Sodium Ion Battery: Complete Technical Guide, Technology Comparison and Advantages of Heiwit's Layered Oxide Cells

The chemical reactions described here are those used in the Heiwit range of sodium-ion batteries.

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 has built and tested a high-capacity sodium-ion battery, using 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.

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: over 6,500 cycles at 90% DoD with 70% residual capacity (NA-48V210Ah, layered-oxide cells) (estimated life of the cells we use)

• Good thermal stability

• Discharging down to -25 °C, charging from 0 °C

• 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 an Asian supplier; the battery module has passed the UN 38.3 transport tests.

The reasons are manifold:

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

• Over 6,500 cycles at 90% DoD with 70% residual capacity (NA-48V210Ah, layered-oxide cells): with one full cycle a day this corresponds to about 18 years of operation. It is a calculation, not a forecast: actual lifetime depends on temperature, depth of discharge and average state of charge.

• High security: passed vibration, shock, short-circuit, overcharge and extrusion tests, with no fires or explosions during testing.

• Voltages similar to LiFePO4 cells: the Heiwit battery, however, works only with Heiwit inverters.

• Operation at low temperatures: the NA-48V210Ah battery discharges down to −25 °C and charges from 0 °C upwards; in the cold the available capacity decreases.

• No cobalt or lithium in the cells.

5. Technical parameters of Heiwit (Layered Oxide) cells

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

• The NA-48V210Ah battery discharges down to −25 °C and charges from 0 °C upwards. It must be installed indoors.

Safety performance

• Reduced, though not zero, thermal risk: in the short-circuit, overcharge, drop, extrusion and thermal shock tests declared by the cell manufacturer, no fire or explosion occurred.

Endurance test

• 6,500 cycles at 0.5C/0.5C and 90% DoD, residual capacity above 70% (NA-48V210Ah, layered-oxide cells)

• This is a test result, not a guarantee: the Heiwit warranty is 10 years and is not expressed in cycles.

6. Comparison of SIB technologies

6.1 Comparative Table

6.2 Advantages of our cells

• More energy in less space: compact cells, also suitable for retrofit. A Heiwit inverter is always required. In retrofit applications, it is connected to the AC line of the existing system.

• Life Cycle: over 6,500 cycles (NA-48V210Ah, layered-oxide cells) in the endurance test, with 90% discharge and residual capacity above 70%.

• Stability and security: in the abuse tests the cells did not go into thermal runaway.

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

7. International certifications and standards

Reference standards for our cells:

• UN 38.3 (security for transport)

• GB/T 31484/5/6 (Chinese standards on cycle life, safety and performance of traction batteries)

• 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 temperatures: the NA-48V210Ah battery discharges down to −25 °C and charges from 0 °C upwards

• Sustainability and price: sodium is an abundant raw material and less exposed to lithium price shocks. The cost of storage should be compared per kWh cycled

• Security: in short-circuit and crush tests, no thermal runaway and no fire

9. Frequently asked questions about sodium ion batteries

Are SIBs interchangeable with lithium batteries?
No. The working voltages are close to those of LiFePO4, but the Heiwit battery works only with Heiwit inverters. It is not a replacement for a lithium battery connected to an inverter of another brand.

How many cycles do they last?
In the endurance test, after 6,500 full cycles at 90% DoD the residual capacity remained above 70% (NA-48V210Ah, layered-oxide cells). This is a test result, not a guarantee: the Heiwit warranty is 10 years and is not expressed in cycles.

Are they safe?
The thermal risk is reduced, not zero. The cells have passed safety tests with no fires or explosions. Safety nevertheless depends on the complete system: cells, BMS and installation to a professional standard.

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: over 6,500 cycles at 90% DoD with 70% residual capacity in the endurance test

• CEI 0-21 certified system (Virgo + battery, TÜV SÜD) and already operating in real installations

• 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, with documented performance and a reduced, not zero, thermal risk. The layered oxide cells selected by Heiwit are a suitable solution for those looking for lithium-free, long-life storage.

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.