Cationic Adsorption-Induced Microlevelling Effect: A Pathway to Dendrite-Free Zinc Anodes

Abstract

Dendrite growth represents one of the most significant challenges that impede the development of aqueous zinc-ion batteries. Herein, Gd³⁺ ions are introduced into conventional electrolytes as a microlevelling agent to achieve dendrite-free zinc electrodeposition. Simulation and experimental results demonstrate that these Gd³⁺ ions are preferentially adsorbed onto the zinc surface, which enables dendrite-free zinc anodes by activating the microlevelling effect during electrodeposition. In addition, the Gd³⁺ additives effectively inhibit side reactions and facilitate the desolvation of [Zn(H₂O)₆]²⁺, leading to highly reversible zinc plating/stripping. Due to these improvements, the zinc anode demonstrates a significantly prolonged cycle life of 2100 h and achieves an exceptional average Coulombic efficiency of 99.72% over 1400 cycles. More importantly, the Zn//NH₄V₄O₁₀ full cell shows a high capacity retention rate of 85.6% after 1000 cycles. This work not only broadens the application of metallic cations in battery electrolytes but also provides fundamental insights into their working mechanisms.

Keywords: Aqueous zinc-ion batteries; Microlevelling; Rare-earth cations; Zinc anodes; Zinc dendrites.

Fig. 1

Schematic illustrations of the zinc–electrolyte interface in different electrolytes. a Solvated Zn²⁺ ions adsorb on protrusions due to the concentration of electric field, resulting in rampant dendrite growth in the ZSO electrolyte. Meanwhile, the water-rich EDL at the interface leads to severe HER upon zinc deposition. b Adsorbed Gd³⁺ ions activate the microlevelling effect by forming an electrostatic shielding layer at the interface and repels water molecules from the EDL, enabling smooth zinc deposition and suppressing HER in the ZSO/Gd³⁺ electrolyte. The gray dashed line represents the virtual profiles of the electric field

Fig. 2

Characterizations of the electrolytes. a Raman spectra of the ZSO and ZSO/Gd³⁺ electrolytes with different Gd³⁺ concentrations. b Deconvolution of HBs and c corresponding ratios of different HB types in the electrolytes. d Absorption energies of Gd³⁺, Zn²⁺, and H₂O on the zinc (002) surface. e Binding energies of Gd³⁺ and Zn²⁺ to H₂O. f Calculated solvation structures of Gd³⁺ ions with H₂O

Fig. 3

Zinc deposition behaviors in different electrolytes. SEM images of the zinc deposited at 1 mA cm⁻² for 1 h in a ZSO and b ZSO/Gd³⁺ electrolytes. c In situ optical microscopy images of the zinc deposits obtained in different electrolytes. 3D-CLSM images of the zinc after cycling for 1 h in d ZSO and e ZSO/Gd³⁺ electrolytes

Fig. 4

Zinc–electrolyte interface stability in different electrolytes. SEM and EDS images of the zinc surface immersed in a ZSO and b ZSO/Gd³⁺ electrolytes for 6 days. c XRD patterns of the zinc foil after immersion tests. Schematic illustrations of the EDL structures in d ZSO and e ZSO/Gd³⁺ electrolytes. f Tafel, g differential capacitance, h LSV and i CA curves of zinc electrodes tested in ZSO and ZSO/Gd³⁺ electrolytes

Fig. 5

Electrochemical reversibility and stability of zinc metal anodes. a EIS curves of the Zn//Zn symmetric cells with the ZSO/Gd³⁺ electrolyte at different temperatures. b Activation energies of Zn²⁺ desolvation in different electrolytes. c CV curves of Zn//Cu batteries with ZSO and ZSO/Gd³⁺ electrolytes. Cycling performance of Zn//Zn symmetric cells at d 1 mA cm⁻², 1 mAh cm⁻² and e 5 mA cm⁻², 2 mAh cm⁻². f SEM images of the zinc anodes cycled in Zn//Zn symmetric cells. g Schematic illustrations of the zinc deposition behaviors in different electrolytes

Fig. 6

Electrochemical performance of ZSO/Gd³⁺ electrolyte. a CE of zinc plating/stripping in Zn//Cu batteries at 2 mA cm⁻² and 1 mAh cm⁻². Voltage–capacity curves of Zn//Cu batteries with b ZSO and c ZSO/Gd³⁺ electrolytes. d EIS and e CV curves of Zn//NVO full cells. f Cycling performance of Zn//NVO full cells at 5 A g⁻¹. SEM images of the zinc anodes obtained in full cells with g ZSO and h ZSO/Gd³⁺ electrolytes after 1000 cycles at 5 A g⁻¹. i Rate performance of Zn//NVO full cells at different current densities