Rechargeable Aluminum-Ion Batteries Based on an Open-Tunnel Framework

Research Advances of Cathode Materials for Rechargeable Aluminum Batteries

Rechargeable aluminum ion batteries (AIBs) have recently gained widespread research concern as energy storage technologies because of their advantages of being safe, economical, environmentally friendly, sustainable, and displaying high performance. Nevertheless, the intense Coulombic interactions between the Al3+ ions with high charge density and the lattice of the electrode body lead to poor cathode kinetics and limited cycle life in AIBs. This paper reviews the recent advances in the cathode design of AIBs to gain a comprehensive understanding of the opportunities and challenges presented by current AIBs. In addition, the advantages, limitations, and possible solutions of each cathode material are discussed. Finally, the future development prospect of the cathode materials is presented.

Rechargeable Batteries for Grid Scale Energy Storage

Ever-increasing global energy consumption has driven the development of renewable energy technologies to reduce greenhouse gas emissions and air pollution. Battery energy storage systems (BESS) with high electrochemical performance are critical for enabling renewable yet intermittent sources of energy such as solar and wind. In recent years, numerous new battery technologies have been achieved and showed great potential for grid scale energy storage (GSES) applications. However, their practical applications have been greatly impeded due to the gap between the breakthroughs achieved in research laboratories and the industrial applications. In addition, various complex applications call for different battery performances. Matching of diverse batteries to various applications is required to promote practical energy storage research achievement. This review provides in-depth discussion and comprehensive consideration in the battery research field for GSES. The overall requirements of battery technologies for practical applications with key parameters are systematically analyzed by generating standards and measures for GSES. We also discuss recent progress and existing challenges for some representative battery technologies with great promise for GSES, including metal-ion batteries, lead-acid batteries, molten-salt batteries, alkaline batteries, redox-flow batteries, metal-air batteries, and hydrogen-gas batteries. Moreover, we emphasize the importance of bringing emerging battery technologies from academia to industry. Our perspectives on the future development of batteries for GSES applications are provided.

Novel One-Dimensional Nanofiber MnSe/CMK-3 High-Performance Cathode Material for Aluminum Batteries

Transition metal selenides have shown outstanding performance as cathode materials for aluminum-ion batteries and have thus become a popular choice for cathode materials. Herein, Mn-based carbon fibers (Mn/CNFs) were first synthesized by electrospinning as a precursor, and then MnSe composites were prepared by a melt-diffusion method. However, due to polyselenides and selenides being generated during electrochemical reactions, the cycling stability of MnSe cathode materials is poor. After 200 cycles, the discharge specific capacity is only 176 mA h/g. To suppress the shuttle effect of selenides and polyselenides, a CMK-3-modified separator was used instead of a glass fiber separator. Compared with MnSe-800, the replaced MnSe-800/CMK-3 has a great capacity improvement; the initial discharge specific capacity is 1029.85 mA h/g, which after 3000 cycles, still remains at 297.84 mA h/g. The soft pack battery can still light up the LED normally under different degrees of folding, which proves the application of this material in wearable devices. This work provides a new way to improve the performance of transition metal selenides.

Reversible and rapid calcium intercalation into molybdenum vanadium oxides

Looming concerns regarding scarcity, high prices, and safety threaten the long-term use of lithium in energy storage devices. Calcium has been explored in batteries because of its abundance and low cost, but the larger size and higher charge density of calcium ions relative to lithium impairs diffusion kinetics and cyclic stability. In this work, an aqueous calcium-ion battery is demonstrated using orthorhombic, trigonal, and tetragonal polymorphs of molybdenum vanadium oxide (MoVO) as a host for calcium ions. Orthorhombic and trigonal MoVOs outperform the tetragonal structure because large hexagonal and heptagonal tunnels are ubiquitous in such crystals, providing facile pathways for calcium-ion diffusion. For trigonal MoVO, a specific capacity of ∼203 mAh g^-1 was obtained at 0.2C and at a 100 times faster rate of 20C, an ∼60 mAh g^-1 capacity was achieved. The open-tunnel trigonal and orthorhombic polymorphs also promoted cyclic stability and reversibility. A review of the literature indicates that MoVO provides one of the best performances reported to date for the storage of calcium ions.

Challenges and Strategies of Low-Cost Aluminum Anodes for High-Performance Al-Based Batteries

The ever-growing market of electric vehicles and the upcoming grid-scale storage systems have stimulated the fast growth of renewable energy storage technologies. Aluminum-based batteries are considered one of the most promising alternatives to complement or possibly replace the current lithium-ion batteries owing to their high specific capacity, good safety, low cost, light weight, and abundant reserves of Al. However, the anode problems in primary and secondary Al batteries, such as, self-corrosion, passive film, and volume expansion, severely limit the batteries' practical performance, thus hindering their commercialization. Herein, an overview of the currently emerged Al-based batteries is provided, that primarily focus on the recent research progress for Al anodes in both primary and rechargeable systems. The anode reaction mechanisms and problems in various Al-based batteries are discussed, and various strategies to overcome the challenges of Al anodes, including surface oxidation, self-corrosion, volume expansion, and dendrite growth, are systematically summarized. Finally, future research perspectives toward advanced Al batteries with higher performance and better safety are presented.

Metal-ion batteries for electric vehicles: current state of the technology, issues and future perspectives

The batteries based on metals-ions have the potential to meet the future needs of electric vehicle (EV) applications. This article reviews the key technological developments and scientific challenges of a broad range of Li-ion, Mg-ion and Al-ion batteries for electric vehicles. The fundamental configurations and corresponding reaction mechanisms of metal-ion strategies are tangibly discussed in this review article. After a brief revision of the fundamentals, the performance is analysed among Li-ion, Mg-ion and Al-ion battery technologies. The key parameters for the present compilation are the abundance, the volumetric capacity, the gravimetric capacity, the cycling life, cost and safety. Further, it summarizes the recycling methodologies, strengths and limitations of these batteries. Finally, future directions of all these batteries are highlighted and discussed.

Tetradiketone macrocycle for divalent aluminium ion batteries

Contrary to early motivation, the majority of aluminium ion batteries developed to date do not utilise multivalent ion storage; rather, these batteries rely on monovalent complex ions for their main redox reaction. This limitation is somewhat frustrating because the innate advantages of metallic aluminium such as its low cost and high air stability cannot be fully taken advantage of. Here, we report a tetradiketone macrocycle as an aluminium ion battery cathode material that reversibly reacts with divalent (AlCl²⁺) ions and consequently achieves a high specific capacity of 350 mAh g⁻¹ along with a lifetime of 8000 cycles. The preferred storage of divalent ions over their competing monovalent counterparts can be explained by the relatively unstable discharge state when using monovalent AlCl₂⁺ ions, which exert a moderate resonance effect to stabilise the structure. This study opens an avenue to realise truly multivalent aluminium ion batteries based on organic active materials, by tuning the relative stability of discharged states with carrier ions of different valence states.

Aluminium ion batteries have been developed based on the storage of monovalent complex ions, impairing their original motivation of storing multivalent ions. Here, the authors demonstrate the divalent ion storage of tetradiketone macrocycles by tuning the relative stability of discharged states.

Controlled growth and ion intercalation mechanism of monocrystalline niobium pentoxide nanotubes for advanced rechargeable aluminum-ion batteries

Rechargeable aluminum-ion batteries (RAIBs) have attracted increasing attention owing to their high theoretical volumetric capacity, high resource abundance, and good safety performance. However, the existing RAIB systems usually exhibit relatively low specific capacities limited by the cathode materials. In this study, we developed a one-step chemical vapor deposition method to prepare single-crystal orthogonal Nb2O5 nanotubes for serving as high-performance electrode materials for RAIBs, showing a high reversible capability of 556 mA h g-1 at 25 mA g-1 and good thermal endurability at elevated temperatures (50 °C). A combination of a series of detailed ex situ structural characterization studies verified the reversible intercalation/deintercalation of chloroaluminate anions (AlCl4-) into/from the (001) planes of monocrystalline Nb2O5 nanotubes. It also revealed that the nanoarchitecture of Nb2O5 nanotubes with thin tube walls, hollow inner space and a short ion transport distance is conducive to the rapid kinetics of the insertion/extraction process. This work provides a promising route to design high-performance electrode materials based on transition metal compounds for RAIBs via the rational modulation of their structure and morphology.

Novel One-Dimensional Hollow Carbon Nanotubes/Selenium Composite for High-Performance Al-Se Batteries

Herein, we successfully prepared one-dimensional nanowire with carbon-coated selenium (Se@CW) by using a simple wet chemical method and obtained a one-dimensional hollow Se@C nanotube (Se@CT) after the subsequent calcination treatment. We have formed a new Al-Se secondary battery by using Se@CT as the cathode and metal aluminum as the anode in the AlCl₃/[EMIm]Cl electrolyte. It is believed that the oxidation intermediate of Se in Al-Se batteries may not only have Se₂²⁺, but there may be other oxidation intermediates, such as Se⁴⁺, Se²⁺, and Se₈²⁺. Therefore, Se@CT exhibits excellent charge-discharge performance in Al-Se batteries. Its initial discharge capacity reaches 447.2 mA h g^-1 at 200 mA g^-1, and the operating voltage is above 1.6 V. Its energy density approaches 708.8 W h k g^-1, the capacity is still 162.9 mA h g^-1 after 200 cycles at 500 mA g^-1, and the corresponding capacity retention rate is up to 83.5%. In addition, its electrochemical performance is far superior to that of Se@CMK-3 in Al-Se batteries and the electrochemical properties of carbon materials, oxides, and sulfide electrode materials in some aluminum-ion batteries, which will open up a new direction for the development of new secondary aluminum-based batteries.

The Rechargeable Aluminum Battery: Opportunities and Challenges

Aluminum battery systems are considered as a system that could supplement current lithium batteries due to the low cost and high volumetric capacity of aluminum metal, and the high safety of the whole battery system. However, first the use of ionic liquid electrolytes leading to AlCl₄ ^- instead of Al³⁺ , the different intercalation reagents, the sluggish solid diffusion process and the fast capacity fading during cycling in aluminum batteries all need to be thoroughly explored. To provide a good understanding of the opportunities and challenges of the newly emerging aluminum batteries, this Review discusses the reaction mechanisms and the difficulties caused by the trivalent reaction medium in electrolytes, electrodes, and electrode-electrolyte interfaces. It is hoped that the Review will stimulate scientists and engineers to develop more reliable aluminum batteries.

Paving the Path toward Reliable Cathode Materials for Aluminum-Ion Batteries

Aluminum metal is a high-energy-density carrier with low cost, and thus endows rechargeable aluminum batteries (RABs) with the potential to act as an inexpensive and efficient electrochemical device, so as to supplement the increasing demand for energy storage and conversion. Despite the enticing aspects regarding cost and energy density, the poor reversibility of electrodes has limited the pursuit of RABs for a long time. Fortunately, ionic-liquid electrolytes enable reversible aluminum plating/stripping at room temperature, and they lay the very foundation of RABs. In order to integrate with the aluminum-metal anode, the selection of the cathode is pivotal, but is limited at present. The scant option of a reliable cathode can be accounted for by the intrinsic high charge density of Al³⁺ ions, which results in sluggish diffusion. Hence, reliable cathode materials are a key challenge of burgeoning RABs. Herein, the main focus is on the insertion cathodes for RABs also termed aluminum-ion batteries, and the recent progress and optimization methods are summarized. Finally, an outlook is presented to navigate the possible future work.

Electrochromism of Nanocrystal-in-Glass Tungsten Oxide Thin Films under Various Conduction Cations

The nanocrystal-in-glass (nanocrystals embedded amorphous matrix) tungsten oxide (WO₃) thin films with a nanoporous characteristic were prepared via an electron beam evaporation technique. The e-beam evaporated WO₃ thin films present a fast colored/bleached time of 16/11, 16/14, and 12/12 s, a large optical modulation of 92, 91, and 87% at 633 nm, and a high coloration efficiency of 61.78, 62.04, and 67.59 cm² C^-1 in Li⁺, Na⁺, and Al³⁺ electrolytes, respectively. On one hand, the improved electrochromic performance is mainly attributed to the short diffusion distance and buffering effect in the host matrix, which facilitates the ion insertion/extraction and alleviates the structural collapse of the framework. On the other, owing to the strong electrostatic interactions between the trivalent cations and the host, the WO₃ thin films in Al³⁺ possess a shallow diffusion depth and long cycle life. The individual contribution from the capacitance- or diffusion-controlled process is comprehensively demonstrated. Pseudocapacitive behavior in the nanocrystal-in-glass WO₃ thin films is in favor of fast kinetics response and sound cycling stability. Our work offers an in-depth insight of the electrochromic mechanism for nanocrystal-in-glass WO₃ thin films in various electrolytes and sheds light on the fundamental principle in the electrochromic devices.

Emerging Nonaqueous Aluminum-Ion Batteries: Challenges, Status, and Perspectives

Aluminum-ion batteries (AIBs) are regarded as viable alternatives to lithium-ion technology because of their high volumetric capacity, their low cost, and the rich abundance of aluminum. However, several serious drawbacks of aqueous systems (passive film formation, hydrogen evolution, anode corrosion, etc.) hinder the large-scale application of these systems. Thus, nonaqueous AIBs show incomparable advantages for progress in large-scale electrical energy storage. However, nonaqueous aluminum battery systems are still nascent, and various technical and scientific obstacles to designing AIBs with high capacity and long cycling life have not been resolved until now. Moreover, the aluminum cell is a complex device whose energy density is determined by various parameters, most of which are often ignored, resulting in failure to achieve the maximum performance of the cell. The purpose here is to discuss how to further develop reliable nonaqueous AIBs. First, the current status of nonaqueous AIBs is reviewed based on statistical data from the literature. The influence of parameters on energy density is analyzed, and the current situation and existing problems are summarized. Furthermore, possible solutions and concerns regarding the construction of reliable nonaqueous AIBs are comprehensively discussed. Finally, future research directions and prospects in the aluminum battery field are proposed.

Carbon Nanoscrolls for Aluminum Battery

This design provides a scalable route for in situ synthesizing of special carbon nanoscrolls as the cathode for an aluminum battery. The frizzy architectures are generated by a few graphene layers convoluting into the hollow carbon scroll, possessing rapid electronic transportation channels, superior anion storage capability, and outstanding ability of accommodating a large volume expansion during the cycling process. The electrochemical performance of the carbon nanoscroll cathode is fully tapped, displaying an excellent reversible discharge capacity of 104 mAh g^-1 at 1000 mA g^-1. After 55 000 cycles, this cathode retains a superior reversible specific capacity of 101.24 mAh g^-1 at an ultrafast rate of 50 000 mA g^-1, around 100% of the initial capacity, which demonstrates a superior electrochemical performance. In addition, anionic storage capability and structural stability are discussed in detail. The battery capacity under a wide temperature range from -80 to 120 °C is examined. At a low temperature of -25 °C, the battery delivers a discharge capacity of 62.83 mAh g^-1 after 10 000 cycles, obtaining a capacity retention near 100%. In addition, it achieves a capacity of 99.5 mAh g^-1 after 4000 cycles at a high temperature of 80 °C, with a capacity retention close to 100%. The carbon nanoscrolls possess an outstanding ultrafast charging/variable discharging rate performance surpassing all the batteries previously reported, which are highly promising for being applied in energy storage fields.