Research On The Application Of Substrate Modification In Lithium Dendrite Inhibition And Lithium Metal Batteries

Lithium metal negative electrode has received much attention due to its advantages such as high theoretical specific capacity(3860 m Ah g^-1),low density(0.534 g cm^-3)and low REDOX potential（-3.04 V vs.SHE）.However,during charging and discharging,dendrite growth,interfacial side reactions and volume expansion of the lithium cathode severely hinder the practical application of lithium metal batteries.To address the above issues,researchers have mainly modified substrates,solid electrolyte interface membranes,electrolyte regulation,diaphragm modification,and other methods for improvement.In this paper,we study the deposition behavior of lithium on different lithium alloy substrates to modify the substrate and improve the electrochemical properties of lithium metal batteries by exploiting the suppression effect of lithium alloy substrates on lithium dendrites.The main work contents are as follows:（1）Taking Li₉Ag_4,Li₁₅Au₄,Li Zn,Li₉Al₄,Li₁₃In₃and Li₁₃Sn₅ lithium alloys as substrates,the deposition behavior of lithium on different alloy substrates was studied by electrochemical characterization,morphological characterization and in-situ observation.It has been shown that lithium nucleation and deposition potentials are lower on the surface of alloy substrates compared to copper foil substrates,with evidence from small to large for Ag,Zn,Al,Au,In,Ti,Sn,Cu.This indicates that the lithium alloy substrate successfully reduces the lithium nucleation barrier and promotes the uniform deposition of lithium.At the same time,the morphology of lithium nucleation deposition on the surfaces of different alloy substrates and copper foil substrates was tested at low current densities,and it was found that uniform and dense lithium deposition occurs on the surfaces of Li₉Ag₄,Li Zn,Li₉Al₄,Li₁₅Au₄ and other alloy substrates.Li₁₃In₃ and Li₁₃Sn₅show wavy and flower-like lithium deposits with uneven folds,respectively,and irregularly clustered lithium deposits appear on the surface of the Ti basement.The results of in-situ tests indicate that the nucleation excess potential and the morphology of the nucleated deposition of lithium on different substrate surfaces affect the subsequent lithium dendrite growth and the battery cycle performance.（2）Based on the research on the deposition behavior of lithium on different lithium alloy substrates,the substrates were further modified based on lithium zinc alloy and combined with three-dimensional structure.By combining 3D carbon cloth（CC）with Zn O quantum dots,carbon cloth coated with Zn O quantum dots was constructed,and then reacted with molten lithium at high temperature to form Li/Li Zn/CC composite negative electrode.The Li Zn alloy has a high adsorption energy（1.89 e V）for lithium atoms,and the lithium has a suitable diffusion energy barrier（0.68 e V）on the surface,which can promote the uniform deposition of lithium.The 3D structure of CC can reduce the local current density at the electrode surface,which further suppresses the growth of lithium dendrites.Therefore,with Li/Li Zn/CC as the electrode,the symmetric cell can work stably for more than 2700 hours with the low current density of 1 m A cm^-2 and the capacity of 1 m Ah cm^-2,and achieve a stable cycle of more than1900 hours with the high current density of 10 m A cm^-2 and the high capacity of 20m Ah cm^-2.It also exhibits excellent electrochemical properties throughout the battery.（3）The porous TiC/CC substrate material was prepared by rapid heating and cooling of Ti O₂/CC with Joule heater,and the TiC/CC substrate was applied to both lithium negative electrode（Li/TiC/CC）and sulfur positive electrode（S/TiC/CC）.The TiC/CC base can not only improve the electrode conduction rate and reduce the effective current density,but also locally anchor and fix the polysulfide due to the interaction between Ti-S when used in the positive sulfur electrode,which better regulates the main sulfur REDOX kinetics and significantly inhibits the shuttle effect of the polysulfide.Thus,in symmetric cells assembled with Li/TiC/CC electrodes,the high current density of 10 m A cm^-2 and the high deposition of 20 m Ah cm^-2 can be continuously and stably operated for more than 500 hours,and in the application of Li-S batteries,The Li-S battery which combines the negative Li/TiC/CC electrode and the positive S/TiC/CC electrode has stable cycle performance and excellent multiplier performance.