Rate-Dependent, Li-Ion Insertion/Deinsertion Behavior of LiFePO<sub>4</sub> Cathodes in Commercial 18650 LiFePO<sub>4</sub> Cells

Liu, Qi; He, Hao; Li, Zhe‐Fei; Liu, Yadong; Ren, Yang; Lu, Wenquan; Lü, Jun; Stach, Eric A.; Xie, Jian

doi:10.1021/am405150c

Cited by 57 publications

(61 citation statements)

References 40 publications

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“…32,33 The LFP cathode at SoC = 100 % is fully delithiated while the single FePO 4 phase region already starts at SoC = 85...95 % depended on the C-Rate. 34 For the initial pressures of Z2 -Z5, the pressure ranges during cycling are in low stiffness region. In Ref.…”

Section: Resultsmentioning

confidence: 99%

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Pressure Characteristics and Chemical Potentials of Constrained LiFePO₄/C₆Cells

Singer

Kropp

Kuehnemund

et al. 2018

J. Electrochem. Soc.

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Constraining lithium-ion cells increases the cyclic lifetime. However, depending on an expected volume expansion during charge and discharge cycling, defining the optimal constraining pressure range is not straightforward. In this study, we investigate a lithium iron phosphate/graphite pouch cell at four initial constraining pressure levels. As a function of C-Rate, the thermodynamic principle of the non-monotonic pressure curve during full charge and discharge cycles is evaluated. Using the rubber balloon model to calculate the chemical potential of lithium iron phosphate and discussing the relationship between the chemical potential and pressure, we illustrate the pressure curve qualitatively. By applying differential pressure analysis, we evaluate the resulting pressure curves of a single graphite stage. Approaching a fundamental understanding of reduced cycling lifetime of full cells with unknown material composition, we allocate the stages and stage transitions of graphite as well as the phase transition of lithium iron phosphate. Local extreme values in the differential pressure analysis indicate phase and stage transitions. These values can identify critical operating conditions that should be considered for defining the optimum initial constraining pressure range.

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Section: Resultsmentioning

confidence: 99%

“…In Ref. 34, Liu et al evaluate a decreasing volume change V of a LFP unit-cell with increasing C-Rate during discharge. They suggest, that the low overpotential at low C-Rates is due to the dominated two-phase mechanism during lithium insertion/extraction close to a thermodynamically controlled process.…”

Section: Resultsmentioning

confidence: 99%

Pressure Characteristics and Chemical Potentials of Constrained LiFePO₄/C₆Cells

Singer

Kropp

Kuehnemund

et al. 2018

J. Electrochem. Soc.

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“…The sample was heated up to 600°C with a heating rate of 2°C per minute. The diffraction data from the sample was collected every 34 s. The obtained 2D diffraction patterns were calibrated using a standard CeO 2 sample and converted to one-dimensional patterns using Fit2D software 62 .…”

Section: Methodsmentioning

confidence: 99%

Graphene-modified nanostructured vanadium pentoxide hybrids with extraordinary electrochemical performance for Li-ion batteries

et al. 2015

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The long-standing issues of low intrinsic electronic conductivity, slow lithium-ion diffusion and irreversible phase transitions on deep discharge prevent the high specific capacity/energy (443 mAh g À 1 and 1,550 Wh kg À 1 ) vanadium pentoxide from being used as the cathode material in practical battery applications. Here we develop a method to incorporate graphene sheets into vanadium pentoxide nanoribbons via the sol-gel process. The resulting graphene-modified nanostructured vanadium pentoxide hybrids contain only 2 wt. % graphene, yet exhibits extraordinary electrochemical performance: a specific capacity of 438 mAh g À 1 , approaching the theoretical value (443 mAh g À 1 ), a long cyclability and significantly enhanced rate capability. Such performance is the result of the combined effects of the graphene on structural stability, electronic conduction, vanadium redox reaction and lithium-ion diffusion supported by various experimental studies. This method provides a new avenue to create nanostructured metal oxide/graphene materials for advanced battery applications.

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“…This phenomenon confirms our previous finding that the lithium intercalation/deintercalation behavior is strongly depends on the charge/discharge rate. 33 Further, it suggests that the solid solution mechanism trends to occur at high current rate while the two phase reaction mechanism prefers to occur at lower current rate. …”

Section: Resultsmentioning

confidence: 98%

“…Many studies on the 18650 battery, documented in the literatures, focused on its electrochemical properties. [30][31] Little work deals with the internal structure changes of 18650 battery, since the big diameter and stainless steel shell of the battery cause a large difficulty in the characterization by conventional techniques.To reveal mechanistic and structural information during the lithiation/delithiation processes under non-equilibrium states, in situ HES-XRD were employed to determine simultaneously the changes in both the cathode and anode in our previous paper, [32][33] and this technique is proved to be effective for the study of battery. The only drawback in the previous work is that the time for every exposure is too long and only the average structure information during the exposure time is observed.…”

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confidence: 99%

Dynamic Lithium Intercalation/Deintercalation in 18650 Lithium Ion Battery by Time-Resolved High Energy Synchrotron X-Ray Diffraction

Liu

Abouimrane

et al. 2015

J. Electrochem. Soc.

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A time-resolved in situ high energy synchrotron X-ray diffraction (HESXRD) technique is employed to study the lithiation/delithiation of cathode/anode in a commercial 18650 battery under real working condition (current rate is 4 C). The phases and their changes in both the cathode and anode are identified simultaneously. For the anode component, during the charge process, as well as the Li x C 6 phase, a lithium-rich phase close to LiC 6 phase and a series of intermediate phases between the Li 0.5 C 6 and LiC 6 phases are observed. A distinct lithium intercalation/deintercalation mechanism is proposed for the cathode. The transforms of LiFePO 4 into the FePO 4 consists three periods with different components of phases, i.e., LiFePO 4 + lithium-deficient solid solution phases (period I), FePO 4 + LiFePO 4 phases (period II), and FePO 4 + lithium-rich solid solution phases (period III). The changes in both the andode and cathode during the discharge process are just inversed to those occurrs during the charge process. The present work indicates that dynamic lithiation/delithaition process under real working condition is different from those at the thermodynamic state, and the in situ HESXRD is one of the most promising technique to monitor such kind of dynamic lithium behavior. In the past twenty years, lithium ion battery experienced a fast development due to its large energy density, high voltage and excellent cycle performance.1-2 While various Li ion battery systems are commercialized, the understanding of the lithiation/delithiation process mechanism occurred in electrode material is recognized to be crucial in developing new batteries and thus is attracting more and more attentions. To study the structure changes in electrode materials during lithium intercalation/deintercalation, various of in situ techniques, such as X-ray diffraction (XRD), 3-5 X-ray absorption, 6-7 Raman spectroscopy, 8 nuclear magnetic resonance [9][10] and transmission electron microscopy, 11 have been employed. However, these techniques possess a weak ability of penetration and can be only utilized in the characterizations of some special designed batteries.12-14 Besides, most of these techniques are based on stepscan mode, by which as long as several minutes are usually required to collect the structure information. Therefore, a small current density has to be applied in order to monitor effectively the structure change in electrode materials. The thus-obtained mechanisms disclosed only the lithiation/delithiation process under thermodynamic equilibrium status. [15][16] In addition, in the graphite/LiFePO 4 battery system, while the intercalation/deintercalation mechanism on the anode (graphite/Li x C 6 ) has been well established, that on the cathode (FePO 4 /LiFePO 4 ) is still under debate. [17][18][19] It was usually reported in the literature that the lithiation/delithiation of FePO 4 /LiFePO 4 involved either a two-phase reaction [16][17] or a solidsolution reaction. [20][21][22] However, notwithstanding the differences in thes...

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Rate-Dependent, Li-Ion Insertion/Deinsertion Behavior of LiFePO₄ Cathodes in Commercial 18650 LiFePO₄ Cells

Cited by 57 publications

References 40 publications

Pressure Characteristics and Chemical Potentials of Constrained LiFePO₄/C₆Cells

Pressure Characteristics and Chemical Potentials of Constrained LiFePO₄/C₆Cells

Graphene-modified nanostructured vanadium pentoxide hybrids with extraordinary electrochemical performance for Li-ion batteries

Dynamic Lithium Intercalation/Deintercalation in 18650 Lithium Ion Battery by Time-Resolved High Energy Synchrotron X-Ray Diffraction

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Rate-Dependent, Li-Ion Insertion/Deinsertion Behavior of LiFePO4 Cathodes in Commercial 18650 LiFePO4 Cells

Cited by 57 publications

References 40 publications

Pressure Characteristics and Chemical Potentials of Constrained LiFePO4/C6Cells

Pressure Characteristics and Chemical Potentials of Constrained LiFePO4/C6Cells

Graphene-modified nanostructured vanadium pentoxide hybrids with extraordinary electrochemical performance for Li-ion batteries

Dynamic Lithium Intercalation/Deintercalation in 18650 Lithium Ion Battery by Time-Resolved High Energy Synchrotron X-Ray Diffraction

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Product

Resources

About

Rate-Dependent, Li-Ion Insertion/Deinsertion Behavior of LiFePO₄ Cathodes in Commercial 18650 LiFePO₄ Cells

Pressure Characteristics and Chemical Potentials of Constrained LiFePO₄/C₆Cells

Pressure Characteristics and Chemical Potentials of Constrained LiFePO₄/C₆Cells