Investigation of 2,6-Sodium Naphthalene Dicarboxylate Structure–Reactivity Relationship by Operando X-ray Diffraction and Post-Mortem Transmission Electron microscopy

Disodium naphthalene dicarboxylate (Na₂-NDC) recently demonstrated promising performance as a negative electrode in full-cell setups. However, its electrochemical reactivity and degradation mechanisms are still not fully understood. In this article, operando X-ray diffraction and post-mortem transmission electron microscopy were combined to investigate the structural and microstructural evolution of Na₂-NDC during cycling. Amorphization, structural degradation, and loss of matter were observed during the first reduction, suggesting important structural instability or reorganization. To go beyond the link between crystallinity and electrochemical reactivity, the crystallographic organization of Na₂-NDC was disturbed using ball-milling. The loss of crystallinity led to a change in the electrochemical response, highlighting the importance of such parameters to accommodate sodium-ion insertion, especially for long-term cycling.