Why Sodium-Ion Batteries are Necessary

When I showed up for work at Tesla nearly ten years ago, it was in a gas-burning 1999 Volvo. I parked it alongside a mosaic of Priuses, Foresters and Volts. While the dream of affordable electric cars propelled us, few if any of the engineers working at Tesla were able to afford the $100,000 cars we designed and built.

Fast forward, and the industry's relentless innovation has slashed the cost of electric vehicles dramatically. As of 2024, fifteen EVs in the United States are priced below $40,000 after federal incentives, and many of these vehicles have ranges on par with the 2013 Model S.

Yet despite technological improvements, recent DOE data shows that out of 281 million cars registered nationally, battery-electric vehicles represent only 0.8%. Nearly nine out of ten passenger vehicles sold in 2023 were still powered by combustion engines.

The crux of consumer hesitation is cost. Electric vehicles remain more expensive than their gasoline-powered counterparts, often by as much as $20,000. Even when consumers reap savings in long-term fuel and maintenance costs, today's high interest rates make electric vehicles unaffordable for many. Market surveys show that annual income is one of the strongest predictors of electric vehicle uptake.

If we want the masses to adopt electric vehicles, the inescapable conclusion is that we must reduce their cost.

Attacking the Source of Cost

The most expensive component in an electric vehicle is its high voltage battery, which weighs around 1,000 pounds and costs anywhere between $5,000 and $20,000. While the past decade has seen extraordinary improvements in battery costs (falling by 82% over ten years), improvements have reached a plateau.

This dramatic cost reduction was based on improvements which are largely now spent: economies of scale, physically larger battery cells, more efficient equipment, and less wasteful packaging. Now, manufacturers face battery costs largely driven by raw materials. In addition to establishing a stubborn cost floor, this injects volatility and uncertainty.

For example: between January 2021 and November 2022, the cost of lithium carbonate surged by more than 12 times. Over that same interval, nickel prices rose by nearly 60%. Battery costs, which had been falling for ten years, increased. EV sale prices surged to a record of $66,997, nearly 34% higher than in 2021.

In response to metals shortages, automakers moved their offerings upmarket, introducing models like the $150,000 Mercedes-AMG EQS and $170,000 Lucid Air Dream Edition. One year later, metals prices collapsed, and these premium products were put on firesale. Major automakers like Ford lost nearly $5 billion in one year. Determined not to make the same mistake twice, legacy automakers retreated to the seemingly safer realm of hybrid-electric vehicles.

This status quo is unsustainable for drivers, automakers, and the planet. If we want customers to drive electric vehicles, automakers must be able to consistently produce high numbers of them at a low cost.

Enter Sodium-Ion 

Around the same time lithium-ion batteries were invented, so too were sodium-ion. Based on the exact same operating principle and manufacturing technology, sodium-ion batteries were shown to deliver ~75% of the performance of lithium-ion, but without many of the latter's scarce and expensive metals.

Yet at the time of lithium-ion's commercialization, there was no reason to ever seriously consider using a sodium-ion battery. In 1991, battery metals were cheap and costs were dominated by manufacturing. Battery designs were inefficient, requiring high-grade materials to yield even moderate performance. And crucially, early markets in consumer electronics prioritized energy density over cost. All of these trends worked in favor of lithium-ion, leaving sodium-ion development by the wayside.

The tables are turned in 2024. Today, materials dominate the cost of a battery, at around 70%. Cost is now a more important parameter than ever. And battery designs, both at the cell and pack level, have become far more efficient. This gives lower-performing materials a chance to compete for market share.

Trends in the underlying applications have also reduced the importance of performance. For example, a Tesla Model S which drained 351 watt-hours per mile in 2013 now uses a mere 281 to travel the same distance due to improved motors, drive electronics, and aerodynamics. Fast chargers have also become ubiquitous in many markets and now replenish charge 300% faster than before, mitigating the need for long range.

These reasons and others are why Chinese companies launched their first electric cars powered by sodium-ion batteries this year. Unlike virtually every other hyped battery technology of the past decade, sodium-ion has crossed the chasm and is here to stay.

It's Not About Energy Density

Many industry analysts scoff at the idea of lower energy density batteries for electric vehicles. After all, isn't range anxiety a core barrier to adoption, making sodium-ion counterproductive?

This dilemma stems from the mistaken idea that energy density is the key determinant of today's EV range. In reality, EV range is often not limited by battery energy density, but by cost. Indeed, one of the core projects from my time at Tesla resulted in the 75 kWh battery pack for Model S, which emptied out cells from the battery pack to offer a lower MSRP. In this vehicle, the only pathway to a longer range was to reduce the cost of battery cells.

While volumetric energy density certainly has a role to play in premium products, automakers are constantly coming up with ways to engineer vehicles around ever bulkier battery packs, realizing that it's cheaper to build cars around big, low-cost batteries than smaller ones based on expensive minerals.

And while battery weight is often touted as a concern, the difference in weight between a sodium-ion and lithium-ion powered electric vehicle comes out to about the weight of a passenger. While this has a modest impact on vehicle cost, the impact on range is negligible.

Today, the energy density of the battery cells used in the Tesla Model 3 is about 30% lower than what was used in the Model S in 2013. The trend of reducing energy density in the name of cost savings is likely to continue.

A Roadmap to Take Sodium Parabolic

Today's sodium-ion batteries deliver around 70% of the energy density of a lithium-iron phosphate battery, the cheapest and lowest performing lithium chemistry used today. Yet sodium is nowhere near its physical limits. Work is only just beginning to optimize the composition and structure of sodium-ion electrode materials.

 While sodium-ion will never be competitive for niche performance applications like sports cars or aircraft, it is on a performance roadmap that we believe intersects with lithium-iron phosphate sometime in the next decade. When this happens, a profound market shakeup is likely to occur, with sodium-ion displacing lithium-ion in some of the most important mass market applications.

Reducing the Cost of Energy Storage

Ten years ago, my inspiration to work at Tesla was to create battery-powered vehicles so exciting that everyone would want to own them. Now, I believe it's time to make sure everyone can. Sodium ion is the clear pathway to accomplish this goal, and as one of the only venture-backed companies in the United States working to industrialize the sodium-ion supply chain, Bedrock Materials has a unique opportunity to see that it will.

And if you're a battery scientist looking for an opportunity to contribute to this cutting-edge work, we'd love for you to join us on that journey.