Since the first lithium-ion batteries (LIBs) commercialized by Sony Corporation in 1991, they are being considered as the most suitable technology for electric vehicles and stationary energy storage systems. [1][2][3][4] Most of commercial LIBs are based on graphite anode due to their high energy density (high capacity of 372 mAh g −1 and low de-/lithiation potential around 0.1 V vs Li/Li + ), [5] long cycle life, low cost and environmental friendliness. [4,[6][7][8][9][10][11] With the motive to accelerate worldwide market adoption of electrical vehicles and provide better user experience, it is an inevitable trend to develop fast charging technology. However, the graphite is still a barrier that hampers high-rate performance of commercial LIBs. [6,9] During charge process, Li ions migrate to the anode and are desired to be inserted into the layered structure of graphite, but Li ions can also be directly reduced to metallic Li under high overpotential, which generally occurs at high charging rates or low temperatures, resulting in rapid decay of electrochemical performances and thermal safety concerns. [12][13][14] In order to address these problems, extensive efforts have been engaged, [14][15][16][17][18][19] but the mechanism of capacity decay of graphite after Li-plating is still unclear. In this work, we aim to describe the mechanism of lithium evolution from intercalated ions in graphite to Li metal plating on graphite particle surfaces by over-lithiation cycle test, in-situ XRD, and titration gas chromatography (TGC). We deteriorate the conditions of lithium plating on graphite and find the Li insertion/deintercalation machnism vanish fast in graphite particles. Our results demonstrate that the graphite intercalation compounds (GICs: LiC 12 , LiC 6 e.g.) gradually become inactive and wrapped by dead lithium or side reaction sediments, and the intercalated Li-ions cannot be stripped from GICs. The isolation of GICs particles leads to fast graphite loss. This insertion/deintercalation vanishing process will be accelerated at low temperature and high rates. The new insight on graphite anode degradation induced by Li-plating can be used to guide the design of advanced materials and electrodes to achieve extreme fast charging. Results and Discussion The Electrochemical Performance of Graphite|Li During Over-Lithiation ProcessThe morphologies of graphite particles are characterized by SEM and TEM, as shown in the inset of Figure 1a and Figure S1. The particles

Summary Calendar life accounts for most of the lifetime of the power lithium‐ion battery applied in electric vehicles, and thus should be investigated in detail. In this paper, a mechanistic calendar aging model of lithium‐ion battery is developed by adding the solid electrolyte interface (SEI) growth side reaction to the pseudo‐two‐dimensional electrochemical model. The model can accurately simulate the capacity degradation and evolution of the charging voltage profiles of a Lix(NiCoMn)1/3O2 ‐ graphite battery during high‐temperature (55°C) storage under various states of charge. The model is further validated by comparing the electrode degradations inside the batteries after calendar aging. The model predicted electrode degradations are consistent with the results identified using a dual‐tank model and post‐mortem analysis, confirming that SEI growth is the dominant degradation mechanism. Based on the validated model, internal changes in electrodes' structure induced by SEI growth during calendaring aging are discussed. The anodes of the calendar‐aged batteries suffer from severe pore clogging and film resistance increase, resulting in apparent power performance degradation of lithium‐ion battery. Finally, modeling analysis is conducted to find possible solutions to mitigate the battery calendar aging process. Rational designs of SEI by reducing the porosity and solvent diffusivity inside the SEI and the kinetic rate constant turn out to be effective in improving the calendar lifetime of lithium‐ion batteries. Novelty Statement Calendar life accounts for most of the lifetime of the lithium‐ion battery in electric vehicles. This study establishes a mechanistic calendar aging model of lithium‐ion battery considering solid electrolyte interface growth. The model can not only simulate the battery capacity degradation and the evolution of battery charging voltage profiles but also capture the internal degradation of the electrodes during the aging process. Modeling analysis is further conducted to find possible solutions to mitigate the calendar aging process of lithium‐ion battery.

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