The effects of persulfate treatment on the electrochemical properties of Li[Li0.2Mn0.54Ni0.13Co0.13]O-2 cathode material

Spherical Li[Li0.2Mn0.54Ni0.13Co0.13]O-2 material was treated with persulfates Na2S2O8 or (NH4)(2)S2O8 to extract lithium to increase the coulombic efficiency of the first cycle. The two persulfates showed different effects. Na2S2O8 greatly improved the first cycle efficiency of the active material to nearly 100%. The rate performance was also increased to more than 200 mAh g(-1) at 1C rate. The reason for the improved rate performance by the treatment of Na2S2O8 is attributed to the formation of spinel phase on the surface of the material and the extraction of lithium and oxygen, which results in a decreased electrochemical resistance, whereas the treatment with (NH4)(2)S2O8 deteriorated the electrochemical performance of the Li-rich compound due to the Li+/H+ exchange and the collapse of the layered structure. (C) 2012 Elsevier B.V. All rights reserved.