Preparation Of Sea Urchin Cu/Cu₃N Nanomaterial And Its Application In Three-Dimensional Current Collectors Of Lithium Metal Anode

With the development of information age,the application of sustainable green new energy such as solar energy has put forward new requirements for energy storage system.Secondary batteries,especially lithium-ion batteries,are widely used because of their high energy density and long cycle life.Among many electrode materials,lithium metal has been widely concerned due to its high theoretical capacity,low reduction potential and lowest density,and is expected to become the anode material of a new generation of high energy density lithium ion batteries such as Li-S and Li-O₂batteries.However,the commercial application of lithium metal anode still faces some problems,including the growth of lithium dendrite caused by uneven nucleation and the drastic change of the relative volume of lithium during deposition and dissolution.To solve these problems,this thesis developed a highly efficient 3D substrate composed of sea urchin shaped Cu based nanoparticles to fabricate efficient lithium metal anode with good cycling performance.The large specific surface area and large amount of nucleation sites provided by the spinous structure and lithiophilic surface improve the ability of the 3D frame to suppress dendrite formation,even under high lithium capaicity and large current density.The specific research content is as follows:（1）The sea urchin-shaped spinous copper/copper oxide（Cu/Cu O）nanoparticles were prepared by surface oxidation of copper spheres,and used to prepare three-dimensional deposition skeleton in lithium metal anode.The spiky morphology made the three-dimensional skeleton have more pores and larger specific surface area,which can accommodate more lithium while alleviating the volume change during cycling,and thus enhance the electrochemical performance of the composite lithium anodes.The liophilic Cu O on the surface provided numerous nucleation sites and guided uniform deposition of lithium metal.The 3D skeleton can deposit lithium up to a capacity of 10m Ah cm^-2without lithium dendrites.The symmetric battery cycled steadily for more than 400 h at10 m A cm^-2and 10 m Ah cm^-2,and the capacity retention was 69%after 250 cycles at 1 C.Moreover,investigation was carried out on the influence of particle morphology and electrical conductivity on performance of the composite electrode through series of experiments,in order to further improve the performance of the composite electrode by the spinous copper nanoparticles.（2）The sea urchin-shaped Cu/Cu O nanoparticles were nitrided on the surface to synthesize sea urchin-shaped Cu/Cu₃N nanoparticles and construct an efficient lithium deposition framework and prepare ultra-thin lithium metal anode current collectors.The surface nitridition can improve the electronic conductivity while still maintain the high lithium-affinity,which makes the conduction resistance of electron and ions in the 3D skeleton become lower.The Cu₃N can promote the formation of SEI films rich in Li₃N,and enhance the reversibility of lithium metal deposition/dissolution process.The symmetric cell cycled steadily for more than 1000 h at 1 m A cm^-2,and the polarization voltage is only 32 m V.Under high current density of 10 m Ah cm^-2,the cycling can be sustained for more than 840 h.The capacity retention of the full battery reached84.3%after 250 cycles at 1 C.The composite lithium anodes can cycled for 1350 h with a low polarization voltage of 34 m V and exihibited good rate performance when the thickness of the 3D sketelon was 25μm.The full battery can cycle for more than 300 cycles with a high Coulombic efficiency of 99.9%.When a 15μm thick skeleton was fabricated and used,the corresponding lithium metal composite electrode offered acceptable lithium deposition effect and electrochemical performance.In conclusion,we believe that the sea urchin-shaped Cu/Cu O and Cu/Cu₃N nanomaterials can induce uniform deposition of lithium metal when applied to build 3D deposition skeleton in lithium metal anode,which can significantly improve the cycling stability and lithium capacity of the battery.Moreover,we found that Cu/Cu₃N nanomaterials have great potential in the construction of ultra-thin lithium anode.