Characterization of Thin‐Film Rechargeable Lithium Batteries with Lithium Cobalt Oxide Cathodes

Abstract

Thin-film rechargeable lithium batteries with amorphous and crystafline LiCoO2 cathodes were investigated, The lithium cobalt oxide films were deposited by radio-frequency (RF) magnetron sputtering of an LiCoO2 target in a 3:1 Ar/02 mixture gas. From proton-induced -y-ray emission analysis (PIGE) and Rutherford backscatterung spectrometry (RBS), the average composition of these films was determined to be Li115CoO216 or, within experimental uncertainty, LiCoO2 + 0.08 Li20. The x-ray powder diffraction patterns of films annealed in air at 500 to 7 00°C were consistent with the regular hexagonal structure observed for crystalline LiCoO2. The discharge curves of the cells with amorphous LiCoO2 cathodes showed no obvious structural transition between 4.2 and 2.0 V, while the discharge curves of the cells with polycrystalline cathodes were consistent with a two-phase potential plateau at -3.9 V with a relatively large capacity. Two lower capacity plateaus were observed at ---4.2 and 4.1 V with the 600 and 700°C annealed cathodes; the -dq/dV peaks were broader and weaker for the 600°C annealed cathodes and were not present at all with the 500°C annealed films. The chemical diffusion coefficients of Li in the cathodes obtained from ac impedance measurements at cell potentials of -4 V ranged from ,1012 cm2/s for the as-deposited amorphous cathodes to --10 cm2/s for the films annealed at 700°C. The capacity loss on extended cycling of the thin-film cells varied with the crystallinity and thickness of the cathodes and with temperature. With the highly crystalline, 700°C annealed material, losses on cycling between 4.2 and 3.8 V at 25°C ranged from 0.0001%/cycle (>1O cycles) to 0.002%/cycle for cells with cathodes from 0.05 to 0.5 m thick.

High-Yield One-Pot Recovery and Characterization of Nanostructured Cobalt Oxalate from Spent Lithium-Ion Batteries and Successive Re-Synthesis of LiCoO2

“…The voltage profiles show that the discharge capacity was improved from 79.8 mA·h·g −1 in the sample calcined at 400 • C to 131 mA·h·g −1 in the one at 900 • C with increasing calcination temperature. This result is in good agreement with our XRD results, indicating that high temperature calcination induces a high degree of cation ordering [31,36]. It has been reported that the Li ion inserts more efficiently for a sample with a lower degree of cation ordering in a textured electrode structure thanks to a greater number of electrochemical active sites and a shorter diffusion length than a sample with a higher degree of cation ordering [30,35,37].…”

Electrochemical Evaluation of Active Materials for Lithium Ion Batteries by One (Single) Particle Measurement

“…Another useful method is an electrochemical measurement with a thin film of active material. 11,12 However, some active materials cannot be prepared in a thin film form due to chemical characteristics of materials. In addition, the thin films of active materials are not exactly same with the particles of active materials used in practical batteries.…”

Perfect reversibility of the lithium insertion in FeS2: The combined effects of all-solid-state and thin film cell configurations

“…The successive reduction of both S 2− and Fe 2+ species led to an impressive volumetric discharge capacity, five times higher than the one for LiCoO 2 . Excellent reversibility and capacity retention were obtained during the first and the subsequent 800 charge-discharge cycles.…”