Abstract
The development of Na‐ion batteries is currently regarded as a sustainable, cheaper and long‐lasting technology compared to that of Li‐ion batteries. This chapter provides a general overview of the hard carbons. It focuses on the description of the main synthesis routes used to prepare hard carbons with a focus on the impact of the precursor type and synthesis conditions on the hard carbon characteristics. The chapter emphasizes the structural, textural and surface chemistry aspects through several selected examples. It discusses the performance in half‐cell and full‐cell in relation with the hard carbon properties. The chapter deals with the sodium storage mechanisms. The main synthesis procedures to obtain hard carbon includes synthetic precursors‐based hard carbon synthesis, bio‐polymers derived hard carbon synthesis and biomass‐based hard carbon synthesis. Surface area, open porosity and closed porosity are key parameters to investigate for hard carbon materials.