Fabrication And Characterization Of Solution-phase-inversion-derived Straight-pore Electrode And Porous Copper Current Collector

As one of the most important electrochemical energy storage and conversion systems,rechargeable lithium batteries are required to achieve higher energy density and power density.An effective way to attain this goal is to optimize the microstructure of electrodes.When thick electrodes work in a high rate,Li+ diffusion in the long and winding transport path in electrode would cause high resistance,which may lead to concentration polarization and poor rate performance.To solve this problem,we have put forward a new method,phase inversion method,to fabricate LiFePO4 electrode with straight pores and investigated the effect of the novel structure on electrochemical performance.Another way to break the bottleneck is replacing the anode and cathode with alternative materials.Li metal is considered to be ideal anode because of its ultra-high energy density and very low redox potential.However,the formation of Li dendrites brings safety hazards into batteries.In this dissertation,porous copper current collector was fabricated by phase inversion method,and it was used to accommodate Li metal and optimize the electrochemical performance of Li metal batteries.The first part of this dissertation is to investigate the preparation processes and experiment parameters of phase inversion method,as well as their effect on electrochemical performance of LiFePO4 electrode.We found out that straight pores can be created when chose NMP as solvent,PVDF as binder and water bath at 10℃.Electrochemical tests proved that straight pores help to reduce concentration polarization in high loading density and high rate.The electrode fabricated by phase inversion method showed better electrochemical performance.The second part of this dissertation is to fabricate porous copper via phase inversion method and thermal treatment.When it was used as current collector in Li metal battery,the large surface provided sufficient area for the deposition of Li metal,and porous structure help to inhibit the formation of Li dendrites.The Li metal battery with porous copper current collector exhibited excellent cycling performance:its Coulombic Efficiency was higher than 96%for 225 cycles and its lifespan was up to 470 hours in a symmetric Li|Li@Cu cell,when it was cycled at a fixed current density of 1 mA cm-2 with a string/plating capacity of 1 mAh cm-2 for each cycle.