Abstract: The chemical composition of Li（Mn，Co，Ni）O2  has firstly appeared as the dopant of LiCoO2  and LiNiO2  in the late 1990s and the research treating it as an independent material started from 2001.In the Li（Mn，Co，Ni）O2 ，Ni2+ is the main electro-active element and Mn4+，as the non-electro-active element improves the structure and thermal stability.While Co3+ partially participates in electrochemical reaction，and its main function improves the structural integrity and the rate capability，and reduces electro-chemical polarization of material.It is believed that Li（Mn，Co，Ni）O2  will be the most promising cathode material for lithium ion batteries due to its higher capacity，structural stability，and fine safety at the higher charge voltage.

Key words: Li（Mn, Co, Ni）O2 ；lithium ion battery；cathode materials