Summary/ Reader Response Draft #3
The article "How an
accidental discovery made this year could change the world." written by
Lockett (April, 2022), introduces the discovery of Lithium-sulfur (Li-S)
batteries and their benefits with it. The Li-S batteries are cheaper to make,
use environmentally friendly materials, can be three times lighter, and have a
low chance of catching fire compared to lithium-ion (Li-ion) batteries, but
Li-S batteries typically have around 1000 charge cycles. Hence, there is a need
to increase its charge cycles. However, according to the author, researchers
find it difficult to increase the charge cycle of Li-S batteries by changing
compounds in the battery’s cathode. “The uncontrolled dendritic and lithium
growth, as well as electrolyte decomposition inherent in lithium metal-based
batteries, cause safety issues and low Coulombic efficiency.” as observed by Li
et al (June 2015). This causes a shuttling effect on Li-S batteries, due to the
dissolution of lithium-polysulfides formed when the battery charges and
discharges. However, the author states that the researchers were able to find a
chemical phase of sulfur that was able to prevent the batteries from degrading.
“Here, we stabilize a rare monoclinic γ-sulfur phase within carbon nanofibers
that enables successful operation of Lithium-Sulfur (Li-S) batteries in
carbonate electrolyte for 4000 cycles (Pai, Singh, Tang, & Kalra, February
2022).” Rahul et al imply that with the introduction of gamma sulfur, they can
stop the reaction that creates polysulfides. “Which stabilizes to 800 mAh·g−1
in the first few cycles and then it remains stable with a small 0.0375% decay
rate over 4000 cycles. The cells exhibit a high capacity of 650 mAh·g−1 even
after the end of 4000 cycles.” Rahul et al mention that the decay rate of the
new Li-S batteries is almost negligible even after 4000 cycles. With this
breakthrough in Li-S batteries, researchers have yet to grasp the understanding
of this phenomenon. Lockett believed that Li-S batteries have the potential to
revolutionize the world. In my opinion, Li-S batteries should replace Li-ion
batteries because sulfur is abundant, it causes lesser ecological harm and is
cheaper. While having a higher energy density means it can be lighter while
storing just as much energy. However, it will take a while before Li-S
batteries replace Li-ion batteries.
Regarding cost, they use
sulfur as a raw material as a by-product of the oil industry instead of
expensive cobalt, which is susceptible to the fragility of global supply chains.
And they can save substantial amounts per unit of power (Merrifield, 2020).
There are three types of Li-ion batteries used in this comparison, Lithium
Cobalt Oxide(LCO), Lithium Nickel Cobalt Manganese Oxide(NMC), and Lithium
Nickel Cobalt Aluminum Oxide(NCA). Sulfur is 243 times cheaper than Nickel and
550 times cheaper than Cobalt.(Benveniste Pérez, Rallo, Canals Casals, Merino,
Amante García,2018). According to research on drones, there might be
significant cost savings with Li-S being available for roughly €72 per kWh,
which is 30% less than comparable Li-ion technology (Merrifield, 2020).
The ecological cost of
rechargeable batteries and the components that make up the batteries is
becoming more and more of a worry. As was stated previously, nickel and cobalt
are frequently found in Li-ion batteries; these minerals are now produced
through extensive mining operations, and the main concern lies in cobalt mining
(Gifford, July 2020). When Cobalt mines are exhausted miners extract cobalt
from communal land, farmland, and homes. Cobalt and other metal mining waste
can contaminate water, air, and soil, reducing crop yields, tainting food and
water, and posing risks to reproductive and respiratory health (Northwestern
University, December 2021). In contrast, sulfur is plentiful to a point that
the US Geographical Survey describes as near limitless and it can be found
being produced on many continents. Furthermore, the environmental agencies,
sulfur does not cause any major health risks (Gifford, July 2020).
The main selling point
of Li-S batteries compared to Li-ion batteries is their higher energy density
per unit weight (Gifford, July 2020). The current Li-S has an energy density of
200 - 500 Wh/kg, while the LCO has 240 Wh/kg, the NMC has 220 Wh/kg and the NCA
has 260 Wh/kg (Benveniste Pérez et al, 2018). Batteries with high energy
density increase the run time of the battery in relation to the size. It can
produce the same amount of energy with a smaller footprint compared to
batteries with lower energy density (Cloud,August 2020). This means that Li-S
batteries can be smaller and lighter, yet last longer without charging.
One of the challenges faced by researchers is being able to
construct Li-S batteries that can reach an energy density of 2600 Wh/kg, even
though they can reach such a high amount of energy density theoretically,
practically they only achieved 500 W/kg. In order to achieve higher energy
density will require high sulfur loading and high sulfur utilization. It hasn’t
been possible to achieve all of these standards simultaneously despite the
researchers’ discussions and formulation of some parameters (Feng et al,2020).
In conclusion, even though the Li-S battery may seem to be better
than the Li-ion battery in many aspects. It appears that Li-S batteries are yet
to be commercialized, while the market for electric vehicles is rising.
Scientists are researching ways to increase energy density and prevent
degradation. If scientists can achieve this, the Li-S battery will replace the
Li-ion battery soon, as the Li-S battery will be more efficient.
References
Benveniste Pérez, G., Rallo, H., Canals Casals,
L., Merino, A., & Amante García, B. (2018). Comparison of the state of
lithium-sulfur and lithium-ion batteries applied to electromobility.
https://upcommons.upc.edu/bitstream/handle/2117/121911/comparison_state.pdf;sequence=1
Cloud, M.(2020, August 21). What is the energy
density of lithium-ion battery? Flux
powerhttps://www.fluxpower.com/blog/what-is-the-energy-density-of-a-lithium-ion-battery
Feng, Y., Wang, G., Ju, J.,
Zhao, Y., Kang, W., Deng, N., & Cheng, B. (2020). Towards high energy
density Li-S batteries with high sulfur loading: From key issues to advanced
strategies. ScienceDirect. pp 320-355
Gifford, S.(2020, July). Lithium-sulfur batteries:
advantages. The Faraday Institution.
https://www.faraday.ac.uk/lis-advantages/
Lockett, W. (2022 ,April 21). An accidental
discovery could change the world. Freethink
https://www.freethink.com/environment/lithium-sulfur-battery
Li, W., Yao, H., Yan, K., Zheng, G., Liang, Z.,
Chiang, Y., & Cui, Y. (2015, June 17).
The synergetic effect of lithium
polysulfide and lithium nitrate to prevent lithium dendrite growth.
Nature Communications
https://www.nature.com/articles/ncomms8436
Merrifield R. (2020, June 05). Cheaper, lighter
and more energy-dense: the promise of lithium sulfur batteries. European
Commission.
Northwestern University. (2021,
December 17). Understanding cobalt’s human cost:Social consequences of green
energy must be assessed in addition to environmental impacts, researchers say. ScienceDaily.
Pai, R., Singh, A., Tang, M., & Kalra, V.
(2022, February 10). Stabilization of gamma sulfur at room temperature to
enable the use of carbonate electrolyte in Li-s batteries. Nature
Communications
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