The key raw material discussed is graphite, particularly natural graphite. The bottleneck arises because, even though natural graphite can be sourced globally, the processing capabilities are concentrated in China. This creates a dependency on China for upgrading the raw materials, which complicates efforts to localize the supply chain and reduce reliance on Chinese processing. This issue is highlighted around timestamp 00:10:38 when it is mentioned, "all of the processing is in China and that's our bottleneck." Additionally, there's an emphasis on the need to develop the right technologies to process these materials domestically around timestamp 00:07:15.