Electrochemical Characterization of Artificial Solid Electrolyte Interphase Developed on Graphite Via ALD

Abstract

During formation of Li-ion batteries, a ‘natural’ solid electrolyte interphase (SEI) is formed at the anode side by decomposition products of the electrolyte. The properties of the SEI are extremely decisive for the overall battery properties, such as rate capability and cycling stability. However, the SEI formation consumes Li, leading to so called ‘formation losses’ that can make up to 15% of the theoretical energy density of the battery. Several approaches have been presented to overcome formation losses while preserving excellent overall battery properties. Particularly, electrochemical prelithiation and the application of artificial SEIs prior cell assembly are considered to effectively reduced formation losses while improving the interfacial charge transfer properties and increasing cycling stability.Herein, the authors present an innovative approach of applying a multifunctional artificial SEI on anode material powders via consecutive atomic layer deposition (ALD) cycles. As a model system, graphite powder has been chosen to be modified and characterized.The resulting electrodes show substantially improved electrochemical performance in half cells and full cells, regarding initial capacity loss, CE and cycling stability. Furthermore, model electrodes consisting of a single layer of graphite particles were manufactured, which exclude the effects of a typical composite electrode and therefore reveal the intrinsic properties of the active material. Using this approach, the interfacial kinetics and the rate capability are investigated comparatively between pristine and ALD coated electrodes, revealing the impact of the artificial SEI on the materials level.