Deployment of micro-grids using renewable energy (solar and wind power) requires large-scale electrical energy storage (EES) systems. Currently, lithium-ion batteries (LIBs) are leading candidates for EES. High power density LIBs addressing intermittency of renewables use expensive lithium titanate as anode. Besides, lithium is a scarce resource. Sodium, on the other hand, is the sixth most abundant element on the Earth’s crust. Sodium-ion batteries (NIBs) operating at ambient temperature are expected to be durable, safe and inexpensive. Regardless of the relatively lower energy density of NIBs, they can effectively be employed in micro-grid applications, where the weight and footprint requirement are not severe.
We present here recently developed non-flammable sodium-ion conducting glyme based electrolyte displaying excellent storage performance of low voltage anodes as well as high voltage cathodes for sodium-ion cells. Employing this liquid electrolyte, non-flammable sodium-ion cells (18650-type) have been fabricated using rhombohedral Prussian Blue analogoue1 or sodium vanadium phosphate as cathode and hard carbon as anode with energy density in the range 40 – 60 Wh/kg (kg refers to the total 18650 full cell weight) and impressive 4C rate performance. This ultra-safe commercial type sodium-ion cells have relatively higher energy density than the reported aqueous (non-flammable) commercial NIBs. We further present thermal (DSC analyses) and safety parameters (heat losses and internal resistance evaluations) of the above 18650 cells which help in developing thermal management systems for NIB packs for possible micro-grids (100-500 kWh) to address the intermittency of renewable energy.
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