The University of Illinois in Champaign/Urbana is still developing awesomely quick-charging batteries – but now with a little twist. The latest innovation from Professor Paul Braun’s research team looks just like an average Li-Ion battery on the outside, but the cathodes include 3-D nanostructures which allow the battery to rapidly charge and discharge without diminishing capacity in the process.
“The system we’ve developed has a number of applications,” says Braun, professor of material science and engineering. “Many capacitors don’t store much energy, and can discharge it very quickly. However, they don’t charge as quickly. Batteries can store quite a lot of energy, but they cannot deliver particularly quickly and require a great deal of time for charging.”
The second disadvantage of the standard battery – whether lithium ion (Li-Ion) or nickel/metal hybrid (NiMH) – is that each time the battery charges and discharges, its capacity decreases. As a rule of thumb, the quicker the charge/discharge process, the faster battery capacity deteriorates, according to Braun.
A battery which retained capacity while charging quickly would be useful for a number of electronics, particularly devices such as laptops, high performance lasers, defibrillators, and electric cars. Braun is especially optimistic regarding uses for EV batteries – currently the range and charging time are seen as major limits for potential EV buyers. “With the new method, it will be possible to charge the EV as quickly as one could fill up a tank of gas in a gas-powered car, and without causing problems for the batteries,” says Braun.
The key to developing such a battery is the new 3-D structure which Braun’s team is developing. First, a surface is coated with tiny spheres so that a sort of grid is formed. Then, the space between the spheres is filled with metal. Next, the spheres are melted or dissolved to create a 3-D porous framework, much like a hard little sponge. Once the spheres are gone, the remaining spongelike framework is electropolished, a process which evenly etches the surface of the framework and expands the pores. Finally, the frame is coated with a thin film of active material. The result is a bi-continuous electrode structure with tiny links, allowing the lithium ions to move very quickly through the conductive metal framework.
There’s no word yet on when Braun’s nifty three-dimensional bi-continuous ultrafast-charge and -discharge bulk battery electrodes will be commercially available (if ever), but further information for the technically minded is available at nature nanotechnology.