(618d) Synthesis and Complex Electrochemistry of Manganese Dioxide in Alkaline Batteries

normal"> 107%;font-family:" times new roman>Synthesis and Complex
Electrochemistry of Manganese Dioxide in Alkaline Batteries

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mso-bidi-font-size:11.0pt;line-height:107%;font-family:" times new roman>Manganese
Dioxide (MnO₂) is one of the cheapest and most abundant materials
available on earth. It is used in a number of applications like catalysis,
water purification, lithium-ion batteries and many more. However, it is
commonly known to most as a AA primary battery, where
it is used to power remote controls, clocks, etc. MnO₂ is used as a
cathode in these primary batteries because of its high theoretical capacity of
617mAh/g, where it is delivered through a two electron reaction mechanism in
alkaline electrolyte. The first electron reaction has been known to deliver
~308mAh/g through a solid-state proton insertion, while the second electron
reaction has been known to deliver the remaining half through a
dissolution-precipitation reaction. For many years MnO₂ was
considered to be electrochemically irreversible because of the breakdown of the
crystal structure during the first electron reaction and the deleterious side-reactions
during the second electron reaction that resulted in the formation of an
inactive substance called hausmannite (Mn₃O₄).^1,2
These major problems relegated this energy dense cathode to the realm of
primary batteries, which otherwise would have been used for many important
applications like grid energy storage.

mso-bidi-font-size:11.0pt;line-height:107%;font-family:" times new roman>In
this talk, we will present different ways of accessing the theoretical second
electron capacity (617mAh/g) of MnO₂ for over 3000 cycles, where the
use of dopants like bismuth oxide and copper, removal of hydrophobic binders
like Teflon, use of high surface area carbon and maintaining a porous electrode
architecture are extremely important.^3-5 We will present the diverse
and complex electrochemistry of MnO₂ that take place with the addition
of bismuth oxide and copper as complexation and intercalation reactions are
added with the solid-state and dissolution-precipitation reactions on the
account of the tendency of bismuth and copper to enhance the redox activity of
MnO₂.⁶ We will also show comprehensive combinatorial
cyclic voltammetry and impedance analysis, where the roles of bismuth and
copper will be further elucidated, and remark on the potential regions where
the complexation and intercalation regions exist in the MnO₂
electrochemistry. For the first time we will show real time microscopy images
and video of the formation and deformation of MnO₂ through
dissolution-precipitation reactions.^5,6 We
will also report on the role of high surface area carbon and binder on MnO₂
electrochemistry, where we find that they affect the electrode architecture and
porosity, which turn out to be very important for the dissolution-precipitation
reactions. Finally, we will present our perspective on the current
understanding of MnO₂ electrochemical reactions based on the
aforementioned and other advanced characterizations that we have performed.  

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mso-bidi-font-size:11.0pt;line-height:107%;font-family:" times new roman>Figure.
Potentiodynamic cycling of MnO₂ showing
its diverse and complex electrochemistry. Top part is the cyclic voltammetry
(CV) scan of the first cycle which shows the conversion of γ-MnO₂
to δ-MnO₂. Bottom part is the CV scan after the first cycle,
which shows the electrochemistry of δ-MnO₂ with Bi and Cu
additives.

normal"> 107%;font-family:" times new roman>Funding:

mso-bidi-font-size:11.0pt;line-height:107%;font-family:" times new roman>This
work was supported by the New York State Research and Development Authority
(NYSERDA) under Project Number 58068 and US Department of Energy ARPA-E under
award number DE AR0000150.

normal"> 107%;font-family:" times new roman>References:

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2016,  bold">321, 135-142

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Huang, J.; Yadav, G. G.; Gallaway, J. W.; Wei, X.; Nyce, M.; Banerjee, S., Electrochemistry Communications,
2017, 81, 136-140 font-family:" times new roman>

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Yadav, G. G.; Gallaway, J. W.; Turney,
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Nat. Commun., 2017, 8, 14424

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Yadav, G. G.; Wei, X.; Huang, J.; Gallaway, J. W.; Turney, D. E.; Nyce, M.; Secor, J.; Banerjee, S., J. Mater. Chem. A, 2017, 5 (30),
15845-15854

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Yadav, G. G.; Wei, X.; Gallaway, J. W.; Chaudhry, Z.;
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