Sodium-Ion Battery - Battery Design

Sodium-ion batteries operate analogously to lithium-ion batteries, with both chemistries relying on the intercalation of ions between host structures. In addition, sodium based cell construction is almost identical with those of the commercially widespread lithium-ion battery types. However, sodium-ion batteries are characterised by several fundamental differences with lithium-ion, bringing both advantages and disadvantages:

Advantages:

Environmental abundance: Sodium is over 1000 times more abundant than lithium and more evenly distributed worldwide.
Safety: Sodium-ion cells can be discharged to 0V for transport, avoiding thermal run-away hazards which have plagued lithium-ion batteries.
Low cost: Sodium precursors (such as Na₂CO₃) are far cheaper than the equivalent lithium compounds.
Four major families of materials for cathode chemistry options:
Cathode materials can be synthesized from more sustainable transition metals such as Fe, Cu or Mn.

Disadvantages:

Sodium-ion cells have lower energy densities than lithium-ion. This is due to sodium being significantly heavier and larger than lithium, as well as Na⁺/Na having a higher reduction potential than Li⁺/Li.
Sodium-ion technology is not as well established as lithium-ion.

Materials
Cell Characteristics
Application

Sodium-Ion Battery Materials

Many of the battery components in both sodium-ion and lithium-ion batteries are similar due to the similarities of the two technologies. This post provides a high-level overview for the constituent cell parts in Sodium-ion batteries.

Hard Carbon Anodes in Sodium Ion

Emerging battery technology – promising cost, safety, sustainability, and performance advantages over current commercialised lithium-ion batteries^1,2.
Advantages:
- widely available
- inexpensive raw materials
- rapidly scalable technology
- meeting global demand for carbon-neutral energy storage solutions^3,4.
Adding metals would increase the overall energy density, but results in volumetric changes leading to failure.

optimization of hard carbon for sodium ion - poster

Sodium-ion & Semi-Solid Technologies

Desay introduced a SSSB reaching 420 Wh/kg, positioning itself between conventional LIB and ASSB.

Key characteristics:

1000+ validated cycles
Passes nail penetration & 300°C thermal tests (no fire, no explosion)
Wide temperature adaptability
Core Technology Stack:
- Lean electrolyte fast-ion pathways
- In-situ dense interface engineering
- Intrinsic + active safety system
- Proprietary solid electrolyte membrane (thin, high conductivity, flame-resistant)

Cell Characteristics

Sodium Ion Cell Characteristions

An energy density of 100 to 160 Wh/kg and 290Wh/L at cell level.
A voltage range of 1.5 to 4.3V. Note that cells can be discharged down to 0V and shipped at 0V, increasing safety during shipping.
20-30% lower cell BOM cost than LFP.
A wider operating temperature than lithium-ion cells (-20°C to +60°C).
Typical Energy efficiency 92% at C/5.

HiNa 32140 OCV curves versus other chemistry

Open Circuit Voltage

The OCV for the two cell datasets that we have to date are quite similar. The hysteresis between charge and discharge is small.

However, you can see that the voltage swing versus SoC is more significant than the other chemistries.

Lifetime

Over-voltage Charging
Presence of Hydrogen
- causes irreversible degradation of α-NaMnO₂ when used as the cathode in Na-ion batteries [1].
Defects in the Cathode Atomic Structure
- these form during the steps involved in synthesizing the cathode material. These defects eventually lead to a structural earthquake in the cathode, resulting in catastrophic performance decline during battery cycling [2].

Hina NaCR32140-MP10 sodium ion cell 0.5C Charge / 0.5C Discharge and 98% capacity retention after 500 cycles.

Reduce the DoD to 90% and even at 2C / 2C cycling the capacity retention is 96% after 3850 cycles, expected life to 80% SOH is >25,000 cycles.

Temperature Performance

Low temperature performance in sodium ion batteries is often discussed as an electrolyte issue, but in practice the bottleneck is much more interfacial. Below -20°C, charge transfer resistance increases sharply and the SEI on hard carbon anodes becomes both chemically unstable and kinetically limiting.

Application

Sodium Ion Battery Pack

This low cot battery technology is approaching fast with lots of announcements.

Achieving 120Wh/kg at pack level.

The battery cell energy density, both volumetric and gravimetric will preclude the use of sodium ion in most vehicle applications. Except perhaps the very smallest packs where sodium can offer an advantage in terms of cost. Although, at the moment it is very early days for the maturity of the supply chain and the cost will be relatively high.

Sodium ion cells for 24V commercial vehicle starter packs appear to be an interesting option with capability down to -40°C. eg CATL 24V Naxtra.