Tuning Surface Energy of Zn Anodes via Sn Heteroatom Doping Enabled by a Codeposition for Ultralong Life Span Dendrite-Free Aqueous Zn-Ion Batteries

Abstract

Aqueous Zn-ion batteries (AZBs) have been considered as one of the most promising large-scale energy storage systems, owing to the advantages of raw material abundance, low cost, and eco-friendliness. However, the severe growth of Zn dendrites leads to poor stability and low Coulombic efficiency of AZBs. Herein, to effectively inhibit the growth of Zn dendrites, a new strategy has been proposed, i.e., tuning the surface energy of the Zn anode. This strategy can be achieved by in situ doping of Sn heteroatoms in the lattice of metallic Zn via codeposition of Sn and Zn with a small amount of the SnCl2 electrolyte additive. Density functional theory calculations have suggested that Sn heteroatom doping can sharply decrease the surface free energy of the Zn anode. As a consequence, driven by the locally strong electric field, metallic Sn tends to deposit at the tips of the Zn anode, thus decreases the surface energy and growth of Zn at the tips, resulting in a dendrite-free Zn anode. The positive effect of the SnCl2 additive has been demonstrated in both the Zn∥Zn symmetric battery and the Zn/LFP and Zn/HATN full cell. This novel strategy can light a new way to suppress Zn dendrites for long life span Zn-ion batteries.

Stabilizing Zinc Electrodes with a Vanillin Additive in Mild Aqueous Electrolytes

“…Rechargeable zinc batteries (RZBs) employing mild aqueous electrolytes hold promise for large-scale energy storage applications owing to the advantages of the metallic Zn anode, including intrinsic safety, globally abundant reserves, and high gravimetric and volumetric capacity (820 mAh g –1 and 5855 mAh cm –3 ). − Moreover, the mildly acidic aqueous electrolytes (e.g., ZnSO 4 solution) with high ionic conductivity can promote the rechargeability of traditional oxide cathode materials (e.g., MnO 2 and V 2 O 5 ), which generally suffer from severe capacity fade in strongly acidic or alkaline electrolytes. , However, state-of-the-art RZBs are hindered by the irreversibility of Zn anodes associated with side reactions and metallic dendrite formation. , Since the redox potential of Zn 2+ /Zn is −0.76 V versus the standard hydrogen electrode (SHE), water decomposition along with the hydrogen evolution reaction (HER) inevitably occurs on Zn during battery rest and operation, leading to the severe corrosion of Zn anodes . Moreover, the HER elevates the local pH value and provokes the formation of inactive byproducts (e.g., Zn­(OH) 2 and Zn 4 SO 4 (OH) 6 · x H 2 O), resulting in a low Coulombic efficiency (CE) and a degradation of battery performance. − In addition, the nonuniform Zn 2+ flux originating from heterogeneous nucleation sites and concentration polarization results in rampant dendritic Zn deposition, which accelerates parasitic reactions and shortens the battery lifespan. , …”

Turning the Byproduct Zn4(OH)6SO4·xH2O into a Uniform Solid Electrolyte Interphase to Stabilize Aqueous Zn Anode

“…In addition, the calculated Bader charge on the Zn atom adsorbed on the Zn(101) facet is −0.1 e, while no charge transfers from Zn atom to the ZHS(001) surface, also suggesting the repulsion of ZHS to Zn atoms. The ZHS(001) facet also possesses lower surface energy than that of the Zn(101) facet (0.06 J m –2 vs 1.03 J m –2 , Figure S1), which could help prevent the direct deposition of Zn atom on the ZHS surface, thus restraining the vertical growth of Zn dendrites. − …”

Highly Strengthened and Toughened Zn–Li–Mn Alloys as Long‐Cycling Life and Dendrite‐Free Zn Anode for Aqueous Zinc‐Ion Batteries

“…The ultra-low plating/stripping overpotential of our ternary ZnLiMn alloy surpasses most of reported binary Zn alloys and other kinds of Zn anodes. [37,38,41] Compared with other kinds of strategies for inhibiting dendrite issues like coating on Zn anode, [22,[42][43][44] adding additives into electrolyte, [21,26,27,45] using high concentration Zinc ion electrolyte [46,47] and using hydro gel electrolyte, [48,49] the ZnLiMn still shows smaller overpotential. Electrochemical impedance spectroscopy (EIS) shows that the Zn-0.4Li-1.0Mn exhibits a smaller charge-transfer resistance R CT of 28.5 Ω than that of pure Zn (68.4 Ω), suggesting the faster electrochemical kinetics, and higher electronic conductivity of Zn-0.4Li-1.0Mn alloy (Figure 2c).…”