Preparation And Electrochemical Performance Of Three-Dimensional Nitrogen-Doped Porous Carbon-Based Composites

With non-renewable energy further consuming,developing renewable energy is imperative.Besides,our country's"dual carbon"strategic goal also emphasizes that developing renewable energy is indispensable and significant.Therefore,advanced renewable energy conversion and storage facilities are urgently needed to overcome the time and space deviation.Electrochemical energy storage devices have been one of the most promising energy storage methods,benefited from the efficient energy conversion,high energy density and power density.Among them,lithium-ion capacitors(LICs),as the hybrid energy storage system combining the advantages of lithium-ion batteries(LIBs)and supercapacitors(SCs),exhibit great potential.Porous carbon has been regarded as the most popular electrode material of LICs,owing to the merits of low cost,convenient preparation,abundant reserves and stability.Considering the limited capacity of porous carbon,a series of three-dimensional N-doped porous carbon(3DNC)/transition metal nanoparticles(TMOs NPs)electrode materials are prepared through combining salt template,gas-phase coating and in-situ pyrolysis.The characterizations of physical/chemical properties and electrochemical performance of the composite electrode materials are carried out.The relationship of electrochemical performance and physical/chemical properties is deeply analyzed.The main research contents are as follows:(1)The shape and size of Na Cl can be tuned by adjusting surfactant amount,recrystallization temperature,solution volume and solvent type.With high PVP content,low temperature,low concentration of Na⁺,Cl⁺and low solubility alcohol,cubic Na Cl with uniform size(?400 nm)is prepared.The same method can be used for obtaining other hydrosoluble salt templates(KCl,KBr and Ba Cl₂).(2)Combining salt template,gas-phase coating and in-situ pyrolysis,3DNC/Cu O composites(3DNC@Cu O-X)with controllable structure(carbon layer thickness,N doping concentration,graphitization degree and pore structure)are obtained.Specially,3DNC@Cu O-9h as anode of LICs achieves the high capacity of 817.1 m Ah g^-1,and the capacity at 10 A g^-1remains 100.2%of the initial capacity after 5000 cycles.The capacity of 3DNC@Cu O-9h cathode is 42.6 m Ah g^-1,and the capacity at 5A g^-1maintains 98%of the initial capacity after 5000 cycles.The LICs composed of3DNC@Cu O-9h exhibit a high energy density of 140.2 Wh kg^-1at 226 W kg^-1,and the capacity still maintains 99.2%of the initial capacity after 5000 cycles.(3)3DNC/Fe₂O₃ composites(3DNC@Fe₂O₃-700)have been prepared through substituting Cu Cl₂ by Fe Cl₃ with stronger activation ability.3DNC@Fe₂O₃-700 as anode of LICs can reach a high capacity of 946.6 m Ah g^-1,and the capacity at 20 A g^-1maintains 106.5%of the initial capacity after 5000 cycles.Furthermore,the capacity of3DNC@Fe₂O₃-700 cathode reaches 82.1 m Ah g^-1 and the capacity at 5 A g^-1 holds 100%of the initial capacity after 5000 cycles.The electrochemical kinetics and capacity mismatch between anode and cathode are relieved to a certain extent,3DNC@Fe₂O₃-700//3DNC@Fe₂O₃-700 LICs exhibit high energy density,high power density(206 Wh kg^-1 at 226 W kg^-1)and excellent cycling life(a capacity retention of 118.2%after 5000cycles).(4)Aqueous 3DNC@Fe₂O₃-700//3DNC@Fe₂O₃-700 SCs are constructed with exceptional performance of 10.45 Wh kg^-1 at 300 W kg^-1,and the capacity at 5 A g^-1maintains 93%of the initial capacity after 10000 cycles.