Functionalized Graphitic Carbon Nitride for Efficient Energy Storage

Using first-principles calculations based on density functional theory, we show that recently synthesized graphitic carbon nitride (g-C4N3 and g-C3N4) can be functionalized with Li atoms for use as materials not only for high-capacity hydrogen storage but also for lithium-ion batteries. The unique properties are due to the high density of Li ions firmly adsorbed over nitrogen triangular holes. The gravimetric and volumetric densities of hydrogen in Li2C3N4 and Li2C4N3 are greater than 10 wt % and 100 g/L, respectively, both exceeding the target set by the U.S. Department of Energy. Similarly, single-layer Li2C3N4 is a good candidate for a lithium-ion anode material with a specific capacity almost twice that of graphite, and bulk LiC4N3 can be used as a cathode material with a specific energy twice that of LiCoO2. The materials have the added advantage that they are stable against clustering of Li and are nontoxic.