Synthesis Of Sb₂S₃ And Sb₂O₃ Nanorods And Their Applications In Secondary Alkali Metal Batteries

As one of the important components of the battery,the anode material often has a huge impact on the performance of the battery.In recent studies,the development of conventional intercalation anode materials such as graphite is severely restricted due to their low theoretical capacity.Alloying and conversion materials are also considered to be the most promising anode materials for next-generation secondary batteries because of their high theoretical capacity.Among them,metal sulfides and metal oxides are the most studied.However,such materials have poor electrical conductivity,and large volume change occurring during the electrochemical reaction,which results in poor rate performance and cycle stability of the batteries.Another factor limiting the commercial applications of such materials is that the synthesis of such materials is mostly complex and the reaction conditions are severely limited.This makes it difficult to achieve large-scale and efficient synthesis in production.There are also some blank for the study of such materials.Few people have systematically studied the applications of the same material in various alkali metal ion batteries,and analyzed the energy storage mechanism in different batteries.In order to provide good direction for solving the above problems,and some theoretical basis for the latecomers to study the energy storage of Sb-based anodes.This thesis synthesized Sb₂O₃,Sb₂S₃ and Sb₂S₃@PPy nanorods through low-cost and facile synthetic methods.Firstly,the sodium storage performance of Sb₂O₃ is studied.Then the electrochemical performances of Sb2S3@PPy in lithium,sodium,and potassium ion batteries are studied.The main results and conclusions of this thesis summarized as follows:?1?Sb₂O₃ was synthesized by using the Sb powder as raw material,and Sb₂O₃rods with different sizes were synthesized by changing the reaction conditions.Then the sodium storage performances of the synthesized materials are studied.Among them,nano-scale Sb2O3 has better sodium storage performance.The initial reversible capacity is 440 mAh g^-1 at 0.1 A g^-1,after 40 cycles the capacity is remained at 360 mAh g^-1.Indicating that material nanocrystallization is beneficial to the improvement of electrochemical performance.?2?The Sb₂S₃@PPy coaxial nanorods were prepared by two steps.First,Sb₂S₃nanorods were prepared using a hydrothermal method.Then,as the template,Sb₂S₃nanorods were coated with a homogeneous polypyrrole?PPy?layer through a solution reaction.The comparison of the performances of those two samples in lithium ion and sodium ion batteries shows that the PPy coating effectively solves the problem of poor electrical conductivity of Sb2S3 and capacity degradation caused by structural damages during cycling.Then we systematically studied the energy storage performance of Sb₂S₃@PPy in three kinds of alkali metal ion batteries.Sb₂S₃@PPy exhibits excellent electrochemical performances in three kinds of batteries,especially in sodium and potassium ion batteries,which is superior than most of the reported similar materials.In sodium ion batteries,the initial reversible capacity is as high as 940 mAh g^-1 at 0.1A g^-1,and remained at 880 mAh g^-1 after 50 cycles,which is the highest among the reported Sb-based materials.In potassium ion batteries,the initial reversible capacity is maintained at 490 mAh g^-1 at 0.1 A g^-1,and remained at 700 mAh g^-1 after 18 cycles.Subsequently,the energy storage mechanism of Sb2S3@PPy in three kinds of batteries was compared and analyzed.It is found that the energy storage process in sodium ion batteries is similar as the capacitor.There is no obvious platform in its galvanostatic charge and discharge curves,and no redox peaks in CV curves,which is different with those in potassium and lithium ion batteries.