The high-voltage LiNi 0.5 Mn 1.5 O 4 (LNMO) spinel is a promising candidate for a positive electrode in lithium ion batteries, but LNMO/graphite full-cells display severe capacity fading issues due to Mn dissolution. In this study, the dissolution behaviors of Mn and Ni were examined systematically under various conditions such as state of charge (SOC), temperature, storage time, and crystal structure of LNMO. In addition, surfaces of calendar-or cycle-aged LNMO and graphite electrodes were analyzed by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), or time-of-flight secondary ion mass spectrometry (TOF-SIMS). The chemical composition of aged electrolyte was determined by gas chromatography (GC) analysis after storage of LNMO electrodes under different conditions. It was found that the amounts of dissolved Mn and Ni and diethyl ether, a decomposition product of diethyl carbonate (DEC) in electrolyte, increased with SOC, temperature, and storage time. The decomposition of electrolyte can be explained, in part, by the self-discharge behavior of LNMO, which promotes electrolyte oxidation. Additional HF is believed to be generated during the formation of diethyl ether (via dehydration reaction from EtOH, another decomposition product of DEC), which accelerates Mn and Ni dissolution from LNMO. In addition, various reaction products that form as a result of Mn and Ni dissolution, such as LiF, MnF 2 , NiF 2 , and polymerized organic species, were found on the surface of LNMO electrodes, which will increase battery-cell impedance.

The chemical degradation of perfluorosulfonic acid (PFSA) membranes was studied both in‐situ (during fuel cell operation) and ex‐situ (by Fenton's test). During fuel cell operation, the degradation rate was quantified by monitoring the rate of fluoride release. The rate of degradation was found to be strongly dependent on operating conditions. Nuclear magnetic resonance (NMR) and mass spectrometry (MS) were used to identify degradation products other than fluoride generated during fuel cell operation. Strong similarities were found between the organic fragments generated from both the in‐situ (fuel cell operation) and ex‐situ (Fenton's test) degradation processes. The chemical structure of the fragment is consistent with that of the side chain on the PFSA ionomer used in the experiments. The implications of the existence of this product for the chemical degradation mechanism are discussed.

To achieve the acceptance criteria (±15%) for accuracy when removing a portion of the DBS spot for quantitative analysis, HCT and punch location for each selected card type will need to be assessed during validation and sample analysis.