Microscopy Study of Structural Evolution in Epitaxial LiCoO<sub>2</sub> Positive Electrode Films during Electrochemical Cycling

Tan, Haiyan; Takeuchi, Saya; Bharathi, K. Kamala; Takeuchi, Ichiro; Bendersky, Leonid A.

doi:10.1021/acsami.5b12025

Cited by 39 publications

(63 citation statements)

References 46 publications

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“…This contributes to promote the charge and discharge electrochemical cycles when this compound is used as a cathode in lithium-ion batteries. 10,[71][72][73] The densities of states, in Figure 9, show a contribution predominance of the oxygen p orbitals and cobalt d orbitals in the HOMO/LUMO frontier orbitals and small contribution of the hybridization between these orbitals.The analyses by SEM (Figure 10) show the morphology, texture and habit of the HT-LiCoO 2 synthesized with the starch and gelatin precursors and in the blank test. We also present the SEM analyses using the citric acid and glycine precursors in Figure S7 (Supplementary Information).…”

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Synthesis and Characterization of LiCoO2 from Different Precursors by Sol‑Gel Method

Freitas

Siqueira

Costa

et al. 2017

J. Braz. Chem. Soc.

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Lithium cobalt oxide, LiCoO 2 , widely used as cathode in lithium ion batteries was synthesized and their structural and electronic properties investigated. The crystalline powders were prepared by the sol-gel method with four complexing agents: citric acid, glycine, starch and gelatin. These syntheses were compared with the blank test (without complexing agent). The X-ray diffraction and vibrational spectroscopy allowed the identification of the rhombohedral phase LiCoO 2 ( ) as the only or principal crystalline component in all samples. A small fraction of a second phase of cubic spinel Co 3 O 4 was observed in the samples of starch, gelatin and the blank test. The Rietveld refinements showed small structural variations, indicating reduced influence of the complexing agents on the synthesis. The theoretical HOMO-LUMO (highest occupied molecular orbital-lowest unoccupied molecular orbital) gap values are in agreement to those estimated by diffuse reflectance spectroscopy (DRS). The scanning electron microscopy (SEM) showed morphological pattern regardless of the complexing agent used, showing an alternative method.Keywords: LiCoO 2 , sol-gel method, XRD, Rietveld refinement, lithium ion batteries, DFT IntroductionLithium cobalt oxide, LiCoO 2 , has been the focus of many studies regarding their structural and electronic properties. [1][2][3][4][5][6][7][8] This system has interesting electrochemical features that allows a wide use as cathodes of lithium ion batteries. 2,4 The investigation of the structural aspects of the material is a crucial issue to better understand the electrochemical properties of the LiCoO 2 compound. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] For example, the nature of the crystal, its size and shape, are directly related with its electrochemical characteristics. 2 The LiCoO 2 synthesized at low temperatures (LT), below 500 °C, presents a cubic spinel structure ( ), while the synthesis at high temperatures (HT) (above 500 °C), generates the rhombohedral structure with stratified layers ( ). Therefore, several authors usually classify these structures as LT-LiCoO 2 and HT-LiCoO 2 , respectively . 1,2,7,8,[18][19][20][21][22][23][24] The rhombohedral phase is characterized by a structure with alternating layers of cobalt and lithium cations intercalated with oxygen anions. 22 The lithium and cobalt(III) ions are arranged in intercalated layers (Figure 1a). The cobalt(III) ion is located at the octahedral sites, forming a strong bond with the neighboring oxygen anion to constitute the Co−O layers (Figure 1b). Finally, the lithium layers are intercalated between the CoO 2 plans. 1,3,4 The octahedral sites of these layers are occupied by lithium and cobalt(III) ions alternately that forms a sequential stacking with oxygen ion layers in a close packing of the ABCABC type ( Figure 1c). 4,5 This specific stacking arrangement leads to an environment equivalent for all ions, allowing the maximum charge delocalization and the minimal system energy. 1,3,4 The degree of crystal orde...

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Synthesis and Characterization of LiCoO2 from Different Precursors by Sol‑Gel Method

Freitas

Siqueira

Costa

et al. 2017

J. Braz. Chem. Soc.

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“…By comparing with the spectra of the standard transition metal oxide compounds, it is revealed that the average valence states of the Co, Mn, and Ti ions in the as‐synthesized NCMT‐2 are 2+, 3.7+, and 4+. It is very surprising that Co ions can be stabilized at 2+ in the P2‐type layer‐structured compounds, since the valence state of Co ions in most layer‐structured cathode materials is 3+ 12, 23, 39. In addition, the valence state of Mn ions in NCMT‐2 is 3.7+, which is higher than Mn 3+ in tunnel‐structured Na 0.66 Mn 0.66 Ti 0.34 O 2 18.…”

Section: Resultsmentioning

confidence: 99%

Utilizing Co²⁺/Co³⁺ Redox Couple in P2‐Layered Na_0.66Co_0.22Mn_0.44Ti_0.34O₂ Cathode for Sodium‐Ion Batteries

Wang

Pan

et al. 2017

Advanced Science

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Developing sodium‐ion batteries for large‐scale energy storage applications is facing big challenges of the lack of high‐performance cathode materials. Here, a series of new cathode materials Na0.66CoxMn0.66– xTi0.34O2 for sodium‐ion batteries are designed and synthesized aiming to reduce transition metal‐ion ordering, charge ordering, as well as Na+ and vacancy ordering. An interesting structure change of Na0.66CoxMn0.66– xTi0.34O2 from orthorhombic to hexagonal is revealed when Co content increases from x = 0 to 0.33. In particular, Na0.66Co0.22Mn0.44Ti0.34O2 with a P2‐type layered structure delivers a reversible capacity of 120 mAh g−1 at 0.1 C. When the current density increases to 10 C, a reversible capacity of 63.2 mAh g−1 can still be obtained, indicating a promising rate capability. The low valence Co2+ substitution results in the formation of average Mn3.7+ valence state in Na0.66Co0.22Mn0.44Ti0.34O2, effectively suppressing the Mn3+‐induced Jahn–Teller distortion, and in turn stabilizing the layered structure. X‐ray absorption spectroscopy results suggest that the charge compensation of Na0.66Co0.22Mn0.44Ti0.34O2 during charge/discharge is contributed by Co2.2+/Co3+ and Mn3.3+/Mn4+ redox couples. This is the first time that the highly reversible Co2+/Co3+ redox couple is observed in P2‐layered cathodes for sodium‐ion batteries. This finding may open new approaches to design advanced intercalation‐type cathode materials.

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“…This basis becomes evident as we examine results from our previously (or yet to be published) reports on cathode materials that cover a range of chemistries and phases [12][13][14][15]. The underlying feature, namely the oxygen sublattice, is identified as the commonality between these different crystallographic phases, and the one that facilitates the observed epitaxial growth.…”

Section: Introductionmentioning

confidence: 94%

“…Pulsed laser deposition (PLD) is a well-established method that is suitable for producing high-quality dense oxide films without post-deposition annealing. Several research groups have utilized PLD to deposit and study different epitaxial cathode films, such as layered LiCoO 2 [7][8][9][10][11][12][13][14], different Li-Mn-O structures [15][16][17][18][19], and compositionally complex Li-TM-O (TM = Co, Mn, Ni) [20][21][22][23][24]. In our previous work, we demonstrated that robust electrochemical measurements (cyclic voltammetry and impedance spectroscopy) can be performed on such binder-free films by utilizing SrRuO 3 (SRO)-Epitaxially deposited on single-crystal SrTiO 3 (STO) substrates-As a conductive electrode [12]; with this approach, it has been shown that different stages of cycling can be studied by atomic resolution scanning TEM (STEM) [13].…”

Section: Introductionmentioning

confidence: 99%

Crystallography and Growth of Epitaxial Oxide Films for Fundamental Studies of Cathode Materials Used in Advanced Li-Ion Batteries

Bendersky

Tan²,

Bharathi

et al. 2017

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Li-ion battery systems, synthesized as epitaxial thin films, can provide powerful insights into their electrochemical processes. Crystallographic analysis shows that many important cathode oxides have an underlying similarity: their structures can be considered as different ordering schemes of Li and transition metal ions within a pseudo-cubic sublattice of oxygen anions arranged in a face-center cubic (FCC) fashion. This oxygen sublattice is compatible with SrTiO 3 and similar perovskite oxides, thus perovskites can be used as supporting substrates for growing epitaxial cathode films. The predicted epitaxial growth and crystallographic relations were experimentally verified for different oxide films deposited by pulsed laser deposition (PLD) on All results demonstrated the feasibility of epitaxial growth for these materials, with the growth following the predicted cube-on-cube orientation relationship between the cubic and pseudo-cubic oxygen sublattices of a substrate and a film, respectively.

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Microscopy Study of Structural Evolution in Epitaxial LiCoO₂ Positive Electrode Films during Electrochemical Cycling

Cited by 39 publications

References 46 publications

Synthesis and Characterization of LiCoO2 from Different Precursors by Sol‑Gel Method

Synthesis and Characterization of LiCoO2 from Different Precursors by Sol‑Gel Method

Utilizing Co²⁺/Co³⁺ Redox Couple in P2‐Layered Na_0.66Co_0.22Mn_0.44Ti_0.34O₂ Cathode for Sodium‐Ion Batteries

Crystallography and Growth of Epitaxial Oxide Films for Fundamental Studies of Cathode Materials Used in Advanced Li-Ion Batteries

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Microscopy Study of Structural Evolution in Epitaxial LiCoO2 Positive Electrode Films during Electrochemical Cycling

Cited by 39 publications

References 46 publications

Synthesis and Characterization of LiCoO2 from Different Precursors by Sol‑Gel Method

Synthesis and Characterization of LiCoO2 from Different Precursors by Sol‑Gel Method

Utilizing Co2+/Co3+ Redox Couple in P2‐Layered Na0.66Co0.22Mn0.44Ti0.34O2 Cathode for Sodium‐Ion Batteries

Crystallography and Growth of Epitaxial Oxide Films for Fundamental Studies of Cathode Materials Used in Advanced Li-Ion Batteries

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Microscopy Study of Structural Evolution in Epitaxial LiCoO₂ Positive Electrode Films during Electrochemical Cycling

Utilizing Co²⁺/Co³⁺ Redox Couple in P2‐Layered Na_0.66Co_0.22Mn_0.44Ti_0.34O₂ Cathode for Sodium‐Ion Batteries