Sodium ion battery: A promising energy-storage candidate for supporting renewable electricity

Sodium ion battery was initially researched alongside lithium ion battery in the late 1970s and through the 1980s. For the benefits of lithium ion batteries, namely higher energy density as a result of higher potential and lower molecular mass, shifted the focus of the battery community away from sodium. While lithium-ion battery technology is quite mature, there remain questions regarding lithium ion battery safety, lifetime, poor low-temperature performance, and cost. Furthermore, the rising demand for Li would force us to consider the growing price of Li resources due to the relative low abundance and uneven distribution of Li. Therefore, to explore low cost, highly safe, and cycling stable rechargeable batteries based on abundant resources is an urgent task. Due to the huge availability of sodium, its low price and the similarity of both Li and Na insertion chemistries, sodium-based batteries have the potential for meeting large scale grid energy storage needs. In spite of the lower energy density and voltage of Na-ion based technologies, they can be focused on applications where the energy density requirement is less drastic, such as electrical grid storage. In the past couple of years, the sodium-ion battery field presented lots of sodium-ion technologies and electrode materials. These range from layered oxides materials to polyanionbased materials, carbons and other insertion materials for sodium-ion batteries, many of which hold promise for future sodium-based energy storage applications. Much work has to be done in the field of Na-ion in order to catch up with Li-ion technology. Cathodic and anodic materials must be optimized, and new electrolytes will be the key point for Na-ion success. This review will gather the up-to-date knowledge about Na-ion battery electrode materials and electrolyte, with the aim of providing a wide view of the system that has already been explored and a starting point for the new research on this battery technology.