Salting-Out Promotes Outstanding Organic Potassium-Ion Batteries

Abstract

Organic materials are promising as battery electrodes due to their flexible design, low cost, and sustainability. Yet, they suffer from high solubility in organic electrolytes and inferior cycling stability. Herein, we propose using high-concentration electrolytes in which organic material dissolution is suppressed via the salting-out phenomenon. Our experimental and theoretical results show that during salting-out, the potassium bis(fluorosulfonyl)imide (KFSI) salt competes with the polyaniline (PANI) molecules to participate in solvation, resulting in a significant reduction of free solvent molecules, further reducing PANI’s dissolution and promoting the formation of anion-derived SEI. Consequently, the 4.0-volt PANI||K cell exhibits a capacity retention of 83.22% after 1250 cycles at 3 A g−1 and an average Coulombic efficiency (CE) of 99.94%. The 4.4-volt PANI||K cell also delivers an average CE of 99.72% after 250 cycles. Notably, the PANI||graphite pouch-cells achieve long cycling stability of 3000 cycles with an average CE of 99.80%. The salting-out approach to stable cathodes offers a promising new approach for developing highly reversible and long-cycling organic batteries.

Keywords: Potassium ion battery, Salting-out effect, Electrolyte regulation, Organic electrode