Electrochemical performance of 5 v LiNi_0.5Mn_1.5O₄cathode modified with lithium carbonate addition in electrolyte

LiNi_0.5Mn_1.5O₄electrode modification is achieved in this work through adding inorganic lithium carbonate (Li₂CO₃) into carbonate electrolyte. Superior cyclic stability of the cathode in the range of 5-2 V is attained, a capacity of 0.3698 mAh g^-1is lost per cycle, which is half of the value in the Li₂CO₃-free condition. The capacity loss above and below 3.5 V are both alleviated in the presence of Li₂CO₃. Its effect on both the electrolyte bulk and the cathode surface is analyzed with SEM, TEM and XPS measurements. The density functional theory (DFT) calculation is carried out to discuss the modification mechanism. It is speculated that Ni⁴⁺⋯CO₃^2-coordination may be formed through the interaction between Ni and O, weakening the oxidizability of Ni⁴⁺on the electrode surface. In addition, Li₂CO₃can consume PF₅in the electrolyte. The interphase film can also maintain thin and steady during the cycling within 5-2 V.