Josh

Abstract:

Lithium-ion batteries (LiB) are ubiquitous and drive a wide variety of devices from personal electronics to electric vehicles. Development of LiB has traditionally been driven by electrochemists and has focused heavily on optimizing charge density per cell. An unintentional end result is a handful of predominant cathode chemistries – LiFePO₄ (LFP), LiCoO₂ (LCO), LiNiAlCoO₂ (NCA), or LiMn₂O₄ (LMO) – many of which can also be considered as dilute magnetic semiconductors. The magnetic nature of separate LiB components (i.e. anode, cathode, electrolyte, etc.) has been most studied using SQUID magnetometry. Nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) are increasingly used as well. Within the last six years, in vitro magnetometry has shown an innate magnetic field persists for LiB. Initial work centered on special non-magnetic pouch cell geometries. Recently we’ve shown that this magnetic field persists even for larger cylindrical formats like the 18650 and 21700.  In addition, changes in the innate magnetic field of LiB can be correlated with changes in the state of health of the battery. A question immediately arises – “How is this signal here to measure?”. In this talk, two different answers to that question will be discussed. The first answer is technical in nature and revolves around a wide variety of magnetometer types (OPM, AMR, TMR) which have been used to capture the magnetic field signal, and the nature of the anisotropic magnetic field emanating from a LiB cell. The second answer is less well developed, and revolves around how ferromagnetic, ferrimagnetic, and super-exchange interactions may possibly combine from the atomic to device scale to present the measured innate magnetic field. Much is unknown - but the importance of LiB in everyday life drives the need for increased understanding of magnetics to augment the existing knowledge of electrochemistry in the rational application, re-use and recycling of LiB.

Biography:

Speaker Bio – Dr. Joshua R. Biller

Dr. Joshua R. Biller is a Group Leader and Principal Scientist at TDA Research Inc. in Golden, CO. He completed his PhD in 2014 at the University of Denver under the guidance of Dr. Gareth and Dr. Sandra Eaton and was awarded the international Bruker Thesis prized in EPR Spectroscopy in 2015. After graduating, he was awarded a NRC Post-doctoral scholarship at the National Institute of Standards and Technology (NIST) in Boulder, CO in the Magnetic Imaging Group. At NIST, he designed and built low-magnetic field NMR and Overhauser DNP instrumentation. In 2018 he joined TDA Research Inc, where he develops new measurement techniques for in-field materials characterization based on electrical, optical (Raman spectroscopy and fluorescence), electromagnetic, magnetic resonance and magnetometry methods. He led initial work in 2020 showing magnetic field values correlated with a battery’s SOC could be read out for full commercial 18650 cells with both LiFePO₄ and LiCoO₂ cathode chemistries when using a total-field optically pumped magnetometer. Currently he is leading projects aimed at expanding the application of a wide variety of magnetometers to battery health and SOC monitoring.