Due to their promise of high specific capacity layered lithium rich nickel manganese oxide materials have a large body of literature dedicated to their structure, and electrochemical behaviors. Yet these materials have often been marred by significant capacity losses, rate capability limitations, and structural instability over the course of cycling. Several techniques involving surface and structural modifications have been used to mitigate these capacity losses. In this work we used a hybrid acetate/nitrate precursors and sol-gel/combustion synthesis to conduct an unprecedented combined survey of the composition of Li(Ni_xLi_((1/3-2x/3))Mn_((2/3-x/3)))O_2, and synthetic quench rates to elucidate the effects of these variables on electrochemical cycling behavior, bulk morphology, and surface morphology of the layered lithium rich manganese oxides. We find that the electrochemical behavior of these materials is dependent on both the nickel content as well as the quenching method, with a lower limit on the nickel content beyond which the effects of quenching are minimal. Despite XRD revealing loss of super lattice peaks indicating a loss of transition metal ordering, often associated with capacity loss, galvanostatic cycling of samples saw improved capacities over the course of cycling. SEM found bulk morphology of cathodes differs across nickel contents, yet it did not experience large changes over the course of cycling. The use of TEM found that the surfaces of Li(Ni_xLi_((1/3-2x/3))Mn_((2/3-x/3)))O_2 powders is highly sensitive to quenching method, and comparison of surfaces over the course of cycling provided incites into the effects of quenching and nickel content on electrochemical cycling behaviors of the cathode materials. This investigation reveals that careful considerations in synthesis are required for the realization of high-performance layered lithium rich nickel manganese oxides.
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