Basics of Electrochemistry

(images will be uploaded shortly)

Applications of electrochemical methods are today widespread, making an impact in fields as diverse as manufacturing, consumer electronics, energy storage systems and transportation. Understanding fundamental aspects of the electrochemical processes involved is a mandatory step in the development of these applications.

The research group

Basics of Electrochemistry

Basics of Electrochemistry addresses basic aspects of Electrochemistry as relevant in the context of chemical energy storage. The techniques applied range from classical methods of electrochemical investigation (e.g. potentiostatic methods, impedance spectroscopy) to structural investigation techniques such as scanning tunnelling microscopy (STM), offering access to atomic-scale details. Methods applied in addition include electron microscopy, optical and electron spectroscopy. A brief overview of representative projects is given in the following.

Electrochemical characterization

Electrochemical characterization of electrodes in novel electrolytes. Cyclic voltammetry (CV) and in-situ electrochemical impedance spectroscopy (EIS) are used for the characterization of electrode materials in contact with complex electrolytes, such as organics and ionic liquids. The use of these novel electrolytes opens new interesting investigation possibilities, which were hitherto inaccessible by electrochemical methods in aqueous electrolytes. For instance, the electrochemical characterization of the electrode/electrolyte interface, but also issues of electrode stability during electrochemical cycling are addressed.

In-situ studies of metal Deposition

In-situ studies of metal Deposition: Metal deposition is a process of wide interest in both industry and electrochemical energy storage. Application of in-situ STM technique allows following the incipient phases of metal deposition under operation conditions by imaging the particle nucleation and subsequent growth through the (organic or ionic liquid) electrolyte. The use of additives to control the structure of the deposited metal film, or to mitigate the undesired plating processes, for example in lithium ion batteries, can be addressed by these techniques.

Studies on the electrode/electrolyte interface

Studies on the electrode/electrolyte interface in lithium-ion batteries. Deposition of metallic lithium at the electrodes drastically affects the safety in exploitation of lithium and lithium-ion batteries. Metallic lithium in its turn can facilitate a decomposition of the organic electrolyte, resulting in a complex layer of organic molecules at the electrode surface. On the other hand, formation of similar solid-electrolyte interphase (SEI) layers during the first charging cycles is essential for the long-term stability of a battery. These processes are studied in-situ by chemically sensitive methods, such as quartz crystal microbalance (QCMB) and optical spectroscopy (e.g. IR, Raman), complemented by structural insights from in-situ STM studies.

Multiscale Modeling

The research group Multiscale Modeling is concerned with the multiscale description of energy-relevant systems. The processes that take place in electrochemical storage media during charging and discharging are on different scales in terms of time and length. It is therefore necessary, given an appropriate theoretical description, for different methods and techniques to be developed and used. By combining these methods, it is possible to describe and predict the properties of electrochemical cells even without using empirical parameters. For example, to simulate the macroscopic transfer of charge or mass it is necessary to know various factors, such as the energy barriers for the individual elementary diffusion steps of the charge carriers. However, precisely such information can be determined at the atomic scale, where the structure and energy of corresponding model systems can be determined using the appropriate ab initio methods.

A primary goal of our activities is to establish a coupling between the different scales by first linking the relevant theoretical models with one another and then applying them to energy-relevant systems (e.g., lithium-ion or lithium-air ones). The specific goal is to reach a fundamental understanding of the important processes at the mesoscopic or macroscopic levels, with the determining elementary processes being described on the microscopic scale.

Methodologically, multiscale coupling is achieved horizontally via an embedding procedure and vertically on the basis of parameter passing. This involves methods ranging from microscopic modeling using quantum chemical techniques to molecular dynamics and statistical mechanics to the macroscopic description of electrochemical systems on the basis of coupled differential equations. The focus is on the coupling between the scales involved.