The lithium and lithium-ion battery electrode chemical stability in the pristine state has rarely been considered as a function of the binder choice and the electrode processing. In this work, X-ray photoelectron spectroscopy (XPS) and XPS imaging analyses associated with complementary Mössbauer spectroscopy are used in order to study the chemical stability of two pristine positive electrodes: (i) an extruded LiFePO4-based electrode formulated with different polymer matrices [polyethylene oxide and a polyvinylidene difluoride (PVdF)] and processed at different temperatures (90 and 130 °C, respectively) and (ii) a Li­[Ni0.5Mn0.3Co0.2]­O2 (NMC)-based electrode processed by tape-casting, followed by a mild or heavy calendering treatment. These analyses have allowed the identification of reactivity mechanisms at the interface of the active material and the polymer in the case of PVdF-based electrodes.

The discharge rate performance of NMC532-based electrodes designed for EV application were measured between 0 and 40°C and were compared to the predictions of the electrolyte limited penetration depth model [Gallagher et al., J. Electrochem. Soc. 163, A138 (2016)], also called diffusion limited current density model [Heubner et al., J. Power Sources 419, 119 (2019)]. To support this analysis, we took into account the actual microstructure of the electrodes, previously characterized by FIB/SEM tomography, and their measured and/or simulated transport properties. We show that the performance of NMC532 electrodes, even with a low carbon content below the percolation threshold, are not limited by electrons transport through the electrode due to the high intrinsic conductivity of this active material. At 40°C, the swelling of the PVdF by the electrolyte solvents penalizes performance, especially as the binder content is high. Above all, the current density at which a brutal decrease in capacity occurs is well predicted by the model, although by reducing the porosity to its percolated micrometer sized fraction. This is in good agreement with the numerical simulations of the ionic transport properties.