Construction Of Novel Porous Copper Current Collector And Study On Stabilization Of Lithium Metal Anode

The high-energy-density batteries that play a key role in the applications like electric vehicles,portable electronic device,smart grid,etc.The construction and development of the batteries with high energy densities is a promising strategy for ensuring energy security,implementing“Energy Conservation and Pollution Emissions Reduction”policies as well as promoting green and low-carbon circular social development system,which is an inevitable course for sustainable energy revolution.Due to their unique features,such as low cost,long cycling,reversible redox properties,and low pollution,lithium ion batteries（LIBs）dominate the market for secondary battery.The energy densities of LIBs,however,need to be substantially enhanced to meet the increasing demand of the rapidly developed consumer electronics,especially the requirement for extending the range of electric vehicles.To date,the most commercial potential LIB systems using lithium cobalt oxides or lithium nickel cobalt manganese oxides as cathodes and graphite anode have already approached the theoretical limitation(usually<300 Wh kg^-1)but still can not fulfill the requirements.Thus,it is necessary to development novel energy storage systems to break the bottlenecks of LIBs.lithium-metal batteries（LMBs）could reach the ultra-high energy densities owing to the high theoretical specific capacity(3860 mAh g^-1),low potential（-0.304 V vs.SHE）and low density(0.534 g cm^-3)of the lithium metal anode.However,several key issues should be addressed towards practicality of LMBs.First,the growth of Li dendrites leads to declining performance and seriously affects the safety of batteries.Second,unstable solid electrolyte interphase（SEI）formation exacerbates electrolyte consumption and shortens the battery cycle life.Third,the internal stress and volume expansion during charge and discharge cannot be effectively controlled,which may seriously destroy the stability of the anode.Therefore,the key point to make the LMBs practical utilization is to develop effective methods to stabilize the Li anode,for example,using three-dimensional（3D）porous copper current collector to replace commercial copper foil,in which the diffusion and nucleation of Li ions could be controlled with the high specific surface area and through-pore structure of 3D skeleton,and thus the growth of Li dendrites suppressed.The currently used fabrications for 3D Cu current collectors are unable to meet the needs of large-scale production,and the low pore volume limits Li loading.In addition,the high mass ratios of the inactive Cu in the electrodes also hinder the enhanced energy densities of LMBs.Thus,the exploration of facile preparation process and the development novel 3D porous Cu current collectors are of great significance.This thesis focuses on the construction the innovative structural design of the stabilized Li metal electrode materials by constructing several Cu-based current collectors have been proposed.Based on the structural design of 3D Cu current collector and the stability mechanism of Li metal composite anode,the practicability of integrated bidirectional porous Cu（IBP-Cu）current collector and ultra-light Cu hollow microsphere（Cu HMS）current collector were studied.The main research contents and conclusions are as follows:1.An IBP-Cu current collector with high pore volume was prepared by powder sintering method.The as-prepared IBP-Cu current collector with high porosity which can accommodate Li up to 16.42 mAh g^-1.Under the charge discharge conditions of 1 mA cm^-2 and 1 mAh cm^-2,the IBP-Cu current collector show high stable cycling performance and maintain an excellent coulomb efficiency of 99.3%for 1000 cycles.Due to the continuous pore structure and high specific surface area,the IBP-Cu exhibits excellent deep charge discharge performance,excellent rate performance and ultra-stable cycle performance.In addition,the symmetrical battery composed of Li/IBP-Cu composite anode also has excellent cycling performance.This kind of integrated bi-directional electrode greatly improves the assembly efficiency and working efficiency of the soft pack battery,and has a broad prospect in the practical application of high-performance lithium metal batteries.The full cell assembled with LiFePO₄ cathode or sulfur cathode also shows high capacity retention,long cycling life and excellent flexibility,which can be used to prepare integrated LMBs with high-energy-density.2.Porous Cu hollow microspheres are prepared by the method of“surface reduction-internal etching”in this project.Then,a porous Cu HMS current collector with high conductivity is developed to construct high porosity current collector,high loading Li metal anode and high-energy-density Li metal battery.Compared with solid Cu current collector,the quality of Cu HMS current collector is reduced by 58.14%.The internal residual zinc can effectively induce the uniform deposition of Li in the porous skeleton.Under the condition of 10 mA cm^-2,the current collector exihits high stability in half-cell for more than 800 h.The Li/Cu HMS-LiFePO₄ battery exhibits excellent rate performance and high discharge capacity(132 mAh g^-1).This Cu HMS current collector with lightweight,high stability,high Li capacity and non-dendrite growth provides experimental support and theoretical basis for the development of practical Li metal batteries.