(Invited) Cost Is King: An Industrial Perspective on Sodium-Ion Batteries

Sodium-ion batteries promise lofty benefits over lithium-ion batteries: more affordable batteries made from abundant materials, better rate performance, temperature stability, and safety, all for a small penalty of battery size and weight. Better still, much of a sodium-ion battery’s manufacturing uses existing infrastructure due to the similarities between lithium and sodium-ion batteries. However, quantification of sodium-ion costs at the cell and pack level reveals substantial costs associated with their typically-low volumetric energy density. The present work explores the nuances of quantifying battery costs by comparing several sodium-ion battery chemistries against the incumbent LFP || Graphite technology. Starting from the materials level, sodium is substantially more abundant in the earth than lithium, and there is a stable and advanced market for sodium outside of the battery field, resulting in minimal price fluctuations. Furthermore, most of the materials for a sodium-ion battery do not require foreign trade, thereby reducing tariff costs. By examining the tariff and price fluctuations of sodium and lithium materials from the last 10 years, it is possible to project future cost scenarios. At the cell level, volumetric energy density of the cathode and anode play a critical role in the final cost/kWh of the battery. Lower volumetric energy density results in higher cell packaging and manufacturing costs. The present work details the relative cost of materials compared to cell packaging and construction under different material cost scenarios, including the cost savings from substituting the copper current collector to aluminum. At the pack level, costs associated with lower volumetric energy density are compounded as additional components and processing are added per pack. On the other hand, a safer sodium-ion battery with higher onset of thermal runaway and lower heat generation or otherwise lower risk of adverse events will reduce the cost of the safety or thermal management systems necessary per pack. Finally, battery cost comparisons must consider cycle life and rate performance of the cell to compare battery lifetime costs and price per power costs. Effective comparisons between lithium and sodium-ion chemistries must match as many cell construction and testing variables as possible to achieve a final cost/lifetime energy and cost/power metric. For the sake of a fair comparison, any unique material or cell advances made for a sodium-ion battery must also be considered feasible for an LFP || Graphite cell unless fundamental chemistry principles suggest otherwise. By quantifying the various costs of a sodium-ion battery, the requisite innovations required to out-compete LFP || Graphite become more apparent.