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Thick Electrode Batteries: Principles, Opportunities, and Challenges

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Abstract and Figures

The ever‐growing portable electronics and electric vehicle markets heavily influence the technological revolution of lithium batteries (LBs) toward higher energy densities for longer standby times or driving range. Thick electrode designs can substantially improve the electrode active material loading by minimizing the inactive component ratio at the device level, providing a great platform for enhancing the overall energy density of LBs. However, extensive efforts are still needed to address the challenges that accompany the increase in electrode thickness, not limited to sluggish charge kinetics and electrode mechanical instability. In this review, the principles and the recent developments in the fabrication of thick electrodes that focus on low‐tortuosity structural designs for rapid charge transport and integrated cell configuration for improved energy density, cell stability, and durability are summarized. Advanced thick electrode designs for application in emerging battery chemistries such as lithium metal electrodes, solid state electrolytes, and lithium–air batteries are also discussed with a perspective on their future opportunities and challenges. Finally, suggestions on the future directions of thick electrode battery development and research are suggested.
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PROGRESS REPORT
1901457 (1 of 19) © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Thick Electrode Batteries: Principles, Opportunities,
and Challenges
Yudi Kuang, Chaoji Chen,* Dylan Kirsch, and Liangbing Hu*
DOI: 10.1002/aenm.201901457
Recent reviews on LBs have provided
a good overview of the developments of
high energy density LBs based on diverse
battery chemistries.[3–6] It is believed that
the energy density of current LBs can
be improved up to 300–350 Wh kg1 in
a short time by using high-nickel (Ni)
content cathodes, silicon (Si) dominant
anodes, and higher voltage electrolytes,
but further progress is needed to achieve
an acceptable lifetime for practical appli-
cation.[7] In regards to long term goals,
continued research and development
(R&D) of next-generation LBs is necessary
to meet the Battery500 Project target of a
cell-level specific energy of 500 Wh kg1,[8]
which necessitates a combination of both
innovative battery chemistries (such as
lithium (Li)-sulfur (S), Li-O2, Li-CO2, and
so on), and cell configurations (improved
active material ratio and cell integration).[9]
However, the majority of current research
efforts are dedicated to the R&D of bat-
tery materials while battery configurational design is relatively
overlooked. Interestingly, with the progress in the develop-
ment of water-in-salt electrolyte and the corresponding battery
chemistry, aqueous LIBs are also possible to meet the Battery
500 Project target. A representative work is the aqueous LIBs
that has been recently reported by Yang et al. which achieves
a stable operation potential of 4.2 V and energy density of
460 Wh kg1.[10] It is great progress but worthy noting that
the energy density calculation is based on the mass of anode
and cathode. When the mass of the electrolyte is included, the
full-cell energy density is dropped to 304 Wh kg1, revealing
the important role of battery configurational design.
Structural engineering provides a feasible and universal way
to further improve the energy density of LBs without changing
the fundamental battery chemistries. Since the battery’s energy
only comes from the electrically active materials in the elec-
trodes, the core principle for the novel structural design of bat-
teries is to minimize the ratio of inactive components while
maintaining or improving battery performance per mass or
volume of active material. Common strategies include the opti-
mization of battery packaging with thinner, more robust mate-
rials, the reduction of electrode porosity with a higher packing
density and increased electrolyte uptake, and the utilization
of thick electrodes. The first is relatively hard to improve in a
short time and would require a breakthrough in battery pack-
aging materials with carefully evaluated cost and safety param-
eters. As for the reduction of electrolyte, it is also difficult to
The ever-growing portable electronics and electric vehicle markets heavily
influence the technological revolution of lithium batteries (LBs) toward higher
energy densities for longer standby times or driving range. Thick electrode
designs can substantially improve the electrode active material loading by
minimizing the inactive component ratio at the device level, providing a
great platform for enhancing the overall energy density of LBs. However,
extensive efforts are still needed to address the challenges that accompany
the increase in electrode thickness, not limited to sluggish charge kinetics
and electrode mechanical instability. In this review, the principles and the
recent developments in the fabrication of thick electrodes that focus on low-
tortuosity structural designs for rapid charge transport and integrated cell
configuration for improved energy density, cell stability, and durability are
summarized. Advanced thick electrode designs for application in emerging
battery chemistries such as lithium metal electrodes, solid state electrolytes,
and lithium–air batteries are also discussed with a perspective on their future
opportunities and challenges. Finally, suggestions on the future directions of
thick electrode battery development and research are suggested.
Electrode Materials
Dr. Y. Kuang, Dr. C. Chen, D. Kirsch, Prof. L. Hu
Department of Materials Science and Engineering
University of Maryland
College Park, MD 20742, USA
E-mail: chencj@umd.edu; binghu@umd.edu
The ORCID identification number(s) for the author(s) of this article
can be found under https://doi.org/10.1002/aenm.201901457.
1. Introduction
Aided by the past 30 years of development, lithium-ion bat-
teries (LIBs) that are based on layered metal oxide cathodes and
graphite anodes are now approaching their specific energy den-
sity limits with a currently achieved cell-level gravimetric energy
density of 250 Wh kg1 at a price of 200–300 US $ kWh1.[1,2]
Global efforts are required for the development of advanced
lithium batteries (LBs) in order to meet the goals of
350 Wh kg1 and 125 US $ kWh1 by 2022, as projected by the
US Department of Energy (DOE) Vehicle Technologies Office,
for the fabrication of competitive electric vehicles (EVs). In gen-
eral, the methods toward achieving higher energy density LBs
can be summarized in two ways: 1) the development of novel
battery chemistries with higher specific capacity and 2) the
exploration of advanced battery configurations with increased
electrochemical active material ratio via electrode architecture
engineering.
Adv. Energy Mater. 2019, 9, 1901457
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