Preparation and characterization of the Li1.12K0.05Mn0.57Ni0.24Nb0.02O2 cathode material with highly improved rate cycling performance for lithium ion batteries

In this work, Li1.12K0.05Mn0.57Ni0.24Nb0.02O2 (LMN-K/Nb) as a novel and high energy density cathode material is successfully synthesized and applied in lithium ion batteries. By combining interlayer exchange and elemental analysis, it can be confirmed that K+ and Nb5+ substitution is respectively in the lithium layer and transition metal (TM) layer since H+ replaces the cations that remain in the lithium layer rather than those in the TM layer. The effect of K+ and Nb5+ co-substitution on the kinetic behavior of insertion/extraction of Li+ is evaluated by electrochemical impedance spectroscopy (EIS), the galvanostatic intermittent titration technique (GITT) and galvanostatic charge/discharge (GCD). LMN-K/Nb delivers an initial capacity of 145 mA h g-1 at 5C rate and 112 mA h g-1 at 10C rate, and maintains 83.1% after 400 cycles at 5C rate and 82.5% at 10C rate. By post-mortem analysis of long-term cycled LMN-K/Nb, K+ and Nb5+ are recognized to play a role in suppressing the irreversible side reactions in LLOs during cycling. This work demonstrates that dual elemental substitution into the lithium layer and TM layer is a feasible strategy to enhance the performance of LLO cathode materials.