As illustrated by Fig. (b), full two layers of Li can be stored on both Janus MXenes, since the voltage is positive from 0 to 2 ion content. However, only Ti 2 CSO monolayer can adsorb two Mg layers. The maximum Mg ion content for Ti 2 CSSe was computed as 1.67. To further investigate the storage properties, we determined the gravimetric capacity based on the following equation,