Science - USA (2020-08-21)

tion from discarded LIB systems. Accidental

inclusion of LIBs in lead battery recycling has

proven hazardous, and better safety and recy-

clinge protocols are needed.

The range of tools and methods developed

over the past 30 years, both experimentally

and theoretically, are readily applicable to

further develop and elucidate the science

of lead–acid batteries. These topics would

greatly benefit from further engagement

from U.S. National Laboratories and across

academia ( 15 ). Leveraging our current sci-

entific knowledge and an established manu-

facturing industry with admirable safety and

recycling records would ensure

strong economic, technical, and

sciencemag.org SCIENCE

GRAPHIC: MELISSA THOMAS BAUM/

SCIENCE

Perhaps the best prospect for the unuti-
lized potential of lead–acid batteries is elec-
tric grid storage, for which the future market
is estimated to be on the order of trillions
of dollars. For that reason, the low cost of
production and materials, reduced concerns
about battery weight, raw material abun-
dance, recyclability, and ease of manufactur-
ing make it an attractive solution if technical
barriers can be addressed. At a current spot
price below $2/kg and an average theoretical
capacity of 83 ampere hours (Ah)/kg (which
includes H 2 SO 4 weight and the average con-
tribution from Pb and PbO 2 active materials)
that rivals the theoretical capac-
ity of many LIB cathode materi-
als ( 8 ), lead–acid batteries have
the baseline economic potential
to provide energy storage well
within a $20/kWh value ( 9 ).
Despite perceived competition
between lead–acid and LIB tech-
nologies based on energy density
metrics that favor LIB in por-
table applications where size is
an issue ( 10 ), lead–acid batteries
are often better suited to energy
storage applications where cost is
the main concern. In reality, LIB
technology has been more detri-
mental to nickel–metal hydride
and nickel-cadmium battery mar-
kets ( 3 ). The increased cost, small
production rates, and reliance on
scarce materials have limited the
penetration of LIBs in many en-
ergy storage applications.
The inherent concern sur-
rounding lead–acid batteries
is related to the adverse health
and environmental effects of
lead ( 11 ). More effective mitiga-
tion is feasible with application
of known practices, strict gov-
ernment regulations, and im-
proved training and engineering
controls, which would further
increase the already impressive
recycling rate of 99% ( 12 ). Also,
many serious safety and health
concerns exist as part of LIB
manufacturing and operation,
including the carcinogenic po-
tential of Ni and Co oxide com-
ponents of cathode materials,
the production of highly toxic or-
ganofluorophosphate neurotox-
ins as a consequence of thermal
runaway events (battery fire and
explosion) ( 8 , 13 ) and potential
contamination of the environ-
ment with toxic organofluorine
by-products arising from electro-
lytes and additives ( 14 ).

As with any technology, many of the as-

sociated risks can be limited with proper

management of materials, good manufactur-

ing practices, and committed waste manage-

ment. The 99% recycling rate of lead–acid

batteries ( 12 ) and stringent regulations on Pb

environmental emissions greatly minimize

the risk of Pb release to the environment.

Alternatively, the lack of economically fea-

sible recycling solutions to LIB technology in

the short term, combined with the expected

increase in the number of battery cells that

are approaching their end of life, aggravate

the potential for environmental contamina-

INSIGHTS | PERSPECTIVES

Nanostructural

crystal formation

(~10 nm to ~10 μm)

Continuous dissolution

and redeposition of

active materials occur

at the surface of

particles and drive

changes in

microstructure.

Microstructural

and fuid fows

(10 μm to 1 mm)

Charge and discharge

cycles form complex

particle interfaces

between Pb and PbSO 4 or

PbO 2 and PbSO 4 on the

micrometer scale. These

self-structured porous

networks create acid and

water concentration

gradients at the

electrochemical

interfaces.

Water-splitting

reactions

(0.1 to 1 nm)

Charging can also split

water into H 2 and O 2 during

overcharging or at impurity

metal (M) atom.

Macroscopic

components

(centimeters)

The Pb anode and

PbO 2 cathode

electrodes and

separator are

illustrated. Charging

regenerates these

materials.

Negative electrode Separator Positive electrode

panel

Pb+C

grid

Pb paste

PbO 2 paste

Pb-alloy

grid

H 2 SO 4

concentration

Electrode

grid Mber

H 2 O

concentration

PbSO 4

Pb/PbO 2

H 2 O

dilution

H 2 SO 4

dilution

e–

Pb

2H+ H 2

2e–

2H 2 OO 2

4H+ + 4e–

μm)

n

H 20

Discharge

Charge

PbSO 4

H 2 SO 4

2e–

PbO2 (positive)

Pb (negative)

Detail below

Detail

below

M

environmental support for lead–

acid batteries to continue serv-

ing as part of a future portfolio

of energy storage technologies. j

REFERENCES AND NOTES

1. I. Fe l d m a n et al., Environ. Law Rep. 46

(2016).

2. R. Rapier, Forbes 27, 1 ; http://www.
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   battery#6227d028279f (2020).


3. C. Pillot, in 11th International Advanced
   Automotive Battery Conference (2020),
   pp. 1–111; http://www.avicenne.com/pdf/
   Fort_Lauderdale_Tutorial_CPillot
   March2015.pdf.


4. G. J. May, A. Davidson, B. Monahov,
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5. D. Pavlov, Lead-Acid Batteries: Science
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6. D. Rand, Batter. Int. (no. 100), pp. 25–27
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7. A. Hazza, D. Pletcher, R. Wills, Phys.
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8. D. Doughty, E. P. Roth, Electrochem. Soc.
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9. M. S. Ziegler et al., Joule 3 , 2134 (2019).


10. A. J. Bard, R. Parsons, J. Jordan, Standard
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11. G. Flora, D. Gupta, A. Tiwari, Interdiscip.
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12. SmithBucklin Statistics Group, “National
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13. W. Weber et al., J. Chromatogr. A 1394 ,
    128 (2015).


14. K. Liu, Y. Liu, D. Lin, A. Pei, Y. Cui, Sci. Adv.
    4 , eaas9820 (2018).


15. A. Davidson, Consort. Batter. Innov.
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    ahead/.
    ACKNOWLEDGMENTS
    The approach applied to develop structure-
    function correlations was funded by the U.S.
    Department of Energy, Office of Science,
    Office of Basic Energy Sciences, Materials
    Sciences and Engineering Division. The
    research efforts were supported by the Lead
    Battery Science Research Program through
    a Cooperative Research and Development
    Agreement. Use of the Center for Nanoscale
    Materials, an Office of Science user facility,
    was supported by the U.S. Department
    of Energy, Office of Science, Office of
    Basic Energy Sciences, under contract
    no. DE-AC02-06CH11357. We thank E.
    Coleman, D. Strmcnik, M. Zorko, C. Ferels, N.
    Chaudhari, and in memoriam Stefan Djokic
    for support in experiments.
    10.1126/science.abd3352

Multiscale electrochemistry

The technical challenges facing lead–acid batteries are a consequence of the

complex interplay of electrochemical and chemical processes that occur at

multiple length scales. Atomic-scale insight into the processes that are taking

place at electrodes will provide the path toward increased efficiency, lifetime, and

capacity of lead–acid batteries.

924 21 AUGUST 2020 • VOL 369 ISSUE 6506

Published by AAAS