Inhibition of transition-metal dissolution with an inert soluble product interface constructed by high-concentration electrolyte

The formation of a compact and stable cathode electrolyte interphase (CEI) film is a promising way to improve the high voltage resistance of lithium-ion batteries (LIBs). However, challenges arise due to the corrosion of hydrogen fluoride (HF) and the dissolution of transition metal ions (TMs) in harsh conditions. To address this issue, researchers have constructed an anion-derived CEI film enriched with LiF and LiPO₂F₂ soluble product on the surface of LiNi_0.5Mn_1.5O₄ (LNMO) cathode in highly concentrated electrolytes (HCEs). The strong binding of LiF and LiPO₂F₂ generated an inert LiPO₂F₂ soluble product interface, which inhibited HF corrosion and maintained the spinel structure of LNMO, contributing to a capacity retention of 92% after 200 cycles at 55°C in the resulting cell with a soluble LiPO₂F₂-containing CEI film. This new approach sheds light on improving the electrode/electrolyte interface for high-energy LIBs.

The Drude-Smith Equation and Related Equations for the Frequency-Dependent Electrical Conductivity of Materials: Insight from a Memory Function Formalism

The Drude‐Smith equation is widely used for treating the frequency‐dependent electrical conductivity of materials in the terahertz region. An attractive feature is its sparsity of adjustable parameters. A significant improvement over Drude theory for these materials, the theory includes backscattering of the charge carriers. It has nevertheless been criticized, including by Smith himself, because of the arbitrariness of a step in the derivation. We recall a somewhat similar behavior of back scattering in fluids observed in molecular dynamics computations and discussed in terms of memory functions. We show how theories such as Drude‐Smith and Cocker et al. are examples of a broader class of theories by showing how they also arise as particular cases of a memory function formalism that divides the interactions into short and long range.

Molecular Dynamics and Emerging Network Graphs of Interactions in Dinitrile-Based Li-Ion Battery Electrolytes

Advancements in battery research have shown interesting formulations of battery electrolytes that have helped improve the efficiency of Li-ion batteries over the decades. However, the quest for a safer and affordable battery electrolyte still proceeds with more unique formulations reported in the literature regularly. The dinitriles, especially adiponitrile and glutaronitrile, have caught the attention of the research community as part of this quest. In this work, we performed molecular dynamics simulations of dinitrile electrolytes with lithium bistrifluorosulfonimide (LiTFSI) as the electrolyte salt at varying concentrations and temperatures. On analysis of our simulations, we find that the densities of the mixtures follow the same trend as that of experimental values. The solvation properties were explored using the radial distribution functions. The connectivity of the Li⁺ with the dinitrile molecules and anions is established for all of the electrolyte concentrations using network graphs. We observe that the electrolytes form highly networked structures as the concentration increases without being affected by the rise in temperature. The networking of ionic interactions was quantified by calculating the average degree of each graph. Ionic conductivity calculations were computed using three methods: Nernst-Einstein relation, correlated method, and current autocorrelation function. We report the importance of accounting for the correlated motion of ions while estimating the ionic conductivity. The correlated conductivity and current autocorrelation function calculations provide a satisfactory estimation of the ionic conductivity compared to the experimental values.

Ion Distribution and Hydration Structure at Solid-Liquid Interface between NaCl Crystal and Its Solution

The interface structure between NaCl crystal and its solution has been investigated at the saturated concentration of 298 K by molecular dynamics simulations. We have found that there are many fine structures at this complex interface. Near the surface of crystal, most of Na⁺ only coordinate with water molecules, while almost all Cl^- coordinate with Na⁺ in addition to water molecules. An ion coordinating with more water molecules is farther away from the epitaxial position of lattice. As approaching to the interface, the first hydration shell of ions has the tendency of being ordered, while the orientation of dipole of water molecules in the first hydration shell becomes more disordered than that in the solution. Generally, the first hydration shell of Na⁺ is less affected by nearest Cl^-, whereas the first hydration shell of Cl^- is significantly affected by nearest Na⁺.

Ionized aromatization approach to charged porous polymers as exceptional absorbents

One-step ionized aromatization approach to cyclopropenium cation-based porous polymers with ultra-high selective capture of anionic dyes in water.