Compensation of irreversible capacity losses is a mandatory task if high capacity alloy and conversion materials want to be used in tomorrow Li-ion batteries, thus enabling further increase of the cell energy. To that aim we here propose a new approach that is based on the use of blend cathodes containing morphologically optimized LiNi0.5Mn1.5O4 (LMNO-O) and lithium-rich Li1+xNi0.5Mn1.5O4 (LMNO-R) to compensate the irreversible losses of lithium-ion cells that employ Si-based anodes. The ratio between LMNO-O and LMNO-R determines the amount of extra lithium available in the electrodes and thus the use of blend electrodes allows fine tuning of the extra-charge within the cathode. Furthermore, the lithium rich phase converts to the standard electrochemically active spinel phase when all the extra lithium leaves the structure, thus not accounting for any inert weight in the cell. We demonstrate that the aforementioned approach leads not only to the full compensation of irreversible capacity losses, but it also improves the cells' cycling stability. Finally, our optimized cells show 25% more specific energy with respect to a reference Graphite|LiNi0.5Mn1.5O4 cell.