HAXPES study of an enhanced solid electrolyte interphase on silicon based anodes for lithium-ion batteries

Abstract

Increasing the capacity of Li-ion batteries and at the same time making the involved interfaces much more stable is one of the crucial challenges on the way to a sustainable energy use.1 Silicon anodes promise almost a 10-fold capacity increase with respect to conventional graphite anodes2, but still pose issues to be overcome: the continuous degradation of the Solid Electrolyte Interphase (SEI) at the surface of silicon-based active materials in lithium-ion battery anodes has been recognized as the key problem of these electrodes, currently preventing their commercial introduction.3

Here we present a methodology to specifically introduce polymer species into the SEI with the aim of providing a flexible backbone to this layer. The polymer was analyzed using Hard X-ray Photoelectron Spectroscopy (HAXPES), Raman spectroscopy and electrochemical testing. HAXPES enabled us to address the full depth-dependent layer chemistry and allowed us to probe the interface of the solid-electrolyte interphase and the silicon based electrode. The performance was investigated by coin-cell lithium ion battery testing and provides an interesting view into the influence of incorporating polymers in the SEI.