As practical interest in flexible/or wearable power-conversion devices increases, the demand for high-performance alternatives to thermoelectric (TE) generators based on brittle inorganic materials ...is growing. Herein, we propose a flexible and ultralight TE generator (TEG) based on carbon nanotube yarn (CNTY) with excellent TE performance. The as-prepared CNTY shows a superior electrical conductivity of 3147 S/cm due to increased longitudinal carrier mobility derived from a highly aligned structure. Our TEG is innovative in that the CNTY acts as multifunctions in the same device. The CNTY is alternatively doped into n- and p-types using polyethylenimine and FeCl3, respectively. The highly conductive CNTY between the doped regions is used as electrodes to minimize the circuit resistance, thereby forming an all-carbon TEG without additional metal deposition. A flexible TEG based on 60 pairs of n- and p-doped CNTY shows the maximum power density of 10.85 and 697 μW/g at temperature differences of 5 and 40 K, respectively, which are the highest values among reported TEGs based on flexible materials. We believe that the strategy proposed here to improve the power density of flexible TEG by introducing highly aligned CNTY and designing a device without metal electrodes shows great potential for the flexible/or wearable power-conversion devices.
As commercial interest in flexible power‐conversion devices increases, the demand for high‐performance alternatives to brittle inorganic thermoelectric (TE) materials is growing. As an alternative, ...we propose a rationally designed graphene/polymer/inorganic nanocrystal free‐standing paper with high TE performance, high flexibility, and mechanical/chemical durability. The ternary hybrid system of the graphene/polymer/inorganic nanocrystal includes two heterojunctions that induce double‐carrier filtering, which significantly increases the electrical conductivity without a major decrease in the thermopower. The ternary hybrid shows a power factor of 143 μW m−1 K−1 at 300 K, which is one to two orders of magnitude higher than those of single‐ or binary‐component materials. In addition, with five hybrid papers and polyethyleneimine (PEI)‐doped single‐walled carbon nanotubes (SWCNTs) as the p‐type and n‐type TE units, respectively, a maximum power density of 650 nW cm−2 at a temperature difference of 50 K can be obtained. The strategy proposed here can improve the performance of flexible TE materials by introducing more heterojunctions and optimizing carrier transfer at those junctions, and shows great potential for the preparation of flexible or wearable power‐conversion devices.
A rationally designed graphene/polymer/inorganic nanocrystal free‐standing paper is demonstrated. The free‐standing paper has a high thermoelectric performance, high flexibility, and mechanical/chemical durability for flexible thermoelectric materials. The paper features two heterojunctions that induce double‐carrier filtering, thus increasing the electrical conductivity without a major decrease in the thermopower. This shows great potential for the preparation of flexible or wearable power‐conversion devices.
Recently, with the fourth industrial revolution, the research cases that search for optimal design points based on neural networks or machine learning have rapidly increased. In addition, research on ...optimization is continuously reported in the field of fuel cell research using hydrogen as fuel. However, in the case of optimization research, it often requires a large amount of training data, which means that it is more suitable for numerical research such as CFD simulation rather than time-consuming research such as actual experiments. As is well known, the design range of fuel cell flow channels is extremely small, ranging from hundreds of microns to several millimeters, which means the small tolerance could cause fatal performance loss. In this study, the general optimization study was further improved in terms of reliability by considering stochastic tolerances that may occur in actual industry. The optimization problem was defined to maximize stack power, which is employed as objective function, under the constraints such as pressure drop and current density standard deviation; the performance of the optimal point through general optimization was about 3.252 kW/L. In the reliability-based optimization problem, the boundary condition for tolerance was set to 0.1 mm and tolerance was assumed to occur along a normal distribution. The optimal point to secure 99% reliability for the given constraints was 2.918 kW/L, showing significantly lower performance than the general optimal point.
A layer-by-layer deposition of two conducting polymers, each layer of which is a few tenths of nanometer thick, has been successfully performed to enhance the thermoelectric power factor of organic ...thin films, which are critical components of flexible thermoelectric energy harvesting devices. The multilayer films were deposited via multiple solution processes, which exhibit enhanced electrical conductivity without any significant degradation of the Seebeck coefficient, in contrast to a coupling behavior between the electrical conductivity and the Seebeck coefficient in bulk materials. The electrical conductivity and power factor-proportional to the electrical conductivity-of 5(PEDOT:PSS/PANI-CSA) multilayer films are 1.3 and 2 times higher than those of a single PEDOT:PSS layer. Transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) reveal distinct interfaces through which an enhanced electrical conductivity and power factor have been achieved in our multilayer films. From the TEM, EELS, and Raman analyses, a model for the enhancement of the electrical conductivity has been proposed. The enhancement of electrical conductivity occurs via stretching of PEDOT and PANI chains and hole diffusion from the PANI-CSA layer to the PEDOT:PSS layer. The band alignment in the multilayer structure not only enhances electrical conductivity but also maintains the Seebeck coefficient at an optimum value. Our study suggests that the layer-by-layer deposition of polymer thin films is a promising technique for manipulating the thermoelectric properties of each polymer component to enhance thermoelectric performance.
Laser three-dimensional (3D) manufacturing technologies have gained substantial attention to fabricate 3D structured electrochemical rechargeable batteries. Laser 3D manufacturing techniques offer ...excellent 3D microstructure controllability, good design flexibility, process simplicity, and high energy and cost efficiencies, which are beneficial for rechargeable battery cell manufacturing. In this review, notable progress in development of the rechargeable battery cells via laser 3D manufacturing techniques is introduced and discussed. The basic concepts and remarkable achievements of four representative laser 3D manufacturing techniques such as selective laser sintering (or melting) techniques, direct laser writing for graphene-based electrodes, laser-induced forward transfer technique and laser ablation subtractive manufacturing are highlighted. Finally, major challenges and prospects of the laser 3D manufacturing technologies for battery cell manufacturing will be provided.
As future thermoelectric generators (TEGs) require flexibility and mass-producibility, the demand for high-performance TEGs based on printed thermoelectric (TE) materials is growing. Herein, we have ...rationally designed a bracelet-type TEG structure where the carbon nanotube (CNT) ink is printed in the in-plane direction of a flexible cable and the device is operated in the out-of-plane direction of the heat source. This is the first report to fabricate a flexible TEG by printing the TE ink on a curved surface. For printing the CNT ink on a curved surface, the viscosity, dispersibility, and TE performance of the CNT ink have been fundamentally studied. Especially, the mechanism of the solvent effect on the dispersion and viscosity of the CNT ink during planetary ball milling has been clarified. The flexible TEG based on 60 pairs of n- and p-doped CNT ink shows the maximum power output of 1.95 μW at a temperature difference of 30 K, which is one of the highest power outputs for flexible TEGs based on CNT inks. The ease of installment of the bracelet-type TEG on heat sources with various shapes and its ability to harvest waste heat in the out-of-plane direction of the heat source has great potential as flexible/or wearable power conversion devices.
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► We used a simultaneous incorporating method to introduce magnetic nanoparticles effectively during biosynthesis of BC. ► The non-ionic amphiphilic comb-like polymer was adopted to ...form a stable dispersion of nanoclusters effectively. ► An electrically conducting magnetic BC membrane was successfully prepared. ► The process can be applied to manufacture other functional biomaterials with the controlled dispersion of nanoclusters.
Magnetic BC was biosynthesized by culturing Gluconacetobacter xylinus in a medium containing magnetite nanoparticle (MNP) clusters. The stable dispersion of MNP clusters in an aqueous solution was achieved using amphiphilic comb-like polymer (CLP) stabilizers to disperse the MNPs. Subsequently, a conducting polymer was synthesized on the magnetic BC fibers by the chemical oxidative polymerization of aniline. The BC fiber was fully coated with polyaniline, forming hydrogen bonds. The colloidal stability of the CLP-modified MNPs was characterized by optical imaging and UV–visible spectroscopy. The chemical structure and morphology of the hybrid BC layers were observed using Fourier transform infrared spectroscopy and scanning electron microscopy. Magnetic and conductive properties were measured to confirm the immobilization of MNPs and polyaniline.
An absorption chiller model for tri-generation (combined cooling, heating, and power) is developed and incorporated with the high temperature- (HT-) proton exchange membrane fuel cell (PEMFC) system ...model that was developed in our previous study. We employ a commercially available flow simulator, Aspen HYSYS, for solving the energy and mass balances of various system components, including an HT-PEMFC stack that is based on a phosphoric acid-doped PBI membrane, natural gas-fueled reformer, LiBr-H2O absorption chiller, balance of plant (BOP) components, and heat exchangers. Since the system’s operating strategy for tri-generation must be changed, depending on cooling or heating loads, a major focus of this study is to analyze system performance and efficiency under different requirements of electricity generation, cooling, and heating conditions. The system simulation results revealed that high-current fuel-cell operation is essential in raising the cooling capacity, but the overall system efficiency is slightly reduced as a result. Using a lower fuel-air ratio for the burner in the reforming module is one alternative that can minimize the reduction in the overall system efficiency under high-current fuel-cell operation and large cooling-capacity modes.
A high-performance, wearable thermoelectric generator (TEG) was fabricated with a highly aligned carbon nanotube (CNT) sheet. The aligned CNT sheet exhibits extraordinary electrical conductivity ...compared to disordered CNT sheets and also can be directly fabricated as a continuous TEG without metal electrode interconnects. This provides a significant reduction in contact resistance between TE legs and electrodes compared to traditional TEGs, resulting in higher power output. In addition, the continuity of the module without any disconnected parts provides high degrees of mechanical stability and durability. This robust and scalable approach to flexible TEG fabrication paves the way for CNT applications in lightweight, flexible, and wearable electronics.
•The tellurium nanowire films hybridized with SWCNT has been proposed.•The mechanical stability of SWCNT improves the flexibility of hybrid films.•The high electrical conductivity of SWCNT enhances ...the thermoelectric property.•The hybrid film with 2wt% SWCNT shows the best thermoelectric property.
Thermoelectrics is a challenging issue for future energy harvesting and cooling technology. We here have demonstrated a new system of the tellurium nanowire (TeNW) films hybridized with single-walled carbon nanotube (SWCNT) as a flexible thermoelectric material and investigated their thermoelectric properties as a function of SWCNT weight ratio in the hybrid. The excellent mechanical stability and electrical conductivity of SWCNT enhance the flexibility and thermoelectric properties of the pure TeNW film. The addition of 2wt% SWCNT into TeNW matrix significantly increases the electrical conductivity from 4 to 50Sm−1 while maintaining the high thermopower, thereby leading to one order of magnitude higher figure of merit (ZT) compared to the pure TeNW film. These results indicate that the SWCNT/TeNW hybrid film would be promising for a potential use as a flexible thermoelectric material.
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