Rate Discharge vs Particle Size of LiCoO2

This paper was published at 23rd Regional Conference on Solid State Science and Technology 2007 (RCSSST 2007), 27-29 Nov 2007, HYATT REGENCY HOTEL JOHOR BAHRU, MALAYSIA

Figure (a)

Figure (b)

Figure (a) shows Scaning Electron Micrograph (SEM) image of the LiCoO2 crushing using Planetery Ball Milling process in our Laboratory. The Figure shows the changing of particle at various crushing time. The particle size of the LiCoO2 decreased when milling time increased. The longer of crushing time, the smaller particle size. It has a limiting crushing time, longer crushing time might be changing the material phase.

Figure (b) shows correlation between particle size and rate discharge performance of LiCoO2. It is found that the discharge capacity of the fresh sample (0 hour) drastically decreased close to 50% when discharged at 5 mA discharge current. Conversely, when using the small particle size sample, the recovery capacity maintained at 50%, even though the discharge current used is 20mA, which is about 4 times higher than fresh sample (0 hour milling). These results show that particle size plays an important role in synthesizing high power density cathode materials. The increasing in power density for the small particle size is due to the shorten of diffusion path length for lithium ions in the cathode material and a large contact area with conductive additives such as carbon as well as electrolyte. The path length concept is illustrated as figure (c).

Figure (c)