IN SUMMARY
Sodium-ion batteries (SIBs) are attracting attention as a possible answer to lithium scarcity and price volatility. Sodium makes up 23,600 ppm of the earth’s crust against just 20 ppm for lithium, and sodium hydroxide costs a fraction of lithium hydroxide. But abundance and low cost do not automatically translate into a lower environmental footprint. Minviro assessed five sodium-ion chemistries against lithium-ion NMC and LFP using life cycle assessment, looking beyond climate change to resource use and acidification, to test whether the “sustainable by default” assumption holds.
Abundance does not equal sustainability. Sodium-ion batteries do not consistently outperform lithium-ion on climate change. Their footprint depends heavily on the specific cathode chemistry, with cobalt-containing and Prussian blue variants performing worst.
Chemistry is everything. Cobalt-free layered oxide sodium-ion cells perform comparably to LFP, while cobalt and polyanionic chemistries exceed both LFP and NMC. The electrolyte (NaPF6) and cathode are the dominant contributors.
Cycle life changes the comparison. Measured over a usable lifetime rather than a single kWh, sodium-ion and LFP cells, which can cycle 2,000 times or more, tend to carry lower impacts than NMC, which cycles fewer times.
Why sodium-ion is gaining attention
Sodium-ion and lithium-ion cells share the same basic structure, but SIBs use a sodium-based cathode in place of a lithium one. The appeal is straightforward: sodium is one of the most abundant elements in the earth’s crust, and sodium precursors are far cheaper than their lithium equivalents, with sodium hydroxide around 900 USD per tonne against roughly 75,000 USD per tonne for lithium hydroxide in early 2023. Companies including CATL, BYD, HiNa, Faradion and Natron Energy are developing the technology, initially for stationary storage and increasingly for smaller electric vehicles. Importantly, incoming battery regulations are agnostic to chemistry, so sodium-ion will face the same carbon footprint scrutiny as lithium-ion, which makes understanding its true impact essential rather than optional.
How the study was built
Minviro used a cradle-to-gate LCA, covering raw material extraction through to cell manufacturing, with a functional unit of one kilowatt-hour of contained cell storage capacity. Five sodium-ion cathode chemistries with hard carbon anodes were assessed: three layered transition metal oxides (two cobalt-free, one with cobalt), one Prussian blue analogue, and one polyanionic compound. These were compared against the two most commercialised lithium-ion chemistries, NMC-622 and LFP. Background data came from Minviro’s internal raw material database alongside Ecoinvent 3.9, using the Environmental Footprint 3.1 method. Because public data on sodium-ion at commercial scale is limited, the study acknowledges lower confidence in the sodium-ion background data than the lithium-ion equivalents.