IDTechEx asks if silicon anodes are the key to mass EV adoption

Optimisations in cell and battery pack designs, alongside the use of higher nickel NMC and NCA cathodes, have led to steady improvement in battery energy density over the past 10-15 years. The energy density limit from current design and material iterations has largely been maximised. However, a promising contender is emerging on the horizon to offer a step-change improvement – silicon. IDTechEx forecast the market for silicon anode material for Li-ion batteries to exceed $24 billion by 2034.

This article, by Dr Alex Holland, Research Director at IDTechEx, draws from the new IDTechEx report, ‘Advanced Li-ion Battery Technologies 2024-2034: Technologies, Players, Forecasts’, which includes analysis on the latest in silicon anode developments.

Silicon anode performance benefits

Silicon has a theoretical capacity of nearly 3600mAh/g (at room temperature), offering the possibility to significantly boost energy densities by replacing graphite, which is used as the anode material in the vast majority of Li-ion batteries. By replacing graphite, which has a capacity of approximately 360mAh/g, with silicon, cell-level energy densities in excess of 400Wh/kg and 1000Wh/l become feasible, with the potential to nearly double the energy density of state-of-the-art commercial cells in 2024. This leap in energy density could translate into electric vehicles with twice the range or electronic devices with twice the runtime.

But the benefits of silicon extend beyond just capacity and energy density. Many silicon anode companies are reporting improved power and fast charging capabilities, an increasingly important performance metric for electric vehicles, as well as other applications such as power tools or consumer devices. Additionally, the more positive voltage of silicon compared to graphite helps reduce the risk of lithium plating, enhancing battery safety, another increasingly important concern for the industry.

Commercialisation efforts ramping up

Currently, silicon oxides can only be used at relatively low weight percentages, <10%, but tens of companies, both large and small, are racing to develop advanced silicon anode materials that can enable higher silicon percentages in batteries. Silicon-dominant compositions remains the aim for a number of players. The battery industry has taken notice of silicon's potential. IDTechEx estimate that over $4 billion of investment has gone into silicon anode startups. Some of this is now starting to go toward the expansion of manufacturing capabilities, capacities, and supply chains. Importantly, the materials and solutions being developed by some of these companies are also starting to be qualified and deployed. Sila Nano have had materials used in the Whoop fitness wearable, Amprius have deployed batteries in drones and high-altitude pseudo satellites (HAPS), while Lightning Motors will offer e-motorcycles using Enevate’s technology. Automotive OEMs have also taken note of the promise of silicon anodes, with the likes of Daimler, Porsche, and GM investing and partnering with silicon anode companies.

Cumulatively, funding into silicon anode startups and companies has exceeded US$4 billion since 2010. Source: IDTechEx

Challenges remain

However, challenges remain to the widespread commercialisation of silicon beyond its use as an additive. Silicon's significant expansion during cycling can lead to issues such as excessive electrolyte consumption, electrode pulverisation, and loss of electrical contact, hence the use of silicon at relatively low percentages in the anode. Significant effort has gone into overcoming these hurdles, and data being reported suggests that cycle lives of up to 1000 cycles are attainable, making silicon broadly suitable for electric cars.

Beyond cycle life, shelf life remains a concern, while in the short-medium term, silicon anode materials will most likely continue to come in at a price premium over graphite on a $/kWh basis. This may restrict their deployment to applications where price sensitivity is lower, such as high-end electric vehicles, military applications, or some electronic devices.

Conclusion

In conclusion, advanced silicon anode materials hold immense promise for improving key aspects of battery performance, but challenges such as cycle life, shelf life, and, importantly, cost must be addressed for widespread adoption. Nonetheless, the deployment of higher percentage silicon content anodes in various applications looks imminent. Increasing scale and continued innovation also provide optimism for driving down the costs of silicon-based anode materials, making them accessible for important mass-market EV segments.