Design And Synthesis Of VA-based Nanostructured Electrode Materials For Lithium/Sodium Storage

Along with the improvement of people’s living standard,portable electronic devices have been widely used in our daily life.Li-ion batteries（LIBs）have become the most popular portable energy storage device,due to its light-weight,high-capacity,long-life performance.However,low reserve abundance and unbalanced distribution of lithium restrict the sustainable development of LIBs.Owing to high-reserve,widely distributed and low-cost of sodium,sodium ion batteries（SIBs）have attracted more and more attention,which are regarded as important options for high-performance secondary batteries.At present,graphite materials are common anode materials for LIBs in commercialized company,however,the low specific capacity of 372 mAh g^-1 for LIBs and 35 mAh g^-1 for SIBs greatly affects the application in lithium/sodium storage.VA alloy（Sb,Bi,P）anode materials have a higher theoretical capacity.However,the large volume changes during alloy/de-alloy process,causing seriously pulverization of the electrode material,which decreases the cycling performance of the alloy electrodes.The nanomaterials of alloy material can effectively buffer the volume change during cycles,and restrain the pulverization of alloy,which improve the cycling performance of electrodes.In this dissertation,we design and synthesize several different types of VA anode materials,which exhibit excellent electrochemical storage lithium/sodium properties.The main content and innovation points are summarized as follows:（1）We prepared few-layer antimonene（FLA）by a method of liquid-phase exfoliation.The FLA anode exhibits a capacity of 620 mAh g^-1 after 150 cycles at a current density of330 mA g^-1.Considering the theoretical capacity of 660 mAh g^-1,the utilization rate is as high as 93.9%.The theoretical calculations results discloses the lower diffusion barrier of Na⁺on the single layer of antimonene is only 0.14 eV,which is lower than MoS₂,VS₂,graphene and other 2D materials.We conduct ex-SEAD,in situ XRD and theoretical calculation to disclose the excellent performance of FLA,and discover the anisotropic expansion and reversible transformation of FLA for sodium storage.（2）We prepare 0D Sb nanoparticles embedded into 2D carbon nanosheets composites.The composites exhibit a capacity of 352 mAh g^-1(based on the mass of composite materials,and 632.5 mAh g^-1 based on the mass of Sb)after a 150 cycles at 200 mA g^-1.In this structure design,internal Sb alloy nanoparticles provide high capacity,and 2D carbon layer buffer volume expansion of Sb nanoparticles,as well as improve the conductivity of composite.The structure design give full play to the synergistic effect of Sb and C.Therefore,the composite material exhibits a high-capacity and high-rate performance of sodium storage.（3）We design a simple electrochemical exfoliation method with a bias voltage of 6 V,this method can quickly and largely-scale prepare 2D porous Bi nanosheets.The 2D porous Bi nanosheets can effectively buffer the volume change during cycles,which is beneficial to improve the cycling performance.The porous Bi nanosheets anode exhibits a volume special capacity of 2517 mAh cm^-3 for the first discharge process at a current density of 0.5C.However,commercial graphite exhibits a volume specific capacity of 775 mA cm^-3 for the first discharge process.After 80 cycles,the porous Bi nanosheets electrode still has a capacity of 614 mAh cm^-3,but commercial graphite only has a capacity of 200 mAh cm^-3.Therefore,porous Bi nanosheets anode exhibits excellent high-volume capacity for LIBs.（4）We synthesize a 2D reticulated red phosphorus consisting of the cross-linking nanowires by regulating polyethylene glycol（PEG）surfactants.The 2D reticulated red phosphorus can effectively buffer the volume changes during cycles.The 2D reticulated red phosphorus exhibits the first discharge specific capacity of 1268.9 mAh g^-11 and charging capacity 845.0 mAh g^-1 at a current density of 520 mA g^-1,corresponding to an initial Coulomb efficiency（ICE）of 66.6%.However,commercial red phosphorus shows the first discharge capacity of 1125.9 mAh g^-1,and charge capacity of 38.6 mAh g^-1,corresponding an ICE of 3.4%.The 2D reticulated red phosphorus can still maintain the capacity of 316.7mAh g^-1 at 26,000 mA g^-1.The 2D reticulated red phosphorus has a wide application prospect in the fields of high-capacity and fast-charge batteries.