閥控式鉛酸蓄電池的失效模式在深放電電動自行車的應用外文文獻翻譯、中英文翻譯

閥控式鉛酸蓄電池的失效模式在深放電電動自行車的應用外文文獻翻譯、中英文翻譯,閥控式鉛酸,蓄電池,失效,模式,放電,電動自行車,應用,外文,文獻,翻譯,中英文 Journal of Power Sources 191(2009)127133Contents lists available at ScienceDirectJournal of Power Sourcesjournal homepage: modes of valve-regulated lead-acid batteries for electric bicycleapplications in deep dischargeYonglang Guoa,Shengqun Tanga,Gang Mengb,Shijun YangbaCollege of Chemistry and Chemical Engineering,Fuzhou University,Fuzhou 350108,PR ChinabHubei Camel Storage Battery Co.Ltd.,Gucheng 441705,PR Chinaa r t i c l ei n f oArticle history:Received 26 June 2008Received in revised form 20 August 2008Accepted 21 August 2008Available online 29 August 2008Keywords:Cycle lifeElectric bicycleFailure modesSofteningValve-regulated lead-acid batteriesa b s t r a c tThe 36 or 48V valve-regulated lead-acid(VRLA)battery packs have been widely applied to the powersources of electric bicycles or light electric scooters in China.The failure modes of the 12V/10Ah VRLAbatteries have been studied by the cycle life test at C2discharge rate and 100%depth of discharge(DOD).It indicates that the main cause of the battery failure in this cycle duty is the softening and shedding ofpositive active mass(PAM)rather than individual water loss,recombination efficiency or sulfation,etc.When the electrolyte saturation falls to a certain extent,the high oxygen recombination current leads tothe depolarization of the negative plate and the shift of the positive plate to a higher potential.The violentoxygen evolution accelerates the softening of PAM and the end of cycle life.2008 Elsevier B.V.All rights reserved.1.IntroductionIn the last two decades,much effort has been devoted to thestudy of valve-regulated lead-acid(VRLA)batteries in the applica-tions of electric vehicles(EV)and hybrid EVs 15.In China,thereis a population of more than 1.3 billion.Most people go to work bybicycle and 65.5 million bicycles were produced in 2007.In recentyears,however,more and more people use electric bicycles or lightelectric scooters to substitute for bicycles.These new vehicles havea 250 or 350W electromotor driven by a 36 or 48V VRLA batterypack,respectively 5,6.Based on the power of the electromotorused,thebatterycapacityis12V10,17or20Ah.Theheldamountofthe electric bicycles and light electric scooters at least reaches 60Mtill the end of last year.It corresponds to about 200M 12V/10AhVRLA batteries,or about RBM 26 billion.The practical operating lifeof batteries is normally in the range of 12 years.With the rapiddevelopment of Chinese or Asian economy,more electric bicyclesand their batteries will be needed and they have a huge potentialmarket in the coming years,which also promotes the developmentof EV.Although there are many failure modes of VRLA batteries,including premature capacity loss(PCL),grid corrosion,softening,Corresponding author.Tel.:+86 591 8789 2893;fax:+86 591 8807 3608.E-mail address:(Y.Guo).sulfation,drying out,additive decomposition and poor separator-plate contact,etc.,they vary with different designs,manufacturingand operating conditions 715.In the deep cycle duty,the inter-face of the grid/active mass easily accumulates the lead sulfatecrystals with very high resistance and forms a barrier layer whenPbSb alloys in the positive grid are substituted by PbCdSnAlalloys.It is called the“antimony-free effect”and the PCL-1 failuremode 7,8.Although the barrier layer can be obviously improvedwith the application of Sn content more than 1.2wt.%,it is sus-ceptible to the abuse conditions such as deep discharge.So mostmanufacturers in China use PbSbCd alloys as positive grid.How-ever,Cd is poisonous and must be excluded.The corrosion ofpositive grids in the cycle duty is not heavy as compared with thatin the float applications.The high contents of Ca and Al acceleratethecorrosionrateofpositivegridsgreatly,althoughtheyhavegoodmechanicalpropertiesandcastability.Theactivemass(AM)ofpos-itiveplatesundergoesgreatvolumeexpansionandshrinkageinthedeep cycle duty,which can lead to poor contact between AM par-ticles 8,9.This is the PCL-2 failure mode often taking place in theEV batteries.It can be greatly improved by compressing the platestack,optimizingthemanufacturetechnologyofpositiveplatesandincreasing the ratio of positive to negative AM.The serious sulfa-tion of negative plates often occurs when the battery operates atthe high rates in a partial-state-of-charge(HRPSoC)or has a highcurrent of oxygen recombination or when the additives at nega-tive plates are decomposed under the high temperature condition1,10,11.It will be overcome with the use of high content graphite0378-7753/$see front matter 2008 Elsevier B.V.All rights reserved.doi:10.1016/j.jpowsour.2008.08.059128Y.Guo et al./Journal of Power Sources 191(2009)127133in negative active mass(NAM)12.Drying out is mostly connectedwith a high charge voltage and current,often in combination withhigh battery temperature.In the extreme cases,thermal runawaymay take place for a battery with very low electrolyte saturation.Water loss depends on the grid compositions,impurities,batterytemperature and charge voltage 8.The suitable charge regimeincluding fast charge is very important for prolonging the batterycycle life 13.For the practice operating of electric bicycle batter-ies,their discharge current depends on the electromotor powerand the accelerating processes.The cutoff voltage is 10.5V.Theyare normally charged at a current-limited constant voltage(CCCV)(2A/14.8V)foronenight,twoorthreetimesperweek.Somecharg-ers also use the multi-step constant current charge.In the standardtest,however,the electric bicycle batteries are discharged at a 2hrate to 70%or 100%depth of discharge(DOD)and charged at thecurrent-limited constant voltage.Although the VRLA batteries have been widely used in electricbicycle,their cycle life and performance still need to be furtherimproved.Inthiswork,themanufacturetechnologiesof12V/10AhVRLA batteries were optimized and the failure modes in the deepcycle duty were investigated.2.ExperimentalThe test battery was 12V/10Ah(C2rate)VRLA batteries com-posedofsevenpositiveandeightnegativeplatesandtheabsorptiveglass mat(AGM)separator.The positive and negative gridswere Pb0.065%Ca1.2%Sn0.003%Al and Pb0.085%Ca0.35%Sn0.015%Al alloys,respectively.The positive and negative pastescontained 45 and 42g H2SO4per kg lead powder.Their apparentdensities were 4.34.4gcm3.It took 48h for their curing and dry-ing.Then the batteries were assembled and filled with 1.25gcm3H2SO4containing 1.5%Na2SO4.The container formation was con-ducted by the multi-step constant current charge regime with twodischarge steps within 70h.The battery weight was about 4.25kg.In the cycle test,the batteries were discharged at 5A(C2rate)to10.5V(100%DOD)and charged at a current-limited constant volt-age of 2.5A/14.4V for 6h,followed by charging at 0.8A for 1hagain at ambient temperature of about 25C.The specific energy ofthe battery reaches 32.6Whkg1.The cycling test was terminatedwhen the battery capacity fell to 7Ah(70%rate capacity).In orderto measure the battery internal resistance,a short current pulsewith 5A and 1ms was exerted by Arbin BT2000 instruments.Afterthe cycle life test,the batteries were torn down and analyzed.ThepowderX-raydiffraction(XRD)ofpositiveandnegativeactivemass(PAM and NAM)were carried out by a XPert Pro MPD Diffractome-ter(Philips).Theirappearancewasobservedbyascanningelectronmicroscope(SEM,Philips,XL30ESEM-TEP).3.Results and discussion3.1.Cycle testsFig.1 shows the dependence of the discharge capacity of twobatteries on cycle number at C2discharge rate.In the initial cycles,their capacity increases and reaches the maximum,11.55Ah,in the28thcycle.Thenitdecreasesgraduallybeforethe250thcycle.Afterthat,itbecomesrelativelystable,butitdropsquicklyafteraboutthe600th cycle.The cycle life of battery A and B is similar and reachesabout 680 cycles.Since in various failure modes,the grid corrosion,PAM soften-ing,drying out,sulfation or undercharge,etc.are closely relatedto the battery charge,the charge regime affects the cycle life of thetestbatteriesgreatly1618.Fig.2showsthechangesofthechargeFig.1.Evolution of discharge capacity of two batteries in the cycles at 100%DOD.current and battery voltage at the current-limited constant voltagein the cycle life test.In the first constant current stage(2.5A),theconstantcurrenttimeinFig.2Ashortenswiththecycles.Itisduetothe gradual falling of the battery capacity.The rising of the chargevoltage in Fig.2B indicates the increase of the battery polarizationresistance due to water loss and battery degeneration,etc.In thesecond constant voltage stage(14.4V),the charge current dropsFig.2.The changes of(A)charge current and(B)charge voltage at the current-limited constant voltage in different cycles.Y.Guo et al./Journal of Power Sources 191(2009)127133129Fig.3.Evolutions of charge current at 6h and charge voltage at 7h in Fig.2.quickly and reaches very small value.However,the tail current at6h begins to increase obviously after about the 400th cycle andits detail evolution is shown in Fig.3.At the final stage of chargeat 0.8A,Fig.2B shows that the charge voltage at first increases andthendecreasesasthecycletestproceeds.Theturningpointappearsaboutinthe50thcycleandthechargevoltagereaches16.68V.Thenthe maximum charge voltage decreases gradually with the elec-trolyte consumption or the decrease of the electrolyte saturation,which leads to the depolarization of the negative plate.After the570th cycle,the maximum charge voltage is lower than 14.40V.Itmeans that such low polarization may result in the underchargeand the accumulation of PbSO4at the negative plate.Fig.3 shows dependence of the charge current at the end ofconstant voltage(6h)in Fig.2A and the voltage at the end of con-stant current(7h)in Fig.2B on the cycle number.In practice,thischarge current responses to the rate of oxygen recombination orcharge efficiency and the charge voltage responses to the polar-ization or effective charge.It is found from Fig.3 that the batterycharge voltage is very high and the charge current increases from0.12 to 0.39A in the initial 50 cycles.It indicates that the batteryhas high electrolyte saturation and very low oxygen recombinationcurrent in this period.Then the charge voltage drops very quicklyand is stabilized in the range of 14.615.0V till the 400th cycle,Fig.4.The changes of the battery internal resistance at the end of charge and dis-charge in the cycles.Fig.5.The changes of voltage and current when the three failed cells were chargedbefore and after adding water.Fig.6.The voltage falling of three cells during the shelf after adding water and afew cycles.Fig.7.The changes of the internal resistance in the charge and discharge of threecells before and after adding water.130Y.Guo et al./Journal of Power Sources 191(2009)127133Fig.8.The photographs of the plate stack and its positive and negative plates of failed battery A.and the charge current lies in the range of 0.2110.388A.This is arelatively ideal cycle process,in which the relatively high voltagenot only ensures the full charge and but also no more water lossoccurs.After that,especially the 600th cycle later,the charge cur-rent at constant voltage stage increases rapidly while the chargevoltage decrease gradually from 14.68 to 14.09V.In this stage,theelectrolyte saturation only decreases by 1.2%(from 88.2%to 87.0%)in about 250 cycles.Kirchev and Pavlov 19 found that the liquidfilm thickness on the surface of NAM and oxygen recombinationrate change sharply when the electrolyte saturation is lower thanabout 87%.At this time,therefore,only a little decrease of the elec-trolyte saturation will result in very high oxygen recombinationcurrent and the depolarization of the negative plate.And the bat-tery undercharge may occur.It also indicates that the battery isdifficult to be fully charged at 14.6V for 7h charge time,which willlead to the obvious degradation of the batteries in the subsequentcycles.The battery internal resistance is related to the battery struc-ture,electrolyte saturation,grid corrosion,contact between PAMparticles,passivation,AM sulfation and reaction area,etc.Since theinternal resistance is small for a new or normally operating bat-tery,the changes of the battery internal resistance at the end ofcharge and discharge were measured only in the later half of cyclelife test and shown in Fig.4.The discharge resistance is about fourFig.9.The torn-down AGM separator from the failed battery.Y.Guo et al./Journal of Power Sources 191(2009)127133131times the charge resistance.And their resistance increases greatlyafter the 550th cycle,especially the final 20 cycles.Apparently,thebattery failure is closely related to the rapid rising of the internalresistance.It can be seen from Fig.3 that the oxygen recombina-tion current goes up sharply in the period.This further leads to thedepolarizationofthenegativeplate,theshiftofthepositiveplatetohigher potential and more violent evolution of oxygen.As a result,the contact between PAM particles becomes poor and the resis-tance increases rapidly,which can accelerate the battery capacityfalling and the end of the cycle life.3.2.Overcharge and adding water testsThe C2capacity of battery A was only 6.03Ah after 700 cycles.In order to analyze the causes of the battery failure,the batterywas divided into two 6V batteries(three cells)after the end ofthe cycle life.They went through the overcharge,adding water andresistance measurements.Since the charge current at the constantvoltage of 14.4V has reached 1.8A in the 670th cycle in Fig.2A,thesubsequent constant charge of 0.8A cannot make the battery fullycharged.To see whether the battery is undercharged,the final 0.8A1h charge was changed into 2A 2h charge and two cycles wereperformed.The first charge amount is 2.53 times the previous dis-charge capacity,but the next discharge capacity is only 6.45Ah andhas the comeback of only 7%capacity.In order to know whetherthe battery failure is due to excessive water loss,each cell wasfilled with about 18ml water after the battery was fully charged.The second C2capacity is only 5.58Ah,less than the first capacity.It indicates that the water loss and undercharge are not the majorcauses of the battery failure.Fig.5showsthechangesofthechargecurrentandvoltagebeforeandafteraddingwatermentionedabove.Beforeaddingwater,theircurves are normal.But after adding water,the maximum chargevoltage only reaches 2.349V per cell so that the charge currentalways keeps the limited value of 2.5A.Based on the charge volt-age at 2.5A for a flood lead-acid battery,it can be presumed thatthe internal short circuit takes place in the battery.Fig.6 showsthe voltage decline of the fully charged battery during its shelf.Itscapacity was completely self-discharged within 20h.The H2SO4solution after charging shows a little black color,instead of beingtransparent.It indicates that severe softening occurs at the posi-tive plate.A lot of PAM particles shed and enter into the electrolyteat high charge current.These PbO2particles can be precipitated atFig.10.The capacity comeback of the negative plate of the failed battery in thecycles.the negative plate as dendritic lead which passes through the AGMseparator to form the tiny short circuit.Fig.7 shows the changes of the internal resistance in the chargeanddischargeofthethreefailedcellsbeforeandafteraddingwater.During charging,the internal resistance decreases gradually andtwo curves are the same.During discharging,the internal resis-tance increases sharply at the end and it is greatly affected byadding water.The battery capacity decreases from 7.50 to 5.83Ah.So similar to the results above,the battery failure is not caused bywater loss.On the contrary,the addition of water hinders the oxy-genescapefromthemicroporesinPAMduringovercharging,whichcan increase the internal pressure in PAM and may cause its shed-ding.Afteranotherthreecycles,thechargevoltageofthethreecellsFig.11.SEM of active mass in different parts of positive plate of the failed battery.(A)500,(B)10,000 and(C)1000.132Y.Guo et al./Journal of Power Sources 191(2009)127133only reaches 6.72V at the constant current of 2.5A.So the internalshort circuit can also take place.3.3.Teardown analysisBatteryAwastorndownafterthecyclelifetestwasended.Fig.8shows the photographs of the plate stack and its positive and neg-ative plates.The plate stack and negative plate had the integratedstructures.Although some ribs of the positive grid were severelycorroded,its frame was still well and the positive plate had rel-atively good mechanical property.It is found,however,that thesevere softening appears in PAM,especially in the upper part of thepositive plate.Fig.9 indicates that the AGM separator facing posi-tive plate glues a lot of PAM particles and that the AGM separatorfacing negative plate is normal.This is due to the fact that the PAMparticles become increasingly small with the cycles and their con-tact among one another becomes poor,resulting in the softeningand shedding.In order to know whether the negative plate fails,one negativeplate of the failed battery was placed between two normal positiveplates,separated by PE separator,and they were put into excessiveH2SO4solution of 1.28 specific gravity.And then the cell was cycledaccording to the conditions of the cycle life test.That is,charge at0.36A2.4Vfor6handatconstantcurrentof0.114Aforanother1h,then discharge to the negative potential of 0.8V(vs.Hg2SO4/Hg)at 0.7A.Fig.10 shows the capacity comeback of the negative platein the cycles.The very low capacity in the first discharge is becausethe negative plate was in a discharge state when the battery wastorn down.It is found that the capacity of the negative plate canFig.12.SEM of active mass in(A)the upper and(B)lower parts of negative plate ofthe failed battery.(A)2000 and(B)e back easily in several cycles.Therefore,the battery failure isnot due to the sulfation or passivation of the negative plate.The SEM of the fully charged PAM of failure battery A are shownin Fig.11.Fig.11A shows the typical coralloid structure of PAM.Thesize of big pores is in the range of 1020?m.There are also a lotof micropores on the framework.Fig.11B is an enlarged Fig.11A,which indicates that size of the PAM particles is 0.30.5?m andtheir contact among one another is very poor.The PAM has a highcrystallinity and has lost its hydrated structure,which is unfavor-abletothebatterycapacityanditscyclelife.Fig.11CshowstheSEMof PAM in the other position.There are some particles with poorcrystallinityorhydratedstructureandsomelargecrystalswithhighcrystallinity and 78?m in size,which are PbSO4crystals.There-fore,the PAM has two structures.One is the accumulation of somePbSO4crystals.The other is the coralloid structure with poor con-tactamongAMparticles.ThePAMhassoftenedandshedobviously.Fig.12 shows the SEM of the fully charged NAM in the upperand lower parts of the negative plate.It can be seen that there aretwo structures.They are PbSO4and Pb crystals.The former are per-fect crystals and the latter have a spongy or dendritic structure.Although the NAM is fully charged,the oxygen recombination atthe negative plates causes the PbSO4accumulation.It is found thatthe PbSO4crystals in the upper part of the negative plate are a littlelarger as compared with those in the lower part.This is due to thecontinual cycle test in which more AM is charged and dischargedin the lower part when the electrolyte stratification occurs.In theupper part,on the other hand,more oxygen recombination takesplace,in which bigger PbSO4crystals can be formed by electro-chemical and chemical reaction processes 20.For the practicalVRLA batteries with electrolyte stratification,however,the sulfa-Fig.13.The XRD patterns of(A)PAM and(B)NAM of the failed battery.Y.Guo et al./Journal of Power Sources 191(2009)127133133tionorbigPbSO4crystalsnormallyappearinthelowerpartbecauseof its self-discharge 21.Therefore,this test battery only has verylight electrolyte stratification due to its small plates.It is well known that