| With the progress of science and technology,supercapacitor has become an important energy conversion and storage device,it has excellent charge-discharge capacity,reliable cycle life,and greater power density,due to these characteristics it is widely used,and one of the most important factors affecting performance is the electrode material.At present,porous activated carbon is the most widely used electrode material,but its preparation of it relies on non-renewable fossil energy,which is unfavourable to environmental protection and sustainable development.It is an effective solution to change the preparation source into green and renewable biomass in nature,in which the plant Kochia with its natural pore structure and rich lignocellulose can be used as a natural carbon source for the preparation of porous carbon.This paper studied the preparation of porous carbon from biomass Kochia,improved the problem of the low energy density of symmetrical supercapacitor caused by the low specific capacitance of carbon electrode,used porous carbon material as a conductive substrate to prepare bimetallic sulfide/porous carbon electrode materiality to improve energy density,further improvements were made to address the inherent disadvantages of pseudocapacitive materials,including poor multiplicative performance and poor cycling stability,then the doped bimetallic sulphide/porous carbon electrode material was developed.First of all,Kochia as a carbon source,using its natural pore size structure and lignin-rich characteristics,using the carbonization and chemical activation method combined to obtain a large specific surface area,pore size structure excellent porous biomass carbon（KAC-5）,explore the optimal carbonization conditions and activation conditions,the final preparation of KAC-5 has abundant microporous structure and bring a high specific surface area of 1441.30 m2·g-1.The specific capacitance of 288 F·g-1(0.5 A·g-1)was obtained by the electrochemical test of the three-electrode system,symmetrical supercapacitor KAC-5||KAC-5 assembled using KAC-5 as positive and negative electrodes with energy density to 12.3 Wh·kg-1Secondly,to solve the problem of low energy density,KAC-5 is used as a conductive substrate to support nickel-cobalt bimetallic sulfide（NCS）with better performance.On the one hand,KAC-5 with a large specific surface area and hierarchical porosity provides a good growth site for NCS,which improves the accumulation and aggregation phenomenon in the growth process of the original NCS to a large extent,so that the active material can expose more active sites for electrochemical reaction.On the other hand,the strong electronic coupling between bimetallic sulfide and porous carbon changes the electronic state of the original material and increases the electrical conductivity,so that the redox reaction can be carried out more quickly and efficiently.The optimal amount of KAC-5 was discussed and the influence mechanism was analyzed.The specific capacitance of NCS at 1 A·g-1 was increased from 1253 F·g-1 to 1426 F·g-1 of NCS-15,and the multiplier performance and cycle stability were also optimized.NCS-15||KAC-5by NCS-15 of the positive and KAC-5 for a negative,under the power density of 775W·kg-1 can provide the energy density of 44.7 Wh·kg-1 after 5000 cycle test capacitance keep the rate of 82.8%.Finally,to solve the inherent shortcomings of NCS,such as poor multiplier performance and poor cyclic stability,Cu doping was carried out,5 mol%was studied as the optimal doping amount,and 5 Cu-NCs electrode was prepared.The geometric form and electronic state of the original NCS were changed,which improved the multiplier performance and cyclic stability.When 5 Cu-NCS and KAC-5 are combined,the introduction of KAC-5 also changes the geometry and electronic state of 5 Cu-NCS and weakens the accumulation and aggregation phenomenon,which will bring higher electrical conductivity and more active sites for electrochemical reaction,further improving the electrochemical performance.At the same time,the optimal amount of KAC-5 and the improvement of 5 Cu-NCS were also studied.Finally,Cu-NCS-10 with excellent electrochemical performance was prepared,and the specific capacitance of 5Cu-NCS was increased from 1440 F·g-1 to 1507 F·g-1 of Cu-NCS-10,and the rate performance and cycle stability of the composite were also improved.Assembled as an asymmetric supercapacitor Cu-NCS-10||KAC-5 achieves a maximum energy density of46.3 Wh·kg-1 at a power density of 775 W·kg-1. |
