Polymer nanocomposite dielectrics with high energy density and low loss are major enablers for a number of applications in modern electronic and electrical industry. Conventional fabrication of nanocomposites by solution routes involves equilibrium process, which is slow and results in structural imperfections, hence high leakage current and compromised reliability of the nanocomposites. We propose and demonstrate that a nonequilibrium process, which synergistically integrates electrospinning, hot-pressing and thermal quenching, is capable of yielding nanocomposites of very high quality. In the nonequilibrium nanocomposites of poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and BaTiO3 nanoparticles (BTO_nps), an ultrahigh Weibull modulus β of ∼30 is achieved, which is comparable to the quality of the bench-mark biaxially oriented polypropylene (BOPP) fabricated with melt-extrusion process by much more sophisticated and expensive industrial apparatus. Favorable phase composition and small crystalline size are also induced by the nonequilibrium process, which leads to concomitant enhancement of electric displacement and breakdown strength of the nanocomposite hence a high energy density of ∼21 J/cm3. Study on the polarization behavior and phase transformation at high electric field indicates that BTO_nps could facilitate the phase transformation from α- to β-polymorph at low electric field.Keywords: discharge efficiency; energy density; nanocomposite dielectrics; nonequilibrium process; phase tuning;

Easy processing and flexibility of polymer electrolytes make them very promising in developing all-solid-state lithium batteries. However, their low room-temperature conductivity and poor mechanical and thermal properties still hinder their applications. Here, we use Li6.75La3Zr1.75Ta0.25O12 (LLZTO) ceramics to trigger structural modification of poly(vinylidene fluoride) (PVDF) polymer electrolyte. By combining experiments and first-principle calculations, we find that La atom of LLZTO could complex with the N atom and C═O group of solvent molecules such as N,N-dimethylformamide along with electrons enriching at the N atom, which behaves like a Lewis base and induces the chemical dehydrofluorination of the PVDF skeleton. Partially modified PVDF chains activate the interactions between the PVDF matrix, lithium salt, and LLZTO fillers, hence leading to significantly improved performance of the flexible electrolyte membrane (e.g., a high ionic conductivity of about 5 × 10–4 S cm–1 at 25 °C, high mechanical strength, and good thermal stability). For further illustration, a solid-state lithium battery of LiCoO2|PVDF-based membrane|Li is fabricated and delivers satisfactory rate capability and cycling stability at room temperature. Our study indicates that the LLZTO modifying PVDF membrane is a promising electrolyte used for all-solid-state lithium batteries.

All-solid-state bulk-type lithium ion batteries (LIBs) are considered ultimate solutions to the safety issues associated with conventional LIBs using flammable liquid electrolyte. The development of bulk-type all-solid-state LIBs has been hindered by the low loading of active cathode materials, hence low specific surface capacity, and by the high interface resistance, which results in low rate and cyclic performance. In this contribution, we propose and demonstrate a synergistic all-composite approach to fabricating flexible all-solid-state LIBs. PEO-based composite cathode layers (filled with LiFePO4 particles) of ∼300 μm in thickness and composite electrolyte layers (filled with Al-LLZTO particles) are stacked layer-by-layer with lithium foils as negative layer and hot-pressed into a monolithic all-solid-state LIB. The flexible LIB delivers a high specific discharge capacity of 155 mAh/g, which corresponds to an ultrahigh surface capacity of 10.8 mAh/cm2, exhibits excellent capacity retention up to at least 10 cycles and could work properly under harsh operating conditions such as bending or being sectioned into pieces. The all-composite approach is favorable for improving both mesoscopic and microscopic interfaces inside the all-solid-state LIB and may provide a new toolbox for design and fabrication of all-solid-state LIBs.Keywords: bulk-type all-solid-state battery; composite; Li7La3Zr2O12,; lithium ion battery; PEO; solid-state electrolyte;

Using Al-contained Li6.75La3Zr1.75Ta0.25O12 (LLZTO) with high conductivity as electrolyte, we design and prepare a kind of monolithic-sintered LLZTO pellets with a novel porous-dense bilayer configuration, which integrates a dense LLZTO layer together with a porous LLZTO layer. Such bilayered configuration LLZTO is tested for all-solid-state lithium batteries. LiCoO2 as cathode active material is infiltrated into the porous electrolyte layer by sol-gel method, and lithium metal is used as anode and its interfacial contact with the dense electrolyte layer is optimized by tuning the surface roughness of the electrolyte. Moreover, a prototype all-solid-state lithium-oxygen battery is also assembled by introducing carbon and silver into the porous electrolyte layer as electronic conductive component in the air electrode and by contacting lithium metal with the dense electrolyte layer as anode. The cycle performances of both prototype batteries are tested to evaluate the function and limitations of the bilayer-structured oxide electrolyte.

•All-solid-state lithium batteries were assembled by a simple approach.•Composite cathodes possessed highly conducting network for ions and electrons.•A high surface capacity of 15 mAh/cm2 was obtained.•Excellent cyclic and rate performance were achieved.A simple way to assemble an all-solid-state lithium-ion battery with ultrahigh surface capacity and energy density was established. Polyethylene oxide-based solid-state electrolyte was prepared via solution method and nano-SiO2 was added into the electrolyte to increase the conductivity. Thick compact LiFePO4 pellet infused with dry polymer electrolyte was used as the composite cathode in the all-solid-state lithium battery. The compact composite cathode not only showed large ionic and electronic conductivity, but also provided sufficient “free space” to compensate the volumetric change of the active materials during cycling. The all-solid-state lithium battery (composite cathode/dry polymer electrolyte/Li) was cycled at a constant current density of 200 μA/cm2 at 60 °C. A maximum discharge specific capacity of 157 mAh/g was achieved and the surface capacity reached 15 mAh/cm2, which was of critical significance for all-solid-state lithium batteries. Good capacity retention was achieved after 10 cycles and great rate performance was obtained. Even at a current density of 1000 μA/cm2, the battery delivered a specific discharge capacity of 71 mAh/g, corresponding to a surface capacity of 6 mAh/cm2. The experimental data demonstrated that the composite cathode was a promising design in high-performance bulk-type all-solid-state lithium batteries.

•LiMn2O4 (LMO) and LiFePO4 (LFP) were found to react with Li6.75La3Zr1.75Ta0.25O12 (LLZTO) at about 500 °C by X-ray diffraction.•LiCoO2 (LCO) and LiNi0.33Co0.33Mn0.33O2 (NCM) were found to react with LLZTO at about 700 °C by Raman spectra.•LaCoO3 is one possible reaction product between LCO and LLZTO. LaCo1−xMnxO3 is one possible reaction product between NCM and LLZTO.High-temperature chemical compatibilities between garnet-like solid state electrolyte of Li6.75La3Zr1.75Ta0.25O12 (LLZTO) and the four major commercial lithium battery cathode materials, i.e., LiCoO2 (LCO), LiMn2O4 (LMO), LiNi0.33Co0.33Mn0.33O2 (NCM) and LiFePO4 (LFP) were investigated by X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), respectively. The same volume fraction of LLZTO and electrode powders were mixed and heated at 400–900 °C for 1 h. According to the results by XRD, LMO and LFP react with LLZTO at approximately 500 °C. The Raman data reveal that both LCO and NCM can react with LLZTO at approximately 700 °C, which lead to generate LaCoO3 and LaCo1−xMnxO3 with a rhombohedral symmetry, respectively.Figure optionsDownload full-size imageDownload as PowerPoint slide

•NASICON-type LATP powders were synthesized by a simple solution method.•The dense LATP electrolyte was obtained at a low sintering temperature.•The highest total conductivity at 25 °C is 1.21 × 10− 3 S cm− 1.A NASICON-type (Na ion super conductor) structured Li1.3Al0.3Ti1.7(PO4)3 (LATP) solid electrolyte with high lithium ion conductivity was synthesized using a simple solution method with 85% H3PO4 solution. In comparison with conventional solid-state reaction and sol-gel method, the pure LATP powders and dense LATP pellets were obtained at a relatively lower temperature. The LATP powders and the resultant pellets were characterized by X-ray diffraction, scanning electron microscopy (SEM) and AC impedance spectroscopy. The LATP pellet obtained at 800 °C for 12 h shows the highest total conductivity of 1.21 × 10− 3 S cm− 1 at room temperature and the lowest activation energy of 0.26 eV. These results imply that the LATP electrolytes obtained using this method can be considered as candidates for solid state electrolytes.

The oxides with perovskite structure possess abundant physical properties, such as magnetism, dielectricity, photoelectricity, ferroelectricity, etc. The oxygen ions in the perovskite unit cell constitute an octahedral distribution. The deformation or tilting of the special oxygen octahedra structure leads to new performances or properties change. Here, we give a review of the relationship between magnetic and electrical behaviors and oxygen octahedral tilting in several typical perovskite oxides. An understanding of how to tune these properties by controlling the tilting during the sample growth can more effectively guide the design of new structures for high performance and inspiring their potential applications.钙钛矿结构氧化物具有极其多样化的物理性能, 如磁性、介电性、光电性、铁电性等. 钙钛矿晶胞中的氧离子排布成八面 体结构. 氧八面体的变形或旋转会改变原有的物理特性, 甚至产生原本不存在的新性能. 本文综述了几种典型钙钛矿氧化物的氧八面 体旋转与磁性能和电性能的关系, 同时探讨了如何通过样品制备控制微观的八面体旋转, 从而更有效的设计具有高性能的新结构, 及 其潜在应用.

Voltage-modified magneto-optical Kerr effect (MOKE) is widely used to describe the converse magnetoelectric (ME) effect in the ferroelectric/ferromagnetic (FE/FM) heterostructures. However, the applied voltage can possibly give rise to electro-optical effect of the FE layer, which would also affect the Kerr signals in the MOKE system. Here, we used an AC voltage to modulate the magnetization in the Ni/Pb(Zr0.52Ti0.48)O3 (PZT) heterostructures with different pre-polarization states of the PZT layers to investigate the complexity of the Kerr signals. The results suggested that the voltage control of Kerr signal contained several origins; however, the strain-induced ME effect dominated in the ME effect in the heterostructures.

A uniaxial magnetic anisotropy Co film was grown on a single-crystal BaTiO3 (BTO) substrate. The strain yielded by the voltage-induced ferroelastic domain switching in the BTO substrate was recorded by atomic force microscope and modulated the magnetism of the Co film. The manipulation of the magnetism of the Co film is experimentally demonstrated by voltage dependence of magnetic hysteresis loops measured via magneto-optic Kerr effect.

An exceptional high ferroelectric remnant polarization (Pr) was observed in BaTiO3 ceramics owing to the formation of micron-sized grains possessing nano-scale mosaicity. Such a structural hierarchy was developed via a novel crystal-growth mechanism, namely ordered coalescence of nano-crystals achieved by synergetic atomic epitaxial growth and self-assembly of nano-crystals. The accommodating lattice defects in sub-grain boundaries due to the imperfect assembly of nano-crystals significantly contribute to the Pr enhancement by stimulating the dynamics of ferroelectric domain formation and switching. This finding defines a new approach to nanopowder sintering leading to enhanced properties sensitive to lattice defects.

A significant enhancement of thermoelectric performance in layered oxyselenides BiCuSeO was achieved. The electrical conductivity and Seebeck coefficient of BiCu1–xSeO (x = 0–0.1) indicate that the carriers were introduced in the (Cu2Se2)2– layer by Cu deficiencies. The maximum of electrical conductivity is 3 × 103 S m–1 for Bicu0.975Seo at 650 °C, much larger than 470 S m–1 for pristine BiCuSeO. Featured with very low thermal conductivity (∼0.5 W m–1 K–1) and a large Seebeck coefficient (+273 μV K–1), ZT at 650 °C is significantly increased from 0.50 for pristine BiCuSeO to 0.81 for BiCu0.975SeO by introducing Cu deficiencies, which makes it a promising candidate for medium temperature thermoelectric applications.

Li3xLa2/3−xTiO3 (LLTO) powder with different lithium contents (nominal 3x = 0.03–0.75) was synthesized via a simple sol–gel route and then calcination of gel-derived precursor at 900 °C which was much below the calcination temperature required for synthesizing the LLTO powder via solid state reaction route. The LLTO powder of sub-micron sized particles, derived from such sol–gel method, showed almost no aggregation. Starting from the sol–gel-derived powder, the LLTO ceramics with different lithium contents were prepared at different sintering temperatures of 1250 and 1350 °C. It demonstrated that our sol–gel route is quite simple and convenient compared to the previous sol–gel method and requires lower temperature for the LLTO. Our results also illustrated that lithium content significantly affects the structure and ionic conductivity of the LLTO ceramics. The dependence of the ionic conductivity on the lithium content, lattice structure, microstructure and sintering temperature was investigated systematically.

Bismuth ferrite (BiFeO3) uniform microcrystals with various morphologies (microspheres and micro/submirocubes) were successfully synthesized by a controlled hydrothermal method. The resulting microstructures were characterized using X-ray diffraction, scanning/transmission electron microscopies and Raman spectroscopy. Possible formation mechanism for BiFeO3 microcrystals was proposed. UV−vis spectra showed that the optical properties of the microsized BiFeO3 crystals were strongly related to their shape and size. We further demonstrated the useful photocatalytic activity of these regular-shaped structures as determined by degradation of Congo red under visible-light irradiation (λ > 400 nm). Additionally, magnetic responses were observed to be influenced by the morphology of as-synthesized BiFeO3 products, and the ferroelectric performance of BiFeO3 submicrocube was also studied by piezoelectric force microscopy (PFM). Being a multiferroic semiconductor with suitable narrow band gap (∼2.2 eV) and uniform morphologies, these BiFeO3 microcrystals might be useful for the design of devices combining magnetic, electronic, and optical functionalities.

An exceptional high ferroelectric remnant polarization (Pr) was observed in BaTiO3 ceramics owing to the formation of micron-sized grains possessing nano-scale mosaicity. Such a structural hierarchy was developed via a novel crystal-growth mechanism, namely ordered coalescence of nano-crystals achieved by synergetic atomic epitaxial growth and self-assembly of nano-crystals. The accommodating lattice defects in sub-grain boundaries due to the imperfect assembly of nano-crystals significantly contribute to the Pr enhancement by stimulating the dynamics of ferroelectric domain formation and switching. This finding defines a new approach to nanopowder sintering leading to enhanced properties sensitive to lattice defects.