Anion-promoted CB[6] macromolecule dissolution for stable Zn-ion batteries

Abstract

The electrode/electrolyte interface of inhomogeneous Zn deposition and water-induced side reactions has hampered the practical application of rechargeable Zn-ion batteries. By a strategy of anionic facilitation of macromolecule dissolution, we introduce an initially water-insoluble macrocyclic organic molecule, cucurbit[6]uril (CB[6]), as a highly effective additive into the ZnSO₄ electrolyte. The horizontal adsorption of CB[6] molecules on the surface of the Zn anode, forming an H₂O/SO₄²⁻ shielding layer, inhibits side reactions. The existence of zincophilic sites optimizes the diffusion behavior of Zn²⁺, inducing epitaxial deposition of Zn²⁺ along the (002) lattice plane. This effectively eliminates rampant dendrite growth. Remarkably, a trace amount of the CB[6] additive results in an ultra-long life of 4160 hours (>173 days) in a symmetrical cell at 1 mA cm⁻² and 1 mA h cm⁻², and long-term stability of over 1100 hours and 480 hours even at a high current density of 10 mA cm⁻² and a high DOD of 34.2%, respectively. Also, Zn‖PANI full batteries show an ultra-long cycle life of 7600 cycles and 98.8% capacity retention. Significantly, a pouch cell with high-loading mass (13.5 mg cm⁻²) exhibits impressive capacity retention (90.9%) at a rate of 0.5 A g⁻¹.