Supercapacitors, or electric double-layer capacitors, store charge via polarization at the electrode-electrolyte interface. Most models of interfacial charge storage at the electric double layer (EDL) focus almost exclusively on the electrolyte, accounting for the transport and arrangement of ions approaching the electrode surface. On the other hand, the electrode is usually considered fixed, with charge accumulation or depletion as the only response to interface polarization. In reality, however, the presence of the interface impacts the fundamental properties of both the electrode and the electrolyte, often in complex and nontrivial ways that are difficult to capture using simple models. These changes can profoundly impact performance predictions. In an effort to realize supercapacitor simulations that more closely approximate in operando experiments, we have been adapting more sophisticated ab initio treatments of the electrode-electrolyte interface that directly or indirectly consider the interplay between the electrode and the electrolyte. Using graphene-based supercapacitor electrodes as a model system, I will discuss how these more complex treatments address the shortcomings of simplistic models, with particular emphasis on improved descriptions of intrinsic quantum and EDL capacitance contributions. I will also discuss how combining advanced theory with in operando X-ray spectroscopy can give insights into nanoscale chemical changes and mesoscale morphological changes occurring in graphene-based supercapacitor electrodes during charging. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.

Towards simulations of electrochemical interfaces in graphene-based supercapacitors under realistic operating conditions

248th National Meeting (2014)

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