How to Characterize Lithium-Ion Battery Binders: FTIR, TGA &DSC Explained

 

A look at the analytical methods behind binder selection—and why the "invisible" component of your electrode deserves closer attention.

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When researchers talk about lithium-ion battery performance, the conversation usually gravitates toward the active materials: the cathode chemistry, the anode graphite, the electrolyte formulation. Binders rarely get top billing. Yet without them, an electrode simply falls apart.

Binders hold the active material and conductive additives together and keep the coating adhered to the current collector. They influence mechanical integrity, processability, and—increasingly important as the industry moves toward greener, water-based manufacturing—the environmental footprint of the whole electrode fabrication process. Choosing the right binder, and understanding how it behaves under heat and processing conditions, is a genuine part of building a better cell.

So how do you actually characterize a battery binder? This post walks through three complementary analytical techniques—FTIR, TGA, and DSC—and what each one tells you, using three of the most common binders as examples: Na-CMC, PVDF, and SBR.

We were pleased to see this exact study carried out by the team at Shimadzu (Asia Pacific) Pte Ltd, using binder materials supplied by Beyond Battery. Their application note is a clear, practical illustration of how these methods come together, and we've drawn on it throughout this article.

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Meet the three binders

Before the analysis, it helps to know the players:

PVDF (Polyvinylidene fluoride) is the classic cathode binder. It's valued for excellent chemical and electrochemical resistance, good thermal and mechanical stability, and favorable rheological behavior with carbon materials. The catch: PVDF is typically processed with organic solvents such as NMP, which are neither cheap nor environmentally friendly.

Na-CMC (Sodium carboxymethyl cellulose) and SBR (Styrene-butadiene rubber) are the water-soluble alternatives that enable a fully water-based electrode route—no organic solvents required. They're frequently used together on the anode side, and they've become central to the industry's push toward more sustainable manufacturing.

Understanding the composition and thermal behavior of each is what lets a researcher or manufacturer make an informed choice. That's where analytical characterization comes in.

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FTIR: Confirming what your binder is made of

Fourier Transform Infrared Spectroscopy (FTIR) identifies the chemical bonds and functional groups present in a sample, producing a spectral "fingerprint" of its composition. It's the go-to technique for confirming a material's identity and screening for contaminants or unexpected components.

In the Shimadzu study, the three binders were measured on an IRSpirit™ FTIR fitted with a single-reflection diamond ATR accessory—a setup that lets you press a sample directly onto the crystal and measure it with minimal preparation.

One practical wrinkle showed up with SBR. Because the SBR sample was supplied as a water-based emulsion, strong water absorption bands dominated the spectrum and masked the binder's own peaks. The fix was simple and instructive: the SBR was coated onto a glass slide and left to dry overnight to drive off the water, then re-measured. With the water gone, SBR's characteristic absorption peaks—especially in the region below 1000 cm⁻¹—came through clearly.

The takeaway for your own work: sample preparation matters. A binder delivered as an emulsion or solution may need drying before FTIR gives you a clean, interpretable spectrum.

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TGA: How much heat can your binder take?

Thermogravimetric Analysis (TGA) measures how a sample's mass changes as it's heated. It's the primary tool for assessing thermal stability—telling you the temperature at which a material begins to decompose, and how much mass it loses along the way.

The study used a Shimadzu DTG-60 simultaneous DTA-TGA, heating samples from room temperature up to 580 °C in both nitrogen and air atmospheres. Decomposition temperature was defined as the point where the sample had lost 2% of its mass.

Here's what the three binders showed (average of two measurements):

 

A few things worth drawing out:

PVDF is the most thermally stable of the three, decomposing near 400 °C, followed by SBR and then Na-CMC. Na-CMC's earlier mass loss is partly water-related; because it's hygroscopic, it holds adsorbed moisture that comes off below 200 °C, so its "true" decomposition is assessed from that point onward.

Atmosphere matters for some binders more than others. Na-CMC and PVDF behaved similarly in nitrogen and air, but SBR decomposed at a noticeably lower temperature in air (286.4 °C) than in nitrogen (312.8 °C)—a reminder that oxidative conditions can shift a material's stability.

TGA also reveals degradation mechanisms. In air, PVDF showed two distinct weight-loss stages. The first (roughly 30–484 °C) is associated with defluorination, while the second, above 484 °C, corresponds to breakdown of the remaining carbon backbone. That kind of detail is invisible to a single-point measurement but obvious in a TGA curve.

Why this matters practically: battery electrodes are typically prepared and dried in the range of 20–90 °C. All three binders decompose well above that window in both nitrogen and air—so from a thermal-stability standpoint, Na-CMC, PVDF, and SBR are all suitable for standard electrode manufacturing.

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DSC: Understanding phase transitions and thermal behavior

Differential Scanning Calorimetry (DSC) measures the heat flow into or out of a sample as it's heated and cooled, revealing thermal transitions like glass transition (Tg), melting (Tm), and crystallization (Tc). Where TGA tells you when a material breaks down, DSC tells you how it behaves across its usable temperature range.

The samples were run on a Shimadzu DSC-60 Plus, cycled through heating and cooling steps under nitrogen. The results (averaged over two runs):

Each binder tells its own story:

PVDF behaves like the semi-crystalline polymer it is—a glass transition around –38 °C, melting near 164 °C, and crystallization on cooling around 122 °C. These are the transitions that govern how it processes and how it holds up thermally in a finished electrode.

SBR, an elastomer, shows a glass transition around 15.7 °C, consistent with its rubbery character at room temperature.

Na-CMC is the interesting case. On the first heating, it shows a broad peak around 115 °C—but this isn't a melting transition. Because Na-CMC is hygroscopic, the peak reflects evaporation of physically bound water from the cellulose structure. The proof: on the second heating, the peak is gone, because the water was already driven off the first time around. This lines up neatly with the TGA data, which showed Na-CMC losing water below 200 °C.

The lesson: DSC and TGA are more powerful together than apart. Cross-referencing the two lets you correctly interpret a signal—distinguishing, say, a genuine melting event from simple moisture loss.

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Bringing it together: why characterization is worth the effort

Three techniques, three different lenses on the same materials:

• FTIR confirms what the binder is (composition and functional groups).
• TGA tells you how much heat it can withstand (thermal stability and decomposition).
• DSC reveals how it behaves thermally (phase transitions across its working range).

Used together, they give a complete picture—one that supports smarter binder selection, better process design, and more reliable cells. And they underscore a point we care about at Beyond Battery: the quality and consistency of a research material shapes everything downstream of it. A binder that behaves predictably under characterization is a binder you can build on.

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Materials you can trust

The binders in this study—Na-CMC, PVDF, and SBR—were supplied by Beyond Battery Pte Ltd. We provide battery research materials and lab equipment to researchers, universities, and industrial R&D teams in over 40 countries, and it's genuinely rewarding to see those materials supporting rigorous analytical work like this.

Whether you're formulating a water-based electrode, benchmarking binders, or building out a full research workflow, we're here to help you source materials you can rely on.

Explore our range of battery binders and research materials at beyond-battery.com, or reach out to our team to discuss your requirements.

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This article draws on the Shimadzu (Asia Pacific) application note "Characterization of Lithium-Ion Battery Binders" (Ai Ming Chua and Zhen Hao Lee, Centre for Application Solutions). Beyond Battery supplied the binder materials used in the study but was not involved in conducting the research. Analytical data and figures are the work of Shimadzu Corporation.