Construction Of Metal Oxide-carbon Matrix Composites And Metal Carbides By Super-assembly Strategy For Lithium Metal Anode

Lithium metal as a battery cathode has a high theoretical capacity of 3860 m Ah g^-1,a low redox potential of-3.04 V and a low density of 0.59 g cm^-3,which is regarded as the"Holy grail"of lithium batteries and an ideal anode material.However,obstacles limit its commercial application,such as lithium dendrite growth and volume expansion during cycling,which results in low efficiency,low stability and safety hazards.In this thesis,three carbon-based frameworks are designed to solve the problems of lithium metal anode.The mainly research are as follows:（1）Uniform Li deposition assisted by dual carbon-confined Co O-Ni O nanoparticles for dendrite-free Li metal anode.We prepare a carbon polyhedral matrix（CPM）and reduced graphene oxide（r GO）composite of Co O-Ni O nanoparticles（（Co O-Ni O@CPM）@r GO）by hydrothermal-freeze-drying strategy.The Co O-Ni O@CPM particles uniformly distributing on the surface of r GO flakes can serve as nucleation sites for the homogeneous deposition of lithium metal.The bimetallic oxides-based nanoparticles can effectively enhance the lithiophilicity.The CPM and r GO flakes can provide a double-confined nano-space to alleviate the volume expansion during the lithium deposition.The results show that the Coulombic efficiency has remained to 98.7%after 300 cycles.The symmetric cells keep stability for more than 800 h at the current density of 1 m A cm^-2 and the deposited capacity of 1 m Ah cm^-2.The full cells assembled with Li Fe PO₄,show the capacity retention rate of 92.6%after 300 cycles at 1 C.The lithiophilic metal oxides and structural advantages significantly improve the electrochemical performance,which favours for its practical application.（2）Preparation of Zn O composites supported on ordered mesoporous carbon as lithium metal anodes.We use a chelation-assisted co-assembly method to synthesize high-quality ordered mesoporous carbon-supported Zn O nanoparticles.The Zn O nanoparticles uniformly distributing on the surface of mesoporous carbon materials can serve as nucleation sites,which can effectively improve the lithiophilicity of the matrix.The results show that the composites can maintain Coulombic efficiency of 98.5%after400 cycles.The symmetric cell can stable for 1000 h at a current density of 1 m A cm^-2with a deposited capacity of 1 m Ah cm^-2,and the full cell has a capacity retention rate of92.6%at 1 C for 700 cycles.Due to the porous structure and the existence of metal oxides,the growth of lithium dendrites and volume expansion during lithium deposition can be effectively suppressed.（3）Hierarchical porous h-Ti₃C₂ composites prepared by dealloying method and its application in lithium metal anode.We prepare hierarchical porous h-Ti₃C₂ matrix by dealloying method.h-Ti₃C₂ has lithiophilic property,which play an important role in homogeneous nucleation of lithium.It effectively regulates the nucleation of lithium metal and inhibits the growth of lithium dendrites.The results show that the composite has a Coulombic efficiency of 98.3%after 400 cycles.The symmetric cell is stable for1000 h at a current density of 1 m A cm^-2 deposited at a capacity of 1 m Ah cm^-2,and the full cell exhibits a capacity retention of 97.8%at 1 C for 700 cycles.h-Ti₃C₂ has a significantly improved electrochemical performance.This work provides a basis for the development of lithium metal battery anodes for high energy and high power battery systems.