LiFSI vs. LiPF6 in Li-ion Battery Electrolytes

2021-11-11 | Jerry Huang

Will LiFSI replace LiPF6 in Li-ion battery electrolytes? Using the new salt lithium bis(fluorosulfonyl)imide (LiFSI) rather than lithium hexafluorophosphate (LiPF6) as an electrolyte improves the performance of Li-ion batteries with silicon anodes, according to a paper published in the Journal of the American Chemical Society by researchers in Europe.

Lithium bis(fluorosulfonyl)imide, commonly referred to as LiFSI, has the molecular formula F2LiNO4S2 and CAS number 171611-11-3. LiFSI appears to be white powder, with a molecular weight of 187.07, and a melting point between 124-128°C (255-262.4°F).

Compared to LiPF6, LiFSI not only enhances thermal stability in li-ion battery technology, but also gives better performance in terms of electrical conductivity, cycle life, and low-temperature. However, LiFSI may have certain corrosive effects on aluminum foil. Some academic papers show that the corrosion of aluminum foil mainly comes from FSI-ions in LiFSI, but this problem can be solved by additives such as fluorine-containing passivation aluminum foil additives.

The trend is quite certain that LiFSI is becoming one of the mainstream lithium salts for next generation electrolytes. Currently, ternary lithium batteries and LFP batteries are constantly being improved and iterated generation after generation that have higher requirements for energy density, high and low-temperature performances, cycle life, and charge and discharge rate performances.

Due to high technical difficulty in mass production and high cost, LiFSI has not been directly used as a solute lithium salt, but as an additive mixed with lithium hexafluorophosphate (LiPF6) for use in the electrolytes of power li-ion batteries especially. For example, LG Chem has been using LiFSI as an additive in their electrolytes for quite some time. As technology improves, more and more LiFSI will be added to electrolytes. It is believed that the cost of LiFSI will be lowered further with the scaling up of mass production. And as time passes, LiFSI has the potential to replace LiPF6 as the main lithium salt for power li-ion battery electrolytes.

Sources:

• https://www.greencarcongress.com/2013/06/lifsi-20130626.html

Will the lithium hexafluorophosphate (LiPF6) market boom or crash in 2021?

2021-11-01 | Jerry Huang

Lithium hexafluorophosphate (LiPF6) is a key raw material in today's technology, for lithium-ion battery electrolytes of lithium-ion power batteries, lithium-ion energy storage batteries and other consumer electronics' li-ion batteries. Along with the boom of EV industry, the li-ion power battery segment consumes the largest portion of LiPF6 in the market.

Since September 2020, the sales of new energy vehicles have increased substantially, which has driven the sales of lithium hexafluorophosphate to increase. It is estimated that the lithium hexafluorophosphate demand in the power battery segment will be about 66,000 tons in 2021 and about 238,000 tons in 2025, with an average annual growth rate of about 40%.

According to data from January to September 2021, China's accumulative capacity of LFP battery in EV installation is about 45.38GWh, and the accumulative capacity of ternary batteries is about 49.70GWh. It is expected that the annual total capacity of LFP battery in EV installation will exceed that of ternary in 2021, with high year-on-year growth rate expected.

As of October 18, the price of lithium hexafluorophosphate was 520,000 yuan/ton, and it has risen by nearly 500% in 2021 with its price at 107,000 yuan/ton only at the beginning of this year, setting a new record high since June 2017. Lithium hexafluorophosphate and electrolyte additives have clearly become one of the materials with the highest growth rates this year. The strong demand in the market is expected to continue, and it is currently in short supply.

Will lithium carbonate continue to increase in price?

2021-10-18 | Jerry Huang

Let's look at the supply-demand situations of lithium carbonate in order to evaluate its price trends.

Battery-Grade Lithium Carbonate (Li2CO3)

The main demanding areas of battery-grade lithium carbonate are currently from the preparation of NMC ternary cathode materials, lithium cobalt oxide and part of lithium iron phosphate (LFP).

In 2021, the overall growth rate of NMC532 and NMC622 has been low, comparing to Ni-rich ternary materials and LFP. In H2 of 2021, it is estimated that the demand for battery-grade lithium carbonate from production of NMC ternary cathode materials will be approximately 48,470 tons, an increase of only 2.4% from the previous H2 of 2020.

Due to the negative impact of the pandemic, the export volume of China's consumer electronics has decreased significantly, with little increase in its domestic market. The demand for battery grade lithium carbonate from lithium cobalt oxide manufacturers has declined. In H2 of 2021, it is estimated that the lithium carbonate demand from this area will be about 16,737 tons, a decrease of 9.7% from H2 of 2020.

In terms of demand from LFP materials, many mainstream power-type LFP material plants currently use battery-grade lithium carbonate as their main lithium source (accounting for about 30%) to ensure the quality of LFP power battery for EV market. Under the imbalance of supply and demand in the power LFP battery market, enterprises have begun to expand their production capacity largely. In 2021 H2, the demand for battery-grade lithium carbonate from this field is expected to be approximately 14,788 tons, an increase of 30% from H2 of 2020.

Industrial-Grade lithium Carbonate (Li2CO3)

The main demanding area of industrial-grade lithium carbonate are from production of LFP material average quality, lithium manganate, lithium hexafluorophosphate and some traditional industries.

In terms of demand from LFP material production, since H2 of 2020, sales of A00-class EV models have been growing rapidly in China market, resulting heavy demand of average quality power LFP battery. At the same time, some mid-end and high-end models, such as Tesla Model Y and Model 3, have also launched their own LFP-powered versions. Besides, the demand for LFP batteries in the energy storage and two-wheelers market is also increasing. Currently the demand of industrial-grade (including quasi-battery-grade) lithium carbonate from LFP material production accounts for about 70%, comparing to that of battery-grade lithium carbonate. In 2021 H2, the demand for industrial-grade lithium carbonate from this field is expected to be approximately 34,505 tons, an increase of 30% from 2020 H2.

As for demand from lithium manganate production, due to fewer orders of consumer electronics and two-wheelers overseas, the demand of lithium manganate cathode material is not strong. At the same time, as the price of lithium salts continues to rise, manufacturers have great pressure on cost increase and some of them reduced its output. Therefore, the demand for industrial-grade lithium carbonate continues to shrink. There was an obvious output reduction of LMO materials early this year in Spring Festival. In 2021 H2 however, the demand for industrial-grade lithium carbonate from this field is expected to be approximately 11,900 tons, a slight increase of 8% from the previous 2020 H2.

With regard to the demand from preparing lithium hexafluorophosphate, along with the hot sales in the EV market, the domestic electrolyte output has increased significantly, and the demand for lithium hexafluorophosphate (LiPF6) has increased greatly as well. In 2021 H2, it is estimated that the demand for industrial grade lithium carbonate from this area is about 11,236 tons, an increase of 40% from 2020 H2.

The remaining demand for industrial-grade lithium carbonate are from productions of metal lithium, causticizing processed lithium hydroxide and pharmaceuticals, accounted for about 26% of its overall demand, with a slight increase.

In conclusion, the overall demand for lithium carbonate continues to increase rapidly. However the overall output of lithium carbonate is shrinking in 2021 H2 due to decreased supply of spodumene, despite an increased supply from brine sources domestic and overseas. Prices for lithium carbonate are most likely to increase if the above estimates stand correct.

Is LiTFSI the best choice to improve low temperature performance in HEV cells?

2021-10-11 | Jerry Huang

Generally it is believed that the higher the proportion of hard carbon (above 15%) is coated to the anode of a li-ion battery, the better its conductivity. However, we must make it clear that the compaction of pure hard carbon pole pieces is about 1.15 g/cc. If more hard carbon is coated to the graphite material, the compaction density of the entire pole piece will be reduced (without increasing the space between the core material layers). It can only achieve 1.2g/cc at most. At the same time, the hard carbon may be compacted and the performance may not be fully utilized. Therefore, it is necessary to choose different ratio of hard carbon coating according to application scenarios.

It is common sense that the anode material is usually unevenly stressed and irregular. The larger the particle size of the material, the greater the internal resistance. Therefore, if hard carbon coating is used, although battery cycle life can be significantly expanded, its calendar life is relatively poor (battery cell capacity reduces greatly within storage of 6 months).

Is LiTFSI the best choice to improve low temperature performance in HEV cells?

Obviously, hard carbon-coated anode material is not enough to solve the pain points of poor performance at low-temperature; some other materials must be improved, such as electrolytes. Electrolytes are an important part of lithium-ion batteries, and they not only determine the migration rate of Li+ lithium ions in the liquid phase, but also play a key role in the formation of SEI film. At the same time, the existing electrolytes have a lower dielectric constant, so that lithium ions can attract more solvent molecules and release them during desolvation, causing greater system entropy changes and higher temperature coefficients (TCs). Therefore, it is important to find a modification method that has a smaller entropy change during desolvation, a lower temperature coefficient, and is less affected by the electrolyte concentration. Currently, there are two ways to improve low temperature performance through electrolytes:

1. Improve the low-temperature conductivity of electrolytes by optimizing the composition of the solvent. The low-temperature performance of electrolytes is determined by the low-temperature eutectic point. If the melting point is too high, the electrolyte is likely to crystallize out at low temperatures, which will seriously affect the conductivity of electrolytes and ultimately lead to failure of the lithium battery. EC ethylene carbonate is an important solvent component of the electrolyte. Its melting point is 36°C. At low temperatures, its solubility is likely to decrease and even crystals are precipitated in electrolytes. By adding low-melting and low-viscosity components to dilute and reduce the EC content of the solvent, the viscosity and eutectic point of the electrolyte can be effectively reduced at low temperatures, and the conductivity of electrolytes can be improved. In addition, domestic and overseas studies have also shown that the use of chain carboxylic acid, ethyl acetate, ethyl propionate, methyl acetate, and methyl butyrate as the electrolyte co-solvent is beneficial to the improvement of the low-temperature conductivity of electrolytes and greatly improves the low temperature performance of the battery. Significant progress has been made in this area.
2. The use of new additives to improve the properties of the SEI film makes it conducive to the conduction of lithium ions at low temperatures. Electrolyte salt is one of the important components of electrolytes, and it is also a key factor to obtain excellent low temperature performance. Since 2021, the electrolyte salt used on a large scale is lithium hexafluorophosphate. The SEI film that is easily formed after aging has a large impedance, resulting in poor low-temperature performance. Therefore, the development of a new type of lithium salt becomes urgent. Lithium tetrafluoroborate and lithium difluorooxalate borate (LiODFB), as lithium salts for electrolyte, have also brought high conductivity under high and low temperatures, so that the lithium ion battery exhibits excellent electrochemical performance in a wide temperature range.

As a new type of non-aqueous lithium salt, LiTFSI has high thermal stability, a small degree of association of anion and cation, and high solubility and dissociation in carbonate systems. At low temperatures, the high conductivity and low charge transfer resistance of the LiFSI system electrolyte ensure its low temperature performance. Mandal Et Al. has used LiTFSI as a lithium salt and EC/DMC/EMC/pC (mass ratio 15:37:38:10) as the basic solvent for electrolyte; and the result showed that the electrolyte still has a high conductivity of 2mScm-1 at -40°C. Therefore, LiTFSI is regarded as the most promising electrolyte that can replace lithium hexafluorophosphate, and is also regarded as an alternative for the transition to an era of solid electrolytes.

According to Wikipedia, Lithium bis(trifluoromethanesulfonyl)imide, often simply referred to as LiTFSI, is a hydrophilic salt with the chemical formula LiC2F6NO4S2. LiTFSI is a white crystal or powder that can be used as an organic electrolyte lithium salt for lithium-ion batteries, which makes the electrolyte showing high electrochemical stability and conductivity. It is commonly used as Li-ion source in electrolytes for Li-ion batteries as a safer alternative to commonly used lithium hexafluorophosphate. It is made up of one Li cation and a bistriflimide anion. Because of its very high solubility in water (> 21 m), LiTFSI has been used as lithium salt in water-in-salt electrolytes for aqueous lithium-ion batteries.

LiTFSI can be obtained by the reaction of bis(trifluoromethylsulfonyl)imide and lithium hydroxide or lithium carbonate in an aqueous solution, and the anhydrous can be obtained by vacuum drying at 110 °C: LiOH + HNTf2 → LiNTf2 + H2O

Lithium bis(trifluoromethylsulfonyl)imide can be used to prepare electrolytes for lithium batteries and as a new Lewis acid catalyst in rare earth; it is used to prepare chiral imidazolium salts by anion replacement reaction of corresponding trifluoromethanesulfonates. This product is an important fluorine-containing organic ion compound, which is used in secondary lithium batteries, super capacitor Chemicalbook, aluminum electrolytic capacitors, high-performance non-aqueous electrolyte materials and as new high-efficiency catalyst. Its basic uses are as follows:

1. Lithium batteries
2. Ionic liquids
3. Antistatic
4. Medicine (much less common)

However, an R&D engineer from China once said: “LiTFSI is mainly used as an additive in current electrolytes and will not be used as the main salt alone. In addition, even if it is used as an additive, the formulated electrolyte has better performance than other electrolytes. LiTFSI Electrolyte is much more expensive than usual types of electrolytes, so LiTFSI is not added, if there is no special requirements on electrolyte performance."

It is believed that in some application scenarios, there are substantial requirements for high-power batteries, scenarios such as electric forklifts and AGVs. As concerns on durability and attributes of production tools, it is also necessary to solve the problems of cycle life and low-temperature performance at one time. Therefore, research and development on next-generation electrolytes will continue. But it is still a multi-dimensional concern and competition of performance, cost, and safety; and the markets will eventually make their own choices.

References:

1. Zheng, Honghe; Qu, Qunting; Zhang, Li; Liu, Gao; Battaglia, Vincent (2012). "Hard carbon: a promising lithium-ion battery anode for high temperature applications with ionic electrolyte". RSC Advances. Royal Society of Chemistry. (11): 4904–4912. doi:10.1039/C2RA20536J. Retrieved 2020-08-15.
2. Kamiyama, Azusa; Kubota, Kei; Nakano, Takeshi; Fujimura, Shun; Shiraishi, Soshi; Tsukada, Hidehiko; Komaba, Shinichi (2020-01-27). "High-Capacity Hard Carbon Synthesized from Macroporous Phenolic Resin for Sodium-Ion and Potassium-Ion Battery". ACS Applied Energy Materials. American Chemical Society. 3: 135–140. doi:10.1021/acsaem.9b01972.
3. Khosravi, Mohsen; Bashirpour, Neda; Nematpour, Fatemeh (2013-11-01). "Synthesis of Hard Carbon as Anode Material for Lithium Ion Battery". Advanced Materials Research. 829: 922–926. doi:10.4028/www.scientific.net/AMR.829.922. S2CID 95359308. Retrieved 2020-08-15.
4. Goriparti, Subrahmanyam; Miele, Ermanno; De Angelis, Francesco; Di Fabrizio, Enzo; Proietti Zaccaria, Remo; Capiglia, Claudio (2014). "Review on recent progress of nanostructured anode materials for Li-ion batteries". Journal of Power Sources. 257: 421–443. Bibcode:2014JPS...257..421G. doi:10.1016/j.jpowsour.2013.11.103.
5. Irisarri, E; Ponrouch, A; Palacín, MR (2015). "Review-Hard Carbon Negative Electrode Materials for Sodium-Ion Battteries". Journal of the Electrochemical Society. 162: A2476. doi:10.1149/2.0091514jes.
6. Dou, Xinwei; Hasa, Ivana; Saurel, Damien; Vaalma, Christoph; Wu, Liming; Buchholz, Daniel; Bresser, Dominic; Komaba, Shinichi; Passerini, Stefano (2019). "Hard carbons for sodium-ion batteries: Structure, analysis, sustainability, and electrochemistry". Materials Today. 23: 87–104. doi:10.1016/j.mattod.2018.12.040

LFP Battery Surpassed Ternary in EV Installation in July

2021-08-12 | Jerry Huang

In China market, the domestic power battery output totaled 17.4GWh in July 2021, an increase of 185.3% year-on-year and an increase of 14.2% month-on-month. Among them, the output of ternary battery is 8.0GWh, accounting for 46.0% of the total output, with an increase of 144.0% year-on-year, and an increase of 8.6% month-on-month; the output of lithium iron phosphate (LFP) batteries is 9.3GWh, accounting for 53.8% of the total output, with an increase of 236.2% year-on-year, and an increase of 20.0% month-on-month.

From January to July this year, the total output of power batteries was 92.1GWh, an increase of 210.9% year-on-year. Among them, the cumulative output of ternary batteries was 44.8GWh, an increase of 148.2% year-on-year, accounting for 48.7% of the total output; the cumulative output of LFP batteries was 47.0GWh, an increase of 310.6% year-on-year, accounting for 51.1% of the total output.

With regard to battery capacity installed by EV industry, the total installation capacity of ternary batteries in July was 5.5GWh, accounting for 48.7%, an increase of 67.5% year-on-year, but a decrease of 8.2% month-on-month; the total installation of LFP batteries was 5.8GWh, accounting for 51.3%, an increase 235.5% year-on-year and an increase of 13.4% month-on-month.

From January to July, the cumulative capacity of ternary batteries installed in EV was 35.6GWh, an increase of 124.3% year-on-year, accounting for 55.8% of the total volume installed; the cumulative capacity of LFP batteries was 28.0GWh, an increase of 333.0% year-on-year, accounting for 43.9% of the total volume installed.

Source: SPIR News

Output of LFP Battery Exceeds That of Ternary Lithium Battery in May

2021-07-06 | Jerry Huang

According to data from the China Automotive Power Battery Industry Innovation Alliance, in May 2021, China's power battery output totaled 13.8GWh, a year-on-year increase of 165.8%. Among them, the output of lithium iron phosphate (LFP) batteries was 8.8GWh in May, accounting for 63.6% of all battery output, an increase of 317.3% year-on-year, and an increase of 41.6% month-on-month; the output of ternary lithium batteries was 5.0GWh, accounting for 36.2% of the total output, an increase of 62.9% year-on-year, but a 25.4% decrease from the previous month. Due to the surge in May this year, the output of LFP batteries has surpassed that of ternary lithium batteries for the first time since 2018. The cumulative output of LFP battery was 29.9GWh from January to May this year, accounting for 50.3% of the total output; while the cumulative output of ternary lithium batteries was 29.5GWh at the same period, accounting for 49.6%.

In terms of battery capacity installed by EV industry, share of LFP batteries is temporarily less than ternary lithium batteries still. In May, the installation capacity of LFP batteries increased by 458.6% year-on-year to 4.5 GWh, and the installed capacity of ternary batteries increased by 95.3% year-on-year to 5.2 GWh. In the first five months of this year, China’s installation of power battery capacity totaled 41.4GWh in EV, a year-on-year increase of 223.9%. Among them, the cumulative volume of ternary lithium batteries was 24.2GWh, an increase of 151.7% year-on-year, accounting for 58.5% of the total batteries installed; the cumulative volume of LFP batteries was 17.1GWh, an increase of 456.6% year-on-year, accounting for 41.3% of the total batteries installed. However, it is worth noting that the current growth rate of LFP batteries in production and EV installation far exceeds that of ternary lithium batteries. If this continues, the EV installation of LFP batteries in June may exceed that of ternary lithium batteries as well.

Output of Nickel-rich Cathode Materials Increases Significantly

2021-07-05 | Jerry Huang

According to statistics from ICCSINO, the market share of nickel-rich ternary materials (811&NCA type) in 2020 has increased to 22% approximately in the field of overall ternary materials, a significant increase compared to that of in 2019. While this year in 2021, total output of ternary cathode materials turns out to be about 106,400 tons in China in Q1+April, of which nickel-rich materials accounted for 32.7%. The monthly output in April reached a new level in a record of 10,450 tons, a year-on-year increase of 309.8%. The growth rate far exceeded expectations. Nickel-rich ternary materials gradually became the main battlefield of the future ternary materials.

In fact, in the past few years, the high-nickelization of ternary cathode materials has not been smooth in China market. Although the trend already appeared in the market in 2018, nickel-rich materials were not well accepted in the Chinese new energy market due to technical and safety issues. In 2019, market share of nickel-rich material was only about 13%. However, with the booming demand in overseas markets in the past two years and the popularity of nickel-rich batteries by major car companies, the shipments of China’s nickel-rich cathode materials have been steadily increasing.

Here is a chart showing shares of different ternary cathode materials' output in China market in Q1+April over recent years. Source: ICCSINO.COM

Direct Lithium Extraction Technology Revealed

2021-05-30 | Jerry Huang

A "Salt Lake Raw Brine Efficient Lithium Extraction Technology" presented by Minmetals Salt Lake Co., Ltd, was approved positive by experts from the Chinese Academy of Engineering in Beijing On May 26th, 2021.

The technology is claimed to be featured as:

1. Salt field spreading is omitted, production period/term is reduced from 2 years into 20 days;
2. Optimized combination of the membrane system has been improved;
3. Device efficiency has been improved; fully automatic control of simultaneous separation of sodium, magnesium, potassium, deboration and extraction of lithium is achieved;
4. Production capacity has been increased by 1.5 times;
5. Power consumption has been reduced by more than 30%;
6. Zero emissions of wasted water, gas or residue;
7. Overall cost is reduced by more than 10%, especially the total lithium extraction rate has been increased 2x, reaching more than 70%, comparing to current technology.

It is claimed that brine’s service life can be doubled and extended. At the same time, product quality has been further improved to match battery grades lithium salts for Li-ion battery industry.

Source: SPIR News

Cost of An NMC622 Pouch Cell by Region

2021-05-13 | Jerry Huang

Currently the costs of various li-ion battery cells differ in different regions or countries. Here is a chart of Manufactured cost of an NMC 622 pouch cell by region, as an example. Source: BloombergNEF

The battery wars continue, with more action in South Asia. The Indian government has just approved subsidies for cell manufacturing.

Indian government claimed that India’s reduction goal of Green House Gas (GHS) emissions will be in line with India’s commitment to combat climate change.

https://lnkd.in/dfGJ3Ca

The subsidies include multipliers for performance, and could be worth up to $27/kWh at the cell level!

BloombergNEF estimates that India is already the lowest cost country for manufacturing cells. The subsidies could reduce costs to $65/kWh!

Even if raw material prices continue to increase there will be more downward pressure on cell and pack prices, says Mr. James Frith.

Li-ion Battery Industry Is Shaping The Lithium Industry

2021-04-16 | Jerry Huang

Lithium ion battery and EV industry occupy 32% of world’s lithium consumption in 2015, with ceramics and glass, lubricating grease, medicine, metallurgy and polymers being 68% at the same time; while it is estimated that Lithium ion battery will consume 67% of world’s lithium supply right after six years by the end of 2021.

Source: Benchmark Mineral Intelligence, Lithium Forecast Database.

In China market, the lithium ion battery industry consumes approximately 80% of lithium hydroxide in 2018 already, according to data from Lithium Research Institute. As a result, the lithium industry has been shaped by lithium ion battery and EV industry since 2015/2016; and lithium refinery has experienced a big shift of thinking for a dominant application in lithium ion battery and electric vehicles out of various end use.

With increasing investment in lithium ion battery, such as NCM, NCA and LFP, especially the resurgence of LFP battery in China market, the demand of battery grade lithium carbonate, being 80% of all grades lithium carbonate's output in 2020, is estimated to continue its growth in the future.