Lithium-ion batteries have been the leading choice for electric vehicles and battery energy storage systems, but they contain critical minerals that are vulnerable to supply chain disruptions. To address this issue, researchers at MIT have been developing complementary energy storage solutions, including sodium-metal batteries. However, sodium metal is highly reactive, making it challenging to achieve long-term stability and fast cycling. A new study published in the journal Joule shows how this dilemma can be addressed by finding the right electrolyte for this battery system. The researchers used an AI-guided algorithm to design 100,000 candidate molecules and then narrowed down the pool to 200 candidates. After experimental tests, they found a clear winner, a solvent called DMFSA, which was both the smallest and the best. This work addresses one of the most persistent challenges in battery research: improving battery performance at high charging and discharging rates without sacrificing long-term stability. By carefully tailoring the size of solvent molecules, the authors demonstrate a new design strategy that could enable lower-cost, higher performance batteries. Blogger's Review: The discovery of the DMFSA solvent is a significant breakthrough for sodium-metal batteries. With the potential to challenge lithium-ion batteries' dominance, this technology could lead to more efficient and environmentally friendly energy solutions. As energy storage technology continues to advance, we can expect more innovative and sustainable solutions to emerge.