Sodium-ion battery, the beginning of a new era

A few months ago, a team of researchers from the RS2E network presented their first prototype sodium-ion battery. To understand the progress that this technology represents, you need to know the context of rechargeable batteries used for mobile applications.

The battery market is now booming and is dominated by lithium-ion batteries. Lithium, in low abundance on Earth (33eme most abundant element, 20mg/kg in the Earth’s crust), is one of the essential elements of these storage systems. The largest mined deposits are limited to a few countries in South America (Chile, Bolivia, Argentina) or Asia (China). It is this low number of producers that fears supply irregularities and therefore places lithium as a medium criticality resource. As the available reserves are estimated to be several tens of millions of tonnes, compared with an extraction between 33 000 and 38 000 tonnes annually (36 000t in 2014), the shortage is not envisaged in the long term (several centuries of supply).

For some years now the development of sodium-ion batteries has become an objective of research laboratories specializing in rechargeable batteries. Sodium is a much more abundant element than lithium (the 6th most abundant element, 23 600mg/kg in the Earth’s crust) and much more accessible. The first sodium reservoir is seawater which contains about 10G/kg, which can be exploited by many countries.

Thus, the realization of a prototype of the format “18650” (standard format used for Li-ion batteries) by the team of RS2E, constitutes a major step forward towards an industrialization of these batteries. With an energy density of 90 Wh/kg, equivalent to the first Li-ion batteries placed on the market, (half less than the last generation at 200 Wh/kg), and a lifespan exceeding 2000 load/discharge cycles, this prototype presents promising characteristics. An improved energy density that can make na-ion batteries even more competitive.

Although sodium-ion technology cannot compete with Li-ion batteries in the mobile phone and Tablet market, it can be fully envisaged as a replacement for Li-ion in electric cars, or as mass storage of intermittent renewable energies (solar, wind,…), two markets in full expansion.

Bibliography

CNRS journal

■ BRGM report, 2011 lithium market panorama

■ CGSP working paper, no. 2013-04, July, “critical metal supply”