Honeycomb-Ordered Na3Ni1.5M0.5BiO6 (M = Ni, Cu, Mg, Zn) as High

Subscriber access provided by READING UNIV

Letter

Honeycomb-Ordered Na3Ni1.5M0.5BiO6 (M = Ni, Cu, Mg, Zn) as High Voltage Layered Cathodes for Sodium-Ion Batteries Peng-Fei Wang, Yu-Jie Guo, Hui Duan, Tong-Tong Zuo, Enyuan Hu, Klaus Attenkofer, Hongliang Li, Xiu Song Zhao, Ya-Xia Yin, Xiqian Yu, and Yu-Guo Guo ACS Energy Lett., Just Accepted Manuscript • DOI: 10.1021/acsenergylett.7b00930 • Publication Date (Web): 01 Nov 2017 Downloaded from http://pubs.acs.org on November 3, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Energy Letters is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Energy Letters

Honeycomb-Ordered Na3Ni1.5M0.5BiO6 (M = Ni, Cu, Mg, Zn) as High Voltage Layered Cathodes for Sodium-Ion Batteries Peng-Fei Wang,a,d,† Yu-Jie Guo,a,d,† Hui Duan,a,d Tong-Tong Zuo,a,d Enyuan Hu,e Klaus Attenkofer,e Hongliang Li,c Xiu Song Zhao,c Ya-Xia Yin,a,d,* Xiqian Yu b,* and Yu-Guo Guo a,d,* a

CAS

Key

Laboratory

of

Molecular

Nanostructure

and

Nanotechnology

CAS

Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences (CAS), Beijing 100190, China b

Beijing National Laboratory for Condensed Matter Physics Institute of Physics, Chinese

Academy of Sciences (CAS) Beijing 100190, China c

Institute of Materials for Energy and Environment, Laboratory of New Fiber Materials and

Modern Textile, Growing Basis for State Key Laboratory, College of Materials Science and Engineering, Qingdao University Qingdao 266071, China d

University of Chinese Academy of Sciences, Beijing 100049, China

e

Brookhaven National Laboratory, Upton, New York 11973, USA

† These authors contributed equally to this work.

ACS Paragon Plus Environment

1

ACS Energy Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

*

To

whom

correspondence

should

be

addressed.

Page 2 of 22

E-mail:

[email protected];

[email protected]; [email protected]

ABSTRACT Developing high voltage layered cathodes for sodium ion batteries (SIBs) has always been a severe challenge. Herein, a new family of honeycomb-layered Na3Ni1.5M0.5BiO6 (M = Ni, Cu, Mg, Zn) with a monoclinic superstructure has been shown to combine good Na+ (de)intercalation activity with a competitively 3.3 V high voltage. By coupling the electrochemical process with ex situ X-ray absorption spectroscopy as well as in situ X-ray diffraction, the charge compensation mechanism and structural evolution of these new cathodes are clearly investigated. Interestingly, both Ni2+/Ni3+ and Cu2+/Cu3+ participate in the redox reaction upon cycling and the succession of single-phase, two-phase or three-phase regions upon Na+ extraction/insertion were identified with a rather good accuracy. This research strategy could provide insights into the structure−function−property relationships on a new series of honeycomb-ordered materials with the general formula, Na3Ni1.5M0.5BiO6, and also serve as a bridge to guide future design of high performance cathodes for SIBs.


2

Page 3 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Energy Letters

Sodium ion batteries (SIBs) have been identified as a promising technology due to sodium’s low cost, virtually unlimited supply as well as its electrochemical similarities to lithium.1-6 In recent years, the exploration of SIBs materials especially cathode materials have been intensively studied.7-11 Layered transition metal oxides NaxMO2 (M = Fe, Co, Ni, Mn, Cr, V and etc.) represents one of the most promising cathode candidates due to their environmental benignity, easy synthesis, and potential high capacity since the early 1980s.12-18 Suggested by Delmas19 et al., Na based layered oxides can be commonly categorized into P2-type (prismatic) and O3-type (octahedral) according to the occupied Na sites and the number of unique oxide layer packing. Once the typical hexagonal lattice contains in-plane distortion, a prime symbol (′) is additionally added to the abbreviation to differentiate the notation, such as monoclinic O′3-type NaNiO220 with C2/m space group and orthorhombic P′2-type NaxMnO221 with Cmcm space group. Compared with P2-type materials, which has a comparatively lower initial Na content,22-23 O3type cathode materials usually deliver a relatively large specific capacity and reversible electrochemistry when cycled below 4.0 V, leading to advantages regarding practical Na full cell fabrication. But the available energy density of the battery is limited to that a large amount of their capacity lies at relatively lower voltages than 3 V. What’s worse, many O3-type materials suffer from Na-driven complicated phase transition, which might result in unsatisfactory battery performance.24-25 Thus searching for new O3-type cathode with high voltage and understanding their reaction mechanism by monitoring the structural evolution occurring during Na+ extraction/insertion process, which are closely related to their electrochemistry, are of great significance and could help design high performance Na cells. With this perspective, we paid our attention on a new series of layered honeycomb-ordered O′3-Na3Ni1.5M0.5BiO6 (M = Ni, Cu, Mg, Zn) phases, which is structurally related to the layered


3

ACS Energy Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 22

NaxMO2 with an Ni2+/Bi5+ cationic honeycomb ordering or a superstructure within the each slab because of the notable difference between M2+ and Bi5+.26-27 In theory, these Ni containing transition metal oxides with honeycomb type arrangement have the potential to make full use of Ni2+→Ni3+→Ni4+ redox chemistry, possibly realizing the high voltage in SIBs. Furthermore, the development of this new type of sodium bismuthides cathodes for SIBs requires an in-depth understanding of the structure−function−property relationships in order to rationally design better electrodes. Under this circumstance, owing to the same valence and similar ionic radius between Ni2+ (0.69 Å) and Cu2+ (0.73 Å), Mg2+ (0.72 Å), Zn2+ (0.74 Å), we performed a deep and comprehensive study to exemplify and elucidate the electrochemical properties, phase transitions, and Na+ transport kinetics of four highly honeycomb-ordered O′3-Na3Ni1.5M0.5BiO6 (M = Ni, Cu, Mg, Zn) as high voltage cathode materials for SIBs. Among these layered bismuthides, typical Na3Ni1.5Cu0.5BiO6 delivers a discharge capacity of 94 mA h g−1, high discharge voltage plateaus at 3.3 V as well as a high recharge rate due to two Na+ (de)intercalation per unit, indicating a brand-new family of Na-storage cathodes materials for SIBs. The charge compensation mechanism for the Ni2+/Ni3+ and Cu2+/Cu3+ as active redox couples during cycling were confirmed by ex situ X-ray absorption spectroscopy (XAS) analysis. Operando X-ray diffraction (XRD) study further revealed that partial Cu/Mg/Zn substitution for Ni effectively suppresses the P′3−O1 phase transition occurring in Na3Ni2BiO6 at the second voltage plateau, improve the structure stability of the P′3 phase over a wide composition range but simultaneously increases the irreversibility of the electrochemical reaction. The Na3Ni1.5M0.5BiO6 (M = Ni, Cu, Mg, Zn) compounds were prepared by a solid-state method as detailed in the Supporting Information. The substitution amounts x = 0.5 were selected for the optimal amounts which allow full utilization of the Ni2+/4+ redox couples. The


4

Page 5 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Energy Letters

XRD patterns of all the samples can be indexed to a monoclinic unit cell (C2/m space group) without any impurities, revealing an even introduction of M2+ into the lattice of the Na3Ni2BiO6. To evaluate the lattice parameters change of the Na3Ni1.5M0.5BiO6 compounds after Cu/Mg/Zn substitution, the obtained structure of typical Na3Ni2BiO6 and Na3Ni1.5Cu0.5BiO6 were refined by the Rietveld method as shown in Figure 1a, b, respectively. According to the refined crystallographic data listed in Tables S1 and S2 (Supporting Information), the Ni, Cu ions occupy the octahedral 2a and 4g Wyckoff sites, suggesting Cu substitutes for partial Ni in the MO2 layer. Due to a slightly larger ionic radius of Cu2+ (0.73 Å) than Ni2+ (0.69 Å), the lattice parameters (a, b, c) of Na3Ni1.5Cu0.5BiO6 (a = 5.4140(7) Å, b = 9.3582(3) Å, c = 5.6925(8) Å, and β = 108.60(8)°) slightly increases upon Cu substitution in contrast to the unsubstituted ones (a = 5.4022(8) Å, b = 9.3530(4) Å, c = 5.6821(0) Å, and β = 108.51(0)°) as shown in Figure 1c and Table S3 (Supporting Information). Similar substitution effects were also observed in the Na3Ni1.5Mg0.5BiO6 and Na3Ni1.5Zn0.5BiO6 samples (Figure S1, S2 and Table S3, Supporting Information). A set of superstructure reflections (marked with asterisks) located at 18–33° 2θ angle are ascribed to a high degree of Ni and Bi cations ordering within the slab layer. In addition, an asymmetric broadening peak located at 2θ = 18.9° is clearly observed due to the presence of stacking faults, which are favoured by the ease of slab gliding between two sodium layers along the c axis in these characteristic “honeycomb” layered materials.28 As illustrated in Figure 1d, six MO6 edge-sharing octahedron surround one BiO6 octahedron in this honeycomb ordered structure, forming the superstructure lattice and the Na+ are hosted within the M2BiO6 slabs. The morphologies of the samples were characterized by scanning electron microscopy (SEM) as shown in Figure S3 (Supporting Information). All the Na3Ni1.5M0.5BiO6 (M = Ni, Cu, Mg, Zn)


5

ACS Energy Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 22

powders exhibit micrometer scale with plate morphology, and a increased particle size is observed for Zn > Cu > Ni > Mg. The detailed crystal structure of the copper substituted Na3Ni1.5Cu0.5BiO6 and Na3Ni2BiO6 is further investigated by high resolution transmission electron microscopy (HRTEM). The chosen thin particles (Figure 2a) went through a ground and dispersed process before TEM analysis. The interfringe distance of Na3Ni1.5Cu0.5BiO6 (Figure 2b) and Na3Ni2BiO6 (Figure S4, Supporting Information) is measured to be 4.04 Å and 4.05 Å, respectively, which corresponds to the (111)M plane in monoclinic symmetry. To better understand the in-plane honeycomb ordering of M and Bi cations revealed by powder diffraction studies, selected area electron diffraction (SAED) studies were conducted for the typical Na3Ni1.5Cu0.5BiO6 (Figure 2c). All electron diffraction patterns were collected along [001] zones, which provides the information of stacking of octahedral layers along c-axis. It is found that only 110R and -120R special to larger primitive trigonal cell can be indexed using rhombohedral cell, suggesting that the R 3ത m model is insufficient for describing the ordered structure of Na3Ni1.5Cu0.5BiO6 on a local scale. All observed diffraction spots could be fully indexed by the √3×√3×1 P3112 trigonal supercell instead as marked in Figure 2c, the additional reflections that can only be indexed as superstructure peaks corresponds to the larger primitive trigonal cell, such as the 100P and 200P reflections visible in the [001]P zone axis.29 The observation of both the X-ray and electron diffraction superstructure suggest strong in-plane Ni/Cu and Bi honeycomb ordering preferences in the Na3Ni1.5Cu0.5BiO6 phase. Energy dispersive spectroscopy (EDS) elementary mapping of sodium, nickel, copper, bismuth, and oxygen in Na3Ni1.5Cu0.5BiO6 (Figure 2d) and Na3Ni2BiO6 (Figure S5, Supporting Information) reveal uniform elements distribution and successful incorporation of Cu into the compound.


6

Page 7 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Energy Letters

The electrochemical properties of these compounds in Na|1M NaClO4 in PC (5% FEC)|Na3Ni1.5M0.5BiO6 cell were tested at 0.1C (16 mA g−1) between 2.0 and 4.0 V. The reversible capacities obtained from the O3-Na3Ni1.5M0.5BiO6 samples are 95, 94, 79, and 79 mA h g−1 for M = Ni, Cu, Mg and Zn, respectively (Figure 3a). The Na3Ni1.5Mg0.5BiO6 and Na3Ni1.5Zn0.5BiO6 cathodes deliver around 25% capacity drop than the unsubstituted one because of the inactive 0.5 mol Mg2+ and Zn2+. Whereas the capacity is maintained the same for Na3Ni1.5Cu0.5BiO6 owing to the electrochemically active Cu2+/Cu3+ and/or oxygen anions as discussed later. Obviously, the O3-Na3Ni2BiO6 electrode exhibits two main voltage plateaus at 3.32 V (O′3−O′′3–P′3 transition) and 3.53 V (P′3–O1 transition). Cu/Mg/Zn substitution leads to smoother charge/discharge curves and a complete vanishing of the second voltage plateau at high voltages, indicating the suppressed P′3–O1 phase transition. And the typical charge/discharge curves of the substituted electrodes can be divided into two main sections: a long plateau around 3.3–3.4 V and a sloping part above 3.4 V. The voltage plateau is attributed to the O′3−O′′3–P′3 phase transformation while the sloping line at higher voltage results from a solid-solution domain with P′3-structure, supported by in situ XRD results in later parts. Figure 3b displays the typical CV curves of various Na3Ni1.5M0.5BiO6 (M = Ni, Cu, Mg and Zn) cathodes at a sweep rate of 0.1 mV s−1. Consistent with the charge/discharge curves, the Na3Ni2BiO6 shows two pairs of strong redox peaks located at 3.18/3.41 V and 3.44/3.56 V, corresponding to the O′3−O′′3–P′3 and P′3–O1 phase transitions, respectively. In contrast, the redox peak at 3.56 V vanishes and retains only one pair of reduction/oxidation peak at 3.25/3.40 V upon Cu/Mg/Zn substitution, demonstrating the P′3–O1 phase transition at higher potentials is effectively suppressed by the substitution of Ni by Cu/Mg/Zn. Unfortunately, the Cu/Mg/Zn substitution fails to improve the cyclic stability of the cathode due to the increased irreversibility of electrochemical structure


7

ACS Energy Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 22

evolution. After 100 cycles at 1C rate, the capacity retentions of Na3Ni2BiO6 cathode is 74%, while the Na3Ni1.5Cu0.5BiO6, Na3Ni1.5Mg0.5BiO6, and Na3Ni1.5Zn0.5BiO6 cathodes could preserve 62%, 52%, and 50% (Figure 3c) its initial discharge capacity, respectively. All cathodes hold a high Coulombic efficiency of ≈100% during the following cycling process except the first cycle (Figure 3c). The effect of Cu/Mg/Zn substitution on the rate capability of the Na3Ni2BiO6 electrodes was also investigated for their possible high-power applications (Figure 3d). Compared with the unsubstituted Na3Ni2BiO6, the Na3Ni1.5M0.5BiO6 (M = Cu, Mg and Zn) samples also deliver unsatisfactory rate capabilities. Further structural analysis suggest Cu/Mg/Zn substitution enlarges the M−O bond lengths and the thickness and volume of the MO6 octahedron due to the larger size of M2+ than Ni2+, leading to the shrinkage of the d-spacing of the Na-ion diffusion layer (Table S4, Supporting Information). So slightly slower Na+ diffusion (3.36 × 10−11 cm2 s−1 for Na3Ni2BiO6 vs 1.79 × 10−11 cm2 s−1 for Na3Ni1.5Cu0.5BiO6) as shown in Figure S6 and S7 (Supporting Information) are achieved upon Na+ (de)intercalation. X-ray photoelectron spectroscopy (XPS) results (Figure S8, Supporting Information) reveal the valence of nickel and bismuth ions remain unchanged after the incorporation of divalent Cu/Mg/Zn, thus solid solutions of the four O′3-Na3Ni1.5M0.5BiO6 compounds can be denoted as Na+3[Ni2+1.5M2+0.5Bi5+]O6. Ex situ XAS experiment (Figure 4) was performed to confirm the charge compensation mechanism of Na3Ni1.5Cu0.5BiO6 during the charge/discharge process. Figure 4a, b display the normalized X-ray absorption near-edge spectroscopy (XANES) spectra at the Ni K-edges and Cu K-edges of the Na3Ni1.5Cu0.5BiO6 electrodes collected at different charging/discharging depths. Reference spectra of NiO (Ni2+), LiNiO2 (Ni3+), Cu2O (Cu+) and CuO (Cu2+) are used to identify the valence states of nickel and copper elements. The Ni K-edge XANES spectra (Figure 4a) shows clearly shift towards the higher energy side (with half energy


8

Page 9 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Energy Letters

position E0.5 shifts ∼2 eV) as charging from 2.0 V to 4.0 V, which comparable in energy to that of LiNiIIIO2, manifesting the oxidation of nickel from Ni2+ to Ni3+. The result shows good agreement with the reported nickel-containing layered oxides.28, 30-32 Meanwhile, the Cu K-edge spectra only exhibits slight shift to higher energy side but with distinct shape changes upon charging to 4.0 V (Figure 4b), suggesting that the slight oxidation of Cu2+ to a higher valence state over the charge process. Due to the covalence between Cu and O, the oxidation of oxygen anions (O2-) is also very likely to occur.33-35 Therefore it can be concluded that that within the explored 2.0–4.0 V potential window, both cationic nickel and copper and anionic oxygen are electrochemically active and responsible for the charge compensation mechanism, corresponding to the observed 1.8 e− transfer in the electrochemical process and is identical to the cyclic voltammetry results.36-39 To grasp a deeper insight into the structure evolution of the Na3Ni1.5M0.5BiO6 cathodes, in situ XRD patterns of Na3Ni2BiO6 and typical Cu-substituted Na3Ni1.5Cu0.5BiO6 electrodes were examined as displayed in Figure 5a, b. The theoretic capacities of the four compounds (Ni: 164 mA h g−1, Cu/Zn: 163 mA h g−1, Mg: 170 mA h g−1) are used in the discussion parts to establish the relationship between the capacity and amounts of sodium being cycled. From the XRD patterns, the pristine monoclinic O′3 phase in Na3-xNi2BiO6 (x = 0) electrode is observed. On Na ions extraction, two sets of new (00l) peaks special to a new distorted O′′3 and monoclinic P′3 phase appeared at a lower angle, revealing a three-phase reaction with the coexistence of O′3, O′′3 and P′3 phases corresponding to 0.13−1.09 Na+ extraction, which matches well with the platform of the electrochemical profile in the voltage range of 3.32−3.40 V. Upon further Na+ extraction till the first 3.40 V charge plateau corresponding to 1.09 Na+ extraction, the diffraction lines special to the O′3 and O′′3 structure thoroughly disappeared and an new pure P′3 phase


9

ACS Energy Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 22

formed, which matches well with the capacity (59 mA h g−1) obtained from the electrochemical data. The Na3Ni2BiO6 cathode could preserve its P′3 structure till to 3.51 V (1.20 Na+ extraction). After charging to x = 1.80 in Na3-xNi2BiO6 at the second plateau domain, in addition to the P′3 phase, a new set of Bragg peaks located at 2θ values of 15.26°, 34.18°, 37.66° and 46.80° appeared, confirming the further phase transformation from the intermediate P′3 phase to this final phase with an O1 type layered structure upon further Na+ extraction, revealing a twophase reaction with the coexistence of P′3 and O1 phases for Na3-xNi2BiO6 (1.20 ≤ x ≤ 1.59) at the second 3.53 V voltage plateau. Finally, the Na3-xNi2BiO6 electrode exists as the single O1 phase till to 4 V (1.59 ≤ x ≤ 1.80). During the discharge process, the O1 phase starts to disappear, transforming reversibly to the P′3 phase, then the P′3 phase gradually disappeared, finally O′3 and O′′3 phase formed. After one full cycle, the initial O′3 type structure recovers with minor intermediate O′′3 phase remained presumably due to the loss of Na during sodium extraction and insertion reactions. The Cu-substituted cathode shows a different phase transition mechanism (Figure 5b). When charged to 3.28 V (0.25 Na+ extraction), the Na3-xNi1.5Cu0.5BiO6 cathode firstly transforms into a distorted O′′3 structure without forming any P′3 diffraction peaks. Then formed a three-phase domain with the coexistence of O′3, O′′3 and P′3 phases till the end of the first charge plateau at 3.40 V (1.09 Na+ extraction). Once the P′3 phase completely forms, a solid solution region is obtained without no extra peak for new phases till reaching 4 V (1.78 Na+ extraction). Noting that the initial O′3 type structure cannot recover after the first cycle, coexisting with a small amount of the O′′3 and P′3 phases even at the ultimate discharged state. In short, partial Cu substitution in Na3Ni2BiO6 could effectively suppress the P′3–O1 phase transition at high


10

Page 11 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Energy Letters

voltages as shown in Figure 5c, extend solid solution zone with P′3 phase over a wider compositional range. But this substitution method also increase the impossibility to recover the pristine O′3 phase at the meanwhile after the first charge/discharge process, which is consitent with the above cell performance of various Na3-xNi1.5M0.5BiO6 cathodes. It is well acknowledged that partial inactive metal substitution (Zn, Mg, Ti, Li and etc.) demonstrates effective to improve the structural stability of conventional transition metal disordered layer structured cathode materials for SIBs.40-43 In the case of the Na3Ni1.5M0.5BiO6 (M = Ni, Cu, Mg, Zn) layer structured materials, metal cations are preferably distributed in a highly honeycomb ordered manner within the MO2 layers due to notable difference between M2+ and Bi5+ ions, which has great influence on their electrochemistry and reaction mechanism upon Na+ (de)intercalation. On one hand, the size mismatch between M2+ and Bi5+ in this ordered structure would induce strain at local scale, which could be reduced by oxidation of Ni2+ to Ni3+.44-46 In other words, the incorporation of inactive metal might act as an detrimental factor rather than stabilizer compared with common layered oxides, which explains the Na3Ni1.5Cu0.5BiO6 shows the optimal cycling stability among the substituted ones in light of active Cu2+. On the other hand, every Ni atom is coordinated by three Bi and three Ni atoms, while each Bi atom is only surrounded by six Ni atoms (Figure S9, Supporting Information). Intriguingly, the charge rearrangement occurs with the oxidation of nickel from the divalent state to the trivalent state when the electrode is charged.47-48 The newly formed charge balance might be affected by the inert Mg2+ and Zn2+ in pristine Ni sites for the substituted Na3Ni1.5M0.5BiO6 cathodes. All in all, cations substitution in these transition metal ordered layered materials might not be a sensible method to improve the battery performance unless this high degree of honeycomb cationic ordering could be thoroughly broken by reasonably structure modulation.


11

ACS Energy Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 22

In summary, four complete honeycomb-layered phases O′3-Na3Ni1.5M0.5BiO6 (M = Ni, Cu, Mg, Zn) were synthesized by a simple solid state approach. All compositions crystallize in a monoclinic unit cell and exhibit a layered structure with a honeycomb cationic ordering within the slabs. The Na storage electrochemistry and the structure evolution during cycling for this new family of Na3Ni1.5M0.5BiO6 cathodes in SIBs is identified. Na3Ni1.5Cu0.5BiO6 shows the best electrochemical performance among the substituted cathodes: a considerable capacity (94 mA h g−1), high voltage (3.3 V of average voltage), owing to the Ni2+/Ni3+ and Cu2+/Cu3+ redox couples when used as positive electrode materials for SIBs. And less capacity reduction is observed compared to when Ni is substituted with inactive Mg or Zn. The presence of heterogeneous M2+ (M = Cu, Mg, Zn) cations stabilize the prismatic (P'3) lattice, suppress the P′3−O1 phase transition observed at high voltage in Na3Ni2BiO6 and retain the O′3−O′′3−P′3 phase transition instead, resulting in a smooth electrochemical profile with a high discharge voltage. However, the irreversibility of the electrochemical reaction was simultaneously increased for the substituted material at the end of the discharge possibility due to the breakage of charge balance and large structure strain in this ordered structure. Possible strategies for breaking the transition metal ordering and mitigating the detrimental irreversible phase transition in honeycomb-layered metal oxides with the general formula, Na3Ni1.5M0.5BiO6, need to be further proposed as high voltage and long life cathode candidates for SIBs. ASSOCIATED CONTENT Supporting Information


12

Page 13 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Energy Letters

Rietveld refinement patterns and structural parameters, SEM images, HR-TEM image and EDS maps, cyclic voltammograms at various sweep rates and corresponding peak current Ip as a function of square root of scan rate v1/2, XPS spectra, local structure illustration. AUTHOR INFORMATION Corresponding Author * E-mail: [email protected]; [email protected]; [email protected] Author Contributions † P.-F.W. and Y.-J. G. contributed equally to this work. Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This work was supported by the National Key R&D Program of China (Grant No. 2016YFA0202500), the National Natural Science Foundation of China (Grant Nos. 51772301 and 21127901), and the ‘Strategic Priority Research Program’ of the Chinese Academy of Sciences (Grant No. XDA09010100). This research used beam line ISS 8-ID of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704.


13

ACS Energy Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 22

Figure 1. Structural characterization results of the Na3Ni1.5M0.5BiO6 compounds, including the experimental

and

Rietveld

refinement

XRD

profiles

of

(a)

Na3Ni2BiO6

and

(b)

Na3Ni1.5Cu0.5BiO6. (c) Changes in lattice parameters of the Na3Ni1.5M0.5BiO6 (M = Ni, Cu, Mg, Zn) samples. (d) Crystal structure of Na3Ni1.5M0.5BiO6 viewed from the [010] axis (top) and the [001] axis (bottom).


14

Page 15 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Energy Letters

Figure 2. (a) TEM, (b) HRTEM images of (111) crystal planes and (c) [001] SAED patterns along the [001]R and [001]P zones of typical Na3Ni1.5Cu0.5BiO6 sample, the circle area in (a) shows the particle area chosen for HRTEM analysis. (d) The EDS maps of Na3Ni1.5Cu0.5BiO6 sample, demonstrating an even distribution of sodium, nickel, copper, bismuth, and oxygen elements in sample particles.


15

ACS Energy Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 22

Figure 3. Electrochemical performance of various Na3Ni1.5M0.5BiO6 (M = Ni, Cu, Mg, Zn) cathodes, including (a) galvanostatic charge/discharge voltage profiles at a 0.1C (1C = 108 mA g−1), (b) CV profiles at a scan rate of 0.1 mV s−1, (c) cycling performance at 1C rate and (d) rate capability at various charge-discharge rates.


16

Page 17 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Energy Letters

Figure 4. Ex situ XANES spectra at the (a) Ni K-edge and (b) Cu K-edge of Na3-xNi1.5Cu0.5BiO6 electrodes collected at different charge/discharge states. Reference spectra of NiO (Ni2+), LiNiO2 (Ni3+), Cu2O (Cu+) and CuO (Cu2+) have been used to identify the valence states.


17

ACS Energy Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 22

Figure 5. In situ XRD patterns collected during the first charge/discharge of the (a) Na /Na3Ni2BiO6, (b) Na/Na3Ni1.5Cu0.5BiO6 cells under a current rate of 0.1C at voltage range between 2 and 4 V. Black asterisks represent peaks from Al window. (c) Schematic illustration showing the phase transition mechanism during the Na insertion/extraction process.


18

Page 19 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Energy Letters

REFERENCES (1) Yabuuchi, N.; Kubota, K.; Dahbi, M.; Komaba, S. Research Development on Sodium-Ion Batteries. Chem. Rev. 2014, 114, 11636-82. (2) Hwang, J.-Y.; Myung, S.-T.; Sun, Y.-K. Sodium-Ion Batteries: Present and Future. Chem. Soc. Rev. 2017, 46, 3529-3614. (3) Xin, S.; You, Y.; Wang, S.; Gao, H. C.; Yin, Y. X.; Guo, Y. G. Solid-State Lithium Metal Batteries Promoted by Nanotechnology: Progress and Prospects. ACS Energy Lett. 2017, 2, 1385-1394. (4) Sun, Y.-K. Future of Electrochemical Energy Storage. ACS Energy Lett. 2017, 2, 716716. (5) Yan, Y.; Yin, Y.; Guo, Y.; Wan, L.-J. Effect of Cations in Ionic Liquids on the Electrochemical Performance of Lithium-Sulfur Batteries. Sci. China Chem. 2014, 57, 15641569. (6) Xin, S.; Chang, Z.; Zhang, X.; Guo, Y.-G. Progress of Rechargeable Lithium Metal Batteries Based on Conversion Reactions. Natl. Sci. Rev. 2017, 4, 54-70. (7) Li, Z.; Ma, L.; Surta, T. W.; Bommier, C.; Jian, Z.; Xing, Z.; Stickle, W. F.; Dolgos, M.; Amine, K.; Lu, J. et al. High Capacity of Hard Carbon Anode in Na-Ion Batteries Unlocked by POx Doping. ACS Energy Lett. 2016, 1, 395-401. (8) Berthelot, R.; Carlier, D.; Delmas, C. Electrochemical Investigation of the P2-NaxCoO2 Phase Diagram. Nat. Mater. 2011, 10, 74-80. (9) Zhu, C.; Kopold, P.; van Aken, P. A.; Maier, J.; Yu, Y. High Power-High Energy Sodium Battery Based on Threefold Interpenetrating Network. Adv. Mater. 2016, 28, 2409-16. (10) Boucher, F.; Gaubicher, J.; Cuisinier, M.; Guyomard, D.; Moreau, P. Elucidation of the Na2/3FePO4 and Li2/3FePO4 Intermediate Superstructure Revealing a Pseudouniform Ordering in 2D. J. Am. Chem. Soc. 2014, 136, 9144-57. (11) Lim, S. Y.; Lee, J. H.; Kim, S.; Shin, J.; Choi, W.; Chung, K. Y.; Jung, D. S.; Choi, J. W. Lattice Water for the Enhanced Performance of Amorphous Iron Phosphate in Sodium-Ion Batteries. ACS Energy Lett. 2017, 2, 998-1004. (12) Hwang, J.-Y.; Myung, S.-T.; Yoon, C. S.; Kim, S.-S.; Aurbach, D.; Sun, Y.-K. Novel Cathode Materials for Na-Ion Batteries Composed of Spoke-Like Nanorods of Na[Ni0.61Co0.12Mn0.27]O2 Assembled in Spherical Secondary Particles. Adv. Funct. Mater. 2016, 26, 8083-8093. (13) Hwang, J.-Y.; Yoon, C. S.; Belharouak, I.; Sun, Y.-K. A Comprehensive Study of the Role of Transition Metals in O3-Type Layered Na[NixCoyMnz]O2 (x = 1/3, 0.5, 0.6, and 0.8) Cathodes for Sodium-Ion Batteries. J. Mater. Chem. A 2016, 4, 17952-17959. (14) Kim, H.; Kim, H.; Ding, Z.; Lee, M. H.; Lim, K.; Yoon, G.; Kang, K. Recent Progress in Electrode Materials for Sodium-Ion Batteries. Adv. Energy Mater. 2016, 6, 1600943. (15) Han, M. H.; Gonzalo, E.; Singh, G.; Rojo, T. A Comprehensive Review of Sodium Layered Oxides: Powerful Cathodes for Na-Ion Batteries. Energy Environ. Sci. 2015, 8, 81-102. (16) Kim, S.-W.; Seo, D.-H.; Ma, X.; Ceder, G.; Kang, K. Electrode Materials for Rechargeable Sodium-Ion Batteries: Potential Alternatives to Current Lithium-Ion Batteries. Adv. Energy Mater. 2012, 2, 710-721. (17) Fang, C.; Huang, Y.; Zhang, W.; Han, J.; Deng, Z.; Cao, Y.; Yang, H. Routes to High Energy Cathodes of Sodium-Ion Batteries. Adv. Energy Mater. 2016, 6, 1501727.


19

ACS Energy Letters

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 22

(18) Kim, J.-K.; Kim, Y.; Park, S.; Ko, H.; Kim, Y. Encapsulation of Organic Active Materials in Carbon Nanotubes for Application to High-Electrochemical-Performance Sodium Batteries. Energy Environ. Sci. 2016, 9, 1264-1269. (19) Delmas, C.; Fouassier, C.; hagenmuller, P. Structural Classification and Properties of the Layered Oxides. Physica 1980, 99B, 81-85. (20) Vassilaras, P.; Ma, X.; Li, X.; Ceder, G. Electrochemical Properties of Monoclinic NaNiO2. J. Electrochem. Soc. 2012, 160, A207-A211. (21) Doeff, M. M.; Peng, M. Y.; Ma, Y.; Jonghe, L. C. D. Orthorhombic NaxMnO2 as a Cathode Material for Secondary Sodium and Lithium Polymer Batteries. J. Electrochem. Soc. 1994, 141, L145-L147. (22) Wang, P.-F.; You, Y.; Yin, Y.-X.; Wang, Y.-S.; Wan, L.-J.; Gu, L.; Guo, Y.-G. Suppressing the P2-O2 Phase Transition of Na0.67Mn0.67Ni0.33O2 by Magnesium Substitution for Improved Sodium-Ion Batteries. Angew. Chem. Int. Ed. 2016, 55, 7445-9. (23) Wang, Y.; Xiao, R.; Hu, Y. S.; Avdeev, M.; Chen, L. P2-Na0.6[Cr0.6Ti0.4]O2 CationDisordered Electrode for High-Rate Symmetric Rechargeable Sodium-Ion Batteries. Nat. Commun. 2015, 6, 6954. (24) Li, X.; Wu, D.; Zhou, Y.-N.; Liu, L.; Yang, X.-Q.; Ceder, G. O3-Type Na(Mn0.25Fe0.25Co0.25Ni0.25)O2: A Quaternary Layered Cathode Compound for Rechargeable Na Ion Batteries. Electrochem. Commun. 2014, 49, 51-54. (25) Wang, P.-F.; You, Y.; Yin, Y.-X.; Guo, Y.-G. An O3-Type NaNi0.5Mn0.5O2 Cathode for Sodium-Ion Batteries with Improved Rate Performance and Cycling Stability. J. Mater. Chem. A 2016, 4, 17660-17664. (26) Seibel, E. M.; Roudebush, J. H.; Wu, H.; Huang, Q.; Ali, M. N.; Ji, H.; Cava, R. J. Structure and Magnetic Properties of the α-NaFeO2-Type Honeycomb Compound Na3Ni2BiO6. Inorg. Chem. 2013, 52, 13605-11. (27) Seibel, E. M.; Roudebush, J. H.; Ali, M. N.; Ross, K. A.; Cava, R. J. Structure and Magnetic Properties of the Spin-1/2-Based Honeycomb NaNi2BiO(6-δ) and Its Hydrate NaNi2BiO(6-δ).1.7H2O. Inorg. Chem. 2014, 53, 10989-95. (28) Liu, J.; Yin, L.; Wu, L.; Bai, J.; Bak, S. M.; Yu, X.; Zhu, Y.; Yang, X. Q.; Khalifah, P. G. Quantification of Honeycomb Number-Type Stacking Faults: Application to Na3Ni2BiO6 Cathodes for Na-Ion Batteries. Inorg. Chem. 2016, 55, 8478-92. (29) Ma, J.; Bo, S.-H.; Wu, L.; Zhu, Y.; Grey, C. P.; Khalifah, P. G. Ordered and Disordered Polymorphs of Na(Ni2/3Sb1/3)O2: Honeycomb-Ordered Cathodes for Na-Ion Batteries. Chem. Mater. 2015, 27, 2387-2399. (30) Yu, X.; Lyu, Y.; Gu, L.; Wu, H.; Bak, S.-M.; Zhou, Y.; Amine, K.; Ehrlich, S. N.; Li, H.; Nam, K.-W. et al. Understanding the Rate Capability of High-Energy-Density Li-Rich Layered Li1.2Ni0.15Co0.1Mn0.55O2 Cathode Materials. Adv. Energy Mater. 2014, 4, 1300950. (31) Vassilaras, P.; Kwon, D. H.; Dacek, S. T.; Shi, T.; Seo, D. H.; Ceder, G.; Kim, J. C. Electrochemical Properties and Structural Evolution of O3-Type Layered Sodium Mixed Transition Metal Oxides with Trivalent Nickel. J. Mater. Chem. A 2017, 5, 4596-4606. (32) Han, M. H.; Gonzalo, E.; Casas-Cabanas, M.; Rojo, T. Structural Evolution and Electrochemistry of Monoclinic NaNiO2 upon the First Cycling Process. J. Power Sources 2014, 258, 266-271. (33) Mu, L.; Xu, S.; Li, Y.; Hu, Y.-S.; Li, H.; Chen, L.; Huang, X. Prototype Sodium-Ion Batteries Using an Air-Stable and Co/Ni-Free O3-Layered Metal Oxide Cathode. Adv. Mater. 2015, 27, 6928-6933.


20

Page 21 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Energy Letters

(34) Zheng, L.; Li, J.; Obrovac, M. N. Crystal Structures and Electrochemical Performance of Air-Stable Na2/3Ni1/3–xCuxMn2/3O2 in Sodium Cells. Chem. Mater. 2017, 29, 1623-1631. (35) Wang, X.; Liu, G.; Iwao, T.; Okubo, M.; Yamada, A. Role of Ligand-to-Metal Charge Transfer in O3-Type NaFeO2–NaNiO2 Solid Solution for Enhanced Electrochemical Properties. J. Phys. Chem. C 2014, 118, 2970-2976. (36) Wang, J.; He, X.; Zhou, D.; Schappacher, F.; Zhang, X.; Liu, H.; Stan, M. C.; Cao, X.; Kloepsch, R.; Sofy, M. S. et al. O3-Type Na[Fe1/3Ni1/3Ti1/3]O2 Cathode Material for Rechargeable Sodium Ion Batteries. J. Mater. Chem. A 2016, 4, 3431-3437. (37) Wang, P. F.; Yao, H. R.; Liu, X. Y.; Zhang, J. N.; Gu, L.; Yu, X. Q.; Yin, Y. X.; Guo, Y. G. Ti-Substituted NaNi0.5Mn0.5-xTixO2 Cathodes with Reversible O3-P3 Phase Transition for High-Performance Sodium-Ion Batteries. Adv. Mater. 2017, 29, 1700210. (38) Zheng, S.; Zhong, G.; McDonald, M. J.; Gong, Z.; Liu, R.; Wen, W.; Yang, C.; Yang, Y. Exploring the Working Mechanism of Li+ in O3-Type NaLi0.1Ni0.35Mn0.55O2 Cathode Materials for Rechargeable Na-Ion Batteries. J. Mater. Chem. A 2016, 4, 9054-9062. (39) Komaba, S.; Yabuuchi, N.; Nakayama, T.; Ogata, A.; Ishikawa, T.; Nakai, I. Study on the Reversible Electrode Reaction of Na1-xNi0.5Mn0.5O2 for a Rechargeable Sodium-Ion Battery. Inorg. Chem. 2012, 51, 6211-20. (40) Xu, J.; Lee, D. H.; Clément, R. J.; Yu, X.; Leskes, M.; Pell, A. J.; Pintacuda, G.; Yang, X.-Q.; Grey, C. P.; Meng, Y. S. Identifying the Critical Role of Li Substitution in P2Nax[LiyNizMn1–y–z]O2 (0 < x, y, z < 1) Intercalation Cathode Materials for High-Energy Na-Ion Batteries. Chem. Mater. 2014, 26, 1260-1269. (41) Singh, G.; Tapia-Ruiz, N.; Lopez del Amo, J. M.; Maitra, U.; Somerville, J. W.; Armstrong, A. R.; Martinez de Ilarduya, J.; Rojo, T.; Bruce, P. G. High Voltage Mg-Doped Na0.67Ni0.3–xMgxMn0.7O2 (x = 0.05, 0.1) Na-Ion Cathodes with Enhanced Stability and Rate Capability. Chem. Mater. 2016, 28, 5087-5094. (42) Wu, X.; Guo, J.; Wang, D.; Zhong, G.; McDonald, M. J.; Yang, Y. P2-Type Na0.66Ni0.33– xZnxMn0.67O2 as New High-Voltage Cathode Materials for Sodium-Ion Batteries. J. Power Sources 2015, 281, 18-26. (43) Yoshida, H.; Yabuuchi, N.; Kubota, K.; Ikeuchi, I.; Garsuch, A.; Schulz-Dobrick, M.; Komaba, S. P2-Type Na2/3Ni1/3Mn2/3-xTixO2 as a New Positive Electrode for Higher Energy NaIon Batteries. Chem. Commun. 2014, 50, 3677-80. (44) Zvereva, E. A.; Stratan, M. I.; Ovchenkov, Y. A.; Nalbandyan, V. B.; Lin, J. Y.; Vavilova, E. L.; Iakovleva, M. F.; Abdel-Hafiez, M.; Silhanek, A. V.; Chen, X. J. et al. Zigzag Antiferromagnetic Quantum Ground State in Monoclinic Honeycomb Lattice Antimonates A3Ni2SbO6 (A = Li, Na). Phys. Rev. B 2015, 92, 144401. (45) Bhange, D. S.; Ali, G.; Kim, D.-H.; Anang, D. A.; Shin, T. J.; Kim, M.-G.; Kang, Y.-M.; Chung, K. Y.; Nam, K.-W. Honeycomb-Layer Structured Na3Ni2BiO6 as a High Voltage and Long Life Cathode Material for Sodium-Ion Batteries. J. Mater. Chem. A 2017, 5, 1300-1310. (46) Schmidt, W.; Berthelot, R.; Sleight, A. W.; Subramanian, M. A. Solid Solution Studies of Layered Honeycomb-Ordered Phases O3-Na3M2SbO6 (M=Cu, Mg, Ni, Zn). J. Solid State Chem. 2013, 201, 178-185. (47) Yuan, D.; Liang, X.; Wu, L.; Cao, Y.; Ai, X.; Feng, J.; Yang, H. A Honeycomb-Layered Na3Ni2SbO6: A High-Rate and Cycle-Stable Cathode for Sodium-Ion Batteries. Adv. Mater. 2014, 26, 6301-6. (48) You, Y.; Kim, S. O.; Manthiram, A. A Honeycomb-Layered Oxide Cathode for SodiumIon Batteries with Suppressed P3-O1 Phase Transition. Adv. Energy Mater. 2016, 1601698.


21

ACS Energy Letters

Page 22 of 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 ACS Paragon Plus Environment

22

Honeycomb-Ordered Na3Ni1.5M0.5BiO6 (M = Ni, Cu, Mg, Zn) as High

Recommend Documents