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Researcher highlights three major lithium-ion battery challenges

Annjil Chong, DIGITIMES, Taipei 0

Lithium-ion battery (LIB) is known to be one of the most promising high-performance energy-storage devices and is widely adopted in electric vehicles (EVs). The global LIB market size is projected to grow at a 12.3% CAGR from US$41.1 billion in 2021 to US$116.6 billion by 2030 based on MarketsandMarkets' research report.

The characteristics of LIBs such as high energy density, lightweight, very low self-discharge rate, and long service life with high coulombic efficiency, making them inimitable for electric-powered vehicles (EVs).

Since the 1980s, Goodenough and his fellow collaborators created a new era for LIBs. The development of EV batteries is divided into three periods by researchers: commercialization in 1991, exploration in 2008, and foresight in 2019.

Sony was the first company that applied lithium-ion rechargeable batteries for its commercial electronic products in 1991. The following is an overview of lithium-based batteries in the EV market:

An overview of various cells and batteries for EV batteries

An overview of various cells and batteries for EV batteries

Notes. C, graphite; Si, silicon; LCO = 1st generation; LiCoO2; LNO = 2nd generation; LiNiO2, LMO = 3rd generation. LiMn2O4; LFP, LiFePO4; NCM, Li[Ni1–x–yCoxMny]O2 (e. g. Li[Ni0.8Co0.1Mn0.1]O2 or Li[Ni0.6Co0.2Mn0.2]O2); NCA, Li[Ni1–x–yCoxAly]O2 (e. g. Li[Ni0.8Co0.15Al0.05]O2); LTO, Li4Ti5O12. Source: Adapted from Liu et al. (2022, p. 4066).

Dr. Mrinalini Mishra, a researcher of battery material as well as an assistant professor of Sustainability Science and Engineering at Tunghai University, shares her insights on EV battery materials.

During the interview, she highlighted three major LIB challenges, namely dendrite formation, the cost of materials, and the exhaustion of lithium reserves. The following are the interview details:

Challenge I: Dendrite formation

The word "dendrite" is derived from the Greek word for tree (δένδρον déndron). It means a multi-branched structure and is a common form of metal solidification, including lithium. For instance, either from the molten state or during electrodeposition.

Although the mechanism of lithium dendrite growth is still understudied, researchers categorized lithium dendrites into two groups:

Group 1: Needle-like, whisker-like, and filament-like structures

Group 2: Moss-like, bush-like, and tree-like structures

Below is a schematic of the electrochemical reaction inside a LIB cell consisting of the cathode, electrolyte, and anode.

Schematic of lithium-ion cell working principle

Schematic of lithium-ion cell working principle

Source: Adapted from Zhao et al. (2022, p. 4). Credit: DIGITIMES Asia

During discharge, lithium ions are released from the anode, travel through the electrolyte, and intercalated in the cathode. Whereas, during charging, charged lithium ions are gathered inside the anode after oxidation reactions occurred in the cathode.

In other words, electrodes and electrolytes are the most crucial components of batteries. There are three types of electrolytes: liquid-based, polymer-based, and all-solid-state.

According to Mishra, dendrite formation, mostly related to the liquid-electrolyte, remains a bottleneck in the EV battery industry. It induces a poor cycle life, low Coulombic efficiency, and even safety concerns. To tackle this problem, Mishra and her team substituted the organic liquid electrolyte with a solid-state electrolyte.

Lithium lanthanum zirconium oxide (LLZO)-based oxide was chosen in their research project because the material has "high lithium-ion conductivity of ~1 mS cm-1 1 at 25-degree Celsius, excellent chemical stability with metallic lithium, and wide electrochemical stability windows of > 5 V," stated in her journal article.

Apart from the material, it is known that the cubic phase is better. Mishra and her team would like to freeze that phase. Various dopants such as aluminum or gallium were used to stabilize the cubic phase of LLZO.

"When we say doping, it means you try to add small amounts of other elements into the compound," she explained. "The result was the cubic phase of LLZO has a better lithium conductivity. That's the reason why we wanted to freeze or hold the LLZO in the cubic phase."

Challenge II: Lithium prices surging

Ambrose and Kendal estimated that the commercial demand for lithium is expected to grow exponentially reaching up to 4.5 million tons per year by 2100 in their article, titled, "Understanding the future of lithium: Part 1, resource model."

Not only does the electronic industry will continue to be the main consumer of lithium, but also the automobile industry where the focus has been shifted to mass production of EVs.

Due to the rapid demand for lithium, prices are spiking. Taking lithium carbonate price as an example, the material had soared by approximately 500% from 12 months prior by the end of January 2022, according to International Banker.

Higher lithium costs will transmit to higher EV-battery prices, spreading to carmakers consequently. In March alone, for example, Tesla hiked its EV prices in the Chinese market at least 3 times. CATL also revised prices for some of its products, according to Jiemian.com. "We need to bring down the cost," Mishra emphasized.

"Cost depends on a lot of things. The reserve, for example, how much active material reserve we have," she explained. "It's not always about lithium, you have graphite. There are many kinds of carbon materials that are being tested. In performance-wise, maybe they are good. But practically, will they be cost-effective? That's a big question."

Challenge III: The exhaustion of lithium reserves

Significant economic lithium occurrences are found in Argentina, Australia, the USA, Chile, Bolivia, and China. Researchers categorized them into three deposit types:

(1) lithium-rich brines

(2) hard-rock pegmatitic lithium ores

(3) lithium-rich clays or sediment-hosted deposits

The following is a table of lithium resources across the globe:

Global lithium resources

Country

Resource type

Identified resources (Unit: Mt Li)

Canada

Pegmatites or clays

1.7

USA

*Pegmatites or clays

*Brine

6.8

Portugal

Pegmatites or clays

0.25

Brazil

Pegmatites or clays

0.4

Bolivia

Brine

21

Argentina

Brine

17

Zimbabwe

Pegmatites or clays

0.54

China

*Pegmatites or clays

*Brine

4.5

Australia

Pegmatites or clays

6.3

Source: Tabelin, C. B. et al. (2021, p. 5). Data compiled by DIGITIMES Asia, April 2022.

Mishra said, "We always want to improve battery performance, we always want better capacity…, but apart from the fact, the major reason we are moving to other materials is that lithium reserves are going down."

She continued, "Materials that are currently being tested in the laboratory are sodium, potassium, aluminum. I think lithium is the most mature one. We don't know how good the other materials will be until they can be applied commercially. That's my feeling."

Mishra predicted that the next generation of large-scale commercial EV batteries will be sodium-ion technologies. CATL, for instance, has unveiled the first generation of sodium-ion batteries as an alternative to LIBs. This technology offers an energy density of up to 160 Wh kg-1 and can be charged to 80% in 15 minutes at room temperature.

She explained, "From a researcher's perspective, I just feel that more research has already been done and people know it better as compared to the aluminum or potassium or other battery materials that are being tried right now. Instead of lithium-ion batteries, people are trying lithium metal batteries. But again, the problem is that we don't have enough lithium reserves. So, we will move to other materials and probably the next one is sodium."

Other promising technologies are as follows:

Future EV batteries

Technology

Description

Dual-ion battery (DIB)

Promising for stationary energy storage instead of traction batteries for EVs

Dual-carbon battery

Dual-graphite/carbon battery

A subcategory of dual-ion battery

Aluminum–graphite DIB

High reversibility and high energy density

Dual-carbon-based

potassium DIB

Good comprehensive performance

Zinc-air battery

Delivering a stunning 210-mW/cm2 high peak power density as well as outstanding cycling stability.

Source: Adapted from Liu et al. (2022, p. 4068) and Zhao et al. (2022, p. 4). Data compiled by DIGITIMES Asia, April 2022.

And this raises the question of "how about recycling used lithium"?

Mishra replied, "That's an interesting topic. To consider practicality, is it cost-effective? Is it sustainable? Throwing used lithium away, of course, is not sustainable. But, taking it back and using it in the battery, will it be sustainable? Or taking it back and using it for something else, would be more sustainable. That part, we still don't know."

About Dr. Mrinalini Mishra

Mrinalini Mishra, Ph.D., currently is an assistant professor at Tunghai University, Taiwan. She has written 24 scholarly papers (15 are the first author, the rest are co-authored) on topics including photocatalytic hydrogen generation, atomic layer deposition, electrophoretic deposition, and MAX phase. Her most recent journal article is Tuning the Crystallinity and Coverage of SiO2–ZnIn2S4 Core-Shell Nanoparticles for Efficient Hydrogen Generation (ACS Applied Materials & Interfaces 13 (3), 4043-4050).

References

Ambrose, H. & Kendall, A. (2019). Understanding the future of lithium: Part 1, resource model. Journal of Industrial Ecology, 24(1), pp. 80-89.

Liu, W., Placke, T. & Chau, K. T. (2022). Overview of batteries and battery management for electric vehicles. Energy Report, 8, pp. 4058-4084.

Mishra, M., Hsu, C. W., Chandra Rath, P., Patra, J., Lai, H. Z., Chang, T. L., Wang, C-Y., Wu, T. Y., Lee, T. C., Chang, J-K. (2020). Ga-doped lithium lanthanum zirconium oxide electrolyte for solid-state Li batteries. Electrochim Acta, 353(136536).

Tabelin, C. B., Dallas, J., Cassanova, S., Pelech, T., Bournival, G., Saydam, S., & Canbulat, I. (2021). Towards a low-carbon society: A review of lithium resource availability, challenges and innovations in mining, extraction and recycling, and future perspectives. Minerals Engineering, 163(106743).

Zhao, G., Wang, X., & Negnevitsky, M. (2022). Connecting battery technologies for electric vehicles from battery materials to management. iScience, 25(2), pp. 1-39.

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