Improved electrochemical performance of NaAlO2-coated LiCoO2 for lithium-ion batteries

NaAlO2-coated LiCoO2 materials have been synthesized as cathode materials for lithium-ion batteries. The NaAlO2 layer is coated on the LiCoO2 particles successfully. NaAlO2-coated LiCoO2 materials exhibit the improved cycling stability and rate capability at a high cutoff voltage of 4.5 V vs Li+/Li. The LiCoO2 sample coated by 2 wt.% NaAlO2 demonstrates the excellent cyclability with a capacity retention of 95.7 % after 50 cycles at 100 mA g(-1). In the meantime, the sample shows superior rate performance, delivering a quite high capacity of over 135 mA h g(-1) at a current density of 1600 mA g(-1), corresponding to 73.4 % of the capacity at 20 mA g(-1). NaAlO2-coating layer acts as a physical barrier that separates the LCO electrode and electrolyte, which will suppress the oxidation of solvents, dissolution of cobalt ions, and the evolution of oxygen at high cutoff voltage. Moreover, the NaAlO2 layer can provide two-dimensional ion diffusion channel for lithium ions, resulting in improvement of electrochemical performance for LiCoO2.