[Complete Battery Mastery](16) The Race for Commercialization of the 'Dream Battery' All-Solid-State Battery Heats Up

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Samsung SDI established an ASB (All Solid Battery) commercialization promotion team during its regular organizational restructuring on December 4th. This team is a direct organization within Samsung SDI's medium-to-large battery business division and will be responsible for the full-scale promotion of the all-solid-state battery business. Samsung SDI reportedly completed the construction of a pilot line for all-solid-state batteries in Suwon in March this year and has provided samples to customers. Samsung SDI aims to commercialize all-solid-state batteries by 2027.

In October, Japan's Toyota announced a strategic partnership with Idemitsu Kosan for the development and mass production of all-solid-state batteries. The two companies plan to commercialize next-generation batteries around 2027-2028. At the press conference, Koji Sato, President of Toyota, explained, "By combining Idemitsu Kosan's material manufacturing technology with Toyota's battery mass production technology, we will establish a mass production system for all-solid-state batteries."

Koji Sato, President of Toyota Motor Corporation (left in the photo), and Shunichi Kito, President of Idemitsu Kosan, are shaking hands and posing for a photo at a joint press conference on October 12 regarding collaboration on solid-state batteries.
[Image source=EPA Yonhap News]

The so-called "dream battery," the all-solid-state battery, is making steady progress toward commercialization. Although slow, these are significant steps. Major companies have set goals to commercialize electric vehicles equipped with all-solid-state batteries around 2027 and are actively conducting tests. All-solid-state batteries have already been installed in small electronic devices. The competition to secure the all-solid-state battery market, expected to bloom fully from the 2030s, has already ignited.

'Dream Battery' All-Solid-State Battery Barriers

All-solid-state batteries (ASB) refer to batteries made entirely of solid materials. Structurally, they replace the liquid electrolyte in the four main components of conventional lithium-ion batteries (cathode, anode, separator, electrolyte) with a solid electrolyte and eliminate the separator.

All-solid-state batteries were developed to prevent the vulnerabilities of lithium-ion batteries, such as fire and thermal runaway. In lithium-ion batteries, the electrolyte serves as the pathway for lithium ions to move between the cathode and anode. The liquid electrolyte consists of lithium salts, organic solvents, and small amounts of additives. Being organic, it is vulnerable to heat and poses a fire risk. Replacing it with a solid electrolyte can suppress fires.

In lithium-ion batteries using liquid electrolytes, separators are used to prevent direct contact between the cathode and anode. However, in all-solid-state batteries, the solid electrolyte itself acts as the separator, eliminating the need for a separate separator. This reduces battery volume and improves energy density.

All-solid-state batteries involve changes not only in the electrolyte but also in the cathode and anode materials. Because they use electrochemically stable solid electrolytes, higher voltage cathode materials can be employed.

Additionally, solid electrolytes have excellent mechanical strength, which can suppress dendrite formation. This allows the use of lithium metal as the anode, which is vulnerable to dendrite formation but can increase battery capacity. (Refer to Complete Battery Mastery Episode 14) As a result, all-solid-state batteries can dramatically increase energy density by applying high-capacity cathodes and lithium metal anodes. The absence of fire risk and the ability to increase energy density are why all-solid-state batteries are called "dream batteries."

However, manufacturing all-solid-state batteries is not as easy as it sounds. To develop all-solid-state batteries, issues such as ▲low ionic conductivity of solid electrolytes at room temperature and ▲high interfacial resistance at the electrode-solid electrolyte interface must be resolved. These problems arise from using solid electrolytes instead of liquid ones.

In lithium-ion batteries, liquid electrolytes actually permeate and wet both the anode and cathode materials, allowing lithium ions to flow naturally through the liquid electrolyte. However, solid electrolytes cannot mix as uniformly as liquids, resulting in voids. These voids reduce ionic conductivity.

All-solid-state batteries consist of solid electrolytes and solid electrodes. Resistance occurs at the contact interface (interphase) between solids. Chemical reactions between solids are less active than between solids and liquids. Imagine two stones touching each other. Naturally, this lowers the performance of all-solid-state batteries.

To increase ionic conductivity in all-solid-state batteries, maximizing contact between the electrolyte and electrodes and minimizing interfacial resistance are essential. Even if these technical issues are solved, there is one last hurdle to commercialization: cost. All-solid-state batteries use different materials and processes from conventional lithium-ion batteries, making initial costs inevitably high.

In the early market, the all-solid-state battery market is expected to be very small. Market research firm SNE Research forecasts the electric vehicle all-solid-state battery market to be 131 gigawatt-hours (GWh) in 2030, accounting for only 4% of the total. Even the most aggressive company, Samsung SDI, estimates the market size at 40 GWh in 2030.

Nevertheless, companies are competitively developing all-solid-state batteries to secure next-generation technology and markets. The future landscape of the secondary battery market will change depending on who finds the answer first.

Solid Electrolytes: Sulfide vs. Oxide

Solid electrolytes used in all-solid-state batteries are broadly divided into inorganic and organic types. Inorganic types include sulfide-based and oxide-based solid electrolytes, while organic types mainly use polymer solid electrolytes.

Among these, sulfide-based solid electrolytes are receiving the most attention. Because sulfide-based solid electrolytes are relatively soft, applying some pressure allows them to form a wide interface with the electrodes. They also have the advantage of higher ionic conductivity compared to other solid electrolytes. Companies such as Toyota and Samsung SDI are prioritizing research on sulfide-based electrolytes with commercialization in mind.

However, sulfide-based solid electrolytes contain sulfur, which can react with oxygen and moisture in the air to produce toxic hydrogen sulfide (H2S) gas. Processes to prevent toxic gas generation are necessary, leading to increased costs.

Sulfide-based solid electrolytes can be classified into crystalline and non-crystalline types depending on their crystal structure. Representative crystalline structures include LISICON (Lithium Super Ion CONductor), LGPS (Li10GeP2S12), LPS (Li7P3S11), and Argyrodite structures. Non-crystalline types are divided into glass and glass-ceramic electrolytes depending on heat treatment temperature.

Oxide-based solid electrolytes have excellent mechanical stability, reducing fire risks such as thermal runaway. They are also electrochemically stable. However, they are hard and brittle, making it difficult to use roll-to-roll processes common in conventional lithium-ion battery manufacturing. Their lower lithium-ion conductivity compared to sulfide-based electrolytes is another challenge to overcome.

Using oxide-based electrolytes requires a high-temperature sintering process. Sintering is a process of applying pressure and heat to powder materials to form a solid mass. This also increases production costs. To overcome the disadvantages of oxide electrolytes, hybrid types mixing polymer electrolytes are being researched.

Examples of oxide-based solid electrolytes include LLTO (Li3xLa2/3-xTiO3) with a perovskite structure, LLZO (Li7La3Zr2O12) with a garnet structure, and LATP (Li1+xAlxTi2-x(PO4)3) with a NASICON (Na Super Ionic CONductors) structure.

Polymer solid electrolytes are similar to conventional liquid electrolyte technology and manufacturing processes. They are relatively easy to commercialize and can be produced at low cost. However, they have low ionic conductivity at room temperature. The French Bollore Group's Bluebus has commercialized polymer solid electrolytes. Polymer solid electrolytes consist of a polymer matrix, lithium salts, and additives. PEO (Poly Ethylene Oxide) is a representative polymer matrix.

·Perovskite structure: Perovskite is the name of a mineral composed of calcium titanate (CaTiO3), first discovered in 1839 in the Ural Mountains of Russia. It is named after Russian mineralogist Perovski.
·Argyrodite structure: A crystal structure similar to a steel-colored mineral containing silver, germanium, and sulfur (Ag8GeS6).
·Garnet structure: A crystal structure similar to garnet, a mineral named after the Latin word for pomegranate due to its color and shape.

Who Will Commercialize All-Solid-State Batteries First?

Amid fierce competition in all-solid-state battery development, some companies have already commercialized products. One such company is Japan's Maxell. In June, Maxell announced it had commercialized the world's first small all-solid-state battery using sulfide-based solid electrolytes. However, Maxell's products are very small, about 1 cm in size, and are limited to small electronic components.

In November, the company announced it is developing a cylindrical all-solid-state battery with 25 times the capacity (200 mAh) of its existing product. This battery operates over a wide temperature range from -50°C to 125°C. Maxell plans to provide samples starting January 2024. Although small, Maxell's all-solid-state battery is significant as it confirms the possibility of commercialization.

Development and testing of all-solid-state batteries for electric vehicles are also actively underway. Taiwan's ProLogium unveiled a large-footprint lithium ceramic battery (LLCB) at the ESS Europe event held in Munich in June and announced plans to provide prototypes to European automakers by the end of this year.

ProLogium first revealed its all-solid-state battery at CES 2020 and has since been negotiating with several automakers. In 2022, German Mercedes-Benz and Vietnam's VinFast announced investments in the company. ProLogium claims its all-solid-state battery achieves twice the energy density of the 2170 cylindrical battery, reducing vehicle weight by 115 kg.

The company stated in 2021 that it achieved volumetric energy densities of 440-485 Wh/L, 80% charge in 12 minutes, and 1000 charge-discharge cycles. It also claims these performances are achievable with 2170 or 4860 cylindrical batteries.

U.S. company QuantumScape announced on December 24, 2022, that it provided 24-layer all-solid-state battery A0 samples to automakers. In the second quarter of 2023, it unveiled a commercial version named QSE-5. This battery cell has a capacity of 5 ampere-hours (Ah) and an energy density of 800 watt-hours per liter (Wh/L). The company claims it can charge to 80% in 15 minutes.

QuantumScape's QSE-5 All-Solid-State Battery

In August 2023, QuantumScape stated in a letter to shareholders that it is closely negotiating with potential automotive customers about product launches but did not disclose the customers' identities. The market believes Volkswagen is testing QuantumScape's all-solid-state batteries. Volkswagen has collaborated with QuantumScape since 2012 and has invested $300 million in the company.

QuantumScape is building a QS-0 pilot line in San Jose, California, and plans to build a second pilot line, QS-1, with Volkswagen. The QS-1 line will start at a 1 GWh scale and expand to 21 GWh in the future.

U.S. venture company Solid Power announced in its Q3 report released in November that it has started supplying A samples to German automaker BMW, marking the first official verification for commercialization. BMW plans to unveil a demo electric vehicle using Solid Power's batteries by 2025.

Solid Power's All-Solid-State Battery

Solid Power is developing sulfide-based all-solid-state batteries and constructing a pilot line capable of producing 15,000 cells annually. The plant is scheduled to begin production in 2026. In Korea, SK Innovation invested $30 million in Solid Power in January 2022 and signed a joint development and production agreement for next-generation batteries.

According to Solid Power's 2021 disclosure, its all-solid-state battery can achieve an energy density of 390 Wh/kg by weight and 930 Wh/L by volume when using NCM811 (nickel-cobalt-manganese ratio of 8:1:1) cathode and silicon anode materials. Using lithium metal anodes increases the gravimetric energy density to 440 Wh/kg (volumetric energy density remains the same). Based on this, the company estimates it can manufacture a 77 kWh battery pack.

In Korea, Samsung SDI is considered the most aggressive in the all-solid-state battery field. Samsung SDI plans to apply a high-nickel NCA (nickel-cobalt-aluminum) cathode and a sulfide-based solid electrolyte with an argyrodite structure that enhances ionic conductivity. Samsung SDI reportedly sources electrolytes from Posco JK Solid Solutions, a joint venture between Posco and Jungkwan Co., Ltd.

Samsung SDI All-Solid-State Battery Structure

Samsung SDI plans to apply an innovative "anode-less" technology using novel materials for the anode. Instead of conventional anode materials like graphite, silicon, or lithium metal, it adds a nano silver-carbon composite layer (Ag-C nano composite layer) to facilitate stable lithium-ion movement. Samsung SDI aims for an energy density of 450 Wh/kg by weight and 900 Wh/L by volume for its all-solid-state batteries.

LG Energy Solution plans to first introduce polymer-based all-solid-state batteries in 2026 and mass-produce sulfide-based all-solid-state batteries by 2030. To this end, it is conducting related research with KAIST and Seoul National University. SK On is developing sulfide-based and polymer-oxide hybrid all-solid-state batteries, aiming to produce battery samples in 2026 and commercialize by 2028.

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electrive, ProLogium creates solid-state battery pack with higher energy density, June 19, 2023
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