A striking reaction
A team from the University of Oxford, working as part of a Faraday Institution Industry Sprint, have developed a class of sodium-ion cathode materials that store charge reversibly on the oxygen atoms as well as metal atoms of the crystal structure. This could pave the way for either more energy dense cells with properties that rival lithium iron phosphate (LFP), providing a route into low cost automotive or e-mobility, or decreasing battery costs for static energy storage applications for the grid.
Having proved the concept at the pouch cell level, the team is now scaling up production via a Royce MATcelerate Zero grant, and is aiming to launch a spin out to commercialise the technology.
Cathode limitations
Sodium-ion batteries are an emerging battery technology, with promising cost and safety benefits when compared to lithium-ion. They can also operate effectively across broad temperature ranges and use earth abundant elements, meaning their supply chains will be less constrained than Li-ion.
However, the performance of sodium-ion cells is constrained by the properties of the cathode, making the search for new types of cathode materials a potentially high impact area of fundamental research.
| By the numbers | |
|---|---|
| 10 g | Demonstrator pouch cells created by the sprint team |
| 1 kg | Manufacturing goal for the next stage of the cathode material project |
A Faraday Institution Industry Sprint, led by Dr Robert House at the Department of Materials, University of Oxford, aimed to exploit recent advances in the understanding of oxygen redox materials to develop new cathode materials for Na-ion batteries.
Dr House explains,
Sodium-ion has a good anode – hard carbon – but we’re trying to find alternative cathode materials that can boost the energy density of sodium-ion batteries so that it can match or even out-compete lithium-ion.”
The potential to use oxygen redox materials as cathodes was a core part of the Faraday Institution CATMAT project investigating new cathode materials for lithium-ion batteries. The understanding of oxygen redox materials developed through the CATMAT project was applied to sodium-ion cathodes, leading to the discovery, which has since been patented. The team was investigating the mechanisms of oxygen redox and what promotes stability of those materials, an understanding that would be needed to increase the battery cycle life, which would unlock the potential use of these materials in commercial batteries.
Dr House, also a member of the CATMAT team, explains further,
Redox reactions are how a battery cathode stores its energy, but they are usually only carried out by the transition metal atoms in the battery cathode’s structure. This limits the amount of energy you can store. We were looking at how to also involve the oxide ions in the redox reaction without causing the structure to become too unstable. Oxide ions are a key part of the crystal structure, but would typically be electrochemically inert.”
By charging the oxide ions, which would usually be “dead weight” in the cathode, the researchers believed cathode capacity, and therefore battery energy density, could be significantly improved.
A promising pair
The CATMAT project had discovered a single example of a sodium-based material that could undergo oxygen redox in a very reversible way. The task for the sprint team was to determine whether the concept of reversible oxygen redox could be applied to a range of different sodium-ion cathode compositions.
Rob continues,
Our aim was to pursue two distinct generations of material. One with very high energy density, which will be important if sodium-ion is going to break into markets such as e-mobility and compete with lithium iron phosphate. The other was very low-cost materials, targeting use cases such as battery energy storage on the power grid.
“We identified a whole range of compounds that exhibited the same redox properties along those two routes and then started to explore some other, commercially relevant properties such as stability and ease of handling. These are important things to consider when you start judging whether a material is going to be a good all-rounder for a cathode.”
Keeping commercial relevance in mind, the team chose production routes involving fast sintering (a process where powdered material coalesces into a solid mass by means of heating) and reasonably low energy intensity processes.
After identifying three promising cathode materials, Rob and his colleagues worked with Professor Magda Titirici at Imperial College London to create several demonstrator pouch cells incorporating 10 grams of the new material, showcasing the new cathodes alongside Imperial hard carbon anodes that are being developed as part of the Faraday Institution NEXGENNA project.
The pouch cell is an important milestone because it’s something you can put in front of a battery pack manufacturer as a tangible outcome of industrial relevance.”
Dr House hopes to secure private investment and spin out a company that will develop and license the cathode materials. In the meantime, the team has secured follow-on funding from the Henry Royce Institute, the UK’s national institute of advanced materials research and innovation. The funding falls within the MATcelerate ZERO programme that backs projects with potential to deliver new materials that could aid the clean energy transition.
The Royce funding will be used to demonstrate the scale up of production of the material.
One of the big steps is to move towards continuous methods of manufacturing the cathode. We’ve already shown it can be done in 10-20 gram batches, and part of the MATcelerate Zero project is to work with AMBIC at CPI to demonstrate production of up to 1kg using techniques that could be used at an industry-relevant scale, using precursor materials that industry would use.”
The Advanced Materials Battery Industrialisation Centre (AMBIC), funded by the Faraday Battery Challenge (and delivered by Innovate UK) is a dedicated environment to design, develop, test and commercialise new battery materials.
A case study published in September 2025.