Heon-Young Lee

Characteristics of carbon-coated graphite prepared from mixture of graphite and polyvinylchloride as anode materials for lithium ion batteries

Abstract A carbon-coated graphite is investigated as the negative electrode for Li-ion batteries. The carbon-coated graphite particles are prepared by simple heat-treatment of mixtures of graphite and poly(vinyl chloride), PVC, at 800–1000°C in an argon flow. The carbon coating reduces significantly the initial irreversible capacity of the graphite in a propylene carbonate-based electrolyte, by suppressing the solvated lithium ion intercalation, and also improves the initial charge–discharge coulombic efficiency. By carbon coating, the specific surface area of graphite particles is greatly increased. These findings can be explained by assuming that a turbostratic structure of PVC-carbon resists irreversible side-reactions which are controlled predominantly by active, edge surface sites.

Lithium storage properties of nanocrystalline Ni3Sn4 alloys prepared by mechanical alloying

Abstract Nanocrystalline Ni 3 Sn 4 alloy powders prepared by high energy ball milling are examined as an anode for lithium-ion batteries. Ex situ X-ray diffraction (XRD) and differential capacity plots show that crystalline Ni 3 Sn 4 has a low affinity for lithium. In the case of well-developed nanocrystalline Ni 3 Sn 4 , the lithium atoms reversibly react with tin atoms in the grain boundaries with no capacity fading for extended cycling.

Fe/Si multi-layer thin film anodes for lithium rechargeable thin film batteries

Fe/Si multi-layer thin films were prepared by alternate deposition using an electron-beam evaporation method. Electrochemical results through galvanostatic charge–discharge experiments are presented. It appears that the volumetric expansion of silicon during cycling can be effectively suppressed by forming a Fe layer between Si layers. The electrochemical characteristics of Fe/Si multi-layer film electrode can be controlled by the thickness, and number of stacked Si layers, and post-annealing.

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

Abstract Thin film Ni 3 Sn 2 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. Ni 3 Sn 2 films remained without undergoing any crystallographic phase change during cycling.

SUBSTRATE EFFECT ON THE MICROSTRUCTURE AND ELECTROCHEMICAL PROPERTIES IN THE DEPOSITION OF A THIN FILM LICOO2 ELECTRODE

An LiCoO2 thin-film cathode was deposited onto sintered alumina and Si/SiO2 substrates. After annealing at 800°C in O2 for 30 min, the film deposited on alumina consisted of large particles with several cracks, whereas the film deposited on the Si substrate was composed of very small and uniform particles. The films deposited on Si showed improved electrochemical properties, such as peak potential divergence and rate capability, over those for the alumina substrate electrode, which can be attributed to differences of the particle size, surface morphology, and the low electrical resistance of the current collector.

Performance of tin-containing thin-film anodes for rechargeable thin-film batteries

Abstract Thin film, Sn, Cu–Sn and Sn–Zr–(O) anodes for microbatteries are deposited on a copper substrate by radio frequency (rf)-magnetron sputtering at room temperature. Charge–discharge characteristics are compared. It appears that the alloying of Sn with Cu or Zr improves the cycling performance. The best cycling efficiency is obtained when Sn is alloyed with Zr. The effects of alloying elements on the electrochemical properties on the thin film are discussed.

Si–Zr alloy thin-film anodes for microbatteries

Abstract Zr–Si thin films were deposited on copper substrates by co-sputtering method of two pure targets. The structure and surface morphology of the films have been characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). The composition was measured by Rutherford backscattering spectroscopy (RBS) and energy-dispersive X-ray spectroscopy (EDS). The electrochemical results showed that alloying with Zr improves the cycling performance, while as a result the reversible capacity decreases. It appears that the electrochemical cycling performance can be further improved by controlling the film deposition conditions such as substrate temperature and bias sputtering.

Amorphous Lithium Nickel Vanadate Thin-Film Anodes for Rechargeable Lithium Microbatteries

Sputter deposited lithium nickel vanadate thin films are investigated as a possible anode for lithium microbatteries. As-deposited films showed almost amorphous characteristics, but included a small amount of crystalline phase. The electrochemical behavior of thin-film electrodes exhibits consistent voltage charge curves for the first and subsequent cycles, and excellent cycling performance, which are different from the results obtained with bulk electrodes. These characteristics and a high specific capacity make lithium nickel vanadate thin films very attractive candidates for lithium rechargeable microbattery anodes.

Si (–Zr)/Ag multilayer thin-film anodes for microbatteries

Abstract Thin film Si/Ag and (Si–Zr)/Ag multilayer electrodes are fabricated on a Cu substrate by alternate sputtering from Si (–Zr) and Ag at room temperature, and their electrochemical properties are investigated. The insertion of the Ag layer into the Si layer improves the cycling performance. The cyclability can be further improved by doping Zr into the Si layer of the Si/Ag multilayer thin films. The effects of the electrode configuration and the contact stability between the current-collecting layer and the electrode on the cycling performance are discussed.

Hydrogen absorption properties of a Zr–Al alloy ball-milled with Ni powder

Abstract The preparation of the Zr 84 wt%–Al 16 wt% non-evaporable getter alloy by means of mechanical alloying and its hydrogen absorption characteristics were investigated. Scanning electron micorscopy and energy dispersive X-ray analysis revealed that the mechanical ball-milling with Ni was successfully employed to coated nickel particles on the surfaces of the Zr–Al getter alloy. The resulting composite particles with pure nickel on the surface of the Zr–Al getter compound show good gettering performance and fast sorption kinetics without any activation process.