Sodium/potassium Storage Properties Of Boron-nitrogen Co-doped Cellulose-derived Hierarchical Porous Carbons

Carbon materials have unique advantages such as adjustable microstructure and designable defects.Doping engineering is of great significance for adjusting the conductivity,structural defects and energy storage performance.Boron/Nitrogen doped hierarchical porous carbon(HPC)materials have been optimized via doping engineering for sodium ion and potassium ion storage.(1)The nitrogen-rich N@HPC and boron(B@N@HPC)modified HPC have been obtained taking cellulose as the carbon source and ammonia/boric acid as the nitrogen/boron doping source.The effect of boron doping is investigated to reveal the evolution of microstructures,porosity,surface area,and chemical groups.It is found that boron doping cannot further change the interlayer distance of nitrogen-rich HPC,but B@N@HPC exhibits excellent electrochemical performance as an anode in sodium ion batteries(SIBs).Compared with N@HPC,B@N@HPC anodes show a larger capacity of 308 m Ah g^-1 at0.02 A g^-1,which is 137%larger than that of nitrogen doped HPC.Electrochemical Kinetics analysis through galvanostatic intermittent titration technique(GITT)and electrochemical impedance spectroscopy(EIS)suggests a capacitive-dominated process combined with a higher Na⁺diffusion coefficient and lower charge transfer resistance for the B@N@HPC than that of N@HPC.The effect of boron doping on the carbon anodes can be taken to explore an enhanced performance for SIBs.(2)In this part,we found that the higher carbonization temperature at 1000?could induce a higher specific surface area up to 1310.4 m2 g^-1.Taking boric acid and ammonium pentaborate as the boron doping precursors,boron doping(B-HPC)and boron/nitrogen co-doping(B-N-HPC)were prepared.Comparative investigations showed that the nitrogen content of B-HPC was 4.71%,which is lower than that of B-N-HPC;while the boron content of B-HPC was 1.92%,which is higher than that of B-N-HPC(1.61%).The B-HPC negative electrode can deliver a capacity of 320 m Ah g^-1 at 0.01 A g^-1,while the B-N-HPC can only reach 200 m Ah g^-1.Moreover,B-HPC exhibit a better cycling stability that that of B-N-HPC.In addition,the capacity of B-HPC anode at 10 A g^-1 is 64 m Ah g^-1,which is also higher than that of B-N-HPC cathode at 42 m Ah g^-1.These results indicate that boron and nitrogen doping can adjust the structure of carbon materials and improve the electronic conductivity of carbon materials,making it easier to store potassium,which can be used to explore ways to improve the performance of potassium ion batteries(PIBs).