We report the development of a rechargeable lithium ion battery with homogeneous mixing of 10% of graphene oxide in active LiMn1.5Ni0.4Cr0.1O4 cathode material for enhanced electrochemical performance. The redox behavior of the cell, which is normally too slow for practical applications, is accelerated with highly conductive graphene. Intimate mixing of the two materials is achieved by a slurry maker using an organic solution for a cathode paste. The fabricated electrode is repeatedly charged/discharge at C/10 and C/2 rates without any significant degradation in the electrochemical capacity. The gravimetric energy density of the composite cathode material exceeds that of the LiMn1.5Ni0.4Cr0.1O4 oxide electrode in lithium-ion batteries, and the addition of graphene in active material is likely to prove advantageous in applications where weight, rather than volume, is a critical factor.