Silicon monoxide (SiO) is a promising next-generation anode material for lithium-ion batteries due to the high capacity it offers. However, such material also exhibits a large initial capacity loss which results in significant loss of Li inventory to irreversible reactions in a full cell. To mitigate the Li inventory loss due to the initial capacity loss of the SiO anode, a prelithiation reagent, Li5FeO4, is added to the LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode, which is then paired with a SiO anode for electrochemical evaluation. The addition of Li5FeO4 leads to a significant 22% improvement in lithium utilization in NCM523. Furthermore, the capacity retention of the full cell increased from 90.94% to 98.92% for 50 cycles. We then further studied the impact of Li5FeO4 addition on the energy density of the cell via modeling. In order to maximize the energy density improvement, thicker electrodes need to be utilized.