Pretreated precursor to realize dual modification that improves the high voltage electrochemical performance of LiNi0.8Co0.1Mn0.1O2 cathode materials

摘要

Ni-rich cathodes have been increasingly studied due to their satisfactory capacity and low cost. However, the rapid attenuation of capacity during charging and discharging Ni-rich cathodes limits their practical use. In this work, a KMnO4-pretreated precursor is used to synthesize LiNi0.8Co0.1Mn0.1O2 (NCM811) in air. The product shows various morphological and structural characterizations, thereby verifying that the pretreatment can successfully achieve the dual modification of a MnO2 coating and Mn4+ doping. Electrochemical tests indicate that the 1.0 wt% KMnO4-pretreated sample exhibits superior cycling performance from 3.0 to 4.5 V. Additionally, the capacity retention rate after 100 cycles reaches 79.15% at 0.2 C, which shows that the pretreated sample has better cycling stability compared with the pure sample calcined in air (59.22%) and the pure sample calcined in oxygen (71.17%). In addition, the capacity retention reaches 82.27% at a high current density of 1 C while suppressing the potential polarization. Cyclic voltammetry and electrochemical impedance spectroscopy tests show that the pretreatment decreases the resistance and suppresses the irreversible phase transition. The protective MnO2 coating inhibits the interfacial reactions between the active substance and electrolyte, while the Mn4+ dopant improves the crystal structure. Therefore, it is concluded that LiNi0.8Co0.1Mn0.1O2, with a superior electrochemical performance at a high of 4.5 V, can be prepared through a KMnO4-pretreated precursor in air. (C) 2020 Elsevier B.V. All rights reserved.