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Abstract: Mesoporous carbons are prepared from a mixture of the soluble starch with needle-like nano-sized Mg(OH)2 particles. The samples structures are characterized by TEM, nitrogen adsorption at 77K and XRD. The electrochemical performance for electrochemical capacitors is evaluated in a 6M KOH aqueous solution. The resultant carbons show a disordered pore structure with interweaving straight nano-tunnels that resembled the shape of the template, and possess a high surface area more than 1000m2 g−1 and a large pore volume. The special one dimensional morphology of templates cause a graphitization effect on the carbon in partial region, different from catalytic graphitization mechanism of transition metal particles. Due to those characteristics, the samples exhibit good electrochemical performances used for electrochemical capacitors electrode, especially excellent power capability. The sample carbonized at 950°C for 6h retain a capacitance of 126Fg−1 even at a high current density of 40Ag−1. [Copyright &y& Elsevier]

It is still a considerable challenge for spinel Li 4 Ti 5 O 12 to achieve high tap density while retaining excellent power capability. Herein, a compact and mesopore-oriented holey-graphene framework (HGF) caging nano-Li 4 Ti 5 O 12 particles (Li 4 Ti 5 O 12 /HGF) is synthesized by capillary shrink effect. In the capillary drying process, nano-Li 4 Ti 5 O 12 particles prevent the absolute aggregation of graphene sheets, remaining mesopore-oriented porosity for rapid Li+ diffusion. After precisely adjusting the porous structure, Li 4 Ti 5 O 12 /HGF composite successfully achieves a balance between tap density and porosity. Furthermore, the in-plane nanopores of holey-graphene sheets provide channels for Li+ diffusion, obviously weakening the Li+ diffusion resistances of compact composite. The resultant Li 4 Ti 5 O 12 /HGF composite combines a high tap density of 1.1 g cm−3 and a moderate mesopore-oriented porosity with BET specific area of 152 m2 g−1, delivering volumetric-specific capacities of 161, 142, 120, 103 mA h cm−3 at 0.035, 1.75, 7 and 14 A g−1, respectively. Even as current density reaches 17.5 A g−1, the as-prepared Li 4 Ti 5 O 12 /HGF composite still displays a capacity of 98 mA h cm−3, showing excellent ultrahigh-rate performance. After 1000 cycles at 7A g−1, the capacity of dense Li 4 Ti 5 O 12 /HGF composite remains 84%, demonstrating high cycle stability. Image 1 • A balance between high tap density and mesopore-oriented structure. • Decreasing Li+ diffusion resistance due to holey-graphene sheets. • Excellent power capability and high cycle stability. [ABSTRACT FROM AUTHOR]

Recently, spinel high-entropy oxide (HEO) anode materials have garnered extensive attention for high-energy lithium-ion batteries due to their high specific capacity. Many studies have explored its energy storage mechanism, but few have paid attention to its characteristics in long cycle life. In this work, the whole life cycling performance of (FeCoNiCrMn)-HEO is presented and investigated for the first time. Distinct capacity trends are studied to divide the cycling life into three stages: activation, upgradation, and degradation. Ex situ morphological characterizations are conducted to reveal that the driving force of stage change is continuous particle fragmentation. As a result, refined particles promote conversion reaction reversibility and induce extra interfacial capacity, achieving 2831 mAh g−1 at 825 cycles. Density functional theory (DFT) calculations provide a deeper insight into the high entropy effect on the ultra-high extra interfacial capacity. However, continuous refinement brings about huge electrolyte interface-derived layers, which are also responsible for pre-decay and post-collapse. The view of the evolution of the lithium storage mechanism is explicitly presented and experimentally verified by high-energy ball milling and fluorinated vinyl carbonate (FEC). These above results can give practical solutions to design high specific capacity and long-life cycle stability HEO anode in the future. [Display omitted] • The whole life performance of (FeCoNiCrMn)-HEO was studied for the first time. • The driving force of capacity change is continuous particle fragmentation. • Particle refinement enhances reaction reversibility and interfacial capacity. • The high entropy effect led to the ultra-high extra capacity. [ABSTRACT FROM AUTHOR]

Abstract: This paper introduces a silicon three-dimensional (3D) micro supercapacitor, featured by using self-supporting nano porous composite materials and interdigital electrodes with high-aspect-ratio. A way to prepare self-supporting materials has been developed, and composites that contain an activated carbon as the active component have been studied and designed to meet the requirements for adequate specific capacitance, good conductivity and strong structure. By combining the designed composite with microfabrication techniques, a micro supercapacitor with high-aspect-ratio interdigital electrodes has been achieved. Electrochemical characterization results of the prototype with NaNO3 electrolyte demonstrate that the 3D supercapacitor exhibits an outstanding overall performance. A large capacitance of 90.7mFcm−2 and a fast power of 51.5mWcm−2 are calculated. Robust stability and high charge/discharge efficiency are also observed. Moreover, this study provides a scalable device built by compatible fabrication method, which is applicable to the integration of high-performance supercapacitors on chip. [Copyright &y& Elsevier]

Li 5 La 3 Nb 2 O 12 (LLNO) is a typical garnet-like solid electrolyte with solitary cubic structure. However, its ionic conductivity is relatively low due to the low relative density when prepared by cold isostatic pressing method, which usually involves high-pressure machines, poor productivity, tedious pressing operations, and low density. In this paper, self-consolidation method is developed to sinter dense LLNO electrolyte. Although not any pressing operations are employed in the entire process, the relative density of LLNO is promoted up to 95%, which is much higher than the reported values of 45–80%. SEM images reveal that the sample is built by huge particles in size of 80 μm indicating that there are few boundaries in the sample. Moreover, a rich content of Li-Al-O compounds is detected out in the boundary areas, which may act as sintering aids for the sample to consolidate automatically. According to the highest density, the bulk ionic conductivity of LLNO sample reaches up to 1.61 × 10 −4  S cm −1 at 30 °C, which is in the same order of magnitude as the value of cubic Li 7 La 3 Zr 2 O 12 electrolyte. This work verifies the self-consolidation mechanism for the sintering of ceramic electrolytes and could significantly facilitate the development of LLNO membrane technology. [ABSTRACT FROM AUTHOR]

We design a novel polymer-graphite composite grid as the negative current collector for lead-acid batteries. With this novel grid, the negative active material (NAM) can deliver a specific capacity of 170 mAh g −1 at a discharge rate of 0.1 C. After that, we conduct structural optimization and surface treatment on the grid to improve its performance. Through the structural optimization, additional lead pastes can be loaded and the cycle stability of the battery is enhanced. By using the optimized grid, the weight of the negative current collector can be remarkably reduced by more than 50%. To handle the serious hydrogen evolution on the graphite surface and the unfavorable adhesion between graphite and NAM, fine PbSO 4 particles are coated onto the surface of the graphite grids by chemical deposition. The cells employing the PbSO 4 -deposition grids exhibit excellent cycling stability as well as low polarization and then high Coulombic efficiency. We present here a possible mechanism that how PbSO 4 deposits effectively enhance the performance of negative plates based on the testing results. [ABSTRACT FROM AUTHOR]

Abstract: This paper demonstrates an asymmetric micro supercapacitor with superior overall performance that combines the advantages of both MnO2 positive electrode and carbon negative electrode for energy storage on a chip. Nano-structured MnO2 with rough surface is synthesized as active material for micro electrode. A self-supporting composite containing MnO2 and another containing nanoporous activated carbon (AC) are separated in an interdigital structure by using micro-electro-mechanical systems (MEMS) fabrication technologies. Measurements of the prototype show that the asymmetric micro supercapacitor has well-performed capacitive behavior, and its working voltage range is extended from 1 V to 1.5 V in aqueous electrolyte due to the MnO2–AC configuration. Calculations prove that it stores much higher energy densities than symmetric ones using either MnO2 or AC. Moreover, this work provides an attractive approach to achieve various asymmetric micro energy storage systems on chips. [Copyright &y& Elsevier]