I have been previously working with different organic electronics applications, such as organic photovoltaics and organic transistors. Both have been commercialized, by companies like ASCA and Flexenable. It is great to see that it has been possible to scale up the production of these unique materials and applications, which can help to increase sustainability of the electronics industry and enable new shapes and appearances for the devices.

Our team is currently working with organic battery materials in the ongoing FinnCERES project, funded by the Research Council of Finland. However, I had not found any company who has commercialised the production of organic batteries until I visited the Battery Show in Detroit last October. There, I heard a keynote talk by Mike Nagus from LiNova Energy. His talk was one of the highlights of the show for me, as it was great to see that it is possible to produce organic cathode active materials in a reliable way.

What is an organic battery

Organic materials are carbon-containing compounds and batteries already contain several of those, for example as binders. However, an organic battery usually refers to a cell where the cathode active material, or in some cases both electrodes, are organic.

In a conventional Li-ion battery, the cathode active material is an inorganic compound, such as lithium iron phosphate (LFP) or lithium nickel manganese cobalt oxide (NMC). In an organic battery, this inorganic electrode material is replaced with an organic one. However, the electrolyte may still contain Li-based or other metal-containing salts.

The most common anode material in batteries is graphite, which is not organic, even though it is a crystalline allotrope of carbon. This is since carbon should have bonds with hydrogen or other elements to be classified as organic. Organic batteries may use a graphitic anode, but they could also have a metallic or other type of anode. Usually, an organic battery is not 100% organic.

Note also that organic is not the same as renewable or biobased. Organic materials can be biobased, but they can be also made from fossil sources.

Benefits of organic cathode materials

To be clear, let’s focus only on the organic cathode active materials. Their main benefit is that they are not mined and can be produced from abundant materials. In addition, they can be produced with a significantly lower carbon footprint when compared to the traditional inorganic options.

Organic materials can also offer other benefits, such as flexibility. As most of the organic cathodes are not that prone to cracks, they could be used in applications where the battery needs to cope with bending or even stretching. Due to their light weight, organic batteries may also provide high gravimetric energy density.

In general, it is good to have different options for battery materials. This way we are not too dependent on one material, which helps in producing enough batteries for multiple purposes and overcome issues with material availability, sustainability and price.

Challenges

As every battery material, organic materials have their challenges and limitations too. This is why we can’t have a one-size-fits-all solution for energy storage.

One of the challenges of organic cathode active materials is their tendency to be soluble in organic solvents. They may easily dissolve into the electrolyte, which reduces the cycle life. Luckily, there are several promising ways to handle the solubility issues. It is e.g., possible to bind the active materials into a polymeric backbone to prevent dissolution.

Low volumetric energy density is another limitation. Organic materials are not as dense as inorganic ones, and they can’t be packed into a very small volume while storing high amount of energy. Organic batteries are thus suitable for such applications where there are no strict volumetric size limitations for the battery.

A third challenge is their low electronic conductivity. Organic cathode materials often require using high amounts of conductive carbon additives to have good enough conductivity for practical applications. This decreases the energy density of the battery further as the ratio of the active material to additives is not optimal.

Different organic cathode materials

There is a great variety of organic cathode active materials and I’m still learning to understand their differences and properties. We have been mainly working with organic radical compounds in our team, but they are just one group of materials.

Hailong Lyu at al. list the following different types in their review: conductive polymers, organosulfur compounds, organic radical compounds, organic carbonyl compounds, and organic imide compounds.

In addition, I very much recommend reading the paper by Jan Bitenc at al. as they provide a nice and critical status update about organic cathode active materials. And even more importantly, they give clear guidelines how to analyse such materials correctly, which will help to compare and understand the results in a reliable way.

Conclusions

I’m a polymer chemist & physicist by training and finalised my PhD about conducting polymers 15 years ago. It has been great to be part of and follow the development of organic electronics from lab to industry. Organic photovoltaics are already at high technology readiness level and now we are starting to see the same thing happen with organic batteries. They won’t replace the Li-ion batteries or other inorganic materials, but they have great potential to be used in parallel with other battery types. We can select which materials to use based on the application requirements.

There are still many challenges to be solved before we see organic batteries in real applications, but I’m optimistic. For example, computational methods can help to design the molecules in the best possible way, which will speed up the development. And some companies are emerging to the field as well, as we saw in the Battery Show.

PS. If you are planning to visit the Battery Show in Detroit this year, I highly recommend visiting the awesome bookstore “John K. King Used & Rare Books”. It was fantastic! I bought a novel called “The Small Mine” from there (tried to find something energy/battery related 😊) and could have stayed there for hours if I would have had more time.