Evaluation of real performance of LiFePO4 by using single particle technique

Munakata, Hirokazu; Takemura, Bunpei; Saito, Takamitsu; Kanamura, Kiyoshi

doi:10.1016/j.jpowsour.2012.06.037

Cited by 82 publications

(85 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The dew point of the room was maintained below 223 K. The electrochemical cell was a two-electrode system with a Li metal counter electrode. [17][18][19][20][21] The electrolyte was a mixed solvent of propylene carbonate and ethylene carbonate (1:1 by volume) containing 1 mol dm ¹3 LiPF 6 (Kishida Chemical Co., Ltd.). Constant current charge and discharge measurements were conducted by using an electrochemical analyzer (SP-150, BioLogic) with a low-current probe.…”

Section: Methodsmentioning

confidence: 99%

“…15,16 However, we have used the single particle measurement technique to investigate the intrinsic properties of the active materials. [17][18][19][20][21] In this technique, a microprobe is placed in contact with an active material particle at the micrometer scale. Dokko et al reported that commercial LiCoO 2 particles have been evaluated by this technique and have excellent rate characteristics.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Intrinsic Electrochemical Characteristics in the Individual Needle-like LiCoO<sub>2</sub> Crystals Synthesized by Flux Growth

et al. 2017

Self Cite

View full text Add to dashboard Cite

The intrinsic electrochemical characteristics of needle-like LiCoO 2 crystals with a hexagonal cylindrical shape were studied by the single particle measurement technique. The needle-like LiCoO 2 crystals were synthesized by the flux growth method. Single-particle Raman spectroscopy and galvanostatic charge-discharge tests at different electrical contact points in one needle-like LiCoO 2 crystal revealed that the crystal has homogeneous intercalation/ deintercalation characteristics throughout the long axis. This suggests that the electron conductivity is high on a 100 µm scale along that axis and that lithium ions are efficiently transferred from the electrolyte to the layer structure of the crystal. The charge rate characteristics of the needle-like LiCoO 2 crystals were also evaluated and compared to those of powdered LiCoO 2 . The polarization curve analysis indicates that the needle-like LiCoO 2 particles had almost same exchange current density, i 0 , as powdered LiCoO 2 , which has a much smaller volume. These excellent electrochemical characteristics are considered to be due to the orientation of the {104} crystal face on the crystal sides, which is the preferential face for lithium ion transfer, and the larger effective surface area of the particles.

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Intrinsic Electrochemical Characteristics in the Individual Needle-like LiCoO<sub>2</sub> Crystals Synthesized by Flux Growth

et al. 2017

Self Cite

View full text Add to dashboard Cite

show abstract

“…The model ignores solid-state diffusion effects inside LFP units based on recent observations of ultrafast chemical 55 and electrochemical 7,56 delithiation/lithiation of LFP units that counter the common belief that intra-particle mass transport is a limiting factor for Li + insertion/de-insertion into/from the units. With this view, the geometrical description of LFP units becomes irrelevant as far as the diffusion length is concerned.…”

Section: Model Developmentmentioning

confidence: 99%

“…Previous modeling and experimental analyses of commercial LFP electrodes similar to that done here considered diffusion to be the determining factor at the end of charge/discharge; 27 Ultrafast charge/discharge of optimized LFP electrodes has also confirmed fast Li mobility in the bulk of LFP. 7,56 In order to assess a diffusion-limited scenario, we extended the mesoscopic model to account for the intra-unit diffusion along with a unimodal log-normal distribution for resistance. Although not shown here, it turns out again that a very small diffusion coefficient on the order of 10 −19 m 2 s −1 (assuming a spherical unit with 80 nm radius) is required in order for solid-state transport limitations to become significant.…”

Section: E3046mentioning

confidence: 99%

Mesoscopic Modeling of a LiFePO₄Electrode: Experimental Validation under Continuous and Intermittent Operating Conditions

Farkhondeh¹,

Pritzker²,

Fowler³

2017

J. Electrochem. Soc.

View full text Add to dashboard Cite

The previously presented mesoscopic model [Phys. Chem. Chem. Phys., 16, 22555, (2014)] for battery electrodes consisting of phase-change insertion materials is incorporated into porous-electrode theory and validated by comparing the simulation results with experimental data from continuous and intermittent galvanostatic discharge of a LiFePO 4 electrode under various operating conditions. The model features mesoscopic LiFePO 4 units that undergo non-equilibrium lithiation/delithiation and fast solid-state diffusion. Good agreement with the experimental data supports the validity of this model. GITT analysis suggests that the slow evolution of the electrode polarization during each pulse and the subsequent relaxation period is due to Li transport between LiFePO 4 units rather than diffusion within the units. Galvanostatic pulse techniques commonly used to determine diffusivities of inserted species in solid-solution systems may also be used to estimate the equilibrium potential of individual mesoscopic units for which no actual measurement has been reported to date. Further analysis of the GITT experiments suggests an alternative pathway for the intermittent charge/discharge of LFP electrodes. Depending on the overall depth-of-discharge/charge of the electrode, relaxation time and the incremental depth-of-discharge/charge of each pulse, the solid-solution capacity available in the Li-rich/Li-poor end-member may be able to accommodate Li insertion/extraction entirely without phase transformation during each pulse. LiFePO 4 (LFP) has proved promising as a high-power active material for the positive electrodes in Li-ion batteries. Its outstanding performance has been subject of intensive research since its discovery in 1997.1 LFP undergoes a phase separation between the Li-poor Li ε FePO 4 and Li-rich Li 1−ε FePO 4 phases (ε and ε 1) during lithiation/delithiation, which is manifested by its equilibrium potential remaining virtually constant over a range of intermediate compositions.1,2 In spite of this phase separation, electrodes consisting of either nano-scale LFP particles 3,4 and/or particles coated with ionically/electronically conducting materials 5-8 exhibit a high rate capability and long cycle life. However, the seeming contradiction between the biphasic nature of the material and its high performance is not reflected in conventional models 9-27 describing the movement of phase boundaries and associated mechanical effects inside the particles during lithiation/delithiation.The advent of high resolution phase mapping tools has lead to more accurate characterization of the charge/discharge dynamics of LFP electrodes. [28][29][30][31][32][33][34][35][36][37][38][39] Maier et al. 32 tracked the phase boundary propagation in a large millimeter-scale LFP single crystal during chemical delithiation and observed the formation of a large amount of microstructural defects such as pores and cracks. Cabana et al. 33 used soft X-ray ptychographic microscopy (with a spatial resolution of ∼5 nm) and X-ray absorption spec...

show abstract

“…A microelectrode-particle contact method has been used to evaluate the electrochemical processes at single active cathode electrode particles [10][11][12] , but the process was either measured for the whole grain (relatively large secondary particle) or, in special circumstances, information was obtained at a resolution of several microns (or larger) by using in situ optical or Raman visualization techniques 12 . At higher resolution, atomic force microscopy (AFM) and scanning tunneling microscopy (STM) have been used to visualize dynamic structural changes during charge/discharge, for instance, solid electrolyte interface formation 13,14 .…”

mentioning

confidence: 99%

Nanoscale visualization of redox activity at lithium-ion battery cathodes

et al. 2014

Self Cite

View full text Add to dashboard Cite

Intercalation and deintercalation of lithium ions at electrode surfaces are central to the operation of lithium-ion batteries. Yet, on the most important composite cathode surfaces, this is a rather complex process involving spatially heterogeneous reactions that have proved difficult to resolve with existing techniques. Here we report a scanning electrochemical cell microscope based approach to define a mobile electrochemical cell that is used to quantitatively visualize electrochemical phenomena at the battery cathode material LiFePO 4 , with resolution of B100 nm. The technique measures electrode topography and different electrochemical properties simultaneously, and the information can be combined with complementary microscopic techniques to reveal new perspectives on structure and activity. These electrodes exhibit highly spatially heterogeneous electrochemistry at the nanoscale, both within secondary particles and at individual primary nanoparticles, which is highly dependent on the local structure and composition.

show abstract

Evaluation of real performance of LiFePO4 by using single particle technique

Cited by 82 publications

References 30 publications

Intrinsic Electrochemical Characteristics in the Individual Needle-like LiCoO<sub>2</sub> Crystals Synthesized by Flux Growth

Intrinsic Electrochemical Characteristics in the Individual Needle-like LiCoO<sub>2</sub> Crystals Synthesized by Flux Growth

Mesoscopic Modeling of a LiFePO₄Electrode: Experimental Validation under Continuous and Intermittent Operating Conditions

Nanoscale visualization of redox activity at lithium-ion battery cathodes

Contact Info

Product

Resources

About

Evaluation of real performance of LiFePO4 by using single particle technique

Cited by 82 publications

References 30 publications

Intrinsic Electrochemical Characteristics in the Individual Needle-like LiCoO<sub>2</sub> Crystals Synthesized by Flux Growth

Intrinsic Electrochemical Characteristics in the Individual Needle-like LiCoO<sub>2</sub> Crystals Synthesized by Flux Growth

Mesoscopic Modeling of a LiFePO4Electrode: Experimental Validation under Continuous and Intermittent Operating Conditions

Nanoscale visualization of redox activity at lithium-ion battery cathodes

Contact Info

Product

Resources

About

Mesoscopic Modeling of a LiFePO₄Electrode: Experimental Validation under Continuous and Intermittent Operating Conditions