<2023> Development Status and Outlook of Binder Technology for Secondary Batteries

Lithium-ion batteries (LIBs) are one of the most promising energy storage devices to address the growing demand for energy storage in electric vehicles and hybrid devices due to their high energy and power density, and their use is increasing rapidly with the growing interest in utilizing green energy for carbon reduction.

According to SNE Research, after the rapid development of new energy storage devices and electric vehicles, the demand for LIBs has been steadily increasing, and the electric vehicle battery market size is expected to grow from $196B in '25 to $401B in '30, with a CAGR of 21%.

The characteristics of LIBs are highly dependent on the electrodes, and optimizing the electrode structure is a top priority to achieve superior battery performance. While the active materials of the anode and cathode are currently being studied and examined with great interest in commercialized LIBs as well as in research, the inactive binder, which maintains the integrity of the electrode and supports the electrochemical process at a low weight fraction (≤5wt%), occupies a critical position in the performance of the electrode along with the active materials and conductors, but has received less attention compared to its importance.

Although binders are a very small part of the electrode, they play a critical role in determining the overall performance of the electrode. The binder is responsible for the adhesion of the anode and cathode active materials to the respective pole plates of the collector and for their durability. The binder must be (1) electrochemically stable in the electrolyte, (2) flexible and insoluble, and (3) resistant to corrosion by oxidation, especially for cathode binders.

Therefore, a functional binder with high bond strength and elasticity is required to effectively connect the active material and the conductor to the collector and accommodate volume expansion to ensure good electrode structure during charge and discharge. Recently, with more insights into binder screening and design, the focus of research is shifting from a mechanical stabilization perspective to multifunctionality that provides electrochemical benefits as well as structural support.

Recently, with the increasing adoption of silicon cathode materials, a new generation of research is underway, as studies have shown that binders have a significant impact on the lithiation reaction, helping to improve electrode capacity and cycleability. Conventional binders mainly use PVDF (PolyVinyliDeneFluoride), a fluoroplastic, for the cathode and SBR (Styrene-Butadiene-Rubber) and CMC (Carboxyl Methyl Cellulose) binders, a synthetic rubber, for the anode, but they are not suitable for use in silicon anodes due to large volume changes.

PTFE (PolyTetraFluoroEthylene) binders have been used for cathode materials, and water-based binders such as PAA (PolyAcrylicAcid) and PI (PolyImide) have been attracting attention for anode materials.

Binders such as PAA and PI are water-based binders, which are used in silicon anode materials that use water-based solvents as electrolytes. Compared to conventional binders, these binders have high tensile strength, high adhesion, and are resistant to volume expansion of silicon anode materials and form a stable SEI (Solid Electrolyte Interphase) layer by wrapping the active material.

PTFE, a next-generation binder for cathode materials, is a hydrophobic material with excellent chemical and heat resistance and is expected to gain attention in dry electrode processes and all-solid-state batteries.

PVDF binders are produced by Kureha in Japan, Solvay in Belgium, and Arkema in France, and SBR binders are produced by Zeon in Japan, all of which are expensive items with a high proportion of foreign production.

The cathode binder is produced by Korea's Chemtros, and for the anode binder, Korea's Hansol Chemical has successfully localized it and is supplying it to Samsung SDI and SK On, while LG Chem. and Kumho Petrochemical are also supplying cathode binders.

Meanwhile, SNE Research's global demand forecast for binders for lithium-ion batteries is expected to increase from 89,000 tons in 2025 to 232,000 tons in 2030, with a value of about KRW 4.4 trillion in 2030.

High-energy-density batteries are expected to place higher requirements on high-performance binders, and from this perspective, binder design should consider the following.

• (1) The binder content should be less than or equal to 3 wt% of the total electrode mass without losing mechanical strength and adhesion.

• (2) Simplification of synthesis using water-based and dry-based polymers from the perspective of low cost and sustainability.

• (3) Multifunctional polymer binders that can integrate all necessary functions into one polymer.

• (4) Deep insights into polymer dispersion and degradation mechanisms, and more.

In this report, SNE has summarized in detail the information available in the literature on the design, synthesis, and application of binders for lithium-ion battery electrodes and forecasted the demand and market for binders based on our forecasts for lithium-ion batteries, and quoted market size and forecasts from external research organizations in the appendix to help readers understand the overall scale.

Finally, by summarizing the status of binder manufacturers and their main products, we hope to provide a holistic insight for researchers and interested parties in this field, which will help to improve the performance of batteries, including their energy density, fast charging capability, and long-term life characteristics.

Strong points of this report:

• (1) Provides a general overview of the binder and contains rich technical content

• (2) Includes key points to consider in design and synthesis through examples of binder development.

• (3) Summarizes the development status and case analysis of binders not only for LIBs but also for next-generation batteries such as Li-S and all-solid-state batteries.

• (4) Provides objective figures on the binder market through objective binder market forecasts based on SNE Research's battery forecasts.

• (5) Detailed information on the development status and product status of major binder companies.

[Shipments and M/S of PVDF binder manufacturers]

[Shipments and M/S of SBR binder manufacturers]

[Binder cost analysis for 4680 cells for Tesla]

• Cathode: NCM811, Anode: Si series

• PVDF cathode binder consumption and cost for a 1 GWh cell: Approx. 38 tons, KRW 1.546 billion

• PAA anode binder consumption and cost for a 1 GWh cell: Approx. 24 tons, KRW 0.823 billion

[A schematic of the dry and wet processes for electrode fabrication]