Zinc-ion rechargeable
batteries, also known as ZIBs, use zinc ions as the charge carrier. In ZIBs Zn is
used as the anode, Zn-intercalating materials as the cathode, and a
Zn-containing electrolyte is also used. In addition to zinc-ion batteries zinc-halide
batteries are being developed for energy storage. Wikipedia notes:
“Both aqueous and non-aqueous electrolytes are being
investigated as candidates for ZIBs. Zinc salts using the TFSI or triflate
anions have been considered for both aqueous and non-aqueous electrolytes. Zinc
sulfate and alkaline KOH-based aqueous electrolytes have also been considered.”
Several cathode
materials have been explored for ZIBs, including “gamma-, delta-type MnO2,
copper hexacyanoferrate, bismuth oxide, layer sulfides and Prussian blue
analogues.” Manganese oxides remain the best choice for cathodic material.
For the past five
years or so zinc-io batteries have been considered to be one of the main
contenders to replace lithium-ion batteries in many applications. New
discoveries are aiding that ability significantly and commercialization is on
the near horizon.
Lithium-ion
batteries have many advantages. Lithium’s position on the periodic table of
elements ensures its position in terms of low-atomic weight which transfers to
lower battery weight. That reflects its superior energy density. That, along
with the fact that lithium is already established as the “incumbent” of energy
storage, ensures that it will retain its market share. However, many energy
storage applications do not require superior energy density but can be compared
instead by cost. Applications like EVs must consider vehicle space and vehicle
weight but battery storage in utility power systems usually does not need to
consider those factors. Ryan Brown, co-founder and CEO of Salient Energy wrote
in a January 2021 article in Power Magazine:
“It has become increasingly clear that any alternative to
lithium-ion batteries needs to adopt standard manufacturing processes to allow
for a rapid and low-cost scale-up. So far, the zinc-ion battery (Figure 1) is
the only non-lithium technology that can adopt lithium-ion’s manufacturing
process to make an attractive solution for renewable energy storage,
particularly for its compatibility along with other advantages.”
He is correct to
point out that standardization in manufacturing is a key to improving costs and
enabling scale-up. It was very advantageous for supermaterials company Lyten as
they adapted a lithium-ion production facility to make lithium-sulfur battery
components. He explains very well the challenges and goals of battery development and manufacturing, and how zinc-ion batteries can complement and replace some
lithium-ion batteries. He notes that there is especially potential for zinc-ion
batteries to replace lithium-ion batteries in stationary energy storage. There
is a link to the article in the references of this post. Other important
potential applications for zinc-ion batteries include their use in maritime
settings, critical infrastructure, and densely populated urban areas.
Both LIBs and ZIBs utilize intercalation where
ions react at both electrodes and travel between them through an electrolyte. ZIBs
use a water-based electrolyte. During discharge, metal at the anode dissolves
into the electrolyte as zinc or lithium ions. Simultaneously, zinc or lithium ions
are absorbed into the cathode from the electrolyte. This process is reversed
during charge. Brown also writes:
“In fact, zinc-ion batteries can improve on lithium-ion
manufacturing processes. Lithium’s violent reactivity with water requires many
of its production steps to take place in a highly controlled atmosphere that
makes the process more costly, and more complicated. As a water-based battery,
zinc-ion does not have this constraint.”
“Additionally, zinc-ion batteries do not require
formation cycling at the end of life. This means they can more quickly move
from the manufacturing line to the customers. This ability to use lithium-ion
manufacturing means that the production of zinc-ion batteries can be rapidly
and inexpensively scaled-up.”
The water-based
electrolytes of ZIBs make them non-flammable compared to LIBs which are banned
in some places like dense urban centers due to safety concerns. Lithium-ion
fires are not that uncommon and can be difficult to extinguish.
Brown thinks that
with a cheap and readily available domestic supply for ZIBs, they could scale up quickly and as economies-of-scale arise in manufacturing, they will become
cheaper than lithium-ion batteries.
A few drawbacks of ZIBs include dendrite formation which can result in failure and corrosion. Salient Energy noted in September 2023 (via Solar Builder) that they have made significant improvements to mitigate both of those risks. They also announced that they had increased cell-level energy density by 150% which is quite an improvement. They also “developed a more stable aqueous electrolyte that prevents corrosion and limits electrolyte pH fluctuations, ensuring longer cycle-life and durability of the battery.” Salient uses domestically abundant (zinc is 100 times more abundant globally than lithium), relatively inexpensive, and readily available zinc and manganese. Another drawback of zinc batteries is that they lose more energy during charging and discharging than lithium batteries do. Some relevant information is shown below from Salient Energy's website.
Solar Builder reported
in May 2022 that Salient Energy:
“…formalized a partnership with Horton World Solutions
(HWS), a sustainable homebuilder, which is hosting the first in-field
demonstration of Salient’s zinc-ion storage system. HWS plans to include the
system in over 200,000 homes.”
The CEO of HWS
joined the board of advisors for Salient Energy, noticing that the partnership
was a win-win. He noted that lithium-ion home storage systems had to design
extra steps for safety and that they often encountered supply shortages and
other supply chain issues. ZIBs could solve both of these concerns.
Researchers at
the University of South Wales (UNSW) Sydney have also developed ways to solve
the rechargeability challenges of what they call aqueous rechargeable zinc
battery (AZB) technology. This includes zinc-ion batteries and zinc-halide
batteries. (A company in Pittsburgh. Pennsylvania, Eos, got a $400 million loan
in 2023 to expand manufacturing of their zinc-halide batteries that offer a 50-100%
longer life than LIBs.) They were able to add a “very small concentration (1
volume%) of non-toxic additive molecules in the battery electrolyte” in
order to prevent dendrite formation and electrode corrosion. They estimate that
this could result in a 5 to 20 times increase in battery life. While ZIBs will
still be prioritized where safety is a major issue, their ability to better
compete with lithium-ion tech in performance means they could one day replace
lithium in many applications. UNSW also notes:
“AZBs that use an aqueous salt solution electrolyte
emerge as promising alternatives due to safety, raw material abundance,
affordability, and competitive energy densities.”
“The use of the high-capacity metallic zinc anode gives
AZBs an energy density boost, and its safe chemistry means it is potentially
fully recyclable. Ambient manufacturing is another significant advantage.”
“The UNSW team continues to work on developing the zinc
anode, cathode, and cell components toward developing battery cell prototypes.
It is estimated that a fully developed technology would cost consumers around
one-third to one-fourth the price of the present-day Li-ion systems.”
That is a pretty amazing
potential cost-benefit, although it is unclear when such a benefit could
materialize.
In September Swedish
company Enerpoly opened the world’s first zinc-ion megafactory which is expected
to begin production in 2025. Production is expected to reach 100MWh annually in
2026. According to a press release from the company:
In July 2024, Enerpoly expanded its manufacturing
capacity by adding cutting-edge dry electrode manufacturing equipment to its
megafactory.
“The end-to-end battery production line and process
development capabilities will allow Enerpoly to accelerate production
capabilities; lower costs, waste, and energy consumption; and deliver more
sustainable energy storage solutions.”
The aqueous
zinc-ion battery (AZIB) is poised to continue to improve. Researchers at
Australia’s Flinders University have developed an aqueous zinc-ion battery
(AZIB) using a modified polymer. The polymer is used at the cathode. According
to a September 2024 article in Interesting Engineering:
“They used a commercially available poly(methyl vinyl
ether-alt-maleic anhydride) polymer, also called poly(MVE-alt-MA)) polymer.
Next, they modified this polymer with 4-amino-TEMPO, to create the final
product, a radical polymer known as PTEMPO.
“Our research is building conductivity using nitroxide
radical polymer cathodes made from cheap commercial polymer and optimized the
battery performance using low-cost additives…”
Researchers at the
Korea Institute of Energy Research (KIER) have also discovered a way to solve
the problem of dendrite formation in ZIBs using low-cost processes and
materials like copper oxide. These improvements are helping to get ZIBs closer
to the capacity retention of LIBs after a comparable number of cycles.
According to a September article in Interesting Engineering:
“The research team successfully controlled zinc
deposition to achieve a world-leading capacity of 60 mAh/cm². They also
demonstrated the technology’s durability through extensive battery performance
tests exceeding 3,000 cycles and confirmed its applicability to large-area
electrodes measuring 64 cm².”
“Like regular copper, copper oxide promotes the initial
growth of zinc and guides its deposition. Additionally, copper oxide has
optimized conductivity for depositing zinc in a uniform distribution, allowing
for more efficient deposition compared to regular copper.”
The end result is
a battery with 10 times the cycle life as previous ZIBs and a much more stable
battery.
A study published
in October 2024 in Nature Communications explored zinc dendrite formation in AZIBs.
The researchers identified the chemical and kinetic controls on dendrite
formation and explored ways to reduce their formation. Corrosion leads to dendrite
formation. They note their results of successfully decreasing dendrite
formation in the abstract:
“The presence of a dense and stable SEI film is critical
for inhibiting the formation and growth of Zn dendrites. By adding 50 mM lithium chloride (LiCl) as an
electrolyte additive, we successfully construct a dense and stable SEI film
composed of Li2S2O7 and Li2CO3, which significantly improves cycling
performance. Moreover, the symmetric cell achieves a prolonged cycle life of up
to 3900 h with the
incorporation of 5% 12-crown-4 additives. This work offers a strategy for
in-situ observation and analysis of Zn dendrite formation mechanisms and
provides an effective approach for designing high-performance Zn-ion batteries.”
They found that
hydrogen gas disrupts the stability of the SEI film and promotes the formation
of zinc oxide (ZnO)/zinc sulfate hydroxide hydrate (ZSH), fostering the growth
of Zn dendrite. Thus, zinc oxide is a chemical byproduct that leads to
corrosion and dendrite formation. Thus, the goal became to limit the chemical
formation of zinc oxide. The resultant decrease in dendrite abundance and
length after adding the electrolyte additive is shown below.
A late October 2024
article in Interesting Engineering notes that German researchers at the Technical
University of Munich (TUM) have utilized a porous organic polymer to massively
increase the cycle life of ZIBs to 100,000 cycles. This improvement is also
based on reducing the formation of dendrites. The researchers utilized:
“… a crystalline 2D porous fluorinated covalent organic
framework, referred to as (TpBD-2F) on the ZIB anode, which serves as a
protective layer. The material creates one-dimensional fluorinated nanochannels
through which zinc ions can easily flow while repelling water molecules.”
“This prevents the formation of needle-like structures in
the battery, commonly referred to as zinc densities, while also stopping
reactions that trigger hydrogen production.”
“The protective film also enabled stable
plating/stripping in symmetric cells for over 1200 h at 2 mA cm−2, the
researchers said in a paper published earlier this month.”
The paper’s
abstract summarizes the results:
“…the reversibility of zinc anodes is constrained by
unchecked dendrite proliferation and parasitic side reactions. To minimize
these adverse effects, a highly oriented, crystalline 2D porous fluorinated
covalent organic framework (denoted as TpBD-2F) thin film is in situ
synthesized on the Zn anode as a protective layer. The zincophilic and
hydrophobic TpBD-2F provides numerous 1D fluorinated nanochannels, which
facilitate the hopping/transfer of Zn2+ and repel H2O infiltration, thus
regulating Zn2+ flux and inhibiting interfacial corrosion. The resulting
TpBD-2F protective film enabled stable plating/stripping in symmetric cells for
over 1200 h at 2 mA cm−2. Furthermore, assembled full cells (Zn-ion capacitors)
deliver an ultra-long cycling life of over 100 000 cycles at a current density
of 5 A g−1, outperforming nearly all reported porous crystalline materials.”
In summary, I conclude that zinc-ion tech is poised to replace a significant amount of lithium-ion tech in the years ahead. How much depends on how these new discoveries in corrosion inhibition and dendrite formation reduction can be integrated into existing manufacturing and how well economies-of-scale can be achieved to make costs better than just competitive. There is no doubt that ZIBs will take some market share from LIBs and become preferred for certain applications, What remains to be seen is how well they can compete performance-wise with LIBs for other apps. It does not yet appear that they will be preferred for EVs, mainly due to energy density but that could change at some point in the future.
References:
Zinc
battery reaches impressive 100,000-cycle life with German innovation. Ameya
Paleja. Interesting Engineering. October 29, 2024. Zinc battery reaches impressive
100,000-cycle life with German innovation
New
zinc batteries offer 10x more life, safer than lithium energy devices. Prabhat
Ranjan Mishra. Interesting Engineering. September 4, 2024. Dendrite suppression leads to 10
times increase in zinc battery life
Affordable
zinc-ion battery built using office laminator can replace lithium cells. Rupendra
Brahambhatt. Interesting Engineering. September 20, 2024. Affordable,
safe zinc-ion battery made possible with modified polymer
World’s
first zinc-ion battery mega-factory targets 100 MWh annual output. Mrigakshi
Dixit. Interesting Engineering. September 3, 2024. Enerpoly opens world's first zinc-ion
battery mega-factory in Sweden
Zinc-ion
batteries: Materials, mechanisms, and applications. Jun Ming, Jing Guo, Chuan
Xia, Wenxi Wang, and Husam N. Alshareef. Materials Science and Engineering: R:
Reports. Volume 135, January 2019, Pages 58-84. Zinc-ion batteries: Materials,
mechanisms, and applications - ScienceDirect
Zinc-ion
battery. Wikipedia. Zinc-ion battery - Wikipedia
Zinc-ion
Batteries Are a Scalable Alternative to Lithium-ion. Ryan Brown. Salient
Energy. Power Magazine. September 4, 2021. Zinc-ion Batteries Are a Scalable
Alternative to Lithium-ion
Zinc
batteries that offer an alternative to lithium just got a big boost. Casey
Crownhart. MIT Technology Review. September 6, 2023. Zinc batteries that offer an
alternative to lithium just got a big boost | MIT Technology Review
Unraveling
chemical origins of dendrite formation in zinc-ion batteries via in
situ/operando X-ray spectroscopy and imaging. Hongliu Dai, Tianxiao Sun, Jigang
Zhou, Jian Wang, Zhangsen Chen, Gaixia Zhang & Shuhui Sun. Nature
Communications volume 15, Article number: 8577 (October 2024). Unraveling chemical origins of dendrite
formation in zinc-ion batteries via in situ/operando X-ray spectroscopy and
imaging | Nature Communications
Salient
Energy says zinc-ion battery close to market after latest breakthroughs. Chris
Crowell. Solar Builder. September 11, 2023. Salient
Energy says zinc-ion battery close to market after latest breakthroughs | Solar
Builder
Homebuilder
HWS to include Salient’s zinc-ion batteries in over 200,000 homes. Chris
Crowell. Solar Builder. May 16, 2022. Homebuilder
HWS to include Salient's zinc-ion batteries in over 200,000 homes | Solar
Builder
A
major boost for clean energy storage: prolonging aqueous zinc battery
rechargeability. Diane Merlot. UNSW Sydney. January 3, 2024. A
major boost for clean energy storage: prolonging aqueous zinc battery
rechargeability
Converting
a low-cost industrial polymer into organic cathodes for high mass-loading
aqueous zinc-ion batteries. Nanduni S.W. Gamage, Yanlin Shi, Chanaka J.
Mudugamuwa, Jesús Santos-Peña, David A. Lewis, Justin M. Chalker, and Zhongfan
Jia. Energy Storage Materials. Volume 72, September 2024, 103731. Converting
a low-cost industrial polymer into organic cathodes for high mass-loading
aqueous zinc-ion batteries - ScienceDirect
Ion-Transport
Kinetics and Interface Stability Augmentation of Zinc Anodes Based on
Fluorinated Covalent Organic Framework Thin Films. Da Lei, Wenzhe Shang,
Lyuyang Cheng, Lyuyang Cheng, Poonam, Waldemar Kaiser, Pritam Banerjee, Suo Tu,
Olivier Henrotte, Jinsheng Zhang, Alessio Gagliardi, Joerg Jinschek, Emiliano
Cortés … et, al. First published: 13 October 2024. Advanced Energy Materials. Ion‐Transport
Kinetics and Interface Stability Augmentation of Zinc Anodes Based on
Fluorinated Covalent Organic Framework Thin Films - Lei - Advanced Energy
Materials - Wiley Online Library
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