Rechargeable Aluminum Research Articles

Self‐Discharge Behavior of Graphitic Cathodes for Rechargeable Aluminum Batteries

AbstractSelf‐discharge, which is associated with energy efficiency loss, is a critical issue that hinders practical applications of rechargeable aluminum batteries (RABs). The self‐discharge properties of two commonly‐used RAB positive electrode materials, namely natural graphite (NG) and expanded graphite (EG), are investigated in this work. EG, which has a wider spacing between graphitic layers and a larger surface area, has a higher self‐discharge rate than that of NG. After 12 h of rest, NG and EG electrodes retain 74% and 63% of their initial capacities, respectively, after charging up to 2.4 V at 0.3 A g−1. Operando X‐ray diffraction, X‐ray photoelectron spectroscopy, and energy‐dispersive X‐ray spectroscopy are employed to study the self‐discharge mechanism. The self‐discharge loss is related to the spontaneous deintercalation of AlCl4− anions from the graphite lattice charge‐compensated by Cl2 gas evolution at the same electrode and can be restored (i.e., no permanent damage is caused to the electrodes) in the next charge‐discharge cycle. It is found that the charging rate and depth of charge also affect the self‐discharge properties. In addition, the self‐discharge rates of NG in 1‐ethyl‐3‐methylimidazolium chloride–AlCl3 and urea–AlCl3 electrolytes are compared.

Spatial reticulate polytriphenylamine cathode material with enhanced capacity for rechargeable aluminum ion batteries

Spatial reticulate polytriphenylamine cathode material with enhanced capacity for rechargeable aluminum ion batteries

A solution-to-solid conversion chemistry enables ultrafast-charging and long-lived molten salt aluminium batteries

Conventional solid-to-solid conversion-type cathodes in batteries suffer from poor diffusion/reaction kinetics, large volume changes and aggressive structural degradation, particularly for rechargeable aluminium batteries (RABs). Here we report a class of high-capacity redox couples featuring a solution-to-solid conversion chemistry with well-manipulated solubility as cathodes—uniquely allowed by using molten salt electrolytes—that enable fast-charging and long-lived RABs. As a proof-of-concept, we demonstrate a highly reversible redox couple—the highly soluble InCl and the sparingly soluble InCl3—that exhibits a high capacity of about 327 mAh g−1 with negligible cell overpotential of only 35 mV at 1 C rate and 150 °C. The cells show almost no capacity fade over 500 cycles at a 20 C charging rate and can sustain 100 mAh g−1 at 50 C. The fast oxidation kinetics of the solution phase upon initiating the charge enables the cell with ultrafast charging capability, whereas the structure self-healing via re-forming the solution phase at the end of discharge endows the long-term cycling stability. This solution-to-solid mechanism will unlock more multivalent battery cathodes that are attractive in cost but plagued by poor reaction kinetics and short cycle life.

Lewis metal salt synthesis of V2C (MXene) composite nickel diselenide as a high-performance cathode material for secondary aluminum batteries

Rechargeable aluminum batteries are promising energy storage devices that have advantages over lithium-ion batteries in terms of safety, cost, and capacity. Herein, a V2C (MXene) composite nickel diselenide (V2C@NiSe2) cathode is synthesized by etching V2AlC MAX phase via Lewis acidic molten salts and then calcining it with selenium. The V2C@NiSe2 cathode material exhibited reversible redox reactions of Ni2+/Nix+, and Se-/Sex+ in the charge–discharge process. Due to the fact that selenium can also replace functional groups on V2C, it can effectively avoid strong interactions between AlCl4- and V2C layers, thereby increasing their energy density. By using V2C@NiSe2 as the cathode material for aluminum batteries, the first cycle discharge specific capacity reached 486.8 mAh/g and remained at 166 mAh/g after about 3800 cycles at 1 A/g. To compare the performance of the V2C@NiSe2 cathode material, additional cathode materials (V2C@MnSe, V2C@FeSe, V2C@CuSe2, and V2C@CoSe) are created using a similar synthesis process. This work demonstrates a novel synthesis method of intercalation-type composite low-dimensional cathode materials for stable secondary aluminum batteries.

Bottom growth strategy for high areal capacity rechargeable aluminum batteries

Among all practical methods to build the high specific energy battery, increasing the areal loading of active materials is a promising choice. However, increasing the areal loading of the active material will inevitably increase the areal deposition amount of aluminum. If aluminum undergoes uneven deposition, dendrite growth is an inevitable problem with the increase of aluminum deposits. In this paper, an anode structure with bottom growth mode (2P-Al2O3/Al) are proposed through anodic oxidation and laser etching technology, which can provide an inverted electric field strength (Ebottom>Etop) to induce the directional deposition of Al. We have grown a dense alumina layer on the surface and pores of the 2P-Al2O3/Al electrode, which can form a stable electrode/electrolyte interface as an SEI layer. The in-situ deposition image of the electrode indicates that aluminum preferentially grows at the bottom of the electrode, and the deposition process of aluminum is very uniform. In addition, the electrode exhibits excellent cycling stability in both half and full batteries. Even under the large areal special capacity of 20 mAh·cm−2 without presenting significant interfacial degradation and early short circuit, it can operate cycle over 900 h, which is more than 3 times that of planer aluminum anode. This technology opens a new platform for designing highly safe and stable long-term energy storage system.

Redox-Bipolar Polyimide Two-Dimensional Covalent Organic Framework Cathodes for Durable Aluminium Batteries.

Emerging rechargeable aluminium batteries (RABs) offer a sustainable option for next-generation energy storage technologies with low cost and exemplary safety. However, the development of RABs is restricted by the limited availability of high-performance cathode materials. Herein, we report two polyimide two-dimensional covalent organic frameworks (2D-COFs) cathodes with redox-bipolar capability in RAB. The optimal 2D-COF electrode achieves a high specific capacity of 132 mAh g-1. Notably, the electrode presents long-term cycling stability (with negligible ~0.0007% capacity decay per cycle), outperforming early reported organic RAB cathodes. 2D-COFs integrate n-type imide and p-type triazine active centres into the periodic porous polymer skeleton. With multiple characterizations, we elucidate the unique Faradic reaction of the 2D-COF electrode, which involves AlCl2+ and AlCl4- dual-ions as charge carriers. This work paves the avenue toward novel organic cathodes in RABs.

Redox‐Bipolare Polyimid Zweidimensionale Covalent Organic Framework Kathoden für langlebige Aluminum‐Akkumulatoren

AbstractNeuartige Aluminium‐Akkumulatoren (AlAKs) stellen eine nachhaltige Option für Energiespeichertechnologien der nächsten Generation mit niedrigen Kosten und beispielhafter Sicherheit dar. Die Entwicklung von AlAKs wird jedoch durch die begrenzte Verfügbarkeit von Hochleistungs‐Kathodenmaterialien eingeschränkt. In diesem Artikel beschreiben wir zwei Polyimid‐ basierte zweidimensionale Covalent‐Organic‐Framework‐ (2D COF) Elektrodenmaterialien mit redox‐bipolarer Fähigkeit in AlAKs. Die optimierte 2D‐COF‐Elektrode erreicht eine hohe spezifische Kapazität von 132 mAh g−1. Die Elektrode weist eine langfristige Zyklenstabilität auf (mit einem vernachlässigbaren Kapazitätsabfall von ≈0.0007 % pro Zyklus) und übertrifft damit frühere Ergebnisse organischer AlAK‐Kathoden. Unsere 2D‐COFs beinhalten n‐Type‐Imide und p‐Type‐Triazine als aktive Zentren im periodisch‐porösen Polymerskelett. Anhand umfänglicher Charakterisierungen erklären wir die ungewöhnliche Faradische Reaktion der 2D‐COF‐Elektrode, bei der AlCl2+‐ und AlCl4− Dualionen als Ladungsträger beteiligt sind. Diese Arbeit ebnet den Weg zu neuartigen organischen Kathodenmaterialien in AlAKs.

DDQ/graphite dual-ion hybrid positive electrode in new AMC/AlCl3 electrolyte for advanced aluminum-organic battery

Rechargeable aluminum battery is a promising energy storage system for large-scale application due to abundant aluminum resources and high safety. Organic small molecules with active carbonyl group as positive electrode materials are expected to provide high voltage and large capacity. High solubility in acidic ionic liquid electrolyte and low conductivity are the key challenges. Here, novel multi-group (2),3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)/graphite dual-ion hybrid positive electrode and 1-allyl-3-methylimidazolium chloride/AlCl3 (AMC/AlCl3) electrolyte are proposed. DDQ exhibit low solubility in AMC/AlCl3 electrolyte and high conductivity based on electron structure engineering by heterogeneous electron-withdrawing groups (i.e. Cl and C≡N), which brings about large capacity, high and stable discharge voltage (1.75 V). DDQ/graphite dual-ion hybrid positive electrode delivers high discharge capacity (224 mAh/g) based on reversible coordination/dissociation of AlCl2+ cations with carbonyl groups and intercalation/de-intercalation of AlCl4- anions in graphite. Excellent stability is exhibited and a large capacity of 185 mAh/g remains after 1000 cycles. The hybrid positive electrode and AMC/AlCl3 electrolyte create a promising strategy to advance aluminum batteries.

A Self‐Charging Aluminum Battery Enabled by Spontaneous Disproportionation Reaction

AbstractHerein, a self‐charging mechanism of rechargeable aluminum (Al) batteries with Chevrel phase molybdenum sulfide (Mo6S8) cathode is reported. The results unambiguously reveal that the self‐charging is a spontaneous disproportionation of Al intercalated Mo6S8 originated from the dynamic shift of Al between occupied sites during Al intercalating and resting. The theoretical study indicates that the fully Al intercalated Mo6S8 in the format of Al4/3Mo6S8 is kinetically accessible driven by electrochemical overpotential but thermodynamically unstable due to the repulsion between Al3+ cations. This mechanism is a true self‐charging with no input of any form of energy, thus distinctly superior to the previously reported self‐charging mechanisms. Based on this discovery, a semi‐flow AlMo6S8 battery is designed and demonstrated with long‐lasting discharge capability and high capacity.

Space limited growth strategy for ultra-high areal capacity rechargeable aluminum batteries

Increasing the areal loading of the electrodes is the premise to improve the energy density of devices and promote the commercialization of aluminum batteries. However, large areal loading will inevitably increase the amount of aluminum deposition per unit area and aggravate dendritic growth, which seriously affect the safety and stability of devices. In this work, a novel aluminum battery anode is reported, which not only increase the effective active area of the electrode, but also form a stable electrode/electrolyte interface to induce electrodeposition uniformly of aluminum. These traits result from the four advantages of P-Al2O3/Al electrode: (1) Homogenizing current density distribution; (2) Redistributing ion concentration gradient; (3) Limiting Al growth in micropores; (4) Large specific surface area provides adequate electrolyte contact. Such an anode retains circulate stably for more than 1400 h at the large area specific capacity of 5 mAh·cm−2. The protected anode shows also excellent cell stability over 2900 cycles when paired with high current density (10 mA·cm−2). In addition, a 480 mAh pouch cell with P-Al2O3/Al anode can remain the energy density of 170 Wh·kg−1 and the energy efficiency of 90% (calculated based on the positive active component) under the voltage of 0.5 V to 2.5 V, which means that the amplification of the battery will not reduce the performance of the Al battery. The strategy and method have important practical significance for assembling aluminum batteries with high energy density and high cycle stability.

A facile in-situ polymerization of cross-linked Poly(ethyl acrylate)-Based gel polymer electrolytes for rechargeable aluminum batteries

Rechargeable aluminum batteries are of interest owing to the nonflammability of Al metal anode and the ionic liquid electrolytes together with the low cost and high capacity of Al metal anode. However, the ionic liquid electrolytes are also moisture sensitive and highly corrosive, bringing about irreversible activity loss, undesired gas production and destructive leakage corrosion, which thus hinder the practical application of rechargeable aluminum batteries. Herein, a gel polymer electrolyte is designed via in-situ cross-linking polymerization of ethyl acrylate (EA) monomer and pentaerythritol acrylate (PETEA) crosslinker in high molar ratio of AlCl3/1-ethyl-3-methylimidazolium chloride (EMIC) ionic liquid. This gel polymer electrolyte exhibits an ionic conductivity of 1.46 × 10−3 S cm−1, a wide electrochemical window up to 3.0 V (vs. Al), alleviated moisture sensitivity and appreciable interfacial stability at room temperature. The assembled solid-state Al//graphite batteries with the gel polymer electrolyte deliver stable capacities of ∼90 mAh g−1 for 1000 cycles at the current density of 100 mA g−1 at both ambient temperature and −10 °C. Even with high-loading graphite cathode of 11 mg cm−2, capacities of ∼60 mAh g−1 can still be obtained for 300 cycles. This work provides a promising strategy for developing reliable and flexible rechargeable aluminum batteries.

Multi-electron reaction and fast Al ion diffusion of δ-MnO2 cathode materials in rechargeable aluminum batteries via first-principle calculations

Rechargeable aluminum batteries with multi-electron reaction have a high theoretical capacity for next generation of energy storage devices. However, the diffusion mechanism and intrinsic property of Al insertion into MnO2 are not clear. Hence, based on the first-principles calculations, key influencing factors of slow Al-ions diffusion are narrow pathways, unstable Al-O bonds and Mn3+ type polaron have been identified by investigating four types of δ-MnO2 (O3, O’3, P2 and T1). Although Al insert into δ-MnO2 leads to a decrease in the spacing of the Mn-Mn layer, P2 type MnO2 keeps the long (spacious pathways) and stable (2.007–2.030 Å) Al-O bonds resulting in the lower energy barrier of Al diffusion of 0.56 eV. By eliminated the influence of Mn3+ (low concentration of Al insertion), the energy barrier of Al migration achieves 0.19 eV in P2 type, confirming the obviously effect of Mn3+ polaron. On the contrary, although the T1 type MnO2 has the sluggish of Al-ions diffusion, the larger interlayer spacing of Mn-Mn layer, causing by H2O could assist Al-ions diffusion. Furthermore, it is worth to notice that the multilayer δ-MnO2 achieves multi-electron reaction of 3|e|. Considering the requirement of high energy density, the average voltage of P2 (1.76 V) is not an obstacle for application as cathode in RABs. These discover suggest that layered MnO2 should keep more P2-type structure in the synthesis of materials and increase the interlayer spacing of Mn-Mn layer for providing technical support of RABs in large-scale energy storage.

Synergistic effect of pore structure and crystalline domains enabling high capacity toward non-aqueous rechargeable aluminum batteries

Rechargeable aluminum batteries (RABs) with low cost and high safety have been regarded as a potential alternative to lithium-ion batteries. Despite the widely used graphite materials, the research on hard carbon with abundant sources and low carbonization temperature is rarely reported. Herein, a series of hard carbon materials with different degrees of graphitization is controllably fabricated through a ball-milling method. It is found that surface-specific area and pore structure are significantly affected by ball-milling time. As a result, the as-optimized product with suitable graphitization degree and pore distribution shows a high capacity (125 mAh·g−1 at 200 mA g−1 after 200 cycles) and excellent cycle stability (82.2 mAh·g−1 at 150 mA g−1 after 500 cycles). Such electrochemical performances can be ascribed to the fact that a proper graphitization degree ensures fast electrons transfer between layers, and multi-pores architectures contribute to accelerating ions migration. This work is expected to guide synthesizing a biomass-derived hard carbon via a facile and low-energy method, which may accelerate the practical application of RABs and facilitates the mass production of cathode carbon materials.

CMK3 collaborated with SexSy to build high-performance rechargeable aluminum-ion batteries

The development of rechargeable aluminum batteries (RABs) has consistently relied on the logical selection and design of cathode materials. Se has a high electrical conductivity while S has a high theoretical specific capacity; yet, both materials are known to present lethal shuttle effects, space expansion, and slow reaction kinetics. The development of RABs will be accelerated if the synergistic properties of both materials can be utilized. Various ratios of SexSy as the cathode materials for RABs, and a series of electrochemical tests are shown in this work. The rise in the ratio of Se and S leads to the improvement of the cycling performance. However, the shuttle effect of Se and S has a fatal blow to the performance of the battery. To solve this problem, (mesostructured carbon materials) CMK3 modified separators were employed between the cathode and anode to further limit the dissolution of Se, considerably improving the utilization of the active materials. Therefore, initial capacity of Al/GF/C@CMK-3/SexSy is about 539.4 mAh g−1 and reversible capacity of 314.2 mAh g−1 was likewise maintained after 500 cycles at 1.0 A g−1. RABs based on Al/S and Al/Se batteries have promising research avenues opened up by Al/SexSy batteries based on CMK3 modified separators.

Advanced structure selenium nanosphere@Ti3C2@graphene oxide with dual-channel and multiple protection strategies for Al–Se batteries

Rechargeable aluminum batteries (RABs) attract plenty of researchers due to their high theoretical energy density, first-rate safety performance, cheap and abundant mineral reserves. Nevertheless, how to solve the problems such as poor long-term cycle performance, low high-rate capacity, and low reversible capacity has become the key to realizing industrial production. Here we successfully prepare the selenium [email protected]3C2@graphene oxide ([email protected]) with an initial discharge capacity of 570.34 mAh g−1 at 1 A g−1, and the discharge capacity remains 253 mAh g−1 even after about 4000 cycles. The Ti3C2 and GO layers are coated on the surface of the selenium nanosphere (SS) successfully, which have a lot of benefits to achieve higher performance. It is worth noting that the dual-channel selenium [email protected]3C2 (SSM) structure can provide the redox reaction of selenium inside the sphere and the reversible intercalation of [AlCl4]- on the sphere's out-surface at the same time, which is the key of the dual-channel strategy. This new engineering strategy has made a great breakthrough in long-term RABs. It also expands the idea for further preparing long-term stable RABs and encourages researchers to explore more excellent cathode materials of RABs.

Recent advancement in carbon-based materials as sulfur hosts for rechargeable aluminum–sulfur (Al–S) batteries

Recent advancement in carbon-based materials as sulfur hosts for rechargeable aluminum–sulfur (Al–S) batteries

Research Progress of Cathode Materials for Rechargeable Aluminum Batteries in AlCl3/[EMIm]Cl and Other Electrolyte Systems

AbstractThe development of safe, cheap, and environmentally friendly advanced rechargeable batteries with high energy density are one of the most pressing tasks for today‘s energy crisis. With the advantages of low cost, abundant reserves, and high‐level safety, rechargeable aluminum ion batteries are considered ideal candidates for next‐generation energy storage batteries in the context of large‐scale energy applications. Relevant knowledge of energy storage materials and electrolytes, which possess close connection in between, is undeniably crucial for such research, while ironically, most attention is attracted to merely one element alone, especially the energy storage materials involving micro/nanomaterials. In this review, we focus on cathode materials matching with various electrolyte systems for rechargeable aluminum batteries and manage to provide new ideas for the preparation methods of high‐efficiency electrochemical energy storage materials, with future outlooks in this field.

Synergistic Transition-Metal Selenide Heterostructure as a High-Performance Cathode for Rechargeable Aluminum Batteries.

We synthesize and characterize a rechargeable aluminum battery cathode material composed of heterostructured Co3Se4/ZnSe embedded in a hollow carbon matrix. This heterostructure is synthesized from a metal-organic framework composite, in which ZIF-8 is grown on the surface of ZIF-67 cube. Both experimental and theoretical studies indicate that the internal electric field across the heterostructure interface between Co3Se4 and ZnSe promotes the fast transport of electron and Al-ion diffusion. As a result, the heterostructured Co3Se4/ZnSe demonstrates superior specific capacity and cycle stability compared to the single-phase Co3Se4 and ZnSe cathode materials.

Ionic Liquid Electrolytes with Mixed Organic Cations for Low-Temperature Rechargeable Aluminum–Graphite Batteries

Recently, aluminum–graphite batteries using chloroaluminate ionic liquid electrolytes have been shown to store charge with significant pseudocapacitive contributions, features attractive for energy storage systems that must function with high capacity retention and high specific power at low temperatures. Herein, we present results toward rechargeable aluminum–graphite batteries designed specifically for low-temperature applications, focusing on electrolyte design to reduce the melting point and enhance ion transport properties down to −40 °C. Chloroaluminate ionic liquid electrolytes with mixtures of organic cations, particularly imidazolium cations with different asymmetric functional groups, were used to impart disorder, disrupt ion clustering, and enhance low-temperature ion mobilities. Graphite cathodes with higher pseudocapacitive contributions showed improved specific capacity retention at lower temperatures, while aluminum anodes with higher surface roughness reduced the nucleation energy for aluminum electrodeposition. An aluminum–natural graphite battery with mixed imidazolium cations was shown to exhibit 87% specific capacity retention at −20 °C and 10 mA g–1. Overall, the results demonstrate multiple approaches to improve low-temperature aluminum battery performance and illustrate electrochemical methods that quantify electrolyte properties relevant to ion transport and clustering, which can be universally translated into other battery systems.

A Flexible Solid-State Ionic Polymer Electrolyte for Application in Aluminum Batteries

Rechargeable aluminum batteries are promising candidates for post-lithium energy storage systems. The electrolyte system of rechargeable aluminum batteries is an urgent research topic hindering the deployment in large-scale applications. To solve the critical problems of current ionic liquid electrolytes, such as leakage, corrosivity, and the need for using separators, we developed a freestanding ionic polymer electrolyte using the direct complexation of polyamide 6 (PA6) with aluminum chloride (AlCl3) and the organic salt triethylamine hydrochloride (Et3NHCl). This complexation allows a dissolution of up to 20 wt % of PA6 in the sample to achieve outstanding mechanical strength and stable electrode–electrolyte interfaces without loss of electrolyte properties. The mechanical and electrochemical properties of the polymer were studied and correlated to the complexation mechanism, which was investigated by FTIR spectroscopy. The ionic polymer electrolyte allows the elimination of unfavorable separators and achieves a high ionic conductivity up to 0.3 mS cm–1 and is capable of electrochemical stripping/plating of aluminum. An Al/graphite battery using this electrolyte provides excellent cycling performance. In addition, the nonflowing ionic polymer electrolyte eliminates the corrosion caused by electrolyte leakage in aluminum batteries and enables the use of conventional stainless steel housings. Our results indicate that this type of solid-state ionic polymer is a promising strategy for achieving stable and safe, yet flexible aluminum batteries.