《新能源技术与材料》第8讲电化学电容器介绍.pptx

电化学电容器及其电极材料的进展介绍

Whatiscapacitors?Whatiselectrochemicalcapacitors(supercapacitors)?电容器（Capacitor）是两金属板之间存在绝缘介质的一种电路元件。其单位为法拉，符号为F。电容器利用二个导体之间的电场来储存能量，二导体所带的电荷大小相等，但符号相反。当电性相反的电荷分别在电容器的两端累积，电容器两端的电位差和电荷产生的电场开始增加。累积电荷越多，为抵抗电场所需要作的功就越大。储存在电容器的能量（国际单位制中，单位为焦耳）等于建立电容两端的电压和电场所需要的能量。电化学电容器（supercapacitor）与上述电容器不同的地方是：两金属板之间存在绝缘介质变成了浸没在电解液中具有电化学活性的材料。基本原理相同，都是在电极处累积电荷达到能量存储的目的。Quetal.JournalofPowerSources,74(1998)99–107

油相与水相E=?CV2Aqueouselectrolytes,suchasacids(e.g.,H2SO4)andalkalis(e.g.,KOH)havetheadvantageofhighionicconductivity(upto～1?S?cm?1),lowcostandwideacceptance.Ontheotherhand,theyhavetheinherentdisadvantageofarestrictedvoltagerangewitharelativelylowdecompositionvoltageof～1.23?V.Non-aqueouselectrolytesofvarioustypeshavebeendevelopedthatallowtheuseofcelloperatingvoltages～2.5?V.Non-aqueouselectrolytemixturessuchaspropylenecarbonateoracetonitrile,containingdissolvedquaternaryalkylammoniumsalts,havebeenemployedinmanycommercialsupercapacitors,particularlythosetargetinghigherenergyapplications.Theelectricalresistivityofnon-ueouselectrolytesis,however,atleastanorderofmagnitudehigherthanthatofaqueouselectrolytesandthereforetheresultingcapacitorsgenerallyhaveahigherinternalresistance.

NatureMater.7,845-854(2008)Ifasupercapacitorisusedinanelectricvehicle,thespecificpowershowshowfastonecango,andthespecificenergyshowshowfaronecangoonasinglecharge.Timesshownarethetimeconstantsofthedevices,obtainedbydividingtheenergydensitybythepower.Electrochemicalcapacitorscurrentlyfillthegapbetweenbatteriesandconventionalsolidstateandelectrolyticcapacitors.能量比较图

特点Batteries:HighenergydensityandlowpowerdensityenergystoragesystemsElectrochemicalcapacitors:HighpowerdensityandlowenergydensitySolarenergyWindenergyWaterenergy……Advantagesof?Electrochemicalcapacitors(EC):High