Lithium cobalt oxide as cathode material of rechargeable lithium battery

Lithium cobalt oxide is the negative electrode material of rechargeable lithium batteries. The structure of LiCoO2 is composed of replacement layers of lithium and cobalt atoms occupying the octahedral orientation of the rhombohedral lattice. After the corresponding cobalt oxidation modification, lithium ions can be reversibly extracted from these layers. In recent years, lithium cobalt oxide films have been used as the counter electrode of electrochromic windows and the cathode of lithium batteries (7-10). Our laboratory has conducted many years of research on thin film lithium batteries based on V20s and LiMn2O4 cathodes (11-13). In order to extend our discussion to other cathode data, we studied the function of LiCoO2 thin film deposited by magnetron sputtering and its behavior in thin-film rechargeable lithium batteries. The lithium cobalt oxide film was prepared on Coorsads-996 alumina plate by planar radio frequency magnetron sputtering. In some cases, these films are deposited together on graphite and serve as a substrate for ion beam and nuclear analysis. The principle is prepared by using pure LiCoO2 (Aifa, 99.5%) as raw material and cold-constrained sintering at 900°C for 2 hours. After treatment, the policy measures 2 inches in diameter and about 3 mm thick. The flow of Ar and 02 into the vacuum chamber is adjusted with a total flow of 12-5SCCM to maintain a 3/1Ar/O2 ratio and a constant pressure of 20mTorr. Assuming that the film density is 5.06 g/cm3 and the stacking speed is measured before and after the quartz crystal stack thickness is monitored and positioned above 5 cm, the policy is usually 7-12/min and the net power utilization rate is 40-50w. After 1h sputtering policy, the substrate is rotated into place more than 5 cm policy. The emission spectrum of the plasma is periodically recorded by the previously described device (i4). The intensity of the lithium emission line at -671nm is basically the same as the intensity of the argon emission line at -750nm, and the deposition rate before and after deposition is basically the same, indicating that the sputtering process is stable. The cathode film was deposited through an aluminum mask with an area of u200bu200b11 mm x 11 mm. The thickness of the cathode varies between 0.3-0.5um measured by the profiler, which is very consistent with the estimated thickness of the rate measurement assuming the theoretical density of 5.06g/cm3. Based on this density, the estimated mass of the cathode is 0.2-0.3 mg. After stacking, the cathode part was annealed at 500-700°C in the FG experimental rotary kiln for 2 hours and gradually cooled to room temperature. The composition of the cathode film deposited on the graphite substrate was measured by proton induced yray emission method (PIGE) and Rutherford backscattering spectroscopy (RBS), and the lithium/cobalt ratio was obtained. An analogy of the Royal Bank of Scotland spectrum. As shown in Figure 1, the solid line simulates backscattering to obtain the Co/O ratio. The ratio of Li/Co and O/Co measured by PIGE and RBS was 1.15. (±0.02) and 2.16 (±0.13) to obtain a uniform film composition of lil15co02.16. The data collection method is 20-70, and the scanning speed is 3/min. The deposited film is x-ray amorphous. Figure 2 shows an example of the diffraction pattern of a LiCoO2 film annealed on a Coors alumina substrate. After annealing, a peak appears at 20u003d18.64, which can be diffracted from the (003) plane of the d-nafeo structure of LiCo02. The temperature change of the annealed film's DC resistivity was measured by the four-probe method and the silver paint contact method. The effect is shown in Figure 3. The resistivity of the film increases as the temperature decreases, and the resistivity of the semiconductor data increases as the temperature decreases. The resistivity at room temperature is -2s2cm. Previous thermoelectric studies on bulk and thin fims have shown that LiCoO2 is a p-type semiconductor, and electron holes are important carriers (7). Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete.