Design And Preparation Of Nanoporous Si-based Composites And The Study Of Their Lithium Storage Performance

Lithium-ion batteries?LIBs?have played the vital role in our daily lives as the dominant power sources for diversified portable electronics owing to their high energy density,long cycle life,and environmental friendliness.In order to obtain much higher energy density for LIBs,the electrode materials must possess large specific storage capacities.However,the current graphite-type anodes for LIBs possess intrinsically low theoretical specific capacity,which restricts their application in facing the demand of large energy and power density.Silicon?Si?is recognized as the most promising anode material to replace or complement graphite in LIBs.Unfortunately,Si has the drawbacks of low conductivity and large volume expansion during alloying with lithium,which usually leads to poor cycle stability and rate performances.In order to solve these problems,engineering special nanoarchitectures and combining Si with highly conductive components have been shown to be the most favorable strategies to buffer the large volume changes of Si and enhance the electrical conductivity of Si anodes.In this work,we present the straightforward fabrication of three-dimensional porous Si-based composites with rich porosity by using a two-step approach to combine controlled alloy refining and facile electroless dealloying.The as-made Si-based composites show enhanced electrochemical performance as anode materials for LIBs.The main contents of this paper:1.The SiSnAl,SiTiAl,and SiNiAl ternary alloys with uniform and controllability compositions were designed and refined by the study of phase diagram and analysis.By etching the Al atom in 0.05 M NaOH solution for the certain time,the remained atom will spontaneously formed three-dimensional porous network nanoarchitecture,such as nanoporous?NP?Si/Sn,Si@TiO₂,and Si/Ni composites.2.The morphology and compositions of the as-made NP-Si/Sn,NP-Si@TiO₂,and NP-Si/Ni composites were characterized.It shows that NP-Si/Sn composites have a uniform bicontinuous porous structure in three dimensions with micro-nano bimodal pore size distribution and the Sn nanoparticles are uniformly dispersed on the porous skeleton.The NP-Si@TiO₂ composites possess the 3D open bicontinuous network structure and the nanoporous TiO₂ with smaller ligaments distributed on surface of the larger ligament of Si to form the unique core-shell structure.The NP-Si/Ni composites own the bulky porous structure with many large voids distributed on the surface.Through the XRD,EDS,and XPS analysis,it can be known that it is easy to realize controllable components and uniform structures with this simple approach.3.Characterizing the electrochemical performance of as-prepared NP-Si/Sn,NP-Si@TiO₂,and NP-Si/Ni composites.They exhibit high capacity,excellent cycling reversibility,long cycle life and good rate capability for lithium storage.With the advantages of unique performance and easy preparation,the as-made composites have potential for application as advanced anode materials for LIBs.