The progress of renewable energy sources and electro-mobility is accompanied with a successful implementation of effective electrochemical energy storage devices, among which the Li ion batteries (LIB) constituting the state-of-the-art (SOTA) technology, occupy a highly positioned place. For reasons of competitiveness to fossil fuels, a significant boost in specific energy is necessary, affording intense research and development (R&D) efforts. For SOTA negative and positive electrodes based on graphite and layered oxide (LiTMO₂) active materials, respectively, the increase in the cell operation voltage represents a widely pursued and promising strategy in this regard.

However, the intended gain in specific energy is accompanied with the rise in specific capacity losses and thus, with the limitations comprising battery life time (cycle life), which is associated with the elevated potential of the positive electrode. The oxidative instability of the aprotic SOTA electrolyte (based on LiPF₆/organic carbonates), as an inactive but essential multicomponent material in electrochemical energy storage devices, is assumed to be the main cause. As a consequence, many R&D efforts in terms of LIB high voltage operation are focused on the improvement and development of advanced electrolyte formulations.

In analogy to negative electrodes in literature, for positive electrodes as well, the specific capacity losses in the initial charge/discharge cycle commonly act as indicators for electrochemical electrolyte decompositions. However, in contrast to negative electrodes, the specific capacity losses for positive electrodes reveal ambiguous results upon variation of active materials and charge cut-off potentials. Moreover, data obtained from potentiodynamic based electrochemical stability measurements point to even sufficient oxidative stabilities of the nonaqueous aprotic electrolytes, thus conflicting with the conventional interpretation of specific capacity losses.

In this work, the apparently contradicting interpretations of the data obtained from galvanostatic and potentiodynamic measurements are systematically unraveled to finally understand the real role and the significance of the oxidation of liquid SOTA electrolytes during high voltage applications in LIBs.

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