Abstract
Finding an adapted negative electrode for Na-ion batteries (NIB) is one of the critical issues for their successful development. The field of anode materials for NIB is also the one where most differences are found when compared to lithium-ion batteries. Contrary to lithium-based systems, graphite does not intercalate sodium ions with conventional electrolytes, and the alternative carbonaceous negative electrode materials that have been proposed, such as hard carbon, are characterized by relatively low specific capacities up to 300 mAh g–1 and undergo substantial irreversible capacity during the first sodiation. The materials are divided based on their reaction mechanism as insertion, alloying or conversion materials. The insertion materials include transition metal oxides, sodium titanate, lithium titanate and layered titanates. An interesting approach to obtain electrode materials from renewable resources with minimum energy consumption is using them as organic electrode materials.