Abstract
In recent years, the scientific community has shown an increasing interest in regards to the investigation of novel materials for the intercalation of lithium atoms, suitable for application as cathodes in the new generations of Li-ion batteries. Within this framework, we have computed the relative structural stability, the electronic structure, the elastic and dynamic properties of Li2MSiO4 compounds (M = Mn, Co, Ni) by means of first-principles calculations based on density functional theory. The so-obtained structural parameters of the examined phases are in agreement with previous reports. The energy differences between different polymorphs are found to be small, and most of these structures are dynamically stable. The band structures and density of states are computed to analyse the electronic properties and characterise the chemical bonding. The single crystal elastic constants are calculated for all the examined modifications, proving their mechanical stability. These Li2MSiO4 materials are found to present a ductile behaviour upon deformation. The diffusion coefficients of Li ions, calculated at room temperature for all the examined modifications, reveal a poor conductivity for this class of materials.
Highlights
Lithium-ion batteries present an excellent combination of high energy and power density and are currently the most promising technology for energy storage devices as well as for electric vehicles [1,2]
The dynamical matrices were calculated from the force constants, and phonon density of states (PhDOS) curves were computed on a Monkhorst-Pack grid [41]
To determine the minimum energy path (MEP) through the Nudged Elastic Band (NEB) method [42,43], five replicas of the system were created by linear interpolation between the initial and final states
Summary
Lithium-ion batteries present an excellent combination of high energy and power density and are currently the most promising technology for energy storage devices as well as for electric vehicles [1,2]. Researching novel materials exhibiting a high specific capacity and good retention of the latter upon electrochemical cycling, as well as high operating voltage is crucial in order to advance the overall state of the art of Li-ion-based battery technology In this context, the main advantage of polyoxyanion intercalation compounds with respect to transition metal oxides is the greater stability upon intercalation/deintercalation of Li+ ions, ensured by the covalence of the bonding between oxygen and the non-metallic atom (e.g., P, Si).
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