How the Binder/Solvent Formulation Impacts the Electrolyte Reactivity/Solid Electrolyte Interphase Formation and Cycling Stability of Conversion Type Electrodes

Abstract

Conversion/alloying type materials are of great interests in term of electrochemical performance for Li-ion batteries and beyond. To address their large volume change (typically >200%) during cycling, tailoring the binder/solvent system used for the electrode formulation together with the use of electrolyte additives are the most used and efficient approaches. However, only few studies have investigated the role of the binder/solvent formulation on the electrolyte reactivity/solid electrolyte interphase (SEI) formation and its composition. To tackle this issue, gas chromatography coupled with electron impact mass spectrometry and X-ray photoelectron spectroscopy analysis were used to understand the long term cycling stability (100 cycles) of NbSnSb-based electrodes. It is showed that CMC-H2O and PAA-H2O formulations favored the formation of a more homogeneous SEI while maintaining efficient active/conducting particles bridging, which results in high cycling stability. PVDF-NMP and PAA-NMP led, however, to much lower coulombic efficiency and higher irreversible capacity correlated with the formation of thick SEI with a concomitant disconnection of active particles. These results highlight that CMC and PAA act as artificial SEI and/or as SEI stabilizers. Overall, this work should benefit to all researchers working on improving, through electrode formulation, the lifetime of Li-ion batteries and beyond.