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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 3 - NAIADES (Na-Ion bAttery Demonstration for Electric Storage)

Teaser

Summary

Wide scale implementation of renewable energy will require growth in production of inexpensive, efficient energy storage systems. The extension of battery technology to large-scale storage will become necessary as intermittent renewable energy sources such as wind, solar and wave become more prevalent and integrated into electrical grid. Lithium-ion battery appears as quite mature for this application but its cost per mWh remains high in comparison to high temperature technology such as Zebra, which integrate low cost sodium base materials. Furthermore, as the use of large format lithium battery becomes widespread; increase demand for lithium commodity chemicals combined with geographically constrained Li mineral reserves will drive up prices. Based on the wide availability and low cost of sodium, ambient temperature sodium-based batteries have the potential for meeting large scale grid energy storage needs. In NAIADES, the objective is to demonstrate the feasibility of ambient temperature Na-ion battery from the knowledge and achievement that has been done at the laboratory scale, up to a module demonstration in a realistic application environment. Several European industries, research institutes and universities decided to join their efforts to assess the Na-ion technology for stationary storage application through building a 1 kW modules system Na-ion cell which will serve as data base to demonstrate economical and public acceptance.These module prototypes will be developed to meet performances in a 1kW system in a cost-effective, sustainable and environmental-friendly manner. New energy policy will be developed to integer the Na-ion battery in the Smart Grid initiative and promote the penetration of renewable energy in the electric network.

Work performed

Two different positive materials have been investigated in this project; a polyanionic cathode and a layered oxide. Polyanion presents a very high average discharge voltage; however, its theoretical capacity is quite modest. It presents also very good cycling behaviour and power rate capability. Layered oxide presents one of the highest theoretical capacity, >200 mAh/g, but the average voltage is rather low, and the rate capability and cycling behaviour are both poor. For the negative electrode, hard carbon was selected. This material was prepared from different precursors at laboratory scale in order to improve first cycle reversibility. Commercial materials have been also benchmarked. The best lab synthesis method has been identified for scale up, and the best commercial material has been chosen for cells and modules development. In terms of scale up, 1 kg batches have been produced of the polyanion with good electrochemical performance. For hard carbon, the first batches have been also produced, but a very high irreversible capacity is observed due to synthesis temperature conditions. Besides, the first 84070 type pouch cells of 1 Ah capacity have been produced in order to perform preliminary tests before producing the larger cells (10 Ah) to be implemented in the module. From this point of view, electrodes have been realised using the 1 kg batches of cathode produced and the selected commercial hard carbon. They show good capacity and good rate capability. Cycling tests are in progress. For the module the preferred specification will be a 12s2p, 12 cells in series and 2 in parallel, setup of 10 Ah cells. This will lead to a total energy content of 960 Wh. The nominal voltage of the battery in the application will be 48 V, leading to a nominal cell voltage of 4 V in this setup. Note that the cells have a maximum cell voltage of 4.33 V. The module design will be based on an existing cell block design. A battery management system, BMS, is also being developed in order to manage and integrate the battery into the final system.

Final results

The main expected impact of this project is the following: an enlarged energy storage portfolio, an increased efficiency of the storage technologies, and a facilitated electric energy management in the grid. So far, as this project is focused on the long term evolution of the electric grid, it is still difficult to provide specific final evidence of the impact. However, some significant results can already give promising answers. First of all, the manufacturing of the first 1 Ah cells have already proven the feasibility of this technology, and from this point of view, it seems very likely that this battery technology will be available soon on the market. However, it must first meet the requirements of specific applications in terms of performance, cost and safety. This is one of the purposes of the test plan of the NAIADES project. Secondly, preliminary results show encouraging values in terms of environmental impact of this material along all its life. Finally, the Integration of this storage tehcnnolgy into the management of the distribution grids to provide increased grid security and stability, will be evaluated during the last year of NAIADES, when the module will be integrated in a smart secondary substation as a backup power source.