Sodium Ion Batteries (also called SIBs, NIBs, or Na-ion batteries) are rechargeable batteries that are similar in their operating principle (‘rocking chair’ design) to Lithium Ion Batteries (LIB) but employ different materials in their construction. Outwardly, SIB and LIB cells have the same form factor (cylindrical, prismatic, pouch) and structure (coated electrodes, electrolyte, tabs). SIBs have the advantages of being made from cheaper, widely available materials1 , and — depending on the cathode chemistry — potentially also being safer than LIBs2 including the LFP chemistry, the most common LIB chemistry for BESS. SIBs are intermediate in energy density between LIBs and the traditional lead acid batteries, which are still widely used in backup battery and consumer market applications for their low price. The wider expectation is for SIB to substitute for LIB in low end EVs, e-bikes, and potentially BESS, where energy density can be traded off for price