Understanding and Controlling Interfacial Reactivity of Silicon Electrodes—Impact of Electrode and Electrolyte Composition

<br/>Silicon is an attractive negative electrode material for lithium-ion batteries (LIBs) because of its high theoretical capacity (3579 mAh g–1), low cost, and demonstrated ability to store Li-ions. However, Si experiences limited capacity retention due to significant volume change on (de)lithiation and repeated formation of the solid-electrolyte interphase (SEI) as the silicon evolves with cycling. These factors can contribute to high internal resistance, low Coulombic efficiency, and decreased capacity over cycling.<br/>Appropriate formation of the SEI through electrolyte modification is a promising strategy to address this issue. Previous studies have evaluated the effectiveness of electrolyte additives on the SEI and capacity retention. While it has been long recognized that the electrode/electrolyte interface is critical, it has proven challenging to probe directly often requiring recovery of the active electrodes with subsequent examination risking change from their functional environment. Cell reactions including SEI formation can be elucidated by coupling information from a variety of methods including electrochemistry, x-ray photoelectron spectroscopy (XPS) of recovered electrodes, and isothermal microcalorimetry (IMC). Outcomes from a series of investigations on the reactivity of silicon electrodes of several compositions and electrolyte environments will be highlighted.