Is (002) the only one that's important? An overall consideration of the main exposed crystallographic planes on a Zn anode for obtaining dendrite-free long-life zinc ion batteries

Abstract

To obtain dendrite-free zinc-ion batteries, efforts have been exerted to modulate Zn²⁺ deposition along the Zn(002) plane. However, the consideration of only the Zn(002) plane lacks certain rationality since Zn(100), (101), (102) and (103) are also the main exposed crystallographic planes on a typical Zn anode. Herein, a theoretically guided Zn²⁺ confining–anchoring strategy is proposed based on the different strengths between the alpha-cyclodextrin (α-CD) additive and various crystallographic planes of zinc. Density functional theory calculations indicate that the exposure of the relatively zincophilic (102) plane is preferred in the presence of α-CD additives. As predicted, Zn²⁺ ions are confined, anchored and nucleated on the (102) plane to achieve preferential growth along the (002) plane of zinc. Constrained 2D diffusion and alleviated concentration polarization at the anode lead to suppressed dendrite growth. Aqueous side reactions are also restricted because of the blocked contact between water and anode after modification. With α-CD additives, the Zn anode exhibited an exceptional cumulative capacity of 3 A h at 5 mA cm⁻² in a symmetric cell and a high coulombic efficiency of ∼99.4% in a Cu‖Zn cell during cycling for 2000 h. A Zn_xV₂O₅‖Zn full battery also demonstrated a good rate capability and a long life span of 2000 cycles with an outstanding capacity retention of 91.3%.