Design And Preparation Of Biomass Carbon-Based Materials And Their Application In Alkali-Ion Batteries

Recently,the global energy crisis and environmental pollution have prompted people to accelerate the pace of research and exploration novel clean energy and energy storage systems.Among them,alkali-ion batteries have received extensive attention from researchers because of their multiple advantages including high energy density,long-term cycling lifetime as well as memorylessness.However,as a key component of the battery,the anode material is suffering from the limitation of low theoretical capacity,which cannot meet the market’s demand for high energy/power density.Natural biomass has become an ideal precursor for the preparation of high-performance electrode materials due to its own advantages such as wide sources,environmental friendly and rich heteroatom elements doping.Unfortunately,it is difficult to design and control of the multi-level structure of biomass carbon-based materials by their multi-component and insoluble characteristics,thereby hindering its development in electrochemical energy storage applications.Herein,the special morphology and multi-level structure of biomass carbon-based materials were carefully customized and prepared using agaric and tremella subjected to hydrothermal treatment,acid-assisted etching and molten salt strategy,and the"structure-performance"relationship between the multi-level structure and the electrochemical performance of the material were explored in detail.The specific research content is as follows:1.Inspired by the internal core-shell structured olive,the olive-like core-shell structured MnO@C composite was prepared by a simple biomass-assisted strategy,when used as the LIBs anodes.Studies have shown that core-shell structure origin from the combined effects of carbon component pyrolysis behavior and heterogeneous contraction process.In addition,such core-shell structure can alleviate the rigid stress caused by volume expansion of MnO during the cycling process,while the N-doped porous carbon shell ensured fast electrochemical reaction kinetics,resulting in excellent rate capacity and remarkable cycling stability.As expected,as LIBs anode materials,MnO@C-800 electrode showed the high reversible capacities of 915.9 and 218.1 m A h g^-1 at a current density of 0.1 and 5.0 A g^-1,respectively,and kept a reversible capacity of 894.4 m A h g^-1 at 0.5 A g^-1 over 100 cycles.2.On the basis of the previous work,the olive-like yolk-shell structured MnO@C composite（MnO@C-OYS）was synthesized by further introducing acid-assisted etching strategy,and used as the LIBs anodes.Such yolk–shell structures exhibited multiple advantages:the presence of internal void spaces alleviated the large volume expansions of MnO and the carbon shells with suitable N-doping not only enhanced the conductivity of the composite materials for efficient electron transfer but also reduced unnecessary side reactions between the material and electrolyte to form stable SEI films.Additionally,the high specific surface area suited the capacitive-dominated lithium storage mechanism for ultrafast rate capability.Therefore,as LIBs anode materials,the MnO@C-OYS electrode maintained a high reversible capacity of 441.6 m A h g^-1 at a current density of 5.0 A g^-1.3.Furthermore,the hollow hierarchical porous olive-like carbon（HHPOC）was prepared using agaric though self-template and acid-assisted etching strategy,and used as the alkali（Li,Na,K）-ion batteries anodes.The as-obtained HHPOC sample showed high specific surface area(856.0 m² g^-1)and abundant micro-/meso-pores for sufficient electrolyte penetration,and large interlayer spacing（0.42 nm）for the insertion/extraction of alkali ions.In addition,the abundant self-doped N/O heteroatoms provide plentiful active sites for storing alkali ions,leading to a capacitive-dominating storage mechanism.Therefore,as alkali-ion batteries anode materials,HHPOC electrode exhibited high reversible capacities of 1121.8,386.8 and 305.6 m A h g^-1 at 0.1 A g^-1for lithium-ion batteries,sodium-ion batteries and potassium-ion batteries,respectively.4.Finally,the two-dimensional（2D）tremella-derived carbon nanosheets（TCNs）were realized via a green and recyclable molten salt（MS）strategy using tremella as precursor,and used as the KIBs anodes.The effect of carbonization temperature on the formation mechanism and structural properties of TCNs was systematically explored.Benefiting from the high specific surface area,expand interlayer spacing and self-N doping,the as-prepared TCNs800 electrode delivered a high reversible capacity of386.3 m A h g^-1 at 0.1 A g^-1,ultrafast rate capability of 119.7 m A h g^-1 at 2.0 A g^-1 and superior cycling lifetime of 122.9 m A h g^-1 after 1000 cycles（CE,～100%）.Furthermore,the excellent electrochemical performance of TCNs800 electrode in PIBs was attributed to the enhanced pseudocapacitance-control behavior.