Synthesis and electrochemical properties of Li[Ni x Co y Mn 1− x − y ]O 2 ( x, y = 2/8, 3/8) cathode materials for lithium ion batteries

Abstract The uniform layered Li(Ni 2/8 Co 3/8 Mn 3/8 )O 2 , Li(Ni 3/8 Co 2/8 Mn 3/8 )O 2 , and Li(Ni 3/8 Co 3/8 Mn 2/8 )O 2 cathode materials for lithium ion batteries were prepared using the hydroxide co‐precipitation method. The effects of calcination temperature and transition metal contents on the structure and electrochemical properties of the Li‐Ni‐Co‐Mn‐O were systemically studied. The results of XRD and electrochemical performance measurement show that the ideal preparation conditions were to prepare the Li(Ni 3/8 Co 3/8 Mn 2/8 )O 2 cathode material calcined at 900°C for 10 h. The well‐ordered Li(Ni 3/8 Co 3/8 Mn 2/8 )O 2 synthesized under the optimal conditions has the I 003 / I 104 ratio of 1.25 and the R value of 0.48 and delivers the initial discharge capacity of 172.9 mA·h·g −1 , the discharge capacity of 166.2 mA·h·g −1 after 20 cycles at 0.2C rate, and the impedance of 558 Ω after the first cycle. The decrease of Ni content results in the decrease of discharge capacity and the bad cycling performance of the Li‐Ni‐Co‐Mn‐O cathode materials, but the decreases of Mn content and Co content to a certain extent can improve the electrochemical properties of the Li‐Ni‐Co‐Mn‐O cathode materials.