Compactness of the Lithium Peroxide Thin Film Formed in Li–O₂ Batteries and Its Link to the Charge Transport Mechanism: Insights from Stochastic Simulations

Abstract

We simulated the discharge process of Li-O batteries and the growth of LiO thin films at the mesoscale with a novel kinetic Monte Carlo model, which combined a stochastic description of mass transport and detailed elementary reaction kinetics. The simulation results show that the ordering of the LiO thin film is determined by the interplay between diffusion and reaction kinetics. Due to the fast reaction kinetics on the catalyst, the LiO formed in the presence of catalyst (cat-CNF) shows a low degree of ordering and is more likely to be amorphous. Moreover, the mobility of the LiO ion pair, which depends largely on the nature of the electrolyte, also impacts the homogeneity of the compactness of the LiO thin film. These results are of high importance for understanding the role of the catalyst and reaction kinetics in Li-O batteries.

Reaction chemistry in rechargeable Li–O2batteries

“…92 Similarly, kinetic Monte Carlo simulation predicts the formation of an amorphous Li 2 O 2 phase when a metal catalyst is present in the cell. 125 As discussed above, the defective Li 2 O 2 exhibits better transport properties than the crystalline phase and can thus be beneficial for the decomposition reaction. Moreover, Song et al recently suggested that the metal catalyst can promote the decomposition of by-product Li 2 CO 3 , which significantly passivates the air electrode, resulting in improved cycle life.…”

Entering the Augmented Era: Immersive and Interactive Virtual Reality for Battery Education and Research**

“…The cylindrical pore represents a geometrical simplification of the actual porous mesostructure of a LOB cathode, to provide the students with a straight‐forward impression of the implications of the Li 2 O 2 formation mechanism depending on their way of driving the EV. Li 2 O 2 is represented in orange color and its formation and spatial localization along the radius and the length of the cylinder is controlled via a lookup table interpolating values pre‐calculated using a kinetic Monte Carlo (kMC) model reported by us elsewhere [63–64] . A lookup table is a data structure stored in the computer memory which is used to replace a calculation by a simple operation of consultation.…”

“…The representation of the evolution of the cathode mesostructures in the game follows a similar strategy as in The Great Li–Air Escapade VR : lookup tables are built based on calculations carried out by using simplified versions of models previously reported by us [56,64, 67] . In the LSB case, the (carbon‐based) cathode evolution representation is more complex (Figure 21).…”

Exclusive solution discharge in Li-O2 batteries

“…Since even small amounts of water in low DN electrolytes could strongly alter product growth 14 , we meticulously excluded any unintended water contamination as detailed in Supplementary Note 2. The thickness of conformal layers allowed by electron tunneling is often considered ≈7 nm 22,23,40 , although the exact number depends on the applied current 40 , the potential 41 , the concentration of defects or Li2O2 crystallinity 42,43 , the homogeneity of the film 44 , and the presence of catalysts 45 . The morphology is expected to be film-like, as the particle thickness growth is selflimited by the drastic increase in resistivity with increasing thickness 46 .…”