[Battery Mastery](23) "K-Battery Will Fall into the Valley and Die Without Bridge Technology" Lee Sang-young, Director of Yonsei University Secondary Battery Center

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"If you keep focusing only on next-generation battery technologies, you might end up dying in the middle valley."

On the 2nd, at Yonsei University, Professor Lee Sang-young of the Department of Chemical and Biological Engineering (Director of the Secondary Battery Research Center) emphasized that while next-generation battery research is important, Korean battery academia and companies should not be obsessed with it alone.

Next-generation batteries such as all-solid-state and lithium-sulfur, often called 'dream batteries,' are literally just dreams. Professor Lee stressed that these cannot be the 'magic wand' in the secondary battery market. If we rely solely on next-generation batteries, whose mass production timeline is uncertain, and neglect the bridging technologies that play an intermediate role, we risk falling behind in the fiercely competitive global market. He cited technologies like thick-film electrodes, dry coating, and silicon anode materials as representative 'bridge technologies.'

Professor Lee also advised that Korean battery companies should not compete with China on volume. China already produces tens of times more than Korea in scale. Instead of volume, competition should focus on premium products that yield higher margins. He said Korean battery companies should build a high-end image like Mercedes-Benz or BMW based on advanced technology.

Furthermore, Professor Lee emphasized that to counter China's 'battery human wave tactics,' it is necessary to utilize artificial intelligence (AI) in materials development to accelerate research speed and for the government to make more active and bold investments.

Professor Sang-Young Lee, Department of Chemical and Biomolecular Engineering, Yonsei University

Professor Lee Sang-young earned his bachelor's degree in Industrial Chemistry from Seoul National University and his master's and doctorate degrees in Chemical Engineering from KAIST. He joined LG Chem in 1997 and worked as a senior researcher until 2008, contributing to the early development of secondary battery technology in Korea. During his tenure at LG Chem's Battery Research Institute, he led the development of the 'SRS (Safety Reinforced Separator),' which enhanced safety by coating ceramic on separators. This technology is currently applied to most electric vehicle batteries.

Overview of the ceramic coating separator technology (SRS) developed by Professor Sang-Young Lee. Image source=LG Energy Solution

Afterward, Professor Lee served as a professor in the Department of Energy Chemical Engineering at UNIST and is currently a professor in the Department of Chemical and Biological Engineering at Yonsei University. He concurrently serves as the head professor of the secondary battery contract department at Yonsei University and as the director of the Secondary Battery Research Center, actively conducting industry-academia research with major domestic battery companies such as LG Energy Solution, SK On, and POSCO.

We met Professor Lee Sang-young to hear his views on various issues related to secondary batteries. The following is a summary of the interview with Professor Lee Sang-young.

"Thick-Film Electrode Technology Can Overcome Energy Density Limits"

-How do you evaluate lithium iron phosphate (LFP) batteries?

▲Domestic companies had little interest in LFP until now. While high-nickel batteries can drive 300-400 km on a single charge, LFP only manages about 200 km. It was natural for domestic companies to focus on high-nickel nickel-cobalt-manganese (NCM) batteries to secure driving range. LFP suddenly gained attention for two reasons. First, high-nickel batteries failed the thermal runaway propagation (TP) evaluation by European automakers. LFP was considered an alternative. Second, Tesla ignited a price competition. We are now in a chasm period where universality is more important than technology. LFP is gaining attention not because of superior technology but because the timing fits. The industry cycle has arrived. Since domestic academia and companies are working hard, I expect results to appear soon in LFP as well.

-I heard LFP has also improved technologically.

▲LFP has fundamental limits. No matter how much performance improves, it only reaches about 60-70% of high-nickel batteries in terms of active material. However, if one technology is applied to LFP, the story changes. So far, we have only talked about materials, but there is a way to increase energy density through electrode technology.

NCM and LFP batteries: Terms used to classify lithium-ion batteries based on the type of cathode active materials. NCM uses nickel, cobalt, and manganese, while lithium iron phosphate mainly uses phosphate and iron. NCM is also called ternary battery because it consists of three components. NCM batteries are further classified by composition ratios such as 523, 622, 811, and 9.5. NCM with nickel content above 80% (NCM811 and above) is called high-nickel NCM. NCM 53 and NCM 522 are classified as mid-nickel.

-What is electrode technology?

▲There are two ways to increase energy density. The first is to change the active material, such as NCM or LFP. The second is to make the active material thicker. This is called thick-film electrode technology. Until now, technical limitations made it difficult to adopt thick-film technology.

-Could you explain thick-film electrodes simply?

▲Simply put, if the conventional battery stacked 10 layers each of cathode, anode, and separator, thick-film technology reduces this to 5 layers and makes the active material thicker accordingly. Since the overall volume remains the same, increasing the thickness of the electrode increases energy capacity. This applies to both LFP and NCM. Previously, changing the cathode active material composition was enough to easily increase energy capacity. Cathode technology has now reached 9.5 (mixing nickel, cobalt, manganese in ratios of 9, 0.5, 0.5) and cannot go further. LFP also has the challenge of increasing energy density. By adopting thick-film technology, LFP can increase capacity to levels comparable to NCM523 or NCM622.

Comparison of conventional lithium-ion battery electrode (left) and thin-film electrode (right)

-When can thick-film electrode technology be commercialized?

▲It requires electrode technology, not just powder (the powdered form of active material). It is a battle between binders (adhesives that help active materials and conductive agents adhere well to the current collector) and conductive agents (materials added to improve electronic conductivity of active materials). Since Sony first commercialized lithium-ion batteries in 1991, the binder PVDF (polyvinylidene fluoride) has never changed. Research is ongoing to replace PVDF with other binders. Several groups, including ours, are developing this technology. It is expected to take another 3 to 5 years before companies can mass-produce it.

-What is the outlook for next-generation batteries such as all-solid-state?

▲We also research next-generation batteries, but mass production is not easy. Yet people keep looking for a 'magic wand.' Why are all-solid-state batteries called 'dream batteries'? Because they are truly dreams. Battery developers should not chase only dreams. Balance is necessary. Without bridge technologies, focusing only on next-generation batteries will lead to dying in the middle valley.

Yonsei University and LG Energy Solution signed an industry-academic cooperation agreement for 'Automotive Battery Technology Development' in September 2022. (From left) Myung Jae-min, Dean of the College of Engineering at Yonsei University, and Kim Dong-myung, Vice President of the Automotive Battery Division at LG Energy Solution (currently CEO of LG Energy Solution). Photo by Yonsei University.

-What are some bridge technologies for lithium-ion batteries?

▲Along with thick-film technology, there are dry coating electrodes and silicon anode materials. Dry electrodes refer to technology that applies active materials directly onto the current collector without mixing them into a slurry with solvents. This skips the drying process, saving time and cost significantly. Since no solvents are used, it is environmentally friendly. Tesla plans to apply dry coating to its 4680 cylindrical batteries. Dry electrodes are also foundational technology for thick-film electrodes.

-How do silicon and lithium metal compare as anode materials?

▲Lithium metal was once considered a promising next-generation anode material. But now people are realizing lithium metal is also a 'magic wand.' Lithium metal anodes show good results in labs, but mass production by companies will take considerable time. A conservative approach to lithium metal is appropriate. Silicon, on the other hand, has great potential as an anode material.

-Silicon has swelling issues, right?

▲It is challenging but more commercially viable than lithium metal. Although it varies by company, I heard they are increasing the silicon content significantly. Silicon anodes can greatly increase energy density, enabling new applications. For example, drones require long flight times but have less demand for charge-discharge cycles. Silicon anodes can be commercialized first in such fields, then safety can be gradually enhanced while expanding applications. It is impossible to satisfy all needs at once.

"Next-Generation Batteries Are Not Magic Wands"

-Between all-solid-state and lithium-sulfur, which will be commercialized first?

▲It is hard to say definitively. It depends on the company's choice. The launch decision will be influenced more by business judgment than technological progress. Technologically, lithium-sulfur batteries are slightly ahead. But companies are likely to release all-solid-state batteries first. However, these may not be true all-solid-state batteries. Those released within the next five years will likely contain some electrolyte.

Professor Lee compared all-solid-state batteries to cups and marbles. Conventional lithium-ion batteries are like putting marbles (active materials) in a cup and adding water (electrolyte). All-solid-state batteries replace water with sand. Water wets the marbles evenly, but sand does not, making electrochemical reactions difficult. Also, with electrolyte, marbles expand and contract during charge-discharge but maintain contact with the electrolyte. With sand, cracks form. This causes low yield even if all-solid-state batteries are mass-produced. Professor Lee believes some electrolyte will inevitably remain in all-solid-state batteries for the time being to improve mass production yield.

-What about the semi-solid battery announced by China's CATL?

▲Semi-solid battery is more of a marketing term. It is hard to explain technically, so they named it that way. Chinese companies mix various substances like polymers and oxides into the electrolyte. Since it is hard to define, they call it 'semi-solid.' I heard that CATL's semi-solid batteries also contain electrolyte.

-What is your outlook on sodium-ion batteries?

▲We used to research sodium-ion batteries but stopped. However, with lithium prices soaring, they gained attention. Now that lithium prices have plummeted again, interest has waned. If lithium prices remain low enough, LFP can cover the low-cost market. Ultimately, it depends on lithium prices. Since lithium prices might skyrocket again, developing sodium-ion battery technology is appropriate. But it is not a world-changing technology.

-Next-generation batteries seem like a distant topic.

▲I am not saying we should stop developing next-generation batteries. It is difficult to achieve innovative technology by continuing only lithium-ion batteries. Technologies developed from next-generation battery research can be applied to lithium-ion batteries, enabling quantum leaps. It is better to view next-generation batteries with a long-term perspective. Telling researchers, "If you don't mass-produce within 2-3 years, it's no good," is problematic.

"K-Battery Should Become Like Mercedes-Benz or BMW"

-Chinese companies seem to have caught up a lot with Korea.

▲Korean battery cell companies initially helped grow many Chinese material companies. To produce products quickly, they partnered with Chinese material companies. But this backfired. Now, the dependency is reversed. Chinese material companies nurtured by Korea supply Chinese battery companies. There is also a big gap in research personnel. We have a shortage of researchers and must observe the 52-hour workweek. What one person does here, 100 people do in China. I was surprised to see them working without breaks on Saturdays and Sundays.

-How should Korean companies compete with China?

▲We can no longer compete on volume. We cannot beat China in production volume. I hope Korean battery companies become like BMW or Mercedes-Benz. They should produce premium products at an appropriate scale with high margins. Even in LFP, if margins are right, we should play the game. Even if sales are low, we must lead in technology.

-Don't Chinese companies also invest heavily in R&D?

▲Exactly, now a very complex puzzle game is unfolding. Looking at the English Premier League, all teams have star players and know each other's tactics well. Still, one team wins. The secondary battery market has now entered the Premier League. When Korean battery company executives present to global automakers, they hear, "CATL already gave the same presentation 30 minutes earlier." It's a really tough game. To win, you must come up with something new that surpasses your opponent.

The "Non-Explosive Water-Based Zinc Battery" developed by Professor Sang-Young Lee of Yonsei University and students Won-Young Kim and Hong Kim was selected as one of the "Top 100 National R&D Achievements of 2023" by the Ministry of Science and ICT. Photo by Yonsei University.

-How do you objectively evaluate Chinese technology?

▲Their production scale is several times ahead of ours. While product quality and safety had a slight 2% gap before, they have caught up a lot. There are hardly any gaps now. Our technologies are similar, but their prices are somewhat cheaper. However, China's progress has stalled temporarily due to the US Inflation Reduction Act (IRA). We should use this opportunity well to advance significantly.

-You also use AI in material development.

▲AI is a wonderful technology. Using AI and robots for experiments can greatly shorten material development time. To compete with China, we must also use AI. If China researches with many people even on weekends, we have no choice but to respond by utilizing AI.

-What do you hope from the government?

▲I appreciate the recent expansion of government R&D budgets in the secondary battery field. However, it is still far less than that for semiconductors. When I visited Tsinghua University in China, the most popular major among students was AI, and the second was secondary batteries. This is because they provide full support for secondary batteries. Sometimes, research projects from the Ministry of Trade, Industry and Energy and the Ministry of Science and ICT overlap. It would be good to have a control tower to coordinate and organize these efforts.