Microstructure Control Of Tin- And Molybdenum-Based Anode Materials And Lithium Storage Performance Reversible

Lithium ion batteries(LIBs) have attracted great attention due to the explosive demand for portable, entertainment electronic equipment required by today’s information-based society and intelligent times. In order to expand the applications of LIBs in these portable consumer electronic devices, even in hybrid electric vehicles(HEVs) and electric vehicles(EVs), more research and improvements on batteries are necessary. Reversible electrode materials are at the center of research relating to lithium ion batteries, which require high loading capacity, high power and high energy density. For the anode materials, carbon negative electrodes cannot satisfy the ever-growing demand for high capacity high power and high energy density. Therefore, achieving significant increase in energy and power density to meet the future challenges is essential. Research found that metal dioxides have higher capacity than the commercial graphite anode material and will be the substitute material.In order to develop new anode material with high specific capacity, high chemical stability, long cycle life and good safety, the domestic and foreign researchers have been interested in improving the properties of metal oxides. But the main drawback of this kind of material is that the capacity is fast fading, the cycle stability is not good, and the first irreversible capacity loss is large, and the charge discharge efficiency is relatively low. When metal oxide used as electrode materials, lithium ions in the oxide prolapse is relatively slow process, first embedded lithium usually cannot be completely prolapse. With the infiltration of circulation in the process of oxides was the volume change, electrode structure loose and electrolyte solution, lithium diffusion channels will continue to open up. At the same time, instability of the electrode material structure due by continuous embedding of lithium ions and deintercalation affect battery electrochemical performance. In order to improve the performance of the material, we designed a variety of micro / nano structure materials with high specific capacity from the structure and composition of the material. The work of this paper is mainly divided into the following several aspects:(1)ultrafinecarbon-coatedsno2nanoparticles(nps)withdiametersof3–6nmarepreparedbyahydrothermalmethodinthepresenceofascorbicacidandsubsequentthermaltreatment.theascorbicacidwasthestructuredirectingagentinthereactionandtheexcessivepartcanbeusedascarbonsources.whenevaluatedasananodematerialforlithium-ionbatteries,theas-synthesizedultrafinecarbon-coatedsno2npsexhibitahighreversiblecapacityof688.6mahg-1atarateof1cafter50 cycles.theperfectelectrochemicalperformancecanbeascribedtotheconductivecarbonshellsurroundingthenpsandtheultra-smallsizeoftheactivematerial,whichcaneffectivelybufferthevolumeexpansion/contractionduringli+insertionandextractionandimprovetheconductivityoftheelectrode.followingup,whenthesno2werereducedbyh2/ar,untrafinesnnanoparticleswithsmallcrystalhavebeensynthesized.theuntrafinesnnanoparticlesexhibitshighcapacityandexcellentelectrochemicalstabilitywhenusedasananodematerialforlithium-ionbatteries.(2)sno2hollowsperhersissynthesizedbyasimplehydrothermalhydrolysisofna2sno3.thediameterofsno2hollowsperherswasabout100~120nm,theinnerdiameterwasabout60~80nmandthethicknessofthehollowsperewasabout20nm.whenusedasanodematerials,thesno2 hollowsperhersmaterialsshowhighdischargecapacityandexcellentelectrochemicalstability.(3)copperandcarbonco-encapsulatedtindioxidenanosphereswithdiametersof8-10nmweresynthesizedthroughasimplesolutionsystemandfollowingcarbonationinn2 atmospheres.theultra-smallsno2grainandtheco-encapsulatedcopperandcarbonshellcaneffectivelyincreasethestabilityoftheactivematerials.whenusedasanodematerialsforlithium-ionbatteries,thecompositesexhibitedgoodelectrochemicalperformancewithhighspecificcapacityof670.3mahg-1after50cyclesatthecurrentdensityof0.2ag-1.(4)large-scalemoo2/carboncompositeshavebeensynthesizedbysimplehydrothermalreductionprocess.moo2/cnanosphereswiththediameterabout15~25nmwereinterconnectedtoformacage-likearchitecture.furthermore,withawater-solublebinder(sodiumalginate),thecage-likemoo2/ccompositesexhibitedahighdischargecapacityandsignificantlyimprovedcyclingperformancecomparedtopreviouslyreportedmoo2-basedanodematerials.theelectrodeswiththemoo2/ccompositescandeliveracapacityof692.5mahg-1after80charge/dischargecyclesatacurrentdensityof200mag-1.afterc-ratemeasurement,thebatterystillcanmaintainexcellentcyclingstability(about550mahg-1reversiblecapacityretainedevenafter475cycles).(5)high-surface-areaf-dopedamorphousmoox(a-moox)issynthesizedbyhydrothermalhydrolysisofammoniummolybdatetetrahydrateinwater-ethyleneglycol(h2o-eg)mixedsolvent.theresultanta-mooxhasasurfaceareaashighas212.74m2g-1andexhibitshierarchicallymicroporous-mesoporousstructure.theelectrochemicalmeasurementsthatdemonstratethehigh-surface-areaf-dopeda-mooxexhibitshighcapacityandexcellentelectrochemicalstabilitywhenusedasananodematerialforlithium-ionbatteries.somesynergisticfactorsincludingf-doping,highspecificsurfacearea,andporousstructure,mayberesponsibleforthegoodlithium-storageperformance.