New battery technologies: steady progress away from Lithium
While the world is steadily transitioning towards using electric energy, a major stumbling block are batteries. As such, batteries don’t generate energy but act as energy buffers that absorb energy while being charged or deliver energy when being discharged. This looks simple but the reality is more complex. Battery cells are chemical-physical systems that must meet many criteria. While a high energy-density is one of the main objectives, the speed at which the energy can be charged or discharged defines its power density. The maximum power a battery can deliver is mostly temperature dependent as too high currents will damage the battery, impacting on its cycle life, or worse, can result in a thermal runaway. Secondary aspects are the availability of raw materials, the manufacturing yield in volume, the production cost which is dependent on the volumes that can be produced in a continuous automated production and last but not least the recyclability of the materials used.
Hence, all over the world, people are researching better and cheaper batteries. Some are looking at replacing the somehow problematic Lithium, Nickel and Cobalt raw materials, others focus on so-called solid state or quasi-solid state electrolytes. Almost daily, R&D labs or companies make announcements but the road from promising lab tests to full scale affordable volume production is long. It’s a process that takes years before full scalability at a market acceptabel pricing level is reached.
One of the promising alternatives for lithium-ion cells are sodium-ion cells. While they generally have a lower energy density, sodium is abundant, much cheaper than Lithium and poses no recycling issues. Steady progress makes them increasingly competitive offering a more sustainable solution.
New cells are now delivering upto 155 Wh/kg while other cells can deliver 50C sustained power rates. This makes them in creasingly a batter alternative. Cells can typically be discharged from -40 upto 60°C with the high current rates within 15 to 45°C. The charging capacity is typically from -10 to 45°C but at lower currents. As usual, no cell can deliver maximum values on all specifications. It’s always a trade-off between energy-density and power density. Note that sodium-ion cells are typically delivered in a prismatic format with relatively high capacities ranging from 50 to more than 200 Ah.
Applications for sodium-ion
Typical applications today are energy storage systems. As no lithium is used, this is the sustainable option. Other arguments are safety, the wide temperature tolerance and as less heat is generated, the cooling requirements are modest. Other applications are car starter batteries and urban electric vehicles.
Below some pictures of a 174 kWh high voltage sodium-ion battery installed in a busy urban environment.
How safe are polyanion sodium cells?
At Kurt.energy safety always has been one of our main concerns. This is the reason why we exclusively focus on hybrid supercapacitors. Recently we added the novel sodium-ion cells and batteries. We analysed manufacturer’s reports and claims and also did our own tests like overcharging and short-circuiting them.
So what does the literature tell us about polyanion sodium cells? These cells offer upto 6000 cycles and have acceptable parameters for many applications, without using lithium and other problematic materials.
Polyanionic sodium-ion (Na-ion) cathode materials are considered among the safest options for sodium-ion batteries due to their rigid structure and strong covalent bonding between transition metals and polyanionic groups, which provides excellent thermal stability and minimal volume change during Na⁺ insertion/extraction, thus reducing thermal runaway risk .
Key safety features of polyanion sodium cells
– Thermal Stability: Polyanion compounds exhibit strong covalent bonding (stronger than Metal-Oxygen bonds in layered oxides), resulting in the least thermal runaway behavior among cathode families . They also have a low internal resistance, reducing the heat build-up due to the current.
– Mechanical & abuse testing: Cells using polyanionic materials (e.g., Na₃V₂(PO₄)₂F₃) have passed rigorous tests, including overheating, overcharging, nail penetration, and short circuits, with no thermal runaway observed .
– Cycling stability: Excellent cycling stability. 6000 cycles and more and high thermal stability make them suitable for long-term use .
– Low risk of sodium plating: unlike hard carbon anodes (which risk sodium plating near 0–0.1 V vs. Na/Na⁺), polyanionic systems often use anodes with higher redox potentials (e.g., Ti-based anodes at 0.5–1.0 V), avoiding dendrite formation.
Comparison with other Sodium based Cathode Types
| Cathode Type |
Energy Density |
Thermal Stability |
Key Safety Notes |
|
|
|
|
| Polyanionic |
Lower |
Best |
Strong covalent bonding, minimal oxygen release |
| Layered Oxides |
Highest |
Poor |
Prone to oxygen loss and structural instability at high temperatures |
| Prussian Blue Analogs (PBAs) |
Moderate |
Moderate |
Risk of toxic HCN/cyanogen gas under extreme conditions |
Limitations & Considerations
– Lower energy density polyanionic materials trade energy density for safety, as their higher redox potential reduces specific capacity.
– Environmental concerns: Some polyanionic chemistries (e.g., vanadium-based) raise sustainability issues; research is ongoing to replace V with earth-abundant elements like Al.
– BMS and system set-up must still ensure that maximum current limits are observed, which are temperature dependent.
Conclusion
Polyanionic sodium cells are exceptionally safe, with robust performance under abuse conditions and minimal thermal runaway risk. Their primary drawback is lower energy density compared to layered oxides, but they are ideal for applications prioritizing safety and longevity .
Polyanion cells and batteries available from Kurt.energy
– 50 Ah, prismatic. Typical battery: 600V nom., 30 kWh, 5C capable dicharging, charging at 0.5C
– 160 Ah, prismatic. Typical battery: 48V nom., 7.68 kWh, 1C capable discharging, charging at 0.5C.
Contact us for specific requests.
Restructuring the company
Times are changing and so do companies. Our history goes way back when we founded Lancelot Research NV. Over the years Lancelot has acted as a holding company investing in spin-offs and research activities. Activities covered multi-processor DSP computers and 3D-radar but the focus was the development of a distributed RTOS for embedded systems using formal, read mathematical, methods. The result was a very clean, orthogonal set of services with well defined distributed semantics and no duplication of code. It’s architecture uses modular and scalable packet switching while the services are programmed on top of so-called “hub” entities. The RTOS is more that only a real-time kernel. It’s an development appoach that has its roots in the CSP Process Algebra, but turned into a pragmatic yet design driven approach for modular and concurrent real-time programming. Tools and API were designed to redice programming errors but also to increase productvity while reducing software maintenance.
Now called VirtuosoNext, the RTOS is very small (measured in KBytes) so that it complety runs inside a processor’s cache memory providing high performance. Nevertheless, it provides fine grain state partitioning and real-time fault tolerance, which is often not available from other RTOS. Using a graphical front-end, the user can develop his application using Tasks and Hub services (which still present themselves as the traditional RTOS services like semaphores and mailboxes) on a cross-development PC. Next the source code can be recompiled for the target single or multiprocesssor system whereby Tasks and Hub entties are then allocated onto the various processing nodes of the target system as if it was a virtual single processor. The executable code for each node is then generated. VirtuosoNext supports single processor systems as well multi/-many core systems with homogenous or heterogenous CPUs. One of the latestBSP was developed for a many-core A9 with FPGA SoC from Xylinx. VirtuosoNext is made available under an Open Technology License complemented with BSP development services. VirtuosoNext was the first product commercialised by Altreonic NV, which was the main spin-off of Lancelot.
Besides the RTOS, Altreonic also developed a unique meta-modeling framework for supporting domain-independent “trustworthy” embedded systems engineering, called GoedelWorks and the novel ARRL (Assured Reliability and Resilience Level) criterium. Later on a small drive-by-wire electric vehicle was developed which resulted in refocussing on developing safe and application specific battery systems. As a result, Altreonic exclusively uses hybrid supercapacitors and recently, sodium-ion battery cells.
The company has now been restructed with its VirtuosoNext and battery activities being transferred back to Lancelot Research NV as the legal entity. Altreonic and Kurt.energy are still in use as tradenames.
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