Sodium-ion batteries
Sodium-ion batteries replace lithium with sodium, a far more abundant element. They promise lower material cost and are often reported to handle low temperatures well, but public long-term ageing data for automotive use is limited and lifetime models are experimental.
How sodium-ion differs
Sodium-ion cells work on the same principle as lithium-ion cells: ions shuttle between two electrodes during charge and discharge. Sodium ions are larger than lithium ions and do not fit well into graphite, so sodium-ion cells typically use a hard carbon anode. Cathode candidates include layered oxides, polyanion compounds and Prussian blue analogues.
The main attractions are abundant raw materials, potentially lower cost and less dependence on lithium, nickel and cobalt. The main drawback is a lower energy density than most current lithium-ion chemistries.
What is known about ageing
Reviews of sodium-ion research describe degradation mechanisms that partly mirror lithium-ion, such as interphase formation on the anode, alongside chemistry-specific issues like structural changes in some cathode materials. Much of the research concerns lab-scale cells and relatively short test durations.
How sodium-ion packs age over many years under real driving, charging and climate conditions is not yet well documented in public peer-reviewed sources. Relationships that are well established for lithium-ion, such as the SOC and temperature dependence of calendar ageing, may behave differently.
Why Voltgevity treats it as experimental
Reviews of EV degradation models stress that a model's reliability depends on the data it is built on. For sodium-ion that data is thin, and cell designs are still evolving quickly. Voltgevity therefore labels sodium-ion predictions as experimental, uses generic assumptions rather than chemistry-specific fitted parameters, and shows wide uncertainty ranges.
These estimates are best read as rough orientation, not as a forecast. They will be revisited as more automotive data is published.
Key takeaways
- Sodium-ion uses abundant materials and typically a hard carbon anode instead of graphite.
- Energy density is lower than that of most current lithium-ion chemistries.
- Public long-term automotive ageing data is limited, so lifetime models are experimental.
- Voltgevity shows sodium-ion predictions with wide uncertainty, as orientation only.