10+battery+technology (1)

8/2/2019 10+Battery+Technology (1)

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Battery Technology

MSE 6080 Spring 12


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Where our energy comes from

MRS Bull 33 (2008) 264


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Renewable energy


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Power Generation Devices

Chem Soc Rev38, 226


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Electrochemical Power Sources Chemical energy transformed directly into

electrical currents Portable sources of electrical power (watches,

portable electronics, start-up of cars)

Store electrical energy supplied by an external source

(electric vehicles, supplementary power supply duringpeak requests)

First battery Volta, 1800

Today 8 15 batteries for every human onEarth

World market in excess of $ 200 billion


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Mobile Power Portable electronic

devices

increasing powerrequirements

Microsized,autonomous

systems (MEMS)may requirebatteries withperformancesunavailable today

Electric car:capacity, weight,

cost


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Nomenclature Primary battery life has ended once the

reactants have been consumed

Secondary battery can be recharged

when the reactants have been used up


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Survey Battery energies: 10-6 Wh

to 3 MWh Miniature batteries

watches and otherminiature apps 0.5 2

uA, 15-60 mWh/yr

Dry batteries toysradios 10 mAh 15 Ah

SLI batteries Pb acid 12 V, 40-60 Ah, 45 Wh/kg


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Future/current uses A Pb acid battery capable to

drive a vehicle is 50x heavier,

25x the room of the equivalent ICengine Longer time to recharge

Currently NiMH

Na or Li based batteries up to100 Wh/kg

Stationary batteries standbypower emergency (250 Wh 5MWh)

Load leveling public powersupply. increase base loadcapacity to stockpile energy andmeet peak energy needs


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Theoretical An electrochemical reaction

provides current throughchemical transformations at theelectrodes and in the electrolyte

Max energy obtainable:G = -zFE

Amount of transformation

proportional to the chargepassed through the cell

Cathode: e flow from theexternal circuit (red)

Anode: e flow to the externalcircuit (ox)

Discharge Charge


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Theoretical 2 The EMF of a battery

tends to decrease with

operation

Design to provide for

small changes in OCP Pt/Fe3+,Fe2+Ce4+, Ce3+/PtFe2+ + Ce4+ Fe3+ + Ce3+

Zn/ZnO/KOH/HgO/HgZn + HgO ZnO + Hg


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Losses Due to the passage of current

Ohmic drop in the electrolyte bulk Electrode losses due to CT step

Processes of formation of a solid phase

(crystallization overvoltage) Porous electrodes interface increase,

resistivity decrease

Impregnation to immobilize liquidelectrolyte


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Characteristics Capacity, Energy, Power Polarization curve cell voltage

vs. current Electrode polarization Cell resistance

Diffusion overvoltage (reactantdepletion)

Discharge curve OCP vs. fraction discharge

Cell voltage during deep discharge


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Theoretical Energy p.u. weight

EMF in 30% KOH is 1.29 V

zFE = 2.5105 Ws ~ 6 Wh MNi = 58.7, MCd = 112.4, Mtot = 331.8

Energy density = 208 Wh/kg

Practical values ~ 40 Wh/kg ~ 20%

2NiO(OH) + Cd + 2H2O = 2Ni(OH)2 + Cd(OH)2

Discharge

Charge


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Primary Batteries Leclanch (1866)

Zn chloride Alkaline manganese

oxide

Al- and Mg-basedLeclanch

Schematics of a Leclanche batteryhttp://www.wisedude.com/science_engineering/batteries.htm


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Leclanch Cell Zn anode, MnO2 cathode,electrolyte ZnCl2 + NH4Cl

Cathode: carbon rod in amixture C/MnO2

Anode: Zn rod in satNH4Cl

Electrolyte immobilizedwith a paste

Zn/ZnCl2, NH4Cl/MnO2,C

E ~ 1.5 V

Zn + 2H2O Zn(OH)2 + 2H+ + 2e

2MnO2 + 2H+ + 2e 2MnO(OH)

Zn + 2MnO2 + 2H2O Zn(OH)2 + 2MnO(OH)


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Leclanch Cell, cont

Self-discharge and gas build-up Slow down by amalgamating Zn with Hg

(recently eliminated)

Other drawbacks Short shelf life (needs refrigeration)

Small energy density (75 Wh/kg)

Voltage decreases over time

Alternative: alk battery (KOH)

Zn + 2H2O Zn(OH)2 + H2


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Rechargeable batteries Charge factor: charge used during charge

vs. charge passed during discharge

CF > 1 if side rxns occur during charging

Cycle life: # of charge/discharge cycles

before battery performance degrades ~ 103

Full charging can often be achieved onlyby overcharging. Careful not to evolve

gases! Self-discharge less important


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Pb acid

Why water does not dissociate?

Theor 171 Wh/kg, actual 40

Wh/kg ~ 23% Cyclability depends strongly onmicrostructure

Heavy, low cost

Pb + SO42- PbSO4 + 2e

PbO2 + 2H2SO4 + 2e PbSO4 + SO42- + 2H2O

PbO2 + Pb + 2H2SO4 2PbSO4 + 2H2Odischarge

25% H2SO4

EMF = 2.1 V

Pb

PbSO4

PbO2

PbSO4


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Microstructural evolution of Pb

electrode


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Ni-Cd

EMF 1.29 V

En density 208 Wh/kg

Rate of discharge, T affectcapacity

Longer cycle life than Pb

(up to 3500, 5-10 yrs) High cost, but decreasing

NiO(OH) + H2O + e Ni(OH)2 + OH-

Cd + 2OH- Cd(OH)2 + 2e

2NiO(OH) + Cd + 2H2O = 2Ni(OH)2 + Cd(OH)2

Discharge

Charge

J Power Sources 100, 125


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Ni-Metal hydride Anode LaNi5 based

(high H2 storage) Electrolyte 30%

KOH

En density 40-110Wh/kg

109 sales/yr


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Li-ion battery Li ve

electrode TM oxide +ve

electrode (Liintercalation)

EMF up to 4.5 V

LIanode

Cathode


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Electrodes Anode graphite

Cathode

Technological trends

Better graphite

Enhance +ve electrode

Improve solvent stability

LiC6 Li+ + 6C + e

Li+ + Mn2O4 + e LiMn2O4

Li+ + Mn2IVO4 + e LiMn

IIIMnIVO4

Li+ + FeIIIPO4 + e LiFeIIPO4


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Trends in R&D

100 200 400 800 1,400

Spec. Power Density (W/kg)

Sp

ec.

EnergyDensity(Wh/kg)

50

100

150

200

LeadAcidNi/Cd

Ni/MH

Lithium-Ion Battery

High PowerLIB

High EnergyLIB

MobileIT

HEV

NextGenerationBattery ?

Courtesy Hyun-Soo Kim


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Some designs

Hardpreparation,

Mndissolution

Low electricconductivity

Low electricconductivity

Low tapdensity

Mndissolution

(@E.T.)

Hardpreparation,Low thermal

stability

High cost,toxicity

Demerits

Low cost,

nontoxic

Low cost,

thermal

stability

High

capacity

High

capacity &

thermal

stability, low

cost

Low cost,

nontoxic

High

capacity

High electric

conductivity,

easypreparation

Merits

3.4V3.45V3.6V3.6V3.8V3.5V3.6VOperationVoltage

180mAh/g4.4-3V:90

3-2.0V:90

150mAh/g170mAh/g170mAh/g120mAh/g180mAh/g140mAh/gPracticalCapacity

344mAh/g170mAh/g285mAh/g285mAh/g148mAh/g275mAh/g274mAh/gTheoretical Capacity

LayeredOlivineLayeredLayeredSpinelLayeredLayeredStructure

LiMnO2LiFePO4LiNiMnO2

Li[CoNiMn]O2

LiMn2O4LiNiO2LiCoO2


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Thermal management Above T2, corrosion and degradation

processes become very fast Below T1 the electrolyte has too high a

resistance and charge transfer is too slow

Heat must be dissipated during highcharge/discharge rates

High T batteries: need to heat, avoid heatloss, use a cooling system to avoidoverheating


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Summary Seek high energy density, high power, low

cost EMF is approaching its limits

Room to improve on rates, lifetime 3D geometries for high rates

Low cost


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Energy Density E = 0.5CV2 = 0.5QV

Increase in V advantageous but limited 0.8-1.2 V in aq electrolytes

3-4 V in non aq (lower Cdl)

Increase in spec area energy/weight

7-10% capacity of a battery

Better cycle life

Fast charge/discharge

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