Type of rechargeable battery Sodium-ion batterySpecific energy0.27-0.72 MJ/kg (75&#;200 W·h/kg)Energy density250&#;375 W·h/LCycle durability"thousands"[1] of cyclesNominal cell voltage3.0-3.1 V

Sodium-ion batteries (NIBs, SIBs, or Na-ion batteries) are several types of rechargeable batteries, which use sodium ions (Na+) as their 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 intercalating ion. Sodium belongs to the same group in the periodic table as lithium and thus has similar chemical properties. However, in some cases, such as aqueous batteries, SIBs can be quite different from LIBs.

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SIBs received academic and commercial interest in the s and early s, largely due to lithium's high cost, uneven geographic distribution, and environmentally-damaging extraction process. An obvious advantage of sodium is its natural abundance,[2] particularly in saltwater. Another factor is that cobalt, copper and nickel are not required for many types of sodium-ion batteries, and more abundant iron-based materials (such as NaFeO2 with the Fe3+/Fe4+ redox pair)[3] work well in Na+ batteries. This is because the ionic radius of Na+ (116 pm) is substantially larger than that of Fe2+ and Fe3+ (69&#;92 pm depending on the spin state), whereas the ionic radius of Li+ is similar (90 pm). Similar ionic radii of lithium and iron result in their mixing in the cathode material during battery cycling, and a resultant loss of cyclable charge. A downside of the larger ionic radius of Na+ is a slower intercalation kinetics of sodium-ion electrode materials.[4]

The development of Na+ batteries started in the s. After three decades of development, NIBs are at a critical moment of commercialization. Several companies such as HiNa and CATL in China, Faradion in the United Kingdom, Tiamat in France, Northvolt in Sweden,[5] and Natron Energy in the US, are close to achieving the commercialization of NIBs, with the aim of employing sodium layered transition metal oxides (NaxTMO2), Prussian white (a Prussian blue analogue[6]) or vanadium phosphate as cathode materials.[improper synthesis?][7][8][9][10][11][12][13]

Sodium-ion accumulators are operational for fixed electrical grid storage, but vehicles using sodium-ion battery packs are not yet commercially available. However, CATL, the world's biggest lithium-ion battery manufacturer, announced in the start of mass production of SIBs. In February , the Chinese HiNA Battery Technology Company, Ltd. placed a 140 Wh/kg sodium-ion battery in an electric test car for the first time,[14] and energy storage manufacturer Pylontech obtained the first sodium-ion battery certificate[clarification needed] from TÜV Rheinland.[15]

History

[edit]

Sodium-ion battery development took place in the s and early s. However, by the s, lithium-ion batteries had demonstrated more commercial promise, causing interest in sodium-ion batteries to decline.[16][17] In the early s, sodium-ion batteries experienced a resurgence, driven largely by the increasing cost of lithium-ion battery raw materials.[16] Also, the number of patent families reached the number of non-patent publication after ca. , which usually signify the fact that the technology reached the commercialization stage.

Operating principle

[edit]

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.[citation needed]

Materials

[edit]

Due to the physical and electrochemical properties of sodium, SIBs require different materials from those used for LIBs.[18]

Anodes

[edit]

Carbons

[edit]

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 .[19] 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+. 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 and showed a 3.7 V average voltage during discharge.[20] Hard carbon was the preferred choice of Faradion due to its excellent combination of capacity, (lower) working potentials, and cycling stability.[21] Notably, nitrogen-doped hard carbons display even larger specific capacity of 520 mAh/g at 20 mA/g with stability over cycles.[22]

In , 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+.[23]

One drawback of carbonaceous materials is that, because their intercalation potentials are fairly negative, they are limited to non-aqueous systems.

Graphene

[edit]

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.[24]

Carbon arsenide

[edit]

Carbon arsenide (AsC5) mono/bilayer has been explored as an anode material due to high specific gravity (794/596 mAh/g), low expansion (1.2%), and ultra low diffusion barrier (0.16/0.09 eV), indicating rapid charge/discharge cycle capability, during sodium intercalation.[25] After sodium adsorption, a carbon arsenide anode maintains structural stability at 300 K, indicating long cycle life.

Metal alloys

[edit]

Numerous reports described anode materials storing sodium via alloy reaction and/or conversion reaction.[16] Alloying sodium metal brings the benefits of regulating sodium-ion transport and shielding the accumulation of electric field at the tip of sodium dendrites.[26] 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.[27]

Metals

[edit]

Many metals and semi-metals (Pb, P, Sn, Ge, etc.) 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 (crumbling) of the material after a few cycles. For example, with tin sodium forms an alloy Na
15Sn
4, which is equivalent to 847 mAh/g specific capacity, with a resulting enormous volume change up to 420%.[28]

In one study, Li et al. prepared sodium and metallic tin Na
15Sn
4/Na through a spontaneous reaction.[citation needed] This anode could operate at a high temperature of 90 °C (194 °F) in a carbonate solvent at 1 mA cm&#;2 with 1 mA h cm&#;2 loading, and the full cell exhibited a stable charge-discharge cycling for 100 cycles at a current density of 2C.[citation needed] (2C means that full charge or discharge was achieved in 0.5 hour). 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 .[29]

In , Dalhousie University researchers enhanced sodium-ion battery performance by replacing hard carbon in the negative electrode with lead (Pb) and single wall carbon nanotubes (SWCNTs). 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.[30]

Oxides

[edit]

Some sodium titanate phases such as Na2Ti3O7,[31][32][33] or NaTiO2,[34] 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

[edit]

In , researchers from China tried layered structure MoS2 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.[35] 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 , 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.[36]

Other anodes for Na+

[edit]

Some other materials, such as mercury, electroactive polymers and sodium terephthalate derivatives,[37] have also been demonstrated in laboratories, but did not provoke commercial interest.[21]

Cathodes

[edit]

Oxides

[edit]

Many layered transition metal oxides can reversibly intercalate sodium ions upon reduction. These oxides typically have a higher tap density and a lower electronic resistivity, than other posode materials (such as phosphates). Due to a larger size of the Na+ ion (116 pm) compared to Li+ ion (90 pm), cation mixing between Na+ and first row transition metal ions (which is common in the case of Li+) usually does not occur. Thus, low-cost iron and manganese oxides can be used for Na-ion batteries, whereas Li-ion batteries require the use of more expensive cobalt and nickel oxides. The drawback of the larger size of Na+ ion is its slower intercalation kinetics compared to Li+ ion and the presence of multiple intercalation stages with different voltages and kinetic rates.[4]

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.[38] 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 .[39] 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+,[40] 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.[41] 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.[42] 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.[43]

Oxoanions

[edit]

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[44] and fluorophosphate[45] 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+).[46] Besides that, sodium manganese silicate has also been demonstrated to deliver a very high capacity (>200 mAh/g) with decent cycling stability.[47] 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.[48] A startup from Singapore, SgNaPlus is developing and commercialising Na3V2(PO4)2F3 cathode material, which shows very good cycling stability, utilising the non-flammable glyme-based electrolyte.[49]

Prussian blue and analogues

[edit]

Numerous research groups investigated the use of Prussian blue and various Prussian blue analogues (PBAs) as cathodes for Na+-ion batteries. The ideal formula for a discharged material is Na2M[Fe(CN)6], and it corresponds to the theoretical capacity of ca. 170 mAh/g, which is equally split between two one-electron voltage plateaus. Such high specific charges are rarely observed only in PBA samples with a low number of structural defects.

For example, the patented rhombohedral Na2MnFe(CN)6 displaying 150&#;160 mAh/g in capacity and a 3.4 V average discharge voltage[50][51][52] 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.[53]

While Ti, Mn, Fe and Co PBAs show a two-electron electrochemistry, the Ni PBA shows only one-electron (Ni is not electrochemically active in the accessible voltage range). Iron-free PBA Na2MnII[MnII(CN)6] is also known. It has a fairly large reversible capacity of 209 mAh/g at C/5, but its voltage is unfortunately low (1.8 V versus Na+/Na).[54]

Electrolytes

[edit]

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.[55] 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.[56]

Comparison

[edit]

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 (for the aqueous versions), and similar power delivery characteristics, but also a lower energy density (especially the aqueous versions).[57]

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.[41][58]

Battery comparison Sodium-ion battery Lithium-ion battery Lead&#;acid battery Cost per kilowatt-hour of capacity $40&#;77 (theoretical in )[59] $137 (average in )[60] $100&#;300[61] Volumetric energy density 250&#;375 W·h/L, based on prototypes[2] 200&#;683 W·h/L[62] 80&#;90 W·h/L[63] Gravimetric energy density (specific energy) 75&#;200 W·h/kg, based on prototypes and product announcements[2][64][65] Low end for aqueous, high end for carbon batteries[57] 120&#;260 W·h/kg (without protective case needed for battery pack in vehicle)[62] 35&#;40 Wh/kg[63] Power-to-weight ratio ~ W/kg[66] ~340-420 W/kg (NMC),[66] ~175-425 W/kg (LFP)[66] 180 W/kg

[67]

Cycles at 80% depth of discharge[a] Hundreds to thousands[1] 3,500[61] 900[61] Safety Low risk for aqueous batteries, high risk for Na in carbon batteries[57] High risk[b] Moderate risk Materials Abundant Scarce and toxic Abundant and toxic Cycling stability High (negligible self-discharge)[citation needed] High (negligible self-discharge) [citation needed] Moderate (high self-discharge)[68] Direct current round-trip efficiency up to 92%[1] 85&#;95%[69] 70&#;90%[70] Temperature range[c] &#;20 °C to 60 °C[1] Acceptable:&#;20 °C to 60 °C.

Optimal: 15 °C to 35 °C[71]

&#;20 °C to 60 °C[72]

Commercialization

[edit]

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 .[73]

Electric vehicles

[edit]

Farasis Energy&#;s JMEV EV3 (Youth Edition) sets a new standard as the world's first serial-production A00-class electric vehicle equipped with sodium batteries (sodium-ion batteries), offering a range of 251 kilometres (156 mi).[74]

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Dongfeng revealed the Nammi 01 electric vehicle, which Dongfeng claimed features a sodium solid state battery at a launch event.[75][better source needed]

Active

[edit]

Altris AB

[edit]

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,[76] launched in 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.[77] Altris holds patents on non-flammable fluorine-free electrolytes consisting of NaBOB in alkyl-phosphate solvents, Prussian white cathode, and cell production. Clarios is partnering to produce batteries using Altris technology.[78]

BYD

[edit]

The BYD Company is a Chinese electric vehicle manufacturer and battery manufacturer. In , they invested $1.4B USD into the construction of a sodium-ion battery plant in Xuzhou with an annual output of 30 GWh.[79]

CATL

[edit]

Chinese battery manufacturer CATL announced in that it would bring a sodium-ion based battery to market by .[80] 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.[64]

In , CATL unveiled the Freevoy hybrid chemistry battery pack for use in hybrid vehicles with a mix of sodium ion and lithium ion cells. This battery pack features an expected range of over 400 kilometres (250 mi), 4C fast charging capability, the ability to be discharged at &#;40 °C (&#;40 °F), and no difference to the driving experience at &#;20 °C (&#;4 °F). By , around 30 different hybrid vehicle models are expected to be equipped with this pack.[81]

On November 18th , CATL announced its second generation sodium-ion battery to be released in and reach mass market by . The battery is expected to be able to be discharged normally at temperatures of &#;40 °C (&#;40 °F). [82]

Faradion Limited

[edit]

Faradion Limited is a subsidiary of India's Reliance Industries.[83] 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 up to 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.[41] They demonstrated transporting sodium-ion cells in the shorted state (at 0 V), eliminating risks from commercial transport of such cells.[84] It is partnering with AMTE Power plc[85] (formerly known as AGM Batteries Limited).[86][87][88][89]

In November , Faradion co-authored a report with Bridge India[90] titled 'The Future of Clean Transportation: Sodium-ion Batteries'[91] looking at the growing role India can play in manufacturing sodium-ion batteries.

On December 5, , Faradion installed its first sodium-ion battery for Nation in New South Wales Australia.[92]

HiNA Battery Technology Company

[edit]

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 , 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 NaCR-ME12 cylindrical cell, the NaCP-ME80 square cell and the NaCP-ME240 square cell, with gravimetric energy densities of 140 Wh/kg, 145 Wh/kg and 155 Wh/kg respectively.[93] The cycle life of Hina's Battery was reported to by 4,500 cycles in . The company's goals were increasing specific energy to 180-200 Wh/kg and the cycle life to 8,000-10,000 cycles. CATL and BYD also made similar statements around the same time.[94]

In , it was reported that HiNa installed a 100 kWh sodium-ion battery energy storage system in East China.[95]

Chinese automaker Yiwei debuted the first sodium-ion battery-powered car in . It uses JAC Group's UE module technology, which is similar to CATL's cell-to-pack design.[96] The car has a 23.2 kWh battery pack with a CLTC range of 230 kilometres (140 mi).[97]

KPIT Technologies

[edit]

KPIT Technologies introduced India's first sodium-ion battery technology, marking a significant breakthrough in the country. This newly developed technology is predicted to reduce the cost of batteries for electric vehicles by 25-30%. It has been developed in cooperation with Pune's Indian Institute of Science Education and Research over the course of almost a decade and claims several notable benefits over existing alternatives such as lead-acid and lithium-ion. Among its standout features are a longer lifespan of 3,000&#;6,000 cycles, faster charging than traditional batteries, greater resistance to below-freezing temperatures and with varied energy densities between 100 and 170 Wh/Kg.[98][99][100]

Natron Energy

[edit]

Natron Energy, a spin-off from Stanford University, uses Prussian blue analogues for both cathode and anode with an aqueous electrolyte.[101] Clarios is partnering to produce a battery using Natron technology.[102]

Northvolt

[edit]

Northvolt, Europe's only large homegrown electric battery maker, has said it has made a "breakthrough" sodium-ion battery. Northvolt said its new battery, which has an energy density of more than 160 watt-hours per kilogram, has been designed for electricity storage plants but could in future be used in electric vehicles, such as two wheeled scooters.[5] The company filed for bankruptcy in November .[103]

TIAMAT

[edit]

TIAMAT spun off from the CNRS/CEA and a H EU-project called NAIADES.[104] Its technology focuses on the development of -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 + cycles to 80% of capacity.[105][106][107][108]

They are responsible for one of the first commercialized product powered by Sodium-Ion battery technology, as of October , through the commercialization of an electric screw-driver.[109]

SgNaPLus

[edit]

SgNaPlus is a spin off from National University of Singapore, that uses a propeitary electrode and electrolyte. [1] It is based in Singapore and leverages on research conducted by Alternative Energy Systems Laboratory (AESL) from Energy and Bio-Thermal Systems Division in the Department of Mechanical Engineering, National University of Singapore (NUS). The division is founded by Prof Palani Balaya. SgNaPlus also has rights for the patent for a non-flammable sodium-ion batteries.[citation needed]

Defunct

[edit]

Aquion Energy

[edit]

Aquion Energy was (between and ) 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 . Its assets were sold to a Chinese manufacturer Juline-Titans, who abandoned most of Aquion's patents.[110][111][109]

Sodium metal rechargeable batteries

[edit]

Types are:[112]

• Molten-sodium battery:
  • Sodium-sulfur battery (Nas).
  • Sodium-metal halide or Sodium-nickel chloride battery (Na-NiCl2 or Zebra battery).
• Sodium-ion battery (NaIBs).

See also

[edit]

• List of battery types
• Comparison of commercial battery types
• Alkali metal-ion batteries:
  • Lithium-ion battery
  • Sodium-ion battery
  • Potassium-ion battery
• Alkaline earth metal-ion batteries:
  • Calcium-ion battery
• Rechargeable battery
• Solid state battery

Notes

[edit]

References

[edit]

Sodium-Ion battery

Sodium-ion batteries operate analogously to lithium-ion batteries, with both chemistries relying on the intercalation of ions between host structures. In addition, sodium based cell construction is almost identical with those of the commercially widespread lithium-ion battery types. However, sodium-ion batteries are characterised by several fundamental differences with lithium-ion, bringing both advantages and disadvantages:

Advantages:

• Environmental abundance: Sodium is over times more abundant than lithium and more evenly distributed worldwide.
• Safety: Sodium-ion cells can be discharged to 0V for transport, avoiding thermal run-away hazards which have plagued lithium-ion batteries.
• Low cost: Sodium precursors (such as Na2CO3) are far cheaper than the equivalent lithium compounds.
• Three major families of materials for cathode chemistry options:
  • layered transition metal oxides
  • polyanionic compounds
  • prussian blue analogs
• Cathode materials can be synthesized from more sustainable transition metals such as Fe, Cu or Mn.

Disadvantages:

• Sodium-ion cells have lower energy densities than lithium-ion. This is due to sodium being significantly heavier and larger than lithium, as well as Na+/Na having a higher reduction potential than Li+/Li.
• Sodium-ion technology is not as well established as lithium-ion.

Sodium-Ion Battery Materials

Many of the battery components in both sodium-ion and lithium-ion batteries are similar due to the similarities of the two technologies. This post provides a high-level overview for the constituent cell parts in Sodium-ion batteries.

Sodium-Ion Cell Characteristics

• An energy density of 100 to 160 Wh/kg and 290Wh/L at cell level.
• A voltage range of 1.5 to 4.3V. Note that cells can be discharged down to 0V and shipped at 0V, increasing safety during shipping.
• 20-30% lower cell BOM cost than LFP.
• A wider operating temperature than lithium-ion cells (-20°C to +60°C).
• Typical Energy efficiency 92% at C/5.

Hard Carbon Anodes in Sodium-ion

• Emerging battery technology &#; promising cost, safety, sustainability, and performance advantages over current commercialised lithium-ion batteries1,2.
• Advantages:
  • widely available
  • inexpensive raw materials
  • rapidly scalable technology
  • meeting global demand for carbon-neutral energy storage solutions3,4.
• Adding metals would increase the overall energy density, but results in volumetric changes leading to failure.

Open Circuit Voltage

The OCV for the two cell datasets that we have to date are quite similar. The hysteresis between charge and discharge is small.

However, you can see that the voltage swing versus SoC is more significant than the other chemistries.

Sodium-Ion Degradation

• Over-voltage Charging
• Presence of Hydrogen
  • causes irreversible degradation of α-NaMnO2 when used as the cathode in Na-ion batteries [1].
• Defects in the Cathode Atomic Structure
  • these form during the steps involved in synthesizing the cathode material. These defects eventually lead to a structural earthquake in the cathode, resulting in catastrophic performance decline during battery cycling [2].

Hina NaCR-MP10 sodium ion cell 0.5C Charge / 0.5C Discharge and 98% capacity retention after 500 cycles.

Reduce the DoD to 90% and even at 2C / 2C cycling the capacity retention is 96% after cycles, expected life to 80% SOH is >25,000 cycles.

Sodium Ion Battery Pack

This low cot battery technology is approaching fast with lots of announcements.

Achieving 120Wh/kg at pack level.

The battery cell energy density, both volumetric and gravimetric will preclude the use of sodium ion in most vehicle applications. Except perhaps the very smallest packs where sodium can offer an advantage in terms of cost. Although, at the moment it is very early days for the maturity of the supply chain and the cost will be relatively high.

Want more information on LFP Lithium iron phosphate battery? Feel free to contact us.

References

1. Zhen Zhu, Hartwin Peelaers, Chris G. Van de Walle, Supporting Information: Hydrogen-induced degradation of NaMnO2, Chem. Mater. , 31, 14, &#;, June 21,
2. Xu, GL., Liu, X., Zhou, X. et al. Native lattice strain induced structural earthquake in sodium layered oxide cathodes. Nat Commun 13, 436 doi: 10./s-022--x
3. Behrooz Mosallanejad et al, Cycling degradation and safety issues in sodium-ion batteries: Promises of electrolyte additives, Journal of Electroanalytical Chemistry, Volume 895, 15 August ,
4. Comprehensive Inorganic Chemistry III, Reference Work &#; Third Edition &#;