The Fabricatiorn And Electrochemical Property Investigation Of Nickel/Cobalt-Based Micro-Nanostructured Metal Sulfitde And Phosphide Materials

Sodium ion battery is considered as one of the most ideal substitutes for Lithium-ion battery along with the increasing demand for renewable energy storage devices and efficient utilization of green energy(aroused by the global resource and energy shortage problems)owing to its rich resources and low cost.Among all kinds of anode materials for Sodium ion batteries(SIBs),metal sulfides and metal phosphides have become the research focus electrode materials because of their diverse advantages,such as abundant resources,low cost and high theoretical specific capacity.However,the usually rapid drop of discharge capacity and poor rate performances are the main challenges and obstacles that faced by metal sulfide and metal phosphide electrodes,which are mainly aroused by the large volume expansion/contraction during Na insertion and extraction processes and the easily dissolved tendency of electrode materials in the organic electrolyte.In order to solve these problems,our main research works are focused on the follow aspects:(1)Synthesis and electrochemical performances investigations of NiS1.03 hollow spheres and cages as anodes for half/full SIBs.NiS1.03 porous hollow spheres(NiS1.03 PHSs)and porous NiS1.03 hollow cages(NiS1.03 PHCs)with high yield were designed and selectively fabricated via a simple solvothermal and subsequent annealing approach.The obtained NiS1.03 PHSs display long-term cycling stability(127 mAh g-1 after 6000 cycles at 8 A g-1)and excellent rate performance(605 mAh g-1 at 1 A g-1 and 175 mAh g-1 at 15 A g-1).In addition,the analyses results of in-situ and ex-situ XRD patterns and HRTEM images reveals the reversible Na-ion conversion mechanism of NiS1.03.It is also worth to note that the NiS1.03 PHSs//FeFe(CN)6 full cell is successfully assembled and exhibits an initial reversible capacity of 460 mAh g-1 at 0.5 A g-1,which further evidence that NiS1.03 is a kind of prospective anode material for SIBs.(2)Ultrafine Co1-xS nanoparticles embedded in nitrogen doped porous carbon hollow nanosphere composite as anode for superb Sodium-ion batteries and Lithium ion batteriesA precursor of Co1-xS with uniform and hollow nanospherical architecture is obtained with high yield via a mild solvothermal method in the presence of 2-methylimidazole at first.And then,Co1-xS,Co1-xS/C(ultrafine Co1-xS nanoparticles embedded in the shells of the nitrogen doped porous carbon hollow nanosphere,which could not only buffer the volume change,but also shorten the diffusion paths of sodium ions and electrons),and Co1-xS@C(Co1-xS nanoparticles entirely covered by external amorphous carbon layer)are selectively fabricated via directly calcination or PPy coating&calcination of the obtained precursor It is found that Co1-xS/C shows the best electrochemical performance than the latter two materials as anodes for SIBs.It is found that the charge capacity of Co1-xS/C can be retained at 472 mAh g-1 after 120 cycles at relative high current density of 0.5A g-1,which was significantly higher than those of Co1-xS@C(122.5 mAh g-1)and pure Co1-xS(80.1 mAh g-1).In addition,559 mA h g-1 is maintained after 100 cycles at 500 mA g-1 when the Co1-xS/C composite applied as anode for lithium-ion batteries(LIBs).The high reversible capacity,excellent cycle stability combined with the facile synthesis procedure enable Co1-xS/C a prospective anode material for rechargeable batteries.(3)Rational fabrication of CoS2/Co4S3@N-doped carbon microspheres as excellent cycling performance anode for half/full Sodium ion batteriesCOS2/Co4S3@NC microspheres obtained via a simple solvothermal and subsequent annealing approach were investigated as an advanced anode material for SIBs for the first time Benefiting from the superior structural stability CoS2/Co4S3@NC spheres exhibit impressive sodium storage properties.It delivers excellent rate capability(650 mAh g-1 at 0.3 A g-1 and 217 mAh g-1 at 6 A g-1)and ultralong-term cycling performance(256 mAh g-1 after 1500 cycles at 4 A g-1 and 239 mAh g-1 after 3000 cycles at 6 A g-1).The pseudocapacitive behavior dominated redox reactions enable fast Na+ insertion/extraction and durable cycle life,which is proved by the kinetic analysis.In addition,FeFe(CN)6//CoS2/Co4S3@NC full cell was assembled and delivered a reversible capacity of 520 mAh g-1 at 500 mA g-1.This work may provide new directions for constructing promising high-performance SIBs electrodes for electrochemical energy storage.(4)Controllable preparation of sandwich-like Ni2P nanoarray/nitrogen-doped graphene nanoarchitecture composite and their electrochemical performances for sodium and lithium ion batteries.We have designed and fabricated a Ni2P/NG/Ni2P sandwich-like hierarchical structure via a simple solvothermal and subsequent annealing approach,which provide efficient ion diffusion channels and electron transfer pathways in the electrochemical process.The as-prepared Ni2P/NG/Ni2P nanoarchitecture exhibits an excellent cycling stability with a high capacity retention of 188 mAh g-1 at 0.5 A g-1 over 300 cycles as a SIB anode.Simultaneously,the synthesized nanoarchitecture delivers a capacity of 417 mA h g-1 at 0.3 A g-1 after 100 cycles when applied as anode for LIBs.The excellent cycling stability,high capacity combined with the facile synthesis procedure position the sandwich-like Ni2P/NG/Ni2P nanoarchitecture a new kind of prospective anode material for SIBs and LIBs.