1、battrey chemistry fundamentals and characteristics,sinowealth bp wxl,page 2,contents,introduction,01,li-ion battery fundamentals and electrical behavior,02,monitoring and safety,04,general battery characteristics,03,page 3,1.2 li-ion battery fundamentals and electrical behavior,1.2.1 battery structu

2、re 1.2.2 fundamentals 1.2.3 materials and their influences 1.2.3 electrical behavior 1.2.4 equivalent circuit,page 4,li-ion battery structure,cylindrical li-ion battery structure,separator, cathode and anode are around the column.,18650,page 5,li-ion battery structure,prismatic li-ion battery struct

3、ure,page 6,li-ion battery structure,coin li-ion battery structure,page 7,li-ion battery structure,thin film li-ion battery structure,10-100um thinkness. for microminiature device,page 8,li-ion battery structure,page 9,li-ion battery structure,li-ion battery structure: anode cathode separator electro

4、lyte enclosure and package,page 10,li-ion battery performance requirements of anode materials,high specific energy high specific power low self-discharge ratio low cost long life high safety level,page 11,capacity calculation： 1mol li+ ,q=96500c（f=na*e=96500c/mol ） 1c = 1as take lifepo4 for example:

5、 the formula weight of lifepo4 is 157.756 g/mol, (1g/157.756g/mol)*96500c/mol /3600s = 170 mah/g the formula weight of licoo2 is 97.88 g/mol, (1g/97.88g/mol)*96500c/mol /3600s = 274 mah/g,li-ion battery capacity calculation for anode,page 12,li-ion battery anode materials and their peformances,page

6、13,licoo2,limn2o4,poor safety, high cost,synthesis difficult,serious attenuation,linio2,li-ion battery anode materials,page 14,li-ion battery anode material development,power field,communication field,lifepo4 limn2o4,li-ternary compound linio2,ni-h,lead-acid,licoo2,power field: lifepo4 and limn2o4 h

7、ave the advantages of low cost, safety and heat stablity. comminocation field: li-ternary compound and linio2 have higher specific energy.,li-ion battery anode material,page 15,li-ion battery performance requirements of cathode materials,li+ can be embed and seperated rapidly. good reversibility of

8、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 compacted large diffusion coefficient for li+ diffusion in cells, easy to charge quickly.,page 16,li-ion battery cathod

9、e materials,page 17,synthetic graphite,silicon carbon alloy,li-ion battery cathode materials performance,page 18,carbon materials potential risk li4ti5o12,large mount of capacity,less expension,long cycle life and storage life,surpport quick charge.etc.,metal lithium is deposited on the carbon surfa

10、ce.it can explosively react with a variety of materials. burning, explode and gas expansion are all protential safety problems.,carbon materials,li4ti5o12,fig. li4ti5o12 sem photo and its chg/dsg performance,li-ion battery cathode materials,page 19,二次鋰電池正負極材料電壓-容量分布圖 voltage versus capacity for posi

11、tive- 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 distribution,page 20,fig.2 electrolyte product manufacture process,li-ion battery electrolyte,electrolyte is one of

12、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 pro

13、cess.,page 21,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-toxic easy to prepare, low cost,li-ion battery performance requirements of electroly

14、te materials,page 22,safety, stability, compatibility with cathode, conductivity, high dielectric constant, low viscosity. composed by solvent and additive,solvent,li-ion battery electrolyte solvent,page 23,li-ion battery electrolyte additive,page 24,1.liquid state, solution. high purity solvent, el

15、ectrolyte(lipf6), additive. 2.solid state, ploymer. polymer lithium ion battery, lip.,li-ion battery electrolyte,page 25,play an improtant role in: keep anode and cathode separate allow ion to pass through itself and charge to transfer,li-ion battery separator,page 26,li-ion battery separator perfor

16、mance,page 27,porous ploymer thin film（pp,pe,pp/pe/pp） mechanical property, wettablity, pore close temp point and fusing point conflict non-woven fabrics,separion 無紡布型 high porosity nanofiber film separion thin film ploymer electrolyte solid, gel,li-ion battery separator,page 28,celgard2400 separato

17、r，pp，25m，37% porosity，0.117m*0.042m pore size,li-ion battery separator example,page 29,li-ion battery characteristics,chemical capacity and energy battery impedance usable capacity power capability cycle life, durability, shelf life self-discharge properties,page 30,li-ion battery chemical capacity/

18、energy,qmax： 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

19、same chemical materials in ah, but wh for different chemical battery.,fig. x voltage profile during low-rate discharge of battery,page 31,li-ion battery battery impedance,battery impedance：dv=i*r, after transient process nyquist plot: voltage responses on current of different frequency a1:impedance,

20、 stretching real value of a2,3,5 a5:0.51s a6:1000s,relaxation time,page 32,li-ion battery battery impedance,battery impedance：dv=i*r, after transient process nyquist plot: voltage responses on current of different frequency a1:1000s.real sesistance stop increasing， ir drop constant，dc resistance.,re

21、laxation time,page 33,battery impedance：dv=i*r, after transient process nyquist plot: voltage responses on current of different frequency 40m 6070m 100m a1 a2 a3 a4 a5 a6 1000s note： cell makers often report cell impendance at 1khz, its not real cell resistance. real resistance(dc resistance) is 2.7

22、 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

23、 fig.3.,li-ion battery battery impedance,page 34,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 difff

24、erent soc. note: do not estimate ir drop by resistance from cell makers. 1khz vs dc estimate usable capacity in real discharge process in thermal box, heat exchange, much more close to real usable capacity why not test cell temperature directly？ self-heating of cell and, more important, electronic d

25、evices result in enviroment temperature around the cells rising, abundant heat exchange(put in thermal box) is nessanary for monitoring.,li-ion battery usable capacity,page 35,ragone plot: power density(w/kg)-energy density(wh/kg). /kg, /l, /m2 energy density(wh/kg): battery ennery for battery one c

26、ycle use power density(w/kg):battery power for battery proviod ennery every unit time,li-ion battery power capability and ragone plot,page 36,cell aged：chemical capacity loss and impedance increase chemical capacity loss： reason：crystal structure of active change influnce：high and low- rate discharg

27、e applications impedance increase： primary reason：passivating layer grow and electrolyte loss influnce：high-rate discharge application. deeper ir drop，usable capacity decrease。,li-ion battery cycle life,page 37,li-ion battery cycle life,analyze： experimental results-impedance increase influnce is mu

28、ch 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)/i,page 38,shelf life depends on storage voltage(storage soc) and storag

29、e temperature. experimental result：lead-acid battery benefit from high soc storage, and li-ion battery prefer low soc storage aged analyzed is similar to that of cycle life, current exsitance accelarate the aged and parastic reaction current cause cracking of passivating layer,and the layer regrow w

30、ill 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.,l

31、i-ion battery shelf life(storage life),page 39,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 lo

32、nger storage life of the battery. under the same charge current condition, the lower charge voltage, the longer cycle life of the battery.,page 40,li-ion battery self-discharge,self-discharge mechanism: parasitic conductance dendritic crystal grows in charge process, decreasing the suface of anode.

33、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 molecules some molecules can become oxidized on cathode, diffuse to anode, and become reduced there, and b

34、ack 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 41,li-ion battery self-discharge,self-discharge mechanism: recom

35、bination of oxygen-hydrogen h2and 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 becom

36、es noticeable close to the end of charge. other redox reactions by impurities in electrolyte.,page 42,li-ion battery self-discharge,temperature：the higher temperature, the higher self-discahrge rate temperature rise will accelerate all redox reactions. age：the more age, the higher self-discahrge rat

37、e the age, the more crack of active materials, the higher surface area, the more matters of redox reactions. note: cell structure design the reactions between electrolyte and electrode always exsit in the process of self-discharge, which makes poor the material activity and changes its structure, le

38、ading to decrease the ennergy(voltage) of the cell under the constant capacity.,page 43,1.4 monitoring and safety,1、safety li-ion battery safety problems need more anntention: more activity of li, reaction with mounts of material high specific ennergy consequence: thermal runaway(熱逃逸，熱失控)：the temper

39、ature rise, the more additive heat. thermal positive feedback battery explode(expansion by heat or much more gas) sources: manufacture process. internal short circuit, metal particles age process. cell imbalance, electrode imbalance unreasonable operation, over discharge/charge. crystal structure change, dendritic crystal, internal short circuit,page 44,1.4 monitoring and safety,2、safety problem example external short c