Dual-protected zinc anodes for long-life aqueous zinc ion battery with bifunctional interface constructed by zwitterionic surfactants

The dendrite growth on the surface of zinc anodes and formation of inactive by-products of Zn4(OH)6SO4.xH2O (ZHS), mainly attributed to the "tip effect" of an uneven surface and water corrosion of zinc anode, have seriously shrunk the anode life and hindered the commercialization of aqueous zinc ion batteries (AZIBs). Herein, we describe a bifunctional interface constructed by zwitterionic surfactant of N-decyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (Z10), which can form a polarized layer with a build-in electric field at the same time as the self-assembled hydrophobic layer on the zinc electrode surface. Two other zwitterionic surfactants including of N-octyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (Z8) and N-tetradecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (Z14) are also selected, due to the different alkyl chain lengths affect the strength of the built-in electric field and the formation of hydrophobic interfaces. A combined results of experimental data with simulated calculations calculations confirm that the strength of the electric field obtained with Z10 attenuates the "tip effect" on the zinc anode surface, while accelerating the transfer of zinc ions and promoting rapid and uniform zinc plating/stripping processes. And benefited from the hydrophobic layer, the free water molecules are blocked outside the inner Helmholtz plane, lead to the suppressed ZHS formation. With the dual protection, in case of Z10, the cycle stability of the AZIBs is considerably improved to yield a long cycle lifetime of 2000 h with a coulombic efficiency of 99.4 %.