Hydrated vanadium pentoxide (VOH) can deliver a gravimetric capacity as high as 400 mA h g −1 owing to the variable valence states of the V cation from 5+ to 3+ in an aqueous zinc ion battery. The incorporation of divalent transition metal cations has been demonstrated to overcome the structural instability, sluggish kinetics, fast capacity degradation, and serious polarization. The current study reveals that the catalytic effects of transition metal cations are probably the key to the significantly improved electrochemical properties and battery performance because of the higher covalent character of 55% in the Cu–O bond in comparison with 32% in the Mg–O bond in the respective samples. Cu( ii ) pre-inserted VOH (CuVOH) possesses a significantly enhanced intercalation storage capacity, an increased discharge voltage, great transport properties, and reduced polarization, while both VOH and Mg( ii ) pre-inserted VOH (MgVOH) demonstrate similar electrochemical properties and performances, indicating that the incorporation of Mg cations has little or no impact. For example, CuVOH has a redox voltage gap of 0.02 V, much smaller than 0.25 V for VOH and 0.27 V for MgVOH. CuVOH shows an enhanced exchange current density of 0.23 A g −1 , compared to 0.20 A g −1 for VOH and 0.19 A g −1 for MgVOH. CuVOH delivers a zinc ion storage capacity of 379 mA h g −1 , higher than 349 mA h g −1 for MgVOH and 337 mA h g −1 for VOH at 0.5 A g −1 . CuVOH shows an energy efficiency of 72%, superior to 53% for VOH and 55% for MgVOH. All of the results suggest that pre-inserted Cu( ii ) cations played a critical role in catalyzing the zinc ion intercalation reaction, while the Mg( ii ) cations did not exert a detectable catalytic effect.
more »
« less
Expanded hydrated vanadate for high-performance aqueous zinc-ion batteries
Hydrated vanadates are promising layered cathodes for aqueous zinc-ion batteries owing to their specific capacity as high as 400 mA h g −1 ; however, the structural instability causes serious cycling degradation through repeated intercalation/deintercalation reactions. This study reveals the chemically inserted Mn( ii ) cations act as structural pillars, expand the interplanar spacing, connect the adjacent layers and partially reduce pentavalent vanadium cations to tetravalent. The expanded interplanar spacing to 12.9 Å reduces electrostatic interactions, and transition metal cations collectively promote and catalyze fast and more zinc ion intercalation at higher discharge current densities with much enhanced reversibility and cycling stability. Manganese expanded hydrated vanadate (MnVO) delivers a specific capacity of 415 mA h g −1 at a current density of 50 mA g −1 and 260 mA h g −1 at 4 A g −1 with a capacity retention of 92% over 2000 cycles. The energy efficiency increases from 41% for hydrated vanadium pentoxide (VOH) to 70% for MnVO at 4 A g −1 and the open circuit voltage remains at 85% of the cutoff voltage in the MnVO battery on the shelf after 50 days. Expanded hydrated vanadate with other transition metal cations for high-performance aqueous zinc-ion batteries is also obtained, suggesting it is a general strategy for exploiting high-performance cathodes for multi-valent ion batteries.
more »
« less
- Award ID(s):
- 1803256
- NSF-PAR ID:
- 10121544
- Date Published:
- Journal Name:
- Energy & Environmental Science
- Volume:
- 12
- Issue:
- 7
- ISSN:
- 1754-5692
- Page Range / eLocation ID:
- 2273 to 2285
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
more » « less
Abstract Currently, there is considerable interest in developing advanced rechargeable batteries that boast efficient distribution of electricity and economic feasibility for use in large-scale energy storage systems. Rechargeable aqueous zinc batteries are promising alternatives to lithium-ion batteries in terms of rate performance, cost, and safety. In this investigation, we employ Cu3(HHTP)2, a two-dimensional (2D) conductive metal-organic framework (MOF) with large one-dimensional channels, as a zinc battery cathode. Owing to its unique structure, hydrated Zn2+ions which are inserted directly into the host structure, Cu3(HHTP)2, allow high diffusion rate and low interfacial resistance which enable the Cu3(HHTP)2cathode to follow the intercalation pseudocapacitance mechanism. Cu3(HHTP)2exhibits a high reversible capacity of 228 mAh g−1at 50 mA g−1. At a high current density of 4000 mA g−1(~18 C), 75.0% of the initial capacity is maintained after 500 cycles. These results provide key insights into high-performance, 2D conductive MOF designs for battery electrodes.
-
null (Ed.)Abstract Ammonium vanadate with bronze structure (NH 4 V 4 O 10 ) is a promising cathode material for zinc-ion batteries due to its high specific capacity and low cost. However, the extraction of $${\text{NH}}_{{4}}^{ + }$$ NH 4 + at a high voltage during charge/discharge processes leads to irreversible reaction and structure degradation. In this work, partial $${\text{NH}}_{{4}}^{ + }$$ NH 4 + ions were pre-removed from NH 4 V 4 O 10 through heat treatment; NH 4 V 4 O 10 nanosheets were directly grown on carbon cloth through hydrothermal method. Deficient NH 4 V 4 O 10 (denoted as NVO), with enlarged interlayer spacing, facilitated fast zinc ions transport and high storage capacity and ensured the highly reversible electrochemical reaction and the good stability of layered structure. The NVO nanosheets delivered a high specific capacity of 457 mAh g −1 at a current density of 100 mA g −1 and a capacity retention of 81% over 1000 cycles at 2 A g −1 . The initial Coulombic efficiency of NVO could reach up to 97% compared to 85% of NH 4 V 4 O 10 and maintain almost 100% during cycling, indicating the high reaction reversibility in NVO electrode.more » « less
-
more » « less
Abstract Vanadium multiredox‐based NASICON‐Na
z V2−y My (PO4)3(3 ≤z ≤ 4; M = Al3+, Cr3+, and Mn2+) cathodes are particularly attractive for Na‐ion battery applications due to their high Na insertion voltage (>3.5 V vs Na+/Na0), reversible storage capacity (≈150 mA h g−1), and rate performance. However, their practical application is hindered by rapid capacity fade due to bulk structural rearrangements at high potentials involving complex redox and local structural changes. To decouple these factors, a series of Mg2+‐substituted Na3+y V2−y Mgy (PO4)3(0 ≤y ≤ 1) cathodes is studied for which the only redox‐active species is vanadium. While X‐ray diffraction (XRD) confirms the formation of solid solutions between they = 0 and 1 end members, X‐ray absorption spectroscopy and solid‐state nuclear magnetic resonance reveal a complex evolution of the local structure upon progressive Mg2+substitution for V3+. Concurrently, the intercalation voltage rises from 3.35 to 3.45 V, due to increasingly more ionic VO bonds, and the sodium (de)intercalation mechanism transitions from a two‐phase fory ≤ 0.5 to a solid solution process fory ≥ 0.5, as confirmed by in operando XRD, while Na‐ion diffusion kinetics follow a nonlinear trend across the compositional series. -
Aqueous zinc ion batteries (ZIBs) are emerging as a highly promising alternative technology for grid-scale applications where high safety, environmental-friendliness, and high specific capacities are needed. It remains a significant challenge, however, to develop a cathode with a high rate capability and long-term cycling stability. Here, we demonstrate diffusion-controlled behavior in the intercalation of zinc ions into highly porous, Mn 4+ -rich, and low-band-gap Ni x Mn 3−x O 4 nano-particles with a carbon matrix formed in situ (with the composite denoted as Ni x Mn 3−x O 4 @C, x = 1), which exhibits superior rate capability (139.7 and 98.5 mA h g −1 at 50 and 1200 mA g −1 , respectively) and outstanding cycling stability (128.8 mA h g −1 remaining at 400 mA g −1 after 850 cycles). Based on the obtained experimental results and density functional theory (DFT) calculations, cation-site Ni substitution combined with a sufficient doping concentration can decrease the band gap and effectively improve the electronic conductivity in the crystal. Furthermore, the amorphous carbon shell and highly porous Mn 4+ -rich structure lead to fast electron transport and short Zn 2+ diffusion paths in a mild aqueous electrolyte. This study provides an example of a technique to optimize cathode materials for high-performance rechargeable ZIBs and design advanced intercalation-type materials for other energy storage devices.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/C9EE00956F
