Li-ion-Battery-introduction锂离子电池介绍

1、Battrey Chemistry Fundamentals and Characteristics,Sinowealth BP wxl,CONTENTS,Introduction,01,Li-ion Battery Fundamentals and Electrical Behavior,02,Monitoring and Safety,04,General Battery Characteristics,03,Page 2,1.2 Li-ion Battery Fundamentals and Electrical Behavior,1.2.1 Battery Structure 1.2.

2、2 Fundamentals 1.2.3 Materials and their influences 1.2.3 Electrical behavior 1.2.4 Equivalent circuit,Page 3,Li-ion Battery Structure,Cylindrical Li-ion Battery structure,Separator, cathode and anode are around the column.,Page 4,18650,Li-ion Battery Structure,Prismatic Li-ion Battery Structure,Pag

3、e 5,Li-ion Battery Structure,Coin Li-ion Battery structure,Page 6,Li-ion Battery Structure,Thin Film Li-ion Battery Structure,10-100um thinkness. for microminiature device,Page 7,Li-ion Battery Structure,Page 8,Li-ion Battery Structure,Li-ion Battery Structure: Anode Cathode Separator Electrolyte En

4、closure and package,Page 9,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 10,Capacity Calculation： 1mol Li+ ,Q=96500C（F=NA*e=96500C/mol ） 1C = 1As Take LiFePO4 for example: The for

5、mula 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 11,Li-ion Battery anode materials and their peformances,Page 12,LiCoO

6、2,LiMn2O4,poor safety, high cost,Synthesis difficult,serious attenuation,LiNiO2,Li-ion battery anode materials,Page 13,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 have the

7、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 14,Li-ion battery Performance requirements of cathode materials,Li+ can be embed and seperated rapidly. good reversibility of Li+ reac

8、tion 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 15,Li-ion battery Cathode materi

9、als,Page 16,synthetic graphite,silicon carbon alloy,Li-ion battery cathode materials performance,Page 17,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 surface.It ca

10、n 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 18,二次锂电池正负极材料电压-容量分布图 Voltage versus capacity for positive- an

11、d 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 19,Fig.2 electrolyte product manufacture process,Li-ion battery electrolyte,Electrolyte is one of four maj

12、or 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.,Pa

13、ge 20,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 electrolyte mater

14、ials,Page 21,safety, stability, compatibility with cathode, conductivity, high dielectric constant, low viscosity. composed by solvent and additive,solvent,Li-ion battery electrolyte solvent,Page 22,Li-ion battery electrolyte additive,Page 23,1.liquid state, solution. high purity solvent, electrolyt

15、e(LiPF6), additive. 2.solid state, ploymer. polymer lithium ion battery, LIP.,Li-ion battery electrolyte,Page 24,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 25,Li-ion battery separator performance,Pa

16、ge 26,porous ploymer thin film（PP,PE,PP/PE/PP） mechanical property, wettablity, pore close temp point and fusing point conflict non-woven fabrics,Separion 无纺布型 high porosity nanofiber film Separion thin film ploymer electrolyte solid, gel,Li-ion Battery Separator,Page 27,Celgard2400 separator，PP，25m

17、，37% porosity，0.117m*0.042m pore size,Li-ion battery separator example,Page 28,Li-ion Battery Characteristics,Chemical Capacity and Energy Battery Impedance Usable Capacity Power Capability Cycle Life, Durability, Shelf Life Self-Discharge Properties,Page 29,Li-ion Battery Chemical Capacity/Energy,Q

18、max： 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 che

19、mical materials in Ah, but Wh for different chemical battery.,Fig. x Voltage profile during low-rate discharge of battery,Page 30,Li-ion Battery Battery Impedance,Battery Impedance：dV=I*R, after transient process Nyquist plot: Voltage responses on current of different frequency A1:impedance, stretch

20、ing real value of A2,3,5 A5:0.51s A6:1000s,Relaxation time,Page 31,Li-ion battery Battery Impedance,Battery Impedance：dV=I*R, after transient process Nyquist plot: Voltage responses on current of different frequency A1:1000s.real sesistance stop increasing， IR drop constant，DC resistance.,Relaxation

21、 time,Page 32,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 times l

22、arger 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.,

23、Li-ion battery Battery Impedance,Page 33,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 SO

24、C. 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 devices r

25、esult in enviroment temperature around the cells rising, abundant heat exchange(put in thermal box) is nessanary for monitoring.,Li-ion battery Usable Capacity,Page 34,Ragone Plot: Power Density(W/kg)-Energy Density(Wh/kg). /kg, /l, /m2 Energy Density(Wh/kg): battery ennery for battery one cycle use

26、 Power Density(W/kg):battery power for battery proviod ennery every unit time,Li-ion battery Power Capability and Ragone Plot,Page 35,cell aged：chemical capacity loss and impedance increase chemical capacity loss： reason：crystal structure of active change influnce：high and low- rate discharge applic

27、ations 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 36,Li-ion Battery Cycle Life,Analyze： Experimental results-impedance increase influnce is much large

28、r 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 37,Shelf life depends on storage voltage(storage SOC) and storage temper

29、ature. 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 will use

30、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 Ba

31、ttery Shelf Life(Storage Life),Page 38,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 sto

32、rage life of the battery. Under the same charge current condition, the lower charge voltage, the longer cycle life of the battery.,Page 39,Li-ion battery Self-Discharge,Self-discharge Mechanism: Parasitic conductance Dendritic crystal grows in charge process, decreasing the suface of anode. Saperato

33、r 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 back to c

34、athode. 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 40,Li-ion battery Self-Discharge,Self-discharge Mechanism: Recombination

35、 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 becomes notic

36、eable close to the end of charge. Other redox reactions by impurities in electrolyte.,Page 41,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 rate the ag

37、e, 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, leading to

38、 decrease the ennergy(voltage) of the cell under the constant capacity.,Page 42,1.4 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(热逃逸，热失控)：The temperature ri

39、se, 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 43,1.4 Monitoring and Safety,2、safety problem example external short circuit,