Kvalue STUDY

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1、△OCV/KTestingMethodPreparedby:JamesZhuang11/1/2006AmperexTechnologyLimitedUnauthorizedreproductionprohibited11/4/2006Surpassingcustomer’sexpectationBackgroundAmperexTechnologyLimitedUnauthorizedreproductionprohibited11/4/2006Surpassingcustomer’sexpectationWhat’s△OCVOCV1OCVBt

2、1t2OCV1>OCVB+eiiRi+i-∑Self-dischargealwaysoccursforanycellandresultinOCVdropduringcellstorage∑CustomerrequiresOCVstableduringcellstorageAmperexTechnologyLimitedUnauthorizedreproductionprohibited11/4/2006Surpassingcustomer’sexpectationWhycellshave△OCV∑Reactionat¢1)Anode;2)Cat

3、hode;3)Electrolyte∑Internalshortcausebyelectricparticle¢1)electrodeparticle;2)metalparticle∑Internalshortcausebyelectrodecontact¢1)Design;2)Manufacture;3)externalforceAmperexTechnologyLimitedUnauthorizedreproductionprohibited11/4/2006Surpassingcustomer’sexpectationHowtocalcu

4、late△OCV∑AfterCharging,Standby12-24hrs∑MeasureOCV1∑Standby48-120hrs∑MeasureOCVB△OCV=OCV1-OCVBAmperexTechnologyLimitedUnauthorizedreproductionprohibited11/4/2006Surpassingcustomer’sexpectationStandbytimeeffectTimevsOCVdrop0.0120.010y=0.0004x+0.00020.0082R=0.99120.0060.004OCVd

5、rop(V)0.0020.000051015202530Time(days)AmperexTechnologyLimitedUnauthorizedreproductionprohibited11/4/2006Surpassingcustomer’sexpectationWhynotuse△OCVinprocessDifferentstoragetimeshouldberefertodifferentOCVdropcriteriaIt’sveryhardforonlineproductioncontrolHowtonormalizetheimp

6、actofstoragetimeandmake△OCVtestfeasible?Byapplying:K=△OCV/△TAmperexTechnologyLimitedUnauthorizedreproductionprohibited11/4/2006Surpassingcustomer’sexpectationWhat’sK∆OCVOCV1-OCVBOCVB-OCV1dVK===−=−∆tt−tt−tdtOCVBOCV1OCVBOCV1AmperexTechnologyLimitedUnauthorizedreproductionprohi

7、bited11/4/2006Surpassingcustomer’sexpectationWhat'sK:MeasureandrealvalueofKVoltage(Measurevalue)3.89Voltage(Realvalue)3.87Kvalue(Measurevalue)3.853.83_K(Realvalue)3.813.793.773.75t0t1t2t3t4t5t6t...t(n-2)t(n-1)tnLongerstandbytimebeforeOCV1,KÆKvaluerealTemperaturecoefficientof

8、OCVmeasurement:dV/dT<0AmperexTechnologyLimitedUnauthorizedreproductionprohi