Introduction

In recent years, the world of energy storage has seen the emergence of a technology destined to radically change the balance: the sodium ion battery (SIB, Sodium-Ion Battery). Although this technology has been known experimentally for decades, it is finally ripe for commercialisation thanks to new chemistries, material improvements and performance that is now comparable to conventional lithium-ion batteries.

Heiwit is among the first manufacturer in Europe to have developed and tested a high-capacity sodium-ion battery on a large scale, adopting cells with layered oxide cathode of the latest generation. In this technical article, we take an in-depth look at SIB technology, compare the main cell families on the market today, explain why we have chosen layered oxide chemistry for our products, and present actual data from our cells, which are certified for industrial storage applications.

1. What is a sodium ion battery

The sodium ion battery is a rechargeable electrochemical device in which the sodium ion (Na+) plays the same role as in lithium ion batteries is occupied by the lithium ion (Li+). In both technologies, the ions move between the anode and cathode during charging and discharging, generating a potential difference that is used to provide electrical energy.

Why sodium?

• Sodium is abundant (the 6th most abundant element on Earth, more than 1000 times more than lithium).

• It is distributed everywhere (no dependence on strategic mining as with lithium).

• It poses no risk of scarcity or speculation on raw materials.

• It reduces costs and price volatility throughout the supply chain.

2. Structure of a sodium ion battery

A sodium ion battery consists, in principle, of the same key elements as a Li-ion:

• Anode (typically “hard carbon” obtained from biomass)

• Cathode (different chemistries available: layered oxide, polyanions, Prussian Blue Analogues, manganese/iron oxides, etc.).

• Electrolyte (liquid solution based on sodium salts in an organic solvent)

• Separator (polymer membrane)

Each material and chemistry adopted strongly influences the performance, safety, durability and final cost of the battery.

3. The main cathode technologies in sodium ion batteries

Today, the market mainly offers three major families of SIB cells, each with its own merits and shortcomings:

3.1 Layered Oxide

Description
Layered oxides (Layered Oxide) represent the technological frontier of SIB batteries. In this chemistry, the cathode consists of a metal oxide with an alternating layered structure, into which sodium ions are inserted and extracted during charge and discharge cycles.

Examples:

• NaNixCoyMnzO2 (different variants with Ni, Co, Mn)

• NaFeO2 and derivatives

Main features

• High energy density: reaches and exceeds 140 Wh/kg (some models go up to 160 Wh/kg)

• High cyclic duration: up to 6,000 cycles (our tested cells)

• Good thermal stability

• Excellent performance even at low temperatures

• Lithium-like working voltage (between 2.5 and 3.8 V nominal)

• Low cost, no critical metal

3.2 Polyanions (NASICON, Na3V2(PO4)3, NaFePO4, Na2Fe2(SO4)3, etc.).

Description
Cathodes based on polyanionic compounds, such as phosphates, sulphates or other compounds, with a very stable crystal structure.

Features

• Very long life cycles

• Very high thermal safety

• Generally lower energy density (100-120 Wh/kg)

• Lower working voltage

Typical usesBackup, stationary applications, telecom.

3.3 Prussian Blue Analogues (PBA, hexacyanoferrates)

Description
Cathodes composed of “Prussian blue”-like structures (complex ferrocyanides/metallocyanides).

Features

• Low-cost cells

• Excellent cyclical stability

• Excellent performance at low temperatures

• Modest energy density (80-110 Wh/kg)

• Limited working voltage

Typical useslarge storage, low-cost systems.

4. Why Heiwit uses Layered Oxide cells

After a long phase of research, testing and validation, Heiwit chose the layered oxide chemistry for its sodium ion batteries, relying on a high-capacity prismatic cell produced by a leading Asian supplier, certified to all major international standards (UN 38.3, GB/T 31484/5/6, QB/T 2502-2000).

The reasons are manifold:

• Real energy density of over 140 Wh/kgvalue among the highest of all currently available SIBs.

• Life cycles greater than 6,000 (with retention >70%)Therefore, the battery can be used for at least 15 to 20 years even in daily cycles.

• High securityPassing all safety tests (vibration, shock, short circuit, overload, extrusion, etc.) without risk of fire or explosion.

• High compatibility with existing BMSs and voltages similar to LiFePO4 cells, so retrofitting is easy in many applications.

• Excellent performance at low temperaturesover 75% of nominal capacity already at -30°C, thus ideal for European markets.

• Absence of cobalt, nickel and lithiumtotal sustainability.

5. Technical parameters of Heiwit (Layered Oxide) cells

The data are extracted from our prismatic cell NaFP71/173/204CY-210:

• At -20°C: capacity > 60% of nominal

• At -30°C: capacity > 75%

• At -40°C: capacity > 60%

Safety performance

• No risk of fire/explosion as a result of: short circuit, overload, drop, extrusion, thermal shock (tests passed according to UL1642 and GB380318).

Actual duration

• 6,000 cycles at 0.5C/0.5C, retention >70%

• Even with deep cycles (DoD 90%)

6. Comparison of SIB technologies

6.1 Comparative Table

6.2 Advantages of our cells

• More energy in less spaceperfect for retrofit or 1:1 replacement with LiFePO4 modules.

• Life Cyclemore than 6000 cycles means more than 15 years of use even under stressful conditions.

• Stability and securityNo risk of thermal runaway, even in case of severe abuse.

• Zero cobalt, nickel and lithium100% “battery of the future”.

7. International certifications and standards

Our cells comply with the main global standards:

• UN 38.3 (security for transport)

• GB/T 31484/5/6 (storage battery performance and safety)

• QB/T 2502-2000 (general standard lithium batteries, compatibility)

• JBT 11137-2011 (battery assembly)

All cells are tested on real charge/discharge cycles, tested for resistance to:

• Vibrations

• Mechanical shocks

• Overcharge/overdischarge

• Short circuit

• Thermal shock (up to 130°C)

• Extrusion

• Free fall from 1 metre

8. Performance of Heiwit sodium ion batteries in real applications

Thanks to the characteristics of layered oxide cells, our sodium ion batteries are ideal for:

• Stationary storage systems (BESS, C&I, grid, residential)

• Integration with photovoltaic systems

• Off-grid and micro-grid

• Cycle-intensive industrial applications

The key advantages over lithium are:

• Stability to deep cyclesSIBs do not suffer from the DoD (Depth of Discharge) limitations of LFPs

• Performance at low temperatureslithium drops dramatically below zero, our SIBs retain more capacity than the 60% even at -20°C

• Sustainability and pricesodium ion cell costs less for the same installed kWh, is not subject to raw material price shocks

• Securityno runaway risk, no fire, even in the event of a short circuit or crushing

9. Frequently asked questions about sodium ion batteries

Are SIBs interchangeable with lithium batteries?
Yes, the working voltage and BMS logics are compatible with LiFePO4 modules, which allows retrofitting without major modifications.

Do they really last 6,000 cycles?
Yes, all our tests confirmed superior retention of the 70% after 6,000 complete cycles, which is superior to many lithium batteries on the market today.

Are they safe?
Yes, they pass all international safety tests, with no risk of fire or explosion.

How much do they cost compared to lithium?
Already today, the cost per kWh is about 20% lower, and will fall further with mass production.

Do they suffer from self-discharge?
No, the self-discharge rate is similar to that of the best lithium-iron-phosphate (LiFePO4) cells.

10. Why choose a Heiwit sodium ion battery

Heiwit has chosen to bet everything on this new frontier:

• Sodium ion battery produced and assembled to the highest quality standards

• Layered Oxide Cells of the latest generation, with the best parameters of density, durability and safety

• Headquartered in Europe and already operational in real plants

• Direct technical support from our research laboratory

We are convinced that sodium-ion batteries represent the future for energy storage, especially in Europe, where sustainability of the supply chain and independence from critical raw materials are now a strategic priority.

11. Conclusions

La sodium ion battery is already a reality: reliable, high-performance, safe and affordable. The layered oxide cells selected by Heiwit represent the top of the line for those seeking clean energy and long-life storage without compromise.

Whether you are an installer, a storage system designer, an energy-hungry company or simply interested in new technologies, our solutions are ready for the energy transition.
Contact us for detailed data sheets, lab tests, installation examples and dedicated offers.

Heiwit: the future of energy goes through the sodium ion battery.