Recent Progress and Prospects on Dendrite-free Engineerings for Aqueous Zinc Metal Anodes

Rechargeable zinc-ion batteries with mild aqueous electrolytes are one of the most promising systems for large-scale energy storage as a result of their inherent safety,low cost,environmental-friendliness,and acceptable energy density.However,zinc metal anodes always suffer from unwanted dendrite growth,leading to low Coulombic efficiency and poor cycle stability and during the repeated plating/stripping processes,which substantially restrict their further development and application.To solve these critical issues,a lot of research works have been dedicated to overcoming the drawbacks associated with zinc metal anodes.In this overview,the working mechanisms and existing issues of the zinc metal anodes are first briefly outlined.Moreover,we look into the ongoing processes of the different strategies for achieving highly stable and dendrite-free zinc metal anodes,including crystal engineering,structural engineering,coating engineering,electrolyte engineering,and separator engineering.Finally,some challenges being faced and prospects in this field are provided,together with guiding significant research directions in the future.

Prestoring lithium into SnO_(2)coated 3D carbon fiber cloth framework as dendrite-free lithium metal anode

For several decades,the promise of implementing of lithium(Li)metal anodes has been regarded as the"holy grail"for Li-based batteries.Herein,we have proposed a facile design of a carbon fiber cloth(CFC)framework coated with SnO_(2)nanoparticles through a hydrothermal process,which served as a reliable host for prestoring molten Li to produce a CFC@SnO_(2)@Li composite anode.XRD,TEM,HRTEM,XPS and different electrochemical characterizations were carried out.Owing to the synergetic effects of the 3D conductive CFC and the coated lithiophilic SnO_(2)nanoparticles,the designed CFC@SnO_(2)@Li electrodes can buffer the volume changes and reduce the local current density,thus suppress the Li dendrites during cycling.Consequently,the CFC@SnO_(2)electrodes showed a high and stable CE of 98.6%for 1000 cycles at a current density of 1 mA cm^(-2)(1 mAh cm^(-2)).What is more,at a high current density of 5 mA cm^(-2)and a high areal capacity of 5 mAh cm^(-2),the symmetric cell displayed relatively low overpotential and long cycling lifetime of 1600 h.The results confirm its great potential as lithium metal anodes in practical battery applications.

Metal–organic framework-derived Co_(3)O_(4)modified nickel foam-based dendrite-free anode for robust lithium metal batteries

For several decades,the promise of implementing of lithium(Li)metal anodes for Li batteries has been a"holy grail"for researchers.Herein,we have proposed a facile design of a MOF-derived Co_(3)O_(4)nanoparticles modified nickel foam,i.e.,Co_(3)O_(4)-NF,as a 3D host to achieve a uniform infusion of the molten Li.The molten Li was uniformly absorbed on the Co_(3)O_(4)-NF host only in 10 s due to its high Li lithiophilicity.The obtained Li-Co_(3)O_(4)-NF composite electrode shows high cycling stability in symmetric cells with low voltage hysteresis even at a high current density of 5 mA/cm2.The full cells of Li-Co_(3)O_(4)-NF/LiFePO_(4)can cycle for more than 500 cycles at 2C without obvious capacity decay.SEM after cycling and in situ optical microscope results suggest that the unique 3D host structure of the Li-Co_(3)O_(4)-NF anode plays key roles on suppressing the dendrite growth and decreasing the local current inhomogeneity.We believe this work might provide a new strategy for fabricating dendrite-free Li metal anodes and facilitate practical applications in Li batteries.

锂离子电池的电化学阻抗谱分析

电化学阻抗谱(EIS)是研究电极/电解质界面发生的电化学过程的最有力工具之一,在过去的20多年中,EIS被广泛应用于锂离子电池研究和生产领域,包括研究电极界面反应机理和容量衰减机制,测定相关电极过程动力学参数和电池的健康状态、荷电状态以及电池的内阻。本文分析了锂离子电池中电极极化过程包含的3个基本物理化学过程——电子输运、离子输运和电化学反应过程,探讨了每一基本物理化学过程包含的步骤及其EIS谱特征,详细论述了与电子输运相关的基本物理化学过程——接触阻抗和感抗产生的机制;介绍了多孔电极理论及其在锂离子电池中的应用,阐述了基于多孔电极理论进行阻抗谱数值模拟的建模原理与方法。综述了石墨、硅、二元3d过渡金属氧化物、LiCoO2、尖晶石LiMn2O4、LiFePO4、尖晶石Li4Ti5O12、过渡金属氟化物材料等电极的典型阻抗谱特征和各时间常数的归属问题。最后讨论了EIS现存的问题及未来的发展方向。