Ag2(S,Te) compounds exhibit excellent thermoelectric (TE) performance and unique mechanical properties, making them an ideal system for near-room-temperature flexible TE materials. In response to the current issues of complex preparation processes and high energy consumption for this kind of material, this work proposes a fabrication strategy for Ag2(S,Te)-based flexible TE films (f-TEFs). Ag2S0.5Te0.5 powders were first synthesized via a wet-chemical method, followed by deposition onto a nylon substrate by vacuum-assisted filtration, and were finally subjected to pressure-free sintering. An optimized composite film exhibits a power factor of 516 & micro;W m-1 K-2 at room temperature (RT), which ranks among the higher levels compared with other Ag2(S,Te)-based f-TEFs. Microstructural characterization studies show that the film contains amorphous/crystalline phases, with numerous nano-pores and wrinkled stacking faults. This unique phase composition and structural configuration synergistically result in multi-scale phonon scattering, which efficiently suppresses lattice thermal conductivity to 0.27 W m-1 K-1 and ultimately contributes to a RT ZT value of 0.34. Additionally, the film retains 93% of its initial electrical conductivity after 1500 bending cycles around a 4 mm-radius rod. A four-leg flexible TE device assembled based on this film generates an open-circuit voltage of 13.5 mV and a maximum output power of 0.84 & micro;W at a Delta T of 30 K, respectively. This work provides a novel approach for efficient and low-cost preparation of high-performance Ag2(S,Te) f-TEFs, showing great potential for long-term TE power generation and thermal sensing, thus pushing flexible electronics for practical applications.

A Ag 2 S 0.5 Te 0.5 /nylon film was prepared showing excellent flexible and high thermoelectric performance.

The growing demand for self-powered wearable electronics has spurred significant interest in flexible thermoelectric films for direct conversion from body heat into electricity. However, most thermoelectric films rely on flexible substrates and involve complex fabrication processes, proposing an urgent demand for cost-effective, high-performance, free-standing alternatives. Herein, we report a free-standing Ag2Se-based nanocomposite film modified with Bi2Se3, fabricated via scalable screen-printing followed by co-sintering. By tuning the Bi2Se3 content in the ink, nanocomposite structures primarily composed of Bi-doped Ag2Se or AgBiSe2/Ag2Se were constructed. Theoretical calculations and experimental analyses reveal that Bi doping promotes band convergence and electrical conductivity, while the in-situ formed AgBiSe2 and the heterointerface-induced energy-filtering effect boost the Seebeck coefficient. The film attains a maximum room-temperature power factor of 2000 µW m− 1 K− 2, with an ultralow in-plane thermal conductivity below 0.8 W m− 1 K− 1, attributed to the synergistic effects of residual carbon, multi-dimensional defects, and nano-interfaces. The film achieves a maximum ZT value of 0.8 at room temperature. The excellent crystallinity and carbon acting as a nano-binder endow the outstanding flexibility. A six-leg flexible thermoelectric device delivers a power density of 3.20 mW cm− 2 under a temperature gradient of 37 K, indicating great potential for wearable applications.

Cu2Se has become a highly promising thermoelectric material owing to its abundant elemental reserves, nontoxicity, and low thermal conductivity. In this work, flexible Cu2Se1-xIx (x = 0, 0.02, 0.04, and 0.06) films were synthesized by a cost-effective and facile hydrothermal approach, followed by vacuum-assisted filtration and hot pressing, and the films were dense with well-crystallized Cu2Se grains. The introduction of iodine provides an additional electron, acting as N-type doping and reducing carrier concentration. With the increase of x, the films exhibit a gradual reduction in electrical conductivity but a concurrent increase in the Seebeck coefficient. As a result, the Cu2Se1-xIx film with x = 0.04 shows an optimal power factor of ∼566.9 μW m-1 K-2 along with remarkable flexibility at room temperature. In addition, the maximum output power of the six-leg flexible thermoelectric generator fabricated using the Cu2Se0.96I0.04 film at a temperature difference of 22.8 K is 1.41 μW, with a power density of 4.02 W m-2. This work presents an effective strategy for developing high-performance flexible Cu2Se-based thermoelectric films.

Developing free-standing flexible thermoelectric films (FFTEFs) is substantial for improved highly efficient utilization of waste heat from irregular surfaces. However, current high-performance TE films are substratedependent with limited flexibility and high cost, while FFTEFs generally show inferior TE performance. Herein, free-standing Ag2Se/carbon flexible composite films were prepared by scalable screen-printing followed by facile annealing. A resulting best film presents a remarkable room-temperature power factor of 1761 mu W m- 1 K- 2, mainly deriving from well-crystallized Ag2Se grains. Strong interfacial and defective phonon scattering resulted in a low thermal conductivity of 0.66 W m- 1 K- 1 at room temperature to achieve a zT value of 0.81. The film shows excellent flexibility (electrical conductivity reduction of less than 10 % after 3000 bending cycles at a 4 mm radius), mainly because the carbon content and Ag2Se grains grown along the (00 l) planes exhibit a gradient distribution along the out-of-the-plane direction. A four-leg TE device assembled with the film outputs a maximum power of 5.5 mu W (corresponding power density of 22.9 W m- 2) at a temperature difference of 31.4 K and possesses great flexibility. This work develops an effective strategy for fabricating high-performance freestanding flexible thermoelectric films.

Ag-2(Te, S) material system has recently attracted increasing interest due to its outstanding deformability. Here, we report a novel method to prepare flexible Ag-2(Te, S) films on nylon membrane: first, a series of Ag2Te1-xSx (x = 0.1, 0.2, 0.3, 0.4, 0.5) powders are synthesized by a wet chemical method, then the powders are subsequently deposited onto nylon membranes via vacuum-assisted filtration and followed by low-temperature hot pressing. The Ag2Te1-xSx films exhibit enhanced electrical conductivity as x increases from 0.1 to 0.5, while the Seebeck coefficient decreases. Additionally, the crystallinity of the films decreases with increasing S content. The Ag2Te0.5S0.5 film exhibits a coexistence of amorphous and crystalline phases, with many nanograins randomly distributed in the amorphous matrix, and demonstrates a power factor (PF) of similar to 502.5 mu W m(-1) K-2 at room temperature. Importantly, compared with the Ag2Te/nylon film, the flexibility, and deformability of the Ag2Te0.5S0.5/nylon film are significantly improved without sacrificing the PF . Finally, a five-leg flexible TE device was assembled, generating a voltage of 15.8 mV and a maximum power of 3.17 mu W under a 29.0 K temperature gradient (Delta T). Moreover, the device demonstrated a rapid and stable response to Delta T.

Lithium metal halide solid-state electrolytes (SSEs) have emerged as promising candidates for solid-state batteries due to their high room-temperature ionic conductivity and wide electrochemical window. Among them, LaCl3-based solid electrolytes, characterized by their non-close packing, have garnered interest because of the abundant channel sites along the c-axis, which can facilitate ion transport. In this work, a high entropy LaCl3based halide solid-state electrolyte [0.5LiCl-xLaCl3(TaCl5 center dot ZrCl4 center dot AlCl3 center dot CaCl2)1/4(1-x) (HELax)] was prepared by ball-milling, and the influence of the LaCl3 proportion on the electrochemical performance and stability of the HELax SSEs was investigated. It was found that multi-ion doping results in the introduction of an amorphous phase, which can potentially enhance ionic conductivity. Meanwhile, LaCl3 is essential for maintaining the unique framework crystal structure that provides the necessary pathways for ion transport. Based on the synergistic effect, the optimized HELa0.5 halide SSE exhibited an enhanced room temperature ionic conductivity of 0.82 mS cm- 1 and a low activation energy of 0.34 eV, surpassing the performance of the non-doped 0.5LiCl-LaCl3 SSE. The lithium symmetric cell (Li|HELa0.5|Li) achieved a remarkable critical current density (CCD) of up to 12 mA cm- 2, and has sustained stable stripping-plating at a current density of 4 mA cm- 2 and a capacity of 4mAh cm- 2 over an extended period of 4000 h. Furthermore, the ASSLBs displayed a capacity retention of 84.2 % at a rate of 0.5 C over 640 cycles. This work contributes to the understanding of the role of high entropy on LaCl3 halide SSE, and provides insights into the design of superionic conductors with improved electrochemical properties for next-generation solid-state batteries.

Since most conductive polymers are p-type, developing high-performance n-type organic-inorganic composite thermoelectric (TE) fibers is a great challenge. Herein, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-coated Ag2Te nanowires (PC-Ag2Te NWs) were prepared by a liquid-phase reaction using PEDOT:PSS-coated Te nanowires (PC-Te NWs) as templates, and the PEDOT:PSS/PC-Ag2Te NWs composite fibers were then prepared by wet spinning. As the content of PC-Ag2Te NWs increases, the composite fiber changes from p-type to n-type. The PEDOT: PSS coating greatly improves the dispersibility of Ag2Te NWs in the PEDOT: PSS matrix, resulting in an ultrahigh content of 87.5 wt % of PC-Ag2Te NWs in the composite fibers, which exhibited a Seebeck coefficient of -61.3 μV K-1 and a power factor of 65.3 μW m-1 K-2. The power factor value is higher than those of previously reported n-type composite TE fibers. Contrary to the estimated thermal conductivity in other reports, in this work, the thermal conductivity of the composite fibers was measured via a transient photoelectrothermal (TPET) technique. In addition, the composite fiber has good tensile properties and mechanical strength, elongating at a break of 47.37% and a tensile stress of 6.59 MPa. For an application demonstration, a self-powered temperature sensor was assembled, which can utilize the vertical temperature difference between the human body and the environment and respond quickly to a small temperature difference.

The growing development of wearable electronics urgently requires a sustainable power source. Flexible thermoelectrics offer a promising solution by directly converting body heat into electricity, which pursues high performance, excellent flexibility, and low cost, simultaneously. Herein, we developed a method for fabricating Ag2Se/Ag/polyvinylpyrrolidone composite films through a facile nanoengineering approach. Ag nanoparticles with regulated content were introduced when synthesizing Ag2Se nanorods coated with polyvinylpyrrolidone, followed by vacuum filtering on nylon membranes and hot pressing. The optimal film shows an exceptional power factor of 3119 mu W m-1 K-2 at room temperature, which mainly results from its dense and special microstructure: coherent or twin grain boundaries of Ag2Se with Ag nanograins, a small amount of polyvinylpyrrolidone serving as a grain binder, which facilitates great flexibility of the film on nylon (remaining 96.5 % of the initial electrical conductivity after 1500 bending cycles). The flexible thermoelectric generator assembled with the film achieves a power density of 64.8 W m-2 (corresponding normalized power density of 704 mu Wm-1 K-2) under a temperature difference of 42.9 K, which is one of the highest values reported for flexible thermoelectric devices. This work provides an effective strategy for fabricating high-performance films for sustainably powering wearable electronics.

Herein, a facile method to fabricate high-performance Ag2Se1-xSx thermoelectric (TE) films on nylon membranes was developed. The Ag2Se1-xSx TE films were fabricated by first wet-chemically synthesizing Ag2Se1-xSx powders beginning from Se/Ag2S molar ratios of 0.5, 0.6, 0.7, 0.8, and 0.9, followed by vacuum-assisted filtration of the powders on nylon membranes, and finally by hot-pressing. When the Se/Ag2S molar ratio is <= 0.7, the films prepared consist of Se-substituted Ag2S with a monoclinic structure; when it is 0.8, the film obtained is composed of Ag2S and Ag2Se in two phases; when it is 0.9, the film prepared consists of S-substituted Ag2Se with an orthorhombic structure. The S-substituted Ag2Se film exhibits a power factor of similar to 1035.4 mu W m(-1) K-2 at 300 K and excellent flexibility (it retains 94.4% of the pristine electrical conductivity after being bended 1000 times around a rod with a diameter of 8 mm). Furthermore, a flexible TE generator consisting of six legs was assembled with the S-substituted Ag2Se film, and it produces a maximum output power of similar to 5.29 mu W (equivalent to a power density of similar to 10.5 W m(-2)) under a temperature gradient of 28.6 K. This work provides an avenue to explore high-performance and low-cost flexible TE devices for room temperature use.

Herein, we develop a facile wet chemical method for the synthesis of Ag2Te powders at room temperature and flexible Ag2Te/nylon thermoelectric (TE) films are prepared by vacuum-assisted filtration of the synthesized Ag2Te powders and then hot pressing. Because of the good crystallinity of Ag2Te grains and continuous grain boundaries, an optimized film exhibits a power factor of 513 mu W m(-1) K-2 at 300 K, which stands among the highest values reported for Ag2Te-based films to date. In addition, the film also has good flexibility. A four-leg flexible TE device assembled with the film generates a power density of 5.46 W m(-2) at a temperature gradient of 31.8 K. This work provides a facile and environmentally friendly method for preparing flexible Ag2Te films.

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 pNVO@C alleviates the stress from Zn 2 + -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 Zn 2 + . 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 highperformance aqueous zinc ion batteries.

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.

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 mu W m(-1) K-2 at 300 K, which is approximate to 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.

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 MnO2 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 MnO2 NWs caused by heat treatment (300 degrees 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 MnO2 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 similar to 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.

Herein, a facile method to prepare flexible S-doped Cu2Se thermoelectric films on porous nylon membranes is developed. First, S-doped Cu2Se powders with nominal compositions of Cu2Se1-xSx (x = 0, 0.02, 0.04, or 0.06) are synthesized by a hydrothermal method. Then, the as-prepared powders are deposited onto nylon substrates by vacuum-assisted filtration and hot-pressing. By adjusting the amount of S doping, the carrier concentration and mobility of the films are tuned, and the thermoelectric properties of the films are effectively optimized. As a result, the Cu2Se0.96S0.04 film displays a highest power factor of -662.2 mu W m- 1 K-2 at 300 K, representing one of the highest values reported for Cu2Se-based flexible films. The film also exhibits excellent flexibility (after 1500 bending cycles around a 4 mm radius rod, 90.8% of the initial electrical conductivity is retained). Additionally, a six-leg flexible thermoelectric generator is assembled with the Cu2Se0.96S0.04 film and outputs a peak power of 1.89 mu W at a temperature difference of 23.1 K. This work presents a new method for preparing costeffective and high -performance Cu2Se flexible thermoelectric films.

Recent studies have shown that silver selenide is a promising thermoelectric material at room temperature. Herein, flexible films with a nominal composition of (Ag1-xCux)2Se are prepared by a simple and efficient one-pot method combined with vacuum-assisted filtration and hot pressing. The thermoelectric properties of the films are regulated by both cationic doping and a dual-phase strategy via a wet chemical method. As the x increases, not only Cu is doped into the Ag2Se, but different new phases (CuAgSe and/or CuSe2) also appear. The (Ag1-xCux)2Se film with x = 0.02 composed of Cu-doped Ag2Se and CuAgSe shows a high PF of ∼2540 μW m-1 K-2 (ZT ∼ 0.90) and outstanding flexibility at room temperature. The high thermoelectric properties of the film are due to the effect of Cu doping and the CuAgSe phase, including the increase in electrical conductivity caused by doping, the enhanced phonon scattering at the Ag2Se/CuAgSe interface, and the interaction between the energy filtering effect and the doping effect. In addition to the high output performance (PDmax = 28.08 W m-2, ΔT = 32.2 K), the flexible device assembled with the (Ag0.98Cu0.02)2Se film also has potential applications as a temperature sensor.

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 Ag2Se/terpineol composite film on a nylon membrane prepared by first one-pot synthesis of Ag2Se 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 Ag2Se 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.

The development of aqueous zinc ion battery cathode materials with high capacity and high magnification is still a challenge.Herein,porous vanadium oxide/carbon（p-VO x @C,mainly VO 2 with a small amount of V 2 O 3 ） core/shell microspheres with oxygen vacancies are facilely fabricated by using a vanadium-based metal-organic framework（MIL-100（V）） as a sacrificial template.This unique structure can improve the conductivity of the VO x ,accelerate electrolyte diffusion,and suppress structural collapse during circulation.Subsequently,H 2 O molecules are introduced into the interlayer of VO x through a highly efficient in-situ electrochemical activation process,facilitating the intercalation and diffusion of zinc ions.After the activation,an optimal sample exhibits a high specific capacity of 464.3 mA h g -1 at0.2 A g -1 and 395.2 mA h g -1 at 10 A g -1 ,indicating excellent rate performance.Moreover,the optimal sample maintains a capacity retention of about 89.3% after 2500 cycles at 10 A g -1 .Density functional theory calculation demonstrates that the presence of oxygen vacancies and intercalated water molecules can significantly reduce the diffusion barrier for zinc ions.In addition,it is proved that the storage of zinc ions in the cathode is achieved by reversible intercalation/extraction during the charge and discharge process through various ex-situ analysis technologies.This work demonstrates that the p-VO x @C has great potential for applications in aqueous ZIBs after electrochemical activation.

Flexible thermoelectric generators offer the possibility of harvesting waste heat from the human body. However, intrinsic brittleness and the high production cost of bulk thermoelectric materials limit their applications in flexible thermoelectric generators. Herein, flexible Ag2Se/carbon nanocomposite films on polyimide substrates are prepared by scalable screen-printing followed by facial heat treatment. An optimal film shows a maximum power factor of 1617 mu W m(-1) K-2 at room temperature and good flexibility. The film consists of mainly Ag2Se grains with a preferred (00l)-orientation and a small amount of carbon. Microstructure observations reveal that the Ag2Se grains with sizes of nano to micrometers have coherent or continuous grain boundaries, and the carbon is mainly amorphous with slight graphitization. A flexible thermoelectric device assembled with the optimal film exhibits a power density of 29.1 W/m(2) at a temperature gradient of 35.4 K. This work demonstrates a cost-effective route to high-performance flexible thermoelectric films.