A breakthrough in EV battery tech

Sodium-ion battery offers a potential low-cost alternative to lithium-ion battery for India and presents an opportunity to achieve energy independence

Lithium-ion batteries have been the go-to technology for vehicle electrification over the last decade. However, the rapid rise in the electric vehicle (EV) demand in the past two years has resulted in massive pressure on the battery supply chain. This makes it indispensable to diversify into newer battery technologies beyond lithium. Sodium-ion is a promising technology to complement lithium-ion batteries or even replace them in some cases.

India is taking successively bigger initiatives to develop energy sustainability and independence. The latest Economic Survey noted that with the aim of electrifying 30 per cent of India’s vehicle fleet by 2030, the domestic EV market is projected to grow at a compound annual growth rate of 49 per cent between 2022 and 2030, and annual sales are expected to reach 10 million by that time. This will, however, be possible only if India has a long-term solution to overcome the challenges of the high cost of EV batteries, import dependence on key battery raw materials, and lack of India-made cell technology

Sodium-ion as an alternative

Over the years, different chemistries have been used in EV batteries. In 2010, the world’s first mass-produced EV by a Japanese car maker employed a lithium-ion battery with NCM (nickel-cobalt-manganese) chemistry, followed closely by an American EV maker introducing their first commercial EV with a similar NCA (nickel-cobalt-aluminium) chemistry. These chemistries have superior performance, but their raw material supply sources, especially for nickel and cobalt, are concentrated in a few regions across the globe, which makes them susceptible to shortages and price fluctuations. This led to the resurgence of LFP (lithium-iron-phosphate) chemistry as a low-cost alternative. The material cost of an LFP battery is 20-30 per cent lower than the NCM, which has led to a global shift towards LFP batteries, with major OEMs committing to the cause.

Automakers are under immense cost pressure to enable the widespread adoption of EVs. However, recent rapid growth in the worldwide EV battery demand has exposed the bottlenecks with lithium mining. The enormous surge in prices of lithium carbonate and lithium hydroxide in the last two years has accelerated the search for newer battery technologies beyond lithium with more abundant, sustainable and low-cost resources.

Sodium, a close cousin of lithium belonging to the alkali metal family, can be the answer. Large quantities can be extracted from both the earth’s crust and seawater and at a lower cost than lithium. Moreover, as sodium does not react with aluminium, an aluminium current collector can be used at both electrodes, unlike the lithium-ion battery, which requires a more expensive copper current collector at the anode. Also, sodium-ion and lithium-ion batteries are similar in cell construction, so production will need only slight assembly-line modifications, making it easier to switch. Overall, a sodium-ion battery is 20-30 per cent cheaper than an LFP battery.

Interestingly, the Sodium-ion battery has no over-discharge characteristics, which means it can be allowed to discharge to zero volts. This reduces the chances of fire hazards during transportation. In contrast, a lithium-ion battery must always be stored with a minimum charge, making it susceptible to thermal runaways. Sodium-ion batteries have faster charging times and could have a longer lifespan compared to lithium-ion variants.

More takers for sodium-ion technology

Lately, sodium-ion technology has been gaining traction, with 10-12 companies working to commercialise it for EV applications. This includes the world’s largest EV battery manufacturer that unveiled its first-generation sodium batteries in mid-2021 and has announced commercial launch in 2023. A Chinese sodium-ion battery manufacturer has already set up the world’s first GWh-class production line and rolled out the first product off the line in December 2022. A UK-based start-up claims to have an extensive sodium-ion technology focused IP portfolio comprising 21 current patent families. A leading US-based manufacturer of sodium-ion batteries has announced a strategic agreement for mass production by 2023.

Most of these players are, however, in the early industrialisation stage. A major challenge in scaling up production is development of suitable materials and supply chain for both electrodes and the electrolyte. Rest of the components such as collectors, separators, solutions, etc can be used from lithium batteries.

What makes it so relevant for India

It is often argued that sodium-ion batteries suffer from lower energy densities, which essentially means they are heavier than the lithium-ion variants for the same energy delivered. However, the first generation of sodium-ion batteries has reached energy densities up to 160 Wh/kg while the most recent LFP batteries have achieved just over 180 Wh/kg.

For the next decade, a large part of the Indian market will comprise of smaller sub-10kWh batteries that go into two- and three-wheelers. This is a cost-sensitive market and the majority of the OEMs have switched to LFP batteries due to lower costs. The current electric two- and three-wheelers in production have batteries with an energy density of 130-150 Wh/kg. This presents a ready-made use case for sodium-ion chemistry as a relevant low-cost, sustainable alternative.

Also, sodium-ion batteries are relevant as a cost-effective alternative for applications where weight and energy density are less of a concern, such as stationary energy storage systems, which is a sunrise sector in India.

Way ahead

India has traditionally depended on oil imports for its energy needs and transitioning to lithium-based BEV technology as a long-term option is under question. Sodium-ion batteries present a promising opportunity in developing India’s home-grown battery technology, thereby reducing the dependency on imports. Moreover, the need for accelerated growth of EVs at a lower cost offers the scale for India to become a global leader in manufacturing sodium-ion batteries.

The writer is new age mobility partner, EY-Parthenon