The defect chemistry of LiFePO4 prepared by hydrothermal method at different pH values

Abstract LiFePO 4 has attracted broad attention as a promising cathode material for lithium ion batteries. One of the key issues related to LiFePO 4 performance lies on the intrinsic characteristic of Li/Fe inter-site mixing. To explore the effect of the defect chemistry on electrochemical behavior, LiFePO 4 is synthesized by hydrothermal method with pH value varying from 11.04 to 5.40. The results show that pure phase of LiFePO 4 could only be obtained at slightly basic and neutral conditions, and Rietveld refinements reveal that the degree of vacancies and inter-site mixing increase with decreasing pH value. The amounts of Fe on Li sites is nearly zero at pH value of 8.19, whereas 3.5% at 6.30. EIS measurements confirm that the occupation of Fe on Li sites will block the one-dimensional tunnel for lithium ion diffusion. It is vital to prevent the defect chemistry of LiFePO 4 by optimizing the synthesis conditions.

[1]  M. Whittingham,et al.  Lithium batteries and cathode materials. , 2004, Chemical reviews.

[2]  John B. Goodenough,et al.  Effect of Structure on the Fe3 + / Fe2 + Redox Couple in Iron Phosphates , 1997 .

[3]  F. Gao,et al.  Kinetic behavior of LiFePO4/C cathode material for lithium-ion batteries , 2008 .

[4]  M. Whittingham,et al.  Hydrothermal synthesis of lithium iron phosphate cathodes , 2001 .

[5]  K. Kanamura,et al.  Hydrothermal synthesis of LiFePO4 as a cathode material for lithium batteries , 2008 .

[6]  R. Frech,et al.  Raman and FTIR Spectroscopic Study of Li x FePO4 ( 0 ⩽ x ⩽ 1 ) , 2004 .

[7]  K. Kanamura,et al.  Identification of Surface Impurities on LiFePO4 Particles Prepared by a Hydrothermal Process , 2005 .

[8]  K. Uematsu,et al.  Enhanced electrochemical performance of LiFePO4 prepared by hydrothermal reaction , 2004 .

[9]  Peter R. Slater,et al.  Atomic-Scale Investigation of Defects, Dopants, and Lithium Transport in the LiFePO4 Olivine-Type Battery Material , 2005 .

[10]  A. Yamada,et al.  Comparative Kinetic Study of Olivine Li x MPO 4 ( M = Fe , Mn) , 2004 .

[11]  K. S. Nanjundaswamy,et al.  Phospho‐olivines as Positive‐Electrode Materials for Rechargeable Lithium Batteries , 1997 .

[12]  I. Willner,et al.  Cover Picture: Increasing the Complexity of Periodic Protein Nanostructures by the Rolling‐Circle‐Amplified Synthesis of Aptamers (Angew. Chem. Int. Ed. 1/2008) , 2008 .

[13]  Montse Casas-Cabanas,et al.  Room-temperature single-phase Li insertion/extraction in nanoscale Li(x)FePO4. , 2008, Nature materials.

[14]  Jae-won Lee,et al.  Characteristics of lithium iron phosphate (LiFePO4) particles synthesized in subcritical and supercritical water , 2005 .

[15]  A. Yamada,et al.  Experimental visualization of lithium diffusion in LixFePO4. , 2008, Nature materials.

[16]  DokkoKaoru,et al.  Electrochemical Reactivity of LiFePO4 Prepared by Hydrothermal Method , 2006 .

[17]  K. Kanamura,et al.  Formation of impurities on phospho-olivine LiFePO4 during hydrothermal synthesis , 2005 .

[18]  Jiajun Chen,et al.  Hydrothermal synthesis of lithium iron phosphate , 2006 .

[19]  Craig A. J. Fisher,et al.  Lithium Battery Materials LiMPO4 (M = Mn, Fe, Co, and Ni): Insights into Defect Association, Transport Mechanisms, and Doping Behavior , 2008 .

[20]  Masao Yonemura,et al.  Room-temperature miscibility gap in LixFePO4 , 2006, Nature materials.

[21]  L. Nazar,et al.  Nano-network electronic conduction in iron and nickel olivine phosphates , 2004, Nature materials.

[22]  Yet-Ming Chiang,et al.  Electronically conductive phospho-olivines as lithium storage electrodes , 2002, Nature materials.

[23]  Xiaozhen Liao,et al.  Low-temperature performance of LiFePO4/C cathode in a quaternary carbonate-based electrolyte , 2008 .

[24]  C. Delmas,et al.  Lithium deintercalation in LiFePO4 nanoparticles via a domino-cascade model. , 2008, Nature materials.

[25]  Yong Ding,et al.  Multi-quantum-well nanowire heterostructures for wavelength-controlled lasers. , 2008, Nature materials.

[26]  Kaoru Dokko,et al.  Electrochemical properties of LiFePO4 prepared via hydrothermal route , 2007 .

[27]  D. Xia,et al.  Synthesises, characterizations and electrochemical properties of spherical-like LiFePO4 by hydrothermal method , 2008 .

[28]  Peter Y. Zavalij,et al.  The hydrothermal synthesis and characterization of olivines and related compounds for electrochemical applications , 2008 .

[29]  Jean-Marie Tarascon,et al.  The existence of a temperature-driven solid solution in LixFePO4 for 0 ≤ x ≤ 1 , 2005 .