Aqueous Aluminum-ion Battery Research Articles

Vanadyl ethylene glycolate: A novel organic-inorganic electrode material for rechargeable aqueous aluminum-ion battery

This report illustrates an investigation on the electrochemistry of vanadyl ethylene glycolate (VEG) for rechargeable aqueous aluminum-ion battery for the first time. Vanadyl ethylene glycolate nanorods were synthesized by in-situ deposition on a carbon cloth current collector and, thereby, it makes a binder free electrode. It is found that the binder free VEG could significantly improve the electrochemical stability in comparison to pristine VEG with binder due to intimate contact of the electrode material with the current collector which resulted in reduced charge transfer resistance. The binder free electrode could deliver a stable discharge capacity of 77 mAhg−1 over 600 cycles at a high current density of 2 Ag−1, whereas pristine VEG shows negligible specific capacity. The Al3+ ion storage mechanism is also demonstrated utilizing ex-situ XPS, XRD and electron microscopy techniques.

Copper hexacyanoferrate as a long-life cathode for aqueous aluminum ion batteries

Aqueous aluminum ion batteries (AAIBs) have emerged as promising low-cost and energy-dense alternatives to conventional lithium-ion batteries. However, AAIBs exhibit a poor rate capability and limited cycle life owing to the rapid degradation. In this study, a copper hexacyanoferrate (CuHCFe) electrode was introduced into AAIBs with an aluminum trifluoromethanesulfonate aqueous electrolyte. Common aluminum electrolytes were compared to highlight the effects of anions and pure acid solutions were examined to eliminate the concerns on proton. A reversible capacity of 69.35 mAh/g was obtained at 70 mA/g, with 73% capacity maintained at 50 C, exhibiting excellent rate performance. Furthermore, the types of anions played an important role in the electrochemical performance. With triflate anions, the CuHCFe electrode exhibited remarkable cycling stability with a neglectable capacity loss in 3000 cycles (eight months of continuous testing) at 70 mA/g and 70% retention after 2300 cycles at 350 mA/g. Ex situ characterization revealed that both transition metals in CuHCFe were simultaneously involved in the redox reaction with minimal lattice change upon ion insertion/extraction. The results demonstrate the compatibility and potential of CuHCFe cathodes and aluminum triflate electrolytes for AAIBs, which can promote the development of such batteries for electrochemical energy storage.

A high-performance Cu–Al dual-ion battery realized by high-concentration Cl− electrolyte and CuS cathode

We propose a new Cu–Al dual-ion battery that aqueous solution composed of LiCl, CuCl and AlCl3 (LiCuAl) is used as the electrolyte, CuS is used as the cathode of aqueous aluminum ion battery for the first time and copper foil is used as the anode. The assembled Cu–Al dual-ion battery yields a reversible capacity of 538 mA h/g at 200 mA/g, and exhibits longterm cycling stability of over 200 cycles with 88.6% capacity retention at 1000 mA/g. Above excellent performance is inseparable from the three components of LiCuAl electrolyte and electrode materials. The Al-storage mechanism of CuS is proposed that the S–S bond in CuS lattice interacts with aluminum ions during the aluminum storage process. In addition, the charging and discharging process does not cause irreversible damage to the S–S bond, thus Cu–Al dual-ion battery with CuS as cathode shows great cycle stability.

Bimetallic Rechargeable Al/Zn Hybrid Aqueous Batteries Based on Al-Zn Alloys with Composite Electrolytes.

Aluminum is abundant and exhibits a high theoretical capacity and volumetric energy density. Additionally, the high safety of aqueous aluminum-ion batteries makes them strong candidates for large-scale energystorage systems. However, the frequent collapse of the cathode material and passive oxide film results in the difficult development of aqueous aluminum-ion batteries. This work provides a novel battery system, namely, Al-Zn/Al(OTF)3 +HOTF+Zn(OTF)2 /Alx Zny MnO2 ·nH2 O, with a mixed electrolyte. The cathode applies MnO topology transformation to ensure that the cathode forms Alx MnO2 ·nH2 O. Topology transformation alters the structure of the cathode material so that Zn2+ can be intercalated into the Alx MnO2 ·nH2 O spinel structure to provide support for the material structure. Regarding the anode, Zn2+ in the electrolyte is deposited onto Al of the anode to produce a regional Al-Zn alloy. Zn2+ is reduced to Zn metal during discharging, which adds a platform for secondary discharge beneficial for battery capacity enhancement. This system can provide a 1.6V discharge platform, while the first cycle discharge can reach 554 mAhg-1 , thereby maintaining a high capacity of 313 mAhg-1 after 100 cycles. This study provides a new idea for the further development of aqueous aluminum-ion batteries (AAIBs).

Rechargeable Aqueous Aluminum-Ion Battery: Progress and Outlook.

The high cost and scarcity of lithium resources have prompted researchers to seek alternatives to lithium-ion batteries. Among emerging "Beyond Lithium" batteries, rechargeable aluminum-ion batteries (AIBs) are yet another attractive electrochemical storage device due to their high specific capacity and the abundance of aluminum. Although the current electrochemical performance of nonaqueous AIBs is better than aqueous AIBs (AAIBs), AAIBs have recently gained attention due to their low cost and enhanced safety. Extensive efforts are devoted to developing AAIBs in the last few years. Yet, it is still challenging to achieve stable electrodes with good electrochemical performance and electrolytes without side reactions. This review summarizes the recent progress in the exploration of anode and cathode materials and the selection of electrolytes of AAIBs. Lastly, the main challenges and future research outlook of high-performance AAIBs are also presented.

Optimization of Electrolytes for High-Performance Aqueous Aluminum-Ion Batteries.

Aqueous rechargeable batteries based on aluminum chemistry have become the focus of immense research interest owing to their earth abundance, low cost, and the higher theoretical volumetric energy density of this element compared to lithium-ion batteries. Efforts to harness this huge potential have been hindered by the narrow potential window of water and by passivating effects of the high-electrical band-gap aluminum oxide film. Herein, we report a high-performing aqueous aluminum-ion battery (AIB), which is constructed using a Zn-supported Al alloy, an aluminum bis(trifluoromethanesulfonyl)imide (Al[TFSI]3) electrolyte, and a MnO2 cathode. The use of Al[TFSI]3 significantly extends the voltage window of the electrolyte and enables the cell to access Al3+/Al electrochemistry, while the use of Zn–Al alloy mitigates the issue of surface passivation. The Zn–Al alloy, which is produced by in situ electrochemical deposition, obtained from Al[TFSI]3 showed excellent long-term reversibility for Al electrochemistry and displays the highest performance in AIB when compared to the response obtained in Al2(SO4)3 or aluminum trifluoromethanesulfonate electrolyte. AIB cells constructed using the Zn–Al|Al[TFSI]3|MnO2 combination achieved a record discharge voltage plateau of 1.75 V and a specific capacity of 450 mAh g–1 without significant capacity fade after 400 cycles. These findings will promote the development of energy-dense aqueous AIBs.

Predominant intercalation of H+ enables ultrahigh rate capability of oxygen deficient MoO3 for aqueous Al-ion batteries

Establishing conclusive proof of ion intercalation/deintercalation is challenging and critical to accurately assessing and optimizing the performance of aqueous aluminum-ion batteries (AAIBs). In this article, we develop oxygen-deficient α-MoO3 (denoted OD-MoO3-x) with an ultrahigh rate capability (97 mA h g−1 at 50 A g−1) for AAIBs. The fast kinetics of charge storage are not only due to interlayer expansion but also related to the charge storage mechanism. Through DFT calculations, in situ XRD, in situ Raman spectroscopy, in situ pH monitoring, ex situ TEM and ToF-SIMS, we identify and quantify the contribution of H+ intercalation to the total energy storage. The mechanism of the ultrahigh rate capability of OD-MoO3-x is established as the predominant H+ intercalation. Our study may shed some light on the electrode development of high-performance multivalent-ion batteries.

Bi-functional poly(vinylidene difluoride) coated Al anodes for highly rechargeable aqueous Al-ion batteries

Aqueous rechargeable aluminum (Al) ion batteries have attracted much attention due to the high abundance of Al metal and high volumetric energy density (8040 mAh cm−3). However, Al anode suffers from hydrogen evolution side reactions in aqueous electrolyte due to its low equilibrium redox potential. Here, we developed a poly(vinylidene difluoride) (PVDF) coating that can inhibit free H2O/O2 and alleviate the corrosion problem. Theoretical calculations verify that PVDF and Al3+ have a strong interaction through the F-Al bond towards the observed uniform Al deposition. As a result, the cell of PVDF-Al/K2CoFe(CN)6 achieved 98.2% Coulombic efficiency after 400 cycles at a current density of 100 mA g−1. This work presents an effective and facile strategy to the development of high-performance and low-cost aqueous Al-ion batteries.

Oxygen vacancies-modulated tungsten oxide anode for ultra-stable and fast aqueous aluminum-ion storage

Rechargeable aqueous aluminum-ion battery (RAAB) is a potential candidate for safe and cost-effective energy storage device. Although tungsten oxide is a promising intercalation anode material to accommodate various metallic charge carriers, its main bottlenecks of application are the low conductivity and sluggish redox kinetics. Herein, a novel W18O49 anode with rich oxygen vacancies (denoted as W18O49-Ov) has been proposed for RAABs. According to the theoretical calculations and experimental results, we found the important role of oxygen vacancies in modulating electronic state and bandgap as well as offering abundant active sites for Al3+ diffusion within the W18O49-Ov anode. Moreover, a 3D robust architecture of W18O49-Ov anode is effectively constructed with excellent structural stability. In-situ Raman investigation further reveals the electrochemical mechanism of W18O49-Ov anode with reversible phase transition about redox reaction between W5+/W6+ states upon Al3+ insertion-extraction. These properties endow the superior aqueous Al3+ storage (∼251.3 mAh g−1), rapid charge-discharge response, and high electrochemical reversibility for W18O49-Ov anode. For real-life applications, a high-performance Al-metal free RAAB is assembled with a long-term cycle performance (∼95.3 % capacity retention after 5000 cycles), and this is the best value in RAABs reported so far, further suggesting its great potential in energy-related electronic fields.

Microrods synthesized of MoO3 with corn straw as biological templates and its electrochemical performance in aqueous aluminum-ion battery

ABSTRACT. In this paper, MoO3 microrods were prepared using corn straw as biological template via roasting process The components and crystal characterization of the material were investigated via X-ray diffraction (XRD)，scanning electron microscopy (SEM), and the electrochemistry property and mechanism were studied. The results showed that the MoO3 material synthesized by template method is orthorhombic structures. The MoO3 particles were submicron and micron rods with uniform distribution and a smooth surface. MoO3 microrods had an average diameter that ranged from 1 to 2 μm. The result indicated that the MoO3 as the new negative of aluminum battery delivers a higher discharge capacity of 190 mA·h·g-1 at a scanning rate of 1 mV·s-1, which showing good capacity and cycling performance.
 
 KEY WORDS: Biological template, Corn straw, Aqueous aluminum-ion battery, MoO3
 
 Bull. Chem. Soc. Ethiop. 2021, 35(3), 669-675.
 DOI: https://dx.doi.org/10.4314/bcse.v35i3.17

LiV3O8 as an intercalation-type cathode for aqueous aluminum-ion batteries

Understanding the intercalation process of Al3+ ions in the layered type LiV3O8 cathode for aqueous aluminum ion batteries.

Investigating intercalation mechanism of manganese oxide electrode in aqueous aluminum electrolyte

Aqueous aluminum-ion batteries (AAIBs) are promising candidates for next-generation energy storage devices that are safe, cost effective, and environmentally benign. Among all electrode materials reported in AAIBs, transitional metal oxide-based electrodes are of particular interest. Although superior electrochemical performance had been achieved, the underlying charge storage mechanism involved remains equivocal. In this work, the electrochemical behavior and charge storage mechanism of alpha oxide dioxide (α-MnO2) electrode in aqueous aluminum trifluoromethanesulfonate (Al(OTF)3) electrolyte are comprehensively investigated through various electrochemical testing and extensive spectroscopic characterizations, and an alternative reaction mechanism is proposed. We observe that H3O+ intercalation/de-intercalation contributes to the reversible capacity over cycles, while only a small amount of Al3+ could intercalate into α-MnO2. The composition of the complex formed during discharge is proposed, which may contain Al3+, OH−, and OTF−. This surface complex would dissolve after charge. Lastly, recommendations are made on prospective electrode and electrolyte design using the insights obtained from this study. Understanding the charge storage mechanism is crucial for designing appropriate electrode materials and electrolytes and we expect that our findings will shed light on achieving high-performance aluminum-based energy storage devices.

Novel K2Ti8O17 Anode via Na+/Al3+ Co-Intercalation Mechanism for Rechargeable Aqueous Al-Ion Battery with Superior Rate Capability.

A promising aqueous aluminum ion battery (AIB) was assembled using a novel layered K2Ti8O17 anode against an activated carbon coated on a Ti mesh cathode in an AlCl3-based aqueous electrolyte. The intercalation/deintercalation mechanism endowed the layered K2Ti8O17 as a promising anode for rechargeable aqueous AIBs. NaAc was introduced into the AlCl3 aqueous electrolyte to enhance the cycling stability of the assembled aqueous AIB. The as-designed AIB displayed a high discharge voltage near 1.6 V, and a discharge capacity of up to 189.6 mAh g−1. The assembled AIB lit up a commercial light-emitting diode (LED) lasting more than one hour. Inductively coupled plasma–optical emission spectroscopy (ICP-OES), high-resolution transmission electron microscopy (HRTEM), and X-ray absorption near-edge spectroscopy (XANES) were employed to investigate the intercalation/deintercalation mechanism of Na+/Al3+ ions in the aqueous AIB. The results indicated that the layered structure facilitated the intercalation/deintercalation of Na+/Al3+ ions, thus providing a high-rate performance of the K2Ti8O17 anode. The diffusion-controlled electrochemical characteristics and the reduction of Ti4+ species during the discharge process illustrated the intercalation/deintercalation mechanism of the K2Ti8O17 anode. This study provides not only insight into the charge–discharge mechanism of the K2Ti8O17 anode but also a novel strategy to design rechargeable aqueous AIBs.

High-Rate Aqueous Aluminum-Ion Batteries Enabled by Confined Iodine Conversion Chemistry.

Most reported cathode materials for rechargeable aqueous Al metal batteries are based on an intercalative-type chemistry mechanism. Herein, iodine embedded in MOF-derived N-doped microporous carbon polyhedrons (I2 @ZIF-8-C) is proposed to be a conversion-type cathode material for aqueous aluminum-ion batteries based on "water-in-salt" electrolytes. Compared with the conventional Al-I2 battery using ionic liquid electrolyte, the proposed aqueous Al-I2 battery delivers much enhanced electrochemical performance in terms of specific capacity and voltage plateaus. Benefitting from the confined liquid-solid conversion of iodine in hierarchical N-doped microporous carbon polyhedrons and enhanced reaction kinetics of aqueous electrolytes, the I2 @ZIF-8-C electrode delivers high reversibility, superior specific capacity (≈219.8 mAh g-1 at 2 A g-1 ), and high rate performance (≈102.6 mAh g-1 at 8 A g-1 ). The reversible reaction between I2 and I- , with I3 - and I5 - as intermediates, is confirmed via ex situ Raman spectra and X-ray photoelectron spectroscopy. Furthermore, solid-state hydrogel electrolyte is employed to fabricate a flexible Al-I2 battery, which shows performance comparable to batteries using liquid electrolyte and can be integrated to power wearable devices as a reliable energy supply.

Suppressing passivation layer of Al anode in aqueous electrolytes by complexation of H2PO4− to Al3+ and an electrochromic Al ion battery

Aqueous aluminum ion batteries (AIBs) are attractive alternatives for post-lithium energy storage systems. However, the short lifespan seriously limits the development of AIBs, arising from the formation of a passivation layer on the Al electrode surface as well as the strong electrostatic interaction between bulky Al3+ ions and host materials. Herein, we developed a hybrid electrolyte based on aluminum trifluoromethanesulphonate (Al(TOF)3) and H3PO4 which can effectively alleviate the passivation and exhibit superior stability. A full aqueous AIB based on this electrolyte and polyaniline (PANI) cathode exhibits a record-breaking lifespan of 3850 cycles and superior rate capability. Mechanism study suggests that Al3+ ions are bonded to both the H2PO4− and TOF− to form complex ions Al(H2PO4−)x(TOF−)y+(H2O)n, which can mitigate the strong charge densities of trivalent Al3+ and contribute to fast reaction kinetics. Besides, the ex-situ study reveals that PANI cathode experiences a co-intercalation/deintercalation process of Al(H2PO4−)x(TOF−)y+(H2O)n, TOF−, and H+ during the charging/discharging process with high reversibility and stability. As a proof of concept, an electrochromic Al//PANI battery is fabricated, which combines both electrochromism and energy storage and delivers a higher coloration efficiency of 84 cm2C−1 at a wavelength of 630 nm. This work presents an effective and facile strategy to developing long-life aqueous Al//PANI batteries and may promote the application of AIBs with electrochromic function.

Reversible aluminum ion storage mechanism in Ti-deficient rutile titanium dioxide anode for aqueous aluminum-ion batteries

Aqueous aluminum-ion batteries (AIBs) are potential candidates for future large-scale energy storage devices owing to their advantages of high energy density, resource abundance, low cost, and environmental friendliness. However, the exploration of suitable electrode materials is one of the key challenges for the development of aqueous AIBs. To address this issue, a new Ti-deficient rutile titanium dioxide (Ti0.95□0.05O1.79Cl0.08(OH)0.13) was achieved via univalent ion doping and evaluated as an anode for aqueous AIBs. This material yields a reversible capacity of 143.1 mA h g−1 at 0.5 A g−1. Even at 3 A g−1, an initial reversible charge capacity of 78.3 mA h g−1 can be achieved and retains almost 82% after 110 cycles. The Al3+ ion storage mechanism has been intensively investigated by ex-situ XRD, XPS, SEM, TEM and Raman techniques, indicating that Al3+ ions can reversibly insert into Ti vacancies and lattice of the Ti0.95□0.05O1.79Cl0.08(OH)0.13 without phase change, leading to much enhanced capacity as compared to the commercial rutile TiO2. These results demonstrate that cationic defect engineering is an effective strategy to improve the electrochemical properties of electrode materials for aqueous AIBs.

9,10-Anthraquinone/K2CuFe(CN)6: A Highly Compatible Aqueous Aluminum-Ion Full-Battery Configuration

Temporally intermittent and spatially dispersed renewable energy sources strongly call for large-scale energy storage devices. Aqueous aluminum-ion batteries show great potential for application due to their safety and low cost. Thus far, however, the ideal full-battery configuration is beyond the scope due to shortcomings with regards to suitable anode and cathode materials. Herein, we report a pioneering aqueous aluminum-ion battery system consisting of a Prussian white cathode, 1 M Al2(SO4)3 aqueous electrolyte, and an organic 9,10-anthraquinone anode. The oxidation capability of the Prussian white cathode during the first charging allows for the fabrication of the full battery without pre-inserting aluminum ions, thus making the rocking-chair-type battery feasible. Importantly, the open-framework structure of the Prussian white and distinct enolization charge storage mechanism of 9,10-anthraquinone ensure fast reaction kinetics. The full battery exhibits cycling stability with a capacity retention of 89.1% over 100 cycles at 500 mA g-1, finishing a cycle in about 10 min. This work provides a pathway for developing rechargeable aqueous aluminum-ion batteries.

Rechargeable Aqueous Aluminum Organic Batteries.

Aqueous aluminum-ion batteries (AABs) are regarded as promising next-generation energy storage devices, and the current reported cathodes for AABs mainly focused on inorganic materials which usually implement a typical Al3+ ions (de)insertion mechanism. However, the strong electrostatic forces between Al3+ and the host materials usually lead to sluggish kinetics, poor reversibility and inferior cycling stability. Herein, we employ an organic compound with redox-active moieties, phenazine (PZ), as the cathode material in AABs. Different from conventional inorganic materials confined by limited lattice spacing and rigid structure, the flexible organic molecules allow a large-size Al-complex co-intercalation through reversible redox active centers (-C=N-) of PZ. This co-intercalation behavior can effectively reduce desolvation penalty, and substantially lower the Coulombic repulsion during the ion (de)insertion process. Consequently, this organic cathode exhibits a high capacity and excellent cyclability, which exceeds those of most reported electrode materials for AABs. This work highlights the anion co-intercalation chemistry of redox-active organic materials, which is expected to boost the development of high-performance multivalent-ion battery systems.

“Water-in-Salt” Electrolyte Promises Reversible Anion Intercalation into Graphite for Energy Storage Applications

Electrochemical energy storage systems (EESS) with high energy density, safety, low cost, and low carbon footprint have become indispensable in the modern era of ubiquitous electronics, electric vehicles, and grid storage. Current EESS lack of these characteristics due to the utilization of critical materials which are precious, flammable and difficult to recycle. Whereas, aqueous electrolytes offer higher safety and lower costs. Nevertheless, their biggest bottleneck is the narrow electrochemical window (1.23V) that is preventing from attaining higher energy and power densities in most of the aqueous EESS. For instance, aqueous rechargeable aluminum ion batteries promise high energy density due to multivalent redox chemistry of aluminum ion (Al3+) but they exhibit much lower energy density in real experiments due to the limited electrochemical windows of the aqueous electrolytes. The water-in-salt based electrolytes (WiSE) can potentially eliminate this barrier by offering a larger electrochemical window by reducing the overall electrochemical activity of water on the electrodes. Here, we demonstrate a new concept using aluminum perchlorate based WiSE that is showing a stable and wide electrochemical window of nearly 4 V against Ag/AgCl. The electrochemistry tests of the electrolyte are performed using carbon-based redox-active electrode materials. We employ the new electrochemical system in aqueous rechargeable aluminum ion batteries, revealing superior performance to standard aqueous electrolytes. Our findings provide new possibilities for widening the electrochemical window and enhancing the energy and power density in aqueous EESS.

Preparation of organic poly material as anode in aqueous aluminum-ion battery

Rechargeable aqueous aluminum ion batteries (RAAB) have gained increasing attentions for large scale energy storage system due to their high safety, nontoxicity and low cost. However, lack of capable anode materials extremely hinders their potential application. As we all know, the anodic material of aluminum ion battery was limited, we report poly (3,4,9,10-perylentetracarboxylic diimide) (PPTCDI) under the different synthesis conditions as organic anode material for aqueous RAAB. The aluminum ions intercalation/deintercalation storage mechanism is affected by the different electrolyte concentrations. Upon their high capacity and cycling stability, our work would highlight potential application of conjugated polymer organic electrode materials for aqueous aluminum ion batteries.