Sodium-ion (Na-ion) batteries, a much more abundant and cheaper alternative to the standard Lithium-ion, are on the verge of commercialisation, explain Carlos Ruiz, Martina Lyons, Isaac Elizondo Garcia and Zhaoyu Wu at IRENA. Though there’s enough Lithium in the world to support global electrification targets, tightening demand and supply chain constraints point at the urgent need for an alternative. The cost of a Na-ion battery cell is expected to be around $40-80/kWh compared to an average of $120/kWh for a Li-ion cell. Na-ion batteries are safer (operating temperature range, stability), and have faster charging times and longer cycle lives. Their energy density is lower, making them bulkier and heavier. But at 160 Wh/kg (which should improve) it is still good enough for city-range EVs and Chinese manufacturers have already announced Na-ion compact EVs with a 250 km range. Production capacity is forecast to grow from 42 GWh/year in 2023 to 186 GWh/year by 2030: enough to power 4.6m EVs manufactured per year. And for stationary grid and home storage, size is not a problem. It’s a story not only of Na-ion, but of the importance of the global energy transition to innovate the alternatives to the mainstream answers, ensuring supply chain diversity and affordable prices, say the authors.

With renewables at its core, the global energy transition towards net-zero will require changes in both the production and the consumption of energy. One of these changes will be the eventual electrification (direct and indirect) of energy end-use sectors (including buildings, transport and industry) which will result in the tripling of global electricity demand by 2050, according to IRENA’s World Energy Transitions Outlook (WETO).

A successful transition needs Storage

Under these premises, the importance of storage for a successful transition cannot be overstated. IRENA’s 1.5°C Scenario sees a need for battery storage to offer significant flexibility to the power system, reaching almost 360 GW by 2030, and 4,100 GW by 2050. But, beyond the power sector, battery storage will play a critical role in the decarbonisation of end-use sectors, as a critical component of electric vehicles for example, which are on track to account for 90% of road transport by 2050.

The problem with Lithium-ion (Li-ion) batteries

Lithium-ion (Li-ion) batteries have been at the forefront of modern energy storage solutions due to their high energy density and versatility, however the growing demand for lithium-ion batteries has led to concerns regarding sustainability, resource availability, geopolitical considerations, and potential supply chain bottlenecks. To be clear, the world has more than enough materials to sustain the energy transition, including lithium. However, the main concern comes from battery supply chains struggling to keep up the pace of ever-growing EV demand, and the skyrocketing lithium carbonate prices caused by this squeeze. These concerns signal the need for exploring alternatives and ways to sustainably optimise the crucially needed storage solutions. Once again, innovation might be the catalyser to speed up the transition, in this case with a range of emerging chemistries for battery storage technologies.

Sodium-ion (Na-ion) batteries

This is where sodium-ion (Na-ion) batteries come in. Na-ion batteries are similar in design and construction to Li-ion batteries but relying on sodium compounds rather than lithium. Sodium is about a thousand times more abundant than lithium, which means that this technology could potentially alleviate the short-term supply concerns which affect its lithium-based counterparts, and the cost volatility this entails by widening the portfolio of viable battery chemistries and ease the squeeze on lithium mining and processing.

Sodium-ion battery manufacturing relies mainly on soda ash as a sodium precursor, a compound that is far more abundant and more sustainable to extract and refine than lithium, making it lower cost, and less susceptible to resource availability concerns and price volatility. The US alone has identified about 47 billion tons of soda ash resources and over 23 billion tons of soda ash reserves. Soda ash can also be (and already is) produced synthetically from salt and limestone through the Solvay process, opening the possibility of it being produced virtually around the globe.

Pros and cons

Na-ion batteries have several key characteristics that offer promising advantages over existing lithium-ion batteries, and which make them viable for specific applications. One of the main advantages is their cost. The cost of Na-ion batteries is expected to be significantly lower than that of Li-ion batteries. This is around 40-80 USD/kWh for a Na-ion cell compared to an average of 120 USD/kWh for a Li-ion cell.

Sodium-ion batteries also offer advantages in terms of sustainability, compared to Li-ion batteries. The large abundance of sodium opens the door for more diverse sourcing. At the same time, some configurations can open the door to reducing the need for critical materials, such as copper (given their aluminium current collector), nickel and cobalt. While layered metal oxide Na-ion batteries (the most predominant type), such as the one developed by Faradion, use nickel and cobalt, some Prussian white and some polyanion types do not use any of these materials.

In terms of safety, sodium-ion batteries have shown promising results, having wider operating temperature ranges and a more stable anode-electrolyte mixture than Li-ion batteries, and the possibility of being safely transported fully discharged. In terms of performance, sodium-ion batteries have excellent capacity retention even in freezing temperatures, fast charging times (80% SOC in 15 minutes) and longer cycle lives (80% capacity retention after 4,000-5,000 cycles) than lithium batteries.

One of the main limitations of these batteries is their energy density, as lower energy densities also mean bulkier and heavier batteries. The latest announcements from some battery manufacturers mention energy densities of 160 Wh/kg for these batteries, also mentioning 200 Wh/kg as their next milestone. While these numbers are comparable to some lower-end Li-ion batteries, they are still behind other commercially available Li-ion chemistries, e.g. Tesla batteries in the range of 250 Wh/kg.

Applications

These characteristics make sodium-ion batteries suitable for use in a number of applications. One of the most promising is stationary storage. The rapidly accelerating integration of variable renewables is creating a pressing need for inexpensive energy storage, not only at the utility-scale, but also behind-the-meter (at home or in businesses). The low cost, long life, safety and performance characteristics of Na-ion batteries, paired with the fact that size and weight are not big concerns for stationary applications, could make them competitive with Li-ion. Additionally, these batteries could also be used in EVs. Particularly in short-range EVs, given their current 160 Wh/kg energy density. In fact, this is already starting to happen with a number of Chinese battery and car manufacturers making a number of announcements for Na-ion battery-powered compact EVs with ranges in the 250 km range.

This figure is in line with currently commercially available small EVs. While it might seem small, it is expected to increase, plus it is more than enough for urban commutes and short trips. For example, in Germany, the average daily distance travelled in an urban setting is about 19 km, which means that a single charge could be enough to last over 10 days of use in an urban setting. If we also consider the lower cost of these batteries in the equation, they have the potential to be disruptive for the EV market.

Commercialisation soon, led by China

The interest in Na-ion batteries keeps increasing and giving the impression that this technology is very close to reaching its breakout moment. This is particularly evident when looking at the sheer number of projects announced and the very ambitious plans by some manufacturers to deploy Na-ion EVs and reach commercial production of Na-ion batteries as early as 2023. These include announcements from: CATL, Chery, BYD, JAC / HiNa, Faradion, Natron, PNNL, and others, including for grid storage projects.

Sodium-ion batteries are already being developed by several companies, mainly in China, and production capacity is forecast to grow from 42 GWh/year in 2023 to 186 GWh/year by 2030 (IRENA, forthcoming). This capacity would be enough to power 4.6 million EVs manufactured per year (assuming a capacity of 40 kWh per vehicle).

Outlook

For certain applications, Sodium-ion batteries have the potential to compete with existing lead-acid, lithium-ion batteries, such as NMC (nickel-manganese-cobalt) or LFP (lithium-iron phosphate). However, there are a number challenges that must be overcome to achieve this, including the improvement of their construction and materials, establishment of supply chains, achieving economies of scale, and in essence proving they are a functioning and cost-effective solution.

This and the coming year will be decisive for this technology given the announcements made. But regardless of their potential success, it is important to highlight the importance of innovation in a renewables-based energy transition, resulting, in this case, in chemistries that can complement lithium-based batteries for certain applications, reducing dependency on a single material and opening the door for more diversified sourcing of materials and technologies. Sodium-ion batteries show great promise and could become a good alternative for specific applications, helping to alleviate supply chain bottlenecks and accelerate the energy transition. With further research and development, they could play a significant role in the transition to a carbon-neutral energy system.

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Carlos Ruiz is a Programme Officer, Innovation and End-Use Sectors, IRENA

Martina Lyons is a Programme Officer, Innovation and End-Use Sectors, IRENA

Isaac Elizondo Garcia is a Consultant, Critical Materials, IRENA

Zhaoyu ‘Lewis’ Wu is an Intern, Innovation and End-Use Sectors, IRENA and Staff Research Associate, Center on Global Energy Policy