Increasing the energy density of layered oxide battery electrodes is challenging as accessing high states of delithiation often triggers voltage degradation and oxygen release. Here, we utilize transmission-based X-ray absorption spectromicroscopy and ptychography on mechanically cross-sectioned Li1.18-xNi0.21Mn0.53Co0.08O2-δ electrodes to quantitatively profile the oxygen deficiency over cycling at the nanoscale. The oxygen deficiency penetrates into the bulk of individual primary particles (~ 200 nm) and is well-described by oxygen vacancy diffusion.Using an array of characterization techniques, we demonstrate that, surprisingly, bulk oxygen 2 vacancies which persist within the native layered phase are indeed responsible for the observed spectroscopic changes. We additionally show that the arrangement of primary particles within secondary particles (~ 5 μm) causes significant heterogeneity in the extent of oxygen release between primary particles. Our work merges an ensemble of length-spanning characterization methods and informs promising approaches to mitigating the deleterious effects of oxygen release in lithium-ion battery electrodes.

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Emily is a senior chemical engineering student at Northeastern University with a minor in biochemical engineering. She has been a chemistry tutor for freshman engineering students for the past three years. Miss Rachel Lauren Shapiro, Northeastern UniversityRachel Shapiro is a third year undergraduate student studying chemical engineering at Northeastern University. She has been involved in the Connections Chemistry Review program for the past 2 years. Rachel works in a chemical engineering lab on campus, has held a co-op position at Davol, Inc. and will be completing another co-op with Entrega Biosciences. Ms. Emma Kaeli, Northeastern UniversityEmma Kaeli is a second-year undergraduate student at Northeastern University, majoring in chemical engineering and pursuing a minor in mathematics. Outside of class, Kaeli works as a chemistry tutor and class grader, and she participates in undergraduate research in a materials science laboratory on campus. She also has held an engineering co-op position with Rogers Corporation's Innovation Center. Ms. Kristen Barbara Coletti, Georgia Institute of TechnologyKristen Coletti is recent graduate of Northeastern University. She received her BS in Chemical Engineering in 2014 and was involved in the Connections Chemistry Review program for over 5 years. Kristen is currently pursuing her Master's Degree in Mechanical Engineering at Georgia Tech, while working full time as an engineer in the Edison Engineering Development Program at GE Power & Water.Dr. Paul A. DiMilla, Northeastern University Paul A. DiMilla is an Associate Academic Specialist in Chemistry & Chemical Biology and Chemical Engineering at Northeastern University. During his academic career at Carnegie Mellon University, Boston University, and Olin College he has been the recipient of the first Whitaker Young Investigator Award from the BMES, a Searle Scholar Award, and an Early Career Development Award from the NSF as well as a three-time recipient of the Omega Chi Epsilon Outstanding Faculty Award from the Northeastern Student Affiliate of AIChE. He also has led industrial R&D teams at Organogenesis Inc. and Polymerix Corporation developing tissue-engineered medical products and drug-generating biodegradable polymers, respectively, and has co-founded Automated Cell, Inc. In addition to being an inventor on 11 issued US patents, he has published the textbook General Chemistry for Engineers with Cognella Academic Publishing. Ms. Rachelle Reisberg, Northeastern University The Impact of Supplemental Instruction on the Performance of Male and Female Engineers in a Freshmen Chemistry Course AbstractThis study investigates the connection between the use of supplemental instruction (SI) by engineering students and their performance in a required first year general chemistry course. SI includes group and one-on-one peer tutoring as well as instructor and teaching assistant office hours. Previous research has shown that participation in SI correlates with higher course grades, more confidence in course material, greater ma...

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is a fourth year undergraduate student at Northeastern University, majoring in chemical engineering and minoring in biochemical engineering. He has been involved in the Connections Chemistry Review program for three years. He has also held an undergraduate research position in a biomaterials laboratory on campus. He has completed two coops in the biotech industry, and is currently completing his third coop at a tissue engineering research laboratory at the University of Hannover in Germany. Ms. Caroline Ghio, Northeastern University Caroline is a third-year undergraduate student at Northeastern University, majoring in chemical engineering and minoring in data science. She completed her first coop at a biotech startup working on sustained release drug delivery. Ghio has tutored students as part of the Connections Chemistry program for two years and does research in a biomaterials laboratory on Northeastern University's campus.