Sodium-Vanadium Bronze Na9V14O35: An Electrode Material for Na-Ion Batteries

Na9V14O35 (η-NaxV2O5) has been synthesized via solid-state reaction in an evacuated sealed silica ampoule and tested as electroactive material for Na-ion batteries. According to powder X-ray diffraction, electron diffraction and atomic resolution scanning transmission electron microscopy, Na9V14O35 adopts a monoclinic structure consisting of layers of corner- and edge-sharing VO5 tetragonal pyramids and VO4 tetrahedra with Na cations positioned between the layers, and can be considered as sodium vanadium(IV,V) oxovanadate Na9V104.1+O19(V5+O4)4. Behavior of Na9V14O35 as a positive and negative electrode in Na half-cells was investigated by galvanostatic cycling against metallic Na, synchrotron powder X-ray diffraction and electron energy loss spectroscopy. Being charged to 4.6 V vs. Na+/Na, almost 3 Na can be extracted per Na9V14O35 formula, resulting in electrochemical capacity of ~60 mAh g−1. Upon discharge below 1 V, Na9V14O35 uptakes sodium up to Na:V = 1:1 ratio that is accompanied by drastic elongation of the separation between the layers of the VO4 tetrahedra and VO5 tetragonal pyramids and volume increase of about 31%. Below 0.25 V, the ordered layered Na9V14O35 structure transforms into a rock-salt type disordered structure and ultimately into amorphous products of a conversion reaction at 0.1 V. The discharge capacity of 490 mAh g−1 delivered at first cycle due to the conversion reaction fades with the number of charge-discharge cycles.

Complete Three-Electron Vanadium Redox in NASICON-Type Na3VSc(PO4)3 Electrode Material for Na-Ion Batteries

Here we introduce a new NASICON-type Na3VSc(PO4)3 positive electrode material for Na-ion batteries demonstrating reversible (de)intercalation of 3 Na cations per formula unit within a wide voltage range with complex voltage-composition dependence. The total electrochemical capacity of the material is 170 mAh/g, which corresponds to the complete three-electron V2+/V3+/V4+/V5+ process. All the (de)sodiation stages follow a predominantly solid-solution mechanism, as shown by operando X-ray powder diffraction. The oxidation of vanadium up to +5 upon the charge of Na3VSc(PO4)3 to 4.5 V vs. Na/Na+ causes the significant transformation of the unit cell. According to ex situ Fourier-transformed infrared spectroscopy it is accompanied by the increasing distortion of the vanadium coordination environment and shortening of the vanadium-oxygen bonds. This leads to the irreversible character of the charge-discharge curve, and the initial structure can be restored after the strong overdischarge to ≈1.5 V vs. Na/Na+.

Ultrahigh Capacity Retention of Li2ZrO3-Coated Ni-rich LNCM811 Cathode Material through Covalent Interfacial Engineering

Nickel-rich LiNiCoMnO (LNCM811) is a promising lithium-ion battery cathode material, whereas the surface-sensitive issues (i.e., side reaction and oxygen loss) occurring on LNCM811 particles significantly degrade their electrochemical capacity retentions. A uniform LiZrO coating layer can effectively mitigate the problem by preventing these issues. Instead of the normally used weak hydrogen-bonding interaction, we present a covalent interfacial engineering for the uniform LiZrO coating on LiNiCoMnO materials. Results indicate that the strong covalent interactions between citric acid and NiCoMn(OH) precursor effectively promote the adsorption of ZrO coating species on NiCoMn(OH) precursor, which is eventually converted to uniform LiZrO coating layers of about 7 nm after thermal annealing. The uniform LiZrO coating endows LNCM811 cathode materials with an exceptionally high capacity retention of 98.7% after 300 cycles at 1 C. This work shows the great potential of covalent interfacial engineering for improving the electrochemical cycling capability of Ni-rich lithium-ion battery cathode materials.

Template Orienting One-Dimensional Schiff-Base Polymer: towards Flexible Nitrogen-enriched Carbonaceous Electrodes with Ultrahigh Electrochemical Capacity

Lithium-ion capacitors (LICs) have attracted much attention considering their efficient combination of high energy density and high-power density. However, to meet the increasing requirements of energy storage devices and the...

A Review of Battery Materials as CDI Electrodes for Desalination

The world is suffering from chronic water shortage due to the increasing population, water pollution and industrialization. Desalinating saline water offers a rational choice to produce fresh water thus resolving the crisis. Among various kinds of desalination technologies, capacitive deionization (CDI) is of significant potential owing to the facile process, low energy consumption, mild working conditions, easy regeneration, low cost and the absence of secondary pollution. The electrode material is an essential component for desalination performance. The most used electrode material is carbon-based material, which suffers from low desalination capacity (under 15 mg·g−1). However, the desalination of saline water with the CDI method is usually the charging process of a battery or supercapacitor. The electrochemical capacity of battery electrode material is relatively high because of the larger scale of charge transfer due to the redox reaction, thus leading to a larger desalination capacity in the CDI system. A variety of battery materials have been developed due to the urgent demand for energy storage, which increases the choices of CDI electrode materials largely. Sodium-ion battery materials, lithium-ion battery materials, chloride-ion battery materials, conducting polymers, radical polymers, and flow battery electrode materials have appeared in the literature of CDI research, many of which enhanced the deionization performances of CDI, revealing a bright future of integrating battery materials with CDI technology.

Improved gravimetric energy density and cycle life in organic lithium-ion batteries with naphthazarin-based electrode materials

Replacing the scarce metal-based positive electrode materials currently used in rechargeable lithium ion batteries with organic compounds helps address environmental issues and might enhance gravimetric electrochemical capacity. The challenge has been to find organic materials with both high capacity and long-cycle life. Here, we study the naphthazarin (5,8-dihydroxy-1,4-naphthoquinone) skeleton as a high capacity candidate electrode for lithium-ion batteries, showing a multielectron-transfer type redox reaction. We also use electron energy-loss spectroscopy to reveal the reaction stoichiometry during charge/discharge processes. While the lithium salt of naphthazarin itself helped deliver a high initial capacity, its cycle-life was not satisfactory. Instead, a newly synthesized naphthazarin-dimer shows a lengthened cycle-life without sacrificing the initial high capacity of 416 mAh g−1 and energy density of 1.1 Wh g−1.

Influence of Crystalline and Shape Anisotropy on Electrochromic Modulation in Doped Semiconductor Nanocrystals

<p></p><p><a>Localized surface plasmon resonance (LSPR) modulation appearing in the near-infrared range in doped semiconductor nanocrystals enriches electrochromic performance. Although crystalline and shape anisotropies influence LSPR spectra, study of their impact on electrochromic modulation are lacking. Here, we study how crystalline anisotropy in hexagonal cesium-doped tungsten oxide nanorods and nanoplatelets affects essential metrics of electrochromic modulation—coloration efficiency (CE) and volumetric capacity—using different sizes of electrolyte cations (tetrabutylammonium, sodium, and lithium) as structurally sensitive electrochemical probes. Nanorod films show higher CE than nanoplatelets in all of electrolytes owing to low effective mass along the crystalline c-axis. When using sodium cations, which diffuse through one-dimensional hexagonal tunnels, electrochemical capacity is significantly greater for platelets than for nanorods. This difference is explained by the hexagonal tunnel sites being more accessible in platelets than in nanorods. Our work sheds light on the role of shape and crystalline anisotropy on charge capacity and CE both of which contribute to overall modulation. </a></p><br><p></p>

Influence of Crystalline and Shape Anisotropy on Electrochromic Modulation in Doped Semiconductor Nanocrystals

<p></p><p><a>Localized surface plasmon resonance (LSPR) modulation appearing in the near-infrared range in doped semiconductor nanocrystals enriches electrochromic performance. Although crystalline and shape anisotropies influence LSPR spectra, study of their impact on electrochromic modulation are lacking. Here, we study how crystalline anisotropy in hexagonal cesium-doped tungsten oxide nanorods and nanoplatelets affects essential metrics of electrochromic modulation—coloration efficiency (CE) and volumetric capacity—using different sizes of electrolyte cations (tetrabutylammonium, sodium, and lithium) as structurally sensitive electrochemical probes. Nanorod films show higher CE than nanoplatelets in all of electrolytes owing to low effective mass along the crystalline c-axis. When using sodium cations, which diffuse through one-dimensional hexagonal tunnels, electrochemical capacity is significantly greater for platelets than for nanorods. This difference is explained by the hexagonal tunnel sites being more accessible in platelets than in nanorods. Our work sheds light on the role of shape and crystalline anisotropy on charge capacity and CE both of which contribute to overall modulation. </a></p><br><p></p>