State-of-the-Art Na-Ion Batteries: Electrolyte Approach to Address the Issues of Cycle-Life

With a worldwide trend towards the efficient use of renewable energies, the electricity supply sector has a pressing need for inexpensive energy storage. Sodium-ion batteries (NIBs) are an emerging battery technology with promising cost, safety, sustainability, and performance advantages over current commercialized lithium-ion batteries. Therefore, NIBs are attractive prospects for stationary storage application (utility scale and behind-the-meter), and transportation applications where energy density is less critical, and lifetime operational cost is the overriding factor. Sodium-ion batteries have similar architecture/construction as state-of-the-art Li-ion batteries and can be a drop-in to the existing manufacturing infrastructure. The abundance of sodium alleviates some of the critical materials supply chains issues associated with lithium. Gravimetric energy densities are reported in the range of 100-200 Wh/kg making them a potential complementary/substitutional technology to lithium iron phosphate-based batteries. Sodium-ion batteries operate in a similar temperature regime as lithium-ion technologies but can be shipped uncharged (0% state of charge) for improved safety. However, before commercializing NIBs, R&D activities must be focusing on cost reduce by: (1) improving technical performance (increasing cycle life and energy density); (2) Establishing supply chains; (3) achieving economies of scales. Recently, some commercialization efforts have been demonstrating in pouch cells, 18650 cells, and/or modules showing very promising data, such as: Natron (US/Prussian blue), Faradion (UK/Layered Oxide), TIAMAT(FR/polyanionic), CATL (CN/Layered Oxide), and HiNa (CN/Layered Oxide). Improving the lifespan as well as energy density of the NIB is one of main targets to support for the deployment if NIBs at scale in various market. In PNNL, we have been developing some advanced electrolytes which are nonflammable and help to resolve the issue of battery cycle life through enhancing/stabilizing the interfacial reaction and preventing the materials failure during long-term operation. In addition, the fundamental aspects and deep exploring on reaction kinetic helps to unveiling the mysteries of the battery degradation and operation failure.