Folic acid-based supramolecules for enhanced stability in potassium ion batteries

Organics present significant prospects as environmentally friendly and sustainable electrode materials for potassium ion batteries (PIBs) because of their abundant, recyclable and highly customizable characteristics. However, small molecular organics are easily solubilized in organic electrolytes, resulting in a low capacity and poor stability. Herein, the folic acid-based supermolecules (SM-FAs) are successfully prepared by a hydrothermal assisted self-assembly strategy. Due to multi-locus hydrogen bonds (HBs) and the cyclized π-conjugated interactions, the structural stability of SM-FAs has been significantly improved, and the solubility in carbonate electrolytes has been effectively inhibited. As an anode for PIB, the SM-FA-6 sample exhibits a large capacity (206 mAh/g at 50 mA/g) and an outstanding cycle stability (capacity retention of 91% after 1000 cycles at 50 mA/g). More impressively, an integrative storage mechanism which combines both the general enolization reaction between C=O groups and K⁺, and the atypical π–K⁺ interaction within the assembled conjugation framework, is unraveled for potassium ion accumulation. It is envisioned that this facile self-assemble strategy opens up a promising avenue to modulate the stability of small molecular organic electrodes with enhanced storage capacity.