Preparation Of Asphalt-Based Carbon Materials And Their Application In Lithium-Ion Hybrid Capacitors

Exhaustion of fossil fuels and environmental pollution drive us to develop new energy such as solar energy,wind energy,water energy,and advanced energy storage systems.Electrochemical energy storage devices（EESDs）like lithium-ion batteries（LIBs）and supercapacitors（SCs）are widely used in our daily life.With the high-speed development of new energy technologies,the demand for both high energy density and high power density EESDs is intense in the future,indicating neither LIBs nor SCs can entirely satisfy.Lithium-ion capacitor（LIC）composed of a battery-type anode and a capacitive-type cathode can deliver high energy density and power density,which got a lot of attention in recent years.However,the reaction kinetics and capacity mismatch between anode and cathode make it difficult to reach ideal results.To solve these issues,high-performance positive and negative electrode materials were prepared from petroleum asphalt in this paper.The LIC constructed by the optimum anode and cathode shows great performances.The main conclusions are as follows.（1）Hierarchical porous carbon（HPC-X,X is refer to different asphalt）materials were prepared through carbonization of different-constituent asphalt and CaCO₃ template.Mesopores and macropores originated from the removal of the CaCO₃ template,while the micropores were produced by the activation of CO₂ from the decomposition of CaCO₃.With the increase of the content of resins and asphaltenes in asphalt,the higher carbon yield and graphitization degree were obtained.Besides,the pore volume over 30 nm is proportional to the content of asphaltenes.Among all the materials,HPC-J with the highest specific surface area and pore volume exhibits optimum electrochemical performances.It can deliver a high reversible capacity of 772 mAh g^-1 at a current density of 0.1 A g^-1 during the initial cycle and a capacity of 410 mAh g^-1 after 1000 cycles at 2 A g^-1.（2）Hierarchical porous activated carbon（ZKAC-T,T is refer to the carbonization temperature）were synthesized by carbonization of asphalt,KOH,and ZnO template.In the existence of KOH,ZnO can participate in the activation process and convert to Zn subsequently evaporating in the high temperature.Increase in carbonization temperature can enhance the activation effect.However,the specific surface area increases first then decreases,which can be explained by the collapse of partial pores at high temperature.ZKAC-850 carbonized at850°C has the best electrochemical performances,presenting a capacity of 85 mAh g^-1 at 2 A g^-1 and no capacity decay after 5000 cycles.（3）LIC was assembled with a pre-lithiated HPC-J anode and a ZKAC-850 cathode,working in a suitable voltage window of 0.5-4 V chosen from the three-electrode test.Different mass ratios of the cathode to anode were studied based on the window.The results show that the initial capacity of LIC raises follow by the increased mass ratio,but an opposite result for cycling stability.When the mass ratio is 3:1,the LIC delivers excellent cycling stability and compromise capacity,emerging energy density retention of 73%after 4000 cycles.Moreover,HPC-J//ZKAC-850 LIC can offer energy density of 113 Wh kg^-1@223 W kg^-1 and 85 Wh kg^-1@25 k W kg^-1 respectively.