The Role of Na and Mg Doping on the Electronic Conductivity of LiFePO₄ : First-Principles Investigations

Abstract:

The effects of Na and Mg doped Li site for Li_1-xM_xFePO₄ have been studied using first-principles within GGA+U. Elastic band method has been used to calculate the activation energy for Li diffusion. The calculated results mean that, the band gaps of the Na and Mg doped Li_1-xM_xFePO₄ are both narrow than that of the un-doped. Especially Mg dopant gives rise to much narrow gap, which is attributed to the appearance of impurity level in the forbidden band of un-doped LiFePO4. The calculated activation energies for LiFePO₄, Li_0.875Na_{0.125Subscript text}FePO₄, and Li_0.875Mg_0.125FePO₄ are 0.33eV, 0.31 eV, and 0.15 eV, respectively. From the calculated results of band gap and activation energy, we can find that Mg dopant will benefit for the hopping of electrons and the improvement of the electronic conductivity for LiFePO₄.

• Periodical: Advanced Materials Research (Volume 629)
• Pages: 64-69
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.629.64
• Online since: December 2012
• Authors: Jing Wu, Gui Gui Xu, Ying Bin Lin, Zhi Gao Huang
• Keywords: Activation Energy, Dopant, First-Principle, LiFePO₄

References

[1] Padhi AK, Nanjundaswamy KS, Goodenough JB. Phospho-olivines as positive-electrode materials for rechargeable lithium batteries. J Electrochem Soc 1997; 144: 1188-94.

DOI: 10.1149/1.1837571

[2] Prosini PP. Modeling the voltage profile for LiFePO4. J Electrochem Soc 2005; 152: A1925-9.

[3] Islam MS, Driscoll DJ, Fisher CAJ, Slater PR. Atomic-scale investigation of defects, dopants, and lithium transport in the LiFePO4 olivine-type battery material. Chem Mater 2005; 17: 5085-92.

DOI: 10.1021/cm050999v

[4] Laffont L, Delacourt C, Gibot P, Wu MY, Kooyman P, Masquelier C, et al. Study of the LiFePO4/FePO4 two-phase system by high-resolution electron energy loss spectroscopy. Chem Mater 2006; 18: 5520-9.

DOI: 10.1021/cm0617182

[5] Sigle W, Amin R, Weichert K, van Aken PA, Maier J. Delithiation study of LiFePO4 crystals using electron energy-loss spectroscopy. Electrochem. Solid-State Lett. 2009; 12: A151-4.

DOI: 10.1149/1.3131726

[6] Maxisch T, Zhou F, Ceder G. Ab initio study of the migration of small polarons in olivine LixFePO4 and their association with lithium ions and vacancies. Phys Rev B 2006; 73: 104301.

DOI: 10.1103/physrevb.73.104301

[7] Chung SY, Bloking JT, Chiang YM. Electronically conductive phospho-olivines as lithium storage electrodes. Nat Mater 2002; 1: 123-8.

DOI: 10.1038/nmat732

[8] Ouyang CY, Wang DY, Shi SQ, Wang ZX, Li H, Huang XJ, et al. First principles study on NaxLi1-xFePO4 as cathode material for rechargeable lithium batteries. Chinese Phys Lett 2006; 23: 61-4.

[9] Ouyang XF, Shi SQ, Ouyang CY, Jiang DY, Liu DS, Ye ZQ, et al. First principles studies on the electronic structures of LiMxFe1-xPO4 ( M = Co, Ni, and Rh). Chinese Phys 2007; 16: 3042-7.

[10] Wang DY, Li H, Shi SQ, Huang X, Chen L. Improving the rate performance of LiFePO4 by Fe-site doping. Electrochim Acta 2005; 50: 2955-8.

DOI: 10.1016/j.electacta.2004.11.045

[11] Ouyang CY, Shi SQ, Wang ZX, Huang X, Chen L. First-principles study of Li ion diffusion in LiFePO4. Phys Rev B 2004; 69: 104303.

[12] Morgan D, Van der Ven A, Ceder G. Li conductivity in LixMPO4 (M = Mn, Fe, Co, Ni) olivine materials. Electrochem. Solid St. 2004; 7: A30-2.

DOI: 10.1149/1.1633511

[13] Dathar GKP, Sheppard D, Stevenson KJ, Henkelman G. Calculations of Li-ion diffusion in olivine phosphates. Chem Mater 2011; 23: 4032-7.

DOI: 10.1021/cm201604g

[14] Zaghib K, Mauger A, Goodenough JB, Gendron F, Julien CM. Electronic, optical, and magnetic properties of LiFePO4: small magnetic polaron effects. Chem Mater 2007; 19: 3740-7.

DOI: 10.1021/cm0710296

[15] Liu ZJ, Huang XJ, Wang DS. First-principle investigations of N doping in LiFePO4. Solid State Commun 2008; 147: 505-9.

DOI: 10.1016/j.ssc.2008.06.013

[16] Kresse G, Furthmüller J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys Rev B 1996; 54: 11169-86.

DOI: 10.1103/physrevb.54.11169

[17] Xu GG, Wu QY, Chen ZG, Huang ZG, Wu RQ, Feng YP. Disorder and surface effects on work function of Ni-Pt metal gates. Phys Rev B 2008; 78: 115420.

DOI: 10.1103/physrevb.78.115420

[18] Weng ZZ, Zhang JM, Huang ZG, Lin WX. Effect of oxygen vacancy defect on the magnetic properties of Co-doped ZnO. Chinese Phys B 2011; 20: 027103.

DOI: 10.1088/1674-1056/20/2/027103

[19] Perdew JP, Chevary JA, Vosko SH, Jackson KA, Pederson MR, Singh DJ, et al. Atoms, molecules, solids, and surfaces: Applications of the generalized gradient approximation for exchange and correlation. Phys Rev B 1992; 46: 6671-87.

DOI: 10.1103/physrevb.46.6671

[20] Zhou F, Cococcioni M, Marianetti CA, Morgan D, Ceder G. First-principles prediction of redox potentials in transition-metal compounds with LDA+U. Phys Rev B 2004; 70: 235121.

DOI: 10.1103/physrevb.70.235121

[21] Zhou F, Kang K, Maxisch T, Ceder G, Morgan D. The electronic structure and band gap of LiFePO4 and LiMnPO4. Solid State Commun 2004; 132: 181-6.

DOI: 10.1016/j.ssc.2004.07.055

[22] Mills G, Jónsson H, Schenter GK. Reversible work transition state theory: application to dissociative adsorption of hydrogen. Surf Sci 1995; 324: 305-37.

DOI: 10.1016/0039-6028(94)00731-4

[23] Liu ZJ, Huang XJ. Factors that affect activation energy for Li diffusion in LiFePO4: A first-principles investigation. Solid State Ionics 2010; 181: 907-13.

DOI: 10.1016/j.ssi.2010.05.020

[24] Shi SQ, Liu LH, Ouyang CY, Wang DS, Wang Z, Chen L, et al. Enhancement of electronic conductivity of LiFePO4 by Cr doping and its identification by first-principles calculations. Phys Rev B 2003; 68: 195108.

[25] Guo ZP, Liu H, Bewlay S, Liu HK, Dou SX. Start-fine-particle carbon-enriched Li0. 98Mg0. 02FePO4 synthesized by a novel modified solid-state reaction. Synth Met 2005; 153: 113-6.

DOI: 10.1016/j.synthmet.2005.07.220

[26] Ong SP, Chevrier VL, Ceder G. Comparison of small polaron migration and phase separation in olivine LiMnPO4 and LiFePO4 using hybrid density functional theory. Phys Rev B 2011; 83: 075112.