At present the most successful rechargeable battery is the Li-ion battery, due to the small size, high energy density, and low reduction potential of Li. Computational materials science has become an increasingly important tool to study these batteries, and in particular cathode properties. In silico studies of cathode materials have proven to be a valuable tool to understand the workings of cathodes, without having to do sophisticated experiments. First-principles and empirical computations have been used by various groups to study key properties, such as structural stability, electronic structure, ion diffusion mechanisms, equilibrium cell voltage, thermal and electrochemical stability, and surface behavior of Li-ion battery cathode materials. Arguably, the most practical and promising Li-ion cathode materials today are layered oxide materials, and in particular LiNi 1−x−y Co x Mn y O 2 (NCM) and LiNi 1−x−y Co x Al y O 2 (NCA). Here, some of the computational approaches to studying Li-ion batteries, with special focus on issues related to layered materials, are discussed. Subsequently, an overview of theoretical and related experimental work performed on layered cathode materials, and in particular on NCM and NCA materials, is provided.

The methyl groups in TetMe-IBX lower the activation energy corresponding to the rate-determining hypervalent twisting (theoretical calculations), and the steric relay between successive methyl groups twists the structure, which manifests in significant solubility in common organic solvents. Consequently, oxidations of alcohols and sulfides occur at room temperature in common organic solvents. In situ generation of the reactive TetMe-IBX from its precursor iodo-acid, i.e., 3,4,5,6-tetramethyl-2-iodobenzoic acid, in the presence of oxone as a co-oxidant facilitates the oxidation of diverse alcohols at room temperature.

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Ni-rich layered oxide LiNi1 – x – y Co x Mn y O2 (1 – x – y > 0.5) materials are favorable cathode materials in advanced Li-ion batteries for electromobility applications because of their high initial discharge capacity. However, they suffer from poor cycling stability because of the formation of cracks in their particles during operation. Here, we present improved structural stability, electrochemical performance, and thermal durability of LiNi0.85Co0.1Mn0.05O2(NCM85). The Nb-doped cathode material, Li­(Ni0.85Co0.1Mn0.05)0.997Nb0.003O2, has enhanced cycling stability at different temperatures, outstanding capacity retention, improved performance at high discharge rates, and a better thermal stability compared to the undoped cathode material. The high electrochemical performance of the doped material is directly related to the structural stability of the cathode particles. We further propose that Nb-doping in NCM85 improves material stability because of partial reduction of the amount of Jahn–Teller active Ni3+ ions and formation of strong bonds between the dopant and the oxygen ions, based on density functional theory calculations. Structural studies of the cycled cathodes reveal that doping with niobium suppresses the formation of cracks during cycling, which are abundant in the undoped cycled material particles. The Nb-doped NCM85 cathode material also displayed superior thermal characteristics. The coherence between the improved electrochemical, structural, and thermal properties of the doped material is discussed and emphasized.

the oceans. Thus, sodium storage systems would likely be far more economically competitive for large-format applications where low price, little pollution, and long cycle life may outweigh energy density considerations. [3] In recent years, rechargeable aqueous sodium-ion battery systems received attention as large-scale energy storage systems owing to their various potential merits. Aqueous batteries are non-flammable, environmentally friendly, and have great potential to be low cost. [4] In the last decade, several cathode compounds were reported to couple with Na-compatible anodes to form full cells including Prussian blue analogs, [5] polyanionic compounds, [6] vanadium oxides, [7] and manganese oxides. [8] Manganese-based cathodes have received particular attention due to their low cost and earth abundance in comparison to other transition metal-based cathodes. Tunnel-structured Na 0.4 MnO 2 (NMO) is of particular interest as cathode material owing to its unique large tunnels that are suitable for sodium intercalation in both aqueous and non-aqueous electrolyte solutions. [9,10] The crystal structure of Na 0.4 MnO 2 is shown in Figure 1a. This system usually exists in the orthorhombic structure. There are five crystallographic manganese sites; the first two are occupied by Mn 3+ , and the latter are occupied by Mn 4+. These crystallographic attributes exhibit a unique charge ordering as reported by previous computational studies. [11] The structure framework is based on double and triple linear chains using edge-shared Mn(2-5)O 6 octahedra and single chains of corner-shared Mn(1)O 5. The three different sodium sites are shown within the tunnel frame, assembled by MnO 6 and MnO 5 polyhedrons. Two sites (Na(2) and Na(3)) are situated in large "S" shaped cavities (Figure 1b), the third site, Na(1), is located in smaller tunnels (Figure 1c). Typically, manganese-based cathode structures are unstable during redox reactions due to Jahn-Teller distortions. However, this tunnel-type structure is very stable, even during long-term electrochemical sodium intercalation and deintercalation reactions in an aqueous solution. Nevertheless, Na 0.4 MnO 2 still faces significant barriers to commercialization as a large-scale energy storage system. These barriers stem, in large, from the limited electrochemical performance, in particular the stability, rate capability, and discharge capacity.