Controllable Preparation Of Agaric Derived Carbon-Based Materials And Its Application In Electrochemical Energy Storage

Carbon material has the advantages of diverse structure,rich surface,strong regulation,and excellent chemical stability and so on,and has been an ideal candidate for electrochemical energy storage materials,such as commercial lithium ion battery anode material graphite,the electrode material of supercapacitor activated carbon.With the rapid development of micro-nano carbon and its composites,its unique structure and excellent electrochemical performance provide new opportunities for its application in the field of electrochemical energy storage,especially in high-energy batteries.Biomass is an ideal material for the preparation of carbon materials due to its abundant reserves and sustainable regeneration.However,due to the insolubility and complex composition of biomass,it is still a challenge to control the morphology of biomass carbon and to prepare ideal composite materials.Therefore,in this paper,we make full use of the characteristics of biomass itself,and realize the diversification of biomass carbon morphology and structure and the preparation of its composite materials through biomass mineralization strategy and yeast culture,and systematically explore its application in electrochemical energy storage.The specific research contents are as follows:1.Taking natural agaric as carbon source,the agaric-based solution was obtained by low temperature hydrothermal treatment,and the secondary high Temperature hydrothermal treatment was carried out with potassium permanganate to realize a biomass-mineralization strategy.MnCO3/C composites with various morphologies were prepared by changing the proportion of the reaction system in the reaction kettle.In addition,MnO/C composites with porous structure can be obtained by calcining cocoon-like MnCO3/C composites as precursor at high temperature.The uniform composition of biomass carbon provides an efficient conductive framework for MnO.The porous structure facilitates electrolyte transport and provides more active sites.As lithium-ion battery anode presents excellent rate performance.The capacity reaches 981 mAh g-1 at a current density of 0.1 A g-1,and the capacity remains at 440 mAh g-1 when the current density reaches 5 A g-1.2.The construction of the core-shell structure is an important way to improve the cycle stability of the metal oxide as the negative electrode of the lithium-ion battery.However,it is still difficult to achieve the core-shell structure of metal oxide@biomass carbon using natural biomass as the carbon source.Combined with the preparation method of cubic manganese carbonate in the work of the previous chapter,the core-shell structured MnO@C composite material was prepared by calcination.The stable carbon shell provides a continuous conductive channel,which can be used as an effective protective layer of MnO,alleviating the volume expansion effect during charge-discharge process and slowing the corrosion of the active material by the electrolyte.In the electrochemical performance test,at a current density of 0.1 A g-1,the mass specific capacity reached 1147 mAh g-1,the volume specific capacity reached 1628.7 mAh cm-3 and present excellent cycle stability.3.Using natural agaric and KMnO4 as raw materials,adjusting their ratio,the precursor MnCO3/C composite was prepared by simple mineralization-strategy again.The cubic porous MnO2 and biomass carbon frameworks were prepared by different processes,and were used as positive and negative electrode materials to assemble asymmetrical supercapacitors,respectively,and showed excellent electrochemical properties,with High Energy Density(46.1 Wh kg-1)and excellent cycle performance.In this work,the "One Stone Two Birds" synthesis strategy can produce both positive and negative electrode materials,which can simplify the preparation process and reduce the synthesis cost.4.In order to solve the problem of easy spoilage of biomass,the original agaric and agaric-base solution were used as solid and liquid media respectively for yeast culture to realize the comprehensive utilization of waste.The effect of yeast fermentation on the original structure and composition of biomass was studied by solid-state culture.The original low porosity massive structure of agaric was modified and the heterogenous elements(N,P)were added.The results showed that the original agaric formed a porous fibrous structure after fermentation by yeast,which increased the specific-surface-area of biomass carbon and was beneficial to further activation.Liquid culture is propitious to the mass reproduction and regeneration of yeast in agaric-based solution.Three-dimensional spore aerogels were obtained by freeze-drying,and the porous spore carbon aerogels were prepared by further carbonization and activation.The-prepared carbon material as supercapacitor electrode show excellent electrochemical performance in different electrolyte systems.The specific capacity of the device under aqueous solution can reach 80F g-1,and the energy density of the ACN organic system reached 88.17 Wh kg-1.