New Liquid Material Can "Bottle" Sunlight with Twice the Energy Density of Lithium Batteries
Technical Principle: Inspired by Sunburn Mechanism
A research team led by Grace Han, an assistant professor at the University of California, Santa Barbara, has developed a novel material capable of capturing sunlight and storing it in chemical bonds, releasing the energy as heat when needed. This technology falls under the field of molecular solar thermal (MOST) energy storage. The findings have been published in the journal Science.
The team drew inspiration from the DNA damage caused by sunburn. When exposed to excessive ultraviolet light, adjacent bases in DNA form a specific damaged structure, which further twists into a "Dewar isomer" upon additional UV exposure. The researchers realized that this isomer essentially acts as a molecular battery, with its spring-like heat-releasing effect precisely matching the behavior they were seeking.
Working Mechanism: Reversible Structural Change Enables Energy Storage and Release
The team created a molecule capable of reversibly storing and releasing energy by synthesizing this structure. This specially designed liquid contains photoresponsive, modified pyrimidone molecules. Upon exposure to sunlight, each molecule undergoes a reversible structural change, shifting from a low-energy configuration to a high-energy, strained configuration.
Think of each molecule as a microscopic spring. Sunlight "winds" the spring, forcing the molecule to twist into an energy-rich Dewar isomer. The molecule can maintain this state for months or even years without releasing the energy. When triggered by a catalyst such as heat or acid, the molecule quickly snaps back to its original shape, releasing the stored energy as heat.
Han Nguyen, a doctoral student in the research group and the paper’s first author, explains that this essentially functions as a rechargeable solar battery that can store sunlight and be recharged repeatedly.
Performance Breakthrough: Energy Density Exceeds Lithium Batteries
In energy storage tests, the pyrimidone system achieved an energy density of approximately 1.6 megajoules per kilogram (MJ/kg), roughly twice that of standard lithium-ion batteries (about 0.9 MJ/kg). In comparison, previous studies on norbornadiene achieved a maximum energy density of around 0.97 MJ/kg, while azaborane reached only 0.65 MJ/kg.
In addition to being repeatedly charged and discharged without degrading the molecular structure, the molecule can store energy for extended periods. The Dewar isomer is extremely stable, with a calculated half-life of 481 days at room temperature. This means energy stored in summer could remain available for use during winter heating.
Practical Validation: Released Heat Sufficient to Boil Water
Professor Han’s team achieved a key breakthrough by translating high energy density into practical results. The research demonstrates that the heat released by this material is sufficient to boil water — a significant accomplishment previously difficult to realize in this field. The researchers noted that achieving boiling water under ambient temperature and pressure is a major achievement.
Because the system consists of dissolved molecular solutions, it is highly scalable and easy to integrate into existing systems. Increasing storage capacity simply requires using more of the solution, which can be pumped, transported, and stored using conventional pipes — a feature that has led to its description as a "bottle of sunshine."
Application Prospects: From Off-Grid Heating to Seasonal Energy Storage
This technology opens the door to a wide range of practical applications, including off-grid heating for camping and hot water supply for homes. Since the material is water-soluble, it can be pumped into rooftop solar collectors. During the day, sunlight converts the molecules into their energy-rich form, which is then stored in a water tank for nighttime heat delivery.
Benjamin Peaker, a doctoral student in Han’s lab and co-author of the paper, points out that while using solar panels requires additional battery systems for energy storage, with molecular solar thermal storage, the material itself stores the solar energy.
Another promising application is seasonal energy storage: the system could be charged during summer and the stored heat used for heating in winter. The Dewar isomer also has potential for electricity generation by integrating it with thermoelectric generators and heat engine cycles.
Future Challenges: Still a Distance from Practical Application
Despite the breakthrough, there remains a gap before this system can be applied to practical home heating. Researchers need to explore molecules capable of absorbing a broader range of the solar spectrum and converting more efficiently into the activated state to further enhance the technology’s practicality.
Sources:
[1]https://news.ucsb.edu/2026/022384/ucsb-scientists-bottle-sun-liquid-battery
[2]https://newatlas.com/energy/molecular-solar-thermal-energy-storage-liquid/
[3]https://www.science.org/doi/10.1126/science.aec6413
[4]https://arstechnica.com/science/2026/02/dna-inspired-molecule-breaks-records-for-storing-solar-heat/
[5]https://www.universityofcalifornia.edu/news/scientists-bottle-sun-liquid-battery