Effects of lithium excess and Ni content on the electrochemical performance of Li1+x (Ni0.45−xMn0.4Co0.15) O2 lithium-ion cathode materials in stoichiometric state

Abstract

In Li-ion batteries, application of active materials can enhance the kinetics of the charge-discharge process, reduce the costs and improve the safety of the system. In this work, the effect of nickel content and lithium excess in Li1+x (Ni0.4−xMn0.5Co0.1) O2 compounds on the electrochemical performance of the lithium-ion battery cathode have been studies. For this purpose, three compounds of NMC in the stoichiometric state were synthesized via co-precipitation as the cathode active material. XRF and EDS analyses indicate that precursors and oxide compounds are well synthesized. The final compound of synthesized cathodes was obtained by ICP analysis. XRD results also suggest that the hydroxide and oxide phases are formed appropriately. SEM results show that the particle size of the synthesized samples ranges from 1–2 μm. As the content of nickel increases (sample 3), particle sizes also increase. The battery charge-discharge test results (at rates of 0.1–5 C) show that when the nickel content is 0.45, the cycle life of the sample 3 is lower than the other two (154 mAh g−1 at discharge rate 1 C). While the discharge capacity for the sample 1 at 1 C and 5 C rates after 30 cycles is 176.9 mAh g−1 and 101.4 mAh g−1, respectively. Therefore, as a result, to increase the cathode capacity, the amount of lithium can be increased as well as the amount of nickel can be reduced in a stoichiometric state.