Abstract
Currently, cobalt-containing lithium-ion batteries (LIBs) are the commercial standard, but due to scarcity and high cost, there is a need for batteries that use more earth-abundant cathode materials. Understanding the degradation pathways in earth-abundant alternative cathode (EACaM) materials due to cycling is key to ensure that similar performance and stability to current standard cathodes are achieved. This work evaluates the effects of electrolyte additives on the cathode electrolyte interface (CEI) formed on EACaM particles during cycling using cryogenic electron microscopy techniques. Additives predicted by machine learning (ML) models to have optimal performance are selected and experimentally validated, demonstrating a significant improvement over the baseline. The use of cryogenic scanning transmission electron microscopy (cryo-STEM) with electron energy loss spectroscopy (EELS) preserves the beam-sensitive CEI providing atomic- to nanoscale information on the surface chemistry of the EACaM particles. Cycled cathodes with the ML additive combination were seen to have less variation in Mn valence state at the CEI layer compared to the bulk and the oxygen pre-edge peak associated with transition metal bonding was retained. This suggests a stabilized surface chemistry of the EACaM particles making them less prone to Mn dissolution, contributing to the observed improvements of LIB performance with these ML electrolyte additives.
*This work was authored in part by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding provided by U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Vehicle Technologies Office. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes.
