A new high-throughput pulsed laser deposition system was designed, built, commissioned and exploited by the fellow. This new method permitted a 15-fold increase in throughput for making thin films, increasing from 4 films a day to 60 films per day; allowing better optimisation on materials. This also had knock on effects on the way that materials optimisation is approached. Funding of $100 k was awarded to the candidate from the Science Support Office at Advance Light Source.
A model system was developed of current commercial cathodes NMC 532 and LiMn2O4 on metal and single crystal supports. These thin films had low roughness (below 1 nm r.m.s. roughness).
A soluble buffer layer was optimised from which low roughness crystalline NMC films could be grown and subsequent “lifted off”. This means that it was possible to make free-standing thin films of NMC 532 with dimensions 10 mm x 10 mm x 5 nm. This is a world’s first battery cathode materials.
These model systems were investigated by several highly surface/interface specific laboratory and synchrotron based techniques, including Near Field Spectroscopy, AFM, X-Ray Reflectivity, X-Ray Photoemission Spectroscopy.
The combination of the above allowed for development of a new understanding of surface degradation processes which occur and the types of changes to the cathode surface which occur during cycling.
A simple surface technique was created and it was demonstrated on thin films that this could reduce these negative effects, in particular interfacial impedance rise over long-term cell cycling. It was then demonstrated that this could be directly applied to bulk cathode materials (before making the cell) and interestingly after making the cell.
