Completed project: Nanostructured lithium-ion batteries
The focus of this project was to improve battery performance by engineering the anode and cathode in a mesostructured and hierarchical fashion.
The goal of the project under the stewardship of Prof. Ullrich Steiner from the Adolphe Merkle Institute of the University of Fribourg was to provide a high specific surface area for Li-ion intercalation, interspersed with larger pores allowing ion diffusion. The resulting network should have good mechanical properties upon battery cycling.
The general approach to achieving the aims above consisted in the combination of sol-gel synthesis of inorganic materials with block-copolymer self-assembly, as previously demonstrated by the Steiner group for other material functionalities (e.g. photovoltaics, optics). The initial approach therefore made use of the co-assembly of block copolymers with a sol-gel chemistry approach to produce nanostructured anatase titania spheres of several micrometres in diameter. This is a proof of principle that battery relevant materials can be easily synthesised with highly controlled hierarchical morphologies, extending from the nano- to the microscale. This was extended by a second complementary approach, in collaboration with the University of Nottingham, where similar nano-structured self-assembled polymer spheres were synthesised in supercritical CO2. Both of these approaches serve as a generic platform for the manufacture of a range of inorganic battery electrode materials. The usefulness of this approach was demonstrated through the manufacture of hierarchical mesoporous lithium iron phosphate, a commonly used battery cathode material. In a half-cell against Li-metal, mesoporous Li-iron phosphate electrodes that were deposited using industry standard processes exhibited outstanding cyclability and excellent cycle life. As an often-used corresponding anode lithium titatanate was similarly synthesised as mesoporous spheres. Similar to the Li-iron phosphate, excellent mechanical and electrochemical properties were found. Overall, this project has produced electrode materials with well-defined porosities that considerably improve battery performance, while remaining compatible with standard battery manufacture protocols.