Abstract
Rational design of active electrode materials is important for the development of advanced lithium and post-lithium batteries. Ab initio modeling can provide mechanistic understanding of the performance of prospective materials and guide design. We review our recent comparative ab initio studies of lithium, sodium, potassium, magnesium, and aluminum interactions with different phases of several actively experimentally studied electrode materials, including monoelemental materials carbon, silicon, tin, and germanium, oxides TiO2 and VxOy as well as sulphur-based spinels MS2 (M = transition metal). These studies are unique in that they provided reliable comparisons, i.e., at the same level of theory and using the same computational parameters, among different materials and among Li, Na, K, Mg, and Al. Specifically, insertion energetics (related to the electrode voltage) and diffusion barriers (related to rate capability), as well as phononic effects, are compared. These studies facilitate identification of phases most suitable as anode or cathode for different types of batteries. We highlight the possibility of increasing the voltage, or enabling electrochemical activity, by amorphization and p-doping, of rational choice of phases of oxides to maximize the insertion potential of Li, Na, K, Mg, Al, as well as of rational choice of the optimum sulfur-based spinel for Mg and Al insertion, based on ab initio calculations. Some methodological issues are also addressed, including construction of effective localized basis sets, applications of Hubbard correction, generation of amorphous structures, and the use of a posteriori dispersion corrections.
Highlights
Further down the periodic table, Ge was found to be effective for Li, with a specific capacity of about 1568 mAh g−1 [49] and faster diffusion for both Li and Na, but sodiation and magnesiation of Ge are inefficient, sodiation has been observed after prior pre-lithiation [50]
We found a similar effect of graphite and amorphous carbon (a-C)
We have reviewed our recent studies on Li, Na, K, Mg, and Al insertion in several structures which attracted significant research interest and have been extensively studied experimentally, including monoelemental materials, binary oxides, and sulfides
Summary
The number of possible ions is by far exceeded by the variety of host structures that can be used as electrode materials in electrochemical battery storage It is beyond the scope of this work to give an overview of all currently investigated electrode materials, but rather to outline the process of rational materials selection and prediction of crucial properties by modeling. A significant body of ab initio literature on modeling of electrode materials exists, mostly considering lithiation, to a smaller degree sodiation, and to a much smaller degree material interactions with prospective electrode materials for other types of batteries This body of work and respective reviews [8,9] establish that DFT can provide semi-quantitative, and sometimes quantitative, accuracy of estimates of voltage-capacity curves and ion diffusion barriers observed in experiments (with achievable accuracies on the order of a fraction of 1 V or 0.1 eV, respectively), even when modeling idealized bulk systems abstracting from microstructural or even interfacial effects. It is advantageous to have estimates of key electrode material properties for different materials and different ions made with the same approximations and the same computational setup
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