Characterization of Binder Materials from Lithium Ion Batteries by Fingerprint Analysis with Pyrolysis‐Gas Chromatography‐Mass Spectrometry

Binders are important inactive materials for the performance and safety of lithium ion batteries (LIBs). Their identification from unknown cells or mixed recycling waste streams for teardown analysis or process control can be challenging. This study demonstrates an analytical approach using pyrolysis‐gas chromatography‐mass spectrometry (PY‐GC‐MS), where characterization of these polymers is enabled by selective indicator pyrolyzates and where interfering matrix components are removed in a multishot pyrolysis. The binder materials styrene butadiene rubber (SBR), sodium carboxymethyl cellulose (Na‐CMC), polyacrylic acid (PAA) and lithium polyacrylate (Li‐PAA) are investigated in graphite (Gr)‐ and silicon nanowire (SiNW)‐based electrodes at various stages of aging. A change of the CMC fingerprint is observed upon electrode processing, electrolyte contact, and electrochemical aging. Aging of the binder and superposition of polymeric solid electrolyte interphase (SEI) components is observed at 350 °C pyrolysis temperature. Washing experiments with dimethyl carbonate (DMC) are performed to differentiate between SEI‐ and binder‐related pyrolyzates and to provide information on the aging condition of the electrodes. All binders show consistent fingerprints at 600 °C across all states of aging. This fingerprinting method improves the identification of polymers in battery recycling streams and provides insights into the thermal decomposition of negative electrode (NE) materials.