Enhancement of Electrochemical Properties of Lithium Rich Li₂RuO₃ Cathode Material

Abstract

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.

Multiscale Investigation into the Co‐Doping Strategy on the Electrochemical Properties of Li2RuO3 Cathodes for Li‐Ion Batteries

“…By considering the calculated energy for FM spin‐states (35204.5 eV) which is lower than antiferromagnetic AFM spin‐states of LRO (35202.1), the FM spin‐states is used for investigation into the studied cathodes and it is compatible with other researches [5] . TDOS and PDOS for p orbitals of O atoms in the cathodes and d orbitals related to the transition metals for the FM spin‐states are reported in Figure 4a and Figure 4b, respectively.…”

“…Unfortunately, commercialized cathodes have various drawbacks that barricade them from being used in electric vehicles (EVs). These include poor rate performance, low energy density, and inferior cycling stability [5,6] . Recently, lithium‐rich layered oxides (LLOs) have received a lot of attention as promising cathode materials, [7–16] which can be generally written as Li 2 MO 3 (M=Mn, Co, Ru, etc.).…”

“…However, LROs also have drawbacks such as oxygen loss, poor electrochemical kinetics, low Li‐ion diffusion coefficient, and large voltage reduction, that need to be mitigated [22–25] . For example, the diffusion coefficient of LRO is about 1.15×10 −11 (cm 2 s −1 ) and it has been shown that it can be increased by 20 % via doping strategies [5] . Some investigations have highlighted the problems and have investigated coating and doping strategies.…”

“…These include poor rate performance, low energy density, and inferior cycling stability. [5,6] Recently, lithium-rich layered oxides (LLOs) have received a lot of attention as promising cathode materials, [7][8][9][10][11][12][13][14][15][16] which can be generally written as Li 2 MO 3 (M=Mn, Co, Ru, etc.). Although LLO cathodes have shown efficient characteristics like high reversible capacity (above 250 mAh g À 1 ) [17] in a higher operational voltage (4.8, vs. Li + /Li) [18] and high energy density (1000 Wh kg À 1 ), [17] many efforts have been made to enhance the electrochemical properties of these positive cathodes to tackle the drawbacks such as first cycle capability loss and poor structural stability.…”

First‐principle study of doping effects (Ti, Cu, and Zn) on electrochemical performance of Li2MnO3 cathode materials for lithium‐ion batteries

“…in all results of doped cathodes, but the overall conclusion was not affected. So, in this work, the same as Kong et al [ 47 ] and other researchers such as Moradi et al, [ 60 ] the DFT‐GGA method was employed to evaluate free Gibbs energy change for Equation ).…”