Anodes and the future of energy density

Mar 13, 2019

We recently had the pleasure of presenting to a working group at the German Association of the Automotive Industry, VDA, in Berlin. The topic under discussion was Trends in downstream anode and battery markets, and the impact of these on cell formulation, energy density and future battery technology.

This edition of our EV Spotlight provides a summary of the main points from the discussion, if you would like to discuss any of the issues in depth please get in touch. Additionally, if you would like to receive a free copy of our new EV Energy Density Monthly Assessment simply email info@rhomotion.com and we will send one out to you.

We consider there to be the three main issues in anode technology that are likely to affect battery cell cost and energy density. These are the role of natural versus synthetic graphite, for which we are grateful for the input of Simon Moores at Benchmark Mineral Intelligence, the role of silicon and the development of solid state technology.

The key development for anodes in the short term is the level and rate of substitution of synthetic graphite for natural graphite. To date the level of substitution has been relatively slow compared to expectations. Most anodes now contain a blend of synthetic and natural material, at a ratio of roughly 65%-35%, but we assert that the rate of substitution is likely to grow as the quality of processed natural flake graphite increases and the market expands.  

Natural flake graphite is relatively cheaper and less energy intensive to produce than synthetic material, and, with a few exceptions, this energy is largely derived from coal. This poses both economic and corporate social responsibility costs, especially for a green technology such as EVs.  There is also limited new synthetic capacity being added, while there will be a marked increase in availability of natural flake graphite owing to a number of greenfield and brownfield capacity investment projects.

In the medium term, the role of silicon is a key issue for anode technology. R&D is ongoing for a silicon dominant anode which would theoretically provide a 20% increase in energy density over a conventional graphite anode. At present blending already takes place, and it is not uncommon for anodes to be composed of around 4-6% silicon, with swelling of the material the main stumbling block to the inclusion of more silicon. There are a number of companies in R&D stage with the silicon dominant anode, with commercialisation posited for 2023, which at this stage still seems relatively optimistic.    

The long term outlook for anodes takes in solid state, probably the highest profile issue in the space. Solid state technology introduces a lithium metal anode and a solid – likely polymer – electrolyte. Theoretically this could lead to a 70% increase in energy density combined with higher voltage and faster charging. The technology is early stage however, and lithium metal is a limiting factor in terms of its cost, availability and its reactivity. The reality is that when solid state arrives it will have to compete against a mature Li-ion battery technology, with a developed supply chain and significantly lower costs and higher energy density than we see today.