The solid electrolyte interphase (SEI) is a multistructured
thin
layer that forms at the anode (e.g., lithium-metal)/electrolyte (e.g.,
ethylene carbonate EC) interface due to electrolyte reduction. At
the initial battery cycles, the SEI protects the electrolyte from
further reduction. However, the SEI continues to grow with time, leading
to capacity loss and eventually the death of the battery. In this
work, we modeled the battery-aging process at storage conditions (calendar
aging). We studied EC decomposition reactions using density functional
theory (DFT) simulations in the gas-phase in isolation and over the
inorganic layer found inside the SEI composed of Li2CO3. We used the values obtained from DFT alongside diffusion
coefficients from the literature to explore the temporal evolution
of the concentration of the species by kinetic Monte Carlo (kMC) simulations.
We found that reactions occurring over Li2CO3 (001) led to a relatively slow SEI growth which is compatible with
the general use of carbonate-based solvents in LIBs for protection/passivation
purposes. Our simulations over Li2CO3 (001)
predict the formation of a multilayered structured SEI. Moreover,
our kMC simulations predict the shift from a nonlinear initial behavior
to a linear behavior for the capacity loss induced by the formation
and growth of the SEI over time which was reported in previous experimental
and theoretical studies for lithiated graphite-based batteries. We
extended our analysis to the decomposition reactions over the Li2O (111) surface, which could form from the decomposition of
Li2CO3. We found that the selectivity of the
decomposition reactions strongly depends on the inorganic surface.
The main conclusion of this study is to highlight the crucial role
played by surface reactions inside the SEI on the nature and selectivity
of the decomposition kinetics of EC for the SEI growth.
In this work we strive to unravel the relationships between the two‐photon absorption (2PA) cross‐sections and structural modifications in an extended panel (280 compounds) of large difluoroborate dyes. More specifically, we use theoretical tools based on Time‐Dependent Density Functional Theory (TD‐DFT), to predict the one and two‐photon absorption properties of all compounds. The BF2‐carrying dyes usually posses a great interest for 2PA bioapplications as smartly designed BF2‐derivatives show good photophysical properties and high quantum yields in aqueous medium. For practical applications, it is important to maximize their 2PA response as well as absorption wavelength. This is why we explore here various strategies for maximizing the 2PA cross‐section: core modifications, multi‐branching, variation of the nature and length of the π‐conjugated linkers, addition of various donor and acceptor substituents. Our results suggest that large values of 2PA cross‐section and redshifted absorption wavelength can be achieved for all studied cores by using the vinylene‐type linkers and asymmetrical substitution with at least one strong peripheral donor group.
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