Sodium ion batteries for stationary applications in challenging environment

The SIBERIA project is a Young Talent Researcher project which seeks to develop and demonstrate fluorine-free Sodium ion batteries (SIBs) suitable for application in challenging environments. In times of rising energy demand, stationary storage of produced energy becomes paramount for the energy transition. Secondary batteries are a key enabling technology for stationary storage. SIBs can be thought of as an analogue of the widely used Lithium ion batteries, which use Sodium rather than Lithium as the basis of the energy storage reactions. Being greatly more abundant than Lithium, the use of Sodium reduces cost and mitigates supply issues due to geopolitical difficulties, making SIBs a very attractive technology for stationary storage in particular. The SIBERIA project will focus initially on the development of new electrolytes which maintain performance across a broad range of temperatures (-20 to +60 °C), in order to function in Nordic climates ideally without the need of thermal battery management, and thus enable cheap and easy roll out of storage solutions tailored for colder environments. In line with the drive to reduce usage of “Forever chemicals” these will utilise novel fluorine free salts developed through the project. In the second stage of development, fundamental studies will investigate the compatibility of these electrolytes with environmentally benign commercially available active materials and guide the engineering of stable “interphases” at the electrode surfaces which enable long term performance. The project will conclude with the pilot scale production of entirely fluorine-free SIBs and their demonstration under Nordic operating conditions.

SIBERIA intends to develop completely fluorine free Na-ion batteries utilising benign iron based Prussian Blue Analogues (PBAs) as an alternative battery technology for stationary storage. Central to the concept is that good performance at low temperatures can minimise or even eliminate the need for active thermal management. Combined with aqueous processing and fluorine-free constituents, this minimises the environmental impact at all lifecycle stages. The project will initially screen PBAs from different suppliers, determine their suitability for aqueous processing and adapt recipes to suit. Concurrently anode materials based on hard carbon and titania will be evaluated similarly. Binders such as CMC and PAA will be applied in place of PVDF. As some components (especially PBAs) have a strong affinity for water, a key goal is to develop processes which enable cell assembly in a conventional dry room rather than a glovebox environment. The core of the project is the development of entirely novel electrolytes based on mixtures of different solvent classes (such as nitriles, ethers, esters, carbonates) with fluorine-free weakly coordinating sodium salts such as carboxyl diacid chelates of phosphorus or boron centres, and cyano substituted Hückel anions based on imidazole moieties. These salts will in large part be synthesised within the project, owing to their commercial non-availability. The electrolytes thus developed will be comprehensively assessed for their electrochemical performance and compatibility with the chosen electrode chemistries not only at room temperature, but also at sub ambient temperatures down to -20 °C. The project will conclude with demonstration and full characterisation of long cycle life cells operating according to charge discharge profiles appropriate to stationary storage applications in Nordic type environments, and the efficacy of the concept will be determined via an LCA performed alongside the experimental work.