About the microstructure of cathodes in Li ion batteries, which one of the following requirements is not necessary? A) Li ions can reach most particles of active cathode material (such as Li1-xC0O2). B) Electrons can reach most particles of active cathode material. C) The average size of active cathode material particles should be small to speed up the diffusion of Li ion. D) The interfaces between the active cathode material particles and the binder materials should be coherent.