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Battery History and Anatomy

Matthieu Dubarry

[email protected]

mailto:[email protected]

Electricity was not used before less than 400 years ago

No practical use until the mid to late 1800s.

250000 light bulbs at the Chicago World Columbia Exposition (1893)

Bridge illumination over the Seine river in Paris, France (1900)

How old do you think the first battery is compare to electrification?

Centuries before? Just before? Right after? Well after?

Answer: -1000 BCE : The Baghdad Battery

A brief history of electrochemical systems

More details: Mythbusters episode 29

1749: Benjamin Franklin’s capacitors

Panels of glass coated with metal on each surface.

Used as static electricity generators.

Linking them together in a "battery" gave a stronger discharge.

Battery original meaning: "group of two or more similar objects functioning together", as in an artillery battery.


1791: Luigi Galvani

Luigi Galvani, an Italian physicist, discovered a hint that paved the way to the idea of the battery. Galvani was dissecting a frog attached to a brass hook with an iron scalpel, and as he touched the frog’s leg, the leg twitched. The physicist believed that this was due to “animal electricity” wherein the energy that sparked the movement came from the leg itself.


1800: “Modern” batteries, Alessandro Volta

Alessandro Volta believing this phenomenon was caused by two differentmetals joined together by a moist intermediary.

He verified this hypothesis through experiment, and published in 1791.

In 1800, Volta invented the first true battery, which came to be known as thevoltaic pile : pairs of copper and zinc discs piled on top of each other,separated by a layer of cloth or cardboard soaked in brine (i.e., theelectrolyte).


https://www.youtube.com/watch?v=5DnaxcUKuhQ

https://www.youtube.com/watch?v=5DnaxcUKuhQ

Theory of electrodynamics

From Volta’s discovery, study of electrical current became possible:

1820, Ampère’s law of interaction between electrical currents;

1827, Ohm’s law of proportionality between voltage and current;

1831, Joule’s law of the thermal effect of electrical current;

1831, Faraday’s law of electromagnetic induction, and many others.

These achievements led to the development of the theory of electrodynamics and practice of electrical engineering and, as a result, to the appearance of a revolutionary new power source: the electromagnetic generator invented in 1866 by Werner von Siemens, which soon surpassed their predecessors both in electrical and economic parameters.


1839: William Robert Grove invented the fuel cell

He called it gas voltaic battery, produced electrical energy by combining hydrogen and oxygen.

In showing that steam could be disassociated into oxygen and hydrogen, and the process reversed, he was the first person to demonstrate the thermal dissociation of molecules into their constituent atoms


1859: Gaston Planté invented the lead acid battery

First rechargeable system

His early model consisted of a spiral roll of two sheets of pure lead separated by a linen cloth, immersed in a glass jar of sulfuric acid solution



1866: Georges Leclanché, forerunner of the modern dry cell battery.

It comprised a conducting solution (electrolyte) of ammonium chloride with a negative terminal of zinc and a positive terminal of manganese dioxide.

These “dry” Leclanché batteries proved to be very simple with regard to manufacture and reliable in usage. As early as 1868, more than twenty thousands of such cells were being manufactured.


20th century: new technologies and ubiquity:

1949: Alkaline dry cells (market 1959)

1949: Hajek imagined the Lithium batteries

1957: Invention of lithium batteries by Herbert & Ulam

1966: Supercapacitors were invented in Cleveland.

Late 1960s: Nickel Metal Hydride cells

1970s: Li-ion batteries (Whittingham) & Flow batteries

1990: Commercialization of Ni-MH batteries

1991: Commercialization of Li-ion batteries (SONY)

Early 1900s to 1920s: The (hopefully 1st) golden age of electric vehicles

1884: Invented by Thomas Parker (UK)

1895: First auto race in America , won by an EV.

1896: First car dealer – sells only EVs.

1898: NYC blizzard, only EVs were capable of transport on the roads.

1900: NYC's huge pollution problem – horses. 2.5 million pounds of manure, 60,000 gallons of urine daily on the streets; 15,000 dead horses removed from the streets each year. All US cars produced: 33% steam cars, 33% EV, and 33% gasoline cars.

A brief history of electric vehicles

1990s: Revival of interest for EVs

Push from the California Air Resources Board for lower emissions vehicles

Chrysler, Toyota, and a group of GM dealers sued CARB in Federal court, leading to the eventual neutering of CARB's ZEV Mandate.


http://www.whokilledtheelectriccar.com/

2010s: New generation of EVs

The world's two best selling all-electric cars of all-time are the Nissan Leaf with 200,000 global sales, and the Tesla Model S, with 100,000 units, both, by December 2015


A look into the future…


Air batteries

Li-sulfur batteries For storage: different opportunities

Summarized timeline:


http://www.upsbatterycenter.com/blog/history-batteries-timeline/https://en.wikipedia.org/http://batteryuniversity.com/learn/article/when_was_the_battery_inventedhttp://www.upsbatterycenter.com/blog/history-batteries-timeline/http://www.electricauto.org/?page=evhistory

Sources:

http://www.upsbatterycenter.com/blog/history-batteries-timeline/

https://en.wikipedia.org/

http://batteryuniversity.com/learn/article/when_was_the_battery_invented

http://www.upsbatterycenter.com/blog/history-batteries-timeline/

http://www.electricauto.org/?page=evhistory

Principles

Reactions in batteries are chemical reactions between an oxidizer and a reducer.

In reactions of this type, the reducer being oxidized releases electrons while the oxidizer being reduced accepts electrons.

In the simple case a battery (cell) consists of two electrodes made of different materials immersed in an electrolyte. The oxidizer is present on one electrode, the reducer on the other.

Battery AnatomyEl

ectr

od

e 1

Elec

tro

de

2

Electrolyte

e- ions

e- ions

When these electrodes are placed into the common electrolyte, an open circuit voltage (OCV) develops between them. When they are additionally connected by an electronically conducting external circuit, the OCV causes electrons to flow through it from the negative to the positive electrode.This current is the result of reactions occurring at the surfaces of the electrodes immersed into the electrolyte.

Activity table

Battery Anatomy - Half cell potentials

More extensive one:http://en.wikipedia.org/wiki/Standard_electrode_potential_(data_page)

The more positive the half-cell EMF, the greater the tendency of the reductant to donate electrons, and the smaller thetendency of the oxidant to accept electrons.

A species in the leftmost column can act as an oxidizing agent to any species below it in the reductant column.

Oxidants such as Cl2 that are above H2O will tend to decompose water.

http://en.wikipedia.org/wiki/Standard_electrode_potential_(data_page)



Classification

By their principles of functioning, batteries can be classified as follows:

1. Primary (single-discharge) batteries.

A primary battery contains a finite quantity of the reactants participating in the reaction; once this quantity is consumed (on completion of discharge), a primary battery cannot be used again (“throw-away batteries”).

Battery Anatomy

Classification


2. Secondary (or rechargeable) batteries.

On the completion of discharge, a storage battery can be recharged by forcing an electric current through it in the opposite direction; this will regenerate the original reactants from the reaction (or discharge) products.

Battery Anatomy

Classification


3. Fuel cells.

In the fuel-cell mode of operation, reactants are continuously fed into the cell (or battery) while reaction products are continuously removed.

Hence, fuel cells can deliver current continuously for a considerable length of time, which largely depends on external reactant storage.

Battery Anatomy

Classification


2.5 Flow batteries

Electrolyte tanks. Can be changed or recharged

Battery Anatomy

Classification


4. Supercapacitors.

Electrochemical capacitors uses the double-layer effect to store electric energy. This double-layer has no conventional solid dielectric which separates the charges.

Battery Anatomy

Different chemistries: different properties, price, efficiency and lifetime

Battery Anatomy

Different chemistries: different properties, price, efficiency and lifetime

Battery Anatomy

Source: KEMA Market Evaluation for Energy Storage in the United States

Modern battery dates back to the 1800s

Invented by Alessandro Volta

Opened the gate to electrification

Lot different chemistries invented since the 1800s

Provide different voltages, performances, lifetime…

Choice depends on application

Li-ion batteries, Lead Acid batteries, Ni-MH, Fuel cells…

Battery History and Anatomy – Take home message

Any questions?

Electricity and the waterfall analogy

Water only spontaneously flows one way in a waterfall.

Likewise electrons only spontaneously flow one way in a redox reaction

From higher to lower potential energy.

Battery Anatomy

Electricity and the waterfall analogy

The Voltage is the driving force, the Current is the flow of electric charge

The Resistance is the opposition to the passage

Battery Anatomy

Height (voltage)

Kahiwa falls Akaka falls Rainbow falls

Flow (current)

Resistance (opposition)

660 m 129 m 31 m

small medium large

negligible negligiblemedium(6 tiers)


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Lithium battery specifics

Matthieu Dubarry

[email protected]


First specificity: the voltage


Eo (V)

H2O/O2

H+/H2 0

1.23

–

+Fuel cell, 1.23V

PbSO4/Pb -0.36 –

PbO2/PbSO4 1.68 +Lead Acid, 2.1V

Ni-MH, 1.2V

MH/M

NiO(OH)/Ni(OH)2

~- 0.6

0.6

–

+

Li+/Li

Fe3+/Fe2+

-3

0.77

–

+Lithium, 3.77V

From their chemistry Lithium batteries have2x or 3x more energy than other technologies

Li batteries should not work because there is no stable electrolyte

The KEY of Li batteries is: « it works ONLY because stable SEI forms and prevents further electrolyte degradation »


« SEI » Solid ElectrolyteInterphase

2 V

olt m

ax

Electrolyte Stability window

SEI

SEI

Aqueous electrolyte

Non-Aqueous electrolyte

Lithium dendrites

However, irregularities at the SEI may lead to uneven lithium deposition upon charge, with dendrite formation that grows to short the cell.

In extreme cases, these uncontrolled events give rise to overheating effects with associated thermal runaway and explosions.


https://www.youtube.com/watch?v=zwLUD41f15U https://www.youtube.com/watch?v=uyO-XE-Q9ZQ

https://www.youtube.com/watch?v=zwLUD41f15U

https://www.youtube.com/watch?v=uyO-XE-Q9ZQ

Proposed solution to the dendrite problem:

(1) a careful choice of the electrolyte system to assure optimized, smooth

lithium deposition

Demonstrated as early as the early 1980s but expensive and harsh chemicals

(2) Another popular route for assuring safe lithium cycling was to switch from liquid, reacting solutions to solid, inert electrolytes.

To prevent serious ohmic polarization, need high lithium conductivity at RT.

Not many materials fulfill this condition.Solid state polymer electrolyte (PEO): working at T>70°C

Was commercialized in the late 90’s

Successful demonstration project but abandoned.

Recently reconsidered by Bolloré/Blue Solutions for the blue car


Blue Solutions Lithium metal polymer cell


https://www.blue-solutions.com/en/

Proposed solution to the dendrite problem:

(1) a careful choice of the electrolyte system to assure optimized, smooth

lithium deposition

Demonstrated as early as the early 1980s but expensive and harsh chemicals

(2) Another popular route for assuring safe lithium cycling was to switch from liquid, reacting solutions to solid, inert electrolytes.

To prevent serious ohmic polarization, need high lithium conductivity at RT.

Not many materials fulfill this condition.Solid state polymer electrolyte (PEO): working at T>70°C

Was commercialized in the late 90’s

Successful demonstration project but abandoned.

Recently reconsidered by Bolloré for the blue car

(3) Replacement of the lithium metal with a less aggressive anode material

Use an intercalation anode: Li-ion cells, the “rocking chair battery”

Use of alloys


Non intercalation batteries



Intercalation Reaction Electrodes

++

++

+

+

++

Intercalation reactionIons are intercalated in the crystal structure of the electrode Diffusion of ions in the electrode intercalation material.

surface reaction

++

e-

+

+ e-

e-

e-

e-

e-

e-

e-

e-

e-

e-

+


Insertion Reaction Electrodes

Examples: V2O5

X. Rocquefelte, Ph.D thesis



Examples: Graphite

Positive electrodes

Nearly all use transition metals

A transition metal is one of the 38 chemical elements from periods 4 to 7 (rows) and

groups 3 to 12 (columns) in the Periodic Table of the Elements.

Unlike alkali metals (column 1) and alkali earth metals (column 2), the transition metals can form ions with a wide variety of degrees of oxidation.

It is this property which is exploited in batteries.

In practice only some of first row are useable because of the existence of high degree of oxidation: Ti, V, Mn, Fe, Co and Ni.

Sc is too rare, Cr is toxic, Cu has a too low potential and zinc not a high enough degree of ox.




Examples: V2O5

X. Rocquefelte, Ph.D thesis


2.8

3

3.2

3.4

3.6

3.8

4

4.2

0 0.05 0.1 0.15 0.2 0.25 0.3

Vo

lta

ge (

V)

Discharged Capacity (Ah)

Li-ion

Lead acid

Present and future development regarding Li-ion batteries

Improvement of the intrinsic performances (energy, power)


Thermal runaway

"thermal runaway" describes a process which is accelerated by increased temperature, in turn releasing energy that further increases temperature. In chemistry (and chemical engineering), this risk is associated with strongly exothermic reactions that are accelerated by temperature rise.

Apply for electrolyte

Decomposition of electrolyte salts and interactions between the salts and solvent start at as low as 70oC. Significant decomposition occurs at higher temperatures.



Lithium resources

https://www.youtube.com/watch?v=7wAH7bdXE6ghttp://vimeo.com/18145602

https://www.youtube.com/watch?v=7wAH7bdXE6g

http://vimeo.com/18145602

Lithium resources

An 18650 cell, which is used almost universally in portable computers,

contains 0.8 g of lithium for a capacity of 2.7 Ah. At $6/kg, the cost

Lithium Resources attributable to lithium is less than $0.005.

For an average-sized electric vehicle, the mass of lithium needed to createa battery pack is around 3 kg. At $6/kg, the cost of the lithium works out atless than $20, a very small part of the final cost of the battery pack



Any questions?

Electrode architecture


Mixing the Active material (poor conductivity) with

Electron-conductive agent (CB powder) e- conductivity

Liquid electrolyte within the porosity Li+ conductivity

Polymeric binder B Cohesion and Adhesion

CB/Binder network

AM

Li+

Liq

uid

ele

ctr

oly

te

e-

e-

e-

Cu

rr

en

t c

oll

ec

tor

Li+

Li+

Positive electrodes


The first commercial prototypes appeared in the late 1970s,

Exxon Company using a TiS2 cathode and Moli Energy Battery group using a MoS2, both with liquid organic electrolytes.

However, some operational faults, including fire incidents, led to the rapid conclusion that there were some problems that prevented safe, extended operation of these first lithium batteries.

It was soon realized that the problems were associated with the anode; due to its very high reactivity, lithium metal reacts readily with the electrolyte: formation of a passivation layer on its surface.


An Exxon LiTiS2 rechargeable lithium battery exhibited at the Chicago electric vehicle (EV) show in 1977. This cell used a tetramethylboride salt in dioxolane solvent electrolyte and each cell had a capacity of 45 Wh. It had pressure relieve valves, to ensure no pressure buildup.


Ph: (808) 956-2349 Fax: (808) 956-2336

Lithium-ion battery testing and degradation analysis

Matthieu Dubarry

[email protected]

50


Introduction

Path dependence of the degradation

What is the problem?

Different paths will lead to different degradation and different evolution of OCV vs. SOC curves.

51

Introduction



?

Possible to handle individual paths

52

Introduction



?

Infinite possible combinations : Impossible to predictNeed to diagnose on board on a case by case basis

53

Battery degradation is extremely sensitive to usage and chemistry.

Introduction


Ca

pa

city

Time

Path A

Path BPath D

Path C

54

Active

elements

StructureMorphology Architecture

Loading,

SeparatorCasing

Voltage

Theoretical CapacityRate capabilityCycle life

Ohmic resistance

Nominal capacity

Cell specificcapacity

Intrinsic Electrode processing

Cell manufacturingΔ Rate capability

Δ ResistanceΔ Capacity

Δ Weight

Δ PERFORMANCE

55Introduction


Need to characterize cells variability

To compare cells and protocols

To insure safety of battery packs

Can be fully addressed with 3 attributes:

Capacity : Amount of active material

Resistance : Ohmic resistance

Rate capability: Faradic resistance

Laboratory testing

Cell to cell variations

Dubarry, Vuillaume, Liaw, Int. J. Energy Res., 34 (2010) 216–231.

Dubarry, Vuillaume, Liaw, J. Power Sources 186 (2009) 500-507.

56

Laboratory testing

Good practices

57

Formation cycles

1 – Ensure formation is completed(stable capacity & voltage response)

2 – Assess cell-to-cell variations1 cycle @ C/21 cycle @ C/5

Duty Cycle

1 – Must be representative of real usage

End Of Life

Laboratory testing

Good practices

58

Formation cycles

1 – Assess cell performance2 – Allow electrochemical analysis

At least:1 cycle @ C/25 Thermodynamic assessment1 cycle @ C/1 Kinetic assessment

End Of Life

Duty Cycle

ReferencePerformanceTest

MonthlyReferencePerformanceTest

Useful diagnosis is a complex balance

Battery Diagnosis

A complex balance

59

Accuracy of diagnosis Diagnosis resources

LOW

HIGH LOW

HIGH


Academics

60


LOW

HIGH LOW

HIGH

Post mortem analysisHalf cell analysis,…XRD, EXAFS, XANES,…First principle modeling,…

Expensive & complexExperimentsHeavy computing

Battery Diagnosis

A complex balance

Lithium ion battery degradation mechanisms

Introduction

Why derivative methods?

J. Groot, State of Health Estimation of Li-ion batteries cycle life test methods

61


Industry

62


LOW

HIGH LOW

HIGH

Voltage & capacity monitoring

Simple characterizationLook up tablesLimited computing

Battery Diagnosis

A complex balance

Classic Industry outputs

63

Q

t t

R

Limited to no knowledge of degradation mechanisms

Battery Diagnosis

A complex balance

0

0.5

1

1.5

2

0 200 400 600 800 1000

2C agingC/25C/5C/2C/12C5C

Ca

pacity (

Ah)

Cycle #

Use testing to address key parameters

Battery Diagnosis

A complex balance

64

Cycle life

Ohmic resistance

VoltageCapacity

Rate capability

10

100

10 100

-20oC

-5oC

10oC

25oC

40oC

60oC

Sp

ecific

en

erg

y (

Wh

.kg

-1)

Specific power (W.kg-1

)

200

400

Voltage vs. capacity Capacity vs. cycle #

Specific P & E vs. TRohmic vs. T

2.5

3

3.5

4

0 0.5 1 1.5 2

C/25

C/5

C/2

C/1

2C

5C

Voltage (

V)

Capacity (Ah)

Conventional battery testing only assess cell performance metricsNot performing diagnostics for battery management


Derivative methods can offer an happy balance

65


LOW

HIGH LOW

HIGH

Look up tablesMedium computing

Battery Diagnosis

A complex balance

Lithium ion battery degradation mechanisms

J. Groot, State of Health Estimation of Li-ion batteries cycle life test methods

Change in lithium

inventory

Change in active

material

Change in ohmic and

faradic resistances

Useful categorization for diagnostics

Thermodynamics

Kinetics

66Battery Diagnosis

A complex balance


Derivative methods can offer an happy balance

67


LOW

HIGH LOW

HIGH

Quantification ofdegradation modes

Look up tablesMedium computing

Battery Diagnosis

A complex balance

Adapt to industry requirements:

Use of available sensors: voltage, current and temperature.

Voltage carries thermodynamic information

Study evolution of voltage response

How can we extract degradation information?

How can we put it in equation for a model?

Use derivative method (enhance changes): IC

Link every feature to corresponding

reactions in the PE and the NE

Follow peak evolution to deduce the origin

-2

-1.5

-1

-0.5

0

3 3.2 3.4 3.6 3.8 4 4.2

Cycle 10Cycle 250Cycle 500

Incre

me

nta

l cap

acity (

Ah

V-1

)

Voltage (V)

2.6

2.8

3

3.2

3.4

3.6

3.8

4

4.2

0 0.5 1 1.5 2


Incre

men

tal cap

acity (

Ah V

-1)

Voltage (V)

68Battery Diagnosis

A complex balance

Capacity (Ah)

Voltage (

V)

ΔQ/ ΔV

Experimentally: possible by coupling 2 techniques:

Battery Diagnosis

A complex balance

0

10

20

30

40

50

60

70

0 200 400 600 800 1000

C/25C/5C/2C/12C

Cap

acity lo

ss (

%)

Cycle #

Loss of lithium inventory

Loss of active

material

Kinetic limitations

Resistance increase

-2

-1.5

-1

-0.5

0

3 3.2 3.4 3.6 3.8 4 4.2


Incre

men

tal cap

acity (

Ah

/V)

Voltage (V)

0

10

20

30

40

50

0 200 400 600 800 1000

C/25C/5C/1C2C

EO

D S

OC

(%

)

Cycle #

SOH tracking +

SOC tracking

M. Dubarry et al. J. Power Sources 196 (2011) 10336

M. Dubarry et al. J. Power Sources, 196(7), (2011) 3420

M. Dubarry et al. J. Power Sources 194 (2009) 551

Rest cell voltagesevolution

Incremental capacitycurves evolution

Change in lithium

inventory

Change in active

material

Change in ohmic and

faradic resistances

2C aging at RT

69

1.2

1.4

1.6

1.8

2

2.2

2.4

0 500 1000 1500 2000

DST/4C

4C/4C

y = 2.2446 - 0.0001232x R= 0.9978

y = 2.3051 - 9.9021e-5x R= 0.99331

Cap

acity (

Ah

)

Cycle #

Battery Diagnosis

A complex balance

-40

-35

-30

-25

-20

-15

-10

-5

0

3.1 3.15 3.2 3.25 3.3 3.35 3.4 3.45 3.5

IC (

Ah

/V)

Voltage (V)

-40

-35

-30

-25

-20

-15

-10

-5

0

3.1 3.15 3.2 3.25 3.3 3.35 3.4 3.45 3.5

IC (

Ah

/V)

Voltage (V)

-40

-35

-30

-25

-20

-15

-10

-5

0

3.1 3.15 3.2 3.25 3.3 3.35 3.4 3.45 3.5

IC (

Ah

/V)

Voltage (V)

We studyvoltagevariations

To understandthe degradationfrom a materialstand point

We then use that knowledgeto predict what willhappen to the cell

?Conventional approach

Our approach

0

5

10

15

20

25

30

35

40

0 500 1000 1500 2000

Deg

rad

ation

%

Cycle number

LAMNE: loss of negative electrode material

LLI: Loss of lithium inventory

Peak indexation: The clepsydra analogy

Use individual electrode response

Understanding the degradation mechanisms

Understanding the IC signature

Peak

Beginning of discharge

Middle of discharge

End of discharge

-3

-2.5

-2

-1.5

-1

-0.5

0

3.2 3.4 3.6 3.8 4 4.2

Incre

men

tal cap

acity (

V-1

)

Voltage (V)

LiMn⅓Ni⅓Co⅓O

2

LiMn2 O

4

Peak Peak

Li+

M. Dubarry et al., J. Power Sources, 196 (2011) 10328.

M. Dubarry, A. Devie and B.Y. Liaw, JEPS In press

Water clock concept: M. Dubarry et al. ECS222/PRIME2012 (2012) abs# 885

IC curves contains information on every component of the cell

The clepsydra analogy enables the indexing of IC curves

NE NE NE

PE PE PE

Vo

lta

ge

Vo

lta

ge

Vo

lta

ge

Li+

71

Clepsydra analogy: Visualize effect of categories of degradation

Understanding the degradation mechanisms

Understanding changes in the IC signature

Initial LAMPELLI Ohmic R increase Faradic R increase

Different degradation categories will have different voltage signaturesDiagnostic possible w/o post-mortem analysesNo need to be an electrochemist

Vo

lta

ge

72

Simple, fast, powerful and accurate diagnosis and prognosis tool

Mechanistic diagnosis and prognosis

Graphical user interface: the ‘alawa toolbox

Stand alone GUI available for license or collaboration

73

Degradation maps: GIC//LFP


Degradation simulation examples

74


Unique capabilities and benefits

Dubarry, Truchot and Liaw, J.Power Sources, 219 (2012) 204-216

Multi degradation simulationdV/dQ simulation

dQ/dV simulation

Q, P, SOC, RCV calculations

75

Effect of path : from any sources of information

(e.g. laboratory testing, literature, physical modeling,…)


Path dependence emulation

If the effect of a path is known, it can be emulated:Prognosis and path dependence emulation

Computation is not intensive.Easy to parameterize. Easy to use.

Complement other modeling approachesReduce complexity: Could be the link between battery material research and BMS

* Dubarry et al. J. Power Sources 196 (2011) 10336

** Kassem et al. J. Power Sources 208 (2012) 296

*** Dubarry et al. J. Electrochem. Soc, 160(2), p. A191 (2013).

RTcycling

Calendaraging

LTexcursion

HTexcursion

Linear LLI +Exponential LAM

*

LLI = f(t,T,SOC) ** LLI+ RDF = f(T) ***

LLI = f(T) ***

Initial LLI thenLinear LLI +

Exponential LAM*

0

20

40

60

80

100

0 200 400 600 800 1000

Cap

acity a

nd

de

gra

datio

n (

%)

Cycle #

Regular RT cycling

LAMNMC

LLIcalendar+LLIaging

LLIcalendar

RT cycling after calendar ageing

76

Battery packsNeeds battery model and state estimator

77

State of Charge (SOC) Estimation

Equivalent of a fuel gauge

for a battery

State estimator

The SOC problem

How is it calculated?

9.5

10

10.5

11

11.5

12

12.5

13

020406080100

Vo

ltag

e (

V)

SOC (%)

Rest Voltage compared lookup table

25

78

9.5

10

10.5

11

11.5

12

12.5

13

020406080100

Cycle 1Cycle 350Cycle 650Cycle 950

Vo

ltag

e (

V)

SOC (%)

State of Charge (SOC) Estimation

State estimator

The SOC problem


1025

To stay accurate OCV vs. SOC curves needs to be updated according to battery state of health (SOH)

Rest Voltage compared lookup table

79

Academia and industry do not have the same definition for SOC.

For industry, SOC is often defined as “The ratio of the Ampere hours remaining in a battery at a given rate to the rated capacity under the same specified conditions”.

Some people read it as using the nominal capacity instead of “the rated capacity under the same specified conditions”

For academia (and especially electrochemists), SOC is a state function which represents the thermodynamic property of the system.

State estimator

The SOC problem

𝑆𝑂𝐶𝑡 =𝑅𝑒𝑚𝑎𝑖𝑛𝑖𝑛𝑔 𝑒𝑥𝑐ℎ𝑎𝑛𝑔𝑒𝑎𝑏𝑙𝑒 𝐿𝑖+ 𝑖𝑜𝑛𝑠

𝑇𝑜𝑡𝑎𝑙 𝑒𝑥𝑐ℎ𝑎𝑛𝑔𝑒𝑎𝑏𝑙𝑒 𝐿𝑖+ 𝑖𝑜𝑛𝑠=

𝑄𝑟𝑒𝑠𝑖𝑑𝑢𝑎𝑙

𝑄𝑚𝑎𝑥

𝑆𝑂𝐶𝑈 =𝑄𝑟𝑒𝑠𝑖𝑑𝑢𝑎𝑙

𝑄𝐶

𝑆𝑂𝐶𝑒 =𝑄𝑟𝑒𝑠𝑖𝑑𝑢𝑎𝑙

𝑄𝑛𝑜𝑚

80

2.8

3.2

3.6

4

0 20 40 60 80 100

C/25

C/5

C/2

C/1

2C

Vo

lta

ge

(V

)

Normalized capacity (%)

Let’s compare them:

State estimator

The SOC problem

SOCt

SOCU definition: SOC scale depends on applied current.Make sense as fuel gauge: miles you can do if you maintain your speedBUT no reference and so no link to thermodynamics.

0100

0100SOCe


𝑄𝐶


𝑄𝑛𝑜𝑚

𝑆𝑂𝐶𝑡 =𝑄𝑟𝑒𝑠𝑖𝑑𝑢𝑎𝑙

𝑄𝑚𝑎𝑥

vs. vs.

0100SOCU@C/2

0100SOCU@C/25

0100SOCU@2C

SOCe definition: SOC scale do not depend on applied current.BUT awkward fuel gauge: miles you can do is you start driving at 60mphAnd still no link to thermodynamics.

SOCt definition: link to thermodynamics.BUT awkward fuel gauge:miles you can do if youslow down to really low speed

A common ground need to be met to allow proper communication

X

X

81

Let’s compare them:

State estimator

The SOC problem

SOCU definition: SOC scale depends on applied current.Make sense as fuel gauge: miles you can do if you maintain your speedBUT no reference and so no link to thermodynamics.


𝑄𝐶


𝑄𝑛𝑜𝑚

𝑆𝑂𝐶𝑡 =𝑄𝑟𝑒𝑠𝑖𝑑𝑢𝑎𝑙

𝑄𝑚𝑎𝑥

vs. vs.

SOCe definition: SOC scale do not depend on applied current.BUT awkward fuel gauge: miles you can do is you start driving at 60mphAnd still no link to thermodynamics.

SOCt definition: link to thermodynamics.BUT awkward fuel gauge:SOC miles you can do if youslow down to really low speed

X

X𝑆𝑂𝐶𝑈 =

𝑄𝑟𝑒𝑠𝑖𝑑𝑢𝑎𝑙

𝑄𝐶

X

= 1 − 𝐷𝑂𝐷𝑈

The best solution to reduce disconnect would be to use two different metrics:

DOD for fuel gauge applications

SOC for battery state monitoring

DOD 1 – SOC but can be calculated from SOC.

C. Truchot, M. Dubarry and B.Y. Liaw, Applied Energy, 119, 218 (2014).

M. Dubarry, V. Svoboda, R. Hwu, and B.Y. Liaw, J. Power Sources, 174(2), 1121 (2007).

82

New approach using in-situ data and single cell OCV response

E.g. 3S string with T gradient

State estimator

SOC calibration for battery packs

83

0.5

0.6

0.7

0.8

0.9

1

1.1

0 100 200 300 400 500 600

25oC

60oC

3S1P

Cap

acity,

Ah

Cycle #

25°C 60°C 25°C

Easy and quick in-situ battery pack full OCV vs. SOC curve determinationAlso allows accurate imbalance tracking

M. Dubarry, C. truchot, A. Devie, and B.Y. Liaw, Journal of The Electrochemical Society, 162 (6) A877-A884 (2015)

Lithium-ion battery testing and degradation analysis

Any questions?

Formation cycles

End Of Life

Duty Cycle

ReferencePerformanceTest

MonthlyReferencePerformanceTest

-2

-1.5

-1

-0.5

0

3 3.2 3.4 3.6 3.8 4 4.2


Incre

men

tal cap

acity (

Ah

/V)

Voltage (V)

-2

-1.5

-1

-0.5

0

3 3.2 3.4 3.6 3.8 4 4.2


Incre

men

tal cap

acity (

Ah

/V)

Voltage (V)

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