Sodium-ion batteries: A real challenger or another passerby for Indian storage tech?

Energy storage is a dynamic battleground of evolving technologies where many make headlines, but few become commercial products. Since the formal launch of Sodium Ion Battery (SIB) cells in 2003, it has taken over two decades of development to get them ready for the real world, and many global companies have jumped onto the bandwagon. The world’s largest EV maker, BYD, broke ground earlier this year on a 30 GWh SIB facility, and the projected capacity for 2030 is already above 150 GWh. For comparison, the global installed capacity of Lithium Ion Battery (LIB) is around 2,100 GWh after continued investments over the past decade. To fully understand SIB, its environmental impact and its likelihood of success, we start with a walk down the periodic table.

Walk down the periodic table

Lithium gained prominence due to its compact atomic size which made it an efficient carrier of charge. Sodium was considered a viable contender because it lives, quite literally, just a block away from Lithium on the periodic table and met other requirements. However, SIB cannot match LIB’s energy density due to its larger size. The initial consumer electronics use cases had space constraints, resulting in the adoption of LIBs. With the advent of electric vehicles (EVs), NMC (Nickel-Manganese-Cobalt along with Lithium) or NCA (Nickel-Cobalt-Aluminum along with Lithium) were the preferred chemistries. The initial reductions in LIB prices were due to the scaling of mining and refining capacities to meet demand from EVs.

But China, which was keen to build a pole position in the new energy automotive sector, preferred Lithium Ferro Phosphate (LFP) due to its cost and safety. It has spent about $29 billion over 20 years in subsidies and incentives, leading to 1,400 GWh of manufacturing capacity. The private sector also responded with deep research, which has significantly bridged the gap in energy density between NMC and LFP. By 2023, it was estimated that over one-third of the EV cars sold in the West had an LFP battery and even Tesla, which began its journey with NCA, is now adopting LFP.

These developments drove down the prices of LIB packs from $1,200 per kWh to about $120 per kWh in 2024; however, prices over the next few years are likely to drop only by 30% to 50%. Most light EVs can reach capital cost parity with their ICE counterparts at a pack cost of about $100 per kWh. Thus, LIB is already tantalizingly close to the ‘takeoff’ point. So why should India consider investing in an alternate chemistry that will go through the same learning curve? There are multiple reasons for this, including the significant geopolitical implications.

Why should India think about investments in SIB

Firstly, as capacities for LIB are scaled, it became clear that the costs of these critical materials (Lithium, Nickel and Cobalt) put a fairly hard floor on the battery costs. The mining of critical and rare earth elements can be described as a “zero-sum game” in which a handful of countries exert control in a market characterized by limited global reserves, intense global competition, and increasing global demand. There were also negative externalities like the impact on the environment and local communities. The table on the next page illustrates this. Sodium-ion cells offer a promising alternative by relying on abundant and earth-friendly materials. This positions sodium-ion technology as a sustainable and scalable solution for energy storage needs, contributing to a more environmentally friendly and resource-resilient energy landscape.

Secondly, renewables will drive demand for stationary storage to address intermittency. A pack cost of $100 per kWh (around ₹8,400 currently) is not good enough for stationary storage. At these prices, packs with a typical life of 4,000 cycles roughly add ₹2 per unit stored, which is a barrier to large-scale adoption. SIB cells can already be manufactured at sub-$100 per kWh but could potentially reach levels of $50 per kWh (around ₹4,200) while also improving cycle life, which can unlock distributed renewable storage.

Lastly, SIB offers a massive geopolitical and supply chain advantage. Between 60% and 80% of the critical mineral refining (Lithium, nickel, and cobalt) for batteries happens in China, making it a potential choke point.

Sodium’s universal availability renders large-scale, cost-competitive refining feasible in almost any country with the right financial and technological muscle.

Demystifying Sodium ion cathodes

In simple terms, think of sodium-ion battery cathodes like ingredients in a recipe. Polyanion cathodes are like a strong and stable backbone that holds sodium ions together, ensuring reliability. Prussian white, or Prussian blue, when fully charged, acts like a molecular sponge, soaking up sodium ions efficiently with its special structure. Layered oxide cathodes are akin to building blocks stacked neatly, providing a spacious and organized environment for sodium ions to move in and out easily. Each type has its unique way of handling sodium, offering a mix of stability, efficiency, and capacity. It’s like choosing between different tools for a job – you pick the one that suits the application at hand best.

Immediate applications of SIB in India

SIB is a versatile, low-cost, stable and safe energy storage option for telecom towers, especially in remote or off-grid areas. The significant environmental, social, and governance (ESG) advantages of SIB are additional benefits. SIBs are much less prone to thermal runaways and fire hazards than LIBs. This makes them a reliable and secure choice for telecom infrastructure, aligning with the increasing emphasis on sustainability, safety, and resilience in the telecommunications sector. SIBs are also a strong contender for grid storage, behind-the-meter applications, and rooftop solar.

Also, in India, two and three-wheeler EVs are driving electrification with a share of 5% and 20%, respectively, in new sales (excluding e-rickshaws, which are 100% electric) for whom the lower energy density of SIBs is not a big concern. For commercial fleets, SIBs offer the advantage of fast charging (80% range in 30 mins). SIB energy density today is around 80 to 120 Wh/Kg while LFP is above 150 Wh/Kg, which brings SIB within striking distance. SIB demonstrates better temperature stability and safety, reducing pack costs further due to less thermal management needs.

The Indian certification ecosystem, which ensures battery safety, does not currently have experience of working with SIBs and will need to go through a learning curve as well.

SIB recycling

The advantage of the low cost of materials in a SIB is also a curse when considering the end of life. There are potentially no valuable minerals, and some variants of SIB have toxic materials like Vanadium. As with plastics, unless the economics of recycling are self-sustaining, we are prone to mishandling waste streams. We need to tread this area with caution.

Strategic implications and energy independence

NITI Aayog has projected an energy storage demand of 260 GWh in India by 2030, of which grid-scale stationary storage has the highest share at around 40%. SIB offers an opportunity to build a fully domestic high-tech industry that could support our push for renewables and also unlock safe, low-cost electric mobility. India has already traversed this path in other industries like Steel and Aluminum, where it ranks among the top 5 manufacturers globally. In addition, with the increasing adoption of solar globally, the potential market is not restricted to India anymore.

Reliance latched onto this with its acquisition of Faradion and plans to set up a 5 GWh SIB facility in India. The ACC PLI scheme works very well to promote reasonably established technologies, but we would do well to remember that China backed LFP when it was a new entrant.

It is our opinion that multiple technologies will coexist, and there is unlikely to be one winner-takes-all chemistry. So, SIBs are quite likely to supplement LIB and not replace them. The real question is if we might have the gumption to invest aggressively behind it to accelerate our Net Zero journey while fulfilling the mandate of “Viksit Bharat”.

About the Authors:

Mr Venkat Rajaraman (L) is the Founder/CEO, and Mr Gautam Patil (R) is the Head of Strategy at Cygni Energy, a leading storage technology company with cutting-edge expertise in EV Batteries (2W & 3W) and Energy Storage Systems (Telecom, Portable Power, etc).

Cygni has deployed over 125MWh of storage solutions and powered over 100,000 EVs. The company currently has a fully automated battery manufacturing facility in Hyderabad with automated cell sorting, laser welding, cell characterization, and end-of-line (EOL) testing. Cygni’s new Greenfield project is currently underway which supports a capacity of 1200MWh.

Also read: Sodium-ion batteries | Current status of the technology and supply chain.