An Exploratory Investigation of Spinel LiMn1.5Ni0.5O4 as Cathode Material for Potassium-Ion Battery

The emerging interest in K-ion batteries (KIBs) increases the importance of cathodes with high working voltage in this system. The LiMn1.5Ni0.5O4 spinel is a promising alternative for the next generation of high voltage Li-ion positive electrodes and its delithiated structure could be of interest for KIBs. In this work, Li ions are extracted from LiMn1.5Ni0.5O4 by a first electrochemical oxidation. The electroformed lambda-Mn0.75Ni0.25O2 spinel phase is shown to convert into layered K0.5Mn0.75Ni0.25O2 (KMNO) at 20 degrees C along the first discharge in K cell. Then, 0.3 K+/KMNO (90 mAh g(-1)) are reversibly exchanged during the subsequent cycle. Superior electrochemical performance are reported for KMNO as compared to K0.5MnO2 (KMO): a higher working voltage vs. K+/K (3.10 V vs. 2.79 V), enhanced rate capability and better cycling stability (70 mAh g(-1) after 60 cycles at C/20 for KMNO vs. 40 mAh g(-1) for KMO). The contribution of the Ni redox system is revealed as a reason for these improved performances.