Stanford group designs room temperature sodium metal anode with good long term cycling capability

The recent run-up in lithium prices underscores the uncertainty about the long term relation between lithium production levels and lithium price. Sodium, which is the next heavier metal in the alkali metal family is abundant and cheap compared to lithium so that the development of sodium metal battery anodes has the potential to improve the long term economic outlook for battery based energy storage.

Of course high temperature liquid sodium anodes are already in use in NGK insulators sodium sulfur (NaS) batteries. This battery technology received a serious setback in 2011 when a battery fire broke out in an energy storage facility owned by the Tokyo Electric Power Company. However, NGK has rebounded from this incident and has redesigned their batteries with a higher safety margin. They recently announced the start of operations of a 300 MWh battery facility built for Mitsubishi Electric Corporation. They also have contracts to build battery facilities in Italy and in the UAE both of which will exceed 300 MWh of energy storage capacity in their final configurations. Therefore sodium metal anodes already have some impressive energy storage achievements to their credit.

However, the solid ceramic electrolyte required for the operation of high temperature (325C) NaS batteries is expensive to manufacture. Room temperature batteries might be cheaper, plus they would open up to the door to mobility application for which the current high temperature batteries are considered inappropriate.

A research group in the Stanford University Department of Materials Science and Engineering recently published a paper paper in which they describe a room temperature sodium metal anode used with a liquid electrolyte which achieved highly reversible Na metal plating-stripping over 300 charge/discharge cycles. Of course thousands of cycles are required for real world applications and furthermore the other half of a room temperature NaS battery (the sulfur cathode) has its own set of problems which need to be solved in order to produce a commercially viable product. Prior to the publication of the Stanford paper more progress has actually been made towards designing a room temperature sulfur cathode than towards designing a sodium anode. This new research may open the door to a complete design for a room temperature NaS battery.