Lithium-ion vs. Sodium-ion

Just a real quick write-up going over the technical differences and some common misconceptions of sodium-ion.

I received a question about sodium-ion on a note I did about Tesla’s possible recycling facility in Australia, and figured I would just create a short post since to give a proper answer far exceeds the limited character count that a reply has.

What do you think would the role be of sodium batteries if they ever get into electric cars manufacturing?

Sodium-ion batteries are already used in select EV models in China, including hybrid setups that pair sodium-ion with lithium-ion instead of engine-battery hybrids.

But without writing a research paper, let’s just look at a basic comparison between sodium-ion and lithium-ion:

Technical Comparison

Sodium-ion has a much lower energy density, requiring about twice the space and number of cells compared to lithium-ion to store the same amount of energy. CATL has announced they are working on a second generation of sodium-ion batteries that is more in lines with the energy density of today’s LFP cells, but that is the energy density of current LFP cells—not what lithium-ion standards will be when this new sodium-ion generation is deployed.

While sodium-ion can recharge faster, its round-trip efficiency—the percentage of energy retained after a full charge-discharge cycle—is around 85–92%, compared to lithium-ion’s 90–98%. Lithium-ion also has a flatter power curve, with response times between 50–300 milliseconds during frequency shifts, while sodium-ion usually reacts in 100–500 milliseconds.

Environmental Considerations

The environmental cost of hard carbon anodes in sodium-ion batteries is often ignored. Making hard carbon requires high-temperature pyrolysis, over 1000°C, of biomass or petroleum-based feedstocks. This process uses a lot of energy and can lead to high CO₂ emissions if fossil fuels are involved. Sodium-ion batteries also have shorter life cycles than lithium-ion, typically lasting 2,000–6,000 charge-discharge cycles, often trailing lithium-ion’s 6,000–10,000 cycles though this varies dependent on the cathode chemistry. That lower durability means more frequent replacements, which adds to the environmental burden from repeated hard carbon production and limited recycling infrastructure. Recycling hard carbon is possible, but without standard methods and broader adoption, it only adds to the problem.

Geopolitical and Innovation

Two points rarely mentioned deserve attention. First, China controls about 80% of the patents related to sodium-ion batteries and is also the primary developer and provider of the manufacturing and processing technology needed to produce these cells. This limits global adoption and will make other countries largely dependent on them.

Second, although sodium-ion research receives millions in funding, lithium-ion attracts considerable more in investments. This supports developments like manganese-rich cathodes that are turning LFP into a more stable and efficient chemistry—advancements not reliant on China. Both Ford and GM are working on manganese-rich cathodes intended to replace basic LFP within the next decade. In my view, we’ll likely see these cells long before a true all-solid-state battery (ASSB) becomes a reality—but that’s a topic for another article.

Advantages and Market Applications

Sodium-ion batteries do offer a few advantages, but their current cost per kWh, averaging $70–100 in China due to limited production capacity, exceeds that of LFP, which has dropped to $53–60/kWh in China and $70–80/kWh in Europe and North America, thanks to the basics of economies of scale and manufacturing maturity. Projections suggest sodium-ion costs could fall to $50/kWh by 2030, potentially undercutting LFP, though lithium-ion’s established infrastructure and ongoing innovations even with the recovery of the price of battery metals will most likely keep both paralleling each other in price.

One clear and current advantage, however, is that sodium-ion batteries are considerably more stable than lithium-ion batteries. In thermal runaway triggered by a short circuit, both battery types react in similar fashions by releasing various gases. For both, carbon dioxide (CO₂) forms when carbonate solvents in the electrolyte break down or react with oxygen from the cathode at high temperatures. Carbon monoxide (CO) emerges from incomplete combustion or the decomposition of carbon-containing materials, such as the electrolyte or anode, in oxygen-limited conditions.

Hydrogen (H₂) is generated in both, hydrocarbons like methane (CH₄), ethylene (C₂H₄), and ethane (C₂H₆) also are produced, resulting from the decomposition of electrolyte solvents under high heat and electrical stress. However, unlike lithium-ion batteries, which produce hydrogen fluoride (HF), a highly toxic and corrosive gas, from the decomposition of lithium salts like lithium hexafluorophosphate (LiPF₆) sodium-ion batteries avoid the creation of the his gas. This is a clear advantage over LFP which will produce more HF than even NMC.

Moreover Lithium-ion cells, particularly NMC cathodes, also release larger volumes of flammable CH₄, C₂H₄, and C₂H₆, amplifying fire hazards. In contrast, sodium-ion batteries tend to produce a less intense gas mixture, with lower volumes of flammable components.

Sodium-ion also performs better in extreme temperatures. In cold conditions, below 0°C, sodium-ion retains 70–80% capacity, outpacing lithium-ion’s 50–60% drop, which also at these temperatures for lithium-ion there is a greater risk of lithium metal plating on the anode. When lithium ions deposit as metal on the anode due to poor intercalation conditions, dendrites are created. These needle-like growths expand over charge-discharge cycles and can eventually lead to the cell shorting out. At high heat, sodium-ion has greater thermal stability, with runaway typically delayed past 150°C and a slower self-heating rate. Lithium-ion, especially NMC cells, can spike to 600°C, with higher fire and gas cloud explosions risk due to elevated levels of flammable hydrocarbons.

Why Sodium Than?

Sodium-ion was pitched as a fix for supposed lithium shortages, but lithium is abundant. The issue is a processing bottleneck and manipulation by China using stockpiling and control over the processing of raw materials. There’s also the narrative that lithium mining is especially destructive. While that’s not technically false—no mining is “green”—newer technology developed and deployed over the last five years is on track to bring emissions below 1 kg of CO₂ per kWh of storage. I broke that down in Is Lithium Really That Dirty if you want to dig into the numbers.

And that’s without even touching lithium-ion recycling, where even CATL says they may not need to mine lithium and other battery metals at all in a few decades. This is a serious possibility when it comes to cobalt. As for the other metals and even graphite, a significant percentage could be sourced from end-of-life batteries.

Robin Zeng Yuqun, founder of Contemporary Amperex Technology Ltd (CATL), said this during a panel at the World Economic Forum in 2024:

By 2042, China will no longer need to mine new mineral materials because of its mature battery recycling market.

Conclusion

Sodium-ion is better seen as a chemistry developed to support China’s hold on the secondary battery market. These batteries will likely find use in grid storage, but for AI and data centers, lithium-ion’s higher efficiency and faster response times will keep it the standard. Other chemistries like zinc or vanadium offer a more long-term potential for basic grid storage without relying on Chinese technology or production.

Despite potential future cost reductions and safety advantages, sodium-ion faces practical limits when competing with lithium-ion for mainstream EV use. Its lower energy density, shorter life cycles, and less efficient energy retention will confine it to niche roles where range and performance aren’t priorities. Grid storage for renewables, where size is less critical, and budget EVs like China’s BYD Seagull may be its primary applications. Meanwhile, lithium-ion continues to improve — Ford and GM are developing manganese-rich cathodes, and both primary and secondary sources using nest generation technologies for lithium and other battery metals are being developed and deployed throughout the world.

Disclaimer: This article is intended solely for educational purposes only and should not be construed as investment advice, a solicitation to buy or sell securities, or a recommendation of any investment strategy. The author has not received compensation from any companies mentioned and is not responsible for decisions made based on this information. Readers are encouraged to consult primary sources and professional advisors before making investment decisions.