Performance and manufacturability are two key criteria for evaluating the suitability of a battery technology. The lower energy density of SIBs compared to LIBs is a notable drawback. However, recent developments in active materials and cell design have increased the energy density of SIBs to around 180 Wh/kg, approaching the levels observed in LFP batteries (185-200 Wh/kg) (CATL 2023; Benchmark Mineral Intelligence 2025). When parameters beyond energy density are considered, SIBs are at par with, or better than, existing LIB technologies, as shown in Table 1.

SIB materials can be indigenised due to their complementarity with existing industries. Unlike lithium, sodium can be extracted relatively easily from seawater, rock-salt deposits, and lake brine, among other precursor materials, and purified, enabling greater upstream indigenisation. Key materials used in SIBs, such as Prussian blue analogues (PBAs), are already produced in India for use in pharmaceuticals and textiles (ACS 2017). Layered oxides (LOs), which share synthesis processes with lithium nickel manganese cobalt oxide (L-NMC) batteries, offer further domestic manufacturing potential (Liu et al. 2023). Increasing the production of active materials for SIBs could enhance domestic value addition beyond current plans focusing on electrodeto-battery production. With China considering export restrictions on battery materials, manufacturing equipment, and lithium-processing equipment, it has become imperative to identify supply chain opportunities using existing technology and infrastructure (Darley 2025).

SIBs can be produced on existing LIB manufacturing lines, simplifying industrial transition and accelerating development. Figure 1 shows that both SIBs and LIBs have similar structures, stacking geometries, and battery form factors (Liu and Hua 2023; Yu et al. 2023; Abraham 2020). Therefore, existing LIB manufacturing plants and technical know-how can be used to produce SIBs (CATL 2021). However, producers and owners of existing lines are likely to be bound by purchase and sale agreements. They might also be reluctant to handle a new chemistry that could result in cross-contamination in the manufacturing facilities. Thus, the theoretical ‘drop-in’ advantage of SIBs may have limited practical applicability, increasing the focus on vertical integration and strategic downstream collaborations among SIB materials manufacturers.

Hard carbon for SIB anodes could have lower manufacturing emissions than synthetic graphite for LIBs. The carbonisation temperature for hard carbon is 700–1,300°C, depending on the raw material. This is significantly lower than the graphitisation temperature of synthetic graphite, which is 2,800–3,000°C. Therefore, SIB anode manufacturing does not require specialised furnaces, lowering capital expenditure (CAPEX) and energy inputs (Carrère et al. 2024).

For the same battery capacity, SIBs can be charged and discharged 4 to 10 times faster than conventional LIBs. Fast charging at a 2C rate (i.e. full charging in 30 minutes) or higher can degrade most LIBs due to the deposition of a lithium layer on the anode. This decreases the availability of active lithium in the cell and blocks the anode’s active sites for lithium ions (Rudola et al. 2021). As a result, the battery capacity and energy density decrease. This layer can also form lithium dendrites that pierce the separator and cause short circuits, leading to thermal runaway and fire (Rudola et al. 2021).

On the other hand, SIBs do not exhibit any sodium plating when charged at a rate of 2C or higher (Rudola et al. 2021). In some cases, SIBs may have a higher volumetric energy density than LIBs when charged at 4C (full charging in 15 minutes) (Rudola et al. 2021). This could lead to faster charging of EVs and batteries for highpower applications. However, some new LIBs in specific applications are also showing charging and discharging rates as high as 6C.

SIBs have a lower risk of fire than LIBs when operated in Indian conditions. Batteries heat up during operation, and when a certain temperature threshold is exceeded, they are at risk of exploding or being damaged through a process known as thermal runaway. The fire safety of LIBs and SIBs depends on the electrolyte used (Committee of Experts on the Transport of Dangerous Goods and on the Globally Harmonized System of Classification and Labelling of Chemicals 2017). Electrolytes used in LIBs can catch fire when exposed to a spark at 36–45°C (flash point) (Committee of Experts on the Transport of Dangerous Goods and on the Globally Harmonized System of Classification and Labelling of Chemicals 2017). In comparison, the flash point for electrolytes in SIBs is greater than 100°C (Committee of Experts on the Transport of Dangerous Goods and on the Globally Harmonized System of Classification and Labelling of Chemicals 2017). This makes SIBs much safer for use in India, as the electrolyte temperature could exceed 50°C during operation, and the ambient temperature in India can also exceed 50°C.

SIBs perform better at extreme temperatures, particularly in sub-zero conditions, making them a good option for remote, high-altitude areas and defence applications. Due to the higher mobility of the sodium ion compared to the lithium ion in sub-zero temperatures, SIBs can operate at ambient temperatures as low as −40°C, whereas LIBs cannot operate efficiently below −20°C (CATL 2023; Zhao et al. 2023; Liu and Hua 2023; Reid 2023). This property makes SIBs suitable for niche applications, such as defence or deployment in cold, high-altitude regions.

Transportation and storage are simpler and safer for SIBs compared to LIBs. LIBs must be stored and transported with a 30 per cent state of charge (SOC) to prevent dissolution of the copper current collector (CC) in the electrolyte (Yu et al. 2023). In contrast, SIBs can be transported at 0 per cent SOC and 0 V, essentially as a ‘bag of electrolyte’ with no safety concerns, because the aluminium based CC does not react with sodium at low SOCs (Yu et al. 2023). The rate of catching fire during thermal runaway is directly dependent on the SOC of the battery (Committee of Experts on the Transport of Dangerous Goods and on the Globally Harmonized System of Classification and Labelling of Chemicals 2017). Although LIBs are not very prone to thermal runaway at 30 per cent SOC, transporting and storing batteries at 0 per cent SOC is logistically simpler and eliminates the risk of fire hazards (Yu et al. 2023). This also reduces the costs of additional cooling and safety equipment required for transportation.

SIBs rely far less on CRMs, which makes the supply chain more resilient to geopolitical scenarios. As seen in Figure 2, some SIB chemistries require significantly fewer CRMs, and others can be entirely CRM-free. The minerals represented in colour in the bar chart correspond to CRMs as per the list created by the Ministry of Mines in 2023 (PIB 2023b). Most of the minerals used in conventional batteries are concentrated in Africa, Australia, and South America, where significant aspects of the mining, processing, and refining infrastructure are dominated by Chinese companies (Greitemeier et al. 2025; Benchmark Mineral Intelligence 2025; Ministry of Mines 2025). Reducing reliance on CRMs could reduce dependence on other countries for mineral ores and processing equipment.

All batteries have three core components–anode, cathode, and electrolyte–and their chemical composition determines key performance characteristics. Lithium-ion batteries contain lithium along with other elements in the cathode and, typically, graphite in the anode. Sodiumion batteries include an array of cathode types, with varying chemical compositions, and hard carbon in the anode, as shown in Table 2. There are three main types of cathode chemistries available for SIBs–Prussian blue analogues (PBAs), layered oxides (LOs), and polyanionic compounds (PACs) (Liu and Hua 2023). Prussian blue analogues are gaining traction in China and the US, whereas the EU and India are focusing more on LOs and PACs (CATL 2021; Murray 2024; KPIT 2023). Most key raw materials used in SIBs are abundantly and inexpensively available in India, and some are already produced in other industries.

Furthermore, a major portion of the manufacturing process for SIBs is similar to that of LIBs (Tapia-Ruiz et al. 2021; CATL 2021; Abraham 2020). Figure 3 shows the schematic for SIB manufacturing and its similarities with LIB manufacturing. The chemical additives required for LIBs and SIBs are similar, and the downstream manufacturing processes are identical for both technologies. This suggests that upcoming LIB manufacturing units could readily adapt to SIBs.

Typically, the CAM, anode-active material (AAM), electrolyte, and CCs make up more than 50 per cent of the total battery value (Bauer et al. 2018; Ferraro and Tumminia 2024; Warrior et al. 2023).

At the time of writing, India’s plans for its battery sector focus on strengthening competitiveness in LIB and cell manufacturing–specifically, electrode coating, cell assembly, and battery-pack assembly. Given that these manufacturing processes are identical for LIBs and SIBs, battery materials manufacturing emerges as an immediate focus area for SIBs (CATL 2021; Abraham 2020). Component manufacturing presents itself as an untapped potential with high possibility for value addition. If material and component production can be scaled up simultaneously, it could create a significant opportunity to drive indigenisation of the battery value chain using SIB chemistry.

Complementary industries and local access to raw materials can accelerate the process of establishing component manufacturing by providing supply chain security, technical expertise, and efficient scaleup. Figure 4 shows the materials developed for the major components used in sodium-ion cells. These materials have been classified based on their use in commercial and lab-scale SIBs, domestic raw material availability, and the presence of domestic manufacturing capabilities. 

A significant share of the materials used in commercial SIBs is already manufactured in India. When factoring in value-addition levels, material requirements for commercial SIBs, and the availability of raw materials or complementary industries, four materials appear most suitable for domestic manufacturing: PBAs, hard carbon, carbonate-based electrolytes, and aluminium foil. However, since most ongoing research and pipeline projects are related to LOs and PACs (Xu et al. 2023), this study investigates PBAs, LOs, PACs, hard carbon, carbonate-based electrolytes, and aluminium foil.

Cathode active material

Three types of CAMs, each with distinct properties, are available for SIBs commercially–PBAs, LOs, and PACs (Liu and Hua 2023). Variations in their chemistry result in changes in the C-rate, energy density, stability, and cycle life. The structure of LOs is similar to that of NMC cathode materials, while the structure of PACs is similar to that of LFP CAMs (Liu and Hua 2023; Delmas 2018; Scherzl et al. 2023; Xiang et al. 2015). The choice of a specific cathode chemistry will depend on its suitability for the end-use application, cost, performance, and raw material availability and manufacturability of the CAM (Figure 5). Given the rapid advances in SIB chemistry, investing in R&D on battery materials becomes vital.

Prussian blue analogues have the potential to be completely free of CRMs and are already manufactured in India for the textile and pharmaceutical industries. They are being commercialised in China by CATL (CATL 2021). However, their manufacturing requirements could pose some issues while scaling up CAM manufacturing (Ge et al. 2024). Meanwhile, Indian research organisations are focusing intensive research efforts on LOs despite their reliance on CRMs. They have also been selected for more than 70 per cent of SIB pipeline projects worldwide (Xu et al. 2023).

This could be due to similarities in their synthesis process with NMC materials (Liu and Hua 2023; Xiang et al. 2015; Gruar and Kendrick 2017). Like PBAs, PACs also have the potential to be free of CRMs. However, the chemistries being commercialised currently in India and the EU depend on vanadium (Liu and Hua 2023).

The two primary production processes used to manufacture CAMs are solvent-based reactions and solid-state reactions. Solvent-based production methods mostly use co-precipitation (Gayara et al. 2023; Xi and Lu 2021; Liu et al. 2023), whereas solid-state methods use ball milling (Cheng et al. 2024; Luo et al. 2022). The products obtained through both methods undergo heat treatment and refining. The choice of synthesis method could impact CAM quality, quantity, and overall CAPEX (Rodriguez et al. 2022).

Co-precipitation produces a uniform CAM structure. However, the yield quantity is limited, and the product has more impurities (Park et al. 2022). Ball milling gives a higher product yield with fewer impurities, but the particles produced may not be uniform in size (Cheng et al. 2024). Since co-precipitation involves fluid handling, the required equipment is more complex and expensive than that for ball milling (Park et al. 2022). Additionally, the furnaces required for heat treatment of the CAM incur high CAPEX and energy costs (Ahmed et al. 2017). The sol-gel method is being developed for producing LOs and PACs (Gayara et al. 2023). It has proven to be more efficient than co-precipitation methods in laboratory settings and could offer higher efficiency at a commercial scale (Gayara et al. 2023). Variations in the sol-gel process, such as microwave sintering or additional hydrothermal calcination, could improve process efficiency (Gayara et al. 2023). However, the CAM material formed through these pathways could have lower purity (Gayara et al. 2023; Ge et al. 2023).

Prussian blue analogues

Prussian blue analogues are metal cyanide salts with the general formula Na4M[Fe(CN)6], where ‘M’ represents a metal atom (Liu and Hua 2023; Xi and Lu 2021). They have a lattice (mesh-like) structure, and their physical and chemical properties depend on the metal in the salt (Liu and Hua 2023). They are non-toxic and chemically stable and are used in the textile industry, the paint industry for dyeing, and the pharmaceutical industry as a treatment for radioactive poisoning (ACS 2017). They are broadly classified into two categories. The first category includes materials that contain zinc, nickel, and copper in the metal sites. They exhibit good cycle life; however, their capacity is low (Xi and Lu 2021). Materials in the second category contain iron, manganese, and cobalt and exhibit high theoretical capacity (Xi and Lu 2021). The performance of PBAs is highly sensitive to the water content in the lattice (Ge et al. 2024). The presence of water helps stabilise the structure of PBAs, but excessive water decreases their capacity (Ge et al. 2024). Therefore, humidity and water content across the entire CAM synthesis plant, cell manufacturing plant, and storage area must be strictly controlled to maintain high quality and performance.

Prussian blue analogues can be synthesised either by co-precipitation in a reactor or by a solid-state reaction in a ball mill (Cheng et al. 2024; Xi and Lu 2021; Chiang 2019). Figure 6 shows the co-precipitation reaction and further processes involved in producing Prussian white. Aqueous solutions of sodium ferrocyanide (Na4 [Fe(CN)6 ]) or potassium ferrocyanide (K4 [Fe(CN)6 ]), a salt of the required transition metal in the CAM such as manganese chloride (MnCl2 ·4H2 O), and sodium or potassium salt are fed into a reactor for co-precipitation (Shuangyu et al. 2024; Xi and Lu 2021). After the coprecipitation reaction, more sodium or potassium salt is added to saturate the mixture, and it is treated at high temperatures to facilitate the formation of larger precipitate particles (Shuangyu et al. 2024; Xi and Lu 2021). If potassium ferrocyanide was used in the process, the obtained precipitate is dissolved in an organic solvent, after which a suitable sodium salt is added to convert the potassium compound to a sodium compound (Shuangyu et al. 2024). The white sodiumbased complex is then separated from the solution via centrifugation (Xi and Lu 2021). The Prussian white is then obtained and further washed with ethanol and deionised water (Xi and Lu 2021). Finally, it is dried and calcined (heated) at high temperatures to remove excess water and volatile impurities (Xi and Lu 2021).

The food processing industry can provide raw materials for manufacturing PBAs, as sodium ferrocyanide and potassium ferrocyanide are used in table salt and other processed foods as anti-caking agents (Gupta et al. 2015).

Commercially, Prussian blue is synthesised through a co-precipitation reaction in a reactor. However, solidstate reactions using ball-milling techniques are being developed to produce higher-quality Prussian blue with low water content, as shown in Figure 7 (Chiang 2019; Cheng et al. 2024). In this method, hydrated sodium ferrocyanide and hydrated ferrous oxalate (FeC2O4.2H2O) are fed into a zirconia ball mill, where the mixture is processed to produce Prussian blue and sodium oxalate (Cheng et al. 2024). The products obtained are first fed into a centrifuge with deionised water, followed by anhydrous ethanol to separate the insoluble Prussian blue from sodium oxalate (Luo et al. 2022). The centrifugation step is repeated multiple times to increase the yield (Luo et al. 2022). The washed Prussian blue is dried in a vacuum oven to remove excess water and impurities (Luo et al. 2022). Ferrous oxalate can be replaced with a mixture of ferrous sulphate and oxalic acid, or with ferrous acetate (Luo et al. 2022).

Layered oxides

These are sodium-embedded metal oxides that form the basis of most pipeline SIB projects (Xu et al. 2023). The precursor materials for the sodium content can be its oxides, carbonates, borates, acetates, oxalates, hydroxides, oxyhydroxides, nitrates, sulphates, phosphates, silicates, arsenides, or cyanides of alkali metals and alkali earth metals (Gruar and Kendrick 2017). Precursors for the transition metals include oxides, carbonates, sulphates, acetates, nitrates, oxalates, hydroxides, oxyhydroxides, phosphates, silicates, and arsenides (Gruar and Kendrick 2017). These transition metal precursors are used in various industries, including polymer, pharmaceutical, chemical, textile, and agricultural, as catalysts (Cotton 2025).

The precursors are mixed in suitable quantities until a homogeneous mixture is obtained, as shown in Figure 8 (Gruar and Kendrick 2017; Barker and Heap 2019). The mixing can be done in a ball mill as a dry process, or the precursors can be dispersed in suitable organic solvents–such as ethanol, methanol, isopropyl alcohol, hexanol, ether, acetonitrile, or ethylene glycol (Gruar and Kendrick 2017). When solvents are used, the mixture is dried, and the obtained powder is either pressed into pellets or kept free-flowing (Gruar and Kendrick 2017; Barker and Heap 2019). The pellets/powder are then roasted/calcined (heated in a furnace) to obtain the required compound (Gruar and Kendrick 2017; Barker and Heap 2019). The heat treatment can be done in a tube furnace in stagnant air, in a flowing inert gas, or in a chamber furnace (Gruar and Kendrick 2017). The heating may be done in two steps, with the first heat treatment at a lower temperature and the second at a higher temperature (Gruar and Kendrick 2017). The obtained oxide is then cooled by either quenching (cooling by submerging the material in a liquid), annealing (leaving the material in the turned-off furnace), or normalising (cooling the material in air) and then ground into a fine powder (Gruar and Kendrick 2017). At each step, the process duration and temperature affect the final structure and properties of the LO formed (Gruar and Kendrick 2017; Barker and Heap 2019). Unlike PBAs, LOs are not affected by humidity, making the drying process simpler and less costly.

Polyanionic compounds

The most used PAC for SIBs is sodium vanadium fluorophosphate (NVPF) (Na3V2(PO4)2F3). The synthesis of NVPF, as shown in Figure 9, involves the thermal reduction (heat treatment) of vanadium pentoxide (V2O5) with a phosphate source, preferably dihydrogen ammonium phosphate (H2(NH4)PO4), and hydrogen gas or a mix of hydrogen and an inert gas to prepare vanadium phosphate (VPO4) (Hall et al. 2017). Conventionally, this step was carried out using carbon black instead of hydrogen, which increased the requirement for rammers and compressors. Therefore, new methods using hydrogen as a reducing agent were developed (Hall et al. 2017). The vanadium phosphate is then calcined (heated in a furnace) at a high temperature in an inert atmosphere with sodium fluoride (NaF) and an oxygenated hydrocarbon, such as glucose, sucrose, fructose, or cellulose, to produce NVPF (Hall et al. 2017). The NVPF produced must be normalised (air-cooled), and then washed and dried to remove impurities and excess moisture (Hall et al. 2017). Compounds similar to PACs are already manufactured by the fertiliser industry.7 China leveraged the overlaps between the fertiliser industry and LFP CAM to drive its LIB industry.

Anode active material

Graphite cannot be used in anodes for SIBs as the sodium ions cannot fit properly into the graphite interlayers (Liu and Hua 2023). As a result, organic materials such as hard carbon and soft carbon, inorganic materials such as tin and silicon, and cell configurations using similar cathode and anode materials have been developed (Liu and Hua 2023). Among these, hard carbon is the most popular material for commercially produced SIBs (Liu and Hua 2023).

Hard carbon

The hard carbon anode for SIBs can be manufactured from waste streams from various industries, including biomass, agricultural waste, polymers, and petrochemicals (Liu and Hua 2023; Wu et al. 2024). This wide and varying availability of raw materials makes the hard carbon supply chain resilient to fluctuations in precursor availability but susceptible to quality inconsistencies resulting from variations in precursor composition.

Traditional hard carbon is produced at scale through carbonisation (Wu et al. 2024), as shown in Figure 10. The selected precursor material is pulverised to obtain even-sized particles, enabling uniform and efficient carbonisation (Wu et al. 2024). This is followed by purification with various solvents to remove impurities, which reduces capacity and cycle life, and drying to remove solvent residue and moisture (Wu et al. 2024). The dried precursor is mixed with water and subjected to hydrothermal carbonisation (HTC) as a pre-carbonisation treatment (Titirici et al. 2024; Wu et al. 2024). This produces a carbonised slurry which must be filtered and dried to remove the excess moisture (Titirici et al. 2024). Subsequently, a secondary hightemperature carbonisation treatment is performed (Wu et al. 2024). During carbonisation, the material is heated to high temperatures in an inert atmosphere to convert the particles to hard carbon (Wu et al. 2024). The temperature and duration of the carbonisation process depend on the type of raw material selected (Wu et al. 2024). Two separate furnaces are used for the precarbonisation and secondary carbonisation processes, which helps extend the lifespan of the secondary carbonisation furnace (Wu et al. 2024).

Hard carbon manufacturers must balance the viability of production techniques with a stable supply of raw materials, both in terms of quantity and quality. The commercially viable raw materials for hard carbon include biomass such as sucrose, glucose, bamboo, lignin, coconut shells, and argan shells; polymers such as phenolic resins; and pitch-based materials, that is, polymer-like material obtained from coal, petroleum, or plants (Wu et al. 2024; Dahbi et al. 2017). Biomassbased precursors can be carbonised to produce highquality hard carbon in a single step, simplifying the overall synthesis process (Wu et al. 2024). However, ensuring quality control and a long-term stable supply for biomass feedstock is difficult (Wu et al. 2024). In contrast, pitch-based precursors have a stable supply chain but are difficult to carbonise, with the hard carbon produced also having poor electrochemical performance (Wu et al. 2024). Generally, the carbonisation temperatures range from 700–900°C for biomass to 1,100–1,300°C for synthetic materials (Titirici et al. 2024; Wu et al. 2024). Hard carbon can also be used in saltwater desalination and water purification. It is also being explored as the anode in LIBs, increasing the available market opportunity (Saju et al. 2024; Rajan and Indira 2022).

Electrolyte

The conventional electrolyte for SIBs consists of a sodium salt dissolved in an organic solvent (Liu and Hua 2023). The salt is generally sodium hexafluorophosphate (NaPF6), which is similar to lithium hexafluorophosphate (LiPF6) used in LIBs (Liu and Hua 2023). NaPF6 is used as a raw material in the manufacture of organic compounds in the pharmaceutical industry. It is also used as a catalyst in some reactions. NaPF6 can be synthesised using a wet reaction in a non-aqueous solvent, a solidstate reaction, or a gaseous reaction (Lekgoathi and Roux 2015). Wet processing results in a high impurity content in the final product, whereas dry processing yields a low final product due to incomplete reaction (Lekgoathi and Roux 2015). The yield from gaseous synthesis is high in purity but is very capital-intensive and requires complex techniques (Lekgoathi and Roux 2015). Conventional industrial-scale methods involve the reaction of phosphorus pentachloride (PCl5) and sodium chloride (NaCl) with liquid hydrogen fluoride (HF) or a reaction of phosphorus pentafluoride (PF5) and NaF in the presence of dry HF (Ould et al. 2021).

The solvent used is generally propylene carbonate (PC) or a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (Committee of Experts on the Transport of Dangerous Goods and on the Globally Harmonized System of Classification and Labelling of Chemicals 2017; Senthilkumaran et al. 2025; Liu and Hua 2023). Lithium-ion batteries generally use a mixture of EC with dimethyl carbonate (DMC) as the solvent in their electrolytes (Liu and Hua 2023; Committee of Experts on the Transport of Dangerous Goods and on the Globally Harmonized System of Classification and Labelling of Chemicals 2017). PC is considered to be the safest solvent and is therefore heavily used in industry for cleaning and degreasing (Alder et al. 2016). It is also used in the paints, pharmaceuticals, cosmetics, textiles, and agrochemicals industries (Alder et al. 2016).

Ethers and room-temperature ionic liquids are being explored as potential liquid electrolytes, and solid polymers, ceramics, and sodium superionic conductor (NASICON) materials are being examined as solidstate electrolytes for SIBs (Liu and Hua 2023). The performance and lifespan of the cell are heavily influenced by the concentration of impurities and the degradation mechanism of the electrolyte (Xiao et al. 2025). These adverse effects can be mitigated by using specific additives in the electrolyte.

Aluminium current collector

Aluminium foil is widely used for packaging to transport and store various products: pharmaceuticals, bulk quantities of tea and coffee, ready-to-eat meals, bakery products, frozen meat and fish, milk bottle caps, wine, machine oil and grease, powdered milk, confectionery, biscuits, chocolates, photographic film, gift wraps, household wraps, butter and margarine, and cigarettes (GoI 1989). Thus, it is readily available. Also, unlike lithium ions, sodium ions do not react with aluminium CCs at the anode (Liu and Hua 2023). Therefore, SIBs use aluminium foil CCs for both the electrodes, decreasing cost and weight (Liu and Hua 2023; Committee of Experts on the Transport of Dangerous Goods and on the Globally Harmonized System of Classification and Labelling of Chemicals 2017). Current collectors are made from 1000-series aluminium with a minimum purity of 99 per cent (Bizot et al. 2021). Their manufacturing process comprises three main phases: rolling, surface cleaning via etching, and conductive carbon coating.

The manufacturing process is outlined in Figure 11. Molten aluminium is used to form ingots, which are then hot-rolled to produce aluminium sheets 2–4 mm thick (European Aluminium Foil Association 2025). Alternatively, continuous casting can be used to directly produce sheets of similar thickness (European Aluminium Foil Association 2025). Continuous casting prevents cracks and porosity defects caused by localised shrinkage, yielding a good surface finish (Gardner 1960). It also consumes less energy, reduces emissions, improves yield, and reduces capital inputs by eliminating the need for reheating furnaces, soaking pits, and primary hot-rolling mills (Gardner 1960).

Electroforming is also being explored as a method for manufacturing aluminium foil because it can produce foils with specific microstructures (Scherzl et al. 2023). Structured CC foils can increase the active surface area and decrease diffusion pathways for the ions (Scherzl et al. 2023). This increases the cell’s energy density and power (Scherzl et al. 2023). The electroforming process is precise to the micron and consumes less energy than roll forming (SPC n.d.). However, commercial uptake has been limited due to high equipment costs, the long duration of the forming process, machining requirements to remove surface inaccuracies, and the need for skilled labour (Mechanical-Engineering.com 2019).

The hot-rolled aluminium sheets are cold-rolled to produce CC foils with a thickness of at most 20 microns (Busson et al. 2018; Bizot et al. 2021). In comparison, food-grade aluminium foil is 11–18 microns thick (Kerry 2012; US Packaging and Wrapping LLC n.d.). The aluminium sheets are coated with oil to prevent overheating due to rolling friction, foil sticking to the rollers, and roller degradation from wear (Ulrich et al. 2016). Upon exposure to air, a layer of aluminium oxide (Al2O3) forms on the aluminium sheets, significantly decreasing the conductivity of the electrodes (Sato 2010). To degrease the sheets, coils of rolled foil are thermally treated, which softens the foil and causes metal recrystallisation. This decreases its mechanical strength and thickens the aluminium oxide layer (Ulrich et al. 2016).

The oxide layer must be removed to prevent performance degradation in the cells. Etching is used to remove oxides and other surface impurities, and the foil is coated with a conductive carbon layer using vapour deposition (Sato 2010). The etching process can be dry or wet, depending on the required properties of the aluminium foil (Sato 2010). Dry etching utilises plasma, whereas wet etching uses chemicals or electrolytes (Iida et al. 1981). The former requires complex and expensive equipment and generates gaseous waste that may be toxic and must be treated before it can be emitted (Cadence PCB Solutions n.d.). Wet etching, conversely, requires less sophisticated equipment, such as immersion baths and tanks, but produces corrosive liquid waste that requires proper treatment before disposal (Cadence PCB Solutions n.d.). From an industrial process perspective, dry etching is highly uniform but has a high probability of damaging the surfaces of thin metal sheets and a lower throughput (Cadence PCB Solutions n.d.). Although wet etching is less uniform due to variations in fluid dynamics, it is less likely to damage the surfaces of thin foils and offers a very high throughput, which makes scale-up easier (Cadence PCB Solutions n.d.).

The vapour deposition process used for the conductive carbon coating has its own challenges, according to Sato (2010). It can create wrinkles in the aluminium sheet due to compressive stresses in the carbon coating, which cause defects in the CAM coating process. However, the recesses created on the foil surface by wet etching make the surface of the foil uneven. This creates a non-uniform, non-continuous layer of carbon coating on the foil, which prevents the formation of sites with compressive stresses that cause wrinkles in the foil. The carbon coating can be done using arc ion physical vapour deposition, sputtering, or plasma chemical vapour deposition, although the conductivity of the deposited coating is the highest for arc ion plating. Figure 11 shows the CC manufacturing process.

A strategic roadmap for SIB development in India can provide a clear vision for the future by tracing long- and medium-term milestones back to short-term innovations. This helps to create a shared understanding among industry, academia, and government stakeholders by building consensus on technology innovation plans. The process could unfold across three stages, with increasing focus on indigenisation:

Stage 1: Research, patenting, and jointly scaling up existing technology

India’s immediate priority should be to focus research on technical bottlenecks related to materials, manufacturing, battery design, synthesis process optimisation, and supply chain constraints, and to establish technological proof of concept for highperforming SIBs at laboratory scale. Research on PBAs could aim to improve their energy storage capacity, optimising processes to reduce energy and water requirements, and increase process throughput. For LOs, focus areas might include decreasing the CRM content while improving the stability and cycle life. Polyanionic compounds mainly face challenges related to storage capacity and CRM requirements, which could be addressed through development of new PAC materials. Research and development for the anode should address the low capacity and inconsistency in the raw material of hard carbon and the viability of repurposing graphite from LIBs. They could also investigate electrode coatings, which ensure a stable solid electrolyte interface (SEI) and raise the threshold temperature for thermal runaway (Lin et al. 2025). For electrolytes, R&D could focus on solid materials, purity assessment throughout the cell life cycle, additives to increase cell life, product safety, and thermal stability under extreme temperatures (−40°C to +71°C) for defence applications.

Apart from the conventional areas of battery materials development, other avenues of cell development, such as improving performance with new cell formats and configurations, can be explored in parallel. Table 3 highlights some critical R&D areas related to cell and battery configuration that are essential for keeping pace with the rapid developments occurring globally and in China.

India’s immediate priority should be to focus research on technical bottlenecks related to materials, manufacturing, battery design, synthesis process optimisation, and supply chain constraints, and to establish technological proof of concept for highperforming SIBs at laboratory scale.

At the same time, India can be an attractive scale-up destination for Western-validated technologies due to the low manufacturing costs and large potential demand. Partnerships between local large-scale manufacturers and foreign companies with established SIB technology can accelerate industrial adoption by leveraging existing global knowledge capital, understanding supply chains and workforce development, and testing deployment potential across domestic use cases.

Stage 2: Prototyping, pilot projects, and standardisation 

The next phase should emphasise indigenisation and supply chain development. Laying the foundation for domestically manufacturing materials, this phase will include advancing research to higher TRLs through pilot projects. With the aim of initiating first-of-a-kind domestic manufacturing of CAMs, AAMs, and CCs, this stage will demand a collaborative, ecosystem-driven approach. Industry–academia initiatives with bidirectional feedback and financial support for start-ups and national laboratories, via government research grants and private investment, will be crucial for pilot-scale initiatives.

National laboratories under CSIR, the International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), and the Centre for Materials for Electronics Technology (CMET) will play a crucial role in advancing academic research from TRLs 3–6.

Indigenous equipment development, leveraging complementary industries, could begin at this stage, enhancing supply chain resilience by reducing dependence on Chinese equipment suppliers and avoiding trade delays. Simultaneously, establishing procedures and standards for material handling, cell testing, and battery performance will be essential for manufacturing high-quality SIBs.

Downstream players will be needed to signal demand for SIB materials, making it important to align with the rapid growth of cell manufacturing in India. According to the announced plans, India is expected to have cell manufacturing capacity exceeding 150 GWh by the end of 2030.

Stage 3: Commercialisation and scale-up

The final stage should focus on promoting the commercial uptake of domestically manufactured SIB materials and achieving scale, cost-competitiveness, and commercial lift-off. At this point, there is a transition from first-of-a-kind to nth-of-a-kind manufacturing, and financially critical CAPEX decisions on scaling equipment, materials, and plants are made. To minimise the investment risk, especially in the face of cheaper Chinese alternatives, supportive offtake mandates and protective trade regulations could act as catalysts.

Improving bankability will enable the technology to be perceived as de-risked, facilitating increased capital flows into the ecosystem and supporting both scale and heightened private sector demand. Finally, commercialisation can be accelerated by integrating innovative equipment with higher throughput and better yield, increasing automation, and optimising shop-floor design to maximise efficiency and ensure workforce readiness.

India’s ability to remain resilient and competitive while it aims to reach net-zero goals and meet a projected 1.3 TWh battery demand by 2047 relies on diversifying its battery storage technology strategy beyond LIBs. While LIBs currently dominate, their reliance on imported critical minerals and a supply chain dominated by China poses significant geopolitical and economic risks. To ensure energy security and technological sovereignty, India must strategically pivot towards SIBs as an indigenous alternative.

Sodium-ion batteries present a unique opportunity to leverage India’s existing industrial capabilities. Unlike LIBs, the supply chain for SIB materials for cathodes, electrolytes, and anodes aligns with domestic capabilities in sectors like pharmaceuticals, chemicals, and textiles. This compatibility offers a pathway to rapidly indigenise manufacturing, reduce import dependence, and mitigate the risks associated with critical mineral scarcity. Additionally, SIBs offer distinct advantages in safety, fast charging, and low-temperature performance, making them ideal for specific applications like defence and grid storage.

To unlock this potential, a cohesive roadmap is essential. India must first prioritise R&D to develop indigenous active materials, followed by significant investment in prototyping and equipment standardisation to bridge the funding gap compared to global peers. Finally, policy interventions such as offtake mandates and trade protections will be crucial to drive commercial scale-up. By fostering collaboration across academia, industry, and policy, India can transform its energy transition challenge into an industrial advantage, establishing itself as a global leader in next-generation battery technology.

The supply chain for SIB materials for cathodes, electrolytes, and anodes aligns with domestic capabilities in sectors like pharmaceuticals, chemicals, and textiles.