High Performance Anodes For Lithium/sodium Ion Batteries Prepared By Dealloying Technology

The fossil fuels burning caused by cars,thermal power generation and so on intensify the greenhouse effect.Renewable and sustainable energy(solar,wind,tidal,biomass and so on)have attracted more and more attention.However,the inherent discontinuity of these renewable energies makes their application limited.Energy storage systems based on electrochemical principles can overcome the limitations.Lithium-ion batteries(LIBs)have been widely used in portable electronic devices and electric cars.Although the energy density of LIBs has increased nearly four times in the past two decades,nowadays,there is a bottleneck for LIBs.The current graphite LIB anode can be replaced by higher specific capacity anode materials(such as silicon,germanium,phosphorus and so on)to increase the energy density of LIBs.But during charging and discharging process the large volume changes of these high capacity electrodes can result in electrodes pulverization,destroying its conductive network.The design of nanostructures(such as nanoporous structure,nano wires,nano arrays,core-shell nanostructures and so on)can alleviate electrode volume expansion effectively.Sodium resource is richer than limited lithium resource,sodium ion batteries(SIBs)are potential substitutes for LIBs.Due to big sodium ion radius,the volume expansion of electrodes during charge and discharge process is also a tough chanllenge for SIBs.Combining the casting and dealloying techniques,the nanoporous germanium,nanoporous antimony,red phosphorus@Ni-P core@shell nanostructures and bismuth nanorods,a series high performance Li/Na ion battery anode materials were prepared,and the simple process allows large-scale preparation.First,Al71.6 Ge28.4 precursor was prepared by rapid solidification technology.Nanoporous germanium(np-Ge)was prepared by chemical dealloying the precursor in 5 wt%hydrochloric acid,allowing for mass-production of electrodes for LIBs.The chemical dealloying mechanism of Al71.6Ge28.4precursor was analysed by XRD,SEM,TEM and so on.With dealloying time increasing(0.5 h,2 h,6 h and 10 h),more and more aluminum of the precursor reacted with the acid.The pores in the precursor gradually increased and finally the np-Ge formed.Nanoporous structure can accommodate volume changes during the lithiation/de-lithiation progress and increase the contact area between electrode and electrolyte.The np-Ge as an advanced anode materials for LIBs shows a promising electrochemical performance with a specific capacity of 1191 mAh g-1 after 160 cycles at a rate of 160 mA g-1 and good rate capability.When the current density increase from 480 mA g-1,800 mA g-1 to 1600 mA g-1,the specific capacity maintains 1020 mAh g-1,910 mAh g-1 and 767 mAh g-1,respectively.Second,we have presented a comprehensive study of using chemical dealloying methods to control the morphology of nanoporous-antimony(NP-Sb)and the size of Sb particle.For the first time depending on regulating the Al-Sb alloy composition,coral-like NP-Sb(NP-Sb70),honeycomb-like NP-Sb(NP-Sb80)and Sb particles(Sb10,Sb30 and Sb45)with different size were prepared by chemical dealloying of Al30Sb70,Al20Sb80,Al90Sb10,Al70Sb30 and Al55Sb45(at%)alloy ribbons respectively,a top-down process.The excellent electrochemical performance of NP-Sb70 is because of its innovative electrode design which ensures strong structural integrity,high sodium ion accessibility,and fast electrode transport.The internal porous structure not only can increase the contact area between electrodes and electrolyte,but also accommodate the volume change during sodiation-desodiation process.The NP-Sb70 delivered a high capacity of 573.8 mAh g-1 after 200 cycles at a rate of 100 mA g-1 and good rate capability as anode for sodium-ion battery(SIB)(the capacity of NP-Sb70 can maintain 510 and 420 mAh g-1 at current density of 1320 and 3300 mA g-1,respectively).This scalable strategy shall pave the way for mass-production of large-capacity electrodes for SIBs,providing new guidelines for optimizing synthesis of nanostructures.Thirdly,arrayed bismuth(Bi)nanorod bundles were prepared by chemical dealloying of Al30Bi70(at%)alloy ribbon,a top-down process.The arrayed Bi nanorod bundles exhibit high retention capacity of 301.9 mAh g-1 after 150 cycles at a rate of 50 mA g-1,flat potential profile and good rate capability(292.5 211.8,142.6 and 102.3 mAh g-1 at 100,5 00,1000 and 2000 mA g-1,respectively)as advanced anode for sodium-ion batteries(SIBs).The excellent electrochemical performance is due to high ion accessibility and fast electron transport of arrayed Bi nanorod bundles,which is essential to improve rate capability of SIBs.This scalable strategy shall pave the way for mass-production of large-capacity electrodes for SIBs and other energy storage systems,providing new guidelines for preparation of 1-D nanostructure array.Finally,we have presented a comprehensive study of combining electroless deposition with chemical dealloying to control the shell thickness and composition of red phosphorus(RP)@Ni-P core@shell nanostructure as a high performance anode for SIBs.The mechanisms of ion,electron transport and the amorphous Ni-P dealloying were studied.The in-situ generated Ni2P on RP particle surface can facilitate intimate contact between RP and mechanically strong amorphous Ni-P outer shell with a high electronic conductivity,which ensures strong electrode structural integrity,stable solid electrolyte interphase and ultra-fast electronic transport.The structure of amorphous Ni-P shell can be regulated by chemical dealloying to balance the electron and ion transportation ability.Finally,the electrochemical performance can be controlled by chemical dealloying.The chemical dealloying mechanism of amorphous Ni-P was first studied.As a result,the 8h RP@Ni-P composite presents asuper high capacity(1256.2 mAh/gcomposite after 200 cycles at 260 mA/gcomposite),superior rate capability(491 mAh/gcomposite at 5200 mA/gcomposite)and unprecedented ultralong cycle-life at 5000 mA/gcomposite for RP-based SIB anode(409.1 mAh/gcomposite after 2000 cycles).The simple scalable synthesis approach shall provide new strategy for the optimization of core@shell nanostructure,paving the way for mass-production of high performance electrodes for SIBs and other energy storage system.