Lithium scandium phosphate-based electrolytes for solid state lithium rechargeable microbatteries

Li₃Sc₂(PO₄)₃ is a promising candidate for use as an electrolyte in solid state lithium rechargeable microbatteries due to its stability in air, ease of preparation, and resistance to dielectric breakdown. The room temperature ionic conductivity was optimized resulting in an increase of over two orders of magnitude to 3×10⁻⁶S/cm. The formation of Li₃(Sc_2−xM_x)(PO₄)₃, where M=Al³⁺ or Y³⁺, resulted in the decrease of porosity, greater sinterability, and considerable enhancement of the ionic conductivity. Yttrium substitutions enhanced the conductivity slightly while aluminum increased the room temperature ionic conductivity to 1.5×10⁻⁵S/cm for x=0.4. Preliminary electron beam evaporation of Li₃Sc₂(PO₄)₃ yielded amorphous thin films with ion ic conductivity as high as 5×10⁻⁵S/cm and a composition of Li_4.8Sc_1.4(PO₄)₃.     

Nanostructured Ni3Sn2 thin film as anodes for thin film rechargeable lithium batteries

Thin film Ni₃Sn₂ anodes were deposited on a Cu substrate by e-beam evaporator at room temperature. The deposited films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). They were tested as anodes for thin film rechargeable lithium batteries. These film electrodes exhibited an excellent cycle performance over 500 cycles. Ni₃Sn₂ films remained without undergoing any crystallographic phase change during cycling.     

Nanostructured cathode thin films with vertically-aligned nanopores for thin film SOFC and their characteristics

Nanostructured cathode thin films with vertically-aligned nanopores (VANP) were processed using a pulsed laser deposition technique (PLD). These VANP structures enhance the oxygen-gas phase diffusivity, thus improve the overall thin film SOFC performance. La_0.5Sr_0.5CoO₃ (LSCO) and La_0.4Sr_0.6Co_0.8Fe_0.2O₃ (LSCFO) were deposited on various substrates (YSZ, Si and pressed Ce_0.9Gd_0.1O_1.95 disks). Microstructures and properties of the nanostructured cathodes were characterized by TEM, HRTEM, SEM and electrochemical measurements. Additionally these well-aligned VANP structures relieve or partially relieve the internal thermal stress and lattice strain caused by the differences of thermal expansion coefficients and lattice mismatch between the electrode and the electrolyte.     

A thin film triode type carbon nanotube field emission cathode

The field electron emission of carbon nanotubes has been heavily studied over the past two decades for various applications, such as in display technologies, microwave amplifiers, and spacecraft propulsion. However, a commercializable lightweight and internally gated electron source has yet to be realized. This work presents the fabrication and testing of a novel internally gated carbon nanotube field electron emitter. Several specific methods are used to prevent electrical shorting of the gate layer, a common failure for internally gated devices. A unique design is explored where the etch pits extend into the silicon substrate and isotropic etching is used to create a lateral buffer zone between the gate and carbon nanotubes. Carbon nanotubes are self-aligned to and within 10 microns from the gate, which creates large electric fields at low potential inputs. Initial tests confirm high field emission performance with an anode current density (based on total area of the device) of 293 μA?cm^?2 and a gate current density of 1.68 mA?cm^?2 at 250 V.     

Characterization of sprayed and sputtered thin films for lithium ion microbatteries

We have investigated the preparation of thin films of anode and cathode materials for all oxide solid state lithium ion microbatteries. Thin films of LiCoO₂ and Li_4/3Ti_5/3O₄ have been deposited by both spray pyrolysis and RF magnetron sputtering. The structural and electrochemical properties of high temperature-LiCoO₂ thin films have been determined. Spray pyrolysis prepared higher quality LiCoO₂ thin films. Both sprayed and sputtered Li_4/3Ti_5/3O₄ thin films exhibited interesting lithium intercalation capacity. However, it has been demonstrated that RF magnetron sputtering is more efficient than spray pyrolysis for optimizing the interface between Li_4/3Ti_5/3O₄ and the substrate material. Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996     

脉冲阴极弧放电制备碳氮薄膜及其分析

采用高压点火的方式触发脉冲阴极弧放电,在Si(100)衬底上制备出较为光滑、均匀、致密的碳氮薄膜. 研究发现在不同的放电电压与距离对薄膜的沉积起到了很重要的作用. 扫描电镜及电子能谱分析表明,薄膜为非晶碳氮薄膜,并且随沉积能量的增大,氮的含量有所增大. 放电溅射过程分析与实验结果相吻合.     

大面积六硼化镧薄膜阴极制备及性能

 采用电子束蒸发方法在大面积玻璃基底和钽基底上沉积六硼化镧薄膜阴极。分别对玻璃基底上沉积的六硼化镧薄膜的生长取向、附着力与不同蒸发角度(0°, 30°,45°和60°)的关系进行了研究;对钽基底上沉积的六硼化镧薄膜阴极的逸出功进行了研究。结果表明:在基底温度为250 ℃时,制备的六硼化镧薄膜具有(100)晶面择优生长的特点;蒸发角度为45°时,六硼化镧薄膜(100)晶面的晶格常数与靶材相差最小,晶粒较小;根据优化的工艺制备的六硼化镧薄膜阴极的逸出功为2.56 eV。     

大面积六硼化镧薄膜阴极制备及性能

采用电子束蒸发方法在大面积玻璃基底和钽基底上沉积六硼化镧薄膜阴极。分别对玻璃基底上沉积的六硼化镧薄膜的生长取向、附着力与不同蒸发角度(0°, 30°,45°和60°)的关系进行了研究;对钽基底上沉积的六硼化镧薄膜阴极的逸出功进行了研究。结果表明:在基底温度为250 ℃时,制备的六硼化镧薄膜具有(100)晶面择优生长的特点;蒸发角度为45°时,六硼化镧薄膜(100)晶面的晶格常数与靶材相差最小,晶粒较小;根据优化的工艺制备的六硼化镧薄膜阴极的逸出功为2.56 eV。     

Inorganic polymer phosphazene disulfide as cathode material for rechargeable lithium batteries

Novel inorganic network polymer phosphazene disulfide [(NPS₂)₃]_n was synthesized by a solution cross-link method. IR and element content analysis confirmed the polymer's molecular structure. The polymer has an average particle size of d_0.5 = 7.7 μm and the specific surface area is 57.4 m² g^− 1. TG/DTA analysis showed that [(NPS₂)₃]_n underwent a decomposition reaction from 200 to 300 °C. When used as cathode material in lithium batteries, its initial discharge capacity was 459.1 mAh g^− 1, which is almost 93.5% of theoretical specific capacity (490.9 mAh g^− 1). After 30 charge–discharge cycles, the discharge capacity of [(NPS₂)₃]_n stabilized at approximately 400.1 mAh g^− 1 which revealed an excellent cyclic ability. Therefore [(NPS₂)₃]_n is of great potential as cathode material for secondary lithium batteries.     

Characterization of a LiCoO2 thin film cathode grown by pulsed laser deposition

A highly (003)-oriented pure LiCoO₂ thin film cathode, without Co₃O₄ impurities, was grown on a stainless steel substrate by pulsed laser deposition and characterized by electrochemical testing, scanning electron microscopy (SEM), ex situ X-ray diffraction (XRD), Raman and X-ray photoelectron spectroscopy (XPS). The initial reversible discharge capacity of the LiCoO₂ thin film cathode reached 52.5?μAh/cm²µm and capacity loss was about 0.18% per cycle at a current density of 12.74?μA/cm². The chemical diffusion coefficient of the Li⁺ ion was estimated to be about 4.7?×?10^?11?cm²/s from cyclic voltammetric (CV) scans. Ex situ XRD revealed that the spacing of crystalline planes expanded about 0.09?Å when charged to 4.2?V, corresponding to Li_0.5CoO₂, lower than the value for composite powder LiCoO₂ electrodes. XPS results showed that the number of low-coordinated oxygen ions increased relative to the removal of Li⁺ ions.     

La0.82Te0.18MnO3薄膜的输运特性和光诱导效应

用脉冲激光沉积法制备了非金属Te掺杂的钙钛矿锰氧化物La0.82Te0.18MnO3单晶薄膜.该薄膜从83 K升温至373 K过程中发生金属-绝缘体相变,转变点温度为283 K.其电阻率在 T相似文献   

Electrochemical and structural properties of MoO3–V2O5 nanocomposite thin film electrodes for lithium rechargeable batteries

We have investigated the electrochemical properties of V₂O₅-based thin film electrodes as a function of the amount of MoO₃ by means of X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), and transmission electron microscopy (TEM). XRD results show that the V₂O₅-based thin film electrodes give an amorphous characteristic. XPS results reveal the formation of V₂O₅ and MoO₃ phases. TEM results show that MoO₃ dots (5–30 nm in size) are embedded in the amorphous V₂O₅ matrix. It is further shown that cells fabricated with the MoO₃–V₂O₅ nanocomposite thin film electrodes give better cycling performance than those made with the single V₂O₅ thin film electrodes. A possible explanation for the MoO₃ nano-dot dependence on the cycling performance of the V₂O₅-based thin film electrodes is described.     

Structural and electrical studies of LiMnVO4 cathode material for rechargeable lithium batteries

The lithium manganese vanadate (LiMnVO₄) cathode material was synthesized by using sol?Cgel method. The thermal behavior of the material has been examined by thermogravimetric and differential thermal analysis. The structure of LiMnVO₄ compound was studied by the Rietveld refined X-ray diffraction technique. Raman spectra showed that the local environment including VO₄ tetrahedra and LiO₆ octahedra as vibrational local units. X-ray photoelectron spectroscopy studies of synthesized LiMnVO₄ powder indicate that the oxidation states of manganese and vanadate are +2 and +5, respectively. The ionic conductivity of the sample is found to be 2.7?×?10^?5 Scm^?1 at 300?°C. The temperature dependent conductivity was conformed from the Arrhenius relation and the activation energy is found to be 0.3?eV. Dielectric spectra showed the decrease in dielectric constant with increase in frequency. Dielectric loss spectra reveal that dc conduction contribution predominates in the compound.     

Structure and electrochemical characteristics of LiFePO4 cathode materials for rechargeable Li-Ion batteries

Complex investigations of cathode materials for rechargeable lithium-ion batteries have been carried out using the following techniques: scanning electron microscopy, microanalysis, extended X-ray absorption fine structure (EXAFS) spectroscopy, Mössbauer spectroscopy, and porosimetry. Investigations have been performed on samples prepared according to the original technology at the St. Petersburg State Institute of Technology (Technical University) (SPbSTI (TU)) and on four commercial cathode materials. It has been established that there is a correlation between the nanostructured morphology of the cathode materials, their chemical composition, and electrochemical capacity. It has been found that the internal resistance of the LiFePO₄ cathode material is linearly dependent on the diffusion coefficient of lithium ions. The valence state and local coordination of Fe ions have been studied using the ⁵⁷Fe Mössbauer effect. It has been shown that more than 90% of the iron ions are in the valence state Fe²⁺. Based on the data available in the literature on the methods of synthesizing LiFePO₄ and data on the diagnosis of the studied samples, conclusions have been drawn about a modification of the synthesis for producing high-quality cathode materials for Li-ion batteries.     

First-principles investigation of the monoclinic NaMnO2 cathode material for rechargeable Na-ion batteries

Using first-principles calculations, we successfully investigate the electrochemical performance of the monoclinic NaMnO₂ for the sodium ion batteries. NaMnO₂ possesses a voltage window of 3.54–2.52 V and theoretical reversible capacity of 136 mAh g⁻¹. Besides, we find that the metallicity of the monoclinic NaMnO₂ gradually increases during Na extraction. Moreover, the computational Na migration energy barrier in the monoclinic NaMnO₂ is 0.18 eV, ensuring ideal conductivity and reversible capacity. Although the Jahn-Teller distortion effects limit the enhancement of the reversible capacity of the monoclinic NaMnO₂, it is still a right cathode material for the sodium ion batteries. The computational results are well in consistent with the experimental investigations.     

Synthesis of PANI/rGO composite as a cathode material for rechargeable lithium-polymer cells

Graphene oxide (GO) was synthesized by an improved Hummers method and then reduced with NaBH₄; GO became rGO with regular layered structure. Polyaniline (PANI)/rGO composite was prepared by a adsorption double oxidant method with rGO as a template. Some physical characterization methods (Fourier transform infrared spectroscopy analysis, X-ray diffraction, scanning electron microscope, and transmission electron microscope) were used to analyze the morphology and crystallinity of the composite. The electrochemical properties were characterized by cyclic voltammetry, impedance spectroscopy, galvanostatic charge/discharge, and rate capability. The first discharge specific capacity of the rPANI/rGO and PANI/rGO was 181.2 and 147.8 mAh/g. After 100 cycles, the capacity retention rate was still 90.2 and 88.9% separately, and the coulombic efficiency of batteries is close to 100%. These results demonstrate the composite has exciting potentials for the cathode material of lithium-ion battery.     

Electrochemical performance of surfactant-processed LiFePO4 as a cathode material for lithium-ion rechargeable batteries

This study focuses on the effect of addition of surfactant as a dispersing agent during vibratory ball milling of LiFePO₄ (LFP) precursor materials on the electrochemical performance of solid-state reaction synthesized LFP for lithium-ion battery cathode material. LFP particles formed after calcinations of ball milled LFP precursors (Li₂CO₃, FeC₂O₄, and NH₄H₂PO₄) showed better size uniformity, morphology control, and reduced particle size when anionic surfactant (Avanel S-150) was used. The specific surface area of LFP particles increased by approximately twofold on addition of surfactant during milling. These particles showed significantly enhanced cyclic performance during charge/discharge due to a reduced polarization of electrode material. Electrodes fabricated from LFP particles by conventional milling process showed a 22 % decrease in capacity after 50 cycles, whereas the performance of electrode prepared by surfactant processed LFP showed only 3 % loss in capacity. The LFP particles were characterized using XRD, FE-SEM, particle size distribution, density measurement, and BET-specific surface area measurement. Electrochemical impedance spectra and galvanostatic charge/discharge test were performed for the electrochemical performance using coin-type cell.     

First principles study on Mn-doped LiFePO4 as cathode material for rechargeable lithium batteries

The electronic structure and diffusion energy barriers of Li ions in pure and Mn-doped LiFePO4 have been studied using density functional theory （DFT）. The results demonstrate clearly that Fe - O covalent bond is weaker than P- O covalent bond. Pure LiFePO4 has band gap of 0.56 eV and diffusion energy barrier of 2.57 eV for Li ions, while the dopant has small band gap of 0.25 eV and low diffusion energy barrier of 2.31 eV, which indicates that the electronic and ionic conductivity of LiFePO4 have been improved owing to doping.     

Sn(II)-Treated MoO3 as cathode material for rechargeable lithium batteries

We report on the synthesis and structural, thermal and electrochemical characterisation of reduced molybdenum oxides with layered α-MoO₃ type structure. The samples have been prepared by reactions of various amounts of water-free tin dichloride with fine-particulated orthorhombic molybdenum trioxide in n-hexane (non-aqueous media) or in aqueous media, which yielded materials with different Sn:Mo ratio. XRD investigations of these materials proved that the crystal structure of the layered α-MoO₃ has been maintained after the reduction process. No crystalline impurity phases (e.g. tin oxides) could be detected by XRD. The tin-reduced samples exhibited a drastically improved cycling stability and capacity retention on cycling in 1 M LiClO₄/propylene carbonate, i.e. the discharge capacities were well above 100 mAh g⁻¹ after 20 cycles whereas the non-treated MoO₃ (reference sample) has retained only about 45 mAh g⁻¹. At higher cycle numbers (approx. cycle 100) the discharge capacity of the reduced molybdenum oxides stabilises at a level of approx. 100 mAh g⁻¹. This significant improvement of the rechargeability may be related to improved electronic conductivity and/or higher structural stabilisation of the layered MoO₃ structure either due to (i) a coating of the MoO₃ particles with a protective thin layer of a tin containing compounds, and/or (ii) an amorphisation of the structure after reductive treatment. Further efforts of this study were devoted to a variation of the conductive carbon content in the electrode composition and to changes of cut-off voltages and current densities. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.     

4-Volt cathode materials for rechargeable lithium batteries wet-chemistry synthesis, structure and electrochemistry

Lithium transition-metal oxides used as intercalation compounds for rechargeable lithium batteries are widely studied in search of structural stability and improved electrochemical performance. Cathode materials belonging to the 4-volt class electrodes were synthesized by wet-chemistry methods, i.e., sol-gel, combustion or co-precipitation techniques. It is shown that synthesis greatly affects the electrochemistry and cycle life characteristics of the cathodes. Extensive damage including local strain variation, nanodomain formation, and changes in cation ordering, has been observed by local probes such as Raman and FTIR spectroscopy. In this work we wish to show the relationship between the local cationic environment and electrochemical characteristics of the 4-volt cathodes. Materials such as LiMn₂O₄, LiCoO₂, LiNi_1−yCo_yO₂, LiNi_1−yCo_yVO₄, and LiMoVO₆ are investigated.