A High Performance Li-ion Capacitor Based On Porous Activated Carbon Cathode And N-doped Porous Carbon Anode

As the powerful candidate for the next generation of energy storage devices,lithium-ion capacitors have become the focus of current research.However,the mismatch between the slow kinetic of negative electrode and the fast ion desorption process of positive electrode and the contradiction between the high capacity of negative electrode and the low specific capacity of the negative electrode seriously hinder the development of lithium ion capacitor.Therefore,the synthesis of new electrode materials has become an urgent problem.In this paper,a series of work has been carried out on the preparation of high performance lithium ion capacitors,such as the preparation of carbon materials,the matching of positive and negative electrodes,and so on.The main contents are as follows:Preparation and electrochemical properties of porous activated carbon anode.Porous activated carbon was prepared by one-step high temperature carbonation activation method with asphalt powder as precursor and KOH as activating agent.Through the investigation of the amount of KOH and the temperature of secondary calcination,we found that the activation temperature of KOH:asphalt powder was 5:1at 800?for 1 h and the secondary calcination temperature is 1000?,the porous activated carbon has the best electrochemical performance.At 1.5-4.5 V and 0.5 A g^-1,the specific capacity is 263.8 m A h g^-1).At 5 A g^-1,the capacity retention rate is 68.11%and the rate performance is excellent.After 500 cycles,the capacity is 97%,which has good cycling stability.Preparation and electrochemical properties of nitrogen-doped porous carbon cathode.A nitrogen-doped porous carbon was synthesized by one-step carbonation template method with asphalt powder as carbon precursor,porous Mg O as template and melamine as nitrogen source.The nitrogen-doped porous carbon has a flake structure similar to that of porous Mg O template,rich mesoporous and high nitrogen content.The electrochemical tests show that the specific capacity of nitrogen-doped porous carbon is248.1 m A h g^-1 at 0.01-1.5 V and 1 A g^-1,and 177.3 m A h g^-1 at 5 A g^-1,respectively.The capacity retention rate is 81.4%.After 1200 cycles,the capacity retention rate is81.4%,and the cycling stability is good.Lithium ion capacitor performance test.lithium ion capacitors were constructed by porous activated carbon as anode and nitrogen-doped porous carbon as cathode.Lithium ion capacitors have good electrochemical performance by suitable matching of high performance positive and negative electrode materials.When the power density is 952.3W kg^-1 the energy density reaches the maximum,which is 176.2 Wh kg^-1.When the maximum power density is 9523.8 W kg^-1,the energy density remains very high,reaching 132.3 Wh kg^-1,After 2000 cycles,the capacity retention rate is 78.12%.In conclusion,a high performance lithium ion capacitor with porous activated carbon as anode and nitrogen doped porous carbon as cathode has been obtained by reasonable matching of electrodes and carbon material structure design.This kind of all-carbon material lithium-ion capacitor has the advantages of high energy density,and good cycling stability,which has important theoretical and practical value for the application of lithium-ion capacitor.