Water‐Stabilized Vanadyl Phosphate Monohydrate Ultrathin Nanosheets toward High Voltage Al‐Ion Batteries

Abstract

storage system, which would propel the substantial development of the energy storage technology. [4] In order to design high energy density storage devices, the identifying of host materials with high performance, especially elevated work potential, is essential. Due to the high electronegativity of oxygen, the metal oxides own strong ionic chemical bonds, which consequently result in increased plateau voltages. [5] Examples of such oxides owning potential high discharge voltages are amorphous V 2 O 5 (≈0.9 V), [6] MoO 2 (1.9 V), [7] TiO 2 (≈1.0 V) [8] and so on. Despite their advantage in working potential, they usually suffer from low capacity, discontented cycling life, and inferior rate capability, which originate from the slow reaction kinetics caused by the strong Coulombic interaction between the trivalent Al 3+ and oxide host lattice. [9] Previous researches have demonstrated that water molecules can be applied as "lubricant" to facilitate ions diffusion. [10] Typically, vanadyl phosphate dihydrate (VOPO 4 •2H 2 O) with a long intercalation chemistry history, has been recently developed as a potential cathode material for various alkali metalion batteries, meriting from its high redox reaction potential due to the strong inductive effect of [PO 4 ] tetrahedrons and the large interlayer space stemming from the interlayer water molecules. [11] Moreover, the easier multivalent ions (Mg 2+ and Zn 2+ ) intercalation into VOPO 4 •2H 2 O can take place with the aid of the water molecules. [11e,12] The study of vanadyl phosphate hydrate as AIBs cathode was first reported in 2020 by Wang and co-workers via fabricating a VOPO 4 -graphene heterostructure. [11f ] Although an improved cycling performance originating from its zero-strain property is achieved, the potential high discharge plateau voltage and capacity of vanadyl phosphate hydrate are underutilized. In addition, the effect and mechanism of the bonded water molecule content and its stability on the aluminum storage behavior have not been systematically studied.In this work, we select VOPO 4 •2H 2 O as a model cathode to reveal its Al 3+ storage behaviors. As expected, the VOPO 4 •2H 2 O presents high discharge plateau and holds high potential Al 3+ storage capacity. We further investigate the relationship between water content and electrochemical performance. Interestingly, our density functional theory (DFT) calculations results reveal that, compared with VOPO 4 •2H 2 O and VOPO 4 , the VOPO 4 •H 2 O possesses the lowest Al 3+ diffusion barrier and Al ion batteries (AIBs) are attracting considerable attention owing to high volumetric capacity, low cost, and high safety. However, the strong electrostatic interaction between Al 3+ and host lattice leads to discontented cycling life and inferior rate capability. Herein, a new strategy of employing water molecules contained VOPO 4 •H 2 O to boost Al 3+ migration via the charge shielding effect of water is reported. It is revealed that VOPO 4 •H 2 O with water lubrication effect and smaller steric hindrance ...

A B-doped layered VOPO4·2H2O cathode for high-performance zinc-ion batteries with an H+/Zn2+ co-insertion mechanism

“…20 The diffraction peaks of typical layered structures were successfully detected, which is seen from the diffraction angles at 11.89 and 23.94, corresponding to the (001) and (002) peaks, respectively. 21 Interestingly, a slight shift of the peaks can be obviously observed when compared with those of VOPO 4 ·2H 2 O, which indicates that B has been doped into the layered structure. The XRD pattern of the local amplified area is displayed in Fig.…”

Advanced V-based materials for multivalent-ion storage applications

“…Mott-Schottky (impedance potential) measurements also showed that the electronic conductivity was greatly improved due to high concentration of O vacancies, which increases the carrier concentration by about 57 times [Figure 11B]. As a result of these unique characteristics, the specific capacity was 313.6 mAh g -1 at 0.1 A g -1 , and the retention was 76.8% after 500 cycles at 5.0 A g -1 [61] . Intercalation of aniline significantly increased the hydrophobicity of VOPO 4 •2H 2 O cathode, thus inhibiting dissolution.…”

“…VOPO 4 displays a typical layered crystal structure with vertexsharing VO 6 octahedra and PO 4 tetrahedra in a 1:1 ratio [Figure 3F] [60] . Hydrothermal synthesized VOPO 4 tends to form the hydrate VOPO 4 •nH 2 O, which easily decomposes into VO x during cycling, so the cycling performance is poor [61] . The 3D framework of Na 3 V 2 (PO 4 ) 3 cathode consists of strongly bonded tetrahedral [PO 4 ] and octahedral [VO 6 ] units with large gaps, favoring fast ion transport.…”

“…However, they also faced various issues. VOPO 4 •nH 2 O dissolves easily in aqueous solution, leading to poor cycling performance [61] . Concentrated ZnCl 2 electrolyte was reported to prevent the dissolution of VOPO 4 •2H 2 O and protect Zn metal from hydrogen evolution reactions and dendrites [162,163] .…”

Adjustable MXene‐Based Materials in Metal‐Ion Batteries: Progress, Prospects, and Challenges

“…In this review, we focus on the fabrication and applications of MXenes, MXene‐based, and MXene‐derived materials in different MIBs, from classical LIBs to novel SIBs, PIBs, MgIBs, and AIBs, in particular concerning their roles in electrochemical reactions. [ 30 ] Initially, a brief introduction and overview of the properties of MXenes are presented. Then highlight the recent progress by using MXene‐based materials for different MIBs.…”