Revealing the coupled cation interactions behind the electrochemical profile of LixNi0.5Mn1.5O4

Lee, Eunseok; Persson, Kristin A.

doi:10.1039/c2ee03068c

Cited by 75 publications

(142 citation statements)

References 38 publications

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“…As a result, extended solid-solution behavior in the Li-doped sample can result from the large Ni/Mn disordering. This observation agrees very well with recent calculation results, 10,11 which indicate that a perfectly cation-ordered spinel with a space group of P4 3 32 resists the solid-solution phase transition behavior because the Ni/Mn ordering is incompatible with the ordering of Li + and vacancies during delithiation, whereas the introduction of Ni/Mn disordering into the spinel structure results in a gradual increase in stability for a solid-solution reaction, especially in a lithium-rich phase such as LNMO. The degree of Ni/Mn disordering strongly increases the solid-solution reaction during delithiation.…”

Section: Resultssupporting

confidence: 82%

“…Recent calculations have shown that the solid-solution phase transformation in the spinel results from the disordering of Ni/Mn, not from Mn 3+ ions. 10,11 However, there are no experimental data supporting this calculation because controlling the Ni/Mn disordering to optimize electrochemical performance without the presence of Mn 3+ ions has not been feasible. As a result, understanding the effect of disordering or the effect of Mn 3+ ions on electrochemical properties is experimentally very important because the decoupling of the Ni/Mn disordering from the Mn 3+ ions can help in optimizing the electrochemical performance of the LNMO spinel.…”

Section: Introductionmentioning

confidence: 95%

“…8 Among these factors, the structure of the spinel has a critical influence on its electrochemical performance. [9][10][11] The LNMO structure is dictated by the ordering of Ni and Mn at two octahedral sites, which results in two spinel forms: disordered and ordered. The Ni and Mn in the ordered spinel are well ordered in two distinct octahedral sites, 4b sites for Ni and 12d sites for Mn, whereas the Ni and Mn in the disordered spinel are randomly distributed in 16d octahedral sites.…”

Section: Introductionmentioning

confidence: 99%

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High electrochemical performance of high-voltage LiNi0.5Mn1.5O4 by decoupling the Ni/Mn disordering from the presence of Mn3+ ions

Lee¹,

Kim²,

Kang³

2015

NPG Asia Mater

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Electrochemical activity in high-voltage spinel LiNi 0.5 Mn 1.5 O 4 (LNMO) is strongly affected by the disordering of Ni/Mn and the presence of Mn 3+ ions. However, understanding the effect of the Ni/Mn disordering or the presence of Mn 3+ ions on electrochemical properties is not trivial because disordering is typically coupled with the presence of Mn 3+ ions. Here, we demonstrate for the first time that the doping of Li instead of Ni increases Ni/Mn disordering, which is decoupled from the presence of Mn 3+ ions. The resultant material has a particle size of~1-2 μm and can achieve 120 mAh g − 1 at 10 C for 50 cycles and further deliver about 60 mAh g − 1 even at a rate of~60 C (1 min discharge). Superior electrochemical performance is achieved by increased solid-solution phase transition behavior, which is caused by increased Ni/Mn disordering during delithiation. By decoupling, we find that the electrochemical properties in LNMO strongly depend on the phase transformation behavior and that the Ni/Mn disordering, rather than Mn 3+ ions, affects the phase transformation by increasing the solid-solution reaction. The fundamental understanding gained from this work could be applied to the development of other phase-separating compounds to improve their electrochemical performance. INTRODUCTIONFor a lithium-ion battery, a high energy density is an essential requirement for novel applications such as plug-in hybrid electric vehicles and electric vehicles. Increasing the redox potential of cathode materials is an effective way to achieve high energy density in the cell. For this purpose, high-voltage spinel LiNi 0.5 Mn 1.5 O 4 is a promising cathode material for LIBs 1-3 because it has a high redox potential of about 4.7 V, which makes its energy density (650 W h kg − 1 ) 20% higher than that of the conventional LiCoO 2 . However, the electrochemical properties of LNMO spinel depend on several factors, such as its structure, 3,4 the quantity of Mn 3+ ions, 5,6 the particle size 2,7 and the morphology of particles. 8 Among these factors, the structure of the spinel has a critical influence on its electrochemical performance. 9-11 The LNMO structure is dictated by the ordering of Ni and Mn at two octahedral sites, which results in two spinel forms: disordered and ordered. The Ni and Mn in the ordered spinel are well ordered in two distinct octahedral sites, 4b sites for Ni and 12d sites for Mn, whereas the Ni and Mn in the disordered spinel are randomly distributed in 16d octahedral sites. 1,12 In the ordered spinel, the ordering of Ni/Mn exists without Mn 3+ ions because a second annealing process at o700°C simultaneously leads to the ordering of Ni/Mn on two distinct octahedral sites and the oxidation of Mn 3+ ions into Mn 4+ ions. However, the disordered spinel shows both the disordering of Ni/Mn and the presence of Mn 3+ ions. The correlation

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Section: Resultssupporting

confidence: 82%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

High electrochemical performance of high-voltage LiNi0.5Mn1.5O4 by decoupling the Ni/Mn disordering from the presence of Mn3+ ions

Lee¹,

Kim²,

Kang³

2015

NPG Asia Mater

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“…30 The high voltage spinel Li X Mn 1.5 Ni 0.5 O 4 also undergoes at least one firstorder phase transformation; the phase-behavior of this compound is sensitive to Ni/Mn ordering on the transition metal cation sublattice, which in turn depends on the thermal history of the material. [31][32][33][34][35][36] The Li X Mn 1.5 Ni 0.5 O 4 materials tested here are prepared in a manner known to produce a disordered Ni/Mn cation arrangement, resulting in phase-behavior mirroring that of Li X Mn 2 O 4 : initial delithiation occurs through a solid solution, followed by a first-order phase transformation between two cubic phases with a linear misfit strain of ∼1.0%. When the Ni/Mn transition metals are ordered, delithiation occurs through two distinct first-order phase transformations each with a linear misfit strain of ∼1.0%.…”

Section: -24mentioning

confidence: 99%

Strategies to Avert Electrochemical Shock and Their Demonstration in Spinels

Woodford

Carter

Chiang

2014

J. Electrochem. Soc.

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We demonstrate that extensive electrochemical shock-electrochemical cycling induced fracture-occurs due to coherency stresses arising from first order cubic-to-cubic phase transformations in the spinels LiMn 2 O 4 and LiMn 1.5 Ni 0.5 O 4 . Electrochemical shock occurs despite the isotropy of the shape changes in these materials. This electrochemical shock mechanism is strongly sensitive to particle size; for LiMn 2 O 4 and LiMn 1.5 Ni 0.5 O 4 , fracture can be averted with particle sizes smaller than ∼1 μm. As a further critical test of the proposed mechanism, iron-doping was used to induce continuous solid solubility of lithium in LiMn Batteries based on ion-intercalation reactions-exemplified by lithium-ion batteries-enable high energy densities which are attractive for applications ranging from portable electronics to electrified transportation to grid-level storage. To achieve high storage capacities and energy density, ion-intercalation hosts must undergo large composition changes, which are often accompanied by large shape changes. These shape changes can result in electrochemical cycling-induced fracture, a phenomenon we have termed "electrochemical shock," which contributes to impedance growth and performance degradation. Electrochemical shock has been observed in a variety of ionintercalation materials with widely varying compositions and crystal structures 1-7 and it can cause severe deleterious effects on battery performance, manifested as impedance growth upon cycling. This has been clearly demonstrated during early cycling (first 500 cycles) of LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) cathodes, for example. 3 Previously, we and others showed that electrochemical shock in intercalation electrodes can be C-rate dependent, such as occurs when steep gradients in ion concentration generate diffusion-induced stresses sufficient to cause fracture. 8,9 Alternatively, electrochemical shock can occur by C-rate independent mechanisms, such as anisotropic shape changes in polycrystalline aggregates (e.g. secondary particles); this mechanism depends on crystal symmetry and state-of-charge, but not on cycling rate. Layered LiCoO 2 and isostructural derivative compounds such as Li(Ni,Co,Al)O 2 are a few examples amongst many in which electrochemical shock is dominated by the C-rate independent anisotropic shape change mechanism.10,11 (In distinguishing C-rate dependent vs. independent, we consider the rate dependence of a mechanism, not of a material. We have adopted a convention of calling C-rate independent any electrochemical shock mechanism that persists to arbitrarily small C-rates. Therefore, if electrochemical shock is observed during low C-rate cycling, this is clear evidence that a C-rate independent mechanism is active. At sufficiently high C-rates, the C-rate dependent concentration gradient mechanism will be simultaneously active and the observed damage accumulation in a given material may not be C-rate independent.) This classification scheme applies most directly to materials that undergo brittle fracture,...

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“…The degree of transition metal ordering in the high voltage spinel with the nominal composition LiNi 0.5 Mn 1.5 O 4 is expected to affect the voltage profile and other electrochemical characteristics of the material in operating cells 15 . In ordered materials (space group P4 3 32), the Ni and Mn occupy 4a and 12d octahedral sites, respectively, whereas in the disordered variants (space group Fd3_m) the transition metals are distributed randomly over octahedral 16d sites.…”

Section: Planning Of Experimentsmentioning

confidence: 99%

Characterization of Electrode Materials for Lithium Ion and Sodium Ion Batteries Using Synchrotron Radiation Techniques

Doeff

Chen

Cabana

et al. 2013

JoVE

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Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Naion batteries. During insertion or removal of alkali metal ions, the redox states of transition metals in the compounds change and structural transformations such as phase transitions and/or lattice parameter increases or decreases occur. These behaviors in turn determine important characteristics of the batteries such as the potential profiles, rate capabilities, and cycle lives. The extremely bright and tunable x-rays produced by synchrotron radiation allow rapid acquisition of high-resolution data that provide information about these processes. Transformations in the bulk materials, such as phase transitions, can be directly observed using X-ray diffraction (XRD), while X-ray absorption spectroscopy (XAS) gives information about the local electronic and geometric structures (e.g. changes in redox states and bond lengths). In situ experiments carried out on operating cells are particularly useful because they allow direct correlation between the electrochemical and structural properties of the materials. These experiments are time-consuming and can be challenging to design due to the reactivity and air-sensitivity of the alkali metal anodes used in the half-cell configurations, and/or the possibility of signal interference from other cell components and hardware. For these reasons, it is appropriate to carry out ex situ experiments (e.g. on electrodes harvested from partially charged or cycled cells) in some cases. Here, we present detailed protocols for the preparation of both ex situ and in situ samples for experiments involving synchrotron radiation and demonstrate how these experiments are done. Video LinkThe video component of this article can be found at

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Revealing the coupled cation interactions behind the electrochemical profile of LixNi0.5Mn1.5O4

Cited by 75 publications

References 38 publications

High electrochemical performance of high-voltage LiNi0.5Mn1.5O4 by decoupling the Ni/Mn disordering from the presence of Mn3+ ions

High electrochemical performance of high-voltage LiNi0.5Mn1.5O4 by decoupling the Ni/Mn disordering from the presence of Mn3+ ions

Strategies to Avert Electrochemical Shock and Their Demonstration in Spinels

Characterization of Electrode Materials for Lithium Ion and Sodium Ion Batteries Using Synchrotron Radiation Techniques

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