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1、Li-ion-Battery-Li-ion-Battery-introductionintroduction锂离子电池锂离子电池介绍介绍CONTENTSIntroductionLi-ion Battery Fundamentals and Electrical BehaviorMonitoring and SafetyGeneral Battery Characteristics 21.2 Li-ion Battery Fundamentals and Electrical Behaviorn1.2.1 Battery Structuren1.2.2 Fundamentalsn1.2.3 Ma
2、terials and their influencesn1.2.3 Electrical behaviorn1.2.4 Equivalent circuit3Li-ion Battery StructurenCylindrical Li-ion Battery structureSeparator, cathode and anode are around the column.186504Li-ion Battery StructurenPrismatic Li-ion Battery Structure5Li-ion Battery StructurenCoin Li-ion Batte
3、ry structure6Li-ion Battery StructurenThin Film Li-ion Battery Structure10-100um thinkness. for microminiature device 7Li-ion Battery Structure8Li-ion Battery StructurenLi-ion Battery Structure:nAnode nCathodenSeparator nElectrolyte nEnclosure and packagecomponentmaterialexampleAnodeLi-embedded Tran
4、sition metal oxidesLiCoO4,LiMnO4,LiCoMnOx,LiFePO4CathodeLi-embeddable compound etc.(synthetic) graphiteElectrolyteLiPF6 alkyl acid estersEC,PC ,EDCSeparatorpolyene porous membranePE,PP,PP/PE/PPEnclosure and packagemetalsteel,aluminum9Li-ion Battery Performance requirements of anode materialsnhigh sp
5、ecific energynhigh specific powernlow self-discharge rationlow costnlong lifenhigh safety level10Capacity 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 wei
6、ght of LiCoO2 is 97.88 g/mol, (1g/97.88g/mol)*96500C/mol /3600s = 274 mAh/gLi-ion Battery Capacity Calculation for Anode11LiFePO4LiMnOxLiCoO2LiNiO2LiNiCoMnO2main componentLiFePO4LiMn2O4LiMnO2LiCoO2LiNiO2LiNiCoMnO2ennergy density (mAh/g)170 ideal148286274274278130-140 actual100-120200135-140190-21015
7、5-165voltage（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
8、 55Li-ion Battery anode materials and their peformances12LiCoO2LiMn2O4poor safety, high costSynthesis difficult serious attenuationLiNiO2Li-ion battery anode materials13Li-ion battery anode material developmentpower fieldcommunication fieldLiFePO4LiMn2O4Li-ternary compoundLiNiO2Ni-Hlead-acidLiCoO2po
9、wer 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 material14Li-ion battery Performance requirements of cathode materialsnLi+ can be embed and seperated rapidly.ngood revers
10、ibility of Li+ reaction with seldom crystal structure change.nweak electric potential change in the reaction process.ngood surface texture(Solid Electrolyte Interface Film, SEI) stability and compactednlarge diffusion coefficient for Li+ diffusion in cells, easy to charge quickly. 15cathode material
11、sungraphitisedungraphitisedcarboncarbongraphite graphite stratified structurestratified structureTransition metal oxidessilica-basedmaterialLi4Ti5O12spinel structuretin-basedmaterialmetal LiLi-ion battery Cathode materials16synthetic graphitesilicon carbon alloyLi-ion battery cathode materials perfo
12、rmancecathode materialscapacityprocess-abilitytemperature stabilitydisadvantagesgraphite carbon360mAh/geasygoodlow capacitySi alloy2500mAh/geasygoodvolume change Sn alloy800-900mAh/ghardbadbad porformance for high rate discahrgemetal Li3860mAh/geasybaddendritic crystal17carbon materials potential ri
13、sk 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 materialsL
14、i4Ti5O12Fig. Li4Ti5O12 SEM photo and its chg/dsg performanceLi-ion battery cathode materials18二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 cell
15、s. Li-ion battery electrode Voltage-Capacity distribution19Fig.2 electrolyte product manufacture processLi-ion battery electrolytenElectrolyte 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
16、 safety of the battery.nElectrolyte 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 product20nkeep liquid state in large temperatu
17、re range, high Li+ conductivity(10-2S/cm).ngood chemical and heat stability, hard to evaporation and reaction with others.nhigh protential up to 4.5V(vs.Li/Li+)。nnon-toxicneasy to prepare, low costLi-ion battery Performance requirements of electrolyte materials21nsafety, stability, compatibility wit
18、h cathode, conductivity, high dielectric constant, low viscosity.ncomposed 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.
19、90.65-55108-二甲醚DME7.20.46-58844.9solventLi-ion battery electrolyte solvent22Li-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 concentr
20、ationAl2O3, MgO,BaO, Li/CaxCOy23n1.liquid state, solution. high purity solvent, electrolyte(LiPF6), additive.n2.solid state, ploymer. polymer lithium ion battery, LIP.Li-ion battery electrolyteelectrolyte classifychemical formulafeatures高氯酸锂高氯酸锂LiClO4explosive四氟硼酸锂四氟硼酸锂LiBF4stability, poor conductiv
21、ity and cyclity六氟砷酸锂六氟砷酸锂LiAsF6effeciency, stability, but cost high and poisonous六氟磷酸锂六氟磷酸锂LiPF4good conductivity, poor thermal stability三氟甲基磺酰三氟甲基磺酰LiN(SO2CF3)good thermal stability and cyclity, but poor conductivity双草酸硼酸锂双草酸硼酸锂LiBOBgood thermal stability and chemical stability, but low solubility
22、and poor conductivity24play an improtant role in:nkeep anode and cathode separatenallow ion to pass through itself and charge to transferLi-ion battery separator25Li-ion battery separator performanceabilitypurposeperformanceposition separator, insulationanode and cathode particles isolation aviod sl
23、ef-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
24、 or the other.long storage lifeself-protectpores close when temperature risesafety26nporous ploymer thin film（PP,PE,PP/PE/PP）nmechanical property, wettablity, pore close temp point and fusing point conflictnnon-woven fabrics,Separion 无纺布型nhigh porosity nanofiber filmnSeparion thin filmnploymer elect
25、rolytensolid, gelLi-ion Battery Separator27Celgard2400 separator，PP，25m，37% porosity，0.117m*0.042m pore size Li-ion battery separator example28Li-ion Battery CharacteristicsnChemical Capacity and EnergynBattery ImpedancenUsable CapacitynPower CapabilitynCycle Life, Durability, Shelf LifenSelf-Discha
26、rge Properties29Li-ion Battery Chemical Capacity/EnergynQmax： Amount of charge can be extracted from the fully charged cell to the end of discharge voltage (EDV). Battery chemical capacity (no load)nIn Unit of:nAh/kg, Ah/l, Wh/kg, Wh/l n/l, /kg - protable equipments(phone, pad, etc.), ploymer Li-ion
27、 Batteryn 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 battery30Li-ion Battery Battery ImpedancenBattery Impedance：dV=I*R, after transient processnNyquist plot: Voltage responses on c
28、urrent of different frequencyA1:impedance, stretching real value of A2,3,5A5:0.51sA6:1000sRelaxation time31Li-ion battery Battery ImpedancenBattery Impedance：dV=I*R, after transient processnNyquist plot: Voltage responses on current of different frequencyA1:1000s.real sesistance stop increasing，IR d
29、rop constant，DC resistance.Relaxation time32nBattery Impedance：dV=I*R, after transient processnNyquist 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(D
30、C 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 circui
31、t refer to page 6 Fig.3.Li-ion battery Battery ImpedanceRelaxation time33nQusable: battery voltages. fully charged voltage, end of discharge voltage。nCell voltage depending on SOC and discharge current(IR drop).nIR drop observed take about 500s. (Nyquist plot 1000s)nIR drop:current，temperature，cycle
32、life，different from diffferent SOC.nNote: Do not estimate IR drop by resistance from cell makers. 1kHz vs DCnestimate 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
33、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 Capacity34nRagone Plot: Power Density(W/kg)-Energy Density(Wh/kg). /kg, /l, /m2nEnergy Density(Wh/kg): battery ennery fo
34、r battery one cycle usenPower Density(W/kg):battery power for battery proviod ennery every unit timeLi-ion battery Power Capability and Ragone Plot35ncell aged：chemical capacity loss and impedance increasenchemical capacity loss：nreason：crystal structure of active changeninflunce：high and low- rate
35、discharge applicationsnimpedance increase：nprimary reason：passivating layer grow and electrolyte lossninflunce：high-rate discharge application. deeper IR drop，usable capacity decrease。Li-ion battery Cycle Life36Li-ion Battery Cycle LifenAnalyze：nExperimental results-impedance increase influnce is mu
36、ch larger than that of capacity loss.n100cycle later，capcity loss5%，impedance increase60%.(DC resistance increased but not 1kHz resistance(almost constant), DC resistance is worthy of our attention)ninternal resistance：R=(V-OCV)/I37nShelf life depends on storage voltage(storage SOC) and storage temp
37、erature.nExperimental result：lead-acid battery benefit from high SOC storage, and Li-ion battery prefer low SOC storagenAged analyzed is similar to that of cycle life, current exsitance accelarate the aged and parastic reactionncurrent cause cracking of passivating layer,and the layer regrow will us
38、e up some active Li, the extra reaction particles will jam up pores to decrease the conductivity.ncurrent appear and disappear make the passivating layer expansion and shrinkage, the machanical change cause the electrical disconnect.nduring same time，cycle aged 510 times larger than storage.Li-ion B
39、attery Shelf Life(Storage Life)38Li-ion Battery Shelf Life(Storage Life)nIn the same temperature, the lower voltage, the lower battery capacity loss, the longer storage life of the battery.nUnder the same voltage condition, the lower temperature, the lower battery capacity loss, the longer storage l
40、ife of the battery.nUnder the same charge current condition, the lower charge voltage, the longer cycle life of the battery.39Li-ion battery Self-DischargenSelf-discharge Mechanism:nParasitic conductancenDendritic crystal grows in charge process, decreasing the suface of anode. nSaperator will be po
41、ked and cracked by more dendritic crystal, leading to electrode direct contect to each other. nPrecautions:nanoporous saparators have been used to reduce this effect.nshuttle moleculesnsome molecules can become oxidized on cathode, diffuse to anode, and become reduced there, and back to cathode. Sim
42、ilar effect of electron transfer.nPrecautions: avoid bringing in impurities in cell manufacture process.nutilize: under the high voltage conditon, the redox reaction of shuttle molecules can prevent over charge. 40Li-ion battery Self-DischargenSelf-discharge Mechanism:nRecombination of oxygen-hydrog
43、ennH2and 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.nRecombination of oxygen-hydrogen generates heat and becomes noticeable close to th
44、e end of charge.nOther redox reactions by impurities in electrolyte.41Li-ion battery Self-DischargenTemperature：the higher temperature, the higher self-discahrge ratenTemperature rise will accelerate all redox reactions.nAge：the more age, the higher self-discahrge ratenthe age, the more crack of act
45、ive materials, the higher surface area, the more matters of redox reactions.nNote: ncell structure designnThe 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(v
46、oltage) of the cell under the constant capacity.421.4 Monitoring and Safetyn1、safetynLi-ion battery safety problems need more anntention:nmore activity of Li, reaction with mounts of materialnhigh specific ennergy nConsequence:nThermal runaway(热逃逸，热失控热逃逸，热失控)：The temperature rise, the more additive
47、heat. thermal positive feedbacknbattery explode(expansion by heat or much more gas)nSources:nManufacture process. internal short circuit, metal particlesnAge process. cell imbalance, electrode imbalancenunreasonable operation, over discharge/charge. crystal structure change, dendritic crystal, inter
48、nal short circuit 431.4 Monitoring and Safetyn2、safety problem examplenexternal short circuit, external monitoring device and circuit prevention for safety.nInternal short circuit, Saperator may be poked and cracked by more dendritic crystal, leading to electrode direct contect to each other. manufa
49、cturing sector and external monitoring circuit prevention for safety.ngas expansion. Under high current and high temperature condition, electrolysis producing amount of gas. manufacturing sector and external monitoring circuit prevention for safety. Gas Safety ValvenThermal dilation, high current, s
50、ide effect. 自收缩隔膜自收缩隔膜nLi is deposited on anode, react with a variety of materials including electrolyte and cathode. More dangerious if air seep into and react with lithium, burning and explode.441.4 Monitoring and Safetyn3、PreventionnProper battery design and manifacture, Improve the monitoring st
51、andard of manufacturing process, additive materialsnRational use of batteries nExternal monitoring circuit in case of improper operations.nMore details on external monitoring circuit please refer to the following chapters.45基本结构基本结构ncathode: Pbnanode: PbO2nseparator: fiberglass, rubber, plastic,nacidproof, porous, strength, insulativitynelectrolyte: sulfate solution(gel)ncell groove: 36 cells for one groove, rutted on the bottom of it for caducous activities to prevent internal short.Thank You.49结束！结束！
