Surface modification studies have been carried out to suppress side reactions for both NCA and NMC cathodes . SiO2, TiO2 and Li2ZrO3 have been investigated as coating materials to improve the thermal stability of NMC. Fluorine has been studied as one of the coating materials for NCA. Fluorine coating substitutes oxygen and enhances the stability of the lattice due to its higher electronegativity and strong metal-fluoride bonds . A combination of fluorine and zirconium coating and FeF3 coatings have also been proposed . These coatings improve capacity retention even at high cycle life. MgF2 coated NCA gives good rate capability .