Spatially resolved modeling and characterization of (de-)intercalation in Li-Ion battery materials

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Li-ion battery materials undergo a significant volume change during charging anddischarging, which is, dependent on the material, connected to a change of thecrystallographic structure. This causes mechanical fatigue which deteriorates the performanceof the batteries. The project aims on investigating, spatially- and time-resolved, the evolutionof the Li distribution and phase transitions during (dis-)charging by means of theoretical andexperimental methods. The project will focus on Li-Fe-P-O as a promising class for futurelow-cost electrode materials1. The theoretical part uses ab-initio calculations of structuralstability and diffusion coefficients in Li-Fe-P-O systems as well as phase-field simulation ofcharge transfer at the anode-electrolyte interface, volume expansion during interdiffusion,phase transformation and mechanical stress. The possible device improvement gained byshrinking microstructural elements to the nanometer regime will be covered by includingsurface and interface related materials characteristics. The experimental part consists ofcombinatorial preparation of thin film samples of cathode materials in the frame of the Li-Fe-P-O system and their high-throughput characterization. The samples will be investigated withrespect to the Li-distribution during (dis-)charging in different electrolytes using new modesof scanning electrochemical microscopy (SECM) in a glove box. Furthermore uniquecombined electro-chemical/mechanical experiments based on micromachined cantileverscoated with Li battery materials will be performed in a glove box in order to reveal stresseffects during Li (de-)intercalation. The project is expected to give a complete and for the firsttime spatially resolved picture of the complex mechanisms of Li transport and phasetransitions in nano-grained battery materials. From the theoretical and combinatorialinvestigations a route to improved materials will be pinpointed.