Research Of Inhibiting Lithium Dendrite Growth By Interfacial And Membrane Modification

The rapid development of green energy puts forward higher requirements for energy storage devices.Lithium-ion battery is widely recognized for its long service life and many other advantages.It has become the most mainstream energy storage equipment.However,in the foreseeable future,the energy density of lithium-ion batteries will reach its limit,which cannot meet the demand for higher energy density energy storage equipment.Therefore,it is urgent to seek better materials to achieve higher energy density batteries.Lithium metal has a theoretical specific capacity of 3860 mAh g-1,and the lowest electrochemical potential of-3.04 V,which makes lithium metal the most ideal material for negative electrode.However,in the continuous charge and discharge process of the battery,uncontrollable lithium dendrite growth has become the trickiest problem in the practical application of lithium metal battery.The growth of lithium dendrites will not only shorten the cycle life of the battery,reduce the coulomb efficiency,and even bring safety hazards such as short circuit,which makes the lithium metal battery unable to be commercialized.Therefore,it is of great research value and practical significance to find a method to inhibit lithium dendrites and improve the safety and cycle stability of lithium metal batteries.Aiming at the dendrite problem of lithium metal anode,this paper adopts two methods including lithium metal surface modification and separator coating to inhibit lithium dendrite,so as to improve the electrochemical performance and safety performance of lithium metal battery.The specific research contents are as follows:(1)The suppression of lithium dendrites in all solid-state lithium metal batteries based on SnI2 interface modification.SnI2 was used to modify the surface of lithium metal anode,and an ion/electron double conductive layer composed of Sn and LiI was formed in situ.The protective layer provides more nucleation sites for the deposition of lithium ions,makes the current distribution more uniform,promotes the uniform deposition of lithium ions,and inhibits the formation of dendrites.At the same time,PEO based all solid electrolyte is used to further improve the safety of the battery.The modified lithium metal electrode shows better cycle stability in both of symmetrical battery and LiFePO4 full battery,and the surface morphology of cycled lithium sheet is much denser and more uniform.This method also provides an idea for the suppression of dendrites in other metal electrodes.(2)The suppression of lithium dendrites based on multi-layer TiO2 modified separator.Anatase TiO2 with laminated structure was prepared and then sprayed on the surface of PE separator as a functional material to achieve TiO2 composite separator.The coating not only improves the thermal stability and wettability to the electrolyte of the separator,but also reduces the nucleation barrier of lithium ion.It also restrains side reaction,and then inhibits the formation of lithium dendrites.In carbonate electrolyte,the symmetrical battery and LiNi0.5Mn1.5O4 full battery composed of composite separator showed improved performance,and there was no obvious dendrite formation on the surface of lithium sheet after battery cycling.In addition,the whole process of this modification method is carried out in the air without special atmosphere protection,which is more conducive to industrialization.