Preparation And Sodium Storage Properties Of Biomass Derived Carbon-based Anode Materials

With the rapid depletion of fossil fuels,resulting in the shortages of resource scarcity and environmental pollution,environmental protection energy such as the energy of solar and tide have got rapid development,and the new energy storage system plays a key role in the use of renewable resources.Due to the high security and low cost,the sodium-ion batteries（SIBs）as a new system exhibits excellent application potential.In the research field of electrode materials,biomass hard carbon has attracted widespread attention due to the environment friendly and abound resources,which exhibit a broad market prospect.However,biomass carbon materials generally have poor rate performance and low initial coulombic efficiency（ICE）in related research,which seriously hinders the business application process.In this work,the bamboo,duckweed and camphor wood were selected as precursors basing on the different biomass characteristics,and the connection between the structure and sodium storage properties was studied by different preparation methods to explore the main factors affecting the rate performance and ICE.The main works are shown as follows:（1）Bamboo-based hard carbon was prepared by high temperature carbonization to explore the relationship between carbonization temperature and the hard carbon structure and sodium storage performance.The results indicate that the layer spacing and degree of disorder gradually decrease with the increase of pyrolysis temperature.Furthermore,the specimen prepared at 1300°C exhibits the best electrochemical performance in that the initial charge capacity is 292.2 m Ah g^-1 at 20 m A g^-1 and it exhibits capacity retention of 88.2%after 100 cycles at 100 m A g^-1.In addition,the electrochemical behavior of the hard carbon was probed,which laid the foundation for the following work.（2）Based on the above work,the duckweed which rich in pore structure and heteroatom was selected as the carbon source to prepare the hard carbon with excellent rate performance by activation and doping,and the effects of heteroatom doping amount on the sodium storage performance were probed.The synergistic effect of activation and doping can effectively ameliorate the diffusion kinetics and surface adsorption capacity of the hard carbon.The material prepared at the optimal condition exhibits high capacity at 1000 m A g^-1which is 144.2 m Ah g^-1 with an excellent rate performance.（3）Combined with the above studies,which can be seen that the biomass hard carbon generally exhibited the low ICE.Therefore,camphor wood with an uncomplicated structure was chosen as the carbon source to prepare the low defect hard carbon by controlling the heating rate,exploring the main factors influencing ICE.The results indicate that the obtained hard carbon exhibits low defect concentration and specific surface area and with the decrease of heating rate.The hard carbon prepared at the heating rate of 0.25°C min^-1 exhibits ICE of 82.8%at 20 m A g^-1with the 90.0%capacity retention after 200 cycles at 50 m A g^-1.The full cell prepared by matching the hard carbon anode with the Na₃V₂（PO₄）₃/C cathode displays the high energy density which is 245.3Wh kg^-1,indicating excellent electrochemical performance.