New Electrode Design Could Boost Supercapacitor Performance

Mechanical engineers from the UCLA Henry Samueli School of Engineering and Applied Science and four other institutions have designed a super-efficient and long-lasting electrode for supercapacitors. The device’s design was inspired by the structure and function of leaves on tree branches, and it is more than 10 times more efficient than other designs.

The electrode design provides the same amount of energy storage, and delivers as much power, as similar electrodes, despite being much smaller and lighter. In experiments it produced 30 percent better capacitance — a device’s ability to store an electric charge — for its mass compared to the best available electrode made from similar carbon materials, and 30 times better capacitance per area. It also produced 10 times more power than other designs and retained 95 percent of its initial capacitance after more than 10,000 charging cycles.

Their work is described in the journal Nature Communications.

Supercapacitors are rechargeable energy storage devices that deliver more power for their size than similar-sized batteries. They also recharge quickly, and they last for hundreds to thousands of recharging cycles. Today, they’re used in hybrid cars’ regenerative braking systems and for other applications. Advances in supercapacitor technology could make their use widespread as a complement to, or even replacement for, the more familiar batteries consumers buy every day for household electronics.

New Electrode Design Could Boost Supercapacitor PerformanceStructural characterization of CNT/GP micro-conduits. a Schematic illustration of CNT/GP micro-conduits in a leaves-on-branchlet nanostructure on CC substrates for high-performance supercapacitor electrodes (Note that the yellow shaded areas in the schematic indicate the selected areas to be magnified). b Bare CC substrate at low magnification (inset shows the surface of a single carbon fiber). c Uniform coverage of CNT micro-conduits on carbon fibers at low magnification. d A close-up of CNT micro-conduits on a carbon microfiber. e A CNT/GP micro-conduit in a heart shape. A single CNT decorated with many GPs at high magnification (inset shows GPs on CNT micro-conduit array walls). g TEM image of the hierarchical structure. h High-resolution TEM image of a petal emerging from a nanotube. i Comparative Raman spectra of CNT micro-conduits and CNT/GP micro-conduits on CC substrates. Scale bars: b 500 μm (inset: 3 μm), c 300 μm, d 10 μm, e20 μm, f 300 nm (inset: 2 μm), g 100 nm, h 10 nm. Nature Communications (2018) doi:10.1038/s41467-018-03112-3

Engineers have known that supercapacitors could be made more powerful than today’s models, but one challenge has been producing more efficient and durable electrodes. Electrodes attract ions, which store energy, to the surface of the supercapacitor, where that energy becomes available to use. Ions in supercapacitors are stored in an electrolyte solution. An electrode’s ability to deliver stored power quickly is determined in large part by how many ions it can exchange with that solution: The more ions it can exchange, the faster it can deliver power.

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