Focus: Sodium-ion Batteries

In my opinion, sodium-ion batteries represent an important energy storage alternative to conventional lithium-ion technology. Based on initial data these batteries should offer similar electrochemical characteristics to their lithium counterparts. In addition, they may provide some significant performance advantages such as: lower material costs and improved safety performance. These properties will be particularly important in future large format uses such as automotive (EV/PHEV) and stationary applications.

Based on these facts it is somewhat surprising that so little research effort has been dedicated to the commercial development of these energy storage systems. Part of the problem is the identification of suitable Na insertion anode materials. Unfortunately, graphite (the preferred negative electrode materials in Li-ion cells) does not allow significant Na ion uptake. Recent work, however has demonstrated significant amounts of sodium may be reversible cycled in disordered, hard carbon hosts. This has allowed the creation of some novel sodium-ion chemistries.

For instance, we recently reported the preliminary performance characteristics of the Hard Carbon//NaVPO4F cell. The abstract to the work may be found here:

Barker et al; A Sodium-ion Cell based on the Fluorophosphate Compound NaVPO4F

Further details on this, and other polyanion based sodium-ion cells may be found here:

Barker et al; US Patent #6872492

Jerry