Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 45: Nonaqueous Liquid/Solid Interfaces

O 45.1: Vortrag

Mittwoch, 18. März 2015, 11:30–11:45, HE 101

Formation of double layers in ionic cells and their relevance for cell voltage and charge transfer — •René Hausbrand — Darmstadt University of Technology, Materials Science Department, Darmstadt, Germany

Double layers at electrode-electrolyte interfaces in ionic devices determine charge transfer kinetics and cell voltage. Lately, interest to understand the double layer formation of Li-ion electrode - electrolyte interfaces has increased due to the future use of Li-ion cells for energy storage. Under equilibrium conditions, the electric potential gradient at an ion electrode - electrolyte interface is determined by the difference of ion chemical potential between electrode and electrolyte, contributing to the electrode potential. For ion transfer, the formation of diffuse double layers (space charge layers) is relevant. This contribution focuses on the impact of the interfacial electrical potential gradients on cell voltage using the example of an all-solid Li-ion cell. First, the fundamentals regarding the origin of cell voltage are briefly introduced. Then, results of surface science investigations on thin film LiCoO2 electrodes and LiPON solid state electrolytes are presented, and evaluated to yield the energy level diagram of the LiCoO2|LiPON|Li cell. The results demonstrate the formation of space charge layers and indicate that the ionic contribution to the cell voltage remains low.