and SWNT bundles was prepared. The self-supporting flexible electrode delivers a high energy density of 651.5 Wh kg−1 at 65.2 W kg−1. The flexible zinc ion batteries assembled with the electrode demonstrate good mechanical properties and a high reversible specific capacity of 343 mAh/g when returned to the flat state after repeated 75 bending cycles. [Display omitted] • A self-supporting MnO 2 /few-layer graphite/SWNT composite film was prepared. • Oxygen vacancies accelerate the charge transfer rate and ensure high capacity. • The interwoven structure improves the kinetics of electrochemical reactions. • An optimal electrode exhibits an energy density of 651.5 Wh kg−1 at 65.2 W kg−1. • A flexible ZIB assembled exhibits a specific capacity of 343 mAh/g at 0.4 A/g. The increasing demand for flexible and wearable electronic devices has led to widespread interest in flexible electrochemical energy storage devices. However, the transformation of the battery structure from conventional to flexible presents a great challenge to the battery design. Herein, we developed a facile method for the preparation of a self-supporting composite film consisting of oxygen-vacancy rich MnO 2 nanowires (NWs), few-layer graphite nanosheets (FLGs), and single-walled carbon nanotube (SWNT) bundles as the cathode of flexible zinc-ion batteries. This ternary interwoven interconnection 3D structure enhances the electrochemical performance of the battery and realizes fast charge transfer; oxygen vacancies in the MnO 2 NWs caused by heat treatment (300 °C in Ar) allow for rapid intercalation and diffusion of Zn2+. The interwoven FLGs and SWNT bundles improve the electrical conductivity, and the robust interactions between the two carbon nanomaterials and the MnO 2 NWs effectively make the composite film with excellent mechanical properties. This self-supporting flexible electrode exhibits a high specific capacity of 374 mAh/g at 0.4 A/g, maintains a Coulombic efficiency of ∼ 100 % after 1600 cycles at 2 A/g, and has a high energy density of 651.5 Wh kg−1 at 65.2 W kg−1. Moreover, the flexible zinc ion batteries assembled with the electrode demonstrate good mechanical properties and a high reversible specific capacity of 343 mAh/g after 75 bending cycles. Based on these findings, we believe that this composite film holds great promise as a cathode material in flexible energy storage applications. [ABSTRACT FROM AUTHOR]

The PVO prepared using the vanadium-based metal–organic framework as a template has a large specific surface area and smaller particle size, which is conducive to the rapid and complete intercalation of PEDOT, and ultimately fewer layered PVO/PEDOT nanosheets with excellent electrochemical performance are formed. [Display omitted] • The PVO@PEDOT nanosheets were prepared by in-situ polymerization. • The PVO@PEDOT has low crystallinity and a large number of oxygen vacancies. • The intercalated PEDOT overcomes the poor conductivity caused by amorphization. • The PVO@PEDOT for ZIBs exhibits a specific capacity of 403.7 mAh/g at 0.2 A/g. • The PVO@PEDOT for ZIBs has 92.8% capacity retention after 3000 cycles at 10 A/g. Layered vanadium oxides have recently emerged as ideal cathode materials for aqueous zinc-ion batteries (ZIBs) due to their high theoretical capacity and low cost. However, their inherent shortages of narrow interlayer distance and poor electric conductivity cause sluggish reaction kinetics and low structure stability, leading to battery performance deterioration. Herein, we developed a novel strategy to simultaneously realize the intercalation of conductive polymer into V 2 O 5 polyhedrons and exfoliation of the V 2 O 5 into ultrathin nanosheets. The strategy is realized by in-situ polymerization of 3,4-ethylene-dioxythiophene (EDOT) monomers in the interlayer of the V 2 O 5 polyhedrons that were derived from the annealing of vanadium-based metal–organic frameworks (MIL-100(V)) in air. The MIL-100-derived V 2 O 5 polyhedrons assembled into porous microspheres (PVO) with abundant porosity and small particle size, which facilitates the penetration of EDOT molecules into the interior of the PVO during in-situ intercalation and polymerization processes, ultimately leading to the V 2 O 5 polyhedrons exfoliating into ultrathin nanosheets. The uniform poly(3,4-ethylene-dioxythiophene) (PEDOT) layer and abundant oxygen vacancies in PVO@PEDOT nanosheets can accelerate the diffusion of electrons and zinc ions, which are evidenced by dynamic analysis, ex-situ characterizations, and density functional theory (DFT) calculations, revealing the synergetic effect of PEDOT and oxygen vacancies. Therefore, the PVO@PEDOT cathode exhibits high specific capacity (403.7 mAh g-1 at 0.2 A g-1), superior rate capability (312.8 mAh g-1 at 10 A g-1), and long-term stability (92.8% of the initial capacity remained after 3000 cycles), which is superior to the majority of ion intercalation improved V 2 O 5. [ABSTRACT FROM AUTHOR]

Room-temperature thermoelectric materials are important for converting heat into electrical energy. As a wide-bandgap semiconductor material, CuI has the characteristics of non-toxicity, low cost, and environmental friendliness. In this work, CuI powder was synthesized by a wet chemical method, then CuI film was formed by vacuum assisted filtration of the CuI powder on a porous nylon membrane, followed by hot pressing. The film exhibits a large Seebeck coefficient of 600 ÎĽV · Kâˆ'1 at room temperature. In addition, the film also shows good flexibility (∼95% retention of the electrical conductivity after being bent along a rod with a radius of 4 mm for 1000 times). A finger touch test on a single-leg TE module indicates that a voltage of 0.9 mV was immediately generated within 0.5 s from a temperature difference of 4 K between a finger and the environment, suggesting the potential application in wearable thermal sensors. [ABSTRACT FROM AUTHOR]

Abstract: A thermoelectric (TE) material is a material where a potential difference is generated as a result of a temperature difference or the corollary of this where a temperature difference is generated when a voltage is applied. These phenomena can be used to generate electricity and/or control temperature. Traditionally, thermoelectric materials are inorganic semiconductors which have been limited in their application by low efficiency and high cost. Since the 1990s, both theoretical and experimental studies have shown that low-dimensional TE materials, such as superlattices and nanowires, can enhance the value of the TE figure of merit (ZT) which is an indicator of TE thermodynamic efficiency. To date it has not been feasible to apply these materials in large-scale energy-conversion processes because of limitations in both their heat transfer efficiency and cost. When compared to inorganic materials, organic conducting polymers possess some unique features, such as low density, low cost, low thermal conductivity, easy synthesis and versatile processability and their use in preparing polymer-inorganic TE nanocomposites appears to have great potential for producing relatively low cost and high-performance TE materials. Recently, an increasing number of studies have reported on polymeric and polymer-inorganic TE nanocomposite materials. The purpose of this paper is to review the research progress on the conducting polymers and their corresponding TE nanocomposites. Its main focus is the TE nanocomposites based on conducting polymers such as polyaniline (PANI), polythiophene (PTH), poly (3, 4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS), as well as other polymers such as polyacetylene (PA), polypyrrole (PPY), polycarbazoles (PC) and polyphenylenevinylene (PPV). Typically, polymer-inorganic TE nanocomposites are produced by physical mixing, solution mixing and in situ polymerization. The key factors that limit the use of these polymers and their polymer-inorganic TE nanocomposites as TE materials are their low ZT values. More recent developments designed to overcome the limitation including, for example, the use of carbon nanotubes and graphenes and the use of computational modelling to accelerate the selection of suitable pairs of conductive polymer and inorganic TE materials to achieve best possible nanocomposites are reviewed. [Copyright &y& Elsevier]

To utilize the flexibility and high theoretical specific capacitance of polypyrrole (PPy) and high electrical conductivity and moderate electrochemical properties of emerging two-dimensional materials, MXene, herein, a high performance, flexible, and freestanding PPy/Ti 3 C 2 T x (a kind of MXene) composite film electrode is prepared by vacuum-assisted filtration of single- and few-layer Ti 3 C 2 T x sheets to obtain a Ti 3 C 2 T x film and then electrochemically deposition of PPy on the film. High-resolution scanning and transmission electron microscope (HRSTEM) observations of the focused ion beam prepared sample reveal that the electrode possesses a unique microstructure: PPy not only polymerizes on the surface of the Ti 3 C 2 T x film, but also intercalates into the gaps within the film. An optimized sample shows an outstanding specific capacitance of 420.2 F g−1 at 1 A g−1, a remarkable cycling stability of 86% capacitance retention after 10,000 cycles, a distinguished flexibility and a good mechanical performance, owing to the special microstructure and synergistic effect of the PPy and Ti 3 C 2 T x. A symmetric all-solid-state flexible supercapacitor fabricated by the 400PPy175/Ti 3 C 2 T x electrode exhibits remarkable specific capacitance of 258.3 F g−1 at 0.5 A g−1, a superior energy density of 10.82 μWh·mg−1 at a power density of 0.11 mW mg−1, and an outstanding power density of 1.89 mW mg−1 at 3.99 μWh·mg−1, indicating that the PPy/Ti 3 C 2 T x film has great potential as supercapacitor electrode. Image 1 • A free-standing PPy/Ti 3 C 2 T x composite film electrode has been prepared. • The PPy/Ti 3 C 2 T x film electrode shows an excellent flexibility. • The PPy/Ti 3 C 2 T x composite film exhibits high electrochemical performance. • The high performance of the film is because of a synergistic effect. [ABSTRACT FROM AUTHOR]

Fiber-shaped supercapacitors (FSCs) have lately attracted interest due to their tiny size, great flexibility, and the prospect of application in wearable devices. Among the FSCs, those based on poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) (PFs) are particularly promising due to their outstanding electrochemical and mechanical properties. However, the areal capacitance and cycling stability of these materials are still far below the practical requirement. In this study, zeolitic imidazolate framework-8 (ZIF-8) is utilized to prepare nitrogen-doped porous carbon (c-ZIF-8), which is then integrated into PFs by a hybrid spinning method. Because of its ultra-high specific surface area (1633.1 m2 g−1) and abundant pores, c-ZIF-8 provides more electrochemically active sites and remarkably increases the capacitance of the composite fibers. They exhibit a high specific capacitance of 635 mF cm−2 and excellent cycling stability in 10,000 cycles. • Carbonized ZIF-8@ PEDOT:PSS composite fibers were prepared by a wet spinning method. • An optimized composite fiber has a superior capacitance with excellent cyclic stability. • A 1D supercapacitor was assembled with the optimized composite fiber. • The supercapacitor exhibits a remarkable areal capacitance of 136 mF cm−2. [ABSTRACT FROM AUTHOR]

Recently, flexible thermoelectric (TE) generators (f-TEGs) have received a lot of attention. Compared with TE films on flexible substrates, self-supporting composite films prepared by combining TE materials with soft fabrics and thus retaining the inherent advantages of fabrics, such as stretchability, breathability, and flexibility, are more practical and may significantly expand the application of f-TEGs in smart wearable devices. Hence, in this work, a facile and rapid method for preparing ultra-flexible self-supporting Ag 2 Se/nylon composite films is developed. The composite films with both TE properties and flexibility were obtained by fast selenization of commercial Ag/nylon fiber fabrics in a short time (60 s) at room temperature and then hot pressing at 230 °C in a vacuum. The maximum power factor of an optimized composite film at room temperature can reach 73.7 μW m−1 K−2. Meanwhile, the film exhibits excellent flexibility with the Seebeck coefficient and electrical conductivity decreased by only 7.37 and 8.48% after being bent 4000 repetitions around a round bar with a radius of 4 mm, which exceeds most reported flexible TE films. The ultra-high flexibility is mainly attributed to its high content of the nylon matrix (∼85.05 wt%), the tight bonding between Ag 2 Se grains, and the good combination between the Ag 2 Se and nylon matrix. In addition, a 3-leg f-TEG assembled with the optimal film produces a maximum power of ∼1.524 μW (corresponding to a power density of ∼0.47 W m−2) at a temperature gradient of 40.6 K, verifying the good TE performance of the composite film. This f-TEG can also be used as a self-powered temperature sensor, showing potential applications in daily life. • Self-supporting Ag 2 Se/nylon composite films were prepared by a novel method. • The composite film is ultra-flexible mainly due to high content of nylon. • An optimized film shows a power factor of 73.7 μW m−1 K−2 at room temperature. • A flexible thermoelectric generator was assembled with the optimal film. • The generator exhibits high output performance near room temperature. [ABSTRACT FROM AUTHOR]

Abstract Recently, organic thermoelectric (TE) materials especially conducting polymers have attracted increasing attention. In this work, we successfully synthesized ultrafine poly (3,4-ethylenedioxythiophene) (PEDOT) nanowires (NWs) (∼10 nm) by a simple self-assembled micellar soft-template method and then obtain highly flexible free-standing PEDOT NW films by vacuum-assisted filtration. The films are with very high electrical conductivity (∼1340 S cm−1). After being treated with 6 M H 2 SO 4 and then with 1 M NaOH at room temperature, the film shows an enhanced power factor of 46.51 μW m−1K−2 (Seebeck coefficient of 25.5 μV K−1, electrical conductivity of 715.3 S cm−1), which increases by 54% compared with that of the pristine film. To the best of our knowledge, it outperforms the TE performance of all reported one dimensional conducting polymer-based films. In addition, the TE performance of the film almost remains unchanged even after being bent for 200 times, indicating excellent flexibility. A flexible TE prototype composed of six strips (7 mm × 30 mm) of the as-prepared PEDOT NW films connected in series shows an output power of 157.2 nW at a temperature difference of 51.6 K. The free-standing PEDOT NW films show promise to a new generation of wearable TE devices. Highlights • A simple method was used to prepare free-standing PEDOT nanowire films. • The PEDOT films show excellent flexibility. • The optimized PEDOT film shows a best TE property of all 1D polymer-based films. • A flexible device assembled from the film generates 7.1 mV and 157.2 nW at 51.6 K. [ABSTRACT FROM AUTHOR]

Composite polymer electrolytes (CPEs) are gaining increasing interest due to their combined advantages of polymer and inorganic ceramic. "Polymer-in-Ceramic" (PIC) system containing a large portion of ceramic fillers (higher than 50 wt%), possesses superior safety, electrochemical and mechanical properties, which render it a promising strategy for mass production of inorganic ceramic electrolytes. However, the poor organic-inorganic interface compatibility between polymer and ceramic leads to severe agglomeration of ceramic fillers within the polymer electrolyte, resulting in cracks in the membrane that impedes the transportation of lithium ions. Thus, two-dimensional (2D) g-C 3 N 4 nanosheets are introduced into the PIC-type electrolyte as a bridge between the organic and inorganic components to improve the homogeneity of the electrolyte membrane and build an effective transportation network. In this work, a PIC type g-C 3 N 4 / Li 1.3 Al 0.3 Ti 1.7 (PO 4) 3 (LATP)/Poly(vinylidene fluoride) (PVDF) electrolyte membrane with a thickness of 35.2 µm is prepared via a simple solution-casing method and delivers satisfactory all-around properties (a high conductivity of 5.9 × 10−4 S cm−1 at 25 ℃, a high lithium-ion transference number of 0.63 and superior thermal stability). To further evaluate its practicability, a solid-state lithium battery of LiNi 0.8 Mn 0.1 Co 0.1 O 2 |CPEs|Li is assembled and provides good cycling and rate performance at room temperature. This work proves the effectiveness of the 2D g-C 3 N 4 nanosheets in resolving the agglomeration issue and optimizing the electrochemical properties of LATP-based polymer-in-ceramic electrolyte, which provides a universal strategy to modify the PIC-type solid-state electrolytes. [Display omitted] • A flexible PIC-type LATP-based electrolyte modified with 2D g-C 3 N 4 was prepared. • g-C 3 N 4 can reduce the cracks caused by the agglomeration of LATP in a membrane. • An efficient ion transportation network has been constructed in the electrolyte. • The optimal properties of the electrolyte were achieved with 5 wt% g-C 3 N 4. [ABSTRACT FROM AUTHOR]

A Zn-doped Ni-based metal−organic framework (Ni-MOF) material with honeycomblike hierarchical spherical structure is synthesized by a microwave-assisted method using HCl as the modulator for the first time. By adjusting the amount of the Zn ions doped, an optimal Zn doped Ni-MOF electrode material is obtained, which possesses a superior electrochemical performance: specific capacity of 237.4 mA h g -1 and 122.3 mA h g -1 at 1 A/g and 20 A/g, respectively. This is one of the highest performances reported so far for MOFs. The excellent electrochemical properties are ascribed to the unique crystal structure and special morphology of the Zn-doped Ni-MOF material. This work shows that the microwave-assisted synthesis is a rapid and efficient method for preparation of Ni-MOF supercapacitor electrode material. [ABSTRACT FROM AUTHOR]

MoS 2 nanosheets have been prepared by a rapid and simple microwave-assisted wet-chemical method using MoS 2 , LiOH·H 2 O and ethylene glycol as the raw materials. The structure and morphology of the obtained product have been characterized by X-Ray diffraction (XRD), Raman spectroscopy, Atomic force microscopy (AFM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The thickness of the MoS 2 nanosheets is about 4.42 nm. The MoS 2 nanosheets after cold pressing have a low electrical conductivity and a high Seebeck coefficient of 690 μV/K. The Seebeck coefficient is much higher than that (280 μV/K) of raw MoS 2 powders. In addition, the MoS 2 nanosheets have enhanced capacitive performance compared with the raw MoS 2 powders, too. [ABSTRACT FROM AUTHOR]

As an important binary IV-VI semiconductor compound, tin selenide (SnSe) has been investigated intensively for a wide range of applications in energy storage and photovoltaic devices, due to its unique electronic and optoelectronic properties. In this work, we successfully synthesized SnSe powders by a simple, rapid and high-yield method called microwave-assisted synthesis for the first time and also measured their electrochemical performances. By rationally controlling the microwave heating time, we found that the 15-min reacted sample exhibited the most outstanding specific capacitance and rate capability (214.3 F/g at 1 A/g and 182.8 F/g at 20 A/g), and excellent cycling stability. The microwave-assisted synthesis method is efficient and rapid for preparing SnSe electrode materials. [ABSTRACT FROM AUTHOR]

Nowadays, thermoelectric (TE) materials have gained considerable attention due to their unique ability to directly convert waste heat to electricity and vice versa . For a long time, researchers have mainly focused on developing high-performance inorganic TE materials, e.g., Bi-Te, Pb-Te, and Si-Ge based alloys, etc. However, inorganic TE materials have various disadvantages, such as high-cost, heavy metal contamination, as well as relatively poor processability, etc. Compared to inorganic TE materials, poly(3,4-ethylenedioxythiophene) (PEDOT) has great potential to be used for TE materials, due to its low thermal conductivity, low-cost, and low-density, etc. Therefore, more and more attention has been focused on the preparation and TE properties of PEDOT and PEDOT based nanocomposites, especially one-dimensional (1-D) PEDOT and 1-D PEDOT based nanocomposites, due to 1-D nanostructures always have enhanced TE properties. This article presents an overview of the synthesis of PEDOT nanoparticles, 1-D PEDOT nanostructures and their corresponding nanocomposites, as well as TE properties. [ABSTRACT FROM AUTHOR]

• NiCoOOH composite was prepared by an in-situ electrochemical activation method. • The optimal electrode achieves an exceptionally high areal capacity and mass loading. • Areal capacity increases linearly by systematically tuning the pore sizes. • Volumetric capacity remain unchanged with increasing mass loading. • The electrode yields a record energy density of 19.1 mWh cm−2. Transition metal hydroxides have shown high capacity performances when at a small mass loading of active material, while it is still a great challenge to obtain a high capacity performance when the mass loading is high. To maximize the capacity at high mass loading, the microstructure of the electrode should be rationally designed. Herein, we report a nickel–cobalt (oxy)hydroxide composite with three-dimensional hierarchical porous architecture realized by an in-situ electrochemical activation method to trigger the active sites and structural rearrangement. By systematically tuning the pore sizes in the hierarchical structure, an optimal composite delivers a record high areal capacity (34.8 mAh cm−2) and energy density (19.1 mWh cm−2) at the mass loading up to 230 mg cm−2. It gives new insights for preparing high performance electrode materials by a facile method and provides a blueprint for the design of high mass-loading supercapacitors. [ABSTRACT FROM AUTHOR]

Abstract: Polyaniline/graphene nanosheets (PANI/GNs) thermoelectric (TE) bulk composite pellets and films have been prepared with PANI to GNs weight ratios ranging from 4:1 to 1:1. Their structure and morphology have been investigated by Raman spectroscopy, thermogravimetric analysis and field emission scanning electron microscopy. The TE properties of the pellets and films were measured at room temperature. As the weight ratio of PANI to GNs decreased from 4:1 to 1:1, both the electrical conductivity and the Seebeck coefficient of pellets and the films increased. This was attributed to a substantial increase in carrier mobility while carrier concentration was not significantly changed. As a result, the power factor of the pellets and films increased from 0.64 to 5.60 and 0.05 to 1.47μWm−1 K−2, respectively. This is the first time the TE properties of PANI/GNs nanocomposites were reported. [Copyright &y& Elsevier]