Liam Critchley outlines how the overwhelming number of commercial battery systems using nanomaterials involve graphene. There are good reasons for this – it has some of the best electrical, structural and stability properties of all nanomaterials, which makes it ideal for battery systems. He argues the battery industry should be looking towards small nanomaterials.
Batteries are a staple technology of modern-day society and lithium-ion batteries have become the dominant architecture throughout the world – not just in high-end technologies such as electric vehicles (EVs), but also in low-cost consumer goods. Lithium-ion batteries are ubiquitous today and it is going to take a big innovation in other battery systems to displace them, especially when there are many advancements focusing on improving existing lithium-ion systems.
While many people are thinking about ‘big’ innovations, the future of battery systems could well be ‘small’. Nanomaterials have become disruptive materials in many industries, and different nanomaterials are now being added into different battery systems. Some of these are in existing lithium-ion battery systems to improve their battery performance and stability, while other approaches are creating new batteries that belong to less explored and less commercialised battery systems.
When it comes to talking about nanotechnology in high-end electronics, there is often a narrative that it is the ‘technology of the future’. The nanomaterials industry has been around for many years and the ‘future’ is now, with many different nanomaterial-enhanced batteries being available on the commercial market and being used in end-use consumer products. It is no longer a technology confined to the academic laboratory and they are starting to have an impact in the real world. This article showcases what is going on with the commercialisation of nanomaterial battery systems.
Graphene-enhanced lithium-ion systems
When it comes to nanomaterials having a commercial impact on batteries, few have been bigger than graphene. Graphite has been widely used as the cathode material, so it has been long known that graphene layers are stable during the everyday function of an electrochemical cell – there are obviously property and mechanistic differences between the use of graphene and graphite but, at the fundamental atomic-single-layer level, they have the same structure. This has led to graphene being used in different parts of an electrochemical cell, including in both electrodes.
There are many reasons why graphene has gathered a lot of interest compared to other nanomaterials. First off, its electronic properties are well documented; with an electrical conductivity of up to 100mS/m, a charge carrier mobility of around 15,000cm2 v-1 s-1 and a charge carrier concentration of up to 1011–1012cm2, it is an excellent material for battery systems.
Once you couple these electrical properties with a high thermal, chemical and structural stability, and a high thermal conductivity (for heat dissipation) of 3000–5000Wm-1K-1, graphene has a range of properties that outperforms many other materials.
Naturally, there is some variation based on the type of graphene used, with some graphene types having better properties than others. But graphene has presented battery manufacturers with an opportunity to improve on the performance and stability of lithium-ion batteries for many different industries. The cost of integrating graphene is generally not high, due to only needing a very small amount of it to bring about improvements.
So, there have been many academic advancements over the years, but what many people do not realise is that there is a raft of commercial graphene-enhanced batteries on the marketplace today that are based on lithium-ion architectures.
When it comes to lithium-ion batteries, one of the hottest areas at the moment is EV batteries. Many types of battery have been proffered for EVs but, like many areas of consumer technology, lithium-ion batteries have so far won the race. Graphene has also penetrated this market. The biggest development in graphene EV batteries globally has come out of China where GAC Group are now using graphene lithium-ion batteries in their Aion V electric cars which are on the road today. Graphene is also used by Ford in its vehicles – but as a sound damper, not in batteries. The Aion V signalled the first real-world consumer use of graphene EV batteries.
Another example of recent innovation in the lithium-ion EV space has been from Nanotech Energy, who are creating graphene-enhanced batteries for electric cars and e-bikes. Incidentally, it also calls its graphene battery ‘the super battery’. This is still a relatively new development, and little is yet known of performance, but it looks as though a number of industries are being targeted.
But it is not all about EVs. One of the recent developments in 2023 came from CAT, which has developed a 5Ah 18V battery pack for use with its power tools. Like the other examples above, it is a lithium-ion battery that has been enhanced with graphene. So far, it has been marketed for use with their hammer drill but, as many battery packs are interchangeable in power tools, we could see more product lines come out with the same battery system in the near future.
Other graphene battery systems
Naturally, a lot of the efforts towards integrating graphene into batteries has been in the form of lithium-ion batteries because they are the most dominant battery in the marketplace with the highest level of consumer trust (if you ignore the not-so-common EV and phone battery fires over the years).
So, it makes sense to target the biggest market and try to improve on the status quo – because it is well-known that lithium-ion batteries only became so popular because of the trade-off between battery performance and long-term stability, as there are many other battery architectures with a much higher theoretical energy density.
Many of the batteries beyond lithium-ion have struggled to make big dents in the market. Manufacturers are now trying to leverage the energy density properties of other battery architectures and use the inherent stability of graphene to make them more commercially viable.
Like lithium-ion systems, there is a number of commercial products and industry prototypes on the market (or planned for market soon). One of the interesting things about these graphene batteries is that the target markets are a little more interesting and not all of them are aiming to disrupt the lithium-ion market, as some want to carve inroads into other market applications such as space technology.
Going into space
Speaking of space technology, this is an area that has been explored by the US company Lyten. It has been working with the US government to create graphene-based batteries for the space sector and prototypes have already been created for small satellite applications. Beyond this, Lyten is also targeting the EV market as well. One of the key developments here is that it is using graphene to commercialise lithium-sulphur batteries, which have long struggled to be commercialised due to the polysulphide effect – where long intermediate molecular chains of lithium and sulphur discharge from the cathode and short circuit the battery.
By using graphene, Lyten has managed to supress the surface reactions at the cathode and drive reactions towards shorter chained Li2S compounds rather than the longer Li2S8 and Li2S6 chains that are typically formed – so the small scale of nanotechnology is already helping to provide a solution to some of the old commercialisation challenges in the battery space.
The Australian company, Graphene Manufacturing Group, is also taking a unique approach by creating graphene-enhanced aluminium-ion batteries. Prototypes of small aluminium-ion battery pouches have been created by the company, but this is a recent development that only came to light towards the end of 2023. It has the potential to be a unique graphene battery architecture with anticipated storage capacities of 500-1000mAh.
Another unique development from 2023 was the announcement that the Canadian company, Hydrograph, and the Sri Lankan company, Celyon Graphene, are using graphene to improve the performance of lead-acid batteries. While lead-acid batteries have been around for many years, the partnership aims to improve the dynamic charge acceptance (ability to absorb electrical charge) by up to 47% compared to existing commercial systems. They are still at the prototype stage, but will hopefully be another graphene battery commercial development to hit the market soon.
Silicon anode commercialisation
Graphene may grab the headlines and take the lion’s share of the commercial nanotechnology-enabled batteries on the market, but nanotechnology has enabled something to be done recently that has been talked about for an age but has never really manifested in any commercial sense. That is, the manufacturing of a commercially-feasible battery that uses a silicon anode.
Silicon has long been touted as a potentially great electrode material based on its high theoretical density. But electrical conductivity properties are not everything if a battery system is to go commercial. For many years, silicon anodes have struggled to penetrate the market and manufacturers have failed to bring a stable silicon anode to the market.
The reason behind the challenges of silicon are due to the volumetric changes (swelling and expansion) that the anode undergoes during the charge/discharge cycles. This volumetric change leads to the destabilisation of the anode and the SEI layer, causing the anode to break down very quickly during use. This has been a challenge for many years because manufacturers and researchers have been looking to bulk silicon materials (like they do for many electronics), when in fact, they should have been looking at something smaller. Yes, it is nanoscale silicon that has now enabled the first commercially viable silicon-based anode to come to market.
This innovation has come from the US company Sila Nanotechnologies and was first announced back in 2022. Using silicon nanoparticles as the anode – built up together into a functional anode rather than using a bulk piece of silicon – it has been able to develop an anode that can cope with the volumetric changes during charge/discharge due to having a much higher degree of porosity than bulk silicon anodes.
These batteries are still in development, but functional prototypes have attracted significant interest. They are set for mass production this year and commercial use in 2025, but one of the most significant developments with these electrodes is that Mercedes wants to use them to create EV batteries for its electric G-Class SUVs. While these silicon batteries are still being developed, nanotechnology has created an incredible opportunity to create silicon-based batteries, and initial estimates are that the energy density could be 20–40% greater than lithium-ion batteries that use traditional graphite anodes.
Global graphene manufacturing
The overwhelming number of commercial battery systems using nanomaterials involve graphene in one form or another. There are good reasons for this – it has some of the best electrical, structural and stability properties of all nanomaterials, which makes it ideal for battery systems. A lot of time, money and collaboration have gone into building a global graphene manufacturing industry.
We are often thinking about the next big thing but, like many areas of electronics looking to materials and processes to create smaller material systems, the battery industry should be looking towards small nanomaterials to bring about performance, stability, and miniaturisation benefits (depending on the application). A lot of it is likely to be around the use of graphene, but nanomaterials have also been able to create new unique commercially viable systems like silicon anodes. They are unlikely to be the last innovative area of battery and electrode design that comes out thanks to nanomaterials.
