Energy Storage for EVsfrom components to integrated systems

Dr. Tony HollenkampCSIRO Energy TechnologyApril 27, 2011

CSIRO Automotive Research

Four key focus areas:

• Vehicle Electrification• Light Weighting• Alternative Fuel Technologies• Lifecycle, Recycling & Regulation

Involvement in AutoCRC• 15 projects• across 4 Themes

Hybrid and electric vehicle technologies

• Parallel and series hybrids• Electric Machines – design

and prototype construction• Power and control

electronics• Energy storage

• Batteries • Supercapacitors

• System integration

Energy Storage: Energy vs. Power

0.1

1

10

100

1000

10 100 1000 10000

Power density [W/kg]

Ener

gy D

ensi

ty

[W

h/k

g] Fuel Cells

Lithium

ElectrolyticCapacitors

Double LayerCapacitors

Hybrid Capacitors

Lead-AcidBattery

NiCd Adv.Lead-Acid

NiMH

The Family of Lithium Batteries

 

Primary Cells• single use• Li metal (-) + MnO2 (+)• cameras, watches,etc

Secondary Cells• rechargeable• carbon (-) + metal oxide (+)• portable electronics, EVs• liquid electrolyte• polymer electrolyte (gel)→ Li polymer batteries

Lithium-ion battery – animation of charging/discharging

Lithium-ion Variants

Cathode Materials

LiCoO2 Archetype material – unstable at high SoCLiMn2O4 Favoured replacement – unstable at low

SoCLiNi1/3Co1/3Mn1/3O2

Common successor to LiCoO2 – improved stability

LiFePO4 Rapidly replacing oxides – superior cycling stability

Anode Materials

C (graphite) Archetype material – low capacity (LiC6)

Sn and Si Improved capacity but cycle-life issues

Li4Ti5O12 Zero-strain material – excellent cycle-life but low voltage (reduces specific energy)

Li metal Ultimate capacity limit but safety concerns – short circuit formation

Charge–Discharge Characteristics

2.8

3

3.2

3.4

3.6

3.8

4

0 2 4 6 8 10Time (h)

Volta

ge (V

)LiFePO4 — Li (Metal) Cell with Ionic Liquid Electrolyte

VTOC

VEOD

No overcharge reaction

Varying Discharge Rates

9 | CSIRO. Australian Science, Australia's Future

Source: http://www.phet.com.tw/Products/Products_Intro.aspx

60 Ah cylindrical LiFePO4 – Li (graphite) by PHET, Taiwan

Operational Issues with Lithium-ion Batteries

Both Pb-acid and NiMH have overcharge reactionsOxidation of water and reduction of oxygen

But for Lithium-ion - No overcharge reactionè tight charge controlè reduced cell-to-cell variations

EVs require high voltage• Multiple cells in series• Issue: balance between cells

• Protection against overcharging and overdischarging• Both will reduce battery life• Redox-stability of electrolytes – worse as T

Is Lithium-ion Safe?

Electrolyte Properties are a Major Issue (not Li!)• mixture of organic carbonates and ethers→ high-boiling, but they are flammableHeat pressure venting Fire

……..an example…………

Possible Result of Excess Overcharge

Courtesy: Sandia Labs

Is Lithium-ion Safe?

Many causes of heating:• Overcharging – oxidation of electrolyte, destabilization

of cathode, Li dendrites• Joule heating – current flow• Short circuits – internal/external• External heat input

Electrolyte Properties are a Major Issue (not Li!)• mixture of organic carbonates and ethers→ high-boiling, but they are flammableHeat pressure venting Fire

Room Temperature Ionic Liquids (RTILs) — Safe Electrolytes

Low-Melting Molten Salts• MP < 100 ºC• negligible vapour

pressure• non-flammable• good conductivity• high thermal and

electrochemical stability• reversible Lithium

cycling

im

pyr

pip

Pxxxx+

Nxxxx+R1

R2

R4

R3N+

CSIRO. FIED – Soldier Technology, London, May 2010

The FIED

• Flexible Integrated Energy Device (FIED) comprises:

• A Flexible Hybrid Battery• Conductive textiles• Safe RTIL electrolytes• Rechargeable• # of batteries scalable depending

on mission duration• Vibration Energy Harvesting

Device (VEHD) which has a • Wearable Transducer• Conditioning Device to convert

motion into electrical energy• Could be integrated into any

soldier garment and / or equipment

CSIRO. FIED – Soldier Technology, London, May 2010

Challenges of making batteries flexible

• novel flexible electrode materials to replace metal electrodes – Conductive textiles

• novel flexible packaging material to replace stainless steel cans – Polymer sealing materials

• replacement electrolytes to increase battery safety – RTILs

C3mpyr cation FSI anion

High Energy Supercapacitors

• Advantagesü high power density (>2kW/kg)ü rapid charge/recharge (Seconds)ü ‘simple’ energy storage, not conversionü excellent charge/discharge cycle-abilityü No maintenance

• Current Limitationû low energy density (~5Wh/kg) relative to

batteries

Ion permeable separator

Energy = ½CV2 To increase Energy:

Increase C (better carbon, new electrolyte, battery electrode)Increase V (new electrolyte, new electrodes, larger effect)

Poro

us c

arbo

n

Por

ous

carb

on -+

+

++

+++

+

++ +

++

+

+

+ ++

+

+

+++

+++

+

++

+

_

_

_

_

_

_

__

_

_

_

__

_

____

_

___

_

_

_

C1 C2

Carbon (symmetric) Supercapacitor

Charge–Discharge = reversible adsorption/desorption of ions

Increased capacitance with new electrolyte

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0 10 20 30 40 50 60 70 80 90Cell Temperature [°C]

Cell

Capa

cita

nce

[F

arad

s]

RTIL 1

RTIL 5

PC/TEATFB*

AN/TEATFB*

At slightly elevated temperatures, existing RTIL electrolytes show superior performance

* Current commercial electrolytes

CSIRO Ni(OH)2/C Asymmetric Supercapacitors

Prototype Capacitance

[Farads] Energy Wh/kg

Max. Power W/kg

ESR

[m.Ώ] Cycle

Efficiency

06-01 (45 mL) 1980 12.1 4430 2.3 0.99

06-02 (45 mL) 2250 5.8 1670 3.5 0.99

06-03 (90 mL) 1770 5.1 1540 2.3 0.99

06-04 (90 mL) 4740 7.8 1410 2.9 0.96

06-05 (90 mL) 8540 14.8 2740 1.0 0.99

10 Wh/kg(2006)

5 Wh/kg(2005)

Poro

us

carb

on

Bat

tery

el

ectro

de

+-

+++

+++

+

++++++

+

+++++++

++++

++++

C1 C2 >> C1

PbO2 Pb

+ – Separator

Lead–acid cell

+ –

Carbonelectrode

PbO2

Asymmetric supercapacitor+ –

UltraBattery

Pb

Carbon electrode

i

ii1

i2

The UltraBatteryUltraBattery combines an asymmetric capacitor and a lead-acid

battery in one unit cell, without extra electronic control.

UltraBattery - Laboratory and Field Trials

§ UltraBattery meets US FreedomCar power-assist targets§ Cycle-life performance exceeds NiMH § On Millbrook test track, UltraBattery-equipped Honda Insight has passed

100,000 mi and continues to meet all performance specifications

Fuel Usel/100km

Battery cost$US

Ni-MH 4.05 $1500 to $2500

Ultrabattery 4.16 $350 to $400

Electric Driveway Project

• Demonstrate Intelligent Integration of Electric Vehicles with Building Energy Management• Develop ‘prototype’ EV charger/discharger which is integrated

with a home energy management system• Develop Toolkit for EV Scenario Analyses • Project Leader:Dr. Phillip Paevere, CSIRO Ecosystem Sciences

Electric Driveway Project

• Rationale• Potential consumer benefits• Delay/reduce major infrastructure costs

• Key Technology Questions• When do I charge the EV?• When do I use surplus EV energy locally in the

home?• When do I feed surplus EV energy to the grid?

• Many Inputs• Vehicle type, state of charge & projected usage• User preferences & requirements• House required & projected energy usage• TOU tariffs, External charging options & pricing

ED Project Resources

Home Energy Manager• CSIRO / LaTrobe University• Intelligent EV charge & discharge

Zero Emissions House• 8 Star Family Home• 6kW PV Array• Living Laboratory

Conversion of three Toyota Prius for SP-Ausnet• Plug-in charge & discharge• Advanced monitoring & control of energy flow • Extra battery capacity

Dai

ly D

eman

d (G

W)

WinterSummer

Capacity = 145M EV km

Source: Pudney - Uni SA; NEMMCO 2007; ABS 2007

Midday Midnight Midday4

10

8

6

Demand = 124M EV km = 85% capacity

Daily Electricity Demand - VIC

*Network Capacity Required Sydney by 2012

Source: UTS Sustainable Futures

Distribution Network Capacity is Spatially Variable

Example Vehicle-to-Building Scenario*

• 50 km Commute• 25 kWh Battery (e.g. Nissan Leaf)• Never discharge below 40% reserve capacity• TOU Tariff: per kWh: 30c peak / 10c off peak• 2 kW max. discharge power• V2B degrades battery at 50% the rate that driving does**• Value approx. $450 per year• V2B Degradation Cost approx. $100 per year**

* Unpublished results from preliminary data, provided by P. Paevere** based on 2020 battery prices and degradation cost estimates from Peterson et al (2010)

PHEV V2B Project work program

V2B vehicle-building interface• Toyota Prius• 4.7 kWh (15 mile PHEV)• Smart grid

V2B algorithm - to minimize facility demandField operations - operate vehicles in V2B field Laboratory testing - to establish battery life/cost parametersBattery tear-down analysis - establish failure modes

Laboratory Testing – Simulated V2B Duty

150

160

170

180

190

200

210

220

224.15 225.15 226.15 227.15 228.15 229.15 230.15 231.15 232.15

Time of simulated operation (hours)

Batte

ry p

ack

volta

ge

(i) UDDS by 2 to work

(ii) fast charge

(ii i) discharge to grid

(iv) fast charge

(v) UDDS by 2 home

(vi) s low night charge

• UDDS x 2 cycle (15 miles) - 100% to 40% SoC• Fast charge off peak - 40% to 90% SoC 2C rate• Discharge on peak - 90 to 30% SoC 2C rate• Fast charge post peak- 30 to 90% SoC 2C rate• UDDS x 2 cycle (15 miles) - 90 to 30% SoC• Overnight charge - 30 to 100% SoC 1C rate

Cycle repeats ~2.5 h

Battery Lifetime/PHEV Miles

Battery Drive Ahs : Grid Ahs

Simulatedvehicle miles

No. 100% DOD cycles to 80% of initial cap

V2B energy(kWh)

3 cells, 25 °C 2 : 1 102 115 5102 -

3 cells, 50 °C 2 : 1 28 665 1450 -

pack, 35-45 °C 2 : 1 60 515 3120 6000

‘Simulated vehicle miles’ assumes all driving is in charge depleting mode.

Increasing temp from 25 to 50 °C decreases life by 3.5 times

Rest at open circuit, at 52 °C, produces 10% permanent capacity loss after 4 months (0% at 25 °C)

Analysis of Failure Modes

Results consistent with - decrease in negative plate capacity- increase in electrolyte resistance - increase

in resistance of SEI

0.00 0.02 0.040.00

0.02

0.04

F1-1 H2-2

-Zim

ag/O

hm

Zreal/Ohm

new

failedNew negative Negative from

failed high-temp cell

Conclusions

• Cell/battery life very sensitive to T, esp. close to 50 °C Pack design and thermal management are crucial

• Rest at high T also causes significant capacity losschoice of parking location also important

• Focus on stability of negative material and electrolyte• V2B (home) much simpler than coordinated V2G• V2B can potentially reduce total cost of EV ownership

- Subject to TOU and battery management- Terms of battery warranty will be crucial

Other Projects: Energy-related

• High Temperature lithium battery for subterranean use (e.g., exploration drilling)

• Ionic liquids as electrolytes in Dye-Sensitised (Graetzel Type) Solar Cells

• Protic ionic liquids for PEM Fuel Cell membranes• Post-combustion capture of CO2 with ionic liquids• Developing novel ionic liquids as media for thermal

storage and heat transfer• Enhanced lithium extraction from minerals

On the Horizon….

• Rechargeable Lithium-air battery• Predicted >1000 Wh/kg• Low cost due to carbon cathode

Source: AIST, Japan

Contacts

Lithium Batteries Tony Hollenkamp, Anand Bhatt

UltraBattery Lan Lam

Flexible Batteries Adam Best

Supercapacitors Tony Pandolfo

Electric Machines Howard Lovatt

V2B and V2G Phillip Paevere

e-mail: firstname.secondname@csiro.au

Carbon anode — good cycle-life but poor specific energy (372 mAh g–1)

from (the present) – lithium-ion battery

to (the future) – re-chargeable lithium-metal battery

Lithium anode — 3800 mAh g-1, but (to date) cycle-life is limited (due to difficulty of stopping dendrite growth)

A

e-e-Li+

Li+

Li+

Li+

Li+

Li+

Li+ Li+

Cathode AnodeCharging

Carbon6C + Li+ + e– C6Li

Metal OxideLiMO2 Li1–xMO2 +

xLi+ + xe– Li metalLi+ + e– Li

Load

eLi+

Li+

Li+

Li+

Li+

Li+

Li+ Li+

Cathode AnodeCharging

e

Safe Rechargeable Lithium-Metal Battery

• Long-standing industry goal has been to replace the carbon-based anode with metallic lithium

• access 10-fold increase in electrode specific energy• device specific energy by 25%• targeting 200 Wh kg-1 (depending on cathode material)

RTIL electrolytes allow reversible Li Li+ + e– • negligible vapour pressure• high thermal stability• low toxicity

OO

F3CS

NS

CF3

OO

N

R

Pyr1x+

TFSI

made possible by Room-Temperature Ionic Liquid Electrolyte

Why do we use ionic liquids?

•……because in conventional electrolytes, the lithium electrode is not able to form a stable interphase at the electrode-electrolyte boundary….•……with the result that dendrites grow short circuits

Avoiding this situation means modifying the solid electrolyte interphase (SEI)

Li|Li+ symmetrical cell - 1.0 mA cm-2• in situ optical imaging

2 mm

1 M LiPF6 in C4H6O3

Li

0 cy

cles

100 cycles 250 cycles

Li

Change in SEI properties when electrolyte is an RTIL

•The SEI is significantly different in the presence of an RTIL

LiF + Li2O

Cu (substrate)Li metal

40 nm

180 nm

LiX + RTIL Li+

P1x+

From XPS Li|Li+ symmetrical cell• 1.0 mA cm-2• 12 min cycle

Li

2 mm

0.5 molal LiTFSI in P13TFSI

Li

500 cycles

CSIRO. FIED – Soldier Technology, London, May 2010

Lithium Metal Batteries – Basic Operation

charge

dischargeLi+ (ion) + e- Li0 (metal) deposited

Poro

us s

epar

ator

deposited Li metal

Current collector

Solid Electrolyte Interphase (SEI) layer formed from electrolyte breakdown products

Anode Cathode

charge

dischargePolymer Polymer+ + e-

Anode:

Cathode:

Li+ ion containing electrolyte

Conducting polymer cathode material

Where is lithium battery research heading?

• Metallic lithium anode offers higher specific energy• Iron phosphate (LiFePO4) cathode delivers good power output, and works well with our latest series of RTILs

However, lower voltage reduces specific energy• high V cathode, e.g., LiNiPO4 (5.1 V vs Li|Li+)

but, demands on electrolyte increase• Increased power density – raise voltage, lower resistance• nano-structuring of electrode materials

• reduce electrode resistance (e.g., Altair – Li4Ti5O12)• reduce electrolyte diffusion paths

• increase conductivity of electrolyte - lithium ion transport

Where is Lithium Battery technology Going?

• Li-ion technology reaching plateau• Rate of further improvement slowing• Limit probably at 200 Wh kg-1 and 1 kW kg-1

• Transition metals in cathodes may limit production• Li-S and Li-air use cheap, abundant C-base• Abundance of Li is not questioned

• Key issues are achievable• Li-S – migration and loss of S as LixS • Li-air – rechargeability of lithium oxides, kineticsLi - S Li -air

Specific Energy (Wh kg-1) 350 – Sion (2007)500 – 600 (pred.)

Up to 5200 (Li2O)

Specific Power (W kg-1) >1000 >1000Cost < Li-ion Depends on catalyst