We need a battery in Europe that is durable, safe, high-performance and cheap. 

The search for an alternative to conventional lithium-ion batteries remains a top priority that is being supported by the European Horizon 2020 programme. We need a battery in Europe that is durable, safe, high-performance and cheap. This is why the Naiades project involving ten partners was launched in 2015 for the purpose of developing a durable sodium-ion battery. This project entered its final stage in 2018.

High-performing, reliable and safe

Developing a battery is one thing, but making it high-performing, reliable and safe is quite another. An effective battery management system (BMS) is needed to do this, and VITO/EnergyVille was charged with developing it. The new sodium-ion battery was developed by different project partners and installed in a smart substation of an electricity grid north of Barcelona by a distribution grid operator. The battery module itself was supplied to researchers at VITO in late November 2018, and the system needed to be tested by as early as mid-December in order to be built in. The BMS software was adapted to the new technology, and safety functions, such as alarm signals, were introduced. For example, the system not only monitors voltages and currents, but also temperature and, over a longer period, cell capacities.  VITO was able to meet the deadline perfectly, because the entire BMS can be monitored and adjusted remotely. The grid services are ensured in the substation by a lithium-ion battery, while the new sodium-ion battery is being used as a back-up for the supporting services such as telecommunications and automation.

How much power? 

Most of the attention is now being devoted to safety. As the technology, and therefore also its production, is not yet fully developed, there are variations in capacity and general performance between the different cells. Cell voltages when charging and discharging the cells must be the same. VITO also ensures that these voltages remain within safe limits and are balanced. An additional challenge exists in providing an accurate state-of-charge estimate: determining how much charge a battery has left and how much power it can still supply. In order to do this, a battery needs to be monitored for an extended period.

This project has already demonstrated the feasibility and potential of the sodium-ion battery as an alternative to lithium-ion batteries for particular applications.