Preparation Of 3D Porous Material And Its Application In Lithium-Oxygen Batteries

With the increasingly prominent environmental and energy problems,the development of clean and renewable electrochemical energy storage technology has been widely concerned.Lithium-air batteries have been widely studied because of their high energy density and become one of the most promising electrochemical energy storage technologies.Yet,the development of Li-air batteries is still hindered by a multitude of problems related to the Li metal anode and the cathode,such as the unsteadiness of the carbon for cathodes,lithium dendrites.It is urgent to design air electrode and lithium metal electrode reasonably to solve these problems.The 3D porous material has the advantages of good electrical conductivity,large specific surface area,and high porosity.Based on these three-dimensional porous materials,the electrode structure is reasonably designed,and the following studies have been carried out.Cu nanoneedle arrays with nanoengineered Au coating are grown directly on Cu foam substrate（Au/Cu@FCu）through in-situ oxidation and reduction method,which is served as the cathode of Li-air batteries.The synthesized carbon-free Au/Cu@FCu exhibits excellent conductivity,high porous,abundant specific surface area,and high catalytic activity,which effectively enhances the electrochemical performance of Li-air batteries.The Au/Cu@FCu cathode demonstrates reversibly formation and decomposition of Li₂O₂,extremely low overpotentials（0.64 V）,ultra-high discharge specific capacity(27270 mAh g^-1),outstanding rate capability and long cycle life,and the good electrochemical stability which is effectively alleviated the problem of carbon cathode’s instability.In order to improve the electrochemical performance of Li-air batteries,we simultaneously solve these problems related to the Li metal anode and the cathode by introducing the concept of symmetrical lithium-oxygen batteries for the first time,which the cathode and anode of lithium air batteries have the same electrode structure.Au/Cu@FCu not only has good electrical conductivity,high porosity,large specific surface area,and high catalytic activity,but Au is the well affinity with lithium.Therefore the Au/Cu@FCu can act as both anode backbone and cathode in Li-air battery.We first study the electrochemical properties of the Li deposited Au/Cu@FCu anode.Benefiting from these structural advantages of Au/Cu@FCu and the lithiophilic nature of Au,the homogeneous plating Li is formed to effectively suppress the generation of dendrites.The Coulombic efficiency of the Li deposited Au/Cu@FCu anode is 96%at 1 mA cm^-2 with 1 mAh cm^-22 capacity.The Li deposited Au/Cu@FCu anode has more excellent cycling stability,which can run above 970 h.Then,based on the characteristics of the cathode discharge products of Li-air batteries,discharging and charging states of the Li deposited Au/Cu@FCu anode and Au/Cu@FCu cathode of the symmetrical Li-air batteries are discussed.Moreover,the symmetrical Li-air battery shows long-term stability.In the future,more efforts in designing and optimizing the material and structure are needed to satisfy the requirements for both anode and cathode,improve the electrochemical performance of Li-air batteries.Again,such electrode and cell construction can provide favorable promising applications in next-generation energy storage systems.