TA Instruments, a division of Waters Corporation, has published a battery testing selection guide that pairs analytical techniques with specific battery components. It covers rheology for electrode slurries, TGA and DSC for binders and electrolytes, TMA and DMA for separators, microcalorimetry for full cells, and thermal conductivity tests for pack materials.
TA Instruments, a division of Waters Corporation based in New Castle, Delaware, has published a selection guide that pairs specific analytical techniques with each stage of battery development. It covers electrode slurries, separators, electrolytes, thermal interface materials and pack casings, as well as complete cells.
The guide is organized by component. Each section sets out a common engineering problem, the measurement used to address it and the instrument that performs it.
Full cells
For complete cells, the guide describes isothermal microcalorimetry (IMC) carried out during electrochemical cycling. The method measures heat flow in operando and separates heat from the main electrochemical reactions from heat produced by parasitic side reactions. It is used to study first-cycle solid electrolyte interphase (SEI) formation, parasitic power across full or narrow voltage ranges, and self-discharge rates. A coin cell differential scanning calorimeter (DSC) covers thermal stability, gases released during thermal failure, heat flow during overcharge or overdischarge, and cycling at subambient temperatures.
Electrode slurries and binders
The electrode section focuses on slot-die coating. An ideal slurry has low viscosity at the high shear rates of mixing and coating, but enough viscosity at low shear rates to level during drying and resist particle settling in storage. Rheology is used to measure viscosity, viscoelasticity, yield stress and thixotropic recovery. Rheo-impedance spectroscopy measures electrical impedance and rheology at the same time to show how the conductive network in a slurry changes under shear. For dry electrode processing, powder rheology with temperature control measures the flowability, compressibility and wall friction of the dry mix.
Thermogravimetric analysis (TGA) quantifies binder and additive content in finished electrodes. The guide notes that too little binder weakens adhesion to the current collector, while too much reduces the share of active material. DSC identifies a binder’s glass transition temperature. An example in the guide compares two binders with glass transition midpoints of 5.13°C and 43.76°C, against a typical lithium-ion operating range of -20°C to 60°C.
Separators and electrolytes
In one TGA example, an uncoated separator loses 99.93% of its mass. A coated separator loses 37.16% and then 5.84%, leaving a 55.06% residue that reflects its inorganic coating. Thermomechanical analysis (TMA) measures shrinkage onset and rupture temperature. Dynamic mechanical analysis (DMA) measures tensile strength and modulus. In the DMA example, the storage modulus onset falls at 43.89°C for the uncoated film and 26.41°C for the coated film.
For electrolytes, combined TGA and DSC give decomposition temperature, solvent loss, onset temperature and heat of reaction. The guide says these values can be used to estimate heat release during thermal runaway. DMA is applied to gel polymer electrolytes, which act as both electrolyte and separator, and rheology is used to assess pumpability in manufacturing. The company’s TGA and rheometers can be operated inside argon or nitrogen gloveboxes for air-sensitive samples.
Module and pack materials
At pack level, DSC measures the heat of fusion and heat capacity of phase change materials (PCM). Thermal conductivity meters and laser flash analysis measure the conductivity and diffusivity of thermal adhesives. For casings, DMA and mechanical test instruments assess creep and fatigue under load, TMA measures thermal expansion, and TGA evaluates degradation temperature and evolved gases during thermal events.
The guide ends with a technique reference sheet summarizing TGA, DSC, DMA, rheology and IMC.
