Imagine a future where batteries don’t just power your devices or vehicles—they also help clean the air. It sounds futuristic, but scientists are edging closer to making this a reality with lithium-carbon dioxide (Li-CO₂) batteries. These next-generation energy storage devices are gaining attention for their potential to store renewable energy while removing CO₂ from the atmosphere—a promising development in the fight against climate change.
How It Works
Li-CO₂ batteries function by absorbing carbon dioxide during discharge, converting it into lithium carbonate—a white, powdery substance. This not only helps reduce greenhouse gases but could also be crucial for future space missions, particularly to Mars, where the atmosphere is about 95% carbon dioxide.
The challenge? Making them commercially viable. Recharging has been a particular hurdle, but recent breakthroughs are pointing in the right direction.
From Accident to Innovation
The story of the Li-CO₂ battery begins with a bit of serendipity. About ten years ago, a team of US and French researchers studying lithium-air batteries stumbled upon something unexpected. They found that the tiny amount of CO₂ in the air was interfering with their experiments—creating unwanted lithium carbonate. But instead of dismissing it as a nuisance, they dug deeper and discovered that CO₂ could actually improve the battery’s charge capacity. This insight paved the way for a new kind of battery that uses carbon dioxide as a key ingredient.
The Chemistry Behind It
At the heart of the Li-CO₂ battery is a clever chemical reaction. The battery's positive electrode is designed to let in CO₂ gas, which dissolves into the liquid electrolyte and reacts with lithium ions. This reaction involves the exchange of four electrons, significantly more than the one electron exchanged in a typical lithium-ion battery. That translates into much higher energy potential.
Theoretically, one kilogram of catalyst material in a Li-CO₂ battery could absorb around 18.5 kilograms of CO₂. That’s roughly the amount emitted by a car driving 100 miles, suggesting a single battery could potentially offset a full day’s worth of emissions.
The Technical Roadblocks
Despite the promise, these batteries are not without their problems. Most prototypes degrade after fewer than 100 charge-discharge cycles—far short of the 1,000–10,000 cycles achieved by standard lithium-ion batteries. Recharging also remains energy-intensive because breaking down lithium carbonate requires significant input, a phenomenon known as "overpotential".
Using noble metal catalysts like ruthenium or platinum can reduce this energy demand, but their cost and rarity make them impractical for mass production.
A Breakthrough from Surrey
Researchers at the University of Surrey have proposed a promising alternative: a catalyst made from caesium phosphomolybdate. It’s cheaper, can be made at room temperature, and offers improved performance. Their version of the battery managed 107 cycles and stored 2.5 times more energy than a conventional lithium-ion cell. They also managed to bring the overpotential down to 0.67 volts—still above the ideal target, but a significant improvement.
Their next step is to replace caesium with a more affordable component, as the phosphomolybdate is the true active ingredient. They're also working on studying how the battery functions in real time to better understand and improve its performance.
Real-World and Extraterrestrial Potential
The research team is also testing the battery’s ability to operate under different CO₂ pressures. So far, all tests have been under standard conditions (1 bar), but the goal is to bring that down to 0.1 bar—making it feasible to use the batteries in vehicle exhaust systems or home heating flues to capture CO₂ on the go.
If the battery can work at just 0.006 bar, it could operate on Mars. And at 0.0004 bar—the concentration of CO₂ in Earth’s atmosphere—it could help capture atmospheric carbon in a wide range of settings.
What Comes Next?
To become commercially viable, the technology must overcome a few key hurdles: increase the number of recharge cycles, lower overpotential below 0.3 volts, and eliminate reliance on rare elements. Researchers are exploring improved casing designs to prevent the electrolyte from drying out and examining how to maintain a steady CO₂ flow during operation.
If these efforts succeed, Li-CO₂ batteries could one day power vehicles, homes, and even space missions—all while actively reducing carbon dioxide in the environment.
Source: The Conversation - Batteries that absorb carbon emissions move a step closer to reality – new study
