Preparation Of Rice Husk Derived C/SiO₂ Composites And Their Research As Anode Materials In Lithium-Ion Batteries

With the rapid development of technology,mobile electronic devices have been widely used in people's production and life.Lithium-ion batteries,as power supplies for many electronic devices,have been given attention and researched from researchers because of their advantages,including rechargeability,high energy density and environmental friendliness.In order to meet the increasing demands for performance of lithium-ion batteries in new-generation electronic devices,modification of electrode has become one of the current research hotspots in this field.Due to the low theoretical specific capacity of traditional carbon materials and the serious volume expansion effect of silicon-based materials,they cannot be used alone to meet the power requirements of modern equipments used as electrodes.Carbon/silica?C/SiO₂?composites can overcome their respective disadvantages and combine the advantages to meet the needs of the equipments.Rice husk is rich in natural carbohydrates and SiO₂.The treated rice husk can become the precursor of C/SiO₂ composites and be used as the electrode materials.In this thesis,the combination of carbonization,ball milling and activation is used to prepare C/SiO₂ composites with excellent electrochemical performance from the aspects of regulating the proportion and structure of the composites.There are two reasons to deal with the composites.On the one hand,the amorphous carbon in the materials can relieve the volume expansion of the silicon-based materials and increase the conductivity of the materials.On the other hand,the reaction between SiO₂ and the activator increases the specific surface area and the number of micropores of the materials,which provides more active sites for Li⁺and improves the specific capacity of lithium-ion batteries.The main research contents are as follows.?1?Rice husk as a precursor was carbonization under inert gas conditions.Changing temperature,which was a simple method,was used to study the effect of carbonization temperature on the oxygen-containing functional groups on the surface of rice husk,the degree of accumulation and amorphousness of C.At the optimal carbonization temperature,the composites were obtained and used as the anode electrode material for lithium-ion batteries,showing excellent electrochemical performance.The initial specific capacity reached 673 mAh g^-1 and the initial Coulomb efficiency was 61%.At the same time,the electrode could maintain the good cycling stability.After 100 cycles,the Coulomb efficiency was 99%and the capacity was maintained at 425 mAh g^-1.?2?On the basis of the previous research,the C/SiO₂ composites obtained under the optimal carbonization temperature were further modified specifically by combining high-energy ball milling,activation or two methods to prepare a series of different rice husk-based C/SiO₂ composites.The results showed that the rice husk-based C/SiO₂ composites obtained by ball milling dispersion and re-activation treatment exhibit excellent electrochemical properties.At a current density of 100 mA g^-1,the initial specific discharge capacity of the electrode was 1411 mAh g^-1,and the initial Coulomb efficiency was 53%.Even after 100 cycles,the Coulomb efficiency was as high as 98%.