Rechargeable magnesium batteries have attracted recent research attention because of abundant raw materials and their relatively low‐price and high‐safety characteristics. However, the sluggish kinetics of the intercalated Mg2+ ions in the electrode materials originates from the high polarizing ability of the Mg2+ ion and hinders its electrochemical properties. Here we report a facile approach to improve the electrochemical energy storage capability of the Li4Ti5O12 electrode in a Mg battery system by the synergy between Mg2+ and Li+ ions. By tuning the hybrid electrolyte of Mg2+ and Li+ ions, both the reversible capacity and the kinetic properties of large Li4Ti5O12 nanoparticles attain remarkable improvement.