[Battery+] ‘Solid-state batteries are exaggerated’

The idea is so simple but powerful.

By replacing inflammable liquid solution inside conventional lithium-ion batteries with solid materials, solid-state batteries would eliminate fire concerns, have a greater life span, support faster charging, offer a lighter weight and provide greater capacity.

The race has already begun among rising solid-state battery startups and established lithium-ion players, including the South Korean trio LG Energy Solution, SK Innovation and Samsung SDI, to debut the game-changing cell first.

Dongwha Enterprise, a battery materials supplier based in Incheon, is one of the candidates for Samsung SDI’s solid-state road map, tasked with developing solid electrolytes, the key for making the “dream” battery real. Samsung SDI aims to develop prototypes of solid-state batteries by 2025 and commercialize them by 2027, a time frame shared by its bigger rival LG Energy Solution.

Despite hype surrounding solid-state batteries, Kim Jeong-soo, head of research and development at Dongwha Enterprise, counters with a more conservative view. Solid-state batteries, realized only in labs so far, would face a tall task to become a commercial commodity as the lithium-ion equivalents are now, or the mainstay of the future energy storage, he said in a recent interview with The Korea Herald. 


Price is king


Inside a lithium-ion cell, the contents are soaked in a liquid solution called electrolytes. Through this liquid, lithium ions travel back and forth between cathodes, the positive terminal, and anodes, the negative terminal. This is the basic mechanism of how lithium-ion batteries are charged and discharged.

When lithium-ion batteries repeat the charge-discharge process over time, lithium ions slowly pile up to form a needlelike structure called dendrites. These dendrites elongate long enough to penetrate separators -- thin plastic walls dividing cathodes and anodes -- and cause short circuits.

By replacing inflammable liquid electrolytes with solid electrolytes made of ceramic materials, solid-state batteries become fireproof. Even in cases of short circuits, solid electrolytes heat up but do not catch fire -- like stones generally do not catch fire.

However, solid electrolytes are extremely difficult to manufacture and therefore would lack price competitiveness for commercialization, according to Kim, who has spent more than 30 years in one of Korea’s big three battery firms and is regarded as one of the nation’s first-generation battery researchers.

“Solid electrolytes can’t be exposed to the atmosphere or moisture during their manufacturing process or they degenerate and release toxic gases. It took us a whole week just to manufacture dozens of grams of solid electrolyte samples inside a glovebox filled with argon. Mass production would require the entire facility to be filled with argon, so it isn’t easy,” he said, drawing from his experience of testing solid sulfide as battery electrolytes.

The market price of liquid electrolytes stands at $6 to $7 per kilogram. One kilogram of solid electrolytes made with solid sulfide costs at least tens of thousands of dollars inside labs. Even if mass-produced, it would be 10 times more expensive, he said.

“If solid electrolytes are produced 8 kilograms in bulk per month, the price would be more than $1,000 per kilogram. If produced 1,000 tons -- not kilograms -- per month, they would still be 10 times more expensive than liquid electrolytes,” Kim said.

Dongwha Enterprise, whose main business is the production of liquid electrolytes for Samsung SDI, is not alone in using sulfide as the electrolyte material. SolidPower, CATL and a joint venture between Toyota and Panasonic are all developing solid-state batteries filled with solid sulfide electrolytes, as they offer the highest lithium ion conductivity. Simply put, lithium ions travel best through solid sulfide electrolytes compared to other known candidates.

However, solid sulfide electrolytes are highly unstable and chemically vulnerable when exposed to the atmosphere. Therefore, solid sulfide electrolytes have to be manufactured inside sealed-off containers filled with argon -- an inert, colorless and odorless gas used especially in welding, lasers and electric bulbs.

Lithium-ion cartel


Above all, solid sulfide electrolytes require completely new raw materials that are not widely used in existing industries and therefore face difficulties in achieving economies of scale.

“To manufacture solid sulfide electrolytes, you need special reagents, which can only be purchased from US-based chemicals company Sigma-Aldrich. One hundred grams of reagents costs thousands of dollars, driving up the price of solid sulfide electrolytes to tens of thousands of dollars per kilogram,” Kim said.

“Another key raw material is lithium sulfide. This raw material is so expensive -- about tens of thousands of dollars per kilogram -- because no one uses it. Lithium sulfide is a mineral that is manufactured at extreme heat between 700 and 800 degrees Celsius, but who’s going to make large investments and establish enormous manufacturing facilities when there’s no demand guaranteed at the moment?”

According to Kim, 170 grams of lithium sulfide is used to produce 1 kilogram of solid sulfide electrolytes.

Most importantly, Kim questions exactly how pricey solid-state batteries can challenge the decadeslong hegemony of lithium-ion batteries, mentioning several failed attempts made in the past by cheaper alternatives, exemplified by sodium batteries.

“General Electric once tried to replace lithium-ion batteries with low-cost sodium-nickel-chloride batteries, building a 600-megawatt-hour plant in the US in 2012. However, GE eventually had to shut down the factory three years later because no matter how cheap sodium batteries were, they weren’t cheap enough to compete against lithium-ion batteries,” Kim said.

The raw material of sodium batteries is salt, which is cheaper than lithium. But the lithium-ion industry has what sodium batteries lack: massive infrastructure and ecosystem spread out all across the world.

“For instance, who’s going to roll out the infrastructure to extract sodium? The lithium-ion industry is the new oil industry, a cartel, so to speak. There are hundreds, thousands of companies involved in the lithium-ion battery industry, and they won’t easily relinquish their initiative to solid-state batteries,” Kim went on.

Despite the limits of solid-state batteries, Kim said niche markets do exist.

As solid-state batteries are fire-resistant, they are appropriate for electric airplanes, for instance. Also, high-profile figures like presidents whose top priority is safety might create demand for electric vehicles powered by solid-state batteries, but still, their potential seems limited.

“Solid-state batteries have limited applications, so their market size is expected at 5 percent that of lithium-ion batteries. Battery makers are unlikely to exhaust their resources for solid-state batteries just for this 5 percent,” Kim said.

By Kim Byung-wook (kbw@heraldcorp.com)