New composite Li1.4Mn0.61Ni0.18Co0.18Al0.03O2.4 and LiNi0.5Mn1.5O3.9F0.1 cathode material with higher specific capacity and better capacity retention

Abstract

Aluminum-modified Li1.4Mn0.61Ni0.18Co0.18Al0.03O2.4 (LNCMA) and fluorine-modified LiNi0.5Mn1.5O3.9F0.1 (LNMOF) cathode materials were successfully synthesized via a solid-state reaction procedure. The discharge capacity of the LNCMA increased from 175.3 to 192.2 mAh g−1, showing approximately a 9.6% improvement after 50 cycles due to Al doping. For the LNMOF cathode, the discharge capacity increased from 116.9 to 174.9 mAh g−1 after F doping, corresponding to an increase of 49.6% after 50 cycles. The new composite cathode was formed by mixing the two cathode materials at a weight ratio of 1:1, which was selected based on the charge–discharge profiles during the first cycle. When the cells were tested in a voltage range of 2.0–4.85 V, the composite material exhibited initial specific capacities of 229.2 and 215.4 mAh g−1, a coulombic efficiency of 94.0% during the first cycle, and a capacity retention of 94.5% after 50 cycles at 0.2C. The concept of inserting irreversible Li ions from the Li-rich material into the 16c vacancy of the LNMOF was validated. The improved capacity was due to the plateau in the discharge capacity curves due to the Mn3+ → Mn2+ reduction. The charge–discharge capacities of the composite material were higher than those in the literature, as was the coulombic efficiency. The new composite material inherited a high-voltage plateau from the LNMOF and a high specific capacity from the LNCMA, and this material has great potential for future applications.