Understanding and Comparing the Stability of Water- versus NMP-Based Tin(IV)Sulfide Electrodes Using Post-Mortem Analysis

Abstract

Tin (IV) sulfide (SnS₂) is a promising anode material for Li-ion batteries (LIBs) due to its high practical reversible capacity of 623 mAhg⁻¹. However, its cycling stability is relatively poor and its long-term degradation during cycling is not yet thoroughly investigated. In this work, a post-mortem analysis of SnS₂ electrodes was performed at pristine state, after the 1^st cycle and at 80 % state-of-health. The analysis compared water-based (Na-CMC/SBR) and NMP-based (PVDF) electrodes revealing insights into their degradation mechanisms and electrochemical performance. During the first cycle, SnS₂ converts into Sn and Li₂S identified by XRD, causing particle cracking and exfoliation. XPS and Raman spectroscopy identified Sn, SnF_x, LiF, Li₂S and carbonates species forming the solid electrolyte interphase (SEI), while in-situ dilatometry revealed up to 60 % irreversible expansion after the first cycle. These species are also found after at 80 % SOH along with an increase in fluorine species, SEI thickness and interfacial resistance. Water-based electrodes exhibited better cycling stability, with 80 wt.% SnS₂ and 10 wt.% binder retaining 80 % capacity after 180+ cycles. These findings underscore the critical role of binder choice and processing in enhancing SnS₂ anodes’ durability and capacity retention, paving the way for sustainable, high-performance LIB anodes.