What can we learn about battery materials from their magnetic properties?

Chernova, Natasha A.; Nolis, Gene M.; Omenya, Fredrick; Zhou, Hui; Li, Zheng; Whittingham, M. Stanley

doi:10.1039/c1jm00024a

Cited by 109 publications

(114 citation statements)

References 88 publications

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“…Closer observation reveals that the remanent magnetization decreases with increasing Al content, which also reflects a decrease of Ni ions in the lithium layer since such ions facilitate the formation of the ferrimagnetic clusters, which lead to the increase of the magnetic hysteresis. 19 Electrochemical performance.-All the Li 1.2 Ni 0.16 Mn 0.56 Co 0.08−y Al y O 2 electrodes show a reversible capacity above 200 mAh/g when charged to 4.8 V and the capacity decreases with increasing Al substitution, as indicated in Fig. 5a.…”

Section: Resultsmentioning

confidence: 97%

Stability and Rate Capability of Al Substituted Lithium-Rich High-Manganese Content Oxide Materials for Li-Ion Batteries

Chernova

Feng

et al. 2011

J. Electrochem. Soc.

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The structures, electrochemical properties and thermal stability of Al-substituted lithium-excess oxides, Li 1.2 Ni 0.16 Mn 0.56 Co 0.08−y Al y O 2 (y = 0, 0.024, 0.048, 0.08), are reported, and compared to the stoichiometric compounds, LiNi z Mn z Co 1−2z O 2 . A solid solution was found up to at least y = 0.06. Aluminum substitution improves the poor thermal stability while preserving the high energy density of lithium-excess oxides. However, these high manganese compositions are inferior to the lithium stoichiometric materials, LiNi z Mn z Co 1−2z O 2 (z = 0.333, 0.4), in terms of both power and thermal stability.The energy density of batteries has increased more than fivefold over the last century, largely attributed to the advent of lithium ion battery technology. 1-3 This has resulted in lithium batteries today dominating the portable electronics market. However, large-scale applications such as needed for electric vehicles or grid load-leveling requires higher energy densities, both volumetric and gravimetric, as well as higher safety and lower costs. 4 Materials with capacities exceeding 200 Ah/kg at potentials around 3.5 to 4 volts are realistic targets that with denser anodes could double the energy density of today's lithium batteries. The layered oxides LiMO 2 or Li 1+y M 1−y O 2 are one class of material that might meet this target.The layered mixed transition metal oxides LiNi z Mn z Co 1−2z O 2 (0.333 ≤ z ≤ 0.5, abbreviated as NMC; z = 0.5, 0.4 and 0.333, abbreviated as 550, 442 and 333, respectively) are beginning to replace the successfully commercialized LiCoO 2 due to their lower cost, more environmental friendliness and higher thermal stability. 5, 6 Our previous comparative study of LiNi z Mn z Co 1−2z O 2 , showed that the z = 0.4 composition has the best electrochemical performance with a theoretical capacity of around 200 mAh/g when charged up to 4.4 V. 7-9 Charging to a higher voltage leads to increased capacity fading. The lithium-excess layered oxides have drawn extensive attention, 10-12 as they can in principle exceed 200 Ah/kg. Our goal is to improve the thermal stability through Al substitution and the capacity through the excess lithium. [13][14][15] Here we report a systematic study of a series of compounds of composition Li 1.2 Ni 0.16 Mn 0.56 Co 0.08−y Al y O 2 , where y = 0, 0.024, 0.048, and 0.08. This composition can be viewed as a 1:1 combination of Li 2 MnO 3 and LiNi 0.4 Mn 0.4 Co 0.2 O 2 ; the latter is we believe the optimum NMC composition. We compare the results obtained with the structure, energy density, power capability and thermal stability of NMC, in order to provide a deeper understanding of the effects of lithium excess and Al substitution in layered oxides. ExperimentalThe Li 1.2 Ni 0.16 Mn 0.56 Co 0.08−y Al y O 2 , (0 ≤ y ≤ 0.08) and NMC were synthesized by the co-precipitation method followed by solidstate reaction. The synthesis of NMC was described in the previous publications. 7-9 For Li 1.2 Ni 0.16 Mn 0.56 Co 0.08−y Al y O 2 , LiOH · H 2 O (Alfa Aesar), N...

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Section: Resultsmentioning

confidence: 97%

Stability and Rate Capability of Al Substituted Lithium-Rich High-Manganese Content Oxide Materials for Li-Ion Batteries

Chernova

Feng

et al. 2011

J. Electrochem. Soc.

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“…In our own previous studies on Li x CoO 2 we used a combination of this "magnetic tool" and diffraction techniques to identify Co 3 O 4 and LiCo 2 O 4 as products of thermal decomposition [22]. Subsequently we extended the approach of combined electron diffraction and magnetic measurements to the binary system LiNi 1Àx Mn x O 2 [18] and finally to the ternary LiNi 1/3 Mn 1/3 Co 1/3 O 2 compound. Although the magnetic properties of the ternary LiNi 1/ 3 Mn 1/3 Co 1/3 O 2 material has been described in several studies [15,16,23], to our knowledge, no reports can be found where the magnetic properties are correlated to electron diffraction studies in an attempt to understand the cation ordering in this material.…”

Section: Introductionmentioning

confidence: 98%

“…Information on oxidation states of transition metal ions [15], cation ordering, [16,17] stoichiometry of lithium ions [18] can be deduced from the magnetic data of these oxides. For example, magnetic measurements of LiCoO 2 were used to characterize changes in the oxidation state of cobalt ions upon lithium extraction [19e21].…”

Section: Introductionmentioning

confidence: 99%

Microstructural investigation of LixNi1/3Mn1/3Co1/3O2 (x ≤ 1) and its aged products via magnetic and diffraction study

Mohanty

Gabrisch

2012

Journal of Power Sources

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“…[8] However, the magnitude of the effective magnetic moment (µ ef f ) obtained from the Curie-Weiss law fitting was inconsistent and spread in the range of µ ef f ∼4.7-5.5 µ B , which has been interpreted that Fe 2+ must be in the high-spin state (HS) as t 4 2g e 2 g of S=2 with a spin-only value of µ ef f = 4.9µ B , and the inconsistent moment above 4.9 µ B has often been described by incomplete orbital-quenching, i.e., the theoretically calculated value from the Lande g-factor with J=L+S (S=2, L=2) without orbital quenching should be µ ef f =6.7µ B . [9,10] Considering a typical iron ion in the crystal field composed of oxygen ligands with high electronegativity, the HS choice of d 6 implies an unexpectedly small crystal field splitting between e g − t 2g , unless the influence of the nearby PO 3− 4 phosphate groups are included. In addition, within the explanation of in-complete orbital-quenching, the actual mechanism that triggers the different degree of orbital-quenching remains unknown.…”

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confidence: 99%

Finite-size effect of antiferromagnetic transition and electronic structure in LiFePO4

Shu

Chou

2012

Phys. Rev. B

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The finite-size effect on the antiferromagnetic (AF) transition and electronic configuration of iron has been observed in LiFePO4. Determination of the scaling behavior of the AF transition temperature (TN ) vs. the particle size dimension (L) in the critical regime, 1 −∼ L −1 , reveals that the activation nature of the AF ordering strongly depends on the surface energy. In addition, the effective magnetic moment that reflects the electronic configuration of iron in LiFePO4 is found sensitive to the particle size. An alternative structural view based on the polyatomic ion groups of PO 3− 4 is proposed. LiFePO 4 has been considered as an ideal cathode electrode material with a workable redox potential of 3.45 V and a high theoretical capacity of 170 mAh/g.[1] LiFePO 4 is a band insulator in bulk crystal form in agreement with the calculated large band gap,[2] however, the fast electron/ion charge/discharge process has been shown to be possible only when the particle size is reduced to below ∼100 nm.[3] While significant progress has been made to demonstrate the impact of nanoscaling on defect chemistry, electrochemical behavior, electron-ion conductivity, lithium ion diffusion, and the charge/discharge rate in general,[4-6] the fundamental question of "why nano-scaling matters?" remains. Generally, there have been two major approaches to interpret the property improvement for LiFePO 4 using nano-scaling induced electron/ion transport: the first is called the "domino-cascade" model, which describes a fast anisotropic lithium insertion/extraction action coupled to the LiFePO 4 -FePO 4 interface movement through an electron polaronic hopping mechanism in nano-crystallites, [5] and the second focuses on the surface effect with carbon coating and miscibility gap size reduction as a result of nano-scaling. [4,7] Conventionally, the iron ion has been viewed as Fe 2+with oxygen ligands to form the octahedral crystal electric field (CEF) of e g -t 2g splitting.[8] However, the magnitude of the effective magnetic moment (µ ef f ) obtained from the Curie-Weiss law fitting was inconsistent and spread in the range of µ ef f ∼4.7-5.5 µ B , which has been interpreted that Fe 2+ must be in the high-spin state (HS) as t 4 2g e 2 g of S=2 with a spin-only value of µ ef f = 4.9µ B , and the inconsistent moment above 4.9 µ B has often been described by incomplete orbital-quenching, i.e., the theoretically calculated value from the Lande g-factor with J=L+S (S=2, L=2) without orbital quenching should be µ ef f =6.7µ B .[9, 10] Considering a typical iron ion in the crystal field composed of oxygen ligands with high electronegativity, the HS choice of d 6 implies an unexpectedly small crystal field splitting between e g − t 2g , unless the influence of the nearby PO 3− 4 phosphate groups are included. In addition, within the explanation of in-

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What can we learn about battery materials from their magnetic properties?

Cited by 109 publications

References 88 publications

Stability and Rate Capability of Al Substituted Lithium-Rich High-Manganese Content Oxide Materials for Li-Ion Batteries

Stability and Rate Capability of Al Substituted Lithium-Rich High-Manganese Content Oxide Materials for Li-Ion Batteries

Microstructural investigation of LixNi1/3Mn1/3Co1/3O2 (x ≤ 1) and its aged products via magnetic and diffraction study

Finite-size effect of antiferromagnetic transition and electronic structure in LiFePO4

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