A sodium-ion battery stores energy the same way a lithium-ion battery does: it moves ions back and forth between two host electrodes. The difference is that it uses sodium, an element roughly 400 times more abundant than lithium. Sodium-ion cells currently store less energy per kilogram than lithium-ion cells. CATL rates its Naxtra cell, which it calls the highest-energy sodium-ion battery, at 175 Wh/kg (a manufacturer figure), which makes sodium-ion a lower-cost, cold-tolerant complement to lithium-ion rather than a replacement for it.

• Sodium makes up about 2.83% of Earth's crust versus 0.0065% for lithium. Sodium cells can also use cheap aluminum foil on the anode instead of copper (Hwang et al., 2017).
• There are three main cathode families: layered sodium transition-metal oxides, polyanion compounds such as Na3V2(PO4)3, and Prussian blue analogues, including Prussian white.
• Graphite, the standard lithium-ion anode, stores almost no sodium. Hard carbon, at roughly 300 mAh/g, is the standard sodium-ion anode.
• Sodium-ion cells are now commercial. CATL announced a 160 Wh/kg first-generation cell in 2021 and its Naxtra cell in 2025, and it has a passenger-car program with Changan.
• According to the IEA (2025), sodium-ion needs either higher energy density or higher lithium prices to beat LFP on cost per kWh. The IEA also sees a possible cost advantage in cold climates.

How does a sodium-ion battery work?

A sodium-ion cell is an intercalation, or "rocking-chair," battery. During charging, Na+ ions leave the crystal lattice of the cathode, travel through a liquid electrolyte, and insert into the anode. On discharge the ions flow back while electrons pass through the external circuit. Sodium's intercalation chemistry is similar enough to lithium's that many of the same compound types work for both. Researchers have also tested sodium-ion cell assembly on existing lithium-ion manufacturing infrastructure.

The current collectors are one practical difference. Lithium alloys with aluminum at the low potentials an anode reaches, so lithium-ion anodes need copper foil. Sodium does not alloy with aluminum in this way, so a sodium-ion cell can use aluminum on both electrodes. Aluminum is cheaper and lighter than copper.

Why do sodium-ion batteries have lower energy density than lithium-ion?

Three basic properties work against sodium. The Na+ ion is larger (1.02 Å versus 0.76 Å for six-coordinate Li+). Sodium is heavier, at 23 g/mol versus 6.9 g/mol. Its standard electrode potential is less negative (−2.71 V versus −3.04 V against the standard hydrogen electrode), so a sodium cell built on the same cathode chemistry runs at a lower voltage. The same review argues that capacity is set mainly by the host electrode structures, so in principle the heavier ion carries only a modest energy penalty. In practice, though, the larger ion causes bigger lattice strain and slower diffusion during cycling (Xie et al., 2020).

The penalty shows up at the cell level. CATL described its 160 Wh/kg first-generation sodium-ion cell as having slightly lower energy density than current LFP batteries. Lithium iron phosphate (LFP) is itself the lower-energy-density lithium-ion chemistry. For how LFP compares with nickel-rich cathodes, see our LFP vs NMC comparison.

What are the main sodium-ion cathode materials?

Layered sodium transition-metal oxides

Layered oxides, NaxMO2 where M is a transition metal, are the sodium counterparts of lithium cobalt and nickel oxides. They are classified by where sodium sits between the MO2 sheets. In O3 types it occupies octahedral sites, and in P2 types it occupies prismatic sites, a scheme introduced by Delmas and coworkers. These oxides can be built from iron and manganese. A 2012 study showed that P2-Na2/3[Fe1/2Mn1/2]O2, made only from Earth-abundant transition metals, delivers 190 mAh/g of reversible capacity. The main drawbacks are complex phase transitions during cycling and sensitivity to air: sodiated layered oxides are highly hygroscopic. Simple end-members studied in this family include NaFeO2, NaMnO2, and NaNiO2.

Polyanion cathodes

Polyanion cathodes use tetrahedral groups such as PO4 to build stiff three-dimensional frameworks. The best-known example is the NASICON-type compound Na3V2(PO4)3, or NVP. It offers a theoretical capacity of about 117.6 mAh/g on a stable plateau near 3.4 V and a modest volume change of about 8%, but its electronic conductivity is poor. Iron phosphate shows how much polymorphs matter. The thermodynamically stable form of NaFePO4 is maricite, not the olivine structure used in LFP, and maricite was long regarded as electrochemically inactive. A 2015 study found that nanosized maricite delivered 142 mAh/g after converting to amorphous FePO4 during the first charge.

Prussian blue analogues and Prussian white

Prussian blue analogues (PBAs) are metal hexacyanometallates. Their open cubic or rhombohedral frameworks have large channels for Na+. Prussian white is the sodium-rich, fully reduced form. A 2015 study reported an air-stable rhombohedral Na1.92Fe[Fe(CN)6]. Its dehydrated, sodium-rich form makes it possible to build cells without a sodium-metal anode. CATL's first commercial cell used a Prussian white cathode and a porous hard-carbon anode, and the company said both its Prussian white and layered-oxide cathodes reach 160 mAh/g.

Why do sodium-ion batteries use hard carbon instead of graphite?

Graphite stores lithium as LiC6, with a theoretical capacity of 372 mAh/g. Sodium forms only dilute graphite compounds such as NaC64, which are worth about 35 mAh/g in conventional carbonate electrolytes. Ion size alone does not explain this, because the even larger K+ ion intercalates readily. The same review cites van der Waals DFT calculations showing that NaC6 and NaC8 have positive formation enthalpies, so they are thermodynamically unfavorable.

Hard carbon is non-graphitizing carbon, made by pyrolyzing precursors such as sugars, biomass, or resins. Its small, curved graphene domains and nanopores store sodium by adsorption, intercalation, and pore filling. Glucose-derived hard carbon reported in 2000 provided more than 300 mAh/g. Most biomass-derived hard carbons deliver up to about 300 mAh/g with an initial Coulombic efficiency below 85%. That first-cycle loss matters in a full cell, because sodium consumed in forming the anode's solid-electrolyte interphase comes out of the cathode's inventory.

Sodium-ion vs lithium-ion: how do they compare?

Are sodium-ion batteries commercially available?

Yes, although volumes are still small compared with lithium-ion. In July 2021, CATL launched a first-generation cell that it said reached 160 Wh/kg, charged to 80% in 15 minutes at room temperature, and kept more than 90% of capacity at −20 °C, and said its thermal stability exceeds China's national safety requirements for traction batteries. It also announced an "AB" pack design that combines sodium-ion and lithium-ion cells in one pack. In April 2025, CATL announced its Naxtra cell, claiming 175 Wh/kg, more than 10,000 cycles, and operation from −40 °C to 70 °C, along with a 24 V start-stop battery for heavy trucks. In February 2026, CATL and Changan unveiled what they call the world's first mass-production sodium-ion passenger vehicle, with a stated pure-electric range above 400 km and a market launch planned for mid-2026. The "first" label is the companies' own; the IEA notes that the 2022 surge of interest had already led to the first EVs using sodium-ion batteries. All of these are manufacturer figures, not independent test results.

The IEA describes a boom-and-bust pattern. Interest in sodium-ion surged in 2022 as lithium prices rose, then waxed and waned through 2023 and 2024 amid supply-chain challenges and falling lithium prices. BYD has since invested in sodium-ion production, and HiNa launched an improved cell in March 2025. The same analysis concludes that sodium-ion will need higher energy density or higher lithium prices to compete with LFP on cost per kWh. It also notes that sodium-ion may be a cheaper option for cold climates, where LFP performs less well.

What does sodium-ion change for the battery supply chain?

Lithium prices are the main reason sodium-ion is attractive. USGS data show the annual average price of battery-grade lithium carbonate (in inflation-adjusted dollars) went from $71,100 per metric ton in 2022 to an estimated $14,000 in 2024. Batteries accounted for an estimated 87% of global lithium use. World mine output outside the United States was about 240,000 tons of lithium content in 2024, led by Australia, Chile, and China. The IEA identifies sodium-ion as one innovation that could reduce the risk of a future lithium shortage and avoid price spikes like the one in 2022.

Sodium supply is a far smaller concern. Common sodium sources include soda ash, and the USGS puts U.S. soda ash reserves alone at about 23 billion tons. The anode side changes as well. Hard carbon replaces graphite, and the USGS estimates that China produced 78% of the world's graphite in 2024, so switching anodes removes dependence on that particular supply chain. Iron- and manganese-based cathodes such as Prussian white and Fe/Mn layered oxides avoid cobalt and nickel entirely. Hard-carbon precursors and processing remain an open scale-up issue. Most reported biomass-derived hard carbons still cost more than graphite and soft carbons.

Frequently asked questions

Is a sodium-ion battery better than lithium-ion?

It is better on some measures and worse on others. Sodium-ion uses more abundant materials and performs well in the cold, but it stores less energy per kilogram. The IEA sees it as competitive with LFP mainly when lithium prices are high or in cold climates.

Do sodium-ion batteries contain lithium?

A sodium-ion cell does not need lithium in its electrodes or electrolyte salt. Some packs, such as CATL's "AB" design, deliberately combine sodium-ion and lithium-ion cells.

Why can't sodium-ion batteries use graphite anodes?

Sodium-rich graphite compounds are thermodynamically unfavorable, so graphite holds only about 35 mAh/g of sodium in standard electrolytes. Disordered hard carbon is used instead.

What is Prussian white?

Prussian white is the sodium-rich, reduced form of iron hexacyanoferrate, a Prussian blue analogue with an open framework for Na+ transport. CATL used it as the cathode of its first-generation cell.

Are sodium-ion batteries safer than lithium-ion?

Manufacturers report good thermal stability. CATL says the thermal stability of its first-generation cell exceeds China's national safety requirements for traction batteries. However, most sodium-ion cells still use flammable organic electrolytes, so safety depends on the specific cell design and testing rather than on the chemistry alone.

How long do sodium-ion batteries last?

CATL claims more than 10,000 cycles for its Naxtra cell. Independent long-term field data are still limited, so treat such figures as manufacturer specifications.

Explore sodium-ion materials on LatticeGraph

Browse the layered sodium oxides, Prussian blue analogues, and vanadium phosphate cathodes classes. Compound pages such as NaFePO4 show computed (DFT) structures, polymorph stability, and band gaps alongside literature synthesis recipes. Our sodium layered oxides analysis and note on DFT database disagreement explain how to read those values.