As one of the most promising sodium-ion battery cathodes, O3-type transition metal (TM) layered oxides (NaxTMO2) with a high specific capacity and operating voltage have received a wide attention. However, they still face the problems of slow Na+ transfer kinetics and undesirable phase transitions, and suffer from severe structural degradation when stored in a humid atmosphere. In this work, we propose a Mg/Cu co-doping strategy to synthesize NaLi0.04(Mg0.02Cu0.04Ni0.19Fe0.33Mn0.42)0.96O2 (LMCNFM) cathode. In this material, Mg serves to stabilize the layer structure and improve reversibility of the phase transitions, while Cu with Cu2+/Cu3+ redox reaction contributes to capacity and enhances moisture stability. Mg/Cu co-doping can expand the Na+ transfer channels, leading to improved rate performance. LMCNFM can deliver a specific capacity of 109.1 mAh g- 1 even at 10 C rate. Mg/Cu co-doping can stabilize the TM layer and reduce the surface side reactions with electrolyte. LMCNFM can maintain 92.7 % of its initial capacity after 200 cycles at 5 C rate. Furthermore, spontaneous extraction of Na+ when exposed to water is suppressed via Mg/Cu co-doping. After being soaked in water for 6 h, LMCNFM shows a minor structural degradation with 88.7 % capacity retained after 200 cycles at 1 C.

Research into cost-effective electrocatalysts for alkaline water and simulated seawater oxidation is paramount for advancing the conversion and storage of renewable energy. In this study, a FeSe2/Ni0.85Se catalyst with the hollow and ultrathin nanobelts structure is synthesized. The distinctive structure characteristics of FeSe2/ Ni0.85Se heterojunction nanobelts confer exceptional oxygen evolution reaction (OER) properties in diverse electrolytes, including alkaline 1 M KOH and simulated seawater (1 M KOH + 0.5 M NaCl) solutions. The FeSe2/ Ni0.85Se catalyst presents the low overpotentials of 259 and 267 mV at a current density of 10 mA cm- 2, along with the Tafel slopes of 33.7 and 65.5 mV dec- 1 in two solutions, respectively. Additionally, the FeSe2/Ni0.85Se catalyst also demonstrates good stability. This exploration introduces a promising strategy for the development of high-performance electrocatalysts in the realm of green energy, marking the significant progress towards sustainable energy solutions.

Prussian blue (PB) is regarded as a promising host for Na or K storage because of its sustainable precursor elements (e.g., Mn, Fe) and open framework structure. However, unstable structure, high crystal H2O content, and risky HCN generation restrain its practical applications. In this work, after systematical investigation of structural evolution from Na-based to K-based PB and its relationship with electrochemical properties, it is clarified that low crystal water content, high K content, and trace Na doping are essential for a robust structure and stable cycling of PB. It is found that a trace Na-doped K-based PB exhibits comprehensive properties of low crystal water content (3.2 wt%), high thermal stability (over 340 degrees C), and superior cycling stability (84.3% after 6300 cycles at 5 C). Besides, the PB can also present stable cycling under harsh conditions, such as with intermittent-overcharge/overdischarge steps (4.8 V/1.2 V, 93.3% after 2100 cycles at 5 C), in a wide voltage range (93.2% after 1000 cycles at 1.5-4.5 V/5 C), under a high rate (83.7% after 4350 cycles at 10 C), and at a high temperature (92.0% after 1650 cycles at 45 degrees C/1 C). The superior electrochemical properties are attributed to its structural robustness even under harsh conditions.

Among some practical O3-type layered oxide cathodes, NaNi1/3Fe1/3Mn1/3O2 (NFM) features a high specific capacity and moderate cyclability. However, sluggish Na+ transfer kinetics, low structural stability, and rapid capacity loss during long-term cycling, are still posing a challenge to commercial applications of this material. In this work, we propose a Mg and Cu co-doped O3-type NaMg0.02Cu0.02Ni0.33Fe0.27Mn0.36O2 (MC-NFM) with a stable structure and good cycling stability. It was found that the Mn-O bonds in MC-NFM are obviously reinforced by synergistic doping with small amounts of Mg and Cu, leading to enhanced structural robustness, decreased Na+ migration barrier, and delayed O3-P3 phase transition. As a result, longer cycle life and enhanced rate performance are achieved. MC-NFM can yield a specific capacity of 142.1 mAh g-1 at 0.1C and 116.0 mAh g- 1 at 5C, and maintain 83.6 % of its initial capacity after 400 cycles at 1C. This work provides a promising design of O3-type cathode for sodium-ion batteries.

Prussian blue (PB) is regarded as a promising cathode for sodium-ion batteries because of its sustainable precursor elements (e.g., Mn, Fe), easy preparation, and unique framework structure. However, the unstable structure and inherent crystal H2O restrain its practical application. For this purpose, a self-constructed trace Mg2+/K+ co-doped PB prepared via a sea-water-mediated method is proposed to address this problem. The Mg2+/K+ co-doping in the Na sites of PB is permitted by both thermodynamics and kinetics factors when synthesized in sea water. The results reveal that the introduced Mg2+ and K+ are immovable in the PB lattices and can form stronger K‒N and Mg‒N Coulombic attraction to relieve phase transition and element dissolution. Besides, the Mg2+/K+ co-doping can reduce defect and H2O contents. As a result, the PB prepared in sea water exhibits an extremely long cycle life (80.1% retention after 2400 cycles) and superior rate capability (90.4% capacity retention at 20 C relative to that at 0.1 C). To address its practical applications, a sodium salts recycling strategy is proposed to greatly reduce the PB production cost. This work provides a self-constructed Mg2+/K+ co-doped high-performance PB at a low preparation cost for sustainable, large-scale energy storage.

LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) is considered as a promising cathode for high-energy-density solid-sate Li metal battery for its high theoretical capacity. However, the high oxidizability and structural instability during charge limit its practical applications. In this work, 1% (in mass) of nanosized Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) was coated on NCM811 to enhance its electrochemical stability with a ceramic/polymer composite electrolyte. A robust, ultrathin (11 mm) composite electrolyte film was prepared by combining poly(vinylidene fluoride) (PVDF) with polyethylene oxide (PEO)-Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZTO). An in-situ polymerization process was used to enhance the interface between the PVDF/PEO-LLZTO (PPL) composite electrolyte and the LATP-coated NCM811 (LATP-NCM811). Coin-type Li|LATP-NCM811 cell with the PPL electrolyte exhibits stable cycling with an 81% capacity retention after 100 cycles at 0.5 C. Pouch-type cell was also fabricated, which can be stably cycled for 70 cycles at 0.5 C/1.0 C (80% retention), and withstand abuse tests of bending, cutting and nail penetration. This work provides an applicable method to fabricate solid-state Li metal batteries with high performance. (c) 2023 The Authors. Published by Elsevier B.V. on behalf of The Chinese Ceramic Society. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

In this paper, a cooling chamber of a 9 Li-ion battery pack is numerically investigated. The effect of the outlet location is studied when the inlet is fixed and changing the outlet location varies. The battery has a cylindrical shape, and the air is used as the working fluid. This study is performed for three different Richardson numbers (Ri) in the presence of forced, natural, and mixed convection flow using six different models of the air outlet. The COMSOL commercial software is employed. Changes in the outlet and inlet location of the flow have a significant effect on the rate of heat transfer and pressure drop. The results show that model 5 has the lowest and model 1 has the highest amount of pressure drop (DP). Enhancing the Ri increases DP in models 1 to 4 and decreases DP in models 5 and 6. The highest temperature of the battery pack cooling chamber corresponds to model 2, and the lowest one is related to model 6. In the Richardson 100, the Model 2 has a 41.8% higher pressure drop than the Model 5. Increasing Ri also reduces air outlet temperature for all models except model 5. Models 6 and 1 have minimum and maximum T-Ave, respectively. They have TBPMax. Models 6 and 1 have maximum and minimum Nu(Ave) of the battery pack, respectively. Increasing the Ri reduces the maximum and T-Ave of the battery pack for all models except model 2.

Bi2Te3-based thermoelectric materials are widely used in near room temperature refrigeration filed. Although Bi2Te3-based polycrystals prepared by powder metallurgy method exhibit good mechanical properties, the low room temperature dimensionless figure of merit (zT) for n-type alloys restricts their further usage. In this work, the electrical and thermal transport properties are manipulated synergistically by multi-scale hierarchical microstructure modulations in n-type Ag2Te/Bi2Te3 composites, including atomic-scale extrinsic point defects, nano-scale low-angel grain boundaries, mesoscale precipitate, and texturing. The carrier concentration is optimized by extrinsic point defects and the carrier mobility is improved due to the strengthened texture, and thus the power factor reaches a high value of 3.6 x 10(-3) Wm(-1)/K-2, which is even higher than the hot deformed counterparts. Simultaneously, the phonon scattering is enhanced by the multi-scale defects and the lattice thermal conductivity is suppressed. A high room temperature zT of similar to 1.0 and an average zT of 0.96 in the 300-500 K range with good mechanical properties are obtained without hot deformation. This work puts forward a paradigm of enhancing the thermoelectric properties via multi-scale hierarchical microstructure modulations and is significant to the industrialization of manufacturing Bi2Te3-based alloys and devices. (c) 2023 Elsevier Ltd. All rights reserved.

Atomic disorders and defects in thermoelectric semiconductors can significantly affect their electronic and phonon transport. In this work, we report the studies of Ni atomic disorder in ZrNiSn by scanning transmission electron microscopy. Three different ZrNiSn polycrystalline and single-crystalline samples were synthesized under different processes from thermodynamically non-equilibrium conditions to more equilibrium ones, as demonstrated by characterizing their phase structure and transport properties. Atomic-resolution high-angle annular-dark-field scanning transmission electron microscopy was employed to study the Ni atomic disorder. The polycrystalline sample prepared by levitation melting exhibited a strong local composition fluctuation, while the sample after further long-term annealing and the single crystal exhibited a more uniform distribution of Ni at the 4c and 4d sites. These results reveal the evolution of Ni atomic disorder in different samples that were prepared under different thermodynamic conditions, which will be helpful to understand the Ni atomic disorder and its relationship with thermoelectric transport in the representative half-Heusler system ZrNiSn.

Na-ion batteries are considered as promising battery systems for large-scale energy storage. Although Na-ion batteries exhibit enhanced low-temperature cycling performance compared with lithium-ion batteries, there is still a great challenge to overcome for practical low-temperature applications. In this work, we propose a low performance Na-ion battery composed of FeNi co-doped Mn-based Prussian cathode (FeNi-MnHCF) and a low concentration electrolyte (0.5 mol L-1) containing a small amount of 2,2,2-trifluoroethyl acetate (ETFA, 1 wt %). The introduction of ETFA could decrease the viscosity, increase ionic conductivity and change the solvation structure of the electrolyte at low temperature. ETFA could also participate in constructing a uniform, stable, and Na-ion conductive CEI layer, enabling rapid Na-ion transport and effective protection of FeNi-MnHCF. The cells with the ETFA-contained electrolyte and FeNi-MnHCF cathode exhibit excellent rate capability and long cycle life at low temperature. When being cycled at-20 degrees C, the cell with ETFA could retain 92.1 % of the capacity after 1120 cycles at 1 C. The cell could also show stable cycling after overcharge to 4.8 V or overdischarge to 1.2 V at-20 degrees C. This work sheds light on the design of long-life and robust Na-ion batteries for sustainable energy storage at low temperature.

Half‐Heusler compounds with semiconducting behavior have been developed as high‐performance thermoelectric materials for power generation. Many half‐Heusler compounds also exhibit metallic behavior without a bandgap and thus inferior thermoelectric performance. Here, taking metallic half‐Heusler MgNiSb as an example, a bandgap opening strategy is proposed by introducing the d–d orbital interactions, which enables the opening of the bandgap and the improvement of the thermoelectric performance. The width of the bandgap can be engineered by tuning the strength of the d–d orbital interactions. The conduction type and the carrier density can also be modulated in the Mg 1‐ x Ti x NiSb system. Both improved n‐type and p‐type thermoelectric properties are realized, which are much higher than that of the metallic MgNiSb. The proposed bandgap opening strategy can be employed to design and develop new half‐Heusler semiconductors for functional and energy applications.

The donor‐like effect, depicting the uncontrollable increase of electron density that can significantly alter the thermoelectric performance of both p‐type and n‐type polycrystalline Bi 2 Te 3 ‐based materials, has long been an intriguing phenomenon, while its origin is still elusive. Herein, it is found that different from the common argument, the donor‐like effect in Bi 2 Te 3 ‐based polycrystals is a result of the oxygen‐adsorption‐induced evolution of the point defects. The dominant point defect in stoichiometric zone‐melted Bi 2 Te 3 ingot is the acceptor‐like . During the fabrication of high‐strength polycrystals, the exposure of the powders to the air leads to their absorption of oxygen and the formation of secondary phase Bi 2 TeO 5 in the following sintering process. This brings about a change of local chemical equilibrium and promotes the evolution of the intrinsic point defect from acceptor‐like to donor‐like . Notably, if the fabrication process is strictly controlled to minimize oxygen adsorption, the evolution of the point defects will be avoided, whereby the donor‐like effect disappears. Consequently, a reproducible high zT value of 1.0 at 325 K can be achieved in Bi 2 Te 2.7 Se 0.3 ‐based polycrystals. These results highlight the importance of understanding the evolution of point defects, which is crucial for developing high‐performance Bi 2 Te 3 ‐based polycrystals and corresponding fabrication processes.

Wearable thermoelectric generators (TEGs), which can convert human body heat to electricity, provide a promising solution for self-powered wearable electronics. However, their power densities still need to be improved aiming at broad practical applications. Here, a stretchable TEG that achieves comfortable wearability and outstanding output performance simultaneously is reported. When worn on the forehead at an ambient temperature of 15 °C, the stretchable TEG exhibits excellent power densities with a maximum value of 13.8 µW cm-2 under the breezeless condition, and even as high as 71.8 µW cm-2 at an air speed of 2 m s-1 , being one of the highest values for wearable TEGs. Furthermore, this study demonstrates that this stretchable TEG can effectively power a commercial light-emitting diode and stably drive an electrocardiogram module in real-time without the assistance of any additional power supply. These results highlight the great potential of these stretchable TEGs for power generation applications.

Aqueous Zn-ion batteries (ZIBs) have acquired more and more attention owing to their intrinsically high safety, environmental friendliness, low cost, and high power density. However, Zn dendrite growth, side reactions, and cathode dissolution caused by the high activity of free water hamper the practical applications of ZIBs. In this work, we report an organics/H2O hybrid aqueous electrolyte that is composed of 50 wt % polyethylene glycol (PEG), 10 wt % ethanol (EtOH), and 40 wt % H2O to address these issues. This electrolyte has a combined merit of low cost, environmental friendliness, and safety, and it also ensures dendrite-free Zn stripping/plating and chemical/electrochemical stability of the manganese-based Prussian blue (Mn-PB) cathode. Daniell-type Na/Zn-ion cells assembled with Zn anode, Mn-PB cathode, and the above electrolyte exhibit long cycle life (61.1% after 9000 cycles at 5 C) and superior rate performance (56.6% retention at 50 C relative 0.5 C). Stable cycling is also realized for the pouch-type cell and cell group. Flammability tests indicate that both the electrolyte and the pouch cell with the electrolyte exhibit nonflammability. This work sheds light on the design of low-cost, safe, and sustainable electrolytes for aqueous Na/Zn hybrid batteries for sustainable energy storage.

Due to the urgent demand for lithium-ion batteries (LIBs) with a high energy density, silicon (Si) possessing an ultrahigh capacity has aroused wide attention. However, its practical application is seriously hindered by enormous volume changes of the Si anode during cycling. Developing novel binders suitable for the Si anode has proven to be an effective strategy to improve its electrochemical performance. Herein, we constructed a three-dimensional network binder, in which the polyacrylic acid (PAA) long chains are cross-linked with one kind of amino acid, lysine (Lys). The abundant polar groups in PAA/Lys enable it to tightly adhere to the Si particles via hydrogen bonds, and the cross-linked structure prevents irreversible slipping of the PAA chains upon volume variation of the particles. The Si used was obtained from a sustainable route by recycling photovoltaic waste silicon. With high elasticity and strong adhesion, the PAA/Lys binder can effectively keep the structural integrity of the Si electrode and improve its electrochemical performance. The Si electrode using the PAA/Lys binder exhibits a good cycling stability (1008 mAh g-1 at 2 A g-1 after 250 cycles). Even with a high mass loading of 3.03 mg cm-2, the Si anode can remain stable for 100 cycles at a high fixed areal capacity of 3.03 mAh cm-2. This work gives a practical method to make stable Si electrodes using sustainable Si source and environmentally friendly amino acid-based binders.

LiNi0.8Co0.1Mn0.1O2 (NCM811) is considered as a promising cathode for high-energy-density solid-sate Li metal battery for its high theoretical capacity. However, the high oxidizability and structural instability during charge limit its practical applications. In this work, 1% (in mass) of nanosized Li1.3Al0.3Ti1.7(PO4)3 (LATP) was coated on NCM811 to enhance its electrochemical stability with a ceramic/polymer composite electrolyte. A robust, ultrathin (11 μm) composite electrolyte film was prepared by combining poly(vinylidene fluoride) (PVDF) with polyethylene oxide (PEO)-Li6.5La3Zr1.5Ta0.5O12 (LLZTO). An in-situ polymerization process was used to enhance the interface between the PVDF/PEO-LLZTO (PPL) composite electrolyte and the LATP-coated NCM811 (LATP-NCM811). Coin-type Li|LATP-NCM811 cell with the PPL electrolyte exhibits stable cycling with an 81% capacity retention after 100 cycles at 0.5 C. Pouch-type cell was also fabricated, which can be stably cycled for 70 cycles at 0.5 C/1.0 C (80% retention), and withstand abuse tests of bending, cutting and nail penetration. This work provides an applicable method to fabricate solid-state Li metal batteries with high performance.

Bi2Te3-based thermoelectric materials are widely used in solid-state refrigeration near room temperature. However, the room temperature figure of merit (zT) of n-type Bi2Te3-based polycrystals produced by once sintering is always lower than 0.8. Herein, low-angle grain boundaries (LAGBs) are introduced in n-type Bi2Te2.7+xSe0.3 by a simple step-hot-pressing procedure (once sintering) and well characterized by scanning transmission electron microscopy. LAGBs consist of dislocation arrays that can effectively scatter the medium-frequency phonons and thus suppress the lattice thermal conductivity. Although LAGBs also serve as scattering centers of low-energy electrons and deteriorate the carrier mobility, they could contribute to the enhanced Seebeck coefficient owing to the increased scattering factor. Overall, the samples with LAGBs own lower electronic thermal conductivity at the same power factor level. Finally, a high room temperature zT of 0.94 is obtained in n-type Bi2Te2.7Se0.3, which is comparable to those produced by multiple-time sintering. Moreover, step-hot-pressing is also found to be effective in promoting the room temperature zT of p-type Bi2Te3-based polycrystals. This work puts forward a new and simple method to construct LAGBs in Bi2Te3-based alloys that enhances their zTs, and sheds light on the underlying mechanisms about how the LAGB affects the electrical and thermal transport properties.

Both p-type and n-type MCoSb (M = Ti, Zr, Hf) half-Heusler compounds have been found to exhibit high thermoelectric performance for power generation, but there is still a lack of research on the suitable interfacial materials to connect both p-type and n-type MCoSb for device assembly. Here, CoSi2 was selected as the electrode to connect p-type Hf0.5Zr0.5CoSb0.8Sn0.2 and n-type (Hf0.6Zr0.4)0.88Nb0.12CoSb, and the interfacial microstructure and interfacial contact resistivity were studied before and after thermal aging. In both types of thermoelectric junctions, the interface layer with a thickness from several to tens of mm is formed, which ensures a good bonding strength. The interfacial contact resistivity of both as-sintered thermoelectric junctions was less than 1 mU cm2, which rises to 3-4 mU cm2 after aging for 8 days at 1,073 K and keeps almost unchanged during the longer aging treatment. The present work demonstrates that CoSi2 is a suitable electrode material for both p- and n-type MCoSb due to the good bonding strength and the low interfacial resistivity, which paves the way for the applications of MCoSbbased TE materials.

Manganese-based Prussian blue has attracted enormous interest because of its high energy density, low cost, and easy synthesis. However, its practical use is limited for its poor rate capability and cycling performance. Here, a Mn/Ni binary Prussian blue was proposed to address this issue. The material with a 1:1 Mn/Ni ratio shows an optimized electrochemical performance when prepared via a Na2C2O4-assisted coprecipitation route at a high precursor salt concentration (0.5 mol L-1, named Mn0.5Ni0.5-0.5). Mn0.5Ni0.5-0.5 delivers a relatively high capacity of 69.4 mAh g(-1) even at a current density rate up to 100 C (69% relative to 0.1 C) and a long cycle life with 85.3% capacity retained after 700 cycles at 5 C. The material functions well at both -20 and 45 degrees C at 1 C. Stable cycling can be realized after overcharge to 4.8 V (91.8%, 300 cycles at 1 C) and overdischarge to 1.2 V (89.7%, 300 cycles at 1 C). In addition, the coin cell group assembled by series/parallel-connected single cells also shows excellent cycling performance without any battery management system. A scalable preparation of kilogram-grade Mn0.5Ni0.5-0.5 is achieved, and the pouch-type full cell made from it also exhibits stable cycling.