Strategies for Realizing Rechargeable High Volumetric Energy Density Conversion-Based Aluminum–Sulfur Batteries

Aluminum–sulfur batteries (ASBs) are deemed to be alternatives to meet the increasing demands for energy storage due to their high theoretical capacity, high safety, low cost, and the rich abundances of Al and S. However, the challenging problems including sluggish conversion kinetics, inferior electrolyte compatibility, and potential dendrite formation are still remained. This review comprehensively focuses on summarizing the specific strategies from polysulfide shuttling inhibition to form smooth anodic Al activation/deposition. Especially, innovations in cathodic side for achieving electrochemical kinetic modulations, electrolyte optimizations, and anodic interface mediations are discussed. Upon detailed elaborating the formation process, influencing factors, and their interactions in the Al–S electrochemistry, a comprehensive summary of their causative mechanisms and the corresponding strategies are provided, including optimization of electrolytes, innovative in situ detections, and precise electrocatalytic strategies. Based on such a systematic understanding in the Al–S electrochemistry, the possible electrochemical reaction mechanism is deciphered more clearly and enlightened practical strategies on the future development of stable ASBs. Furthermore, future opportunities and directions of high-performance conversion-based Al–S batteries for large-scale energy storage applications are highlighted.     

Significance of Current Collectors for High Performance Conventional Lithium-Ion Batteries: A Review

Conventional lithium-ion batteries (LIBs) are constantly evolving to improve their electrochemical performance and safety. In the past decade, research on electrode and electrolyte materials has significantly promoted the development of conventional LIBs. However, the current collector (CC) in conventional LIBs has not received sufficient attention. As a transfer unit that collects and disperses electrons from electrodes and transports them to the load, the performance of the CC significantly affects the performance of LIBs. This article reviews the impact of the CC on the electrochemical performance and safety of conventional LIBs in four aspects: CC requirements, manufacturing process, surface coating modification, and multifunctionalized CCs. Meanwhile, this review provides an objective summary and prospect on the transition from single-functionality to multifunctionality requirements for CC, as well as the future needs for CC development and the technical hurdles that should be overcome. The article focuses on providing a detailed insight into the important impact of CCs on conventional LIBs, which has not received enough attention in the past. It emphasizes the need and urgency for the development of multifunctional CCs to provide new ideas for improving the performance of conventional LIBs.     

Boosting Redox Kinetics of Sulfur Electrochemistry by Manipulating Interfacial Charge Redistribution and Multiple Spatial Confinement in Mott–Schottky Electrocatalysts

The serious shuttle effect and sluggish reaction kinetics intrinsically handicap the practical application of Li-S batteries. Herein, a unique 3D hierarchically porous Mott–Schottky electrocatalyst composed of W₂C quantum dots (QD) spatially confined in nitrogen-doped graphene microspheres (NGM) is proposed for regulating the kinetics of sulfur electrochemistry. Experimental and theoretical results disclose a spontaneous charge rearrangement and induce built-in electric field across the W₂C QD/NGM heterojunction interface, contributing to reduced energy barrier for both polysulfides reduction and Li₂S oxidation during entitle discharge/charge processes. Furthermore, the ultrasmall W₂C QD with high electrocatalytic activity and superior conductivity can promote the conversion of S species, while the hierarchically porous microspheres assembled from wrinkled graphene nanosheets not only can efficiently inhibit the polysulfides shuttling via multiple spatial confinement, but also provide abundant inner space for stable reservation of active S, highly conductive networks, and maintain the structural integrity of cathode during consecutive cycling. Consequently, Li-S batteries employed with the designed W₂C QD/NGM-based cathode exhibit outstanding electrochemical properties even at a high sulfur loading. The superior performance combined with the simplicity of the synthesis process represents a promising strategy for the rational design of advanced electrocatalyst for energy applications.     

Dynamic Balance of Partial Charge for Small Organic Compound in Aqueous Zinc-Organic Battery

Organic cathodes for aqueous zinc-ion batteries (AZIBs) feature intrinsic flexibility and favorable kinetics, but they suffer from high solubility. Herein, a partial charge regulation strategy is deployed by designing a small organic molecule with extended π-conjugated plane, namely benzo[i]benzo[6′,7′]quinoxalino[2′,3′:9,10]phenanthro[4,5-abc]phenazine-5,10,16,21-tetraone (PTONQ). The charge equalization of active sites induced by the extended π-conjugated plane of the PTONQ molecule combined with high aromaticity renders the molecule low solubility, fast charge transfer, and high structural stability. The fabricated Zn//PTONQ battery cycles more than 500 h at 175 mA g⁻¹ with small capacity reduction, fast charged/discharged kinetics, and anti-freeze performance (below -20°C). By a series of ex situ characterizations, it is attested that the capacity originates mainly from Zn²⁺ insertion/removal of PTONQ without H⁺ incorporation, which also accounts for the formation of Zn_x(CF₃SO₃)_y(OH)_2x-y·nH₂O by-products. This result benefits the understanding of the by-product formation mechanism of organic cathode and paves a new way to advance the aqueous Zn-organic batteries.     

Direct Synthesis of Fluorinated Carbon Materials via a Solid-State Mechanochemical Reaction Between Graphite and PTFE

Fluorinated carbon materials (FCMs) have received significant attention, because of their exceptional stability, which is associated with the strong C-F bonding, the strongest among carbon single bonds. However, the fluorination of carbon materials requires extremely toxic and moisture-sensitive reagents, which makes it inapplicable for practical uses. Here, a straightforward and relatively safe method are reported for the scalable synthesis of FCMs, by mechanochemical depolymerization of polytetrafluoroethylene (PTFE) and fragmentation of graphite. The resultant FCMs are evaluated as anode materials for lithium-ion batteries (LIBs). An optimized FCM delivered capacities as high as 951.6 and 329.3 mAh g ⁻¹ at 0.05 and 10 A g ⁻¹, respectively. It also demonstrated capacity retention as high as 76.6% even after 1000 cycles at 2.0 A g ⁻¹.     

Low-Cost Multi-Function Electrolyte Additive Enabling Highly Stable Interfacial Chemical Environment for Highly Reversible Aqueous Zinc Ion Batteries

The practicality of aqueous zinc ion batteries (AZIBs) for large-scale energy storage is hindered by challenges associated with zinc anodes. In this study, a low-cost and multi-function electrolyte additive, cetyltrimethyl ammonium bromide (CTAB), is presented to address these issues. CTAB adsorbs onto the zinc anode surface, regulating Zn²⁺ deposition orientation and inhibiting dendrite formation. It also modifies the solvation structure of Zn²⁺ to reduce water reactivity and minimize side reactions. Additionally, CTAB optimizes key physicochemical parameters of the electrolyte, enhancing the stability of the electrode/electrolyte interface and promoting reversibility in AZIBs. Theoretical simulations combined with operando synchrotron radiation-based in situ Fourier transform infrared spectra and in situ electrochemical impedance spectra further confirm the modified Zn²⁺ coordination environment and the adsorption effect of CTAB cations at the anode/electrolyte interface. As a result, the assembled Zn-MnO₂ battery demonstrates a remarkable specific capacity of 126.56 mAh g⁻¹ at a high current density of 4 A g⁻¹ after 1000 cycles. This work highlights the potential of CTAB as a promising solution for improving the performance and practicality of AZIBs for large-scale energy storage applications.     

A Universal Descriptor in Determining H2 Evolution Activity for Dilute Aqueous Zn Batteries

Large-scale energy storage with aqueous Zn batteries (AZBs) have bright future, but their practical application is impeded by H₂ evolution reaction (HER), which results in poor stability of Zn–metal anodes. Here, using linear sweep voltammetry in dilute salt aqueous electrolytes, it is discovered that as the salt concentration decreases, HER is gradually suppressed, which is contrary to prior beliefs. Combining calculations and experiments, it is demonstrated that HER derives predominantly from the sum of Zn²⁺-solvated water rather than the average amount of water in the Zn²⁺-solvation structural unit or free water without interaction with Zn²⁺, which answers the puzzle from above. This result, which differs fundamentally from the previous understandings, sheds new light on the mysterious role of water chemistry in controlling HER and contributes to a more rational design of advanced electrolytes for AZBs.     

Phase transformation and electrochemical charge storage properties of vanadium oxide/carbon composite electrodes synthesized via integration with dopamine

Chemically preintercalated dopamine (DOPA) molecules were used as both a reducing agent and a carbon precursor to prepare δ-V₂O₅·nH₂O/C, H₂V₃O₈/C, VO₂(B)/C, and V₂O₃/C nanocomposites via hydrothermal treatment or hydrothermal treatment followed by annealing under Ar flow. We found that the phase composition and morphology of the produced composites are influenced by the DOPA:V₂O₅ ratio used to synthesize (DOPA)_xV₂O₅ precursors through DOPA diffusion into the interlayer region of the δ-V₂O₅·nH₂O framework. The increase of DOPA concentration in the reaction mixture led to a more pronounced reduction of vanadium and a higher fraction of carbon in the composites’ structure, as evidenced by X-ray photoelectron spectroscopy and Raman spectroscopy measurements. The electrochemical charge storage properties of the synthesized nanocomposites were evaluated in Li-ion cells with nonaqueous electrolytes. δ-V₂O₅·nH₂O/C, H₂V₃O₈/C, VO₂(B)/C, and V₂O₃/C electrodes delivered high initial capacities of 214, 252, 279, and 637 mAh g^–1, respectively. The insights provided by this investigation open up the possibility of creating new nanocomposite oxide/carbon electrodes for a variety of applications, such as energy storage, sensing, and electrochromic devices.     

Anisotropically Hybridized Porous Crystalline Li-S Battery Separators

Anisotropically hybridized porous crystalline Li-S battery separators based on porous crystalline materials that can meet the multiple functionalities of both anodic and cathodic sides are much desired for Li-S battery yet still challenging in directional design. Here, an anisotropically hybridized separator (CPM) based on an ionic liquid-modified porphyrin-based covalent-organic framework (COF-366-OH-IL) and catalytically active metal-organic framework (Ni₃(HITP)₂) that can integrate the lithium-polysulfides (LiPSs) adsorption/catalytic conversion and ion-conduction sites together to directionally meet the requirements of electrodes is reported. Remarkably, the-obtained separator exhibits an exceptional high Li⁺ transference-number (t_Li+ = 0.8), ultralow polarization-voltage (<30 mV), high initial specific-capacity (921.38 mAh g⁻¹ at 1 C), and stable cycling-performance, much superior to polypropylene and monolayer-modified separators. Moreover, theoretical calculations confirm the anisotropic effect of CPM on the anodic side (e.g., Li⁺ transfer, LiPSs adsorption, and anode-protection) and cathodic side (e.g., LiPSs adsorption/catalysis). This work might provide a new perspective for separator exploration.     

Multiscale Structural Engineering of Sulfur/Carbon Cathodes Enables High Performance All-Solid-State Li?S Batteries

Constructing all-solid-state lithium–sulfur batteries (ASSLSBs) cathodes with efficient charge transport and mechanical flexibility is challenging but critical for the practical applications of ASSLSBs. Herein, a multiscale structural engineering of sulfur/carbon composites is reported, where ultrasmall sulfur nanocrystals are homogeneously anchored on the two sides of graphene layers with strong S C bonds (denoted as S@EG) in chunky expanded graphite particles via vapor deposition method. After mixing with Li_9.54Si_1.74P_1.44S_11.7Cl_0.3 (LSPSCL) solid electrolytes (SEs), the fabricated S@EG-LSPSCL cathode with interconnected “Bacon and cheese sandwich” feature can simultaneously enhance electrochemical reactivity, charge transport, and chemomechanical stability due to the synergistic atomic, nanoscopic and microscopic structural engineering. The assembled InLi/LSPSCL/S@EG-LSPSCL ASSLSBs demonstrate ultralong cycling stability over 2400 cycles with 100% capacity retention at 1 C, and a record-high areal capacity of 14.0 mAh cm⁻² at a record-breaking sulfur loading of 8.9 mg cm⁻² at room temperature as well as high capacities with capacity retentions of ≈100% after 600 cycles at 0 and 60 °C. Multiscale structural engineered sulfur/carbon cathode has great potential to enable high-performance ASSLSBs for energy storage applications.