The Optimal Amount of Lithium Difluorophosphate as an Additive for Si‐Dominant Anodes in an Application‐Oriented Setup

Abstract

Fluoroethylene carbonate (FEC) and vinylene carbonate (VC) are considered the most effective electrolyte additives for improving the solid electrolyte interphase (SEI) of Si‐containing anodes while lithium difluorophosphate (LiDFP) is known to improve the interphases of cathode materials and graphite. Here, we combine VC, FEC, and different amounts of LiDFP in a highly‐concentrated electrolyte to investigate the effect on Si‐dominant anodes in detail. Cycle life tests, electrochemical impedance spectroscopy and rate tests with anode potential monitoring were conducted in Si/NCM pouch cells. The results reveal that adding LiDFP to the electrolyte improves all performance criteria of the full cells, with a concentration of 1 wt.% being the optimal value for most cases. Post‐mortem analyses using scanning electron microscopy and x‐ray photoelectron spectroscopy showed that a more beneficial SEI film was formed for higher LiDFP concentrations, which led to less decomposition of electrolyte components and a better‐maintained anode microstructure.

Thickness Variation of Conductive Polymer Coatings on Si Anodes for the Improved Cycling Stability in Full Pouch Cells

“…The latter causes material pulverization and loss of electrical contact with the current collector. ,, Furthermore, the volume expansion leads to continuous fracture of the solid electrolyte interphase (SEI) layer on the active material during cycling. In this context, there is intensive research ongoing regarding the development of Si anodes, on material − as well as on electrode and cell levels. ,− …”

“…In this context, there is intensive research ongoing regarding the development of Si anodes, on material 9 − 12 as well as on electrode and cell levels. 8 , 13 − 16 …”