Preparation Of Solid Electrolyte And Investigation On Micromechanism Of The Electrode-Electrolyte Interface In Lithium Metal Batteries

Lithium(Li)metal has been pursued as the most promising anode for high energy density electrochemical systems,and these high specific energies derive from the high theoretical specific capacity(3860 mAh g-1),low density(0.59 g cm-3)and the lowest negative electrochemical potential(-3.04 V vs.the standard hydrogen electrode)of the Li metal.However,the issue of uncontrollable Li dendrite growth,causing by irregular lithium deposition,restricts the wide applications of Li metal based high energy batteries.In this thesis,we intend to modulate uniform Li deposition by novel solid electrolyte and modified electrode-electrolyte interface to suppress uneven Li dendrite growth.The mechanisms of Li-ion transportation in solid electrolyte and the Li deposition on the modified interface were fully investigated.The electrochemical performances in these systems show that both the methods can greatly improve the stability of Li metal anodes.The main research contents and results are summarized as following:1.Solid-liquid electrolytes(SLEs)with well-aligned nanopores were fabricated via absorbing polyethylene glycol(PEG)engineered nanoporous Al2O3 ceramic membranes with liquid electrolytes.The SLEs show high ionic conductivity,low Rint,high mechanical modulus and good stability against Li anode at both room and elevated temperatures.The materials were assembled as Li/Li4Ti5O12 half cells to investigate their longtime cycling performance.These measurements show more than 1000 charge/discharge cycles can be achieved with no evidence of dendritic deposition.2.The transport mechanism of Li+ in the two phases were analyzed by using molecular dynamics simulations.The results indicated that the SLEs can make homogeneous Li+ distribution and rapid transportation in its two special nanophases.This configuration facilitates the application of LMBs with stable Li deposition and long lifetime performance and can be used in next-generation energy storage systems for advanced stable battery technologies.3.A platinum modified polypropylene separator were prepared by a one-step sputter technology.Pt nanolayers with good electronic conduction provide Li deposition sites during repeated charging/discharging.Moreover,Pt nanolayers can enhance the mechanical properties and micro-structures of commercial polypropylene separators.This system achieved the bidirectional growth of Li dendrites,which efficiently filled gaps between Pt layers and Li anodes by integrating dead Li and Li dendrites into smooth and dense Li layer.The symmetric Li|PP@Pt|Li cells exhibit low overpotentials,dense Li anode and strong tolerance under high current densities.Meanwhile,Li/LiFeP04 cells present excellent electrochemical performance with an average specific capacity of 131 mAh g-1 at 1 C.The Pt modified PP separator not only ensures stable cycling performance and practical application,but also possesses ease to be fabricated,which makes it possible to be used in advanced metallic batteries.