Design And Performance Study Of Three-Dimensional Hosts For Zinc Metal Anodes

As an ideal anode for AZIBs,metallic Zn is favored by the eminent merits such as moderate chemical reactivity in water,high security,large volumetric capacity,and suitable redox potential.Nevertheless,the problems such as uncontrolled formation of Zn dendrites,the chemical/galvanic corrosion,hydrogen evolution reaction（HER）and passivation still severely hamper the industrialization of Zn metal batteries.Combining with the structural design and surface modification strategies,we have designed the various 3D zincophilic hosts with hollow or porous structure to effectively induce the Zn deposition within the frameworks,thereby sufficiently suppressing the dendrites growth and the detrimental parasitic reactions.Details are listed as follows:（1）The host design strategy as a practical and scalable method could effectively actualize a systematic manipulation of Zn deposition by optimizing the process of diffusion,adsorption,nucleation,and growth.In the Part I,we designed a spatial confinement approach for stable ZMAs using the highly ordered Ti O_x/Zn/N-doped carbon inverse opal（denoted as TZNC IO）host through the colloidal crystal templating and the subsequent stepwise topochemical reactions.Of note,the 3D macroporous framework with periodic structure could precisely control the electric field distribution and minimize the local current density to induce the preferential Zn deposition within the TZNC host.The sufficient void space within the interconnected pores could effectively regulate Zn ion fluxes and alleviate volume expansion.More importantly,the well-distributed amorphous Ti O_x and Zn/N-doped carbon could serve as the zincophilic sites to reduce the nucleation overpotential and avoid the production of hydrogen bubbles.As expected,the TZNC host enabled dendrite-free Zn deposition with a compact surface.Furthermore,the corresponding symmetric cell using the TZNC@Zn electrode exhibited low voltage hysteresis at various current densities and long-term cycling stability（over 450 h）.In addition,an aqueous full cell using the TZNC@Zn composite anode and V₂O₅ cathode demonstrated a stable lifespan over repeated 2000 cycles.（2）Anchoring zincophilic sites on the surface of hosts could minimize nucleation energy barrier by providing a strong adsorption to metallic Zn,thereby promoting a homogeneous Zn nucleation.In the Part II,we introduced the Sn as the zincophilic seeds in the Ti O₂ inverse opal（Ti O₂/Sn）to construct the highly ordered zincophilic host for stable ZMAs.The highly ordered macroporous framework could effectually homogenize the electric field distribution and reduce the local current density,thereby achieving re-distribution of Zn ion flux.The sufficient void space within the framework could effectively alleviate volume expansion.More importantly,the well-distributed Sn could serve as the zincophilic sites to induce the preferential Zn deposition within the Ti O₂/Sn host,thus suppressing the dendrites growth and the detrimental parasitic reactions.As expected,Ti O₂/Sn host showed almost negligible nucleation overpotential and high average CE of 99.82%over 800cycles.Moreover,the corresponding symmetric cell using the Ti O₂/Sn@Zn electrode exhibited a long cycle life over 1850 h at 1 m A cm^-2 with a fixed capacity of 1 m Ah cm^–2.Moreover,a full cell assembled by the Ti O₂/Sn@Zn anode and a commercial V₂O₅ cathode exhibited excellent reversibility and good cycling stability over 2000 cycles.（3）On the basis of the above works,we designed a Sn/TiO₂ encapsulated hollow mesoporous carbon sphere array with highly ordered opal structure（HMCSST）as the 3D zincophilic host for high-performance ZMAs.The HMCSST with hierarchically gradient porous structures could enable the fast mass transfer from the solutions to inner zincophilic sites,achieving the preferential Zn deposition within the hosts.Besides,the Ti O₂/Sn nanoparticles on the surface of hosts could both reduce the overpotential and suppress the HER.Benefitting from the ordered gradient porous structure with abundant zincophilic sites,HMCSST host and the corresponding HMCSST-Zn||HMCSST-Zn symmetric cell exhibited remarkable electrochemical properties in terms of high CE,fast deposition kinetics,and prolonged cycling stability.A full cell based on the designed HMCSST-Zn anode and the V₂O₅cathode demonstrated superior rate capability and stable cycle life.