Preparation And Performances Of Silicon-based Flexible Anodes With Carbon Nanotube

In recent years,lithium-ion batteries have become one of the mainstream devices in various power supply systems,and due to the emergence of portable electronic devices,bendable and foldable devices,which in turn have placed flexible requirements on lithium-ion batteries,the development of flexible self-supporting electrodes with high specific capacity and long cycle life has become a research hotspot in recent years.Among many lithium-ion battery anode materials,silicon-based anode has been of great interest to researchers because of its ultra-high theoretical specific capacity(4200 m Ah g^-1),but there are shortcomings such as large volume change（about 400%）and poor cycle stability of silicon-based anode,so it is of great importance to develop flexible silicon-based anode lithium-ion batteries with high specific capacity and stable electrochemical cycle performance.Carbon nanotubes have the advantages of good flexibility,stable chemical properties,stable mechanical properties,and good electrical conductivity,which have many applications in the preparation of flexible electrodes.Carbon nanotubes are one-dimensional tubular structures that can build three-dimensional networks,which can provide space for the volume change of silicon and inhibit the volume change of silicon to some extent,and can also improve the electrical conductivity.Some progress has been made in the preparation and research of CNT/Si flexible electrodes,such as using extraction,pulsed laser deposition,chemical vapor deposition,etc.However,there are still some problems,such as poor cycling stability,complicated preparation process,low loading,and low first efficiency,etc.New methods need to be developed and new structures need to be studied to solve these problems.In this paper,we propose a CVD combined with infiltration method to prepare flexible self-supported CNT/Si composite electrodes,and obtain CNT/（Fe@Si@SiO₂）-like core-shell structure after annealing,and excellent electrochemical performance after electrochemical testing.This paper is divided into the following aspects:（1）characterization and kinetic analysis of CNT/（Fe@Si@SiO₂）flexible negative electrode,which shows that compared with CNT/Si electrode,CNT/（Fe@Si@SiO₂）electrode promotes the interfacial electron transfer and improves the diffusion coefficient of lithium ions in the electrode,which in CNT/（Fe@Si@SiO₂）is 1.15×10^-12 cm² s^-1,which is about 2.5 times higher than that of the CNT/Si electrode;（2）the effect of loading on the electrochemical performance of the electrode was studied by increasing the loading by superposition,and the capacity could reach 1.76 m Ah cm^-2 under 1 A g^-1 at 1.04 mg cm^-2 and up to 2.2 m Ah cm^-2 at 0.2 A g^-1,and up to 2.23 m Ah cm^-2 at 0.2 A g^-1;（3）The effect of the introduction of rGO on the electrochemical performance of the electrode was investigated.The initial Coulombic efficiency,conductivity,and lithium ion diffusion coefficient of the electrode were increased after the addition of rGO.At 0.1 A g^-1,its charging specific capacity and discharging specific capacity were 1565.16 m Ah g^-1and 2284.56 m Ah g^-1,respectively,and the initial coulombic efficiency could reach68.51%,the capacity retention rate was up to 122.05%after 300 cycles,and the lithium ion diffusion coefficient also increased to 4.23×10^-11 cm² s^-1;（4）introducing Ti₃C₂T_x to study the electrochemical performance of CNT/Ti₃C₂T_x/Si flexible anode electrode.The first charge specific capacity is 2466 m Ah g^-1 and the first discharge specific capacity is 3443.60 m Ah g^-1,and its first effect is as high as 71.62%,and the reversible specific capacity of 805.80 m Ah g^-1 can still be retained after 500 cycles of charge and discharge,which has a relatively excellent cycling performance;（5）to study the effect of silicon particle size on electrochemical performance of the electrode,the capacity of 1μm CNT/Si flexible electrode was 2298.40 m Ah g^-1 and1395.70 m Ah g^-1 at 0.1 A g^-1 next discharge and first charge,respectively,and the capacity retention rate was up to 85.74%with stable cycling performance after 500cycles.After adding rGO to micron silicon particles,its first charge specific capacity was 1882.80 m Ah g^-1 and first discharge specific capacity was 2458.20 m Ah g^-1,and its initial Coulombic efficiency was up to 76.59%,and the diffusion coefficient of lithium ions in the electrode was 3.98×10^-11 cm² s^-1.