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Sodium super ionic conductor (NASICON) materials are considered as an attractive cathode in sodium-ion batteries. Although the three-electron reactions in Na3MnTi(PO4)3 have greatly enhanced the capacity of NASICON-structured materials, the low potential from Ti3+/4+ redox reaction and undesirable initial coulombic efficiency (ICE) have inhibited its practical application. Herein, NASICON structured Na3+2xMn1+xTi1−x(PO4)3 was designed and synthesized by the atomic-ratio-controlled method. Impressively, the increase in the Mn content not only significantly enhances the average voltage, but also increases the theoretical capacity with more than three-electron reactions. Na3+2xMn1+xTi1−x(PO4)3 can deliver an extra-high capacity of 181.4 mA h g−1 at 0.1C (1C = 150 mA h g−1), and 100.4 mA h g−1 at 10C during the rate tests. When x = 0.15 and 0.2, the energy density is up to 560.2 and 539.5 W h kg−1 at 0.1C, which is significantly higher than 442.4 W h kg−1 with x = 0, i.e. Na3MnTi(PO4)3. The capacity retention is 87.4% at 1C after 500 cycles and 83% at 5C after 1000 cycles, respectively. In addition, the ICE is as high as 89.2% after the introduction of more Na ions in the pristine structure. The structural evolution and electrochemical reaction mechanism were further confirmed by ex situ XRD, XPS and TEM. This work provides a new insight into controllable design of low cost, high capacity and energy density NASICON-structured materials for SIBs.

To improve the photocatalytic efficiency of the N₂ reduction reaction, MXene quantum dots (Ti₃C₂-QDs) and two-dimensional (2D) nickel metal–organic framework (Ni-MOF) with different ratios were fabricated by a simple self-assembly strategy to form type II heterojunctions. The resultant composites showed enhanced absorption and excellent interfacial charge-transfer capabilities according to the optical and photoelectron properties. The optimal Ti₃C₂-QD/Ni-MOF heterostructure exhibited a considerable ammonia yield rate (88.79 μmol gcₐₜ–¹ h–¹). By means of X-ray absorption near-edge fine structure (XANES) technique, it was found that the interaction of Ti₃C₂-QD and Ni-MOF could accelerate the electron transfer, and Ni site would be the main area to enrich the electron density as well as adsorb and activate N₂. Finally, with the aid of density functional theory (DFT) calculations and in situ Fourier transform infrared spectrometry (FTIR), the reaction pathway and intermediate products were studied.

Lithium–sulfur (Li–S) batteries have been attracting great attention as promising rechargeable batteries because of their large specific capacity and high energy density. However, some technical pr...

Symmetric sodium-ion batteries possess promising features such as low cost, easy manufacturing process, and facile recycling post-process, which are suitable for the application of large-scale stationary energy storage. Herein, we proposed a symmetric sodium-ion battery based on dual-electron reactions of a NASICON-structured Na3MnTi(PO4)3 material. The Na3MnTi(PO4)3 electrode can deliver a stable capacity of up to 160 mAh g-1 with a Coulombic efficiency of 97% at 0.1 C by utilizing the redox reactions of Ti3+/4+, Mn2+/3+, and Mn3+/4+. This is the first time to investigate the symmetric sodium-ion full cell using Na3MnTi(PO4)3 as both cathode and anode in the organic electrolyte, demonstrating excellent reversibility and cycling performance with voltage plateaus of about 1.4 and 1.9 V. The full cell exhibits a reversible capacity of 75 mAh g-1 at 0.1 C and an energy density of 52 Wh kg-1. In addition, both ex situ X-ray diffraction (XRD) analysis and first-principles calculations are employed to investigate the sodiation mechanism and structural evolution. The current research provides a feasible strategy for the symmetric sodium-ion batteries to achieve high energy density.

Secondary electrocaloric effect (ECE) arising from piezoelectricity combined with crystal thermal expansion was often overlooked in ECE studies of ferroelectric ceramics. This work mainly evaluated the primary ECE (ΔTECE) and secondary ECE (∆T2) of eco-friendly BaSnxTi1-xO3 (BSnT100x, 0

Defect engineering in thermoelectric materials leads to the formation of exotic transport properties. Specifically, reduction in lattice thermal conductivity (кL) can be realized through scattering of low and high-frequency phonons by interfacial and point defects respectively. Herein we explore such phenomena by inducing dense dislocations through doping of rare earth (RE) impurities in β-(Zn1−xREx)4Sb3 [x = 0.3–0.5 at.%] as phonon scattering source of all frequencies. Lattice anharmonicity created results in an ultra-low кL of ~0.15 W/mK for β-(Zn0.997 Yb0.003)4Sb3. Vibrational properties and phonon scattering altered by the lattice anharmonicity are studied in detail through terahertz and infrared spectroscopies.

With the development of high-temperature thermoelectric materials, especially the superionic copper selenide (Cu2−xSe), thermal stability and cycling thermoelectric performance have become a great concern recently. Here we demonstrate that the excellent repeatability of the thermal cycling data of a simple Cu–Se binary system can be obtained. The thermal stability was systematically studied via measuring the thermal-cycling thermoelectric performances of Cu1.97Se samples with different rates of Se evaporation by adopting a simple and controllable method, i.e., the conventional solid-state sintering method. The samples fabricated using the conventional sintering method exhibited an optimized figure of merit of 0.8 at 800 K with very good thermal repeatability and stability from 400 K to 800 K. The results indicated that the conventional sintering method can also be adopted to fabricate materials with satisfactory thermoelectric performance. It was found that the repeatability of thermal cycling data is directly related to the sintering temperature and indirectly associated with the evaporation of Se. The Cu1.97Se samples sintered at low temperatures experienced less evaporation of Se with good thermal repeatability, while they exhibited relatively low thermoelectric performance due to high carrier concentration. Although the samples sintered at high temperatures show a large variation in the thermal cycling performance, the repeatability could be improved by the further annealing process, which reveals that good thermal stability of thermoelectric materials can be obtained via post-treatment.

As the featured material of the superionic thermoelectric (TE) material family, copper-chalcogenide Cu2-xSe is attracting growing research interest for its excellent TE performance derived from the satisfactory power factor and the ultra-low thermal conductivity induced by the superionic effect. Various efforts have been made and proved to be effective to further enhance the TE performance for Cu2-xSe. However, this material is still far from the application stage, which is mainly due to concerns regarding control of the properties and the costly complex fabrication technology. Here we report a scalable pathway to achieve high-performance and tunable Cu2-xSe, utilizing conventional sintering technology and copper (Cu)-vacancy engineering with an effective mass model. The figure of merit zT is a competitive value of 1.0 at 800 K for the optimized binary Cu2-xSe, based on the precise modeling prediction and Cu-vacancy engineering. The changes in TE properties of Cu2-xSe under heating-cooling cycle tests are also revealed. Our work offers the referable method along with the decent parent material for further enhancement of TE performance, paving a possible route for the application and industrialization of Cu2-xSe TE materials. Keywords: Thermoelectric, Copper selenide, Copper-vacancy engineering, Effective mass model

It is challenging to achieve highly efficient thermoelectric materials due to the conflicts between thermopower (Seebeck coefficient) and electrical conductivity. These parameters are the core factors defining the thermoelectric property of any material. Here, we report the use of isovalent substitution as a tool to decouple the interdependency of the Seebeck coefficient and the electrical properties of cerium-doped bismuth selenide thermoelectric material. With this strategy, we can achieve a simultaneous increase in both the electrical conductivity and the Seebeck coefficient of the material by tuning the concentration of cerium doping, due to formation of neutral impurities and consequently the improvement of carrier mobility. Our theoretical calculation reveals a downward shift of the valence band with cerium concentration, which influences the thermoelectric enhancement of the synthesized materials. Finally, an order of magnitude enhancement of the figure of merit is obtained due to isovalent substitution, thus providing a new avenue for enhancing the thermoelectric performance of materials.

At present, the lithium-rich metal oxide Li 1+z MO 2 (M = Ni, Co, Mn, etc.) is one of the promising cathodes materials for high-energy lithium-ion batteries. In this work, we report the effect of different doping amounts of fluoride ions on the microstructural and electrochemical properties of Li[Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ]O 2 cathode material. At low doping levels, the fluoride ions substituted the oxygen ions. When the doped fluorine was more than the theoretical limit of x = 0.15, LiF-based material was attached on the surface of the material, offering better cycling performance of battery. With the doping effect, a discharge capacity of 230 mAh/g and a capacity retention rate of 98% were found respectively, which are better than the pristine electrode.

In order to explore efficient photocatalysts for N2 reduction reaction (NRR), 0D AgInS2 nanoparticles and 2D MXene (Ti3C2) nanosheets with different mass ratios are employed for building Z-scheme heterostructures. The resultant hybrids exhibit excellent interfacial charge transfer ability according to their optical and photo-electro properties. As a result, the obtained composite (30 wt% AgInS2) shows significant improvement on the photocatalytic performance for N2 fixation with a high ammonia yield rate of 38.8 μmol/(g∙h) under visible-light illumination (>400 nm). Meanwhile, the DFT calculations show that the activation of N2 in a dinuclear end-on bound structure could lead to high adsorption energy (Ead = −5.20 eV). Moreover, the mechanism of enhanced photocatalytic activity was proposed in terms of the quantum calculation between Ti3C2 and N2. This work provides new systems for enhanced NRR performance.

In the present work, the surface-modified graphene (SMG)/poly(vinylidene fluoride) (PVDF) fibrous membranes obtained from the electrospinning were treated by the hot pressing in the laminating mode to form the SMG/PVDF composites. The SMG was prepared by subjecting the graphene oxide to silane modification, NaBH4 reduction, and PVDF grafting in sequence. The successful surface modification of graphene was confirmed by TEM, XPS, Raman spectroscopy, FTIR, WAXD, and TGA. Furthermore, the structures of SMG/PVDF composites fabricated by the electrospinning-hot pressing method were studied by SEM, FTIR, and WAXD, which exhibited the well dispersion of SMG in the PVDF matrix. Finally, the investigation showed that the dielectric permittivities of SMG/PVDF composites increased with the SMG content, which were significantly higher than that of pristine PVDF. The dielectric permittivity of SMG (16 wt%)/PVDF composite (83.8) at 1000 Hz was found to be ten-fold that of the corresponding value of pristine PVDF (8.3) with a relatively low dielectric loss factor (0.34) and a relatively high thermal conductivity (0.679 W/mK).

In this work, a novel porous amorphous Fe2O3/nitrogen-doped carbon composite as a promising anode material for sodium-ion batteries has been fabricated by in situ growing amorphous Fe2O3 on 3D interconnected nitrogen-doped carbon nanofibers. The as-prepared composite exhibits superior sodium storage properties. It delivers a high reversible capacity of 408 mA h g−1 after 350 cycles at a current density of 100 mA g−1 and a good rate capability of 183 mA h g−1 at 3 A g−1. The excellent electrochemical performance is owing to the synergistic effects of the amorphous structure of Fe2O3 and the 3D interconnected nitrogen-doped carbon network with high nitrogen doping content (10 atom%), which do not only relieve the internal stress of the electrode and accommodate more electrochemical active sites for Na+ storage, but also buffer the volume changes of amorphous Fe2O3 as well as facilitate the electronic and ionic transportation during cycling.

The electrochemical carbon dioxide (CO2) reduction (ECR) represents one of the most promising technologies for CO2 conversion into value-added feedstock from carbon monoxide (CO) to a variety of hydrocarbons. As the raw material for Fischer–Tropsch synthesis, CO is one of the most desirable ECR products and has recently received extensive research attention. Although noble metal materials, such as Au and Ag, show high selectivity towards conversion of CO2 to CO, their relative scarcity and high cost seriously limit their practical commercial application. Nanostructured carbon-based non-precious metal electrocatalysts (Nano-CNMs) are of tremendous interest in the field of ECR catalysis due to their tunable structures and electronic properties. Herein, we present an overview of recent progress in the application of Nano-CNMs, mainly including heteroatom-doped carbon, transition metal–heteroatom co-doped carbon, and carbon-based hybrid materials, with emphasis on electrocatalytic conversion of CO2 to CO. We particularly focus on discussing the structure/composition–performance relationships with regard to the electronic structure, surface properties, doping content, and associated electrocatalytic performance of various Nano-CNMs. We outline the future research directions in the development of high-selectivity ECR electrocatalysts for CO production and the stringent challenges in fundamental research and industrial application.

Developing a thermoelectric generator(TEG) with shape conformable geometry for sustaining low-thermal\ud impedance and large temperature gradient (ΔT) is fundamental for wearable and multi-scale energy harvesting applications. Here we demonstrate a flexible architectural design, with efficient thin film thermoelectric\ud generator as a solution for this problem. This approach not only decreases the thermal impedance but also\ud multiplies the temperature gradient, thereby increasing the power conversion efficiency (PCE) as comparable to\ud bulk TEG. Intact thin films of Tin telluride (p-type) and Lead Telluride (n-type) are deposited on flexible substrate\ud through physical vapor deposition and a thermoelectric module possessing a maximum output power density of\ud 8.4 mW/cm2 is fabricated. We have demonstrated the performance of p-SnTe/n-PbTe based TEG as a flexible\ud wearable power source for electronic gadgets, as a thermal touch sensor for real-time switching and temperature\ud monitoring for exoskeleton applications.

The direct use of graphene for potential thermoelectric material requires the opening of its bandgap without loss of its high electric conductivity. We herein demonstrate a synchronous reduction and assembly strategy to fabricate large-area reduced graphene oxide films with high electric conductivity and optimized low thermal conductivity assembly. The reduced graphene oxide films have a high electric conductivity and low thermal conductivity, which results from high longitudinal carrier mobility of the lattice domains as well as the enhanced scattering of phonons in the defects and their boundary that substantially reduces the mean phonon free path and the thermal conductivity. Flexible thermoelectric generators were prepared by assembling reduced graphene oxide film on 3D printed polydimethylsiloxane grids, demonstrating a remarkable output voltage of 57.33 mV/g at a temperature difference of 50 K. A wristband-type flexible thermoelectric generator with 7 repeating units generated a maximum power density of 4.19 µW/g at ambient temperature of 15 °C. The 3D printed generator is promising in providing power autonomy to wearable microwatt electronic devices. In addition, we believe that this work can be easily scaled up and can offer the pathway to produce large-scale manufacturing of graphene based materials for future microelectronics and large-scaled flexible and wearable energy harvesting systems.

In this work, the crystal structure, thermal conductivity, as well as dielectric and electrical properties of poly(vinylidene fluoride-co-chlorotrifluoroethylene) [P(VDF-CTFE)] filled with two different carbon nanofillers including exfoliated graphite nanoplates (xGNPs) and multi-walled carbon nanotubes (MWCNTs) have been compared. The xGNPs and the MWCNTs were well dispersed in the P(VDF-CTFE) matrix using a simple solution-blending process. The xGNPs have the ability to induce the large amount of useful polar β and γ crystal phases for P(VDF-CTFE) via the relatively strong interfacial interaction between their functional groups and the dipoles of P(VDF-CTFE), while the MWCNTs only produce the relatively low amount of β crystal phases for P(VDF-CTFE) due to their weak π-dipole interactions with P(VDF-CTFE). It was found that both the electrical conductivity and dielectric properties of xGNPs/P(VDF-CTFE) composite were better than those of MWCNTs/P(VDF-CTFE) composite. The thermal conductivities of xGNPs/P(VDF-CTFE) composites were much higher when compared with those of MWCNTs/P(VDF-CTFE) composites at the same filler content, which is probably owing to the better compatibility between xGNPs and P(VDF-CTFE). For example, the thermal conductivities of xGNPs (5 wt%)/P(VDF-CTFE) composite and MWCNTs (5 wt%)/P(VDF-CTFE) composite were 0.83 W/mK and 0.43 W/mK, respectively.

Biomass-based carbon has attracted considerable attention as a host material of active sulfur in lithium–sulfur batteries, while chemical activators of H3PO4, KOH, or ZnCl2 are essential to constru...

To improve the dielectric performance of high-dielectric-constant conductive filler/polymer composites, polyaniline was deposited on exfoliated graphite nanoplates (xGNPs) by in-situ polymerization method to form polyaniline (PANI) coated xGNPs (xGNPs@PANI) as the conductive filler for the oxidized styrene-butadienestyrene copolymer (SBS-FH) containing both hydroxyl and formyloxy groups. The results of TEM, SEM, FTIR, TGA, Raman spectrum, XPS, and WAXD showed that PANI had been coated onto the surface of xGNPs successfully. The xGNPs@PANI/SBS-FH composites were prepared by a simple solution-blending method and the homogenous distribution of xGNPs@PANI in the SBS-FH matrix was confirmed by SEM. The presence of xGNPs@PANI was found to significantly improve the dielectric properties of resultant composite compared to the unmodified xGNPs. For example, the xGNPs@PANI/SBS-FH composite near percolation threshold filled with 9.38 vol.% xGNPs@PANI showed a dielectric constant of 56.8 and a dielectric loss factor of 0.51 at 1000 Hz, while the corresponding values of xGNPs (1.19 vol.%)/SBS composite were 15.96 and 2.91 at 1000 Hz, respectively. In addition, the incorporation of xGNPs@PANI into SBS-FH could effectively enhance the thermal conductivity of resultant xGNPs@PANI/SBS-FH composite.

Perovskite ferroelectrics possess the fascinating piezoelectric properties near a morphotropic phase boundary, attributing to a low energy barrier that the results in structural instability and easy polarization rotation. In this work, a new lead-free system of (1-x)BaTiO3-xCaHfO3 was designed, and characterized by a coexistence of ferroelectric rhombohedral-orthorhombic-tetragonal (R-O-T) phases. With the increase amount of CaHfO3 (x), a stable coexistence region of three ferroelectric phases (R-O-T) exists at 0.06 ≤ x ≤ 0.08. Both large piezoelectric coefficient (d33∼400 pC/N), inverse piezoelectric coefficient (d33*∼547 pm/V) and planar electromechanical coupling factor (kp∼58.2%) can be achieved for the composition with x = 0.08 near the coexistence of three ferroelectric phases. Our results show that the materials with the composition located at a region where the three ferroelectric R-O-T phases coexist would have the lowest energy barrier and thus greatly promote the polarization rotation, resulting in a strong piezoelectric response.

Lithium-sulfur (Li-S) battery has attracted remarkable attention owing to its high theoretical energy density. However, its commercialization is still hampered by the rapid capacity degradation which mainly originates from the polysulfides shuttle between the anode and cathode. In this paper, a functional multiwall carbon nanotube/sulfonated polyaniline (MWCNT/SPANI) modified separator is designed to enhance the electrochemical performance of the Li-S batteries with high sulfur loading. The MWCNT/SPANI-coated separator is highly permselective to Li + but rejects the transportation of polysulfide anions. Besides, the MWCNT/SPANI coating can also work as an upper current collector and provides channels for electron and ion transport to enhance the sulfur utilization and ensure the reactivation of trapped active materials. With the ion selective MWCNT/SPANI-coated separator, the electrochemical performance of the Li-S batteries based on cathodes with high sulfur loading (5 mg cm −2 ) and high sulfur content (72 wt%) has been significantly improved. It delivers a reversible capacity of 913 mA h g −1 at the current density of 100 mA g −1 after 100 cycles, much higher than that of the cells with pristine Celgard separator. Hence, the ion selective MWCNT/SPANI modified separator is promising for developing high-performance Li-S batteries employing cathodes with high sulfur loading and high sulfur content.

Aqueous rechargeable batteries have promising application in large-scale energy storage owing to their cost-effective, eco-friendly, high safety and good electrochemical performance. An aqueous rechargeable hybrid sodium/zinc battery with Zn anode, Na3MnTi(PO4)3 cathode and 0.5 mol L-1 CH3COONa and Zn(CH3COO)2 mixed electrolyte has been designed for the first time. The battery delivered a reversible and stable capacity of 95.0 mAh g−1 at 1.5 C for 50 cycles with a high and flat working voltage of 1.75 V vs. Zn2+/Zn. Impressively, the battery showed the excellent cycling performance and superior rate capability, which can be cycled at 10.0 C for 2000 cycles with a capacity retention of 93.6% and a reversible capacity of 55.6 mAh g−1 at 30.0 C. Meanwhile, the co-intercalation mechanism of hybrid Na+ and Zn2+ in the cathode is elucidated by cyclic voltammogram, ex-situ XRD, ex-situ XPS and Rietveld refinement analysis. This work gets insight into the charge/discharge processes of hybrid ions for NASICON-structured Na3MnTi(PO4)3, providing a feasible way to design cost-effective, high safety and long-term aqueous rechargeable batteries.

Colossal permittivity (CP) materials have shown great technological potential for advanced microelectronics and high-energy-density storage applications. However, developing high performance CP materials has been met with limited success because of low breakdown electric field and large dielectric loss. Here, composite films have been developed based on surface hydroxylated ceramic fillers, (Er + Nb) co-doped TiO2 embedded in poly(vinylidene fluoride trifluoroethylene) matrix by a simple technique. We report on simultaneously observing a large dielectric constant up to 300, exceptional low dielectric loss down to 0.04 in the low frequency range, and an acceptable breakdown electric field of 813 kV cm−1 in the composites. Consequently, this work may pave the way for developing highly stable and superior dielectrics through a simple and scalable route to meet requirements of further miniaturization in microelectronic and energy-storage devices.

High-voltage LiNi0.5Mn1.5O4 is a promising cathode candidate for lithium-ion batteries (LIBs) due to its considerable energy density and power density, but the material generally undergoes serious capacity fading caused by side reactions between the active material and organic electrolyte. In this work, Li+-conductive Li2SnO3 was coated on the surface of LiNi0.5Mn1.5O4 to protect the cathode against the attack of HF, mitigate the dissolution of Mn ions during cycling and improve the Li+ diffusion coefficient of the materials. Remarkable improvement in cycling stability and rate performance has been achieved in Li2SnO3-coated LiNi0.5Mn1.5O4. The 1.0 wt% Li2SnO3-coated LiNi0.5Mn1.5O4 cathode exhibits excellent cycling stability with a capacity retention of 88.2% after 150 cycles at 0.1 C and rate capability at high discharge rates of 5 C and 10 C, presenting discharge capacities of 119.5 and 112.2 mAh g-1, respectively. In particular, a significant improvement in cycling stability at 55 °C is obtained after the coating of 1.0 wt% Li2SnO3, giving a capacity retention of 86.8% after 150 cycles at 1 C and 55 °C. The present study provides a significant insight into the effective protection of Li-conductive coating materials for a high-voltage LiNi0.5Mn1.5O4 cathode material.

Tin sulfide (SnS2) is an excellent photocatalyst, which is widely used in reduction of heavy metal pollutants. However, its application is hindered by the rapid recombination of photogenerated carriers. In this study, a heterostructure composite composed of PANI, SnS2 and carbon sphere (PANI@SnS2@Cs) was prepared by a hydrothermal approach combined with in-situ oxidative polymerization to release the fast recombination of photogenerated carriers and improve the photoreduction performance. Compared with bare SnS2 and SnS2@Cs, PANI@SnS2@Cs not only provides more efficient photoreduction performance, but also possesses stronger adsorption capability. In neutral solution, 60 mg PANI@SnS2@Cs is capable of reducing 60 mL contaminated water with a concentration of 100 mg/L Cr(VI) within 30 min of solar light. Characterizations including transmission electron microscope and UV–Vis-NIR diffusive reflectance spectra were applied to provide evidences to confirm the heterostructure and the excellent optical performance of PANI@SnS2@Cs. Besides, the mechanism behind PANI@SnS2@Cs was investigated that the photogenerated e- in the lowest unoccupied molecular orbital (LUMO) of PANI can be transferred into the conduction band of SnS2 while h+ in valence band of SnS2 can be transferred into the highest occupied molecular orbital (HOMO) of PANI.

In this work, graphene was modified by the grafting of poly(vinylidene fluoride) (PVDF) using Friedel-Crafts reaction to form PVDF-grafted graphene (PGG) filler, which was confirmed by transmission...

SnSe single crystals have been demonstrated to possess excellent thermoelectric properties. In this work, we demonstrate a grain size control method in growing nanocrystalline SnSe thin films through a glancing angle pulsed-laser deposition approach. Structural characterization reveals that the SnSe film deposited at a normal angle has a preferred orientation along a axis, while by contrast, the SnSe film deposited at an 80° glancing angle develops a nanopillar structure with the growth direction towards the incident atomic flux. The glancing angle deposition greatly reduces the grain size of the thin film due to a shadowing effect to the adatoms, resulting in significantly increased power factor for more than 100%. The maximum Seebeck coefficient and power factor are 498.5 μ V / K and 18.5 μ W c m − 1 K − 2 , respectively. The enhancement of thermoelectric property can be attributed to the potential barrier scattering at grain boundaries owing to the reduced grain size and increased grain boundaries in the film. Given this enhanced power factor, and considering the fact that the nanopillar structure should have much lower thermal conductivity than a plain film, the zT value of such made SnSe film could be significantly larger than the corresponding single crystal film, making it a good candidate for thin film-based thermoelectric device.

In this study, novel ZnS@In2S3 core@shell hollow nanospheres were fabricated by a facile refluxing method for the first time, and the formation mechanism of hollow structure with interior architecture was discussed based on ion-exchange Ostwald ripening. As the photocatalytic material for degradation of gaseous o-Dichlorobenzene (o-DCB), the as-synthesized core@shell hollow nanospheres were found to show significantly enhanced catalytic performance for effective separation of photo-generated charges. Moreover, the mechanisms of enhanced activity were elucidated by band alignment and unique configuration. Such photocatalyst would meet the demands for the control of persistent organic pollutant (POPs) in the atmospheric environment.

A fairy simple and environmental hydrothermal method is successfully found to synthesize the anode materials integrated by NiFe2O4 (NFO) and ultrathin flake graphite (UFG)，which are denoted as NFO/UFG composites. Then a couple of experiments have been implemented in order to search for the most profitable proportion of UFG in the composite. And it's finally attested that NFO/UFG-2 composite exhibits the most beneficial morphology structure which is characterized as three-dimensional floral NFO microspheres assembled by many porous nanosheets anchored on the pedestal of UFG by SEM test and further TEM measurement. Not only that, the NFO/UFG-2 composite is also investigated to acquire the best electrochemical performances. It shows a most stable long-term cycling performance with a high initial coulombic efficiency of 83.4% and even obtains a high specific capacity of 963.4 mAh g-1 after 300 cycles at a current density of 200 mA g-1 and remarkable reversibility not only at low current densities but also at high current densities. Satisfactorily the good synergy of porous NFO and UFG significantly enhances the electronic conductivity and relieves the huge bulk expansion of traditional transition metal oxide. This unique electrode material is demonstrated to be a promising candidate for the new-generation LIBs.

In this work, Bi 0.85 Sm 0.15 Fe 0.97 Sc 0.03 O 3 ceramics were prepared by rapid hot pressing. Their crystal structures, dielectric and multiferroic properties were studied with an emphasis on microscopic ferroelectric and ferromagnetic domains characterizations. X-ray diffraction data revealed a diphase structure consisting of rhombohedra R 3 C and orthorhombic Pbnm . The ferroelectric polarization and magnetization measurements showed the ceramics， possessing simultaneously a giant remanent polarization of 42.36 μC/cm 2 and a high remanent magnetization of 0.134 emu/g at room temperature. Moreover, the regularly striped ferroelectric and ferromagnetic domain structures have been identified and analyzed by combining transmission electron microscopy and piezoresponse/magnetic force microscopy.

A variety of nano/microstructured YF3:0.125Eu3+, 0.5%Bi3+ samples with specific morphologies was successfully synthesized by a hydrothermal method using various fluoride sources as microstructure-directing agents, and the grain morphology and fluorescence were effectively tailored. The YF3:0.125Eu3+, 0.5%Bi3+ samples using NH4F, NH4HF2, LiF, NaF, KF, MgF2, CaF2, and BaF2 as fluoride source are abbreviated as S1–S8, respectively. Except for the sample S8, all the diffraction peaks of the other materials (S1–S7) can be indexed to pure YF3 with orthorhombic symmetry. Granule-like nanoparticles, truncated octahedron, octahedron, and bipyramid morphologies were observed in S1–S2, S3–S4, S5–S7, and S8 samples, respectively. The grain size of the materials is positively correlated with the cationic radius in fluoride sources, which gives the values of 64 nm to 4.2 μm. The schematic diagram showing grain formation process has been proposed on the basis of fluoride source-induced morphological evolution. The morph...

Chemically integrated hybrid quantum dots ZnCo2O4/reduced graphene oxide (QDs ZCO/rGO) sheets nanocomposites are synthesized through polyol processes. rGO sheets grow and interweave to form basic skeletons. Ultrafine ZCO particles with a size of around 3.66 nm grow and embed on both sides of the rGO sheets, and the rGO sheets restrain the reunion of ZCO nanoparticles. The existence of rGO sheets and ZCO nanoparticles can engender the mutual synergistic effects so that hybrid QDs ZCO/rGO electrodes exhibit the excellent electrochemical properties. Owing to this special nanoparticles-on-sheets structure, the hybrid QDs ZCO/rGO electrodes exhibit an excellent initial discharge capacity for rechargeable lithium-ion batteries (1325.9 mAh g−1 at the current density of 200 mA g−1), high rate stability (532.3/566.1 mAh g−1 at 4000 mA g−1) and outstanding electrochemical cyclic stability (657.6/668.2 mAh g−1 at 2000 mA g−1 after 2000 cycles with a capacity retention of 68.6%). For full-cells, high initial reversible discharging capacity (646 mAh g−1 at 200 mA g−1) and good cyclic stability (514 mAh g−1 at 200 mA g−1 after 100 cycles) are obtained. The superior performance of the as-prepared electrodes is ascribed to the advantage of nano-sized particles. With the successful synthesis of hybrid QDs ZCO/rGO nanocomposites, the facile synthetic route and unique growth of nanostructuring method can be extended to high electrochemical performance electrodes for commercial lithium-ion batteries.

Hierarchical CoMn2O4 microspheres assembled by nanoparticles have been successfully synthesized by a facile hydrothermal method and a subsequent annealing treatment. XRD detection indicate the crystal structure. SEM and TEM results reveal the 3-dimensional porous and micro-/nanostructural microsphere assembled by nanoparticles with a size of 20-100 nm. The CoMn2O4 electrode show initial specific discharge capacity of approximately 1546 mAh/g at the current rates 100 mA/g with a coulombic efficiency of 66.7% and remarkable specific capacities (1029-485 mAh/g) at various current rates (100-2800 mA/g).

In this work, Li 2 SiO 3 , a layer-structured fast Li + -ion conductor with three-dimensional Li + paths, has been firstly introduced into LiNi 0.5 Mn 1.5 O 4 to form novel cathode composites of (1-x)LiNi 0.5 Mn 1.5 O 4 ·xLi 2 SiO 3 via a citric acid-assisted sol-gel method. The effects of Li 2 SiO 3 on the phase structure, morphology and electrochemical performance of the materials were investigated. As x increases, the structure and electrochemical properties of the materials are tailored. The cathode material with x = 0.10 delivers ultrahigh initial discharge capacity ∼150.3 mAh g −1 , which is 24.4% larger than that of the pristine LiNi 0.5 Mn 1.5 O 4 (120.8 mAh g −1 ). The Li 2 SiO 3 -composited LiNi 0.5 Mn 1.5 O 4 materials present an enhanced cycling stability, better rate performance and lower charge transfer resistance. These excellent electrochemical properties indicate that the compositing of fast Li + -ion conductor Li 2 SiO 3 is an effective method to enhance the electrochemical performance of LiNi 0.5 Mn 1.5 O 4 -based cathode materials.

Polystyrene-block-polybutadiene-block-polystyrene triblock copolymer (SBS) has the potential to be used as a dielectric elastomer for actuator, sensor, energy harvesting, and so on, but its low dielectric constant and thermal conductivity seriously limit this application. In this study, novel exfoliated graphite nanoplates (xGNPs)/SBS composites were prepared by a solution-blending method using N,N-dimethylformamide and tetrahydrofuran as co-solvents. Wide-angle X-ray diffraction measurement confirms that xGNPs have been incorporated into SBS. Furthermore, the result of scanning electron microscopy shows that xGNPs disperse well in the SBS matrix. The effects of xGNPs on the dielectric constant and thermal conductivity of the resultant xGNPs/SBS composites were investigated. The dielectric constant at 1,000 Hz significantly increased from 2.72 for pure SBS to 15.96 and 40.94 for xGNPs/SBS composite containing 1.19 and 1.27 vol.% of xGNPs, respectively. Moreover, the thermal conductivity of the xGNPs/SBS composite containing 1.27 vol.% of xGNPs has been improved from 0.18 to 0.41 W/m·K in comparison with that of pure SBS.

Lead-free piezoelectric and multiferroic ceramics of BiFeO3–BaTiO3–NdCoO3 were synthesized by a conventional solid-state reaction method and the structural, piezoelectric, multiferroic and magnetoelectric properties of the materials were investigated. All the ceramics can be well sintered at a low sintering temperature of 980 °C for 2 h. The introduction of NdCoO3 into BiFeO3–BaTiO3 induces a dramatic enhancement in the piezoelectricity, multiferroicity and magnetoelectric effect of the materials. After the addition of 1.0–3.0 mol% NdCoO3, the ceramics possess a morphotropic phase boundary of rhombohedral and orthorhombic phases and exhibit high Curie temperature (~486–605 °C), strong piezoelectricity, good ferroelectricity and excellent temperature stability of piezoelectricity. The greatly enhanced magnetism with M r = 0.4229 emu/g and M s = 2.7186 emu/g is obtained in the ceramic with 8.0 mol% NdCoO3, almost six times larger than that of an undoped ceramic. The ceramic with 2.0 mol% NdCoO3 shows a strong magnetoelectric effect (α 33 = 750 mV cm−1 Oe−1). The practical application potential of the present materials has also been preliminarily demonstrated by mimicking current monitoring. Our results suggest that the present ceramics may have potential applications in advanced lead-free piezoelectric and/or multiferroic devices.

Based on the empirical electron theory of solids and molecules, the valence-electron structures (VES) and the surface energy of the Ni‒Cu electrode of Pb(Ti, Zr)O3 piezoelectric ceramics were calcu...

Organosilicate (OS)/poly(vinylidene fluoride) (PVDF) composites containing 2 and 4 wt% OS were prepared by the melt-blending method. It was confirmed by scanning electron microscopy that OS was homogeneously distributed in the PVDF matrix. The results of differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and wide angle X-ray diffraction indicated that the incorporation of OS along with stretching treatment could effectively transform PVDF crystallization from the stable α phase to the most useful electroactive β phase. The interfacial interaction between PVDF and OS was analyzed by X-ray photoelectron spectroscopy and zeta potential. The dielectric properties, AC conductivities, mechanical properties, Rockwell hardness, and thermal conductivity of resultant OS/PVDF composites have been measured. More importantly, the piezoelectric coefficient d 33 and pyroelectric coefficient p of stretched OS/PVDF composites were enhanced significantly in comparison with the pure PVDF, making them promising materials for self-powered electronic systems, thermal detectors, sensors, and actuators.

Porous ZnFe2O4 nanorods have been successfully prepared by a simple spray-drying process followed by sintering. The structure and morphology of the samples were characterized by X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. The porous structured ZnFe2O4 materials are successfully used as potential anode material for lithium-ion batteries. Electrochemical results show that the anodes exhibit good cycling performance and rate capability. The anode exhibits initial discharge capacity of approximately 1459 mAh g−1 with an initial coulombic efficiency of 77.8% at a constant density of 100 mA g−1. The discharge capacity of the ZnFe2O4 retained 1458 mA h g−1 after 120 cycles at the current rate of 100 mA g−1 and 456 mA h g−1 could be obtained at the current density of 5000 mA g−1 after 200 cycles. The discharge capacities can still be as high as 778 mAh g−1 at a high rate of 3000 mA g−1. Such remarkable electrochemical properties could be ascribed to the unique porous morphology with large surface area and porosity that were beneficial to facilitate the diffusion of Li ions and electrolyte into the electrodes, meanwhile prevent volume expansion/contraction during lithiation/dislithiation processes.

In recent years, multi-component integrated composite cathodes for lithium ion batteries have attracted considerable attention. In this work, novel layered-spinel integrated cathode materials of (1− x )LiNi 0.5 Mn 0.5 O 2 - x LiMn 1.9 Al 0.1 O 4 were synthesized by a sol-gel method, and their phase structures, morphologies and electrochemical performance were investigated. The crystal structure of the (1− x )LiNi 0.5 Mn 0.5 O 2 - x LiMn 1.9 Al 0.1 O 4 is changed from layered to spinel structure with increasing x . All the samples exhibit nanoscale grains with the minimum grain size of ~130 nm when x = 0.5. The composite electrode with x = 0.5 exhibits the optimal discharge capacity, presenting a large initial discharge capacity of 236 mAh g −1 at the current density of 20 mA g −1 . Good rate capability is also obtained at the composite electrode with x = 0.5 where the electrode displays the relatively high discharge capacity of 64.9 mAh g −1 at the high rate of 5 C. The improved electrochemical performance is related to the introduction of spinel structure into layered structure and small grain size. The spinel structure can stabilize the layered structure, which leads to the improvement in the electrochemical performance of the composites; and the small grain size in the sample with x = 0.5 provides short lithium ion diffusion way and thus enhances the electrochemical performance.

The hierarchically structured cathode material Li1.165Mn0.501Ni0.167Co0.167O2 (LMNCO) is successfully synthesized via a facile ultrasonic-assisted co-precipitation method with a two-step heat treatment by adopting graphene and carbon nanotubes (CNTs) as functional framework and modified material. The structure and electrochemical performance degeneration mechanism were systematically investigated in this work. The obtained LMNCO microspheres possess a hierarchical nano-micropore structure assembled with nanosized building blocks, which originates from the oxidative decomposition of the transition metal carbonate precursor and carbonaceous materials accompanied with the release of CO2 (but still remain carbon residue). What’s more, the positive electrode exhibits enhanced specific capacities (276.6 mAh g−1 at 0.1 C), superior initial coulombic efficiency (80.3 %), remarkable rate capability (60.5 mAh g−1 at 10 C) and high Li+ diffusion coefficient (~10−9 cm2 s−1). The excellent performances can be attributed to the pore structure, small particle sizes, large specific surface area and enhanced electrical conductivity. (1 C = 250 mA g−1).

High-quality fine-grained ferroelectric glass-ceramic composites were successfully fabricated by using a modified hybrid processing. The properties of interfaces were investigated by using impedance spectroscopy (IS). In our measured impedance spectra, a polarization with an ideal Debye behavior was observed at intermediate frequency ranging between 1 kHz and 100 kHz. This polarization was attributed to the space charge accumulation at the grain-boundary interfaces, due to the presence of large dielectric constant difference between the fillers and the host. Basing on the IS results, a brick-layer microstructural model was proposed for the ferroelectric glass-ceramic composites. Our studies indicated that the new modified hybrid processing can be used to design composites with desired interfaces that have a homogeneous dielectric constant, so as to achieve high breakdown strength, thus leading to high electrical energy density storage devices.

Si@carbon composites have been successfully prepared via spray drying and subsequent calcination using PSA microspheres, nano-silicon and natural graphite as raw materials. Nano-silicon with a 20–100 nm particle size is prepared by radio-frequency electromagnetic induction. Such small nano-silicon particles can effectively accommodate the volume expansion of the Si@carbon anode. Additionally, the unique core–shell structure of Si@carbon composites can effectively alleviate the agglomeration of nano-silicon particles. Electrochemical tests show that the Si/carbon electrode delivers a high initial discharge capacity of approximately 1404.27 mAh g−1 with an initial coulombic efficiency of 82.4 %. The discharge specific capacity remains as high as 73.6 % after 100 charging-discharging cycles, demonstrating the electrode material’s good cycle stability. In addition, the corresponding specific capacity of the Si@carbon composites electrode remains at around 1150 mAh g−1 at a current density of 1 A g−1. And when the current density is 0.1 A g−1, its specific capacity can still remain at around 920 mAh g−1, indicating excellent capacity reversibility. Therefore, Si@carbon composites are superior anode materials for high-performance Li-ion batteries.

Zn2+ ion substituted nickel ferrite nanomaterials with the chemical formula Ni1−xZnxFe2O4 for x = 0, 0.3, 0.5, 0.7 and 1 have been synthesized by a facile green-chemical hydrothermal method as anode materials in lithium ion battery. The morphology and structure of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The physical and electrochemical properties were tested by electrochemical system. Furthermore, the energetic and electronic properties of the samples were investigated by density functional calculations. The results suggest that Zn substitution can affect the conduction performance of the zinc - nickel ferrite. Meanwhile, electrochemical results show that an enhancement in the capacity with increasing Zn concentration is observed especially for x = 0.3 which exhibit high discharge capacity of 1416 mAh g−1at the end of 100th cycle. Moreover, the theoretical research method with high yield synthesis strategy described in the present work holds promise for the general fabrication of other metallic elements substitution in complex transition metal oxides for high power LIBs.

Novel P(VDF-TrFE)/organosilicate composite membrane was fabricated by electrospinning. The electrospun composite membrane containing as little as 2 wt% of organosilicate demonstrated significant improvements in strength, modulus, and toughness by about 103%, 45%, and 97%, respectively, when compared with those of electrospun pure P(VDF-TrFE) membrane, while maintaining high porosity and good breathability and piezoelectricity. We believe that such an organosilicate-reinforced durable, porous, and piezoelectric P(VDF-TrFE) membrane has huge advantages in various applications such as flexible sensors, wearable electronics, filter membrane, tissue engineering, battery separator, and polymer electrolyte.

Polyhedral Ti-doped Co3O4 nanoparticles with a diameter of about 100–300 nm have been easily synthesized by a co-heat precipitated method. The structure and morphology of the materials were characterized by X-ray diffraction, field-emission scanning electron microscopy, and transmission electron microscopy. The electrochemical measurements were implemented on half coin cells. Galvanostatic charge, discharge performance, cyclic voltammetry and impedance measurement were utilized to investigate the electrochemical properties. The Ti-doped Co3O4 electrodes showed superior performance compared with the undoped Co3O4 electrodes, including the enhanced rate capability, and better capacity retention. At current densities of 500 mA g−1, the Ti-doped Co3O4 electrodes exhibited initial capacities of 1173.6 and 849.0 mAh g−1, and the capacities were maintained at 850.3 and 838.6 mAh g−1 after 120 cycles. These excellent electrochemical properties can be attributed to the nanoscale structure and Ti doping.

Nanocrystalline ZnFe2O4, Zn0.5Mn0.5Fe2O4, and Zn0.5Mn0.5Fe2O4@CNT composites have been successfully prepared by a facile and high-yield co-precipitation method. All the samples as the anode materials were characterized by X-ray diffraction, thermogravimetry, and electrochemical measurements. It has been found that the appropriate Mn doping and CNTs intertwining actively affect the formation of uniform morphology and improve the cycling stability and rate capability. The Zn0.5Mn0.5Fe2O4@CNT composites exhibit excellent electrochemical performance as the anode material, with enhanced reversible capacity (1374.8 mAh g−1 after 100 cycles at the current density of 100 mA g−1) and good rate capability (933.5 mAh g−1 at 500 mA g−1, 809.9 mAh g−1 at 1000 mA g−1, 634.2 mAh g−1 at 1500 mA g−1). We also present the crystal structure and Li-ion insertion mechanism for the above materials. Our work displays the Li storage matrix model of the ZMFO electrode which may offer a novel way for the investigation of the LIBs with excellent electrochemical performance and perfect structural stability .