After three decades of steadily decreasing lithium-ion battery (LIB) costs, 2022 marked a historic reversal: cell prices rose significantly due to the surge in lithium raw material costs. This supply chain volatility has pushed the battery industry to seriously consider alternative solutions, with sodium-ion batteries (SIB) emerging as leaders.

SIBs offer interesting advantages over LIBs:

• Low-cost raw materials (sodium vs. lithium)
• More sustainable and abundant metals on Earth in cathode materials and current collectors (Fe, Mn, Al vs. Ni, Co, Cu)
• Geographically diversified distribution of raw materials for better supply chain resilience
• Excellent rate capability, especially in Prussian blue analogues
• Superior low-temperature performance
• Greater safety in some chemistries (e.g., NFPP)
• Ideal for stationary energy storage (BESS), with potential for EV applications
• Compatibility with direct replacement in existing LIB gigafactories

Currently, SIBs cost about $125/kWh, but a techno-economic study by Yao et al. suggests that costs could drop to $30/kWh by 2045, as shown in Figure 1. This opens up a vast opportunity for innovation in all aspects of SIB production. In contrast, LIBs are approaching the maximum cost limit of minerals, limiting further gains through traditional expansion.

Although LIB prices have dropped drastically since 2023, the potential advantages of SIB chemistries, including sustainability and supply chain instability, maintain their position as a valid complement to LIBs for numerous applications.

Market trends

The performance characteristics of sodium-ion batteries (SIBs) enable them to compete with lithium iron phosphate (LFP) cell chemistry in similar applications that require low-cost batteries, with an acceptable trade-off in terms of lower energy density. Target markets include battery energy storage systems (BESS), backup storage for data centers, and mid-to-low-end electric vehicle markets.

Although current SIB battery costs ($125/kWh) are not yet competitive with lead-acid batteries ($50-70/kWh), projections show that SIB batteries could surpass lead-acid batteries in terms of cost-effectiveness between 2032 and 2047. This wide range reflects uncertainties in mineral prices, demand growth, and geopolitical supply chain disruptions. Companies investing in research and development today will be best positioned to remain competitive tomorrow. The last two decades in battery manufacturing have been characterized by the expansion of lead-acid batteries. As a vast knowledge base and infrastructure are now available, the commercialization of SIB batteries is happening rapidly, with mass production already expanding in China, based on announcements from CATL, BYD, and others.

Overview of active materials in sodium-ion batteries

Cathode materials

• Layered oxides (e.g., NFM – NaNi₁ / ₃Fe₁ / ₃Mn₁ / ₃O₂)

  The highest energy density among SIB cathode materials, but there are trade-offs due to the higher cost from nickel content. These materials are analogous to NMC materials in the Li-Ion battery sector.

  The most common dopants include Mg, Ti, Cu, Zn, Ca to enable electrochemical stability and moisture exposure during manufacturing[5].

• Polyanionic cathodes (e.g., NFPP – Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) or NVPF – Na 3 V 2 (PO 4 ) 2 F 3 )

  Lower capacity and voltage compared to layered oxides, but better safety performance and lower costs. These materials are analogous to LFPs in the LIB space.

• Prussian blue analogues (e.g., PBA – NaₓMnFe(CN)₆)

  Material with the highest discharge rate in the sodium-ion space with discharge rates >10C[1]. The trade-off is that they have the lowest energy density SIB cathode.

Anode materials

• Hard carbon (HC)

  Dominant anode material in SIBs, with properties that depend heavily on the carbonaceous material precursor.

• Alloy materials (e.g., Sn, Pb, P)

  High energy density anode materials that alloy with Na, but undergo large volume changes during sodiation (>350%), resulting in poor cycle stability and lifespan[5]. These materials are analogous to silicon anodes in the lithium-ion space, but have a lower level of technological maturity.

• Anode-free designs

  The anode with the highest theoretical energy density among SIBs. However, like anode-free and solid-state LIB chemistries, they are the furthest from commercialization on this list, with significant safety issues to overcome in research.

Examples of the three most common SIB materials are shown in Figure 2, which graphically represents the first cycle voltage as a function of capacity.

Comparison of battery chemistry

The sodium-ion battery offers numerous advantages over lithium iron phosphate batteries and other batteries. Compared to lithium, sodium has a relatively lower chemical activity, making it less prone to thermal runaway or explosions during use. This stability makes sodium-ion batteries extremely safe during fast charging and capable of handling higher charging power. Sodium-ion batteries offer a wide operating temperature range, from -40 °C to 80 °C, making them suitable for applications in extreme weather conditions. The sodium reserve is 440 times greater than that of lithium; although the cost of sodium-ion batteries is higher than that of lithium batteries, it will decrease in the future and become an economical solution.

The main challenges facing SIB development

Despite significant advantages in terms of sustainability, costs, and supply chain, SIBs still face real technical obstacles. The biggest challenge is the low energy density of the cells, both volumetric (272 Wh/L) and gravimetric (134 Wh/kg), due to lower voltages and lower specific capacities compared to lithium-ion battery (LIB) materials. There are also challenges related to air stability and moisture absorption, depending on the active material used. Furthermore, NFM materials are currently expensive because they contain about 30% Ni, so the industry's expected trend is to reduce the nickel content in the coming years.

Additionally, there are challenges associated with the electrochemical stability window of the materials: they are limited to a lower full cell voltage due to the 0.3 V difference between Na/Na + vs Li/Li + [1]. This means that degradation reactions on the cathode side, such as oxygen release in the lattice, electrolyte oxidation, and transition metal dissolution, occur at a lower voltage compared to lithium-ion cells.

The promise of sodium-ion technology

Sodium-ion batteries are emerging as a viable alternative to lithium-ion batteries, particularly for large-scale energy storage. Current sodium-ion technologies follow three main paths: layered oxide, Prussian blue/white, and polyanion chemistry. However, traditional layered oxide and Prussian blue/white technologies present difficulties, including limited cycle life and reduced stability at high temperatures, making them less suitable for large-scale energy storage.

The battery with polyanion technology, in particular a sodium iron orthopyrophosphate cathode combined with a hard carbon anode. This approach offers significant advantages, such as higher round-trip energy efficiency, excellent low-temperature performance, and robust charge/discharge rate. These qualities position the battery as a game changer for industrial-scale storage solutions that require longevity, reliability, and safety.

Energy storage performance:

• Cycle life and capacity retention: at 25 °C and under 1P power conditions, it achieves a capacity retention of 94.2% after 4,000 cycles. Under optimized conditions, the battery is expected to exceed 20,000 cycles while maintaining a state of health (SOH) of 70%.

• Temperature resistance: at 45 °C, the battery demonstrates remarkable durability, retaining 92.5% of its capacity after 4,000 cycles, which is a performance increase of more than five times compared to conventional alternatives.

• Safety and reliability: Compliant with and exceeding the stringent GB/T 44265 standard for industrial-scale energy storage systems, the battery has undergone rigorous safety tests, including drop, crush, short circuit, overcharge, over-discharge, and thermal runaway assessments. In addition, it complies with GB/T 31485 standards and has successfully passed the nail penetration test, confirming its excellent safety credentials.

Unparalleled safety features

The commitment to safety is evident in the battery's design. The main safety features include:

• Extremely long 0 V shelf life: after six months of storage at 0 V, the battery maintains its full capacity without any degradation, operating efficiently as a brand new unit.

• No risk of sparks: even during assembly, if the anode and cathode were to accidentally short circuit, the battery eliminates the risk of sparks or electric shocks.

• Safe transport: the battery remains safe even under extreme transport conditions, such as crushing or overturning. There is no risk of combustion or explosion, ensuring safe handling and use.

Driving the future of energy storage

H2W™'s innovative approach to sodium-ion battery development consolidates its position as a leader in the energy storage sector. By addressing the critical challenges of large-scale energy storage, such as stability, efficiency, and safety, it is unlocking the immense potential of sodium-ion technology. The company's commitment to innovation ensures continued progress in energy storage solutions that meet the ever-evolving needs of the industry.

Conclusion

The launch of sodium-ion batteries marks a crucial moment in industrial-scale energy storage. Thanks to its cutting-edge technology and unrivaled safety features, H2W™ is paving the way for a more sustainable and efficient energy future. With the company preparing for mass production in 2025, the energy storage sector can rely on a reliable, high-performance solution, tailor-made to meet global energy demand.