Prospects in anode materials for sodium ion batteries - A review

With the rapid expansion in energy demands and depletion of fossil fuel reservoirs, the importance of clean energy production and storage has increased drastically. The renewable energy recourses are cost effective, sustainable and carbon dioxide emission free alternatives. Nevertheless, this energy is not always available and needs to be stored. Lithium ion batteries (LIBs) are rapidly used in various applications such as powering electronics, electric vehicles and grid energy storage. However, the increasing concerns regarding load leveling of renewable energy and rise in cost of LIBs due to limited availability of lithium reserves arises doubts whether LIBs alone can meet the rising demands for mid-to-large-scale energy storage. Therefore, attention has been shifted towards development of sodium ion batteries (SIBs) which have wide reserves and low precursor cost and thus is considered as appropriate choice for solar and wind energy development. The prime problem encountered in development of large-scale SIBs is the low effectiveness of appropriate anode material because of large size and sluggish kinetics of Na ions. A comprehensive study regarding anode materials is reported focusing on storage mechanism and structural changes involved during storage of Na ions in various classes of anode materials including carbon-based materials, conversion, conversion/alloying and organic materials. A brief overview of various components of SIBs such as cathode, electrolyte and separator are also discussed.