LiionBatteryintroduction锂离子电池介绍.pptx

CONTENTSIntroductionLi-ion Battery Fundamentals and Electrical BehaviorMonitoring and SafetyGeneral Battery Characteristics Page 1第1页/共49页1.2 Li-ion Battery Fundamentals and Electrical Behavior1.2.1 Battery Structure1.2.2 Fundamentals1.2.3 Materials and their influences1.2.3 Electrical behavior1.2.4 Equivalent circuitPage 2第2页/共49页Li-ion Battery StructureCylindrical Li-ion Battery structureSeparator,cathode and anode are around the column.Page 318650第3页/共49页Li-ion Battery StructurePrismatic Li-ion Battery StructurePage 4第4页/共49页Li-ion Battery StructureCoin Li-ion Battery structurePage 5第5页/共49页Li-ion Battery StructureThin Film Li-ion Battery Structure10-100um thinkness.for microminiature device Page 6第6页/共49页Li-ion Battery StructurePage 7第7页/共49页Li-ion Battery StructureLi-ion Battery Structure:Anode CathodeSeparator Electrolyte Enclosure and packagecomponentmaterialexampleAnodeLi-embedded Transition metal oxidesLiCoO4,LiMnO4,LiCoMnOx,LiFePO4CathodeLi-embeddable compound etc.(synthetic)graphiteElectrolyteLiPF6 alkyl acid estersEC,PC,EDCSeparatorpolyene porous membranePE,PP,PP/PE/PPEnclosure and packagemetalsteel,aluminumPage 8第8页/共49页Li-ion Battery Performance requirements of anode materialshigh specific energyhigh specific powerlow self-discharge ratiolow costlong lifehigh safety levelPage 9第9页/共49页Capacity Calculation：1mol Li+,Q=96500C（F=NA*e=96500C/mol）1C=1AsTake LiFePO4 for example:The formula weight of LiFePO4 is 157.756 g/mol,(1g/157.756g/mol)*96500C/mol/3600s=170 mAh/gThe formula weight of LiCoO2 is 97.88 g/mol,(1g/97.88g/mol)*96500C/mol/3600s=274 mAh/gLi-ion Battery Capacity Calculation for AnodePage 10第10页/共49页LiFePO4LiMnOxLiCoO2LiNiO2LiNiCoMnO2main componentLiFePO4LiMn2O4LiMnO2LiCoO2LiNiO2LiNiCoMnO2ennergy density(mAh/g)170 ideal148286274274278130-140 actual100-120200135-140190-210155-165voltage（V）3.2-3.73.8-3.93.4-4.33.62.5-4.13.0-4.5cycle life2000500inferior300inferior800transition metalvery richrichrichpoorrichpoorenvironmantalnon-poisonousnon-poisonousnon-poisonousradioactivity(Co)poisonous(Ni)poisonoussafetygreatgoodgoodbadbadnot badtemp()-207550low temp stable-20 55N/A-20 55Li-ion Battery anode materials and their peformancesPage 11第11页/共49页LiCoO2LiMn2O4poor safety,high costSynthesis difficult serious attenuationLiNiO2Li-ion battery anode materialsPage 12第12页/共49页Li-ion battery anode material developmentpower fieldcommunication fieldLiFePO4LiMn2O4Li-ternary compoundLiNiO2Ni-Hlead-acidLiCoO2power field:LiFePO4 and LiMn2O4 have the advantages of low cost,safety and heat minocation field:Li-ternary compound and LiNiO2 have higher specific energy.Li-ion battery anode materialPage 13第13页/共49页Li-ion battery Performance requirements of cathode materialsLi+can be embed and seperated rapidly.good reversibility of Li+reaction with seldom crystal structure change.weak electric potential change in the reaction process.good surface texture(Solid Electrolyte Interface Film,SEI)stability and compactedlarge diffusion coefficient for Li+diffusion in cells,easy to charge quickly.Page 14第14页/共49页cathode materialsungraphitisedungraphitisedcarboncarbongraphite graphite stratified structurestratified structureTransition metal oxidessilica-basedmaterialLi4Ti5O12spinel structuretin-basedmaterialmetal LiLi-ion battery Cathode materialsPage 15第15页/共49页synthetic graphitesilicon carbon alloyLi-ion battery cathode materials performancecathode materialscapacityprocess-abilitytemperature stabilitydisadvantagesgraphite carbon360mAh/geasygoodlow capacitySi alloy2500mAh/geasygoodvolume change Sn alloy800-900mAh/ghardbadbad porformance for high rate discahrgemetal Li3860mAh/geasybaddendritic crystalPage 16第16页/共49页carbon materials potential risk Li4Ti5O12large mount of capacity,less expension,long cycle life and storage life,surpport quick charge.etc.Metal lithium is deposited on the carbon surface.It can explosively react with a variety of materials.Burning,explode and gas expansion are all protential safety problems.carbon materialsLi4Ti5O12Fig.Li4Ti5O12 SEM photo and its chg/dsg performanceLi-ion battery cathode materialsPage 17第17页/共49页二次锂电池正负极材料电压二次锂电池正负极材料电压-容量分布图容量分布图Voltage versus capacity for positive-and negative-electrode materials presently used or under serious considerations for the next generation of rechargeable Li-based cells.Li-ion battery electrode Voltage-Capacity distributionPage 18第18页/共49页Fig.2 electrolyte product manufacture processLi-ion battery electrolyteElectrolyte is one of four major part of the Li-ion battery,which plays an important role in Li+transfer and has an effect on Capacity,work temperature range cycle and safety of the battery.Electrolyte is usually 15%of the total weight and 32%of total volume,and its purity is worth attention in the manufacturing process.raw-materialsolvent-preparepurificationfine purificationelectrolytesolution preparestirfinished productPage 19第19页/共49页keep liquid state in large temperature range,high Li+conductivity(10-2S/cm).good chemical and heat stability,hard to evaporation and reaction with others.high protential up to 4.5V(vs.Li/Li+)。non-toxiceasy to prepare,low costLi-ion battery Performance requirements of electrolyte materialsPage 20第20页/共49页safety,stability,compatibility with cathode,conductivity,high dielectric constant,low posed by solvent and additive中文名称short namedielectric constantviscosity(mPas)melting point()boiling point()decomposition voltage(V)乙烯碳酸酯EC901.9372385.8丙烯碳酸酯PC652.5-492425.8二甲基碳酸酯DMC3.10.593905.7二乙基碳酸酯DEC2.80.75-431275.5乙基甲基碳酸酯EMC2.90.65-55108-二甲醚DME7.20.46-58844.9solventLi-ion battery electrolyte solventPage 21第21页/共49页Li-ion battery electrolyte additiveAdditive NameApplicationComponent亚乙烯碳酸酯improve SEI film performanceSO2/Co2/VC磷酸三甲酯improve eletrolyte safetyTMP冠醚和穴状化合物improve electrolyte conductivityether,etc.金属氧化物和盐balance acid concentrationAl2O3,MgO,BaO,Li/CaxCOyPage 22第22页/共49页1.liquid state,solution.high purity solvent,electrolyte(LiPF6),additive.2.solid state,ploymer.polymer lithium ion battery,LIP.Li-ion battery electrolytePage 23electrolyte classifychemical formulafeatures高氯酸锂LiClO4explosive四氟硼酸锂LiBF4stability,poor conductivity and cyclity六氟砷酸锂LiAsF6effeciency,stability,but cost high and poisonous六氟磷酸锂LiPF4good conductivity,poor thermal stability三氟甲基磺酰LiN(SO2CF3)good thermal stability and cyclity,but poor conductivity双草酸硼酸锂LiBOBgood thermal stability and chemical stability,but low solubility and poor conductivity第23页/共49页play an improtant role in:keep anode and cathode separateallow ion to pass through itself and charge to transferLi-ion battery separatorPage 24第24页/共49页Li-ion battery separator performanceabilitypurposeperformanceposition separator,insulationanode and cathode particles isolation aviod slef-discharging,internal short circuitporinessLi-ion transferhigh conductivity,low internal impendancechemical stabilityno reaction and consumptionlong storage lifeelectrolyte wettabilityfully contactedion conductivitylong cycle lifemechanical propertyin case of crack by force from dendritic crystal or the other.long storage lifeself-protectpores close when temperature risesafetyPage 25第25页/共49页porous ploymer thin film（PP,PE,PP/PE/PP）mechanical property,wettablity,pore close temp point and fusing point conflictnon-woven fabrics,Separion 无纺布型high porosity nanofiber filmSeparion thin filmploymer electrolytesolid,gelLi-ion Battery SeparatorPage 26第26页/共49页Celgard2400 separator，PP，25m，37%porosity，0.117m*0.042m pore size Li-ion battery separator examplePage 27第27页/共49页Li-ion Battery CharacteristicsChemical Capacity and EnergyBattery ImpedanceUsable CapacityPower CapabilityCycle Life,Durability,Shelf LifeSelf-Discharge PropertiesPage 28第28页/共49页Li-ion Battery Chemical Capacity/EnergyQmax：Amount of charge can be extracted from the fully charged cell to the end of discharge voltage(EDV).Battery chemical capacity(no load)In Unit of:Ah/kg,Ah/l,Wh/kg,Wh/l/l,/kg-protable equipments(phone,pad,etc.),ploymer Li-ion Battery Ah,Wh-comparing different battery with same chemical materials in Ah,but Wh for different chemical battery.Fig.x Voltage profile during low-rate discharge of batteryPage 29第29页/共49页Li-ion Battery Battery ImpedanceBattery Impedance：dV=I*R,after transient processNyquist plot:Voltage responses on current of different frequencyA1:impedance,stretching real value of A2,3,5A5:0.51sA6:1000sRelaxation timePage 30第30页/共49页Li-ion battery Battery ImpedanceBattery Impedance：dV=I*R,after transient processNyquist plot:Voltage responses on current of different frequencyA1:1000s.real sesistance stop increasing，IR drop constant，DC resistance.Relaxation timePage 31第31页/共49页Battery Impedance：dV=I*R,after transient processNyquist plot:Voltage responses on current of different frequency40m 6070m 100m A1 A2 A3 A4 A5 A6 1000sNOTE：Cell makers often report cell impendance at 1kHz,its not real cell resistance.real resistance(DC resistance)is 2.7 times larger than that at 1kHz.Relaxation time increasing，real resistance keep constant but imaginary increacing,as if serially connected capacitor and capatance is huge.note that cell impedance varies from SOC,resulting from active particals and ions changes.Equivalent circuit refer to page 6 Fig.3.Li-ion battery Battery ImpedanceRelaxation timePage 32第32页/共49页Qusable:battery voltages.fully charged voltage,end of discharge voltage。Cell voltage depending on SOC and discharge current(IR drop).IR drop observed take about 500s.(Nyquist plot 1000s)IR drop:current，temperature，cyclelife，different from diffferent SOC.Note:Do not estimate IR drop by resistance from cell makers.1kHz vs DCestimate usable capacity in real discharge process in thermal box,heat exchange,much more close to real usable capacitywhy not test cell temperature directly？self-heating of cell and,more important,electronic devices result in enviroment temperature around the cells rising,abundant heat exchange(put in thermal box)is nessanary for monitoring.Li-ion battery Usable CapacityPage 33第33页/共49页Ragone Plot:Power Density(W/kg)-Energy Density(Wh/kg)./kg,/l,/m2Energy Density(Wh/kg):battery ennery for battery one cycle usePower Density(W/kg):battery power for battery proviod ennery every unit timeLi-ion battery Power Capability and Ragone PlotPage 34第34页/共49页cell aged：chemical capacity loss and impedance increasechemical capacity loss：reason：crystal structure of active changeinflunce：high and low-rate discharge applicationsimpedance increase：primary reason：passivating layer grow and electrolyte lossinflunce：high-rate discharge application.deeper IR drop，usable capacity decrease。Li-ion battery Cycle LifePage 35第35页/共49页Li-ion Battery Cycle LifeAnalyze：Experimental results-impedance increase influnce is much larger than that of capacity loss.100cycle later，capcity loss5%，impedance increase60%.(DC resistance increased but not 1kHz resistance(almost constant),DC resistance is worthy of our attention)internal resistance：R=(V-OCV)/IPage 36第36页/共49页Shelf life depends on storage voltage(storage SOC)and storage temperature.Experimental result：lead-acid battery benefit from high SOC storage,and Li-ion battery prefer low SOC storageAged analyzed is similar to that of cycle life,current exsitance accelarate the aged and parastic reactioncurrent cause cracking of passivating layer,and the layer regrow will use up some active Li,the extra reaction particles will jam up pores to decrease the conductivity.current appear and disappear make the passivating layer expansion and shrinkage,the machanical change cause the electrical disconnect.during same time，cycle aged 510 times larger than storage.Li-ion Battery Shelf Life(Storage Life)Page 37第37页/共49页Li-ion Battery Shelf Life(Storage Life)In the same temperature,the lower voltage,the lower battery capacity loss,the longer storage life of the battery.Under the same voltage condition,the lower temperature,the lower battery capacity loss,the longer storage life of the battery.Under the same charge current condition,the lower charge voltage,the longer cycle life of the battery.Page 38第38页/共49页Li-ion battery Self-DischargeSelf-discharge Mechanism:Parasitic conductanceDendritic crystal grows in charge process,decreasing the suface of anode.Saperator will be poked and cracked by more dendritic crystal,leading to electrode direct contect to each other.Precautions:nanoporous saparators have been used to reduce this effect.shuttle moleculessome molecules can become oxidized on cathode,diffuse to anode,and become reduced there,and back to cathode.Similar effect of electron transfer.Precautions:avoid bringing in impurities in cell manufacture process.utilize:under the high voltage conditon,the redox reaction of shuttle molecules can prevent over charge.Page 39第39页/共49页Li-ion battery Self-DischargeSelf-discharge Mechanism:Recombination of oxygen-hydrogenH2and O2generate by electrolysis of water,gasses then diffuse through the separator and react since saparators are not airtight.Another redox reaction generate which is similar to the effect of electron transfer.Recombination of oxygen-hydrogen generates heat and becomes noticeable close to the end of charge.Other redox reactions by impurities in electrolyte.Page 40第40页/共49页Li-ion battery Self-DischargeTemperature：the higher temperature,the higher self-discahrge rateTemperature rise will accelerate all redox reactions.Age：the more age,the higher self-discahrge ratethe age,the more crack of active materials,the higher surface area,the more matters of redox reactions.Note:cell structure designThe reactions between electrolyte and electrode always exsit in the process of self-discharge,which makes poor the material activity and changes its structure,leading to decrease the ennergy(voltage)of the cell under the constant capacity.Page 41第41页/共49页1.4 Monitoring and Safety1、safetyLi-ion battery safety problems need more anntention:more activity of Li,reaction with mounts of materialhigh specific ennergy Consequence:Thermal runaway(热逃逸，热失控)：The temperature rise,the more additive heat.thermal positive feedbackbattery explode(expansion by heat or much more gas)Sources:Manufacture process.internal short circuit,metal particlesAge process.cell imbalance,electrode imbalanceunreasonable operation,over discharge/charge.crystal structure change,dendritic crystal,internal short circuit Page 42第42页/共49页1.4 Monitoring and Safety2、safety problem exampleexternal short circuit,external monitoring device and circuit prevention for safety.Internal short circuit,Saperator may be poked and cracked by more dendritic crystal,leading to electrode direct contect to each other.manufacturing sector and external monitoring circuit prevention for safety.gas expansion.Under high current and high temperature condition,electrolysis producing amount of gas.manufacturing sector and external monitoring circuit prevention for safety.Gas Safety ValveThermal dilation,high current,side effect.自收缩隔膜Li is deposited on anode,react with a variety of materials including electrolyte and cathode.More dangerious if air seep into and r