Synthesis and performance of carbon-modified LiFePO_4 using an in situ PVA pyrolysis procedure

LiFePOa/carbon composite cathode material was prepared by granulating and subsequent pyrolysis processing in N2 atmosphere with polyvinyl alcohol （PVA） as the carbon source. The influences of carbon content on the microstructure and battery performance were investigated. Single LiFePO4 phase and amorphous carbon can be found in the products. A special micro-morphology of the optimum sample was observed. The discharge capacity of the cell with the optimum cathode was 135 mAh.g^-1, close to the charge capacity of 153 mAh.g^-1 at 17 mA.g^-1. The influence of ambient temperature on the cell capacity was investigated. The temperature dependence of its electrochemical characteristic was evaluated by using AC impedance spectroscopy. A new equivalent circuit based on the charge and mass transfer control process in an electrode was proposed to fit the obtained AC impedance spectra. The tendency of every element in the equivalent circuit was used to interpret the temperature dependence of the capacity of the optimum cathode.

Preparation,Characterization and Applications of Titanate/Titania Nanocrystals

The present paper focused on the preparation of hydrogen titanate nanotubes and nanowires and their conversion into titania by heat treatments.The structural,morphology and optical properties of as-prepared nanostructured titanate and titania were investigated by transmission electron microscopy (TEM),X-ray diffraction (XRD) and diffusive reflectance spectra.The slim diameter of these nanostructured titanate and titania,the versatile crystal structure and special optical and electronic properties may make them find versatile applications in chemical sensors for multiple purposes.

Highly Active Rutile TiO_2 for Photocatalysis

Nanocrystalline titania was prepared by the homogeneous-precipitation method at temperature lower than 120℃. The properties of powders were identified by XRD,TEM and diffuse reflection spectra.The results showed that rutile titania formed at 70℃without calcination in air.Nanometer rutile TiO_2 had good crystalline and small particle size.The formation mechanism of rutile was also discussed.The photocatalytic activity of the prepared particles was tested for the degradation of methyl orange.The photocatalytic activity of rutile TiO_2 was higher than those obtained from Degussa P-25 TiO_2.The reasons for high photocatalytic activity of futile were discussed.

Fabrication and Characterization of GCO Electrolyte Films

Gd-doped Ceria (GCO:Gd_(0.1)Ce_(0.9)O_(1.95)) sensing films have been fabricated successfully on glasses and porous Al_2O_3 ceramic substrates by RF magnetron sputtering.Sputtering conditions such as power and temperature have been investigated and the sample was characterized in detail by XRD,SEM and AC impedance spectroscopy.The results show that the films grow preferentially along the (111) compact plane with a pure fluorite structure and the crystal grain grows more sufficiently with increasing of the annealing temperature.In addition,a high oxygen ion conductivity of 2.24×10^(-2) S.cm^(-1) is achieved at 800℃.

Enhancement of–OH content on mechanical properties of antiperovskite solid electrolytes

All-solid-state batteries,renowned for their enhanced safety and high energy density,have garnered broad interest.Oxide solid electrolytes are highly anticipated for their balanced performance.However,their high Young’s modulus and inadaptability to volume change during cycling lead to poor contact and eventual battery failure.In this work,Young’s modulus of Li_(1+x)(OH)_(x)Cl samples is lowered to a level comparable to that of sulfide by regulating the–OH content.As the–OH content increases,Young’s modulus of Li_(1+x)(OH)_(x)Cl samples decreases significantly.This may be due to the local aggregation of–OH groups,forming cavities similar to LiOH structure,which reduces the bonding of the structure.On the premise of high Li-ion conductivity and electrochemical stability,the lowered Young’s modulus improves the contact between the solid electrolyte and the electrodes,forming a strong and stable interfacial layer,thereby improving interfacial and cycling stability.The symmetrical lithium metal cell shows excellent cycle performance of 600 h,and the assembled LiFePO_(4)|Li_(2.4)(OH)1.4Cl|Li cell shows significantly enhanced cycling endurance with 80%capacity retention after 150 cycles.This work not only emphasizes the crucial importance of Young’s modulus in improving interface issues but also offers innovative approaches to advance the mechanical properties of solid electrolytes.

Recent progress in Ti-based nanocomposite anodes for lithium ion batteries

Studying on the anode materials with high energy densities for next-generation lithium-ion batteries(LIBs) is the key for the wide application for electrochemical energy storage devices.Ti-based compounds as promising anode materials are known for their outstanding high-rate capacity and cycling stability as well as improved safety over graphite. However, Ti-based materials still suffer from the low capacity, thus largely limiting their commercialized application. Here, we present an overview of the recent development of Ti-based anode materials in LIBs, and special emphasis is placed on capacity enhancement by rational design of hybrid nanocomposites with conversion-/alloying-type anodes. This review is expected to provide a guidance for designing novel Ti-based materials for energy storage and conversion.

Nanowires-assembled WO3 nanomesh for fast detection of ppb-level NO2 at low temperature

Hierarchical WO3 nanomesh,assembled from single-crystalline WO3 nanowires,is prepared via a hydrothermal method using thiourea(Tu)as the morphology-controlling agent.Formation of the hierarchical architecture comprising of WO3 nanowires takes place via Ostwald ripening mechanism with the growth orientation.The sensor based on WO3 nanomesh has good electrical conductivity and is therefore suitable as NO2 sensing material.The WO3 nanomesh sensor exhibited high response,short response and recovery time,and excellent selectivity towards ppb-level NO2 at low temperature of 160℃.The superior gas performance of the sensor was attributed to the high-purity hexagonal WO3 with high specific surface area,which gives rise to enhanced surface adsorption sites for gas adsorption.The electron depletion theory was used for explaining the NO2-sensing mechanism by the gas adsorption/desorption and charge transfer happened on the surface of WO3 nanomesh.