In the search for high-energy Li-ion positive electrodes, the layered lithium NMC oxides have been studied extensively. Despite wide interest in this system, until recently, the phase diagram remained poorly understood resulting in many conflicting reports in the literature. Combinatorial synthesis, coupled with X-ray diffraction, was used to determine the phase diagrams under various synthesis conditions [1-2]. The unexpected complexity seen in this system included multiple 3-phase regions that transform during cooling along with boundaries to single phase regions which shift during cooling. Despite the deepended understanding of the structural phase diagram, there now remains a very limited exploration of how the electrochemical properties evolve across these complex phase spaces. Herein, we adapt a high-throughput electrochemical testing system wherein 64 samples are cycled simultaneously in order to measure the cycling of the mg-scale powder combinatorial samples. The methodology involves using a solution-dispensing robot is used to make the samples by co-precipitation synthesis followed by high temperature annealing. The samples are subsequently mounted in the combinatorial electrochemical cell and cycled simultaneously. Given that the combinatorial samples here are powders, made using synthesis methods comparable to those used commercially, the results scale-up very well. Beyond the proof-of-concept of the novel high-throughput measurements, results on hundreds of samples in the Li-Mn-Ni-Co-O system of extreme interest as next-generation positive electrodes will be presented. Consequences for further studies in this popular composition space will be discussed.

References:

[1] McCalla, E., Rowe, A. W., Shunmugasundaram, R., & Dahn, J. R. (2013). Structural study of the Li–Mn–Ni oxide Pseudoternary system of interest for positive electrodes of Li-ion batteries. Chemistry of Materials, 25(6), 989-999.

[2] Brown, C. R., McCalla, E., Watson, C., & Dahn, J. R. (2015). Combinatorial study of the Li–Ni–Mn–Co oxide pseudoquaternary system for use in Li–Ion battery materials research. ACS combinatorial science, 17(6), 381-391.