Stabilization of Zn Metal Anode through Surface Reconstruction of a Cerium-Based Conversion Film

Corrosion and dendritic deposition have been the long-standing interfacial challenges of Zn anode, resulting in the deterioration of the aqueous zinc-based batteries. Herein, the surface of Zn metal anode is pioneeringly reconstructed by a cerium-based conversion film (Zn@CCF) through a chemical conversion method. Faster growth of the film in the vicinity of zinc grain boundaries significantly prevents the substrate from genetic micro-corrosion that leads to catastrophic damage. The affinity of the film toward zinc facilitates a low nucleation barrier and smooth zinc deposition. Consequently, Zn@CCF enables long-term lifespan (1200 h) with low polarization ( ≈ 60 mV) at 4.4 mA cm⁻², which also maintains good capacity retention and excellent cycling stability of Zn@CCF/MnO₂ full cells. This facile and effective approach helps suppress Zn dendrite formation and brings forward the significance of surface reconstruction of the Zn metal anode for corrosion inhibition, which can be potentially applied to other metal anodes in aqueous energy storage systems.     

A Lean-Zinc and Zincophilic Anode for Highly Reversible Zinc Metal Batteries

Lean-zinc anode is a promising configuration that can eliminate the trade-off of energy density and cycle lifetime of zinc metal (Zn⁰) batteries. However, there are rare investigations of lean-Zn anode designs and it remains a grand change to sustain high zinc reversibility under lean zinc conditions. Herein, a lean-Zn anode design based on a hierarchical and zincophilic cobalt metal (Co⁰) nanowire-decorated carbon host, which is derived from a ZnCo bimetallic organic framework, is reported. Within the lean-Zn anode, the trace amount of Zn⁰ acts as a zinc reservoir to make up for any irreversible loss of zinc source upon cycling, while the zincophilic Co⁰ nanowires can guide uniform zinc nucleation and growth through a lattice matching mechanism. Consequently, high Zn⁰ reversibility (average Coulomb efficiency of 99.6% for 4250 cycles), low nucleation overpotential (50.8 mV at 1 mA cm⁻²), and uniform and compact zinc electrodeposition are realized. When coupling the lean-Zn anode with a Zn-containing cathode, the full cell delivers high Coulomb efficiency (99.6% for 4250 cycles on average) and a long lifetime of more than 5000 cycles.     

A Rooted Multifunctional Heterogeneous Interphase Layer Enabled by Surface-Reconstruction for Highly Durable Sodium Metal Anodes

Sodium plating–stripping with high reversibility is still an intractable challenge for sodium metal-based batteries due to the fragile natural solid-electrolyte interphase (SEI) film and severe Na dendrites growth. Herein, a surface reconstruction strategy is proposed and a rooted heterogeneous interlayer derived from in situ reactions between tin selenide and Na metal (abbr. Na/SnSe) is produced to regulate Na⁺ deposition behavior and impede dendrite growth. The high sodiophilic Na₁₅Sn₄ component demonstrates the robust combination and dendrite suppression capability, inhibiting fracture and delamination problems during volume variation. Meanwhile, the superionic Na₂Se ingredient contributes to the optimized Na⁺ conduction efficiency and low nucleation overpotential, enabling uniform distribution of electrical fields and ultimately eliminating Na dendrites. Consequently, the reconfigured multifunctional Na/SnSe interphase realizes a long-term lifespan over 2400 h at 0.5 mA cm⁻²/1 mAh cm⁻² in symmetric cell with an extremely low voltage hysteresis. Moreover, the assembled Na/SnSe||NaNi_1/3Fe_1/3Mn_1/3O₂ pouch cell achieves exceptional cycling stability and capacity retention (90.4 mAh g⁻¹ after 1800 cycles at a high current density of 2 A g⁻¹), exploiting an avenue for designing durable SEI layer and high-quality sodium metal batteries.     

Outer Helmholtz Plane Regulation and In Situ Zn Surface Reconstruction for Highly Reversible Zn Anodes

Metallic Zn, a promising anode for aqueous energy storage devices, suffers from uncontrolled dendrite growth and corrosion, leading to a short cycle life and low Coulombic efficiency (CE) in Zn-based batteries. Herein, a composite electrolyte including zinc sulfate, copper(II) chloride, and poly(N-diallyldimethylammonium chloride) (PDADMAC), denoted as PDADMAC–CuCl₂–ZnSO₄, is applied to simultaneously reconstruct the outer Helmholtz plane (OHP) and homogenize the Zn surface for highly reversible Zn anodes. The results of characterization, namely Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, density functional theory calculations, and electrochemical tests, confirm that the addition of chloride ions promotes the adsorption of PDADMAC on the OHP of the electric double layer and controls the Zn deposition process by regulating the electric field. Simultaneously, in situ Zn surface homogenization is accomplished by the reaction of Cu²⁺ on the Zn surface. As a result, the highly reversible Zn anode sustains extremely long-term cycling for 2407 h at 5 mA cm⁻² with 5 mAh cm⁻² and 1300 h at 10 mA cm⁻² with 10 mAh cm⁻² in Zn//Zn symmetrical cells. A high average CE of 99.3% is achieved over 430 cycles at 15% depth of discharge.     

Reconstruction of Electric Double Layer for Long-Life Aqueous Zinc Metal Batteries

Aqueous rechargeable Zn metal batteries (AZMBs) have attracted widespread attention due to their intrinsic high volumetric capacity and low cost. However, the unstable Zn/electrolyte interface causes Zn dendrite growth and side reactions, resulting in poor Coulombic efficiency and unsatisfactory lifespan. Herein, a SiO₂ reinforced-sodium alginate (SA) hybrid film is designed to regulate solid–liquid interaction energy and spatial distribution of all species in the electric double layer (EDL) near the Zn electrode. The unique interfacial layer gives rise to a uniform distribution of Zn²⁺ in the Helmholtz layer through solvation sheath modulation. Moreover, theoretical calculations show that the SO₄²⁻ anions and free-water are substantially reduced in the Helmholtz layer, effectively suppressing hydrogen evolution reaction and formation of by-products through strong charge repulsion and hydrogen bond fixing of free-water. The reconfigured EDL not only ensures homogenous and fast Zn²⁺ transport kinetics for dendrite-free Zn deposition, but also eliminates interface parasitic side reactions. The Zn@SiO₂-SA electrode enables excellent cycling stability of symmetrical cells and high-loading full AZMBs with a lifespan over 3000 h and an areal capacity of 2.05 mAh cm⁻², thus laying a solid basis for realizing practical AZMBs.     

Regulation of Ionic Distribution and Desolvation Activation Energy Enabled by In Situ Zinc Phosphate Protective Layer toward Highly Reversible Zinc Metal Anodes

Despite the merits of high specific capacity, low cost, and high safety, the practical application of aqueous Zn metal batteries (AZMBs) is plagued by the dendritic growth and corrosion reaction of Zn metal anodes. To solve these issues, a Zn₃(PO₄)₂·4H₂O protective layer is in-situ constructed on Zn foil (Zn@ZnPO) by a simple hydrothermal method, avoiding the traditional slurry-casting process. The insulating and conformable ZnPO layer improves the wettability of Zn@ZnPO and aqueous electrolyte via decreasing the contact angle to 11.7^o. Compared with bare Zn, the Zn@ZnPO possesses a lower desolvation activation energy of 35.25 kJ mol^-1, indicating that the ZnPO fasters the desolvation of hydrated Zn²⁺ ions and thereby ameliorates their transport dynamics. Micro-morphology and structural characterization show that there are no dendrites forming on the post-cycling Zn@ZnPO anodes, and the interfacial ZnPO layer remains almost identical before and after cycles. It can be explained that the electrochemically stable ZnPO layer acts as an ionic modulator to enable the homogeneous distribution of Zn²⁺ ions, inhibiting the growth of Zn dendrites. Benefiting from these advantages, the Zn@ZnPO based symmetric and full cells deliver highly reversible Zn plating/stripping behavior and long cycling lifespans.     

Tungsten‐Doping‐Induced Surface Reconstruction of Porous Ternary Pt‐Based Alloy Electrocatalyst for Oxygen Reduction

Surface engineering has been found to be effective in promoting the catalytic activities of noble‐metal‐based nanocatalysts. In this contribution, by using the PtCu_xNi ternary alloy nanocrystal (NC) as the model catalyst, a surface tungsten(W)‐doping strategy, combining a surface oxidative acid treatment protocol, can effectively boost the electrocatalytic activities of the NCs in oxygen reduction reaction. The W‐doped PtCu_xNi alloy catalysts show obvious enhancement in electrochemical surface area and mass activity and slightly enhanced specific activity compared with the undoped catalyst. Based on the experimental evidence, it is proposed that the W doping involves a surface reconstruction by first removing the surface Pt atoms from the NC and then reducing them back to the surface. The existence of surface Ni atoms may be crucial in promoting the catalytic activities possibly through their electronic interactions to the active sites. The durability of the W‐doped PtCu_xNi catalysts is also enhanced possibly due to the pinning effect of surface W atoms. Therefore, the surface engineering of PtCu_xNi ternary alloy by W atoms can effectively modulate its activity and durability.     

A Sieve‐Functional and Uniform‐Porous Kaolin Layer toward Stable Zinc Metal Anode

Zinc metal is considered as one of the best anode choices for rechargeable aqueous Zn‐based batteries due to its high specific capacity, abundance, and safety. However, dendrite and corrosion issues remain a challenge for this system. Herein, sieve‐element function (selective channel of Zn²⁺) and uniform‐pore distribution (≈3.0 nm) of a kaolin‐coated Zn anode (KL‐Zn) is proposed to alleviate these problems. Based on the artificial Zn metal/electrolyte interface, the KL‐Zn anode not only ensures dendrite‐free deposition and long‐time stability (800 h at 1.1 mA h cm^?2), but also retards side reactions. As a consequence, KL‐Zn/MnO₂ batteries can deliver high specific capacity and good capacity retention as well as a reasonably well‐preserved morphology (KL‐Zn) after 600 cycles at 0.5 A g^?1. This work provides a deep step toward high‐performance rechargeable Zn‐based battery system.