With the development of human society and the increasing popularity of electronic devices,there is an increasing demand for secondary batteries.Due to the high enegy density,high working voltage,long cycle life,environmental friendniess and high efficiency,lithium-ion batteries(LIBs)have been successfully applied in our daily life.However,the limited reserves of lithium resources,which seriously increases the cost of lithium ion batteries and restricts their wide application.Therefore,the development of new electrode materials with high specific capacities to improve the cycling life and energy density of the battery has become the current mainstream trend.On account of increasing demand for energy storage devices,sodium-ion batteries with abundant reserve,low cost and similar electrochemical properties,have the potential to partly replace the commercial lithium-ion batteries.Iron-based electrode mnanoparticles aterials with abundant raw materials and high energy density have been focused researchers interests in recent years.However,there are some problem himered their widely application,such as large volume change,poor rate performance and cycling performance.Therefore,it is very important to carry out the structure design and surface modification to improve their electrochemical properties(1)Developed an effective and simple in-situ encapsulation and transformation strategy to implant well-distributed pyrite nanoparticles into spherical porous carbon frameworks to form pitaya-structured spheres.Benefiting from such special architecture features,the as-synthesized pitaya-structured cathode can successfully buffer the volume change and prevent aggregation of FeS2 nanoparticles during the charge/discharge processes.The vesica-like carbon matrix provides an unhindered pathway for electron transport and Li+diffusion and restricts the thin solid-electrolyte interphase layer to the outer surface of carbon outer-shells.The current conversion-based electrode displays a high and stable energy density(about 1100 Wh kg-1 at 300 mA g-1),ultrahigh rate capability(a reversible capability of 660,609,554,499,449,and 400 mA h g-1 at 0.2,0.5,1.0,2.0,5.0,and 10 A g-1,respectively),and stable cycling performance(a reversible capability of 614 mA h g-1 at 0.3A g-1 after 100 cycles)(2)Rationally designed a facile metal-organic framework(MOF)-derived selenidation strategy to synthesize in-situ carbon-encapsulated selenides as superior anode for LIBs.This peapod-like Fe7Se8@C with nano-structured features delivered ultra-stable cycling performance at high charge-discharge rate and demonstrated ultra-excellent rate capability.The uniform peapod-like Fe7Se8@C nanorods represent a high specific capacity of over 560 mAh g-1 after 200 cycles at 3 A g-1 and deliver a capacity of 654.8,642.5,634.5,622.9,566.4 and 458.6 mAh g-1 at the current density of 0.1,0.2,0.5,1.0,2.0 and 5.0 A g-1,respectively.The current simple MOF-derived method could be a promising strategy for boosting the development of new functional inorganic materials.(3)To solve the agglomeration of Fe and low electronic conductivity of FeP anode,a simple route through MOF-derived phosphorization has been successfully explored for in-situ encapsulation of FeP nanoparticles in porous carbon framework(FeP@C).The MOF-derived FeP@C anode can substantially inhibit the coarsening of small Fe,improve the electroconductivity and moderate the volume expansion of electrode,leading to superior rate capability and excellent cycling performance for Li-ions storage.The FeP@C anode delivers a high reversible capacity of 700 mAh g-1 at 0.1 A g-1 over 180 cycles and delivers a capacity of 760,685,623,579,521,445 and 363 mAh g-1 at the current density of 0.1,0.2,0.5,1.0,2.0,4.0 and 8.0 A g-1,respectively.The kinetic analysis,calculated diffusion coefficient and partial density of states(PDOS)results also confirmed this in-situ carbon encapsulated strategy improves the conductivity of FeP particles facilitating the alkali-ion/electron’s transportation.(4)An anode of self-supported FeP@C nanotube arrays on carbon fabric(CF)has been successfully fabricated via a facile template-based deposition and phosphorization route:first,well-aligned FeOOH nanotube arrays were simply obtained via a solution deposition and in-situ etching route with hydrothermally-crystallized(Co,Ni)(CO3)0.5OH nanowire arrays as the template;subsequently,these uniform FeOOH nanotube arrays were transformed into robust carbon-coated Fe3O4(Fe3O4@C)nanotube arrays via glucose adsorption and annealing treatments;finally FeP@C nanotube arrays on CF were achieved through facile phosphorization of these oxide-based arrays.Such a unique structure design promises the achievement of FeP@C anodes with stable cycling performance(a large and stable capacity of 712 mA h g-1 at 0.5 A g-1 over 270 cycles,corresponding to area capacity of 1.31 mA h cm-2 at 0.92 mA cm-2)and superior rate capability(a reversible capacity of 945,871,815,762,717 and 657 mA h g-1 at 0.1,0.2,0.4,0.8,1.3 and 2.2 A g-1,respectively,equal to 1.73,1.59,1.49,1.39,1.31,1.20 mA h cm-2 at 0.18,0.37,0.732,1.46,2.38 and 4.03 mA cm-2,respectively).The assembled LiCoO2//FeP@C full cell can also deliver a capacity of 932、783、716、624、515 mAh g-1 at 0.1,0.25,0.5,0.5,1.0 and 2.5 A g-1,respectively(equal to 1.70、1.43、1.31、1.14、0.94 mA h cm-2 at 0.18、0.37、0.92、1.83、4.58 mA cm-2,respectively).(5)Based on the previous prepared FeOOH nanotube arrays,robust carbon-coated Fe(Fe@C)nanotube arrays was obatained via glucose adsorption and annealing treatments under H2/Ar atmosphere.Finally,FeF3@C nanotube arrays were achieved through facile fluorination of these Fe@C arrays.As cathode for LIBs,these FeF3@C nanotube arrays exhibit superior rate capability(delivers a capacity of 676,564,487,367,251 and 123 mAh g-1 at the current density of 0.1,0.2,0.5,1.0,2.0,and 5.0 A g-1,respectively)and stable long-cycling performance(delivers a high reversible capacity of 368 mAh g-1 at 0.1 A g-1 over 90 cycles). |