Effect of LiCoO[sub 2] Cathode Nanoparticle Size on High Rate Performance for Li-Ion Batteries

The effect of cathode nanoparticle size on high-rate performance in Li-ion batteries was investigated using hydrothermally prepared oleylamine-capped nanoparticles with a particle size of obtained at . Upon annealing as-prepared at 500, 700, and , the particle size increased to , , and , respectively. Ex situ transmission electron microscopy and X-ray diffraction results indicated that the thickness of the solid electrolyte interface (SEI) affected the particle's electrochemical properties at high rates. A cathode with a smaller particle size had a thicker SEI layer, which acted as a barrier for Li-ion diffusion, resulting in deteriorated rate capabilities at higher C rates. However, irrespective of the particle size, there was no structural degradation after cycling. Rate capability tests were performed under two different electrode densities (3.4 and ), and with a particle size of demonstrated the best rate capability at higher C rates. Upon extended cycling at the rate, with a particle size of exhibited 87 and under 3.4 and , respectively.