Lithium–CO 2 batteries are attractive energy‐storage systems for fulfilling the demand of future large‐scale applications such as electric vehicles due to their high specific energy density. However, a major challenge with Li–CO 2 batteries is to attain reversible formation and decomposition of the Li 2 CO 3 and carbon discharge products. A fully reversible Li–CO 2 battery is developed with overall carbon neutrality using MoS 2 nanoflakes as a cathode catalyst combined with an ionic liquid/dimethyl sulfoxide electrolyte. This combination of materials produces a multicomponent composite (Li 2 CO 3 /C) product. The battery shows a superior long cycle life of 500 for a fixed 500 mAh g−1 capacity per cycle, far exceeding the best cycling stability reported in Li–CO 2 batteries. The long cycle life demonstrates that chemical transformations, making and breaking covalent CO bonds can be used in energy‐storage systems. Theoretical calculations are used to deduce a mechanism for the reversible discharge/charge processes and explain how the carbon interface with Li 2 CO 3 provides the electronic conduction needed for the oxidation of Li 2 CO 3 and carbon to generate the CO 2 on charge. This achievement paves the way for the use of CO 2 in advanced energy‐storage systems.