Increased specific capacity and/or working potential are important prerequisites for high energy functional materials for lithium-ion batteries. Furthermore practical applications require materials with high tap density in order to maximize the loading of the electrodes, thereby optimizing the energy density on cell level. Stoichiometric and phase pure LiNi0.5Mn1.5O4 (LMNO) has been synthesised via a continuous co-precipitation and lithiation process, suited for large scale production. Powder properties have been controlled in order to obtain spherical particles consisting of a multitude of densely-packed primary crystallites. The obtained material exhibits a single plateau at 4.7 V vs. Li/Li+ with high capacity, rate capability and cycling stability. Morphological factors such as crystallite size, particle size and particle architecture, and additionally the variation of oxygen stoichiometry have been investigated. This study clearly illustrates the importance of these factors on the electrochemical performance of an optimized LMNO high-voltage material.