Jacob LaManna1,Maha Yusuf2,3,Michael Daugherty1,3,Youngju Kim1,3,Eli Baltic1,Boris Khaykovich4,Johanna Weker5,Michael Toney6,Daniel Hussey1,David Jacobson1
National Institute of Standards and Technology1,Stanford University2,University of Maryland3,Massachusetts Institute of Technology4,SLAC National Accelerator Laboratory5,University of Colorado Boulder6
Jacob LaManna1,Maha Yusuf2,3,Michael Daugherty1,3,Youngju Kim1,3,Eli Baltic1,Boris Khaykovich4,Johanna Weker5,Michael Toney6,Daniel Hussey1,David Jacobson1
National Institute of Standards and Technology1,Stanford University2,University of Maryland3,Massachusetts Institute of Technology4,SLAC National Accelerator Laboratory5,University of Colorado Boulder6
Neutrons and X-rays provide complementary penetrating probes for electrochemical systems. Neutrons have high sensitivity to hydrogen and lithium, two elements important to fuel cells and lithium-ion batteries. X-rays of sufficient energy are sensitive to the solid structure in electrochemical systems. To fully leverage this complementarity, the National Institute of Standards and Technology (NIST) provides the NIST-NeXT system for truly simultaneous neutron and X-ray tomography. NIST-NeXT is well suited for investigations of electrochemical systems due to the simultaneous acquisition of both modalities, ensuring that both modes view the sample at the exact same sample state. The materials typically used to make electrochemical devices for neutron investigations are typically at odds with X-ray investigations, and vice versa. For example, X-ray compatible fuel cells are often fabricated of plastics, such as polyether ether ketone (PEEK), which are opaque to neutrons while neutrons can easily penetrate steel and titanium that can be opaque to X-rays. Material selection and their effects on electrochemical performance are critical to facilitate multimodal analysis. Neutrons are isotopically sensitive making it possible to adjust the sample transmission through isotopic exchanges such as replacing hydrogen with deuterium, which has a 10x lower neutron attenuation coefficient. Therefore, it is feasible to reduce the hydrogen content of a lithium-ion battery by replacing standard hydrogenous polymer separator and electrolytes with deuterated materials resulting in increased neutron transmission, and hence better contrast for lithium in the electrochemical system. X-rays, on the other hand, require lower atomic number elements to increase transmission through the sample. The substitution of stainless steel with aluminum has the benefit of higher X-ray transmission but corrosion becomes a problem in an acidic electrochemical environment. This talk will go over the design trade-offs for fuel cells and batteries required to conduct simultaneous neutron and X-ray tomography and provide insight into the design choices for recommended cell configurations. Additionally, example fuel cell and battery studies using NIST-NeXT will be given.