While everyone wants their online purchases to arrive on their doorsteps ASAP, sometimes there just aren't enough humans to do the job. That's where robots come in. And you have to power the robots somehow. Enter this tiny zinc battery, which could change the game for micro delivery robots.

Small but mighty, it has high energy density and is made with inexpensive materials that are mostly nontoxic and much more environmentally friendly than previous lithium ion batteries. The zinc battery can't catch fire if damaged, and could be upcycled from retired body armor. And, it could double the range of delivery robots.

The only downside? Zinc batteries do have to be replaced a bit more frequently. Over its life cycle, the metal eventually forms spikes that break the membrane between electrodes. The electrode network is what provides the power, so as it breaks down, so does the battery.

According to the University of Michigan researchers who designed it, integrating the battery into the structure of the robot is essential, especially as robots get smaller and smaller. The smaller the scale, the less efficient existing stand-alone batteries tend to be.

Deliveries aren't the only application being worked on. Researchers are hoping that zinc batteries will also improve the development of swarm robots, small bots that can self-assemble into larger devices, due to a significant decrease in weight.

All I know is that if the robots take over, I’d rather take on one big robot than a million small ones in a fight, but it seems like I might lose that battle either way.