Interfaces Studies on LiNi0.82Mn0.07Co0.11O2 (NMC811) with Vinylene Carbonate Additive Using in-Situ Raman and X-Ray Absorption Spectroscopy at Ultra-High Operation Voltage

Abstract

Interfaces evolutions in lithium-ion battery determines the rate-limiting step for lithiation of most electrode materials by influencing Li+ insertion occurred in the solid phase boundary. To our best knowledge, we will be the first to employ the in-situ characterization techniques including Raman spectroscopy and X-ray absorption spectroscopy (XAS) to probe the cathode electrolyte interface (CEI) formation and its protective effect on NMC cathode with the presence a high concentration of vinylene carbonate (VC). The Raman data showed a brand new peak around 1000 cm-1 appeared after the initial cycle due to the VC polymerization indicating the maturity of CEI layer with a modified electrolyte system, the in-situ XAS data revealed that the surface reconstruction of NMC cathode was significantly suppressed with the VC additive by delta-R analysis from extended X-ray absorption fine structure (EXAFS) and the oxidation state of nickel was relatively stable compared to a baseline electrolyte environment when the operation voltage window was pushed to 4.8V. This work shed light on characterizing materials property across spatio-temporal scales relevant for various additives electrolyte system under in-situ/operando conditions including specific form factors, providing design principles for materials and composites, functional aspects of interfacial operation and degradation pathways. Figure 1