The performance of current electrochemical energy storage systems (EESS) is often cathode limited due to the large imbalance between the cathode and anode’s capacities (e.g. 140 mAhg-1 and 372 mAhg-1 respectively for electrodes in LiCoO2-LiC6 batteries). The energy density of EESS can be dramatically improved by developing cathode materials with higher capacities and reduction potentials. Organic compounds are promising cathode materials due to their light-weight, tunability, and ability to undergo multiple redox processes. The Abruña research group investigates cathode materials by initially designing and computationally screening compounds to identify hits. These target molecules are synthesized and coupled to polymers to mitigate solubility and conductivity issues. The cathode materials are characterized extensively by electrochemical techniques such as cyclic voltammetry (CV), rotating disk electrode (RDE), electrochemical quartz crystal microbalance (EQCM), as well as spectroscopy (e.g. UV-Vis, Raman, X-ray). The materials are also tested under practical device conditions in coin cells. Each part of the research loop provides valuable feedback to improve the performance of the cathode materials.
Spectroelectrochemisty is one of the techniques employed to probe battery components. Researchers design UV-Vis and/or Raman experiments to characterize compounds in solution or solid state, which includes real battery device conditions. The planning process can include designing and fabricating new cell configurations. The analysis of spectra often includes the incorporation of computational data.
Raman spectroscopy is a powerful analytical tool by which we can obtain chemical information about a sample in study. We currently have a confocal Raman microscope by which we characterize both organic and inorganic samples to obtain information about the chemical changes and chemical properties of materials. We also have the capability to do in situ and operando experiments by which we can track chemical changes during electrochemical cycling. A representative experiment of this technique can be observed in the attached figure where a poly-3,4-ethylenedioxythiophene (PEDOT) conducting polymer film-modified electrode is being probed at different doping states.