Structural Design And Interface Control Of Electrode Materials For Aqueous Zinc Secondary Batteries

Aqueous zinc secondary batteries are expected to be used for large-scale energy storage due to their low cost,high safety,and environmental friendliness.Nonetheless,the slow Zn²⁺diffusion kinetics and structural instability of traditional cathode materials lead to rapid capacity decay of aqueous zinc secondary batteries.At the same time,the phenomena such as dendrite growth,hydrogen evolution,and corrosion of the metal Znanode lead to the low coulombic efficiency and poor reversibility of Znanode,which critically hinder the practical application of aqueous zinc secondary batteries.Therefore,a stable and fast Zn²⁺transport channel is constructed and the Zn²⁺deposition/dissolution kinetics are improved by optimizing the structural design and regulating the reaction interface,which significantly improves the reversibility and cycling stability of the cathode and anode materials,and provides the material basis and theoretical support for the construction of long cycle life aqueous zinc secondary batteries.The main research contents and results are as follows:（1）In view of the poor cycle stability and low Znstorage capacity of the cathode material MoS₂,hydrated MoS₂ material with wide layer spacing was prepared by hydrothermal method.The research shows that the introduction of crystal water not only effectively shields the electrostatic interaction between the material and Zn²⁺,reduces the Zn²⁺intercalation/extraction barrier,but also widens the interlayer spacing and improves the Zn²⁺intercalation/extraction kinetics,thereby significantly improving the cycle stability.（2）The low reversibility and poor cycle stability of Znanode are one of the key factors restricting the cycle life of aqueous zinc secondary batteries.Aiming at the dendrite problem caused by the uneven diffusion of Zn²⁺on the Znmetal surface,a Znanode（RT-Znelectrode）with（002）plane orientation was constructed by electrochemical deposition and the effect of crystal plane orientation on Zndeposition behavior was studied.The research shows that the more exposed（002）crystal plane is beneficial to controlling the plating/stripping behavior of Zn,promoting the preferential deposition of Znalong this crystal plane,avoiding the growth of dendrites,and improving the cyclic stability of the Znanode electrode.（3）To increase deposition active sites,a three-dimensional heterometallic protective layer（Zn/Sn）was constructed on the Znmetal surface by solution replacement reaction.The research shows that the modified layer not only provides abundant nucleation sites,decreases the nucleation barrier,relieves the growth of dendrites,but also reduces the local current density,decreases the volume expansion of the Znanode during cycling and increases the reversibility of the Znanode.（4）To achieve the stability of the Znanode electrode at high discharge depth,a multi-channel insulating ZnO modified layer was prepared by the chemical oxidation method.The research shows that the modified layer not only adjusts the concentration of Zn²⁺near the electrode,guides the uniform deposition of Zn,but also significantly reduces the desolvation activation energy of hydrated zinc ions,accelerates the plating/stripping kinetics of Zn,and increases the cycle life of the Znanode at high discharge depth.（5）The electrochemical performance of intercalated materials as anodes for aqueous zinc secondary batteries was also explored.An intercalated Znstorage anode material,TiS_2-x,was prepared by the gas-phase anion exchange reaction between CS₂ and TiN.The results show that the introduction of defects in TiS_2-x material not only increases the active site of Znstorage,speeds up the transport speed of Zn²⁺,but also avoids the structural change of Zn²⁺during the process of Zn²⁺intercalation/extraction.The full cells constructed by matching it with the Zn_xMn O₂ cathode material have a voltage window of 1.0 V and a high specific capacity of 102.9 m Ah/g,which indicates that TiS_2-x has good ion migration kinetic and thermodynamic stability,and it is a promising anode material for Znstorage.