LiC2, the super dense high pressure phase of lithium-intercalated graphite, has been tested in a two-electrode cell vs. Li with an organic electrolyte. A primary capacity of 910 mAh/g per carbon atom was observed during the first deintercalation cycle at constant current, almost three times greater than the ideal 372 mAh/g value for the normal saturated-phase LiC6. LiC2 also exhibited the desirable characteristic of a low and flat working voltage profile, and most of the Li was removed at similar to 18 mV. The first deintercalation cycle also showed weak anomalies which coincide with previously identified phase transitions between high order Li in-plane superlattices. Repeated cycling yielded a reversible capacity close to 372 mAh/g, with Li removed at similar to 100 mV. The high initial capacity and near ideal reversible secondary capacity suggests that this material could be useful in rechargeable batteries requiring a very large first deintercalation capacity.