• A new paper could give energy scientists a better way to design supercapacitors.

  • Capacitors are a circuitry tool, and supercapacitors use them in a battery-like design.

  • Batteries move energy using chemical reactions, and these can deteriorate over time.

Much of the modern world relies on battery charging—from the world’s billions of mobile devices to electric cars, scooters, and assisted bicycles. Inside these rechargeable batteries, ions are passed from one side to another to spend the charge, then reversed in order to recharge.

Special materials called supercapacitors could blow this huge battery market wide open, turning one steady drip of battery charging into a showerhead. In newly published research, scientists propose a new model for studying supercapacitors, giving other researchers a better way to study how a different battery paradigm might work.

In a typical battery, there are extra electrons in circulation in the form of ions—particles with a different number of electrons than that substance has in its neutral state—inducing a positive or negative charge overall. Ions are packed into a battery and forced through a material that skims off the electrons, which become electrical current as they flow out of the battery’s terminal. Eventually, the supply of electrons is depleted, and the battery is dead. In a rechargeable battery, those ions can regain electrons and return to the start, ready to have those new electrons skimmed off in a new cycle.

A supercapacitor is a newer concept that combines the design of a battery with the physics of a capacitor. A capacitor has two layers of conductive material with an insulator (like, for example, glass) between them. This insulator causes energy to build up on either side, but not pass through. In a supercapacitor design, energy instead accumulates on the surface in an electric field that holds the electrons in place. This difference is key: the particles aren’t joining and being stripped from atoms and molecules as part of a chemical reaction, which saves energy and prevents wear over time.

The thing is, everything in science must be codified in a way that lets researchers compare like with like when needed. That means we need to emulate supercapacitors and run the numbers in exactly as much depth as we can with traditional batteries.

“Due to the high computational demands of direct numerical simulations and a lack of interfacial boundary conditions for reduced-order models, the current understanding of [surface-based] charging is limited to simple geometries,” the researchers explain. In other words, just like video game consoles, the computer simulations of supercapacitors must be built one generation at a time.

Ankur Gupta of the University of Colorado Boulder led this new paper, published now in peer reviewed Proceedings of the National Academy of Sciences of the United States of America (PNAS). Gupta and the other two authors used existing formulae to build an efficient way to model thousands of charge-storing surface pores in just a few minutes.

Gupta explained in a University of Colorado Boulder statement that his team used existing knowledge of flow through pores—like the study of water filtration—and applied that knowledge to the flow of energy over a porous material. They also considered Kirchoff’s law, which is a foundational principle that underpins the study of current and circuitry design. In their system of ions flowing over a system of many pores, the law had to be modified to account for the proverbial chaos.

With the new model in hand, the team hopes that other researchers will be able to continue to design and test new supercapacitors. Gupta also hopes that contributing to this “somewhat underexplored” area will help energy scientists continue to improve our future.

“The primary appeal of supercapacitors lies in their speed,” Gupta said in the university statement. “So how can we make their charging and release of energy faster? By the more efficient movement of ions.”

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