Recently, anionic‐redox‐based materials have shown promising electrochemical performance as cathode materials for sodium‐ion batteries. However, one of the limiting factors in the development of ...oxygen‐redox‐based electrodes is their low operating voltage. In this study, the operating voltage of oxygen‐redox‐based electrodes is raised by incorporating nickel into P2‐type Na2/3Zn0.3Mn0.7O2 in such a way that the zinc is partially substituted by nickel. As designed, the resulting P2‐type Na2/3(Ni0.5Zn0.5)0.3Mn0.7O2 electrode exhibits an average operating voltage of 3.5 V and retains 95% of its initial capacity after 200 cycles in the voltage range of 2.3–4.6 V at 0.1C (26 mA g−1). Operando X‐ray diffraction analysis reveals the reversible phase transition: P2 to OP4 phase on charge and recovery to the P2 phase on discharge. Moreover, ex situ X‐ray absorption near edge structure and X‐ray photoelectron spectroscopy studies reveal that the capacity is generated by the combination of Ni2+/Ni4+ and O2−/O1− redox pairs, which is supported by first‐principles calculations. It is thought that this kind of high voltage redox species combined with oxygen redox could be an interesting approach to further increase energy density of cathode materials for not only sodium‐based rechargeable batteries, but other alkali‐ion battery systems.
Herein, the fabrication of a cathode that achieves a high operating voltage via Ni substitution in P2‐Na2/3(Ni0.5Zn0.5)0.3Mn0.7O2. The cathode delivers outstanding electrochemical performance as well as structural stability for prolonged cycling.
In this work, the rational design of O′3‐type NaNi2/3−xCoxSb1/3O2, a solid solution of NaNi2/3Sb1/3O2–NaCo2/3Sb1/3O2, is introduced. Because of the difficulty of the Co3+/2+ redox reaction, the ...electronic structures of NaNi2/3−xCoxSb1/3O2 compounds are engineered to build electroconducting networks in the oxide matrix through electrochemical oxidation of Co2+ to Co3+, after which the formed Co3+ does not participate in the electrochemical reaction but improves the electrical conductivity in the structure. Density functional theory calculations reveal a reduced bandgap energy after the formation of Co3+ during desodiation of Na1−yNi2/3−xCoxSb1/3O2. Using the oxidized Co3+ species while improving the electrical conductivity, the NaNi2/3−xCoxSb1/3O2 (x = 1/6) electrode exhibits excellent cyclability for 1000 cycles with ≈72.5% capacity retention at 2C (400 mA g−1) and activity even at 50C (10 A g−1) in Na cells. Operando X‐ray diffraction and ex situ X‐ray absorption near‐edge structure investigations reveal suppressed lattice variations upon charge and discharge compared with those of NaNi2/3Sb1/3O2 achieved by the presence of the electrochemical‐driven Co3+ in the structure. These findings offer a new strategy for the development of cathode materials for sodium‐ion batteries, providing important insight into their structural transformations and the electronic nature of advanced cathode materials.
The electronic structure of honeycomb layered NaNi2/3−xCoxSb1/3O2 is engineered as a cathode material for sodium‐ion batteries. The results emphasize that the electrochemically driven Co3+, which does not participate in the electrochemical reaction, not only enhances electrical conductivity but aids structural stabilization to suppress volume variation, leading to excellent long‐term cyclability.
Oxygen‐redox‐based cathode materials for sodium‐ion batteries (SIBs) have attracted considerable attention in recent years owing to the possibility of delivering additional capacity in the ...high‐voltage region. However, they still suffer from not only fast capacity fading but also poor rate capability. Herein, P2‐Na0.75Li0.15Ni0.15Mn0.7O2 is introduced, an oxygen‐redox‐based layered oxide cathode material for SIBs. The effect of Ni doping on the electrochemical performance is investigated by comparison with Ni‐free P2‐Na0.67Li0.22Mn0.78O2. The Na0.75Li0.15Ni0.15Mn0.7O2 delivers a specific capacity of ≈160 mAh g−1 in the voltage region of 1.5–4.6 V at 0.1 C in Na cells. Combined experiments (galvanostatic cycling, neutron powder diffraction, X‐ray absorption spectroscopy, X‐ray photoelectron spectroscopy, and nuclear magnetic resonance (7Li NMR)) and theoretical studies (density functional theory calculations) confirm that Ni substitution not only increases the operating voltage and decreases voltage hysteresis but also improves the cycling stability by reducing Li migration from transition metal to Na layers. This research demonstrates the effect of Li and Ni co‐doping in P2‐type layered materials and suggests a new strategy of using Mn‐rich cathode materials via oxygen redox with optimization of doping elements for SIBs.
The role of Ni substitution on the structure and electrochemical properties of oxygen‐redox‐based P2‐type Na0.67Li0.22Mn0.78O2 layered cathode materials is investigated. Ni provides not only an increase of the operating voltage and decrease of voltage hysteresis, but also improves the cycling stability by reducing Li migration from transition metal to Na layers.
Herein, the promising properties of open‐structured NaV3O8 as a cathode material for Zn‐ion batteries (ZIBs) are investigated. First‐principles calculations predict the insertion of Zn2+ (0.74 Å) in ...NaV3O8 with an interlayer distance of ≈7 Å, enabling delivery of a high discharge capacity of 353 mAh g−1 at 70 mA g−1 (0.2 C) for 300 cycles in the operating window of 0.3−1.5 V in 1 m Zn(CF3SO3)2 aqueous solution. Operando synchrotron X‐ray diffraction, X‐ray absorption near edge structure spectroscopy, and first‐principles calculations validate the insertion of Zn2+ into the NaV3O8 structure within the operation range. Moreover, operando synchrotron X‐ray diffraction and operando Raman spectroscopy reveal the formation of layered zinc hydroxytriflate (Zn5(OH)8(CF3SO3)2∙xH2O) as a side reaction below 0.8 V on discharge (reduction) and its dissolution into the electrolyte above 0.8 V on charge (oxidation). The formation of the Zn hydroxytriflate interfacial layer increases the charge‐transfer activation energy from 15.5 to 48 kJ mol−1, leading to kinetics fade below 0.8 V. The findings reveal the charge‐storage mechanism for NaV3O8, which may also be applicable to other vanadate cathodes, providing new insights for the investigation and design of ZIBs.
New insights on open‐structured NaV3O8 as a cathode for Zn‐ion storage are provided. Interfacial layer formation is explained via first‐principles calculations, operando synchrotron XRD, and operando Raman spectroscopy.
Nickel-rich layered lithium transition-metal oxides, LiNi(1-x)M(x)O(2) (M = transition metal), have been under intense investigation as high-energy cathode materials for rechargeable lithium ...batteries because of their high specific capacity and relatively low cost. However, the commercial deployment of nickel-rich oxides has been severely hindered by their intrinsic poor thermal stability at the fully charged state and insufficient cycle life, especially at elevated temperatures. Here, we report a nickel-rich lithium transition-metal oxide with a very high capacity (215 mA h g(-1)), where the nickel concentration decreases linearly whereas the manganese concentration increases linearly from the centre to the outer layer of each particle. Using this nano-functional full-gradient approach, we are able to harness the high energy density of the nickel-rich core and the high thermal stability and long life of the manganese-rich outer layers. Moreover, the micrometre-size secondary particles of this cathode material are composed of aligned needle-like nanosize primary particles, resulting in a high rate capability. The experimental results suggest that this nano-functional full-gradient cathode material is promising for applications that require high energy, long calendar life and excellent abuse tolerance such as electric vehicles.
Herein, stable cationic and anionic redox in an O3‐type layered NaNi2/3Ru1/3O2 cathode for sodium‐ion batteries (SIBs) is revealed. Density functional theory (DFT) calculation shows that the electron ...density features change in density of state with mixing of delocalized valence states as well as localized deeper energy states of O(p), Ni(d), and Ru(d) for the highly desodiated Na1−xNi2/3Ru1/3O2 electrode, revealing the covalent characteristic of the transition metal (TM)O and TMTM bonds in the charged system. These properties lead to cycling stability for 200 cycles, with ≈79% of the capacity retained at a rate of 1C (210 mA g−1). Operando X‐ray diffraction, X‐ray absorption spectroscopy, and DFT calculations reveal the reversible electrochemical activity of the Ni2+/Ni3+ and O2−/O1− redox reactions, which are sustainable throughout the cycles. In addition, no loss of oxygen from the crystal structure of NaNi2/3Ru1/3O2 occurs according to differential electrochemical mass spectrometry. The findings provide additional insight into the complex mechanism of the oxygen redox activity of high‐capacity O3‐type cathode materials for SIBs, encouraging further studies on their development.
An O3‐type layered NaNi2/3Ru1/3O2 cathode material with both cationic and anionic redox highlighted by theoretical and mechanistic properties is investigated. Ru provides partial covalent bonding in the charged system, with acceptable structural and cycling stability accompanied by Ni2+/Ni3+ and O2−/O1− redox pairs without O2 gas loss in Na cells.
EphA10 (erythropoietin‐producing hepatocellular carcinoma receptor A10) is a catalytically defective receptor protein tyrosine kinase in the ephrin receptor family. Although EphA10 is involved in the ...malignancy of some types of cancer, its role as an oncogene has not been extensively studied. Here, we investigated the influence of EphA10 on the tumorigenic potential of pancreatic cancer cells. Analysis of expression profiles from The Cancer Genome Atlas confirmed that EphA10 was elevated and higher in tumor tissues than in normal tissues in some cancer types, including pancreatic cancer. EphA10 silencing reduced the proliferation, migration, and adhesion of MIA PaCa‐2 and AsPC‐1 pancreatic cancer cells. These effects were reversed by overexpression of EphA10 in MIA PaCa‐2 cells. Importantly, overexpression and silencing of EphA10 respectively increased and decreased the weight, volume, and number of Ki‐67‐positive proliferating cells in MIA PaCa‐2 xenograft tumors. Further, EphA10 expression was positively correlated with invasion and gelatin degradation in MIA PaCa‐2 cells. Moreover, overexpression of EphA10 enhanced the expression and secretion of MMP‐9 in MIA PaCa‐2 cells and increased the expression of MMP‐9 and the vascular density in xenograft tumors. Finally, expression of EphA10 increased the phosphorylation of ERK, JNK, AKT, FAK, and NF‐κB, which are important for cell proliferation, survival, adhesion, migration, and invasion. Therefore, we suggest that EphA10 plays a pivotal role in the tumorigenesis of pancreatic epithelial cells and is a novel therapeutic target for pancreatic cancer.
The role of a catalytically defective receptor protein tyrosine kinase EphA10 for tumorigenesis has been investigated in pancreatic cancer cells. Overexpression and knockdown of EphA10 respectively increased and decreased the proliferation, migration, adhesion, and invasion of MIA PaCa‐2 and AsPC‐1 pancreatic cancer cells as well as the weight and volume of MIA PaCa‐2 xenograft tumors. Our data suggest that EphA10 plays a pivotal role in tumorigenesis of pancreatic epithelial cells and is a novel therapeutic target for pancreatic cancer.
Herein, P′2‐type Na0.67Ni0.1Fe0.1Mn0.8O2 is introduced as a promising new cathode material for sodium‐ion batteries (SIBs) that exhibits remarkable structural stability during repetitive Na+ ...de/intercalation. The ONiOMnOFeO bond in the octahedra of transition‐metal layers is used to suppress the elongation of the MnO bond and to improve the electrochemical activity, leading to the highly reversible Na storage mechanism. A high discharge capacity of ≈220 mAh g−1 (≈605 Wh kg−1) is delivered at 0.05 C (13 mAg−1) with a high reversible capacity of ≈140 mAh g−1 at 3 C and excellent capacity retention of 80% over 200 cycles. This performance is associated with the reversible P′2–OP4 phase transition and small volume change upon charge and discharge (≈3%). The nature of the sodium storage mechanism in a full cell paired with a hard carbon anode reveals an unexpectedly high energy density of ≈542 Wh kg−1 at 0.2 C and good capacity retention of ≈81% for 500 cycles at 1 C (260 mAg−1).
The study aims at achieving high operating voltage with the suppression of Jahn–Teller distortion by Mn3+ via substitution of Fe3+ and Ni2+ into the Pʹ2‐Na0.67Ni0.1Fe0.1Mn0.8O2 structure, which delivers outstanding electrochemical properties as well as long‐term cycling stability.
A high‐rate of oxygen redox assisted by cobalt in layered sodium‐based compounds is achieved. The rationally designed Na0.6Mg0.2Mn0.6Co0.2O2 exhibits outstanding electrode performance, delivering a ...discharge capacity of 214 mAh g−1 (26 mA g−1) with capacity retention of 87% after 100 cycles. High rate performance is also achieved at 7C (1.82 A g−1) with a capacity of 107 mAh g−1. Surprisingly, the Na0.6Mg0.2Mn0.6Co0.2O2 compound is able to deliver capacity for 1000 cycles at 5C (at 1.3 A g−1), retaining 72% of its initial capacity of 108 mAh g−1. X‐ray absorption spectroscopy analysis of the O K‐edge indicates the oxygen‐redox species (O2−/1−) is active during cycling. First‐principles calculations show that the addition of Co reduces the bandgap energy from ≈2.65 to ≈0.61 eV and that overlapping of the Co 3d and O 2p orbitals facilitates facile electron transfer, enabling the long‐term reversibility of the oxygen redox, even at high rates. To the best of the authors' knowledge, this is the first report on high‐rate oxygen redox in sodium‐based cathode materials, and it is believed that the findings will open a new pathway for the use of oxygen‐redox‐based materials for sodium‐ion batteries.
A new compound, P2‐Na0.6Mg0.2Mn0.8Co0.2O2, exhibits outstanding electrochemical performance assisted by high‐rate oxygen redox as well as structural stability for prolonged cycles. The electrode delivers high capacity because of the overlapping of Co 3d and O 2p orbitals. Moreover, the electrode displays excellent long‐term cycling performance, retaining 72% of its initial capacity after 1000 cycles at 5C.
We propose a feasibility of Co-free Ni-rich Li(Ni1–x Mn x )O2 layer compound. Li(Ni1–x Mn x )O2 (0.1 ≤ x ≤ 0.5) have been synthesized by a coprecipitation method. Rietveld refinement of X-ray ...diffraction and microscopic studies reveal dense and spherical secondary particles of highly crystalline phase with low cation mixing over the whole compositions, implying successful optimization of synthetic conditions. Electrochemical test results indicated that the Co-free materials delivered high capacity with excellent capacity retention and reasonable rate capability. In particular, Li(Ni0.9Mn0.1)O2, which possesses the lowest cation mixing in the Li layers among samples, exhibited exceptionally high rate capacity (approximately 149 mAh g–1 at 10 C rate) at 25 °C and high discharge capacity upon cycling under a severe condition, in the voltage range of 2.7–4.5 V at 55 °C. The cation mixing in Li(Ni0.9Mn0.1)O2 increased slightly even after the extensive cycling at the elevated temperature, which is ascribed to the structural integrity induced from the optimized synthetic condition using the coprecipitation.
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