Multi-Ion Engineering Strategies toward High Performance Aqueous Zinc-Based Batteries

As alternatives to batteries with organic electrolytes, aqueous zinc-based batteries (AZBs) have been intensively studied. However, the sluggish kinetics, side reactions, structural collapse, and dissolution of the cathode severely compromise the commercialization of AZBs. Among various strategies to accelerate their practical applications, multi-ion engineering shows great feasibility to maintain the original structure of the cathode and provide sufficient energy density for high-performance AZBs. Though multi-ion engineering strategies could solve most of the problems encountered by AZBs and show great potential in achieving practical AZBs, the comprehensive summaries of the batteries undergo electrochemical reactions involving more than one charge carrier is still in deficiency. The ambiguous nomenclature and classification are becoming the fountainhead of confusion and chaos. In this circumstance, this review overviews all the battery configurations and the corresponding reaction mechanisms are investigated in the multi-ion engineering of aqueous zinc-based batteries. By combing through all the reported works, this is the first to nomenclate the different configurations according to the reaction mechanisms of the additional ions, laying the foundation for future unified discussions. The performance enhancement, fundamental challenges, and future developing direction of multi-ion strategies are accordingly proposed, aiming to further accelerate the pace to achieve the commercialization of AZBs with high performance.

Review and New Perspectives on Non-Layered Manganese Compounds as Electrode Material for Sodium-Ion Batteries

After more than 30 years of delay compared to lithium-ion batteries, sodium analogs are now emerging in the market. This is a result of the concerns regarding sustainability and production costs of the former, as well as issues related to safety and toxicity. Electrode materials for the new sodium-ion batteries may contain available and sustainable elements such as sodium itself, as well as iron or manganese, while eliminating the common cobalt cathode compounds and copper anode current collectors for lithium-ion batteries. The multiple oxidation states, abundance, and availability of manganese favor its use, as it was shown early on for primary batteries. Regarding structural considerations, an extraordinarily successful group of cathode materials are layered oxides of sodium, and transition metals, with manganese being the major component. However, other technologies point towards Prussian blue analogs, NASICON-related phosphates, and fluorophosphates. The role of manganese in these structural families and other oxide or halide compounds has until now not been fully explored. In this direction, the present review paper deals with the different Mn-containing solids with a non-layered structure already evaluated. The study aims to systematize the current knowledge on this topic and highlight new possibilities for further study, such as the concept of entatic state applied to electrodes.

NaFe2PO4(MoO4)2: A Promising NASICON-Type Electrode Material for Sodium-Ion Batteries

Searching for polyanionic electrode materials with high Na⁺ and electronic conductivity is pivotal to realize high-performance sodium-ion batteries. Here, we report a novel polyanionic-based NASICON-type compound, NaFe₂PO₄(MoO₄)₂ (NFPM), that does not crystallize in the common space group R-3c or C2/c but in the rare P2/c. The studies on bond valence sum maps show that NFPM has high Na⁺ conductivity because the large volumes of MoO₄ groups make the interstitial channels wider, thus making the energy barrier of Na⁺ diffusion decrease along these channels. Density functional theory calculations demonstrate that NFPM has high electronic conductivity because the contribution of Mo 4d orbitals on the formation of the bottom of the conduction band makes the connected MoO₄ groups take part in electron transport. Electrochemical tests exhibit that NFPM can deliver a capacity of ∼80 mAh g^-1 with good reversible cyclability utilizing the Fe³⁺/Fe²⁺ redox couple. In situ X-ray diffraction measurements indicate that NFPM undergoes one-phase reaction mechanism in the process of charge and discharge.

High-Performance MnO2 /Al Battery with In Situ Electrochemically Reformed Alx MnO2 Nanosphere Cathode

Aqueous Al-ion battery (AAIB) is regarded as a promising candidate for large-scale energy storage systems due to its high capacity, high safety, and low cost, with MnO₂ proved to be a high-performance cathode. However, the potential commercial application of this type of battery is plagued by the frequent structural collapse of MnO₂ . Herein, an in situ, electrochemically reformed, urchin-like Al_x MnO₂ cathode is developed for water-in-salt electrolyte-based AAIBs. Benefiting from its unique α-MnO₂ coated Mn₂ AlO₄ structure, a high Al ion storage capacity is achieved together with a high discharge voltage plateau of 1.9 V by reversible MnO₂ electrolysis. Consequently, the battery exhibits a high specific capacity of 285 mAh g^-1 and a high energy density of 370 Wh kg^-1 at a high current density of 500 mA g^-1 . Improved stability with record capacity retention is also obtained at an ultrahigh current density of 5 A g^-1 after 500 cycles. Such a high-capacity and high-stability Al_x MnO₂ cathode would pave the way for in situ electrochemical transformation of cathode design and thus boost the practical application of AAIBs.

Efficient catalytic activity and bromate minimization over lattice oxygen-rich MnOOH nanorods in catalytic ozonation of bromide-containing organic pollutants: Lattice oxygen-directed redox cycle and bromate reduction

The inhibition of bromate formation is a challenge for the application of ozonation in water treatment due to the carcinogenicity and nephrotoxicity of bromate. In this study, the high-mobility lattice oxygen-rich MnOOH nanorods were synthesized successfully and applied for the bromate inhibition during catalytic ozonation in bromide and organic pollutants-containing wastewater treatment. The catalytic ozonation system using lattice oxygen-rich MnOOH nanorods exhibited an excellent performance in bromate control with an inhibition efficiency of 54.1% compared with the sole ozonation process. Furthermore, with the coexistence of 4-nitrophenol, the catalytic ozonation process using lattice oxygen-rich MnOOH nanorods could inhibit the bromate formation and boost the degradation of 4-nitrophenol simultaneously. Based on the experiments of ozone decomposition, surface manganese inactivation and reactive oxygen species detection, the inhibition of bromate could be attributed to the effective decomposition of ozone with generating more ·O₂^- and the reduction of bromate into bromide by lattice oxygen-rich MnOOH. The existed surface Mn(IV) on lattice oxygen-rich MnOOH can accept electrons from lattice oxygen and ·O₂^- to generate surface transient Mn(II)/Mn(III), in which Mn(II)/Mn(III) can promote the reduction of bromate into bromide during catalytic ozonation. This study provides a promising strategy for the development of bromate-controlling technologies in water treatment.

A controlled synthesis of γ-MnOOH nanorods via a facile hydrothermal method for high-performance Li-ion batteries

A hydrothermal reduction route was used for the controlled production of MnOOH nanostructures. The formed γ-MnOOH nanorods can be used as one of the high performance anodes for the preparation of lithium ion batteries.

Efficient degradation of bentazone via peroxymonosulfate activation by 1D/2D γ-MnOOH-rGO under simulated sunlight: Performance and mechanism insight

An innovative 1D/2D γ-MnOOH-rGO catalyst was successfully synthesized by anchoring γ-MnOOH nanowires on rGO nanosheets. Its catalytic activity was comprehensively evaluated by bentazone degradation in PMS/simulated sunlight system. Results showed that the γ-MnOOH-rGO catalyst achieved 96.1% decomposition of bentazone within 90 min in the coupled system, improving by 26.7% compared to that obtained in the γ-MnOOH mediated system. Moreover, the newly-designed γ-MnOOH-rGO exhibited stability, recyclability and practicability for bentazone elimination. Mechanism insight highlighted that more active sites exposed on γ-MnOOH-rGO surface, providing more opportunities for PMS activation and bentazone degradation. Besides, the rGO could transfer photo-induced electrons, accelerating radical-based reactions. More importantly, ∙OH and ¹O₂ appeared in γ-MnOOH-rGO/PMS/simulated sunlight system, which played an overwhelming role in bentazone removal. In prospect, the γ-MnOOH-rGO showed promising potential for refractory contaminants remediation from aquatic environment in PMS/photocatalytic system.

A novel self-assembled-derived 1D MnO2@Co3O4 composite as a high-performance Li-ion storage anode material

Manganese dioxide (MnO₂) is a high-performance anodic material and applied widely in lithium-ion batteries (LIBs).

Fe(ii) and Mn(ii) removal by Ca(ii)–manganite (γ-MnOOH)-modified red mud granules in water

In this study, a material (DLRMG) was synthesized by modifying Ca²⁺ and manganite (γ-MnOOH) on red mud granules (RMG), which were the main raw materials derived from industrial alumina. Moreover, a series of experiments were conducted on the adsorption of Fe²⁺ and Mn²⁺ in underground water. The prepared samples were analyzed by X-ray diffraction (XRD), thermogravimetric analysis-differential thermal analysis (TG-DTA), zeta potential analysis, BET and scanning electron microscopy (SEM); the concentration of the effluent was found to be of acceptable standard after the treatment. DLRMG continued to treat fluoride wastewater even after the saturated adsorption of Fe²⁺ and Mn²⁺, and the results clearly showed that the treatment was effective. Overall, the problems of red mud stockpile and pollution in China would be effectively controlled by DLRMG.

The use of the waste of aluminum industry to prepare effective polluted materials for the treatment of underground water.

A study on electrochemical properties of P2-type Na–Mn–Co–Cr–O cathodes for sodium-ion batteries

The comprehensive electrochemical properties of P2-type Na–Co–Mn–O cathodes for sodium ion batteries could be significantly enhanced by optimal Cr-doping.

CoMn2O4 embedded in MnOOH nanorods as a bifunctional catalyst for oxygen reduction and oxygen evolution reactions

CoMn₂O₄ embedded in MnOOH nanorods (CoMn₂O₄–MnOOH NRs) was prepared using a two-step hydrothermal method involving the oxidation of Mn by Co species in preformed MnOOH NRs, and the as-prepared catalyst exhibits an expectably remarkable performance for the ORR and the OER.

Ultrasmall MnO Nanoparticles Supported on Nitrogen-Doped Carbon Nanotubes as Efficient Anode Materials for Sodium Ion Batteries

Sodium ion batteries (SIBs) have attracted increasing attentions as promising alternatives to lithium ion batteries (LIBs). Herein, we design and synthesize ultrasmall MnO nanoparticles (∼4 nm) supported on nitrogen-doped carbon nanotubes (NDCT@MnO) as promising anode materials of SIBs. It is revealed that the carbonization temperature can greatly influence the structural features and thus the Na-storage behavior of the NDCT@MnO nanocomposites. The synergetic interaction between MnO and NDCT in the NDCT@MnO nanocomposites provides high rate capability and long-term cycling life due to high surface area, electrical conductivity, enhanced diffusion rate of Na⁺ ions, and prevented agglomeration and high stability of MnO nanoparticles. The resulting SIBs provide a high reversible specific capacity of 709 mAh g^-1 at a current density of 0.1 A g^-1 and a high capacity of 536 mAh g^-1 almost without loss after 250 cycles at 0.2 A g^-1. Even at a high current density of 5 A g^-1, a capacity of 273 mAh g^-1 can be maintained after 3000 cycles.

Recent progress in layered double hydroxide based materials for electrochemical capacitors: design, synthesis and performance

As representative two-dimensional (2D) materials, layered double hydroxides (LDHs) have received increasing attention in electrochemical energy storage and conversion because of the facile tunability between their composition and morphology. The high dispersion of active species in layered arrays, the simple exfoliation into monolayer nanosheets and chemical modification offer the LDHs an opportunity as active electrode materials in electrochemical capacitors (ECs). LDHs are favourable in providing large specific surface areas, good transport features as well as attractive physicochemical properties. In this review, our purpose is to provide a detailed summary of recent developments in the synthesis and electrochemical performance of the LDHs. Their composites with carbon (carbon quantum dots, carbon black, carbon nanotubes/nanofibers, graphene/graphene oxides), metals (nickel, platinum, silver), metal oxides (TiO₂, Co₃O₄, CuO, MnO₂, Fe₃O₄), metal sulfides/phosphides (CoS, NiCo₂S₄, NiP), MOFs (MOF derivatives) and polymers (PEDOT:PSS, PPy (polypyrrole), P(NIPAM-co-SPMA) and PET) are also discussed in this review. The relationship between structures and electrochemical properties as well as the associated charge-storage mechanisms is discussed. Moreover, challenges and prospects of the LDHs for high-performance ECs are presented. This review sheds light on the sustainable development of ECs with LDH based electrode materials.