Four novel cathode electrode materials with improved material properties have been derived from the Lithium Manganese Oxide spinel using co‐doping strategies. Specifically, Aluminum, Nickel, Magnesium, and Yttrium were selected as the primary dopant to replace a fraction of Mn3+ (5 %), and S2− was selected as the secondary dopant to replace 1 % of O2−. A combination of quantum mechanics and molecular dynamics was used to study the fracture mechanics of the new materials for various State of Charge values, and improved performance is validated with experimental data. The results show that lattice constant values for all the doped structures decrease by 1.87 %–2.07 %. Overall, with co‐doping, the diffusion properties improved, and activation energy required for Li+ vacancy migration reduced (0.21–0.25 eV). We conclude that with reduced inter‐atomic distance, the overall life of the LMO spinel can be improved. The Computational Fluid Dynamics simulations to study the macro‐scale behaviour of these new materials shows a reduction in intercalation induced stress and heat generation.
The
solid–electrolyte interface (SEI) layer has a critical
role in Li-ion batteries’ (LIBs) life span. The SEI layer,
even in modern commercial LIBs, is responsible for more than 50% of
capacity loss. Due to the inherent complexity in studying the SEI
layer, many aspects of its performance and characteristics, including
diffusion mechanisms in this layer, are unknown. As a result, most
mathematical models use a constant value of the diffusion coefficient,
instead of a variable formulation, to predict LIBs’ properties
and performance such as capacity fading and the SEI growth rate. In
this work, by employing a multiscale investigation using a combination
of quantum mechanics, molecular dynamics, and macroscale mathematical
modeling, some equations are presented to evaluate the energy barrier
against diffusion and the diffusion coefficient in different crystal
structures in the inner section of the SEI layer. The equations are
evaluated as a function of temperature and concentration and can be
used to study the diffusion mechanism in the SEI layer. They can also
be integrated with other mathematical models of LIBs to increase the
accuracy of the latter.
Lithium-rich layered Ru-based oxides are interesting cathode materials due to their high energy density and reversible capacity. However, their poor structural stability and voltage decay hinder their broad commercial applicability. To address this, we investigate the co-doping strategy on Li 2 RuO 3 (LRO) for improved battery performance using a combination of quantum mechanics, molecular dynamics, and pseudo-1-dimensional (P1D) formulations. Specifically, in addition to the effect of Ti as a dopant in Li 2 Ru 0.5 Ti 0.5 O 3 (LTO), the effect of three co-dopants, Tc, Rh, or Pd in Li 2 Ru 0.5 Ti 0.25 M 0.25 O 3 has also been studied. It has been found that the co-doping strategy significantly improves the thermal stability of LRO. Tc and Ti improve structural stability by reducing the oxygen removal reaction. Pd and Tc reduce the bandgap considerably, leading to higher electrical conductivity. The results show that co-doping minimizes the energy required for Li-ions diffusion. In particular, Tc significantly enhances the Li-ions diffusion in LRO and LTO. Further co-dopants Rh, Pd, and Tc improve the maximum voltage of LRO, as well as the voltage stability by reducing the voltage reduction. Finally, P1D simulations show that while LTO provides the highest voltage and power operation, doping it with Tc and Pd increases its efficiency by reducing the ohmic potential drop and diffusion polarization.
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