First-principles investigation of the electronic and Li-ion diffusion properties of LiFePO4 by sulfur surface modification

Abstract

We present a first-principles calculation for the electronic and Li-ion diffusion properties of the LiFePO 4 (010) surface modified by sulfur. The calculated formation energy indicates that the sulfur adsorption on the (010) surface of the LiFePO 4 is energetically favored. Sulfur is found to form Fe-S bond with iron. A much narrower band gap (0.67 eV) of the sulfur surface-modified LiFePO 4 [S-LiFePO 4 (010)] is obtained, indicating the better electronic conductive properties. By the nudged elastic band method, our calculations show that the activation energy of Li ions diffusion along the one-dimensional channel on the surface can be effectively reduced by sulfur surface modification. In addition, the surface diffusion coefficient of S-LiFePO 4 (010) is estimated to be about 10 À11 (cm 2 /s) at room temperature, which implies that sulfur modification will give rise to a higher Li ion carrier mobility and enhanced electrochemical performance. V C 2014 AIP Publishing LLC.

Emergence of Metallic Properties at LiFePO4 Surfaces and LiFePO4/Li2S Interfaces: An Ab Initio Study

“…Due to the changes in volume between S 8 and Li 2 S phases, the coating shell is destroyed which turns the LFP-sulfur composite with a "protected" sulfur core into a mixture of independent sulfur and (carbon-coated) LFP particles. 12 In this situation, the decarbonized surface areas of LFP particles can potentially be sulfidated, 13,14 and, at the final stage of reaction, may potentially serve as a "substrate" for Li 2 S growth.…”

A review on first principles based studies for improvement of cathode material of lithium ion batteries

“…Xu explained the electronic and lithium ion diffusion properties upon sulfur coating on the surface of LiFePO 4 (010) [156] . A much narrow and tight band gap of 0.67 eV for sulfur coated LiFePO 4 [S-LiFePO 4 (010)] was obtained which indicated the fantastic electronic properties.…”

“…explained for the first time the correlation between the lithium diffusion and possible instability in LiMPO 4. Studies using neutron inelastic scattering experiments were reported [152] .…”

“…The experimental results were in good agreement with the theoretical calculations. Lattice dynamics calculations indicated the instability of zone-center as well as zone-boundary phonon modes at the [100] direction is the result of elevated temperature [152] .…”

A first-principles study of bulk and surface Sn-doped LiFePO4 : The role of intermediate valence component in the multivalent doping

“…Despite the many excellent properties of LiFePO 4 , such as good thermal stability, environmental benignity and relatively low cost, one of its primary disadvantages is its low intrinsic electronic conductivity (10 À9 $ 10 À10 S cm À1 ) [10]. To improve the electrochemical performance of LiFePO 4 , extensive research has focused on the development of coatings [11][12][13][14][15][16][17][18] (such as carbon, metal, or metal oxides), particle size minimization [2,12,19,20], doping techniques [10,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] and so on. Among these treatments, doping may have advantages over the others in the enhancement of the intrinsic electrical conductivity with no loss of energy density due to introducing nonactive materials (C coating) or void spaces (nanoparticle assembling).…”