Silicon Anodes Can Improve EV Battery Density and Extend Range Without Cost Increase
By 2030, electric vehicles (EVs) are projected to account for approximately one-third of all vehicles sold globally, driven by surging consumer demand for better performance and reduced individual carbon footprints.
Better performance will be achieved with next-generation batteries that ideally reduce the amount of critical materials used in traditional lithium-ion batteries (LiBs), e.g., lithium, graphite, nickel, etc., and they are expected have lower carbon footprints, increased efficiency, and a wider-range of applications. These batteries come in numerous chemistries including silicon-based.
Silicon Anodes as a Solution
Silicon anodes are gaining increasing popularity in electric vehicles—but wait! Aren’t they already in them? Yes, in fact Tesla, a former Global Cleantech 100 member, had been working to implement silicon in their EVs as early as 2015.
Over $3B has been invested in silicon anode technologies over the past decade and approximately $1B has been invested since 2021.
Silicon has a relatively high theoretical-specific capacity, meaning it packs more energy in the same amount of space compared to graphite and other metal alloys, which results in increased battery performance. Still, in practice it is only used in small amounts (up to 15% reported) and may result in only small energy density increases.
Experimental reports of a 20-40% increase in energy density of silicon anode-based LiBs have been observed. However, this experimental maximum has historically been impractical at scale due to silicon’s tendency to expand and contract during lithiation or a charge cycle.
An over 400% expansion of silicon is reported which is impractical at scale in EVs considering there is limited room in the battery cell and the automotive industry seeks to lighten the weight of them. Expansion results in poor conductivity, electrolyte consumption and can cause the silicon lattice to collapse.
Silicon Can Cause Rapid Degradation of the Anode and Shorten the Lifespan of LiBs -- Until Now
Recent developments have optimized silicon by controlling expansion and increasing its conductivity. Well-designed void spaces by means of reliable, scalable processes that are compatible with current manufacturing processes (drop-in solutions) are now available.
When processed into micro/nanometer-sized particles, silicon can be carefully fine-tuned with polymer and metal coatings that allow expansion in a controlled manner. In some cases, these coatings can increase the conductivity of silicon and improve the energy density. Innovators like Sila Nanotechnologies, Group14 Technologies, and Ionblox are just a few examples of startups taking this approach.
Paraclete Energy’s polymer matrix mitigates the typical problems when working with silicon. With their polymer matrix, the SEI forms on the outside of the particle, so the electrolyte never comes into contact with the silicon. Using a polymer matrix allows for over 70% active silicon material per particle vs. others using 12% per particle. Their silicon is therefore the material with the highest energy density for lithium-ion batteries. Paraclete Energy is no longer limited to 12% silicon, an incremental improvement over SiOx, but their polymer matrix is a nearly 8x improvement over graphite.
E-Magy produces high-purity nanoporous fused particles that are nanowire-like for silicon dominant anode manufacturers. E-Magy has demonstrated swelling of less than 1%, overcoming the most significant barrier to commercialization.
Similarly, nanotubes and nanowires act as scaffolds that allow silicon particles room to expand within a finite space so as not to destroy the lattice. OneD Battery Sciences and Amprius are just a couple innovators who grow silicon nanowires that are combined with graphite-based LiBs. Amprius claims their technology increases energy density by up to 50%, resulting in a driving range of up to 547 miles.
SiliB uses 100% silicon nanowires in a single step manufacturing process, eliminating the need for graphite, catalysts, binders, and any other additives used in traditional anode manufacturing. SiliB’s process does not require use of the traditional manufacturing equipment.
But these innovators aren’t stopping at silicon anode material development and manufacturing. Amprius, StoreDot, Solid Power, and Enevate, are a few examples of component manufacturers that have begun producing their own batteries ready to be implemented in EVs.
What Are Automotive Manufacturers Thinking?
These innovative solutions have caught the attention of major automotive players like Mercedes-Benz, GM Motors, Toyota, Hyundai and Porsche. These automotive players have engaged in many ways from licensing IP, purchasing materials, funding pilot plants, research and development, and acquisitions.
In 2022, Sila Nanotechnologies announced they will incorporate their silicon anode technology in the electric Mercedes-Benz G-Class vehicle by mid-decade. Likewise, Porsche subsidiary Cellforce Group, announced they will incorporate Group14 Technologies’ silicon anode in their lithium-ion batteries to implement in Porsche EVs.
Governments Jump on Board
These innovations have also caught the attention of government agencies across the globe that seek to reduce their carbon footprints on the roads.
- Through the Inflation Reduction Act, the U.S. Department of Energy (DOE) invested an astounding $2.8B in domestic battery manufacturing projects including $787M in silicon anode materials.
- The UK’s Faraday Battery Challenge invested $33M in silicon anode technologies in 2023.
- InnovFin Energy Demo Projects and the European Investment Bank (EIB) invested approximately $32M in Finnish startup, LeydenJar Technologies, ‘Plant One’, a 100 MWh capacity silicon anode foil plant to launch in 2026.
This government action is needed to help innovators overcome financial barriers and provide stability and security on their path to market. Furthermore, government engagement encourages private investors to join. We expect to see an increase in private investors joining to enable competition and push innovation even further.
Continued Innovation in Silicon Anode Technologies is Furthering the Battery Revolution
Solid Power’s EV batteries combine their silicon anode technology with solid-state sulfide electrolyte batteries and a commercially available lithium nickel manganese cobalt (NMC) cathode. Solid-state batteries have an even higher energy density range than silicon-based LiBs and endless potential applications. When the solid sulfide electrolyte is combined with silicon, Solid Power claims their batteries increase the energy density of LiBs by 50-100%.
But this increase in energy density could potentially be further improved through cathode innovation, signaling future generations of these technologies with enhanced performance is yet to come. This also indicates that the innovation push should not all land on the shoulders of the anode.
By improving upon commercially available binders, electrolytes, cathodes, etc., batteries can be further optimized. For example, lithium-metal solid-state batteries could increase the energy density to over 150% compared to traditional LiBs; however, these remain commercially unavailable.
Silicon anode technologies will continue to grow in popularity, and we will see an increased number of significant investments from private investors. Innovators have announced they will begin penetrating the market through consumer electronics in 2023 and have plans to integrate in EVs by 2026 or sooner.
We anticipate those who can vertically integrate across the battery supply chain will have an advantage and ultimately win out over those who simply license or sell anode materials. Furthermore, we expect innovators that have begun optimizing the chemistries of the remaining battery components in addition to the anode will gain further control over the market.
Buff Lopez, Research Analyst at Cleantech Group, discusses the trends and innovations in battery materials and silicon anodes.
