Sodium-ion battery
Sodium-ion batteries (NIBs or SIBs) are several  types of rechargeable batteries, which use sodium ions (Na+) as its charge carriers. In some cases, its working principle and cell construction are similar to those of lithium-ion battery (LIB) types, but it replaces lithium with sodium as the cathode material, which belongs to the same group in the periodic table as lithium and thus has similar chemical properties. In other cases, aqueous Na-ion batteries are quite different from Li-ion batteries. SIBs received academic and commercial interest in the 2010s and 2020s, largely due to the uneven geographic distribution, high environmental impact, and high cost of many of the materials required for lithium-ion batteries. An obvious advantage of sodium is its natural abundance, particularly in saltwater. No less important is the fact that cobalt, copper and nickel are not required for many types of sodium-ion batteries, and more abundant iron-based materials work well in Na+ batteries, even though they are not suitable for Li+ batteries. This difference is due to the larger ionic radius of Na+ compared to Li+, which prevents place-exchange between the alkali metal and the transition metal ions. At the same time, the larger ionic radius of Na+ results in a slower movement of this ion inside crystal lattices. For example, the exchange of Na+ in NaFeSO4F is orders of magnitude slower than that of Li+ in LiFeSO4F, even though both crystals have the same tavorite structure. Other challenges to the adoption of SIBs include lower energy density and short  cycle life. Electric vehicles using sodium-ion battery packs are not yet commercially available. However, CATL, the world's biggest battery manufacturer, announced in 2022 the start of mass production of SIBs. In February 2023, the Chinese HiNa Battery Technology Co., Ltd. placed a 140 Wh/kg sodium-ion battery in an electric test car for the first time, and energy storage manufacturer Pylontech obtained the first sodium-ion battery certificate from TÜV Rheinland. 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. Operating principle 
SIB cells consist of a cathode based on a sodium-based material, an anode (not necessarily a sodium-based material) 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 (a potential plateau) below ⁓0.15 V vs Na/Na+. Graphite anodes for LIBs offer typical capacities of 300–360 mAh/g. 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, (lower) working potentials, and cycling stability. 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 – 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 
Graphene Janus particles 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(AsC5) mono/bilayer has been explored as an anode material due to high specific gravity (794/596mAh/g), low expansion(1.2%), and ultra low diffusion barrier (0.16/0.09eV), indicating rapid charge/discharge cycle capability, during sodium intercalation. After sodium adsorption, a carbon arsenide anode maintains structural stability at 300K, indication 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 (NiSb) 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. Tin 
In another 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 electrolyte at 1 mA cm−2 with 1 mA h cm−2 and the full cell exhibited a steady cycling rate of 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. Oxides 
Some sodium titanate phases such as Na2Ti3O7, or NaTiO2, delivered capacities around 90–180 mAh/g at low working potentials (< 1 V vs Na/Na+), though cycling stability was limited to a few hundred cycles. Molybdenum disulphide 
In 2021 researchers from China tried layered structure  as a new type of anode for sodium-ion batteries. A dissolution-recrystallization process densely assembled carbon layer-coated MoS2 nanosheets onto the surface of polyimide-derived N-doped carbon nanotubes. This kind of C-MoS2/NCNTs anode can store 348 mAh/g at 2 A/g, with a cycling stability of 82% capacity after 400 cycles at 1 A/g. TiS2 is another potential material for SIBs because of its layered structure, but has yet to overcome the problem of capacity fade, since TiS2 suffers from poor electrochemical kinetics and relatively weak structural stability. In 2021 researchers from Ningbo, China employed pre-potassiated TiS2, presenting rate capability of 165.9mAh/g and a cycling stability of 85.3% capacity after 500 cycles. Other anodes for Na+ 
Some other materials, such as mercury, electroactive polymers have also been demonstrated in laboratories, but did not  provoke commercial interest. Cathodes

Oxides 
Sodium-ion cathodes store sodium via intercalation. Owing to their high tap density, high operating potentials and high capacities, cathodes based on sodium transition metal oxides have received the greatest attention. To keep costs low, research attempts to minimize costly elements such as Co, Cr, Ni or V. A P2-type Na2/3Fe1/2Mn1/2O2 oxide from earth-abundant Fe and Mn resources can reversibly store 190 mAh/g at average discharge voltage of 2.75 V vs Na/Na+ utilising the Fe3+/4+ redox couple – on par or better than commercial lithium-ion cathodes such as LiFePO4 or LiMn2O4. However, its sodium deficient nature lowered energy density. Significant efforts were expended in developing Na-richer oxides. A mixed P3/P2/O3-type Na0.76Mn0.5Ni0.3Fe0.1Mg0.1O2 was demonstrated to deliver 140 mAh/g at an average discharge voltage of 3.2 V vs Na/Na+ in 2015. In particular, the O3-type NaNi1/4Na1/6Mn2/12Ti4/12Sn1/12O2 oxide can deliver 160 mAh/g at average voltage of 3.22 V vs Na/Na+, while a series of doped Ni-based oxides of the stoichiometry NaaNi(1−x−y−z)MnxMgyTizO2 can deliver 157 mAh/g in a sodium-ion “full cell” with a hard carbon anode at average discharge voltage of 3.2 V utilising the Ni2+/4+ redox couple. Such performance in full cell configuration is better or on par with commercial lithium-ion systems. A Na0.67Mn1−xMgxO2 cathode material exhibited a discharge capacity of 175 mAh/g for Na0.67Mn0.95Mg0.05O2. This cathode contained only abundant elements. Copper-substituted Na0.67Ni0.3−xCuxMn0.7O2 cathode materials showed a high reversible capacity with better capacity retention. In contrast to the copper-free Na0.67Ni0.3−xCuxMn0.7O2 electrode, the as-prepared Cu-substituted cathodes deliver better sodium storage. However, cathodes with Cu are more expensive. Oxoanions 
Research has also considered cathodes based on oxoanions. Such cathodes offer lower tap density, lowering energy density than oxides. On the other hand, a stronger covalent bonding of the polyanion positively impacts cycle life and safety and increases the cell voltage. Among polyanion-based cathodes, sodium vanadium phosphate and fluorophosphate have demonstrated excellent cycling stability and in the latter, an acceptably high capacity (⁓120 mAh/g) at high average discharge voltages (⁓3.6 V vs Na/Na+). Besides that, sodium manganese silicate has also been demonstrated to deliver a very high capacity (>200 mAh/g) with decent cycling stability. A French startup TIAMAT develops Na+ ion batteries based on a sodium-vanadium-phosphate-fluoride cathode material Na3V2(PO4)2F3, which undergoes two reversible 0.5 e-/V transitions: at 3.2V and at 4.0 V. A startup from Singapore, SgNaPlus is developing and commercialising Na3V2(PO4)3 cathode material, which shows very good cycling stability, utilising the non-flammable glyme-based electrolyte. Prussian blue and analogues 
Several reports discussed the use of various Prussian blue and Prussian blue analogues (PBAs), with the patented rhombohedral Na2MnFe(CN)6 displaying 150–160 mAh/g in capacity and a 3.4 V average discharge voltage and rhombohedral Prussian white Na1.88(5)Fe[Fe(CN)6]·0.18(9)H2O displaying initial capacity of 158 mAh/g and retaining 90% capacity after 50 cycles. Electrolytes 
Sodium-ion batteries can use aqueous and non-aqueous electrolytes. The limited electrochemical stability window of water results in lower voltages and limited energy densities. Non-aqueous carbonate ester polar aprotic solvents extend the voltage range. These include ethylene carbonate, dimethyl carbonate, diethyl carbonate, and propylene carbonate. The most widely used salts in non-aqueous electrolytes are NaClO4  and sodium hexafluorophosphate (NaPF6) dissolved in a mixture of these solvents. It is a well-established fact that these carbonate-based electrolytes are flammable, which pose safety concerns in large-scale applications. A type of glyme-based electrolyte, with sodium tetrafluoroborate as the salt is demonstrated to be non-flammable. In addition, NaTFSI (TFSI = bis(trifluoromethane)sulfonimide) and NaFSI (FSI = bis(fluorosulfonyl)imide, NaDFOB (DFOB = difluoro(oxalato)borate) and NaBOB (bis(oxalato)borate) anions have emerged lately as new interesting salts. Of course, electrolyte additives can be used as well to improve the performance metrics. Comparison 
Sodium-ion batteries have several advantages over competing battery technologies. Compared to lithium-ion batteries, sodium-ion batteries have somewhat lower cost, better safety characteristics, and similar power delivery characteristics, but also a lower energy density. The table below compares how NIBs in general fare against the two established rechargeable battery technologies in the market currently: the lithium-ion battery and the rechargeable lead–acid battery. Commercialization 
Companies around the world have been working to develop commercially viable sodium-ion batteries. A 2-hour 5MW/10MWh grid battery was installed in China in 2023. Active

Faradion Limited 
Faradion Limited, is a subsidiary of India's Reliance Industries. Its cell design uses oxide cathodes with hard carbon anode and a liquid electrolyte. Their pouch cells have energy densities comparable to commercial Li-ion batteries (160 Wh/kg at cell-level) with good rate performance till 3C and cycle lives of 300 (100% depth of discharge) to over 1,000 cycles (80% depth of discharge). Its battery packs have demonstrated use for e-bike and e-scooter applications. They demonstrated transporting sodium-ion cells in the shorted state (at 0 V), eliminating risks from commercial transport of such cells. It is partnering with AMTE Power plc (formerly known as AGM Batteries Limited). In November 2019, Faradion co-authored a report with Bridge India titled ’The Future of Clean Transportation: Sodium-ion Batteries’ looking at the growing role India can play in manufacturing sodium-ion batteries. On December 5, 2022, Faradion installed its first sodium-ion battery for Nation in New South Wales Australia

TIAMAT 
TIAMAT spun off from the CNRS/CEA and a H2020 EU-project called NAIADES. Its technology focuses on the development of 18650-format cylindrical cells based on polyanionic materials. It achieved energy density between 100 Wh/kg to 120 Wh/kg. The technology targets applications in the fast charge and discharge markets. Power density is between 2 and 5 kW/kg, allowing for a 5 min charging time. Lifetime is 5000+ cycles to 80% of capacity. HiNA Battery Technology Company 
HiNa Battery Technology Co., Ltd is, a spin-off from the Chinese Academy of Sciences (CAS). It leverages research conducted by Prof. Hu Yong-sheng's group at the Institute of Physics at CAS. HiNa's batteries are based on Na-Fe-Mn-Cu based oxide cathodes and anthracite-based carbon anode. In 2023, HiNa partnered with JAC as the first company to put a sodium-ion battery in an electric car, the Sehol E10X. HiNa also revealed three sodium-ion products, the NaCR32140-ME12 cylindrical cell, the NaCP50160118-ME80 square cell and the NaCP73174207-ME240 square cell, with gravimetric energy densities of 140 Wh/kg, 145 Wh/kg and 155 Wh/kg respectively. In 2019, it was reported that HiNa installed a 100 kWh sodium-ion battery power bank in East China. Natron Energy 
Natron Energy, a spin-off from Stanford University, uses Prussian blue analogues for both cathode and anode with an aqueous electrolyte. Altris AB 
Altris AB was founded by Associate Professor Reza Younesi, his former PhD student, Ronnie Mogensen, and Associate Professor William Brant as a spin-off from Uppsala University, Sweden. The company was launched in 2017 as part of research efforts from the team on sodium-ion batteries. The research was conducted at the Ångström Advanced Battery Centre led by Prof. Kristina Edström at Uppsala University. The company offers a proprietary iron-based Prussian blue analogue for the positive electrode in non-aqueous sodium-ion batteries that use hard carbon as the anode. Altris holds patents on non-flammable fluorine-free electrolytes consisting of NaBOB in alkyl-phosphate solvents, Prussian white cathode, and cell production. CATL 
Chinese battery manufacturer CATL announced in 2021 that it would bring a sodium-ion based battery to market by 2023. It uses Prussian blue analogue for the positive electrode and porous carbon for the negative electrode. They claimed a specific energy density of 160 Wh/kg in their first generation battery. The company planned to produce a hybrid battery pack that includes both sodium-ion and lithium-ion cells. Defunct

Aquion Energy 
Aquion Energy was (between 2008 and 2017) a spin-off from Carnegie Mellon University. Their batteries (salt water battery) were based on sodium titanium phosphate anode, manganese dioxide cathode, and aqueous sodium perchlorate electrolyte. After receiving government and private loans, the company filed for bankruptcy in 2017. Its assets were sold to a Chinese manufacturer Juline-Titans, who abandoned most of Aquion's patents. See also 
 List of battery types
 Alkali metal-ion battery
 Lithium-ion battery
 Sodium-ion battery
 Potassium-ion battery
 Calcium-ion battery
 Rechargeable battery
 Salt water battery

Notes

References

External links 
 
 

Metal-ion batteries
Battery types