Structural Design And Performance Study Of Dendrites-free Lithium Metal Anode

Lithium metal has a high theoretical specific capacity(3860 m Ah g^-1)and low redox potential（-3.04 V vs.SHE）,which has great potential for development,and lithium metal batteries using it as anode material have received a lot of attention from researchers.However,the uncontrolled growth of lithium dendrites during the cycle of lithium metal batteries can lead to lower energy density,shorter cycle life and battery safety problems caused by puncturing the diaphragm during application,which seriously limits their practical applications.In this thesis,the uncontrolled growth of lithium dendrites is investigated,and the introduction of lithium-friendly elements to prepare alloy electrodes and the construction of three-dimensional porous electrodes loaded with lithium is proposed to achieve effective regulation of the uniform deposition of lithium metal.The main research contents are as follows:Firstly,an alloy-coupled diffusion-regulated lithium deposition mechanism is proposed to design and prepare ultrathin low-melting-point Sn-Bi-In ternary alloy electrodes to study their lithiation reaction process and lithium metal electrodeposition behavior.Specifically,the 8μm-thick Sn-Bi-In metal alloy foil electrode was prepared by melting-rolling method to study its electrochemical lithium alloying reaction process,lithium metal pre-deposition process and reversible electrochemical reaction process of lithium deposition/stripping.Combining a series of characterization tools and electrochemical tests such as constant current charge/discharge and impedance,the phase transformation and microscopic morphology evolution of the electrode were systematically investigated,and a high deposition volume of 196.3 m Ah cm^-2 and uniform deposition of dendrite free lithium were achieved.When matched with Li Fe PO₄ cathode to assemble the full cell,the capacity retention rate is 92.9%and the Coulomb efficiency is 98.69%after 600 cycles at 1C magnification.Secondly,nanoporous metal substrates with open porous structure,high electrical conductivity,high porosity and lithium affinity were designed to investigate the effects of porous structure and lithium affinity sites on lithium metal deposition.Specifically,three-dimensional nanoporous MgNi₂ was prepared by Vapor Phase Dealloying,and then electrochemically pre-deposited to form three-dimensional nanoporous composite electrode Li/MgNi₂,combined with a series of characterization means to study the structural evolution of three-dimensional nanoporous MgNi₂preparation process;using electrochemical testing methods to systematically study the three-dimensional nanoporous MgNi₂ composite electrode.The electrochemical performance of the Li/MgNi₂ composite electrode was systematically investigated using electrochemical testing methods.When the deposition amount reached 1 m Ah cm^-2 with a stable cycle of 260 h,the Coulomb efficiency was maintained at 100%,and the three-dimensional porous structure and the induction of lithium homogeneous deposition by the lithium-loving Mg component were realized,and the growth of lithium dendrites was inhibited.