Product optimization of LFP/Graphene composite cathode material for Li-ion batteries

We have developed a new graphene coating method onto the aluminium current collector. This results in eight times as much capacity at high (dis)charge rates, such as 10C, as compared to state of the art LFP electrodes. At the full cell level, similar trend is also achieved with twice as much capacity over a wide range of (dis)charge rate (1C to 10C). The most important consequence of this improvement is that we are able to significantly increase the energy and power density of the battery at a given charge/discharge rate, and that it allows us to increase the thickness of the cathode. Based on the EIS results carried out at different stat of charges, charge transfer resistance was found to drop ~90% which is an indicator of better electrode utility. These results were complemented by rate mA/cm2 vs. mAh/cm2 plots that were extracted from rate performance tests. It was found that infliction point where the areal capacity takes a downward trend is shifted to higher current densities. This reflects the fact that rate performance of the electrode has been improved upon coating the Al foil. Comparison to commercial coated Al foil and commercial LFP electrodes were also completed. It was demonstrated that our coated electrode was superior to that of a commercial product and may be produced at a lower cost due to the exclusion of additives in the coating layer. The comparison to commercial A123 electrode was done by dismounting a A123 battery and recovering its LFP electrode. Results suggests that our LFP electrode cast onto coated Al foil outperforms at all C-rates employed. Raman scans were recorded along the coated Al foil showing that the the coating layer was composed of multiple graphene layers that gave similar Raman signals to those of graphite. Current efforts include adhesion test and increased electrode mass loading to reach high energy target.

The primary objective of the present project is to develop our LiFePO4/graphene (LFP/Graphene) composite material to the pilot decision level. LiFePO4 is a widely used material for cathodes in Li-ion batteries. It is expected that the addition of graphene will significantly improve the properties of the material, such that capacity, lifetime and power density of the Li-ion battery is also improved. The major challenges are on the practical side related to synthesis and formulation of the material. On the theoretical side the challenge is to study and understand how the presence of graphene affects the diffusion behaviour of lithium ions in the material, as well as chemical degradation mechanisms. A combination of electrochemical techniques and other materials characterization techniques will be used for the fundamental study. A "pre-pilot"/ large lab-scale reactor will be set up with the dual purpose of process scale-up and production of sufficient material to make 18650-type batteries for demonstration. These results, and results from a technical economical evaluation will constitute the basis for decision to go to pilot scale.