Electrochemical effects of ALD surface modification on combustion synthesized LiNi_(1/3)Mn_(1/3)Co_(1/3)O_2 as a layered-cathode material

摘要

Combustion synthesized Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 particles are coated with thin, conformal layers of Al_2O_3 by atomic layer deposition (ALD). XRD, Raman, and FTIR are used to confirm that no change to the bulk, local structure occurs after coating. Electrochemical impedance spectroscopy (EIS) results indicate that the surface of the Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 are protected from dissolution and HF attack after only 4-layers, or ~8.8 Å of alumina. Electrochemical performance at an upper cutoff of 4.5 V is greatly enhanced after the growth of AI2O3 surface film. Capacity retention is increased from 65% to 91% after 100 cycles at a rate of C/2 with the addition of only two atomic layers. Due to the conformal coating, the effects on Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 overpotential and capacity are negligible below six ALD-layers. We propose that the use of ALD for coating on Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 particles makes the material a stronger replacement candidate for LiCoO_2 as a positive electrode in lithium ion batteries.