Effect of potassium doping on the electrochemical properties of 0.5Li₂MnO₃-0.5LiMn_0.375Ni_0.375Co_0.25O₂ cathode

In the realm of next generation cathode materials for Li-ion rechargeable batteries, Li and Mn riched (LMR) cathodes are important candidate because of its high nominal voltages and specific discharge capacities. However, capacity and voltage fade in LMR cathodes are attributed to the formation of spinel like phase with repeated cycling. In the present work, LMR cathode of composition 0.5Li₂MnO₃-0.5LiMn_0.375Ni_0.375Co_0.25O₂ (layered notation Li_1.2Mn_0.55Ni_0.15Co_0.1O₂) and its potassium doped variants are investigated in terms of their structural and electrochemical behavior. The cycleability, rate capability and voltage fade characteristics of potassium doped cathodes are found to be improved as compared to the undoped cathode. Thus, Li_1.184K_0.016Mn_0.55Ni_0.15Co_0.1O₂LMR cathode yields a capacity retention ∼86% after 50 charge-discharge cycles. Using X-ray diffraction and Raman spectroscopy analyses in conjunction with impedance spectroscopy, X-ray photoelectron spectroscopy, and galvanostatic intermittent titration technique we have established that cycling induced layered to spinel phase transition is retarded in K doped LMR cathodes to yield improved electrochemical performance and voltage fade characteristics.