"3D battery" design twists together for split-second charging
Most batteries are made up of a cathode on one side and an anode on the other, with a nonconducting separator between them. Now, engineers at Cornell University have developed an unusual new structure that intertwines the components together in a swirling shape, which they say lets the device recharge in a matter of seconds.
The Cornell team's new battery architecture is based on a complex, porous shape known as a gyroid, which has previously been used to make the most of the 2D wonder material graphene. The new battery also used thin films of carbon (although not thin enough to become graphene), built into a gyroidal shape using a process known as block co-polymer self-assembly.
This carbon gyroid forms the anode of the battery, and contains thousands of pores each about 40 nanometers wide. These pores were then coated with a separator layer about 10 nanometers thick, and then a sulfur cathode was added. The final ingredient to fill up the last bit of those pores is an electronically-conducting polymer called PEDOT.
Each of these pores has everything it needs for energy storage and delivery, making them almost like tiny little batteries in their own right. But by spreading them out across the huge surface area of the gyroid shape, the new architecture can pack in a far better power density than conventional battery designs can allow.
In practical terms, that means the battery can be recharged in a matter of seconds, or even faster, the researchers say.
"This three-dimensional architecture basically eliminates all losses from dead volume in your device," says Ulrich Wiesner, lead researcher on the study. "More importantly, shrinking the dimensions of these interpenetrated domains down to the nanoscale, as we did, gives you orders of magnitude higher power density. In other words, you can access the energy in much shorter times than what's usually done with conventional battery architectures."
As promising as it seems, the team acknowledges that the new design isn't without its flaws. While the battery is charging and discharging, the sulfur expands but the PEDOT layer doesn't, so the latter will gradually wear away over time.
"When the sulfur expands, you have these little bits of polymer that get ripped apart, and then it doesn't reconnect when it shrinks again," says Wiesner. "This means there are pieces of the 3D battery that you then cannot access."
The team is working on fixing that problem, and is currently seeking a patent on the proof-of-concept as it stands.
The research was published in the journal Energy and Environmental Science.
Source: Cornell University