搜索
HowtobuildabetterbatterythroughnanotechnologyByRobertF.ServiceMay.26,2016,12:00PMPALOALTO,CALIFORNIA—Onadrizzly,graymorninginApril,YiCuiweaveshisscarletredTeslainandoutofSiliconValleytraffic.Cui,amaterialsscientistatStanfordUniversityhere,isheadedtovisitAmprius,abatterycompanyhefounded6yearsago.It’snocoincidencethatheisdrivingabattery-poweredcar,andthathehasleasedratherthanboughtit.Inafewyears,hesays,heplanstoupgradetoanewmodel,withacrucialimprovement:“Hopefullyourbatterieswillbeinit.”CuiandAmpriusaretryingtotakelithium--ionbatteries—today’sbestcommercialtechnology—tothenextlevel.Theyhaveplentyofcompany.MassivecorporationssuchasPanasonic,Samsung,LGChem,Apple,andTeslaarevyingtomakebatteriessmaller,lighter,andmorepowerful.Butamongthesepowerplayers,Cuiremainsapioneeringforce.Unlikeotherswhofocusontweakingthechemicalcompositionofabattery’selectrodesoritscharge-conductingelectrolyte,Cuiismarryingbatterychemistrywithnanotechnology.Heisbuildingintricatelystructuredbatteryelectrodesthatcansoakupandreleasecharge-carryingionsingreaterquantities,andfaster,thanstandardelectrodescan,withoutproducingtroublesomesidereactions.“He’stakingtheinnovationofnanotechnologyandusingittocontrolchemistry,”saysWeiLuo,amaterialsscientistandbatteryexpertattheUniversityofMaryland,CollegePark.Iwantedtochangetheworld,andalsogetrich,butmainlychangetheworld.YiCui,StanfordUniversityInaseriesoflabdemonstrations,Cuihasshownhowhisarchitecturalapproachtoelectrodescandomesticateahostofbatterychemistriesthathavelongtantalizedresearchersbutremainedproblematic.Amongthem:lithium-ionbatterieswithelectrodesofsiliconinsteadofthestandardgraphite,batterieswithanelectrodemadeofbarelithiummetal,andbatteriesrelyingonlithium-sulfurchemistry,whicharepotentiallymorepowerfulthananylithium-ionbattery.Thenanoscalearchitecturesheisexploringincludesiliconnanowiresthatexpandandcontractastheyabsorbandshedlithiumions,andtinyegglikestructureswithcarbonshellsprotectinglithium-richsiliconyolks.Ampriusalreadysuppliesphonebatterieswithsiliconelectrodesthatstore10%moreenergythanthebestconventionallithium-ionbatteriesonthemarket.Anotherprototypebeatsstandardbatteriesby40%,andevenbetteronesareintheworks.Sofar,thecompanydoesnotmakebatteriesforelectricvehicles(EVs),butifthetechnologiesCuiisexploringliveuptotheirpromise,thecompanycouldonedaysupplycarbatteriesabletostoreupto10timesmoreenergythantoday’stopperformers.Thatcouldgivemodest-pricedEVsthesamerangeasgas-poweredmodels—arevolutionaryadvancethatcouldhelpnationspowertheirvehiclefleetswithelectricityprovidedbysolarandwindpower,dramaticallyreducingcarbonemissions.Cuisaysthatwhenhestartedinresearch,“Iwantedtochangetheworld,andalsogetrich,butmainlychangetheworld.”Hisquestgoesbeyondbatteries.Hislabisexploringnanotechinnovationsthatarespawningstartupcompaniesaimingtoprovidecheaper,moreeffectiveairandwaterpurificationsystems.ButsofarCuihasmadehisclearestmarkonbatteries.Luocallshisapproach“untraditionalandsurprising.”JunLiu,amaterialsscientistatthePacificNorthwestNationalLaboratoryinRichland,Washington,putitmoredirectly:Cui’snanotechcontributionstobatterytechnologyare“tremendous.”Makingleapsinbatterytechnologyissurprisinglyhardtodo.EvenasSiliconValley’sprimaryinnovation,thecomputerchip,hasmadeexponentialperformancegainsfordecades,batterieshavelagged.Today’sbestlithium-ioncellsholdabout700watt-hoursperliter.That’saboutfivetimestheenergydensityofnickel-cadmiumbatteriesfromthemid-1980s—notbad,butnotbreathtaking.Inthepastdecade,theenergydensityofthebestcommercialbatterieshasdoubled.Batteryuserswantmore.Themarketforlithium-ionbatteriesaloneisexpectedtotop$30billionayearby2020,accordingtoapairofrecentreportsbymarketresearchfirmsTransparencyMarketResearchandTaiyouResearch.TheriseinproductionofEVsbycarcompaniesthatincludeTesla,GeneralMotors,andNissanaccountsforsomeofthatsurge.Buttoday’sEVsleavemuchtobedesired.ForaTeslaModelS,dependingontheexactmodel,the70-to90-kilowatt-hourbatteriesaloneweigh600kilogramsandaccountforabout$30,000ofthecar’sprice,whichcanexceed$100,000.Yettheycantakethecaronlyabout400kilometersonasinglecharge,substantiallylessthantherangeofmanyconventionalcars.Nissan’sLeafisfarcheaper,withastickerpriceofabout$29,000.Butwithasmallerbatterypack,itsrangeisonlyaboutone-thirdthatoftheTesla.Improvingbatteriescouldmakeamajorimpact.Doublingabattery’senergydensitywouldenablecarcompaniestokeepthedrivingrangethesamewhilehalvingthesizeandcostofthebattery—orkeepthebatterysizeconstantanddoublethecar’srange.“Theageofelectricvehiclesiscoming,”Cuisays.ButinorderforEVstotakeover,“wehavetodobetter.”Herecognizedtheneedearlyinhiscareer.AfterfinishinghisundergraduatedegreeinhisnativeChinain1998,CuimovedfirsttoHarvardUniversityandthentotheUniversityofCalifornia(UC),Berkeley,tocompleteaPh.D.andpostdocinlabsthatwerepioneeringthesynthesisofnanosizedmaterials.Thoseweretheearlydaysofnanotechnology,whenresearcherswerestrugglingtogetafirmhandleonhowtocreatejustthematerialstheywanted,andtheworldofapplicationswasonlybeginningtotakeshape.WhileatUCBerkeley,Cuispe