A team of researchers in China has developed a new hybrid electrolyte that could significantly improve supercapacitors, energy storage devices known for rapid charging and high durability. The discovery could have big implications for electric vehicles and power grids.
Supercapacitors store energy differently from regular batteries. Instead of using chemical reactions, they rely on the separation of ions. This allows them to charge and discharge far more quickly. They’re already used in technologies like regenerative braking and grid stabilisation. But so far, they’ve faced serious limitations.
Most supercapacitors rely on water-based electrolytes. These are safer and cheaper than organic alternatives, but they break down at low voltages, usually below 1 volt. They also struggle with extreme temperatures, freezing below 0°C and boiling at 100°C. These drawbacks have limited their use in EVs and other demanding environments.
The Chinese research team tackled this problem with a new electrolyte mix. Their formula combines water, an ionic liquid called EMIMNTf₂, and potassium trifluoromethanesulfonate (KOTf). Normally, water and ionic liquids don’t mix, but the potassium salt helps restructure the water’s hydrogen bonds, letting the liquids combine.
This change prevents the water from breaking down, allowing the supercapacitor to run at 3.37 volts, nearly three times the usual voltage. It also remains stable from 0 to 100°C, which makes it far more useful in real-world conditions.
The prototype also proved durable: it kept 81.8% of its capacity after 10,000 charge-discharge cycles at 60°C. By comparison, commercial supercapacitors can lose up to 30% of their capacity after just 5,000 cycles.
Energy density was another bright spot. While still not at the level of lithium-ion batteries, the new device came close; it also retained the fast charge-discharge benefits that make supercapacitors unique.
However, challenges remain. The new electrolyte is still in the lab stage. Scaling up for industrial production will require new methods, and existing EV systems would need major redesigns to handle the higher voltage.
Experts say the breakthrough is promising, but point to the need for cost-effective manufacturing before it can compete with existing battery technologies. If those hurdles are overcome, the new system could reduce dependence on lithium, offering a more sustainable and faster-charging option.
The research is part of China’s broader push into energy storage innovation. Since 2015, the country has filed over 75% of global patents related to supercapacitors. This latest advance supports global efforts to improve grid storage and electrify transport using cleaner, more efficient technologies.
While it won’t replace lithium-ion batteries any time soon, this hybrid system could pave the way for new combinations that blend the strengths of both battery types.
