Preparation And Application Of Lithium/Carbon Composites For Lithium Metal Batteries

Compared to conventional lithium ion batteries(LIBs),anodes of lithium metal batteries(LMBs)have higher theoretical capacity(3860 mAh g-1)and lower electrochemical potential(-3.04 V).Therefore,many experimenters and researchers are paying more and more attention to the research of lithium metal anodes(LMAs).However,the problem when using lithium metal as the anode is obvious.For example,short circuit or even explosion would happen to the LMB if the lithium dendrites develop ceaselessly.Moreover,the current density and power density of the LMBs are greatly limited due to the unstable solid electrolyte interfaces(SEIs)on the surface of anodes,so it is difficult to develop the actual application of LMBs in daily life.Thus,exploring a kind of lithium metal anode which is stable and could operate at large current density is a important subject.In this thesis,lithium/carbon(Li/C)composite electrodes were prepared by cold rolling.The composite electrode sheets with different carbon contents were obtained by superposition of Li sheets and control of rolling thickness.The method of cold rolling is simple in operation,easy to achieve the mass production,and more importantly,it can be used for different types of porous materials.Powdered carbon materials such as:reduced graphene oxide(rGO),activated microwave exfoliated graphite oxide(aMEGO)and activated carbon(AC);non-powdered carbon materials such as carbon cloth(CC),carbonized sponge;non-carbon materials such as:sponge,stainless steel fiber felt(SSFF),have been used.The surface morphology and composition of samples were characterized by SEM and XRD;the electrochemical performance was characterized by constant current charge and discharge test.For the measurements,Lithium metal/carbon(Li/C)composite electrode sheets prepared by cold rolling were assembled into symmetrical batteries in a glove box,and then tested at a high current density(10 mA cm-2)and large capacity(10 mAh cm-2).The symmetrical battery made of 460 in Li/rGO was able to cycle for more than 119 cycles with an overpotential of 225 mV,while that made of 340 ?m Li/rGO was cyclable for more than 425 cycles with an overpotential of 150 mV,both better than the symmetrical batteries from bare Li metal with the same thicknesses.Moreover,the Li/rGO electrodes with thicknesses of 460 ?m and 340 ?m have the Li utilization rate of 21.3%and 31.6%,respectively,at a charge and discharge capacity of 10 mAh cm-2,which is higher than bare Li metals of the same thicknesses(10.5%and 14.3%).The Li and rGO composite anodes not only have stable three-dimensional composite structures and high Li utilization rates,but also can efficiently prevent the the growth of lithium dendrite at high current density and large capacity.These characteristics make Li/C composites prepared by cold rolling a valuable application prospect in the future.