Thermoelectric materials can be used as the active materials in thermoelectric generators and as Peltier coolers for direct energy conversion between heat and electricity. Apart from inorganic ...thermoelectric materials, thermoelectric polymers have been receiving great attention due to their unique advantages including low cost, high mechanical flexibility, light weight, low or no toxicity, and intrinsically low thermal conductivity. The power factor of thermoelectric polymers has been continuously rising, and the highest ZT value is more than 0.25 at room temperature. The power factor can be further improved by forming composites with nanomaterials. This article provides a review of recent developments on thermoelectric polymers and polymer composites. It focuses on the relationship between thermoelectric properties and the materials structure, including chemical structure, microstructure, dopants, and doping levels. Their thermoelectric properties can be further improved to be comparable to inorganic counterparts in the near future.
Thermoelectric polymers have gained great attention, arising from their merits of low cost, light weight, low or no toxicity, and high mechanical flexibility. This article provides a review on the recent progress of thermoelectric polymers and composites.
For the first time, successful fabrication of the cotton aerogels and cotton-cellulose aerogels is achieved using recycled fibers from environmental waste for oil absorption. The pure cotton and ...cotton-cellulose aerogels are obtained using a cost-effective mixing-blending method with polyamide-epichlorohydrin as strengthening additives. The obtained aerogels are silanized using methyltrimethoxysilane via a facile chemical vapor deposition to endow aerogels with hydrophobic surface. Effects of fiber concentrations and cotton-to-cellulose mass ratio on oil absorption performance in various solvents are also investigated. The cotton aerogel with an initial concentration of 0.25wt% presents the highest oil absorption capacity over 100gg−1. Besides, the cotton/cellulose aerogels also demonstrate good absorption capacity in different pollutant organics. The absorption kinetics of the aerogels with different cotton concentrations are also investigated using pseudo first-order model. Both equilibrium absorption and absorption kinetics demonstrate cotton/cellulose aerogels as promising materials for oil absorption and environmental pollution treatment.
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•Cotton aerogel with absorption capacity over 100gg−1 was prepared through simple solution routine.•Silanized cotton and cotton/cellulose aerogel present good hydrophobicity.•Cotton/cellulose aerogels show remarkable absorption capacity in various contaminates.•Cellulose helps to improve absorption reversibility for the composite aerogels.
How to effectively match the relationship between users’ perceptual demands and the characteristics of industrial robot modules becomes a pressing issue when perceptual demands become a significant ...determinant of whether users purchase and employ industrial robots. In this regard, we propose a Kansei Engineering-based method for industrial robot module configuration, using the module design of a glass substrate transfer robot as an example. First, the method analyzes the perceptual demand characteristics of the target user, utilizing the semantic difference method, and then establishes a mapping relationship between the user’s perceptual demand and the robot design elements, utilizing the hierarchical inference method. On the basis of this mapping relationship, the robot module for transfer glass substrates is then designed. Finally, orthogonal design and conjoint analysis were used to effectively and objectively analyze user preferences for various module configuration alternatives. The results indicate that the industrial robot’s shape, color, and material are the three appearance characteristics that influence the user’s perceptual demands. The slender, rigid design features of the industrial robot, such as the streamlined drive shaft, lengthwise expanded body structure, integrated body structure, and hidden plugs, as well as the simple color scheme and smooth metal surface, are key elements in the industrial robot’s perceptual design. The turn shaft module and lift shaft module have respective weights of 35.040% and 31.120%, determining whether the glass substrate transfer robot can create a simple style. In the context of the widespread use of industrial robot modules, the methods and findings of this study offer new ideas for the design of industrial robot modules and broaden the research and applications of Kansei Engineering in module design.
Thermoelectric materials can be utilized to directly convert heat into electricity. This is particularly important for harvesting waste heat that is abundant on earth. But their thermoelectric ...performance is still not high enough for practical heat‐to‐electricity conversion after being studied for about 200 years. Instead of enhancing the figure of merit (ZT) of thermoelectric materials, a significant improvement in heat harvesting by constructing a hybrid ionic/electronic thermoelectric converter (HTEC) is demonstrated. The device consists of an electronic unit and an ionic unit. The electronic unit is made of a thermoelectric polymer, poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), and the ionic unit is composed of an ionogel. In addition to the heat‐to‐electricity conversion by the electronic unit from a temperature gradient due to the Seebeck effect, the ionic unit can generate electricity from temperature fluctuations owing to thermal ionic diffusion (Soret effect). The power generation can be many times more than the control thermoelectric generator using PEDOT:PSS. Because the temperature of waste heat usually fluctuates, the HTECs can give rise to much higher heat‐to‐electricity power conversion than normal thermoelectric generators with electronic conductors only.
A hybrid ionic/electronic thermoelectric converter (HTEC) is demonstrated. It consists of an electronic layer and an ionic layer. The electronic layer can convert heat into electricity from a temperature gradient, and the ionic layer can generate electricity from temperature fluctuations. The power generation can be many times more than of the control thermoelectric generator using PEDOT:PSS.
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•Continuous power generation by ITECs is demonstrated.•Continuous ITECs can supply comparable or even higher specific average power than conventional intermittent ITECs.•An equivalent ...circuit is proposed for the ITECs.•Expressions are derived for the performance of ITECs.
Ionic conductors emerged as the next-generation thermoelectric (TE) materials mainly due to their high thermopower, which is higher than that of the electronic conductors by 1–2 orders in magnitude. However, they cannot be directly used in TE generators (TEGs) because ions cannot transport across the electrodes into the external circuit. Instead, they can be used in ionic TE capacitors (ITECs) to harvest heat. Nevertheless, the ITECs reported in literatures are operated in an intermittent mode, and repeated connection and disconnection to the external load are required. These severely affect their application in practice. Here, we demonstrate the continuous operation of ITECs with the external load always connected. In addition, an equivalent circuit is proposed for the ITECs in the continuous mode, which can account for the TE parameters like the peak voltage and voltage decay time constant. The continuous ITEC can supply comparable power or even higher performance than the control intermittent ITEC, depending on the temperature variation. This work is significant for the practical application of ionic TE materials in heat conversion and the sustainable development of human society.
Thermoelectric (TE) materials are significant for sustainable development because they can be used to directly harvest heat into electricity. Recently, ionic TE materials emerged as very promising ...materials mainly due to their high thermovoltage that can be higher than the Seebeck coefficient of electronic TE materials by 2–3 orders in magnitude. However, their conductivity is very low. Here, the significant improvement in the ionic conductivity and thus the overall TE properties of ionogels is reported by engineering their solid networks, which immobilize the ionic liquid in the ionogels. An antisolvent of poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) is added into the acetone solution of 1‐ethyl‐3‐methylimidazolium dicyanamide (EMIM:DCA) that is an ionic liquid and PVDF‐HFP prior to the ionogel formation. This can significantly change the solid networks formed by PVDF‐HFP and thus the microstructure of the EMIM:DCA/PVDF‐HFP ionogels, thereby facilitating ionic transport. As a result, the ionic conductivity of the ionogels can be increased from 7.0 to 17.6 mS cm−1. The ionogels can exhibit a high ionic figure of merit (ZTi) of 1.8 with the ionic Seebeck coefficient of 25.4 mV K−1 and the thermal conductivity of 0.190 W m−1 K−1. This is the highest recorded ZTi value for ionic conductors.
The addition of antisolvent into solution can engineer the solid networks and the microstructure of ionogels. This can greatly increase the ionic conductivity and thus the overall thermoelectric properties of ionogels. The ionic conductivity can be increased from 7.0 to 17.6 mS cm−1, and the ionogels can exhibit a high ionic figure of merit (ZTi) of 1.8.
Thermoelectric materials can be used to harvest low‐grade heat that is otherwise dissipated to the environment. But the conventional thermoelectric materials that are semiconductors or semimetals, ...usually exhibit a Seebeck coefficient of much less than 1 mV K−1. They are expensive and consist of toxic elements as well. Here, it is demonstrated environmental benign flexible quasi‐solid state ionogels with giant Seebeck coefficient and ultrahigh thermoelectric properties. The ionogels made of ionic liquids and poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) can exhibit a giant Seebeck coefficient up to 26.1 mV K−1, the highest for electronic and ionic conductors. In addition, they have a high ionic conductivity of 6.7 mS cm−1 and a low thermal conductivity of 0.176 W m−1 K−1. Their thermoelectric figure of merit (ZT) is thus 0.75. The giant Seebeck coefficient is related to the ion‐dipole interaction between PVDF‐HFP and ionic liquids. Their application in ionic thermoelectric capacitors is also demonstrated for the conversion of intermittent heat into electricity. They are especially important to harvest the low‐grade thermal energy that is abundant on earth.
Ionogels composed of polymer networks and ionic liquids are prepared and studied for thermoelectric conversion. They can exhibit an ionic Seebeck coefficient up to 26 mV K−1, the highest for electronic and ionic conductors. In addition, they can have high ionic conductivity whereas low thermal conductivity. Thus, they can exhibit a high ZT value of 0.75.
Stretchable electronic materials and devices have important applications in flexible electronic systems including wearable electronics and bioelectronics. Convenient electricity generation such as ...thermoelectric conversion is required for the flexible electronic systems. Hence, it is development of high‐performance thermoelectric materials with high mechanical stretchability would be highly desirable. Here, stretchable and transparent ionogels with high thermoelectric properties are demonstrated. The ionogels made of elastomeric waterborne polyurethane and 1‐ethyl‐3‐methylimidazolium dicyanamide (EMIM:DCA, an ionic liquid) are prepared by solution processing. Their mechanical and electrical properties depend on the loading of EMIM:DCA. The ionogels with 40 wt% EMIM:DCA can have a high mechanical stretchability of up to 156%, low tensile strength of 0.6 MPa, and low Young's modulus of 0.6 MPa. They also exhibit a high ionic thermovoltage of 34.5 mV K−1, high ionic conductivity of 8.4 mS cm−1 and low thermal conductivity of 0.23 W m−1 K−1 at a relative humidity of 90%. As a result, it can have a high ionic figure of merit (ZTi) of 1.3 ± 0.2. Both the thermovoltage and the ZTi value are the highest for stretchable thermoelectric materials. They can be used in ionic thermoelectric capacitors to convert heat into electricity.
Ionogels of WPU and 1‐ethyl‐3‐methylimidazolium dicyanamide (EMIM:DCA, an ionic liquid) have high thermoelectric performance, high mechanical stretchable, and high optical transparency. They have a high mechanical stretchability of up to 156% and high ionic thermovoltage of 34.5 mV K−1. Their ionic figure of merit (ZTi) can be up to 1.3 ± 0.2.
Abstract
To efficiently harvest the abundant waste heat on earth is of great significance for sustainable development. Thermoelectric materials can be used to directly convert heat into electricity, ...and ionic thermoelectric materials like ionic liquids (ILs) are considered as the next‐generation thermoelectric materials. It is important to develop novel methods to improve the overall thermoelectric properties particularly the thermopower. Herein, the great enhancement in the thermopower of 1‐ethyl‐3‐methylimidazolium dicyanamide (EMIM:DCA) is reported that is an IL by introducing zeolitic imidazolate framework (ZIF‐8) that is a metal‐organic framework (MOF) for the first time. The presence of 40 wt.% ZIF‐8 can greatly increase the ionic thermopower of EMIM:DCA from 8.8 to 31.9 mV K
−1
at room temperature, and the ZIF‐8/EMIM:DCA mixture at the ZIF‐8 loading of 10 wt.% can exhibit a
ZT
i
value of 3.1, notably higher than that (0.59) of neat EMIM:DCA. The enhancement in the thermopower is attributed to the increase in the difference of the mobilities of EMIM
+
and DCA
−
by ZIF‐8. Because DCA
−
is smaller while EMIM
+
is larger than the pore size of ZIF‐8, the DCA
−
transport is hindered by ZIF‐8, while EMIM
+
can bypass ZIF‐8.
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