| As the world's population expands and the economy grows,energy consumption increases.Due to the limited resources of fossil energy,research on clean,renewable and sustainable energy technologies has become an urgent problem to be solved.Lithium-ion batteries(LIBs)are the dominant power source for a wide range of portable electronic devices due to their high energy density,long lifespan and environment benignity.Even though the property of LIBs has already been considerably enhanced in recent years,further improvement of both their energy density and power density is still attracting much attention.Silicon has drawn much attention due to its high theoretical specific capacity(4200 mAh/g).However,novel silicon-based nanomaterials usually need multi-step and advanced fabrication process,making the products costly.As an alternative,silica(SiO2)has been considered to be the anode materials of LIBs because of the analogous advantage of storing a large quantity of lithium and relatively low discharge potentials.Besides,SiO2 is one of the most abundant materials on Earth and the major constituent of sand and therefore,the cost is cheaper than other metal-based materials.However,SiO2 can form a large amount of irreversible products during the first reaction,which leads to a low first Coulombic efficiency(CE).In order to solve this problem,we prepared SiO2 materials and lithiated it.Then,we systematically study the electrochemical performance of SiO2 and lithiated-SiO2 anode materials.First,we derived SiO2 nanoparticles from rice husks.Through SEM and XRD,we identified that the derived SiO2 particles are amorphous nanoparticles with porous structure.The particles were lithiated via a thermal methods.The mainly constituent of the lithiated products are Li21Si5 and Li2O.After prelithiation,the porous network was destroyed in a certain degree.The cycling and CV tests were implemented.The result show that pre-lithiation can enhance the first CE effectively.In order to further study the influence of particle size on the electrochemical performance of pre-lithiation products,we systematically invested SiO2 particles with different sizes varying from 6 nm to 3 um.All prelithiated composites exhibit better performance than that of untreated SiO2.The nano-particle,which is often thought to be more competitive in battery performance,however,lost its superiority after prelithiation.Contrary to our expectations,the micron-sized SiO2 particle demonstrates more stable cycling performance,delivering a prelithiation capacity of 1412 mAh/g and a reversible specific capacity over 1300 mAh/g after 50 cycles.Finally,we propose the idea of directly pre-lithiation sand as the anode material for lithium-ion batteries.First,we use the mechanical ball milling to make the sand particle size more uniform.After pre-lithiation treatment,we perform electrochemical tests such as cycling and C V.Experiments show that pre-lithiation can make sand react with Li,which is usually considered to be inactive to Li.The reaction form LixSi/Li2O composite.The as-prepared electrode has a first lithium insertion capacity of about 2400mAh/g,and the first coulombic efficiency is greater than 90%.LixSi/Li2O alloy derived from sand has a good cycling performance.After 50 cycles,it still maintains a reversible capacity of about 1700mAh/g,and the capacity retention rate is about 70%.After 120 cycles,the material capacity was maintained at around 1500mAh/g.In conclusion,pre-lithiation can effectively improve the electrochemical activity and the first Culombic Eficiency of the SiO2 electrode,which solved a big problem for the application of SiO2 in the anode material of high performance lithium ion battery... |
PDF Full Text Request