Ion pumping synergy with atomic anchoring for dendrite-free Zn anodes

Abstract

• Ion pumping synergy with atomic anchoring is first proposed for Zn anodes. • The TCNQ@Zn foils effectively avoid 2D diffusion on the exposed Zn (101) surface. • The TCNQ@Zn foils induce 3D diffusion deposited on Zn (002) plane. • The TCNQ@Zn cells cycle over 2000 h under 1, 5, and 10 mA cm −2 . • The full cells maintain a capacity decay rate of only 0.03% over 1000 cycles. The practical application of aqueous Zn-ion batteries (AZIBs) has been limited by the notorious dendrite growth and side reactions of Zn anode, despite their high theoretical capacity, low cost, and intrinsic safety in large-scale energy storage. Herein, the tetracyanoquinodimethane anions (TCNQ 2− ) modified Zn anode (TCNQ@Zn) is fabricated via in-situ interfacial etching of Zn by TCNQ, which induces more exposure of Zn (101) planes. Benefitting from the abundant cyano group of TCNQ 2− , the TCNQ 2− can serve as an ion pump to continuously pump Zn 2+ in electrolyte for uniform Zn nucleation deposition on the exposed (101) surface. Simultaneously, owing to the significantly higher migration barrier on TCNQ 2− modified Zn (101) than (002), the 2D diffusion on the Zn (101) can be effectively inhibited, inducing 3D diffusion on Zn (002) to form the ordered (002) deposition orientation. These ordered Zn (002) textures significantly restrain the Zn dendrite formation and passivation reaction. Due to the synergistic effects of surficial ion pumping and atomic anchoring, the TCNQ@Zn anode exhibits remarkable cycling stability over 2000 h at different current densities (1, 5, and 10 mA cm −2 ). This work provides new theoretical guidance for highly stable reversible Zn metal anodes. TCNQ@Zn anode is fabricated by in situ interfacial reaction, which shows TCNQ 2− modified surface with a high proportion of Zn (101). Ion pumping synergy with atomic anchoring effect enable cells to cycle over 2000 h at 1, 5 and 10 mA cm −2 .