Synthesis And Characterization Of Porous Carbon Anode Materials For Potassium Ion Batteries

Potassium-ion batteries are most likely to be a substitute for lithium-ion batteries and used in large-scale energy storage,resulting from the richness and low cost of potassium resources.However,the potassium-ion radius is large and the diffusion kinetics are slow,making it difficult for the existing anode material to stably store potassium.Carbonaceous materials become one of the anode electrode materials for potassium ion batteries due to large interlayer distance,high specific surface area and electronic conductivity.However,the problems of low rate,poor cycle stability and low capacity problems caused by the instability of the carbon material structure need to be urgently resolved.In this paper,porous carbon materials and nitrogen-doped carbon cages were prepared by low temperature hydrothermal reaction and high temperature carbonization process using sycamore leaves as raw material.The specific research contents are as follows:1 The products after hydrothermal heating were used as precursors at 800,850 and900? for carbonization 3 h(heating rate is 2?·min^-1),respectively.The electrochemical behavior of the products at different reaction temperatures was researched and the optimal carbonization temperature was determined.Based on the optimal carbonization temperature,nitrogen doping was performed.The results show that after the nitrogen doping,more structural defects were introduced,additional reactive sites were provided,the specific surface area(286.6 m²·g^-1)and the interlayer distance?0.368 nm?were increased.As an anode electrode material for potassium-ion batteries,the high reversible capacity of 189.6 mAh·g^-11 can be achieved over 1800 cycles at a current density of 2000mA·g^-1,showing excellent stability and high capacity.2 The hydrothermal product was used as the precursor and reacted at a constant carbonization temperature of 850? for 0.5,1.5,3 and 6 h(heating rate is 10?·min^-1).The morphology and electrochemical behavior of the products at different reaction times were studied.The results show that the product with carbonization for 3 h has the best morphological structure and excellent reversible capacity.With the extension of sintering time,the specific surface area increases first and then decreases.When the sintering time was 3h,the specific surface area reached 300.3 m²·g^-1.As an anode electrode material for potassium-ion batteries,it can stably maintain the discharge specific capacity of 177.6mAh·g^-11 after 2000 cycles at a high current density of 2000 mA·g^-1,showing ultra-long cycle life.