This thesis describes in-depth theoretical efforts to understand the reaction mechanism of graphite and lithium metal as anodes for next-generation rechargeable batteries. The first part deals with Na intercalation chemistry in graphite, whose understanding is crucial for utilizing graphite as an anode for Na-ion batteries. The author demonstrates that Na ion intercalation in graphite is thermodynamically unstable because of the unfavorable Na-graphene interaction. To address this issue, the inclusion of screening moieties, such as solvents, is suggested and proven to enable reversible...