Preparation And Electrochemical Performance Of Biomass (mango Kernel, Oil Cake) Derived Hierarchical Porous Carbo

Today,energy storage and resource issues are two significant challenges facing the development of human society.The use of biomass waste to prepare porous activated carbon with high specific surface area,high microporosity ratio and excellent electrical conductivity is attracting a lot of attention from research scholars in energy conversion and storage.In this thesis,mango seeds and rapeseed meal（oil meal）biomass waste were used to prepare activated carbon by carbonization.Subsequently,nitrogen（N）,and oxygen（O）doped mango seed activated carbon（MSAC）and nitrogen（N）,oxygen（O）,phosphorus（P）and sulfur（S）co-doped rapeseed meal activated carbon（RMAC）were obtained in a simple high-temperature activation process.Details of the research are as follows.（1）The effect of different amounts of KOH activator on the microstructure and electrochemical performance of MSAC is carefully investigated.The results show that the specific surface area and microporosity of the MSAC materials obtained are higher when activated with higher amounts of KOH activator.But the content of elemental doping is reduced.The optimized MSAC-4 exhibits high specific surface area(1815 m²?g^-1),high microporosity（94%）,and high content of N（1.71 at.%）and O（10.93 at.%）doping.The MSAC-4 electrode achieves an ultra-high specific capacitance of 402 F?g^-1 at a current density of 1 A?g^-1.After 5000 cycles,the MSAC-4 electrode maintains a capacitance value of up to 102.4%compared to the initial capacitance value,showing excellent cycle life stability.Subsequently,the electrochemical performance of the supercapacitor assembled with MSAC electrode was investigated in detail in 6 M KOH,1 M[BMIM]BF₄/AN electrolyte and PVA/KOH solid electrolyte.Finally,the flexible all-solid-state asymmetric supercapacitor（FSAS）assembled with MSAC-4 anode,Ni Co Al layered double hydroxide（LDH）cathode,and PVA/KOH solid-state electrolyte was investigated.It obtains an energy density of 33.65 Wh?kg^-1 at a power density of 187.5 W?kg^-1 and maintains 80%of the initial capacitance after 10000 cycles.（2）The effect of different activation temperatures on the microstructure and electrochemical properties of RMAC is investigated.The specific surface area and microporosity of RMAC materials obtained at higher activation temperatures are larger,but the elemental doping content reduces.The optimized RMAC-800 shows a large specific surface area(3291 m²?g^-1)and multi-element doping of N,O,P and S.It achieves a very high specific capacitance of 416 F?g^-1 at 1 A?g^-1 and maintains 92%of the initial capacitance after 10000 cycles.The RMAC-800 electrode material exhibits very good electrode performance and high cycle life retention.The electrochemical performance of symmetrical supercapacitors assembled with RMAC-800 electrode materials was then investigated in 6 M KOH and 1 M[BMIM]BF₄/AN electrolytes.The device achieves a high energy density of 195.94 Wh?kg^-1 at a power density of1125 W?kg^-1 and maintains 75%of the initial capacitance value after 5000 cycles.Therefore,This thesis provides a low-cost and facile strategy to transform biomass wastes,such as mango core and oil meal,into porous carbon materials for energy conversion and storage systems.