Unveiling pseudocapacitive behavior of hard carbon anode materials for sodium-ion batteries

Hard carbon is the most prospective anode material for sodium-ion batteries with outstanding electrochemical performance. However, the type of reaction associated with charge storage is a subject of contentious deliberations within the scientific society. We examined the pseudocapacitive behavior of glucose-derived hard carbon with different porosity by detailed linear sweep voltammetric analysis which demonstrated the presence of three distinct processes occurring during Na+-deinsertion. A combination of pseudocapacitive-intercalation-pseudocapacitive behavior for all synthesized hard carbons is proposed. Obtained results differ drastically from the behavior demonstrated by graphite/Li cell, soft carbon/Na cell and pure Na metal plating.