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Realization of extreme fast charging (XFC, ≤15 minutes) of lithium-ion batteries is imperative for the widespread adoption of electric vehicles. However, dramatic capacity fading is associated with XFC, limiting its implementation. To quantitatively elucidate the effects of irreversible lithium plating and other degradation mechanisms on the cell capacity, it is important to understand the links between lithium plating and cell degradation at both the local and global (over the full cell) scales. Here, we study the nature of local lithium plating after hundreds of XFC cycles (charging C-rates ranging from 4C to 9C) in industrially-relevant pouch cells using spatially resolved X-ray diffraction. Our results reveal a spatial correlation at the mm scale between irreversible lithium plating on the anode, inactive lithiated graphite phases, and local state-of-charge of the cathode. In regions of plated lithium, additional lithium is locally and irreversibly trapped as lithiated graphite, contributing to the loss of lithium inventory (LLI) and to a local loss of active anode material. The total LLI in the cell from irreversibly plated lithium is linearly correlated to the capacity loss in the batteries after XFC cycling, with a non-zero offset originating from other parasitic side reactions. Finally, at the global (cell) scale, LLI drives the capacity fade, rather than electrode degradation. We anticipate that the understanding of lithium plating and other degradation mechanisms during XFC gained in this work will help lead to new approaches towards designing high-rate batteries in which irreversible lithium plating is minimized.

Electrolyte ordering near solid surfaces is of vital importance in diverse fields, ranging from physical chemistry, to energy storage, and heterogeneous catalysis. However, experimental determination of the structure of the electrode–electrolyte interface and electric double layer is challenging due to limited experimental approaches. In this work we show a detailed picture of the electrode–electrolyte interface relevant to Li-ion batteries. Specifically, we probe the atomic-scale interfacial structure of a non-aqueous liquid electrolyte solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) containing lithium hexafluorophosphate (LiPF6) salt via surface sensitive Angstrom resolution X-ray reflectivity (XRR). We complement our experimental results with molecular dynamics (MD) simulations, and find good agreement between the experiment and simulation derived density profiles. The surface at open circuit voltage (OCV) induces layering of electrolyte molecules near the interface, which decays towards the bulk, and we conclude that both EC and DMC molecules in the first interfacial layer tend to adsorb parallel to the surface. With increasing salt-concentration, the layering periodicity and the degree of order increase. We discuss implications of our results to Li-ion batteries, with focus on the relation between interfacial structure and ion transport in and out of the electrode.

Correction for ‘Quantification of heterogeneous, irreversible lithium plating in extreme fast charging of lithium-ion batteries’ by Partha P. Paul et al., Energy Environ. Sci., 2021, DOI: 10.1039/d1ee01216a.

Correction for ‘The nanoscale structure of the electrolyte–metal oxide interface’ by Hans-Georg Steinrück et al., Energy Environ. Sci., 2018, DOI: 10.1039/c7ee02724a.