Solar power is cheap and clean, but it still has a timing problem. Your roof can be producing electricity at noon, then you are back to the grid after dinner when the air conditioner is still fighting that sticky summer heat. That mismatch is one reason energy storage has become so important.
A team at Nanjing Tech University in China says it has a new way to bridge that gap. In a peer reviewed Electrochimica Acta paper, the researchers describe a “solar redox flow battery” that both captures light and stores energy in liquid electrolytes, reaching an average solar to electricity efficiency of about 4.2% in lab testing.
What if the solar panel and the battery were the same machine?
A battery that charges directly from light
The device is designed to photo charge without an external electrical bias, meaning the light does the charging work. Under simulated sunlight from a xenon lamp, the system charged using light alone and was then discharged like a battery.
The paper reports stable discharge for more than 15 cycles, which is early stage but enough to show the concept works as an integrated system. Corresponding author Chengyu He told pv magazine that anthraquinone derivatives are “favored materials for energy storage” in solar redox flow batteries.
Why 4.2% is not the whole story
Most commercially available solar panels are roughly 20% efficient at turning sunlight into electricity, so 4.2% can sound underwhelming. But this number is measuring a combined “capture plus store plus output” pathway, not a bare solar cell.
The authors point to earlier anthraquinone-based solar redox flow batteries that ranged from well under 1% to a few percent in solar-to-output electricity efficiency, with stability often harmed by very acidic or very alkaline conditions.
In that light, getting above 4% while avoiding the harshest chemistries is a meaningful research step, even if it will not lower your electric bill tomorrow.
The chemistry bet is about durability
A quieter detail is the operating environment. The device runs at pH 12, and the paper argues this helps keep ferrocyanide stable and reduces photoelectrode corrosion compared with stronger alkaline systems.
The electrolyte choice is also pragmatic. The authors describe 2,6‑DBEAQ as a functionalized form of 2,6‑DHAQ that is six times more soluble at pH 12, and they cite prior work showing the redox pairing can maintain an open-circuit voltage above 1 V.
Business and defense are chasing the same thing
The timing is not random. The International Energy Agency says the global lithium ion battery market exceeded $150 billion in 2025, while also warning that supply risks are rising as batteries spread across cars, grids, and data centers.
That pressure is why long duration options, including flow batteries, keep getting attention. A U.S. Department of Energy assessment highlights a key advantage of flow batteries, which is that energy capacity can scale with tank size while power is set by the cell stack, making them a natural fit for microgrids and backup power.
For military installations, resilience is not a buzzword, it is a planning requirement. Department of Defense microgrid design guidance says teams should evaluate renewable generation and energy storage options early in any project, alongside mission needs and life-cycle costs.
What to watch next
So what comes next for a “solar battery” like this? Efficiency has to rise, cycle life needs to jump from tens to thousands, and the system has to prove it can operate outside the lab, not just under a carefully controlled lamp.
It’s not there yet, but the direction is hard to ignore. If researchers can keep improving integrated solar storage devices, we may eventually see cleaner and safer systems that make solar power feel less like a daytime product and more like an all-day utility.
The study was published on ScienceDirect.
