Electrochemical characteristics of lithium-excess cathode material (Li_(1+x)Ni_(0.9)Co_(0.05)Ti_(0.05)O_2) for lithium-ion batteries

摘要

A Ni0.9Co0.05Ti0.05(OH)(2) precursor was synthesized with the concentration gradient method. To overcome the Li-ion shortage the problem due to the formation of a solid electrolyte interphase (SEI) layer during the initial charge/discharge process in the cathode material, lithium-excess Li1+xNi0.9Co0.05Ti0.05O2 (0 = x = 0.07) cathode materials were investigated by physical and electrochemical analyses. The physical properties of the lithium-excess cathode materials were analyzed using FE-SEM and XRD. A coin type half-cell was fabricated with the electrolyte of 1M LiPF6 dissolved in organic solvents (EC:EMC=1: 2 vol%). The electrochemical performances were analyzed by the initial charge/discharge efficiency, cycle stability, rate performance and electrochemical impedance spectroscopy (EIS). The initial charge capacity of the cathode material was excellent at about 199.8-201.7 mAh/g when the Li/Metal ratio was 1.03-1.07. Additionally, the efficiency of the 6.0 C/0.1 C was 79.2-79.9%. When the Li/Metal ratio was 1.05, the capacity retention showed the highest stability of 97.8% after 50 cycles.