Preparation Of Lithium Metal/Honeycomb Carbon Skeleton Composite Electrodes And Its Inhibition Of Lithium Dendrite Growth

Following the innovation of technology and the advance of society,people's livelihoods have also moved to a moderate level across the board,but the consumption of non-renewable energy is also increasing,so more and more researchers are working on new energy storage devices with"light mass,high specific capacity and good safety".Lithium(Li)metal is a prospective anode for lithium-ion batteries,meeting the requirements of"light weight"and"high capacity".However,there are significant safety risks,as the lithium metal anode is prone to lithium dendrites,which can puncture the diaphragm and cause short circuits,leading to explosions and other hazards.In order to inhibit lithium dendrites growth,this thesis synthesizes three-dimensional honeycomb carbon skeletons,oxy-boron co-doped honeycomb carbon skeletons and oxy-boron co-doped honeycomb carbon skeletons covered with zinc oxide composites in a series of simple ways for the current collector of lithium metal,and investigates the effect of fluid collection on the deposition pattern of lithium metal and have carried out relevant electrochemical tests.This thesis focuses on the following research:(1)Polystyrene spheres of different diameters were synthesised by emulsion polymerisation,which were then used as templates and phenolic resins as precursors to prepare HcCs with amorphous structures of honeycomb carbon skeletons,and the HcCs were characterised by a series of characterisation tools(SEM,TEM,XRD,BET and Raman,etc.).The growth pattern of lithium metal on HcCs and the effect of different pore sizes of HcCs on lithium metal deposition were explored.The results show that:lithium metal grows spherically on HcCs,which contributes to uniform lithium metal deposition;HcCs-100 with the smallest pore size have better lithium affinity.At 1 mA/cm~2 with lithium deposition capacities of 1mAh/cm~2,Cu@HcC-100 collectors maintain a Coulomb efficiency above 88%in 108 cycles,and the symmetric cell is stable for 280 h.The initial capacity of HcCs-100@Li full cell is150.2 mAh/g,maintaining a capacity of 93.7 mAh/g and a Coulomb efficiency of 99.3%in500 cycles at a 0.5 C rate.Therefore,HcCs with large specific surface area and curved ion channels can regulate the morphology of lithium deposition and have a role in inhibiting lithium dendrite growth.(2)Oxygen-boron co-doped honeycomb carbon skeletons OBHcCs were prepared on the basis of HcCs-100 using an oxygen-boron containing phenolic resin as a precursor,and the OBHcCs were characterized by a series of characterization tools.The effect of oxygen-boron co-doping on lithium metal growth and on lithium metal deposition was explored,while the mechanism of inhibition of lithium dendrite growth by oxygen-boron co-doping was also investigated by XPS depth profiling and density flooding theory calculations.The findings indicate that:the oxygen-boron co-doping does not change the spherical growth pattern of lithium metal and achieves better dendrite free lithium metal deposition than HcCs;the OBHcCs-1 with the least amount of oxygen-boron doping has better pro-lithium properties.At 1 mA/cm~2 with lithium deposition capacities of 1 mAh/cm~2,the Cu@OBHcC-1 collector maintains a Coulomb efficiency above 97.2%in 150 cycles,and the symmetric cells can be stably cycled for 700 h.The initial capacity of OBHcCs-1@Li full cell is 148.0 mAh/g,maintaining a capacity of 125.2 mAh/g and a Coulomb efficiency of 99.6%for 500 cycles at a 0.5 C rate.The oxygen-boron co-doping facilitates the formation of SEI films with more inorganic content,which helps the diffusion of lithium ions;the oxygen-boron functional group has greater adsorption energy for lithium atoms.The oxygen-boron functional group has a higher adsorption energy for lithium atoms,and the lithium atoms tend to nucleate and grow at the oxygen-boron doping sites.Therefore,the oxygen-boron co-doping provides more nucleation sites,which is conducive to improving the lithiophilicity of the carbon skeleton and inhibiting lithium dendrites growth,but too high an amount of oxygen-boron doping is likely to lead to oxide precipitation,resulting in lower electrical conductivity of the material,which is not conducive to inhibiting lithium dendrites.(3)The OBHcCs@ZnO were coated with ZnO nanoparticles on top of OBHcCs-1 by direct precipitation and characterised by a series of characterisation tools.The effect of ZnO cladding on the growth pattern and on the deposition of lithium metal was explored.The results show that the ZnO cladding does not change the spherical growth pattern of the lithium metal and achieves uniform lithium metal deposition with high capacity.At 1 mA/cm~2 with lithium deposition capacities of 1 mAh/cm~2,the Cu@OBHcC@ZnO-2 collector maintains a Coulomb efficiency above 97.6%in 486 cycles,and the symmetric cells can be cycled stably for 420 h.Thus,the ZnO coating can further improve the lithiophilicity of OBHcCs,but the inhibition of lithium dendrites at high lithium loading capacity is not satisfactory,and even weakens the inhibition of lithium dendrites by the original oxygen-boron co-doped carbon skeleton.