The effect of Cr doping on Li ion diffusion in LiFePO₄from first principles investigations and Monte Carlo simulations

Abstract

Using the adiabatic trajectory method, the migration energy barriers for the migration of Li ions and Cr ions along the one-dimensional diffusion pathway in pure and Cr doped LiFePO4 are obtained from first principles calculations. The results show that while Li ions can diffuse along the diffusion pathway easily, Cr ions do not easily diffuse away from their initial positions. This means that the heavy Cr ions will block the one-dimensional diffusion pathway of the material. Monte Carlo simulations are performed to evaluate the influences of the blocking behaviours on the electrochemical performance of LiFePO4 cathode material for Li ion secondary batteries. The results show that the evaluated capacity is highly sensitive to the amount of the dopant, the size of the super-cell being used for simulation (particle size of the powder cathode material) and the Monte Carlo steps for statistics (charge–discharge current density).

Research on Advanced Materials for Li‐ion Batteries

“…[146] Because of the feature of 1D ionic transport, it was necessary to know whether the Cr ions in the Li sites could block the diffusion of Li ions along the 1D diffusion pathway. [147] We performed ab initio density functional theory (DFT)-based calculations using the Vienna ab initio simulation package VASP. [148][149][150][151] This code solves the Kohn-Sham equations within the pseudopotential approximation whereby the electrons are described in the local-density approximation (LDA) by ultrasoft pseudopotentials.…”

Atomic Level Investigations of Lithium Ion Battery Cathode Materials

“…7) A number of ab initio simulations of both systems have also been reported in the literature, providing details of electronic structure and related properties. [8][9][10][11][12][13][14] In this paper we compare and contrast defect formation, ion migration mechanisms and surfaces in the layered oxide LiCoO 2 and orthophosphates LiMPO 4 , where M = Mn, Fe, Co or Ni, using a classical potential model. The advantage of this model is that it enables the treatment of a much larger number of ions in any given simulation, an important aspect in handling the long-scale perturbations that arise from lattice point defects and surfaces.…”

Ab initio Studies on Li4+xTi5O12 Compounds as Anode Materials for Lithium‐Ion Batteries

“…[9,10] The reliability of first principles calculations has been tested in predicting both the structural and electronic properties of different kinds of electrode materials. Here, our first principles calculations lead to positive predictions regarding the possibility of further intercalating lithium in Li 7 Ti 5 O 12 -based on structure, intercalation potential, and electronic structure.…”