Planetary habitability is enabled by the transfer of volatile substances like H2O from planetary interiors to surfaces during volcanic degassing, but fully degassed rocks will not retain a geochemical record of these processes. The element lithium (Li) is thought to behave moderately volatilely and may function as a proxy for H2O in completely degassed systems, like Martian meteorites. Here we present new experimental measurements of Li partitioning between clinopyroxene and melts to examine if Li trends in Martian meteorites may be attributable to processes other than H2O degassing. We find Li is moderately incompatible in clinopyroxene in both compositions and identify potential partitioning trends with temperature and pressure. We used the new data to model the concentration of Li in cpx during cooling. Our cooling model reproduces Li trends in Martian cpx, suggesting that previous hypotheses regarding H2O in the Martian interior may need to be re-evaluated.