Sodium-ion battery
A sodium-ion battery is a rechargeable battery that uses sodium ions as charge carriers. In some cases, its working principle and cell construction are similar to those of lithium-ion battery types, simply replacing lithium with sodium as the intercalating ion. Sodium belongs to the same group in the periodic table as lithium and thus has similar chemical properties. However, designs such as aqueous batteries are quite different from LIBs.
SIBs received academic and commercial interest in the 2010s and early 2020s, largely due to lithium's high cost, uneven geographic distribution, and environmentally damaging extraction process. Unlike lithium, sodium is abundant, particularly in saltwater. Further, cobalt, copper, and nickel are not required for many types of sodium-ion batteries, and abundant iron-based materials work well in
The development of batteries started in the 1990s. Companies such as HiNa and CATL in China, [|Faradion] in the United Kingdom, Tiamat in France, Northvolt in Sweden, and Natron Energy in the US, claimed to be close to commercialization, employing sodium layered transition metal oxides, Prussian white or vanadium phosphate as cathode materials.
Sodium-ion accumulators are operational for fixed electrical grid storage, and vehicles with sodium-ion battery packs are commercially available for light scooters made by Yadea, which use HuaYu sodium-ion battery technology.
History
Sodium-ion battery development took place in the 1970s and early 1980s. However, by the 1990s, lithium-ion batteries had demonstrated more commercial promise, causing interest in sodium-ion batteries to decline. In the early 2010s, sodium-ion batteries experienced a resurgence, driven largely by the increasing cost of lithium-ion battery raw materials. Also, the number of patent families reached the number of non-patent publication after ca. 2020, which usually signify the fact that the technology reached the commercialization stage.Operating principle
SIB cells consist of a cathode based on a sodium-based material, an anode and a liquid electrolyte containing dissociated sodium salts in polar protic or aprotic solvents. During charging, sodium ions move from the cathode to the anode while electrons travel through the external circuit. During discharge, the reverse process occurs.Materials
Due to the physical and electrochemical properties of sodium, SIBs require different materials from those used for LIBs.Anodes
Carbons
SIBs can use hard carbon, a disordered carbon material consisting of a non-graphitizable, non-crystalline and amorphous carbon. Hard carbon's ability to absorb sodium was discovered in 2000. This anode was shown to deliver 300 mAh/g with a sloping potential profile above ~0.15 V vs Na/Na+. It accounts for roughly half of the capacity and a flat potential profile below ~0.15 V vs Na/Na+. Such capacities are comparable to 300–360 mAh/g of graphite anodes in lithium-ion batteries. The first sodium-ion cell using hard carbon was demonstrated in 2003 and showed a 3.7 V average voltage during discharge. Hard carbon was the preferred choice of Faradion due to its excellent combination of capacity, working potentials, and cycling stability. Notably, nitrogen-doped hard carbons display even larger specific capacity of 520 mAh/g at 20 mA/g with stability over 1000 cycles.Recent advances in hard carbon anodes
Recent studies have focused on modifying the microstructure and surface chemistry of hard carbon to improve its performance as an anode material for sodium-ion batteries. Hard carbon stores sodium through a combination of adsorption on defect sites, intercalation between turbostratic graphene layers, and filling of nanopores with sodium clusters. Its electrochemical behavior depends on the arrangement of pseudo-graphitic domains and the distribution of open and closed pores within the carbon matrix.To achieve high capacity and fast-charging performance, researchers have explored structural engineering approaches such as enlarging the interlayer distance and tuning the pore structure. Nitrogen doping and pore activation have been shown to increase interlayer spacing and create additional active sites for sodium storage, which improves rate capability and reversibility. Control over the size and volume fraction of closed pores affects sodium cluster formation, influencing the low-potential plateau capacity and cycling stability.
Biomass-derived hard carbon with optimized pseudo-graphitic domains and tailored closed pores has been reported to reach a reversible capacity of 280 mAh/g at 1 A/g, retaining over 90% of its capacity after 1000 cycles. These findings indicate that microstructural design and heteroatom doping are effective strategies for improving the performance of hard carbon anodes in sodium-ion batteries.
In 2015, researchers demonstrated that graphite could co-intercalate sodium in ether-based electrolytes. Low capacities around 100 mAh/g were obtained with relatively high working potentials between 0 and 1.2 V vs Na/Na+.
One drawback of carbonaceous materials is that, because their intercalation potentials are fairly negative, they are limited to non-aqueous systems.
Graphene
have been used in experimental sodium-ion batteries to increase energy density. One side provides interaction sites while the other provides inter-layer separation. Energy density reached 337 mAh/g.Carbon arsenide
Carbon arsenide mono/bilayer has been explored as an anode material due to high specific capacity, low expansion, and ultra low diffusion barrier, indicating rapid charge/discharge cycle capability, during sodium intercalation. After sodium adsorption, a carbon arsenide anode maintains structural stability at 300 K, indicating long cycle life.Metal alloys
Numerous reports described anode materials storing sodium via alloy reaction and/or conversion reaction. Alloying sodium metal brings the benefits of regulating sodium-ion transport and shielding the accumulation of electric field at the tip of sodium dendrites. Wang, et al. reported that a self-regulating alloy interface of nickel antimony was chemically deposited on Na metal during discharge. This thin layer of NiSb regulates the uniform electrochemical plating of Na metal, lowering overpotential and offering dendrite-free plating/stripping of Na metal over 100 h at a high areal capacity of 10 mAh cm−2.Metals
Many metals and semi-metals form stable alloys with sodium at room temperature. Unfortunately, the formation of such alloys is usually accompanied by a large volume change, which in turn results in the pulverization of the material after a few cycles. For example, with tin sodium forms an alloy, which is equivalent to 847 mAh/g specific capacity, with a resulting enormous volume change up to 420%.In one study, Li et al. prepared sodium and metallic tin /Na through a spontaneous reaction. This anode could operate at a high temperature of in a carbonate solvent at 1 mA/cm2 with 1 mAh/cm2 loading, and the full cell exhibited a stable charge-discharge cycling for 100 cycles at a current density of 2C.. Despite sodium alloy's ability to operate at extreme temperatures and regulate dendritic growth, the severe stress-strain experienced on the material in the course of repeated storage cycles limits cycling stability, especially in large-format cells.
Researchers from Tokyo University of Science achieved 478 mAh/g with nano-sized magnesium particles, announced in December 2020.
In 2024, Dalhousie University researchers enhanced sodium-ion battery performance by replacing hard carbon in the negative electrode with lead and single wall carbon nanotubes. This combination significantly increased volumetric energy density and eliminated capacity fade in half cells. SWCNTs endured active material connectivity, boosting capacity to 475 mAh/g and reducing losses, compared to 430 mAh/g in Pb cell without SWCNTs.