Two-dimensional lithium diffusion behavior and probable hybrid phase transformation kinetics in olivine lithium iron phosphate

Olivine lithium iron phosphate is a technologically important electrode material for lithium-ion batteries and a model system for studying electrochemically driven phase transformations. Despite extensive studies, many aspects of the phase transformation and lithium transport in this material are still not well understood. Here we combine operando hard X-ray spectroscopic imaging and phase-field modeling to elucidate the delithiation dynamics of single-crystal lithium iron phosphate microrods with long-axis along the [010] direction. Lithium diffusivity is found to be two-dimensional in microsized particles containing ~3% lithium-iron anti-site defects. Our study provides direct evidence for the previously predicted surface reaction-limited phase-boundary migration mechanism and the potential operation of a hybrid mode of phase growth, in which phase-boundary movement is controlled by surface reaction or lithium diffusion in different crystallographic directions. These findings uncover the rich phase-transformation behaviors in lithium iron phosphate and intercalation compounds in general and can help guide the design of better electrodes.Lithium transport and phase transformation kinetics in olivine LiFePO4 electrode remain not fully understood. Here the authors show that microsized olivine particles possess 2D lithium diffusivity and exhibit a possible hybrid mode of phase boundary migration upon cycling.

[1]  Nae-Lih Wu,et al.  Study on dynamics of structural transformation during charge/discharge of LiFePO4 cathode , 2008 .

[2]  W. Chueh,et al.  Tracking Non‐Uniform Mesoscale Transport in LiFePO4 Agglomerates During Electrochemical Cycling , 2015 .

[3]  Rahul Malik,et al.  Kinetics of non-equilibrium lithium incorporation in LiFePO4. , 2011, Nature materials.

[4]  Byoungwoo Kang,et al.  Battery materials for ultrafast charging and discharging , 2009, Nature.

[5]  Long-Qing Chen,et al.  Defects, Entropy, and the Stabilization of Alternative Phase Boundary Orientations in Battery Electrode Particles , 2016 .

[6]  Stéphanie Belin,et al.  An Electrochemical Cell for Operando Study of Lithium Batteries Using Synchrotron Radiation , 2010 .

[7]  Chunsheng Wang,et al.  Galvanostatic Intermittent Titration Technique for Phase-Transformation Electrodes , 2010 .

[8]  Charles Delacourt,et al.  Study of the LiFePO4/FePO4 Two-Phase System by High-Resolution Electron Energy Loss Spectroscopy , 2006 .

[9]  N. Sharma,et al.  Direct evidence of concurrent solid-solution and two-phase reactions and the nonequilibrium structural evolution of LiFePO4. , 2012, Journal of the American Chemical Society.

[10]  Rahul Malik,et al.  Particle size dependence of the ionic diffusivity. , 2010, Nano letters.

[11]  Martin Z. Bazant,et al.  Intercalation dynamics in rechargeable battery materials : General theory and phase-transformation waves in LiFePO4 , 2008 .

[12]  Young-Sang Yu,et al.  Visualization of electrochemically driven solid-state phase transformations using operando hard X-ray spectro-imaging , 2015, Nature Communications.

[13]  Hsiao-Ying Shadow Huang,et al.  Strain Accommodation during Phase Transformations in Olivine‐Based Cathodes as a Materials Selection Criterion for High‐Power Rechargeable Batteries , 2007 .

[14]  Gerbrand Ceder,et al.  Ab initio study of the migration of small polarons in olivine Li x FePO 4 and their association with lithium ions and vacancies , 2006 .

[15]  M. Islam,et al.  Feeling the strain: enhancing ionic transport in olivine phosphate cathodes for Li- and Na-ion batteries through strain effects , 2016 .

[16]  M. Bazant.  Thermodynamic stability of driven open systems and control of phase separation by electro-autocatalysis. , 2017, Faraday discussions.

[17]  Claire Villevieille,et al.  Combined operando X-ray diffraction–electrochemical impedance spectroscopy detecting solid solution reactions of LiFePO4 in batteries , 2015, Nature Communications.

[18]  Xincun Tang,et al.  Investigation on diffusion behavior of Li+ in LiFePO4 by capacity intermittent titration technique (CITT) , 2009 .

[19]  W. Craig Carter,et al.  Size-Dependent Lithium Miscibility Gap in Nanoscale Li1 − x FePO4 , 2007 .

[20]  J. E. Hilliard,et al.  Free Energy of a Nonuniform System. I. Interfacial Free Energy and Free Energy of a Nonuniform System. III. Nucleation in a Two‐Component Incompressible Fluid , 2013 .

[21]  J. Maier.  Mass transport in the presence of internal defect reactions. Concept of conservative ensembles. III, Trapping effect of dopants on chemical diffusion , 1993 .

[22]  Jun Wang,et al.  In operando tracking phase transformation evolution of lithium iron phosphate with hard X-ray microscopy , 2014, Nature Communications.

[23]  Jian Yu Huang,et al.  In Situ Atomic‐Scale Imaging of Phase Boundary Migration in FePO4 Microparticles During Electrochemical Lithiation , 2013, Advanced materials.

[24]  Palani Balaya,et al.  Ionic and electronic transport in single crystalline LiFePO4 grown by optical floating zone technique , 2008 .

[25]  Fei Meng,et al.  Screw dislocation driven growth of nanomaterials. , 2013, Accounts of chemical research.

[26]  Linda F. Nazar,et al.  Approaching Theoretical Capacity of LiFePO4 at Room Temperature at High Rates , 2001 .

[27]  Sai-Cheong Chung,et al.  Optimized LiFePO4 for Lithium Battery Cathodes , 2001 .

[28]  Daniel A. Cogswell,et al.  Coherency strain and the kinetics of phase separation in LiFePO4 nanoparticles. , 2011, ACS nano.

[29]  S. Marchesini,et al.  Dependence on Crystal Size of the Nanoscale Chemical Phase Distribution and Fracture in LixFePO₄. , 2015, Nano letters.

[30]  Pedro E. Arce,et al.  A Discharge Model for Phase Transformation Electrodes: Formulation, Experimental Validation, and Analysis , 2007 .

[31]  M. Doeff,et al.  TEM Study of Fracturing in Spherical and Plate-like LiFePO4 Particles , 2008 .

[32]  Milo R. Dorr,et al.  Anisotropic Phase Boundary Morphology in Nanoscale Olivine Electrode Particles , 2011 .

[33]  Pier Paolo Prosini,et al.  Determination of the chemical diffusion coefficient of lithium in LiFePO4 , 2002 .

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

[35]  E. Favvas,et al.  What is spinodal decomposition , 2008 .

[36]  Robert W. Balluffi,et al.  Kinetics of Materials: Balluffi/Kinetics , 2005 .

[37]  Q. Shen,et al.  Visualization of anisotropic-isotropic phase transformation dynamics in battery electrode particles , 2016, Nature Communications.

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

[39]  J. Dionne,et al.  Direct visualization of hydrogen absorption dynamics in individual palladium nanoparticles , 2017, Nature Communications.

[40]  Ming Tang,et al.  Model for the Particle Size, Overpotential, and Strain Dependence of Phase Transition Pathways in Storage Electrodes: Application to Nanoscale Olivines , 2009 .

[41]  Guoying Chen,et al.  Mesoscale phase distribution in single particles of LiFePO4 following lithium deintercalation. , 2013, Chemistry of materials : a publication of the American Chemical Society.

[42]  Venkat Srinivasan,et al.  Discharge Model for the Lithium Iron-Phosphate Electrode , 2004 .

[43]  Thomas J. Richardson,et al.  Electron Microscopy Study of the LiFePO4 to FePO4 Phase Transition , 2006 .

[44]  G. Ceder,et al.  Particle-size and morphology dependence of the preferred interface orientation in LiFePO4 nano-particles , 2014 .

[45]  J. E. Hilliard,et al.  Free Energy of a Nonuniform System. I. Interfacial Free Energy , 1958 .

[46]  Alain Mauger,et al.  Study of the Li-insertion/extraction process in LiFePO4/FePO4 , 2009 .

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

[48]  Xia Lu,et al.  Kinetically Controlled Lithium-Staging in Delithiated LiFePO4 Driven by the Fe Center Mediated Interlayer Li–Li Interactions , 2012 .

[49]  Martin Z. Bazant,et al.  Origin and hysteresis of lithium compositional spatiodynamics within battery primary particles , 2016, Science.

[50]  Ruhul Amin,et al.  Phase boundary propagation in large LiFePO4 single crystals on delithiation. , 2012, Journal of the American Chemical Society.

[51]  Dane Morgan,et al.  Li Conductivity in Li x MPO 4 ( M = Mn , Fe , Co , Ni ) Olivine Materials , 2004 .

[52]  Y. Chiang,et al.  Comparative Study of Lithium Transport Kinetics in Olivine Cathodes for Li-ion Batteries† , 2009 .

[53]  Peter Y. Zavalij,et al.  Reactivity, stability and electrochemical behavior of lithium iron phosphates , 2002 .

[54]  J. Xie,et al.  Li-ion diffusion kinetics in LiFePO4 thin film prepared by radio frequency magnetron sputtering , 2009 .

[55]  Yiyang Li,et al.  Current-induced transition from particle-by-particle to concurrent intercalation in phase-separating battery electrodes. , 2014, Nature materials.

[56]  Y. Orikasa,et al.  Transient phase change in two phase reaction between LiFePO4 and FePO4 under battery operation , 2013 .

[57]  Jason Graetz,et al.  Study of antisite defects in hydrothermally prepared LiFePO₄ by in situ X-ray diffraction. , 2011, ACS applied materials & interfaces.

[58]  Hui Zhang,et al.  [100]-Oriented LiFePO4 Nanoflakes toward High Rate Li-Ion Battery Cathode. , 2016, Nano letters.

[59]  Daniel A. Cogswell,et al.  Suppression of phase separation in LiFePO₄ nanoparticles during battery discharge. , 2011, Nano letters.

[60]  Jonathan P. Wright,et al.  Rate-induced solubility and suppression of the first-order phase transition in olivine LiFePO4. , 2014, Nano letters.

[61]  Karena W. Chapman,et al.  Capturing metastable structures during high-rate cycling of LiFePO4 nanoparticle electrodes , 2014, Science.

[62]  Kyle R Fenton,et al.  Intercalation pathway in many-particle LiFePO4 electrode revealed by nanoscale state-of-charge mapping. , 2013, Nano letters.

[63]  J. Maier.  Mass Transport in the Presence of Internal Defect Reactions—Concept of Conservative Ensembles: I, Chemical Diffusion in Pure Compounds , 1993 .

[64]  G. Schütz,et al.  Phase evolution in single-crystalline LiFePO4 followed by in situ scanning X-ray microscopy of a micrometre-sized battery , 2015, Nature Communications.

[65]  Rahul Malik,et al.  A Critical Review of the Li Insertion Mechanisms in LiFePO4 Electrodes , 2013 .