Controlled Growth Of Graphene/Graphdiyne Arrays And Performance As Substrates For Lithium Metal Deposition

With the rapid development of mobile phones,computers and new energy vehicles,the development of new generation of long-cycle,high-energy-density secondary batteries has become a research hotspot.Considering its higher theoretical specific capacity(3860 mAh g-1)and low reduction potential(-3.04V vs.SHE),lithium has become the most promising anode in the future.However,there are loads of problems with lithium mental anodes,such as generation of lithium dendrites,side reactions between lithium mental and the electrolyte,and volume expansion during cycling.Based on this background,this thesis mainly constructs vertical graphene on copper foam(Cu@VG)and nitrogen-doped graphdiyne on copper foam(Cu@N-GDY)as composite electrode to solve these problems.The main contents are as follows:(1)A vertical graphene nano walls was constructed on the surface of copper foam by plasma enhanced chemical vapor deposition(PECVD)to obtain a composite electrode.Due to good electrical conductivity and large specific surface of vertical graphene,the composite electrode provides more abundant room for lithium deposition which could reduce local current density and effectively inhibit the growth of lithium dendrites.The synergy of these advantages improves the electrochemical performance of the battery.Compared with copper foam(Cu)and copper foam/graphene(Cu@G)electrodes,Cu@VG electrodes exhibit lower nucleation over potential(26.6mV),Cu@VG composite electrode can stably cycle 1875 times with a current density and area capacity of 5mA cm-2,1mAh cm-2,improvement of cycle time and rate performance are witnessed in a full battery assembled with commercial NCM.(2)Graphdiyne is polymerized on the surface of copper foam by hydrothermal synthesis,and then nitrogen is doped through thermal reduction to finally obtain high-quality copper foam/nitrogen-doped graphdiyne(Cu@N-GDY)composite electrode.Owning to unique topological structure and electronic structure of graphdiyne,high charge mobility,excellent electron transport ability and the excellent lithiophilic performance of nitrogen element.The electrode could promote the uniform deposition of lithium metal and alleviate the volume expansion of lithium negative electrode.Compared with the copper foam(Cu)and copper foam/graphdiyne(Cu@GDY)electrodes,the Cu@N-GDY electrode presents a lower nucleation over potential(13.3 mV),Cu@N-GDY composite electrode can stably cycle for 175 cycles with a current density and area capacity of 3mA cm-2 and 3mAh cm-2,enhancement of cycle stability and rate performance are saw in a full battery assembled with commercial NCM.The research work provides a reference to the direction of metal protection.