Conduction and Surface Effects in Cathode Materials: Li8ZrO6 and Doped Li8ZrO6

Huang, Shuping; Fang, Yuan; Wang, Bo; Wilson, Benjamin E.; Tran, Nam; Truhlar, Donald G.; Stein, Andreas

doi:10.1021/acs.jpcc.6b02077

Cited by 15 publications

(29 citation statements)

References 61 publications

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“…The movement of the vacancy involves the migration of Li + from an occupied site to a vacant site; thus, vacancy diffusion is described in terms of the simultaneous movement of a Li + and a hole polaron. We considered two such diffusion processes: (a) a cross process, in which the paths of the Li + and the polaron cross and (b) a side-by-side (SBS) process, in which the paths of Li + and the polaron are parallel . The results are given in Table .…”

Section: Resultsmentioning

confidence: 99%

“…For calculations on surfaces of LSO, based on our previous tests, 19 a vacuum layer of 10 Å was used to remove any interaction between the periodically repeated slabs of the most stable (0001) surface, and the five bottom layers of the slab were fixed at the positions in the bulk structure. A 3 × 3 × 1 kpoint mesh was used for the k-point sampling.…”

Section: Computational Detailsmentioning

confidence: 99%

“…We considered two such diffusion processes: (a) a cross process, in which the paths of the Li + and the polaron cross and (b) a side-by-side (SBS) process, in which the paths of Li + and the polaron are parallel. 19 The results are given in Table 6.…”

Section: T H I S C O N T E N T Imentioning

confidence: 99%

“…Because Sn(IV) has a full d subshell, we expect only anionic oxygen redox in LSO. , We have previously studied Li 8 ZrO 6 (LZO), which is also a solely anionic-redox cathode material. The electron transport mechanism in LZO mainly involves small-polaron diffusion of oxygen polarons. − By replacing the transition metal Zr with the main-group metal Sn, we obtain a material (LSO) that was found as a stable lithiated phase of SnO 2 in experiments. − Previous DFT calculations of different lithiated tin-based oxides were carried out mainly for predicting the binding energies of Sn 3d 5/2 to elucidate the core level chemical shift observed in the XPS measurement . However, the effect of delithiation in Li 8 SnO 6 on the electrochemical performance of tin-oxides as the cathode in the lithium-ion battery is not yet well-understood in the above-mentioned literature.…”

Section: Introductionmentioning

confidence: 99%

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Anionic Oxygen Redox in the High-Lithium Material Li₈SnO₆

et al. 2021

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Lithiated transition metal oxide cathode materials that combine oxygen-anion redox [O2 –/(O2) n−] with cation redox offer substantial capacities and higher voltage than cathodes without oxygen redox, but oxygen-anion redox is usually accompanied by the formation of peroxo or superoxo species that may cause oxygen release. To clarify the relationship between the oxygen release and peroxide and superoxide dimers without the complication of transition-metal redox, we performed density functional theory calculations to study the layered Li8SnO6 cathode because it has only oxygen-anion redox during delithiation. Features with O–O distances of ∼1.5 Å (corresponding to the formation of a peroxide) were observed at 75% lithium concentration, and further delithiation to 62.5% lithium concentration shortened the O–O bond distance to ∼1.3 Å (corresponding to the formation of superoxide). The solely anionic oxygen redox stabilizes the delithiated structure of Li8–x SnO6, and it does not cause structural disorder or release oxygen gas. Ab initio molecular dynamics calculations in the supercell at 300 K indicate that oxygen dimerization may occur at 75% lithium concentration. On the (0001) surface with a high lithium concentration (98%), oxygen dimerization is unfavorable. The calculations by HSE06 show that oxygen redox in Li8SnO6 offers an initial voltage (vs Li/Li+) greater than 4.2 V. The GGA+U calculations indicate that the Li+-polaron in Li95Sn12O72 migrates with a migration barrier of only 0.43 eV. This work also quantifies a solely anionic oxygen redox mechanism in Li8SnO6, and it provides a deeper understanding of anionic oxygen redox in Li-excess oxide cathode materials.

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Section: Resultsmentioning

confidence: 99%

Section: Computational Detailsmentioning

confidence: 99%

Section: T H I S C O N T E N T Imentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Anionic Oxygen Redox in the High-Lithium Material Li₈SnO₆

et al. 2021

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“…These U values are adopted according to the simulation parameters of Li(Ni x Mn y Co z )O 2 models from the Materials Project Web site () and our own tests . Recent studies reported that for some kinds of TM oxides as cathode materials (e.g., Li 8 ZrO 6 ), applying U to p orbitals of oxygen during charging can give a correct picture of oxygen polaron but that PBE cannot. We tested and applied U (1 eV) to p orbitals of oxygen for (333) at SOC = 0.33 and 0.66, respectively.…”

Section: Experimental Methodsmentioning

confidence: 99%

Tuning of Thermal Stability in Layered Li(Ni_xMn_yCo_z)O₂

et al. 2016

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Understanding and further designing new layered Li(NiMnCo)O (NMC) (x + y + z = 1) materials with optimized thermal stability is important to rechargeable Li batteries (LIBs) for electrical vehicles (EV). Using ab initio calculations combined with experiments, we clarified how the thermal stability of NMC materials can be tuned by the most unstable oxygen, which is determined by the local coordination structure unit (LCSU) of oxygen (TM(Ni, Mn, Co)-O-Li): each O atom bonds with three transition metals (TM) from the TM-layer and three to zero Li from fully discharged to charged states from the Li-layer. Under this model, how the lithium content, valence states of Ni, contents of Ni, Mn, and Co, and Ni/Li disorder to tune the thermal stability of NMC materials by affecting the sites, content, and the release temperature of the most unstable oxygen is proposed. The synergistic effect between Li vacancies and raised valence state of Ni during delithiation process can aggravate instability of oxygen, and oxygen coordinated with more nickel (especially with high valence state) in LSCU becomes more unstable at a fixed delithiation state. The Ni/Li mixing would decrease the thermal stability of the "Ni═Mn" group NMC materials but benefit the thermal stability of "Ni-rich" group, because the Ni in the Li layer would form 180° Ni-O-Ni super exchange chains in "Ni-rich" NMC materials. Mn and Co doping can tune the initial valence state of Ni, local coordination environment of oxygen, and the Ni/Li disorder, thus to tune the thermal stability directly.

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