First, to push the depth of intercalation to 1-v of 0.94 during Li + extraction and maintain two-phase equilibrium, the effect of particle size was investigated. It has been demonstrated that particle dimension is an important factor to determine the ion exchange kinetics of solid materials such as nanocrystals and clays . We studied the ion exchange kinetics of three different layered cobalt oxides: commercial O3 LiCoO2 (LCO), synthesized smaller O3 LiCoO2 (sLCO), and synthesized P'3 Na0.67CoO2 (NCO). Their X-ray diffraction (XRD) patterns are shown in Supplementary Fig. . The LCO are single primary particles of irregular shapes with dimension of 11.1 ± 4.9 µm (Scanning electron microscopy (SEM), Fig. ). The sLCO and NCO are both platelet like particles. The sLCO has lateral size of 1.04 ± 0.24 µm and thickness of 420 ± 100 nm (Fig. ). The NCO has lateral size of 194 ± 66 nm and thickness of 96 ± 29 nm (Scanning transmission electron microscopy (STEM), Fig ). Particle sizes are summarized in Supplementary Table . The NCO are smaller due to their lower temperature requirement for solid state synthesis . The larger (lateral) surface for the platelet type particles is the (001) surface, which has negligible alkali cation diffusion coefficient .