Chihiro Yada

Preparation of LiFePO4 thin films by pulsed laser deposition and their electrochemical properties

Olivine structured thin films were prepared by pulsed laser deposition and their electrochemical properties were investigated by cyclic voltammetry (CV) and charge-discharge tests. The resultant films exhibited only a couple of anodic and cathodic peaks at which is characteristic of olivine on CV between 2.0 and 5.0 V (vs. The discharge capacity estimated from the CV obtained at maintained 69% of that obtained at This high rate capability is probably due to the film being so thin that the intrinsically poor electronic conductivity of was not of importance.

Charge-Transfer Reaction at the Lithium Phosphorus Oxynitride Glass Electrolyte/Lithium Manganese Oxide Thin-Film Interface and Its Stability on Cycling

Charge-transfer reaction at a lithium manganese oxide (LiMn 2 O 4 ) thin-film electrode/lithium phosphorus oxynitride glass electrolyte (LiPON) interface was investigated using all-solid-state thin-film batteries (Li/LiPON/LiMn 2 O 4 ). X-ray diffraction measurements revealed that the crystal structure of the thin-film LiMn 2 O 4 electrode changed on depositing the LiPON thin-film electrode, but a thermal treatment at 498 K for 60 min re-formed the original crystal structure. The potential sweep curve of the thermally treated film battery was identical to the cyclic voltammogram of a LiMn 2 O 4 thin-film electrode in a conventional organic electrolyte (1 mol dm -3 LiClO 4 dissolved in propylene carbonate). In contrast to a LiPON/LiCoO 2 interface, the charge-transfer resistance at the LiPON/LiMn 2 O 4 interface did not decrease sufficiently after the thermal treatment relative to the charge-transfer resistance of the organic electrolyte/LiMn 2 O 4 interface. This indicates that there should be a compatible electrode and LiPON film electrolyte combination to obtain an effective decrease in the charge-transfer resistance. Charge-discharge tests revealed that the resultant film battery repeated stable charge-transfer reaction on its cycling compared with the organic electrolyte system. Also, this electrochemical stability was maintained at a high temperature (333 K), which is probably because the formation of the LiMn 2 O 4 /LiPON interface inhibited Mn dissolution from the LiMn 2 O 4 thin-film electrode.

High throughput methodology for synthesis, screening, and optimization of solid state Lithium ion electrolytes

A study of the lithium ion conductor Li(3x)La(2/3-x)TiO(3) solid solution and the surrounding composition space was carried out using a high throughput physical vapor deposition system. An optimum total ionic conductivity value of 5.45 × 10(-4) S cm(-1) was obtained for the composition Li(0.17)La(0.29)Ti(0.54) (Li(3x)La(2/3-x)TiO(3)x = 0.11). This optimum value was calculated using an artificial neural network model based on the empirical data. Due to the large scale of the data set produced and the complexity of synthesis, informatics tools were required to analyze the data. Partition analysis was carried out to determine the synthetic parameters of importance and their threshold values. Multivariate curve resolution and principal component analysis were applied to the diffraction data set. This analysis enabled the construction of phase distribution diagrams, illustrating both the phases obtained and the compositional zones in which they occur. The synthetic technique presented has significant advantages over other thin film and bulk methodologies, in terms of both the compositional range covered and the nature of the materials produced.

Solid-State Lithium-Ion Batteries for Electric Vehicles

Abstract Rapid global industrial development, rising populations and the corresponding increase in the number of vehicles have caused a sudden jump in the consumption of fossil fuel energy. Given this background, the critical issues facing vehicle manufactures can be summarized into the following three: preventing air pollution, reducing CO2 emissions and developing vehicles that can run on a variety of alternative energy sources to petroleum. The most effective way of addressing these issues is considered to be the development of vehicles that can run on electricity, such as hybrid vehicles, plug-in hybrid vehicles, electric vehicles and fuel-cell hybrid vehicles.

Amorphous Li–V–Si–O Thin Films as High-Voltage Negative Electrode Materials for Thin-Film Rechargeable Lithium-Ion Batteries

A new kind of high-voltage negative electrode material for thin-film rechargeable lithium-ion batteries was prepared through electrochemically reductive decomposition of an amorphous Li-V-Si-O thin solid electrolyte film. The thin solid electrolyte film was prepared by pulsed laser deposition, showing 1.3 X 10 -7 S cm -1 in ionic conductivity with negligible electronic conductivity. Electrochemical lithium insertion into the thin solid electrolyte film was observed at ca. 1.7 V (vs Li/Li + ), which was the potential window of the reduction side for the film electrolyte. When the lithium insertion/extraction reaction was repeated over the reductive-side potential window (1.0-4.0 vs Li/Li + ) at low current density, the charge/discharge capacity gradually increased with the repetition of the reaction. Consequently, large charge/discharge capacity (350 mAh g -1 ) was achieved under quasi-open-circuit voltage conditions between 1.2 and 2.7 V (vs Li/Li + ). X-ray photoelectron spectroscopy analysis revealed that the redox reaction of vanadium ions in the film compensated the electrical charge balance for the lithium insertion/extraction reaction of the film electrolyte. The apparent lithium diffusion coefficient of the film was 1 X 10 -15 cm 2 s -1 < D app Li < 2 X 10 -13 cm 2 s -1 .