Preparation And Electrochemical Performance Of 3D Interconnected Carbon Tube Array As Anode For Lithium-Ion Batteries

Lithium-ion batteries(LIBs)are the most extensively used secondary batteries.To satisfy the development demand of new electronic devices like electric vehicles and energy storage networks,it is particularly important to develop LIBs with long cycle life,high power density and high energy density.Among all the anode materials,transition metal oxides and silicon-based anode materials have drawn extensive attention due to their high theoretical capacity,and environmental friendliness.Nevertheless,low conductivity and large volume variation during charge-discharge process restrict their further application.To solve these problems,in this paper we design and construct self-supported three-dimensional interconnected carbon tube(3DCT)film loaded with anode materials,which not only solved the problems of low conductivity and volume expansion of active materials,but also avoided the use of binder and metal collector.The energy and power density based on the mass of the electrode are greatly improved.Furthermore,we investigated the reaction mechanism and electrochemical performance of these self-supported electrodes and revealed the mechanism and universality of 3D-CT in improving electrochemical performance of anode materials.The main research contents and results are as follows:1.Three-dimensional interconnected carbon tube membrane loaded with Mn3O4 nanoparticles(Mn3O4-NPs)and carbon nanotubes(Mn3O4-NPs/CNTs@3D-CT)has been successfully prepared.As the anode of LIBs,it shows excellent cycling and rate performance(based on the mass of the entire electrode).The integrated freestanding structure avoids the use of inactive materials such as conductive agent and binder,which greatly improves the conductivity of the electrode and the transport speed of ions.The presence of 3D-CT and CNTs not only effectively solved the problem of volume expansion Mn3O4,but also established a good conductive path between 3D-CT and Mn3O4-NPs,solving the problem of low conductivity.The effect of lithium hexafluoropropane-1,3-disulfonimide(LiHFDF)-based electrolyte on the cycling performance of electrode was studied.Moreover,we verified the conversion reaction model of transition metal oxides and investigated the lithium storage mechanism of Mn3O4-NPs/CNTs@3D-CT electrode by in-situ and ex-situ characterization.2.Free-standing 3D-CT electrodes loaded with ultrafine SnO2 nanoparticles(SnO2NPs@3D-CT)were synthesized using three-dimensional porous alumina oxide(3DAAO)as templates.The ultrafine SnO2 nanoparticles can not only effectively slow the volume variation of SnO2 nanoparticles,but also effectively inhibit the coarsing of Sn,thus greatly improving the initial coulomb efficiency(CE)of SnO2-based electrodes.The integrated carbon tube grid structure effectively improves the electrical conductivity and structural stability,and also provides a fast ion transport channel.In addition,freestanding structure avoids the use of binder,conductive agent and metal collector,solves the problem of low mass loading of active materials in the electrode,and greatly improves the cycling and rate performance of SnO2-based electrode based on the mass of the entire electrode.3.Based on the previous work,the 3D-CT electrode loaded with NiO and SnO2 nanoparticles(NiO/SnO2-NPs@3D-CT)was prepared successfully.The presence of NiO can not only provide additional capacity,but also catalyze the conversion of Sn to SnO2 by Ni nanoparticles formed during the process of lithium intercalation,which can further improve the initial CE and capacity of the SnO2-based electrode,which solve the problem of low initial CE of the SnO2-based electrode.In addition,the vertical carbon tube of 3D-CT can also shorten the transport distance of ions and electrons,so as to realize the rapid transport of ions and electrons.As the anode of LIBs,it not only shows excellent electrochemical performance in half battery,but also exhibits good cycling and rate performance when it is assembled with LiCoO2 cathode in full cell,which has potential to replace commercial graphite anode and has important guiding significance for the development of high-performance SnO2-based anode.4.A self-supported three-dimensional interconnected carbon@silicon tube membrane(3D-C@void@SiT)electrode with core-shell structure is proposed using 3D-AAO as a template.The electrochemical performance of the anode was investigated.The interconnected silicon tube array and core-shell structure can accommodate the drastic volume variation of silicon,and keep the stability of the structure.The coated carbon layer can not only further release the volume change of silicon,maintain the stable SEI film,but also enhance the electrical conductivity of the electrode.The integrated structure avoids the use of inactive materials and increases the capacity performance based on the electrode level.The vertical channels bridge the transport distance of Li+and electrons and enhance their electrochemical performance at high current densities.