Explore the vast range of titles available.

The performances of rechargeable batteries are strongly affected by the operating environmental temperature. In particular, low temperatures (e.g., ≤0 °C) are detrimental to efficient cell cycling. To circumvent this issue, we propose a few-layer Bi 2 Se 3 (a topological insulator) as cathode material for Zn metal batteries. When the few-layer Bi 2 Se 3 is used in combination with an anti-freeze hydrogel electrolyte, the capacity delivered by the cell at −20 °C and 1 A g −1 is 1.3 larger than the capacity at 25 °C for the same specific current. Also, at 0 °C the Zn | |few-layer Bi 2 Se 3 cell shows capacity retention of 94.6% after 2000 cycles at 1 A g −1 . This behaviour is related to the fact that the Zn-ion uptake in the few-layer Bi 2 Se 3 is higher at low temperatures, e.g., almost four Zn 2+ at 25 °C and six Zn 2+ at −20 °C. We demonstrate that the unusual performance improvements at low temperatures are only achievable with the few-layer Bi 2 Se 3 rather than bulk Bi 2 Se 3 . We also show that the favourable low-temperature conductivity and ion diffusion capability of few-layer Bi 2 Se 3 are linked with the presence of topological surface states and weaker lattice vibrations, respectively. The performances of rechargeable batteries are detrimentally affected by low temperatures (e.g., < 0 °C). Here, the authors report a few-layer Bi2Se3 material capable of improving battery cycling performances when operational temperatures are shifted from +25 °C to −20 °C.

The formula for maximum efficiency ( η ₘₐₓ) of heat conversion into electricity by a thermoelectric device in terms of the dimensionless figure of merit ( ZT ) has been widely used to assess the desirability of thermoelectric materials for devices. Unfortunately, the η ₘₐₓ values vary greatly depending on how the average ZT values are used, raising questions about the applicability of ZT in the case of a large temperature difference between the hot and cold sides due to the neglect of the temperature dependences of the material properties that affect ZT . To avoid the complex numerical simulation that gives accurate efficiency, we have defined an engineering dimensionless figure of merit ( ZT ) ₑₙg and an engineering power factor ( PF ) ₑₙg as functions of the temperature difference between the cold and hot sides to predict reliably and accurately the practical conversion efficiency and output power, respectively, overcoming the reporting of unrealistic efficiency using average ZT values.

Nanocomposite engineering decouples the transport of phonons and electrons. This usually involves the in-situ formation or ex-situ addition of nanoparticles to a material matrix with hetero-composition and hetero-structure ( he C- he S) interfaces or hetero-composition and homo-structure ( he C- ho S) interfaces. Herein, a quasi homo-composition and hetero-structure ( ho C- he S) nanocomposite consisting of Pnma Bi 2 SeS 2 - Pnnm Bi 2 SeS 2 is obtained through a Br dopant-induced phase transition, providing a coherent interface between the Pnma matrix and Pnnm second phase due to the slight structural difference between the two phases. This ho C- he S nanocomposite demonstrates a significant reduction in lattice thermal conductivity (~0.40 W m −1 K −1 ) and an enhanced power factor (7.39 μW cm −1 K −2 ). Consequently, a record high figure-of-merit ZT max  = 1.12 (at 773 K) and a high average figure-of-merit ZT ave  = 0.72 (in the range of 323–773 K) are achieved. This work provides a general strategy for synergistically tuning electrical and thermal transport properties by designing ho C- he S nanocomposites through a dopant-induced phase transition. Most of the thermoelectric nanocomposites have structure character of a hetero-composition and hetero-structure, or hetero-composition and homo-structure between matrix phase and dispersion phase. This work shows a quasi homo-composition and hetero-structure ( ho C- he S) nanocomposite consisting of Pnma  Bi 2 SeS 2  -  Pnnm  Bi 2 SeS 2 with high ZT.

Ferroelectric polymers have great potential applications in mechanical/thermal sensing, but their sensitivity and detection limit are still not outstanding. We propose interface engineering to improve the charge collection in a ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) copolymer (P(VDF-TrFE)) thin film via cross-linking with poly(3,4-ethylenedioxythiophene) doped with polystyrenesulfonate (PEDOT:PSS) layer. The as-fabricated P(VDF-TrFE)/PEDOT:PSS composite film exhibits an ultrasensitive and linear mechanical/thermal response, showing sensitivities of 2.2 V kPa −1 in the pressure range of 0.025–100 kPa and 6.4 V K −1 in the temperature change range of 0.05–10 K. A corresponding piezoelectric coefficient of −86 pC N −1 and a pyroelectric coefficient of 95 μC m −2 K −1 are achieved because more charge is collected by the network interconnection interface between PEDOT:PSS and P(VDF-TrFE), related to the increase in the dielectric properties. Our work shines a light on a device-level technique route for boosting the sensitivity of ferroelectric polymer sensors through electrode interface engineering. The piezoelectric and pyroelectric coefficients of ferroelectric materials are critical to improving the sensitivity and detection limit in sensing. Here, the authors report an interface engineering strategy using a PEDOT:PSS penetrating electrode, that realizes high pressure and temperature sensitivity.

Mg 3 (Sb,Bi) 2 is a promising thermoelectric material suited for electronic cooling, but there is still room to optimize its low-temperature performance. This work realizes >200% enhancement in room-temperature zT by incorporating metallic inclusions (Nb or Ta) into the Mg 3 (Sb,Bi) 2 -based matrix. The electrical conductivity is boosted in the range of 300–450 K, whereas the corresponding Seebeck coefficients remain unchanged, leading to an exceptionally high room-temperature power factor >30 μW cm −1 K −2 ; such an unusual effect originates mainly from the modified interfacial barriers. The reduced interfacial barriers are conducive to carrier transport at low and high temperatures. Furthermore, benefiting from the reduced lattice thermal conductivity, a record-high average zT  > 1.5 and a maximum zT of 2.04 at 798 K are achieved, resulting in a high thermoelectric conversion efficiency of 15%. This work demonstrates an efficient nanocomposite strategy to enhance the wide-temperature-range thermoelectric performance of n-type Mg 3 (Sb,Bi) 2 , broadening their potential for practical applications. The utilization of Mg 3 (Sb,Bi) 2 in thermoelectric devices is hindered by its low performance near room temperature. Here, authors report thermoelectric performance enhancement of Mg 3 (Sb,Bi) 2 within a wide temperature range by incorporating metallic inclusions at grain boundaries. (279 in total)

Ionic thermoelectric (i-TE) liquid cells offer an environmentally friendly, cost effective, and easy-operation route to low-grade heat recovery. However, the lowest temperature is limited by the freezing temperature of the aqueous electrolyte. Applying a eutectic solvent strategy, we fabricate a high-performance cryo-temperature i-TE liquid cell. Formamide is used as a chaotic organic solvent that destroys the hydrogen bond network between water molecules, forming a deep eutectic solvent that enables the cell to operate near cryo temperatures (down to –35 °C). After synergistic optimization of the electrode and cell structure, the as-fabricated liquid i-TE cell with cold (–35 °C) and hot (70 °C) ends achieve a high power density (17.5 W m −2 ) and a large two-hour energy density (27 kJ m −2 ). In a prototype 25-cell module, the open-circuit voltage and short-circuit current are 6.9 V and 68 mA, respectively, and the maximum power is 131 mW. The anti-freezing ability and high output performance of the as-fabricated i-TE liquid cell system are requisites for applications in frigid regions. The authors make an ionic thermoelectric cell with a eutectic solvent of formamide that can operate at temperatures as low as −35 °C by applying hydrophilic and gold coated treatments to the electrode and introducing a thermal separator.

From an environmental perspective, lead-free SnTe would be preferable for solid-state waste heat recovery if its thermoelectric figure-of-merit could be brought close to that of the lead-containing chalcogenides. In this work, we studied the thermoelectric properties of nanostructured SnTe with different dopants, and found indium-doped SnTe showed extraordinarily large Seebeck coefficients that cannot be explained properly by the conventional two-valence band model. We attributed this enhancement of Seebeck coefficients to resonant levels created by the indium impurities inside the valence band, supported by the first-principles simulations. This, together with the lower thermal conductivity resulting from the decreased grain size by ball milling and hot pressing, improved both the peak and average nondimensional figure-of-merit (ZT) significantly. A peak ZT of ∼1.1 was obtained in 0.25 atom % In-doped SnTe at about 873 K.

The lack of desirable diffusion barrier layers currently prohibits the long-term stable service of bismuth telluride thermoelectric devices in low-grade waste heat recovery. Here we propose a new design principle of barrier layers beyond the thermal expansion matching criterion. A titanium barrier layer with loose structure is optimized, in which the low Young’s modulus and particle sliding synergistically alleviates interfacial stress, while the TiTe 2 reactant enables metallurgical bonding and ohmic contact between the barrier layer and the thermoelectric material, leading to a desirable interface characterized by high-thermostability, high-strength, and low-resistivity. Highly competitive conversion efficiency of 6.2% and power density of 0.51 W cm −2 are achieved for a module with leg length of 2 mm at the hot-side temperature of 523 K, and no degradation is observed following operation for 360 h, a record for stable service at this temperature, paving the way for its application in low-grade waste heat recovery. The lack of desirable barrier layers prohibits the power generation applications of bismuth telluride thermoelectric devices. Here, the authors construct a kind of Ti barrier layer with high strength and low resistivity with a module exhibiting high thermal stability during the service at 523 K.

Thermoelectric power generation is one of the most promising techniques to use the huge amount of waste heat and solar energy. Traditionally, high thermoelectric figure-of-merit, ZT , has been the only parameter pursued for high conversion efficiency. Here, we emphasize that a high power factor ( PF ) is equivalently important for high power generation, in addition to high efficiency. A new n-type Mg ₂Sn-based material, Mg ₂Sn ₀.₇₅Ge ₀.₂₅, is a good example to meet the dual requirements in efficiency and output power. It was found that Mg ₂Sn ₀.₇₅Ge ₀.₂₅ has an average ZT of 0.9 and PF of 52 μW⋅cm ⁻¹⋅K ⁻² over the temperature range of 25–450 °C, a peak ZT of 1.4 at 450 °C, and peak PF of 55 μW⋅cm ⁻¹⋅K ⁻² at 350 °C. By using the energy balance of one-dimensional heat flow equation, leg efficiency and output power were calculated with T ₕ = 400 °C and T c = 50 °C to be of 10.5% and 6.6 W⋅cm ⁻² under a temperature gradient of 150 °C⋅mm ⁻¹, respectively. Significance Thermoelectric materials have been extensively studied for applications in conversion of waste heat into electricity. The efficiency is related to the figure-of-merit, ZT = ( S ²σ / κ ) T , where S , σ , and κ are the Seebeck coefficient, electrical conductivity, and thermal conductivity, respectively. Pursuing higher ZT for higher efficiency has been the focus by mainly reducing the thermal conductivity. In this paper, we point out, for a given ZT , higher power factor ( S ²σ ) should be pursued for achieving more power because power is determined by ( T ₕ − T c) ²( S ²σ )/ L , where T ₕ, T c, and L are the hot and cold side temperatures, and leg length, respectively. We found a new material, Mg ₂Sn ₀.₇₅Ge ₀.₂₅, having both high ZT and high power factor.

The rising demand for sustainable energy solutions has promoted significant interest in ionic thermoelectric materials, which convert low-grade waste heat into electrical energy through spatial temperature gradients. However, diurnal temperature variations, which offer potential for location-independent time-domain thermal energy, remain largely unexplored. To overcome the challenges of harvesting spatially limited thermal energy, this study presents an ionic thermoelectric cycle (t-ITC) designed for time-domain thermal energy harvesting, incorporating two gels with contrasting temperature coefficients. A temperature-adaptive self-regeneration (TASR) strategy is proposed to set the critical regeneration temperature ( T CR ) at the midpoint of temperature fluctuations, facilitating long-term device operation. The regeneration criteria are defined as neutralization of the electrochemical potential difference between separated cells, and a method based on shared counter-ion self-balancing is introduced. Employing a polyacrylamide-polyvinylpyrrolidone (PAM-PVP) matrix with KI 3 /KI and K 3 Fe(CN) 6 /K 4 Fe(CN) 6 redox couples, both utilizing the same counter-ion K + for regeneration, the t-ITC device attains a peak energy density of 3.28 kJ m –2 per cycle and a relative Carnot efficiency of 8.39% with 70% heat recuperation, under cycling conditions between 60 °C and 10 °C. This work highlights the potential of t-ITC devices for global-scale time-domain thermal energy on a global scale, across diverse environments, such as hot deserts and cold plateaus. The authors present a PAM-PVP hydrogel ionic thermoelectric device using KI 3 /KI and K 3 Fe(CN) 6 /K 4 Fe(CN) 6 redox couples to harvest time-domain thermal energy without external charging, reaching 4% relative Carnot efficiency from 60 °C to 10 °C.