A Lead Monoxide Precursor of High Surface-Area for Lead-Acid Battery Paste

R Vasant Kumar

Department of Materials Science

University of Cambridge, UK

Acknowledgements

Seref Sonmez, Vega Kotzeva, Jiakuan Yang, Lilia Sanchez, Richard Darby, Yingjun Liu, David Zou, of Department of Materials Science

Lei Wang, Nigel Williams of the Business School

Maggie Wilkinson & Zlatka Stoeva of Cambridge Enterprise

A Schematic Cut-Away of Lead Battery

Table 1 Range of Compositions from a dry lead battery paste

Material Wt %

Lead sulphate 55-65

Lead dioxide 15-40

Lead monoxide 5-25

Metallic lead 1-5

Carbon black, plastics, fibres, other sulphates

1-4

Current Method - Pyrometallurgy

*For 10,000 tpy plantCapital: $4-5MEnergy: 14,000MWH*Independent Consultants

Battery Manufacture

Lead is then chemically oxidised to PbO for the battery industry

PbO is electrochemically reduced to Pb and oxidised to PbO2 to make anode and cathode

Lead containing Organic

Crystalline Compounds

PbO Precursor

New

A new process for recycling lead battery waste

→

↓↑

→

Special Leaching/Crystallization Process

Lead Battery

Combustion/Calcination Process

Manufacturing Lead Battery

Waste Battery

Paste

New Paste

Patent: PCT/GB2007/004222; WO2008/056125RV Kumar, S Sonmez and V Kotzeva

A new process for recycling lead battery waste

→

Paste

Pb GridHeat Energy from pasterecycling

New Grid

New Paste directly from paste recycling

Kettle

Waste Battery

New lead Battery

Green PB Recycling Process

Patent: PCT/GB2007/004222; WO2008/056125RV Kumar, S Sonmez, V Kotzeva

Leaching

Combustion-Calcination

SpentLead grid

MetallicLead

Energy

0

1

2

3

4

5

6

0 10 20 30 40 50 60

Time / mins

Tem

pera

ture

Ris

e / °

C

1.5 : 1 1.25 : 1 1 : 1

Leaching of battery paste PbO and PbO2

Ratio ofPaste/reagent

10

20

30

40

50

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Reaction time(min)

Tem

pera

ture

(℃

) Lead (II) oxide

Lead (IV) dioxide

Lead sulfate

1

1.5

2

2.5

3

3.5

4

4.5

0 10 20 30 40 50 60

Time / mins

pH

1.5 : 1 1.25 : 1 1 : 1

pH vs time for varying paste/reagent ratio

5 15 25 35 45 55 65

2 θ(degree)

Inte

nsi

ty(a

.u.) A

B

C

D

XRD Pattern of A: Standard Lead citrate; B: from PbO; C: fromPbO2 and D: from PbSO4

Lead organic crystallites of Lead citrate (A) from PbO and PbO2

SEM images of Lead Citrate (B) from PbSO4

Precursors Ideal weight loss

Fromdehydrating

weight loss

(TGA)

Ideal weight loss

For decomposition to PbO

weight loss

after exothermic peak of TGA

weight loss

calcined at 350 for ℃1h

Precursor I[Pb(C6H6O7)]·H2O 4.3% 4.20% 46.3% 49.8% 48.2%

Precursor II[Pb(C6H6O7)]·H2O 4.3% 4.20% 46.3% 49.8% 49.0%

Precursor III[Pb3(C6H6O7)2]·3H2O

5.1% 5.50% 36.6% 38.3% 37.5%

Combustion-Calcination of Lead citrates in Air

334.01°C

2000J/g

167.76°C

151.79°C238.7J/g

285.09°C

-5

0

5

10

15

20

25

He

at

Flo

w (W

/g)

0

20

40

60

80

100

120

We

igh

t (%)

40 80 120 160 200 240 280 320 360 400

Temperature (°C)

Sample: 20070423PbO-airSize: 7.8140 mgMethod: Ramp

DSC-TGAFile: C:...\yj231\20070423\20070423PbO-air.002Operator: yj231Run Date: 23-Apr-2007 14:50Instrument: SDT Q600 V8.2 Build 100

Exo Up Universal V4.3A TA Instruments

Wt loss and heat produced on decomposing Pb citrate (A)

357.91°C2427J/g

117.77°C

284.16°C

9.869%

-5

0

5

10

15

20

25

He

at

Flo

w (W

/g)

0

20

40

60

80

100

120

We

igh

t (%)

40 80 120 160 200 240 280 320 360 400

Temperature (°C)

Sample: 20070411PbSO4airSize: 15.9840 mgMethod: Ramp

DSC-TGAFile: C:...\DSC\20070411-PbSO4air-analysis.001Operator: rs489Run Date: 11-Apr-2007 14:27Instrument: SDT Q600 V8.2 Build 100

Exo Up Universal V4.3A TA Instruments

Wt loss and heat produced from lead citrate (B)

10 20 30 40 50 60 70 80 90

2 θ(degree)

Inte

nsity

(a.u

.)

300℃

350℃

400℃

450℃

Pb

PbO

Mixture of α and β PbO and metallic Pb – can be controlledto varying ratios

Heat Produced

Combustion-calcination of lead citrates can generate thermal energy of 2 kJ/ g of lead battery paste

The Raceway Adiabatic Flame Temperature is over 1500K!

This energy is equivalent to 550 kWh/kg of paste!

PbO morphology after combustion-calcination

SEM

TEM

Spongy PbO Agglomerated PbO

Skeletal PbO

Additives during leaching to control PbO morphology

Lead citrate PbO

Addition of C-fibre to PbO precursor

FEGSEM – Each fibre is coated FEGSEM – Each fibre is coated with PbOwith PbO

Physical Properties of PbO

Free Pb: 0 to 20 % Crystal structure: α/β ratio: 0.05 to 1 Crystal size: 20 – 100 nm Particle average size: 1 – 5 μm Specific surface area (BET) m2/g: 2.4 to 5.5 Acid absorption (mg H2SO4/ g oxide): 270 –

530

Preliminary Electrochemical Testing

First discharge capacity in the 130 – 160 mAh/g of PbO

Increase in discharge capacity with no of cycles up to 8-10 cycles and then remained constant to 50 cycles

Further work is ongoing

-5.0 -2.5 0 2.5-0.10

-0.05

0

0.05

0.10

E (Volts)

I (A

mps/

cm2 )

A

BC

DE

A: PbO /PbSO4 reduction to PbB: Pb oxidation to PbSO4

C: PbSO4 oxidation to PbO2

D: PbO2 reduction to PbSO4

E: PbSO4 reduction to Pb

The Green PB Process

For 10,000 tpy plantCapital: $1-1.5 MEnergy: 1750 MWH

5000 MWhEnergy available

Conclusions

New method for directly recovering PbO from spent battery paste

Many control variables available to vary physical properties of PbO product

Promising preliminary results Thank You