A High-Voltage and High-Capacity Li1+XNi0.5Mn1.5O4.0 (0 < x < 1) Cathode Material: From Synthesis to Full Lithium-Ion Cells

Abstract

Improvements of currently available LiB technology are needed to meet the requirements for automotive applications especially in terms of energy density. In the current Li-ion battery technology, the cathode active material represents the main limiting factor for reaching higher values of energy density. Therefore, cathode materials with either increased specific capacity or increased working potential with respect to the currently used active materials are necessary to improve energy density. Moreover, increased safety and reduced cost are needed for large scale applications. The substitution of Co in the cathode structure with more accessible elements is the key for the cost reduction. In this communication, we describe a series of Co-free, Li-rich Li1+xNi0.5Mn1.5O4.0 (0<x<1) compounds obtained via a low-temperature synthetic method. Morphological, structural and electrochemical characterization will be discussed. The lithium‐nickel‐manganese oxide compounds were tailored with respect to morphology, particle size and shape distribution for facile processability during electrode development. The specific particle architecture, consisting of densely packed nano‐sized primary crystallites, allows reaching a tap‐density of 2.4 g cm-3. In the potential range 2.4-4.9 V, the cathode material of composition Li1.5Ni0.5Mn1.5O4 shows a specific capacity of 210 mA h g-1, very good cycling stability and low voltage hysteresis in half-cells vs. lithium. In addition, we demonstrate for the first time the high-voltage and high-capacity cathode application in full Li-ion cells versus graphite anode with very high cycling stability. The initial Li content can be tailored in order to be used for compensating the irreversible capacity loss of the graphite anode in full-cells. The electrochemical mechanism in the low-potential region and the involved phase transitions, studied by different techniques including HR-TEM and XRD, will be discussed together with the electrochemical behavior under different operative conditions. The good electrochemical performance and low cost, together with the feasibility of a chemical method to obtain Li-rich Li1+xNi0.5Mn1.5O4(0<x<1), make practical applications for high-energy density LiBs possible. Acknowledgements This work was supported by the German Federal Ministry of Education and Research (BMBF) in the project Li-EcoSafe (03X4636A).