Liquid crystal locomotion

Nanoporous materials developed by Nanotecture may offer a solution to the power limitations of standard, non-rechargeable lithium batteries — a major drawback in high-power applications.

The company is using a templating method to produce nanostructured materials to make the batteries’ cathodes, allowing structures to be formed around a template, which is then removed.

‘We use things such as liquid crystals as templates,’ said Nanotecture chief executive Chris Wright. ‘These self-organise at a nano-scale, allowing us to build our material around the liquid crystal.’

Wright said the technique could solve the batteries’ low power problem by improving the chemical kinetics of the solid state reactions within the electrodes.

‘If you can make an electrode with a well-controlled high surface area, it means the electrolyte can diffuse relatively quickly, therefore you can increase the kinetics,’ he said. ‘This would increase the power of the battery.’

The hexagonally close-packed liquid crystals used by Nanotecture in the battery manufacturing process contain hexagonal, rod-shaped crystals, surrounded by an aqueous component.

The process typically dissolves metal ions in the aqueous component, which are electrodeposited onto a support around the liquid crystal structure. This forms a metal film around the crystals, which are washed off to leave the film with a hexagonally close-packed array of holes. Emulsions, micelles or even different phases of liquid crystals could also be used to create the films, allowing a high degree of control over the sizes of the pores, and the separation between them.

The films have parallel channels of regular-sized holes running through them, which could offer several benefits over standard electrodes. The problems of inter-particle resistance are avoided, and the parallel channels of holes allow the electrolyte to diffuse much more rapidly to the surface of the electrode.

‘We tend to find that we get much faster response times with these materials,’ Wright said. ‘This is why we initially started to exploit them in supercapacitors — essentially a very high-powered battery design. Now we are looking to see whether the same kind of technology can be used in a simple, high-power battery.’

The company is now working on a two-year R&D project with Ultralife Batteries, supported by a £131,000 grant from the DTI.

‘By the end of the project, we will have a new electrode material which, hopefully, we will be able to make economically,’ Wright said.

‘It then becomes a commercial question. We will be looking to see what effect the material has on important characteristics such as cycle life and temperature performance. We hope the result will be a higher power density, allowing batteries to be lighter or smaller for the same power requirement.’