Synthesis And Lithium Storage Properties Of Metal Oxide/carbon Multicompoud Materials

Benefiting from the advantages of high energy density,high working voltage and none memory effect,lithium-ion batteries(LIBs)have become one of the most widely used electrochemical energy storage devices.However,with the continuous improvement of equipment technology in the area of portable electronic devices,electric vehicles and grid storage systems,commercial graphite anodes limited by low specific capacity(372 mAh g^-1)and poor rate performance,can not meet the requirements of high-rate(high-power-density)battery system.Hence,it is essential to seek anode materials with high specific capacity,good rate performance and long cycle life to develop high-performance LIBs.Currently,researchers have two main research aspects on anode materials:one is to modify anode materials without changing their chemical properties by structural design or surface modification(coating,doping);another one is to develop novel anode materials with high specific capacity and safety performance.Inspired by above directions,two kinds of anode materials with high specific capacity and excellent rate performance have been prepared in simple and efficient ways.The main contents are as follows:(1)In order to improve the rate performance of graphite anode,the niobium pentoxide/graphite multi-compoud anode materials(Nb₂O₅/C)were synthesized in different ratios by high-energy ball milling technology,employing graphite and nano-Nb₂O₅ as raw materials.After being mixed by ball-milling,part of thin graphite layers were peeled off from the graphite and nano-Nb₂O₅ was uniformly attached or embedded in the graphite layers,which could expose more active sites and improve the reaction kinetics on the electrode surface.As anode for LIBs,the influence of Nb₂O₅ content exerting on the specific capacity,cyclic stability and rate performance of Nb₂O₅/C hybrid anode was explored.The results showed that the hybrid anode electrode with a 10%quality-proportion of Nb₂O₅(Nb₂O₅/C-10%)exhibited the highest specific capacity and the best rate performance.The specific points are as follow:the Nb₂O₅/C-10%displayed a reversible specific capacity of 339.2 mAh g^-1 after 310 cycles at the current density of 1 C(higher than that of pure graphite with reversible capactity of 304.6 mAh g^-1);the capacity retention rate was up to 76%under the rate current density of 2 C(much higher than that of pure graphite with 50%).(2)An architecture of MOF-derived In₂O₃ nanocrystals/hierarchically porous nitrogen-doped carbon composite(In₂O₃/HPNC)were reported using the indium-based metal-organic framework(MOF)as the precursor.After annealing,the small-sized In₂O₃ particles were evenly embedded in the framework of nitrogen-doped hierarchically porous(micro/meso/macro-pores) carbon(HPNC).The HPNC can not only accommodate the volume expansion of In₂O₃nanocrystals,but can also offer efficient interpenetrating pathways for electrons and lithium ions to migrate rapidly during charge/discharge processes.As anodes for LIBs,In₂O₃/HPNC exhibited excellent cyclic stability and excellent rate performance.The specific pionts are as follow:a high specific capacity of 623 mAh g^-1 over 2000 cycles at 1000 mA g^-1,corresponding to an ultra-low specific capacity decay of 0.017%per cycle;even with a high rate current density of 20 A g^-1,it could show a considerable specific capacity of 136 mAh g^-1.