Research Update: Retardation and acceleration of phase separation evaluated from observation of imbalance between structure and valence in LiFePO4/FePO4 electrode

Tokuda, Keiichi; Kawaguchi, Tomoya; Fukuda, Katsutoshi; Ichitsubo, Tetsu; Matsubara, Eiichiro

doi:10.1063/1.4886555

Cited by 6 publications

(4 citation statements)

References 33 publications

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“…It is obvious that the MP unit cell experiences a volume expansion of about 6% after the insertion of 1 mole of Li. This value is close to that of FePO 4 after 1 mole Li insertion, that is, in the range of 5–8%. , …”

Section: Resultssupporting

confidence: 81%

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Density Functional Theory Investigation of Mixed Transition Metals in Olivine and Tavorite Cathode Materials for Li-Ion Batteries

Alfaruqi

Kim

Park

et al. 2020

ACS Appl. Mater. Interfaces

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Lithium-ion batteries (LIBs) are widely used in various electronic devices and have garnered a huge amount of attention. In addition, evaluation of the intrinsic properties of LIB cathode materials is of considerable interest for practical applications. Therefore, through first-principles calculations based on the density functional theory, we investigated the structural, electronic, electrochemical, and kinetic properties of mixed transition metals, that is, Ni-substituted LiMnPO4 (LMP) and LiMnPO4F (LMPF) cathode materials, that is, LiMn0.5Ni0.5PO4 (LMNP) and LiMn0.5Ni0.5PO4F (LMNPF), respectively, which have not been extensively studied. We also evaluated their delithiated phases, that is, Mn0.5Ni0.5PO4 (MNP) and Mn0.5Ni0.5PO4F (MNPF). Our calculations suggest that Ni substitution significantly affected the structural and electrochemical properties. After Li insertion, the MNPF unit-cell volume increased by about 8%, lower than that of pristine MnPO4F. The Li intercalation voltage also increased in LMNP (4.27 V) and LMNPF (5.23 V). In addition, the migration barrier was calculated to be 0.4 eV for LMNPF, lower than that of LMPF. This study may provide insights for developing LMNP and LMNPF cathode materials in LIB applications.

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Section: Resultssupporting

confidence: 81%

“…This value is close to that of FePO 4 after 1 mole Li insertion, that is, in the range of 5−8%. 54,55 Figure 1c,d shows the relaxed structures of LMNP and Mn 0. The reduced unit cell in LMP and MnPO 4 after the Ni substitution can be attributed to the smaller ionic radius of Ni 2+ (0.83 Å), as predicted from Vegard's law.…”

Section: Resultsmentioning

confidence: 99%

Density Functional Theory Investigation of Mixed Transition Metals in Olivine and Tavorite Cathode Materials for Li-Ion Batteries

Alfaruqi

Kim

Park

et al. 2020

ACS Appl. Mater. Interfaces

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“…By using the in situ XRD measurement and the Rietveld refinement, Wang et al investigated the delayed phase transition of submicron LiFePO 4 particles at the rate of 0.1 C, which was possibly originated from the nucleation and growth mechanisms of a new phase. By combining in situ XRD and the X-ray absorption near edge structure, Tokuda et al observed that the phase transition of the LiFePO 4 particle with an equivalent diameter of 177 nm was later than the valence change of Fe ions at the rate of 1 C, owing to the coherent strain caused by the lattice mismatch between two phases. By using in situ XRD and Gaussian curve fitting, Siddique et al revealed that the phase transformation was delayed more seriously at a higher rate which might come from the insufficient Li-ion supply caused by the obstacle of diffusion through the complicated porous network or limited local electronic conductivity.…”

Section: Results and Discussionmentioning

confidence: 99%

Size-Dependent Memory Effect of the LiFePO₄ Electrode in Li-Ion Batteries

Guo

Song

et al. 2018

ACS Appl. Mater. Interfaces

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In Li-ion batteries, the phase transition usually determines the electrochemical kinetics of some two-phase electrode materials, and it can be adopted to excellently interpret the memory effect of Li-ion batteries, therefore the size dependence of phase transition was expected to affect the memory effect significantly. In this work, we investigated the memory effect and phase transition of olivine LiFePO4 in Li-ion batteries. Through electrochemical measurements, we found that the memory effect of LiFePO4 was dependent on the particle size, especially after a long-time relaxation. By using the in situ X-ray diffraction, we found that the phase transition of nano-LiFePO4 was ahead of the charging and discharging processes, while it took place concurrently or later for micro-LiFePO4, which might be attributed to the high-specific two-phase boundary of nano-LiFePO4. Furthermore, the phase-transition diagram was adopted to interpret the size-dependent memory effect schematically. Notably, it is the first time to report the phase transition ahead of (dis)charging for nano-LiFePO4, which is significant to understand the phase transition of two-phase electrode materials, as well as the relevant phenomena, such as the memory effect.

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“…The P-DAFS measurements were conducted at beamline BL28XU, 29,30 SPring-8, Japan. We used a Si(111) channel-cut monochromator with a 3 mm gap in combination with two pairs of horizontal and vertical Rh-coated mirrors upstream and downstream of the monochromator to eliminate highorder harmonics.…”

Section: P-dafs Measurements and Analysismentioning

confidence: 99%

Roles of transition metals interchanging with lithium in electrode materials

Kawaguchi

Fukuda

Tokuda

et al. 2015

Phys. Chem. Chem. Phys.

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Roles of antisite transition metals interchanging with Li atoms in electrode materials of Li transition-metal complex oxides were clarified using a newly developed direct labeling method, termed powder diffraction anomalous fine structure (P-DAFS) near the Ni K-edge. We site-selectively investigated the valence states and local structures of Ni in Li0.89Ni1.11O2, where Ni atoms occupy mainly the NiO2 host-layer sites and partially the interlayer Li sites in-between the host layers, during electrochemical Li insertion/extraction in a lithium-ion battery (LIB). The site-selective X-ray near edge structure evaluated via the P-DAFS method revealed that the interlayer Ni atoms exhibited much lower electrochemical activity as compared to those at the host-layer site. Furthermore, the present analyses of site-selective extended X-ray absorption fine structure performed using the P-DAFS method indicates local structural changes around the residual Ni atoms at the interlayer space during the initial charge; it tends to gather to form rock-salt NiO-like domains around the interlayer Ni. The presence of the NiO-like domains in the interlayer space locally diminishes the interlayer distance and would yield strain energy because of the lattice mismatch, which retards the subsequent Li insertion both thermodynamically and kinetically. Such restrictions on the Li insertion inevitably make the NiO-like domains electrochemically inactive, resulting in an appreciable irreversible capacity after the initial charge but an achievement of robust linkage of neighboring NiO2 layers that tend to be dissociated without the Li occupation. The P-DAFS characterization of antisite transition metals interchanging with Li atoms complements the understanding of the detailed charge-compensation and degradation mechanisms in the electrode materials.

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Research Update: Retardation and acceleration of phase separation evaluated from observation of imbalance between structure and valence in LiFePO4/FePO4 electrode

Cited by 6 publications

References 33 publications

Density Functional Theory Investigation of Mixed Transition Metals in Olivine and Tavorite Cathode Materials for Li-Ion Batteries

Density Functional Theory Investigation of Mixed Transition Metals in Olivine and Tavorite Cathode Materials for Li-Ion Batteries

Size-Dependent Memory Effect of the LiFePO₄ Electrode in Li-Ion Batteries

Roles of transition metals interchanging with lithium in electrode materials

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Research Update: Retardation and acceleration of phase separation evaluated from observation of imbalance between structure and valence in LiFePO4/FePO4 electrode

Cited by 6 publications

References 33 publications

Density Functional Theory Investigation of Mixed Transition Metals in Olivine and Tavorite Cathode Materials for Li-Ion Batteries

Density Functional Theory Investigation of Mixed Transition Metals in Olivine and Tavorite Cathode Materials for Li-Ion Batteries

Size-Dependent Memory Effect of the LiFePO4 Electrode in Li-Ion Batteries

Roles of transition metals interchanging with lithium in electrode materials

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Product

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Size-Dependent Memory Effect of the LiFePO₄ Electrode in Li-Ion Batteries