Lidiya Komsiyska

Mechanochemical Synthesis of PEDOT:PSS Hydrogels for Aqueous Formulation of Li-Ion Battery Electrodes

Water-soluble binders can enable greener and cost-effective Li-ion battery manufacturing by eliminating the standard fluorine-based formulations and associated organic solvents. The issue with water-based dispersions, however, remains the difficulty in stabilizing them, requiring additional processing complexity. Herein, we show that mechanochemical conversion of a regular poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) water-based dispersion produces a hydrogel that meets all the requirements as binder for lithium-ion battery electrode manufacture. We particularly highlight the suitable slurry rheology, improved adhesion, intrinsic electrical conductivity, large potential stability window and limited corrosion of metal current collectors and active electrode materials, compared to standard binder or regular PEDOT:PSS solution-based processing. When incorporating the active materials, conductive carbon and additives with PEDOT:PSS, the mechanochemical processing induces simultaneous binder gelation and fine mixing of the components. The formed slurries are stable, show no phase segregation when stored for months, and produce highly uniform thin (25 μm) to very thick (500 μm) films in a single coating step, with no material segregation even upon slow drying. In conjunction with PEDOT:PSS hydrogels, technologically relevant materials including silicon, tin, and graphite negative electrodes as well as LiCoO2, LiMn2O4, LiFePO4, and carbon-sulfur positive electrodes show superior cycling stability and power-rate performances compared to standard binder formulation, while significantly simplifying the aqueous-based electrode assembly.

Detecting Aging Phenomena in Commercial Cathodes for Li-Ion Batteries Using High Resolution Computed Tomography

Using high resolution computed tomography (CT) the change of the morphometric parameters in depth of electrodes for lithium ion batteries with aging has been examined. Commercially available 2 Ah Li-ion cells were continuously cycled to different state of health (SOH). The cathodes were subsequently analyzed using CT with voxel size resolution of about 400 nm. For a quantitative analysis binarized images were evaluated and various properties such as the size distribution of active particles analyzed. Using this technique a decrease in the average particle size and an increase in number of particles of LiCoO2 with decreasing SOH of the battery is confirmed experimentally for the first time.