Design And Electrochemical Property Of Lithium Metal Anode Collector

Due to the limited theoretical capacity of graphite anode(372 mAh g^-1),lithium ion batteries are difficult to meet the needs of large electric equipment such as electric vehicles for high stability,high energy density and ultrafast charge and discharge.Lithium metal anodes have ultra-high theoretical capacity(3860 mAh g^-1)and the lowest electrochemical potential.Lithium metal is ideal anode for the next generation of lithium oxygen,lithium sulfur and other high energy density battery system.The uncontrolled growth behavior of lithium dendrites and the volume expansion during cycling process hinder the practical application of lithium metal anodes.The modification of “lithiophilic” metal oxide on metal current collector is a method to fundamentally inhibit the growth of lithium dendrites,which is more beneficial to practical application.Commercial copper foil collector requires higher surface energy for nucleation due to its “lithiophobic” nature,and the defects on its surface tend to induce the uneven Lithium deposition.The Ti-mesh shows goodelectrical conductivity,chemical inertness and high strength and toughness,which is a good metal current collector.Its' three-dimensional structure can alleviate the volume expansion of lithium metal anode.Brass mesh is also a promising current collector,which is low cost and good conductivity.However,their “lithiophobic” nature limit their practical application.In this paper,typical commercial Titanium?Ti?mesh and commercial Brass mesh were studied,and their surface modification and structure design were carried out for current collector of lithium metal anode.The main research contents of the thesis involve:?1?Self-assembling Cu O nanoflowers layer onto the Ti-mesh by microwave method,and use Cu O nanoflowers @ Ti-mesh for lithium metal anode current collector.Lithium?Li?metal anodes are promising candidates for high-energy-density batteries.However,uncontrollable dendritic plating behavior and infinite volume expansion are hindering their practical applications.Herein,a novel Cu O@Ti-mesh?CTM?is prepared by microwave-assisted reactions,followed by pressing on Li wafers,leading to Li/Cu O@Ti-mesh?LCTM?composite anodes.The lithiophilic Cu O nanoflowers on Ti-mesh provided evenly distributed nucleation sites,inducing uniform Li-ion lateral plating,which can effectively inhibit the growth of Li dendrites and volume expansion during cycling.The as-prepared LCTM composite anode exhibits high coulombic efficiency?CE?of 94.2% at 10 mA cm^-2 over 90 cycles.Meanwhile,the LCTM anode shows a low overpotential of 50 m V at 10 mA cm^-2 over 16000 cycles and a low overpotential of 90 m V and 250 m V even at ultrahigh current densities of 20 and 40 mA cm^-2.When paired with Li4Ti5O12?LTO?,it enhances the capacity retention of LTO/Li wafer full cells by about two times from 36.6% to 73.0% and 42.0% to 80.0% at 5 C and 10 C with long-term cycling.?2?The surface of brass mesh was oxidized by electrochemical oxidation in Na OH solution,and the oxidized layer @ brass mesh was used for lithium metal anode current collector.The Oxidation Brass Mesh?OBM?prepared by Electrochemical Oxidation method.Plating a certain amount of lithium metal onto OBM,leading to Li/Oxidation Brass Mesh?LOBM?composite anode.Brass mesh lithiophilic CuO and ZnO particles provided uniform distribution of nucleation sites,increasing the specific surface area,inducing the uniform Li deposition,which can effectively inhibit the growth of Li dendrites and alleviate the volume expansion during the process of cycling.LOBM maintained a high coulombic efficiency of 98.0% for over 700 cycles at a current density of 1 mA cm^-2.And the LOBM anode maintained an ultralow overpotential of 60 m V and 120 m V at the ultrahigh current density of 10 and 20 mA cm^-2.When the utilization of Li of anode is 50%,the capacity retention of the LOBM-LFP?LiFePO₄?full cell wasimproved at 2 C.