Aryl Diazonium- and Pyrene-Functionalised Graphite for Lithium-Ion Batteries

Abstract

One of the main reasons for battery aging in lithium-ion batteries (LIBs) is the formation of a solid electrolyte interphase (SEI). SEI formation results in capacity loss and power fading due to irreversible electrochemical decomposition of electrolyte. However, the SEI protects the negative electrode from further parasitic surface reactions with the electrolyte. Therefore, it is of great interest to learn more about factors influencing the SEI and its formation. One approach is to modify the surface of the active material.Since graphite is commonly used as negative electrode material in LIBs, we modified graphite with anchor molecules featuring functional groups. In particular, we use aryl diazonium salts and pyrenes as anchor molecules to cover a covalent and a non-covalent approach. The influence of different functional groups on the electrochemical properties of graphite electrodes is investigated. Furthermore, the importance of the modification method and the influence of the anchor molecule is addressed. The functional groups of modified graphite electrodes enable further layer growth, which is an important aspect for the design of an artificial SEI.For surface and electrochemical characterisation of the modified graphite samples, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and galvanostatic cycling are used.Financial support of the German Research Foundation (DFG) within the project B2 of the Collaborative Research Centre (SFB 1176) is kindly acknowledged.