Will cheap, sustainable Na-ion batteries soon replace the current Li-ion battery technology? One of the main challenges to be overcome for the commercialization of Na- ion batteries lies in ﬁnding better Na-ion cathode materials. Sodium manganese oxides, NaxMnO2, typically have a high energy density per unit volume. Yet, these layered materials undergo a number of phase transitions upon electrochemical cycling which limit their cycle life. In this talk we will see how solid-state NMR and Density Functional Theory can be used in combination to understand the structural and electronic processes occurring upon electrochemical cycling of NaxMnO2–type compounds. In particular, we have found that NMR spectroscopy can give us invaluable information on the eﬀect introducing of dopant species on the transition metal lattice to enhance the structural stability and the electrochemical performance of NaxMnO2 cathodes.