“Rechargeable Sun Battery” Outperforms Lithium-Ion, Offering Latest Path to Solar Energy Storage
Researchers at UC Santa Barbara have developed a novel molecule capable of capturing solar energy and releasing it as heat on demand, demonstrating performance that surpasses traditional lithium-ion batteries. This breakthrough, detailed in a recent paper published in the journal Science, offers a potentially transformative solution to the intermittent nature of solar power.
Beyond Batteries: A Chemical Approach to Solar Storage
Unlike conventional solar panels that convert sunlight directly into electricity, this new technology focuses on storing solar energy chemically. This approach doesn’t rely on bulky batteries or extensive electrical grids, presenting a more streamlined and potentially scalable energy solution. The core of this innovation lies in a modified organic molecule called pyrimidone, a key advancement in the field of Molecular Solar Thermal (MOST) energy storage.
How it Works: A Molecular “Rechargeable Battery”
The pyrimidone molecule, inspired by components found in DNA, functions like a rechargeable battery, but instead of storing energy as electricity, it stores it within chemical bonds. When exposed to sunlight, the molecule twists into a high-energy state, effectively “charging” it. This stored energy can then be released as heat when triggered by a catalyst or a small amount of heat, allowing for on-demand energy retrieval. As doctoral student Han Nguyen explains, “The concept is reusable and recyclable.”
The process is analogous to photochromic sunglasses, which darken in sunlight and clear indoors. “That kind of reversible change is what we’re interested in,” Nguyen says. “Only instead of changing color, we want to use the same idea to store energy, release it when we need it, and then reuse the material over and over.”
Stability and Efficiency Through Computational Modeling
To understand the molecule’s stability and energy storage capabilities, the team collaborated with Ken Houk, a distinguished research professor at UCLA, utilizing computational modeling. The team prioritized a lightweight, compact molecule design, removing unnecessary components to maximize efficiency.
Impressive Energy Density and Practical Applications
The new molecule boasts an energy density of more than 1.6 megajoules per kilogram, roughly double the energy density of a standard lithium-ion battery (around 0.9 MJ/kg) . Researchers demonstrated that the heat released from the material was intense enough to boil water—a feat previously difficult to achieve in this field.
This capability opens the door for practical applications ranging from off-grid heating for camping to residential water heating. Because the material is soluble in water, it could potentially be pumped through roof-mounted solar collectors to charge during the day and stored in tanks to provide heat at night.
“With solar panels, you need an additional battery system to store the energy,” says coauthor Benjamin Baker. “With molecular solar thermal energy storage, the material itself is able to store that energy from sunlight.”
Looking Ahead
This research, supported by the Moore Inventor Fellowship awarded to Associate Professor Grace Han in 2025 , represents a significant step toward more efficient and sustainable energy storage solutions. The development of “rechargeable sun batteries” could play a crucial role in addressing the challenges of intermittent renewable energy sources and paving the way for a cleaner energy future.