Syntheses Of Metal Chalcogenide Composites And Their Applications As Anode Materials For Lithium/Sodium Ion Batteries

As environmental pollution and the energy crisis become increasingly problematic,the accelerated development and use of renewable and clean energy are urgent challenges for society as a whole in order to achieve the sustainable development goal of "Carbon Neutrality".Among the many energy storage devices,lithium-ion batteries have been widely used in various fields of production and life due to their small size,light weight and high energy density,such as mobile phones,electric cars,laptops and other electronic devices.However,compared with lithium,sodium is more abundant in nature,making it cheaper to produce sodium-ion batteries,so they are more suitable for large-scale power storage systems.Lithium/sodium ion batteries consist of a cathode,an anode,a separator and an electrolyte.The anode,as an important part of the battery,is a key factor in determining the performance of the battery and has therefore been extensively studied.Among them,metal chalcogenide composites stand out among the many anode materials due to their superior electrochemical properties,such as high theoretical specific capacity and low chemical reaction potential.In addition,studies have been shown that the design of more reasonable morphology structure is also very important to improve the performance of lithium/sodium ion battery anodes.A reasonable morphological structure can,on the one hand,play a protective role for metal particles,such as alleviating the volume expansion of metal particles during charging and discharging,and on the other hand,improve the electron transport rate and the diffusion rate of lithium/sodium ions,thus improving the multiplicative performance and cycling stability of lithium/sodium ion batteries.Based on the above research background,this thesis investigates the synthesis of metal chalcogenide composites and their performance when used as anode materials for lithium/sodium ion batteries,using metal chalcogenide composites as the research target.The main research contents are as follows.1.The composite material（Ni@NC-rGO）with nitrogen-doped carbon nanotubes encapsulated with nickel nanoparticles on reduced graphene oxide sheets was prepared by catalytic chemical vapor deposition,and then Sb3+ were introduced into the nitrogen-doped carbon nanotubes by solvothermal method.Finally,Sb2Se3 nanoparticle was successfully encapsulated in nitrogen-doped carbon nanotubes through high temperature selenization,and Sb2Se3@NC-rGO composite was obtained.The material exhibited excellent rate performance and cycling stability when applied to lithium-ion battery anode material.The specific discharge capacity was 1408,1145,1017,877,676 and 494 mAh g^-1 at current densities of 0.2,0.5,1.0,2.0,5.0 and 10.0 A g^-1,respectively,and remained at 1330 mAh g^-1 when the current density returned to 0.2 A g^-1.In addition,the electrode can maintain a discharge specific capacity of 451.1 mAh g^-1 after 450 cycles at a current density of 2.0 A g^-1 and can maintain a discharge specific capacity of 192.6 mAh g^-1 when cycled at a high current density of 10,000 cycles at 10.0 A g^-1.2.A porous hexagonal NiTe₂/NC sheet ocomposite forming a heterogeneous structure between a nitrogen-doped carbon layer and NiTe2 crystals was successfully synthesized by a self-polymerization reaction under a hydrothermal reaction and a subsequent carbonization reaction.The material exhibits high reversible specific capacity and long cycle stability when used as the anode material for sodium-ion battery.A high reversible discharge capacity of 351 mAh g^-1 can be achieved after 300 cycles at a current density of 1 A g^-1.When the current density is increased to 10 A g^-1,a high discharge capacity of 271 mAh g^-1 can still be achieved after 1200 cycles.