The natural abilities of bamboo have inspired new battery designs. 

A water-carrying membrane inside bamboo that enables it to be the fastest growing plant in the world has inspired a research team to develop more efficient electrodes for batteries.

Professor Ziqi Sun works on ways to mimic the structural and optical properties of natural objects such as seashells, fish scales and fly eyes, to develop sustainable energy solutions.

His latest project was inspired by walking past a clump of bamboo in the Brisbane City Botanic Gardens.

It has led to a new design inspired by the multilayer membrane that runs up inside the bamboo stem.

The membrane, which is about as thick as a piece of paper, allows the ultrafast transport of water and nutrition up the bamboo. The membrane is made up of layers that are packed very closely together on the side closest to the inner ring of the bamboo, and further apart on the side nearest the centre of the bamboo. The layers also have a porous structure on the surface.

The researchers found this multilevel interlayer structure enabled water and electrolytes to travel through the bamboo in two ways.

The inner layered structure, with the confined spacing, enables the “superfluidic” travel of the liquid and electrolytes, which means the liquid travels very quickly through the plant. The outer layer, with more space between the levels, allowed the liquid to be more quickly dispersed through the structure.

This research project was then used to build on previous work on two-dimensional nanomaterials, which are super thin materials, for the very fast transport of ions through a battery.

“Nature has taught us how to design with these kinds of two-dimensional materials, and how a multilevel distribution of the space will be much more helpful for high-performance batteries,” Professor Sun said.

Researchers mimicked the bamboo structure with a membrane using layers of “nanosheets” of cobalt oxides and graphene, which individually were about 100,000 times thinner than a human hair.

The team applied suction to one side of the sheets to replicate the layer structure of the bamboo membrane, which saw the closest layers pulled tightly together with a distance of less than 5 nanometres between them.

With the force of the suction weakening as the layers built up, the outer layers came together with up to 2200 nanometres between them. 

The bioinspired membrane they produced, which was 50 mm round and tens of micrometres thick made up of thousands of layers, was examined for its ability to transport ions by placing them into lithium-ion batteries.

The researchers found they outperformed other materials commonly used for electrodes in batteries.

They also examined the membrane’s wettability, which is the ability of liquid to maintain contact with a solid surface, and confirmed that the bioinspired membranes showed a superwetting behaviour towards organic electrolyte. 

This means there was no barrier for the contact and entry of the electrolyte from the surface into the inside membrane.

“The study offers a new principle in designing high-performance energy materials,” Professor Sun said.

“Most importantly, it paves a way for future materials intervention by learning from the greatness of nature.”