Mn3O4 nanocrystalline@carbon nanotube-carbon nanotube for long-lifetime and excellent rate-capability zinc-ion storage

Enabling Long-cycling Aqueous Zn-Mn3O4 Batteries via Segregated and Interlaced Carbon Frameworks

Mn3O4 is a promising candidate for aqueous zinc ion batteries (ZIBs) due to its high theoretical capacity (468.5 mAh g-1) and environmental friendliness, while its practical application is hindered by slow kinetics and rapid capacity degradation. Herein, a porous Mn3O4 with segregated and interlaced carbon framework (HCF-Mn3O4) is introduced. The in situ hydro-assembled interlaced carbon nanotube (CNT) forms a porous structure enhancing electron conduction and accelerating Zn2+ transport; while the segregated CNT network serves as an encapsulation layer to improve mechanical stability. Together, these features facilitate the simultaneous insertion and transformation of H+/Zn2+ and enhance Zn2+ diffusion kinetics. As a result, HCF-Mn3O4 achieves a high specific capacity of 474 mAh g-1 at 0.05 A g-1, excellent rate performance of 178 mAh g-1 at 1.50 A g-1, and stable cycling over 3000 cycles with minimal capacity decay (≈0.02% per cycle). This design offers new opportunities for developing high-rate, long-lasting ZIBs.

Regulating the zinc ion transport kinetics of Mn3O4 through copper doping towards high-capacity aqueous Zn-ion battery

High working voltage, large theoretical capacity and cheapness render Mn3O4 promising cathode candidate for aqueous zinc ion batteries (AZIBs). Unfortunately, poor electrochemical activity and bad structural stability lead to low capacity and unsatisfactory cycling performance. Herein, Mn3O4 material was fabricated through a facile precipitation reaction and divalent copper ions were introduced into the crystal framework, and ultra-small Cu-doped Mn3O4 nanocrystalline cathode materials with mixed valence states of Mn2+, Mn3+ and Mn4+ were obtained via post-calcination. The presence of Cu acts as structural stabilizer by partial substitution of Mn, as well as enhance the conductivity and reactivity of Mn3O4. Significantly, based on electrochemical investigations and ex-situ XPS characterization, a synergistic effect between copper and manganese was revealed in the Cu-doped Mn3O4, in which divalent Cu2+ can catalyze the transformation of Mn3+ and Mn4+ to divalent Mn2+, accompanied by the translation of Cu2+ to Cu0 and Cu+. Benefitting from the above advantages, the Mn3O4 cathode doped with moderate copper (abbreviated as CMO-2) delivers large discharge capacity of 352.9 mAh g-1 at 100 mA g-1, which is significantly better than Mn3O4 (only 247.8 mAh g-1). In addition, CMO-2 holds 203.3 mAh g-1 discharge capacity after 1000 cycles at 1 A g-1 with 98.6 % retention, and after 1000 cycles at 5 A g-1, it still performs decent discharge capacity of 104.2 mAh g-1. This work provides new ideas and approaches for constructing manganese-based AZIBs with long lifespan and high capacity.

K-Mn3O4-NCs@PANI nanochains for high-rate and stable aqueous zinc-ion batteries: A doping and morphology-tailored synthesis strategy

Aqueous zinc ion batteries (AZIBs) are promising energy storage solutions due to their high energy density and safety. However, developing cathode materials that offer both high energy density and durability for Zn2+ ions storage remains challenging. Manganese (Mn) oxide-based cathodes have been developed for AZIBs due to their high discharge voltage and desirable capacity, but face challenges like poor conductivity, slow reaction kinetics, and dissolution during cycling. Doping, morphology/structure design, and protective layers are effective for enhancing the structure, conductivity, and electronic properties of Mn-based oxides. A synthetic strategy combining these methods for Mn3O4 cathodes is proposed for AZIBs. K+ ions doping in Mn3O4 (K-Mn3O4) can regulate local electronic structure, induce oxygen vacancies, improve conductivity, and provide more active sites for Zn2+ ions diffusion. Additionally, K-Mn3O4 nanochain (K-Mn3O4-NCs), with a unique chain-like nanostructure (NCs) and high aspect ratio, synthesized via Mn2+ ions chelation with nitrilotriacetic acid (NTA) and calcination, show reduced interparticle contact resistance, shorter Zn2+ ions diffusion length, and faster reaction kinetics. Meanwhile, the in-situ polymerized polyaniline (PANI) layer on K-Mn3O4-NCs shields against corrosion (K-Mn3O4-NCs@PANI), connects 1D K-Mn3O4-NCs into a continuous conductive network, suppresses volume expansion, and improves stability. Electrochemical analysis shows that K-Mn3O4-NCs@PANI exhibits higher stability and faster reaction kinetics due to a reduced bandgap, increased oxygen defects, and less coulombic repulsion between Zn2+ ions and Mn oxide hosts. The K-Mn3O4-NCs@PANI cathode achieved a high capacity of 510 mAh/g at 0.1 A/g and excellent rate capacity of 203.2 mAh/g at 5 A/g. After 20,000 cycles, it maintained a capacity of 90.3 mAh/g at 5 A/g, showing exceptional long-term stability with a minimal decay rate of 0.026 ‰ per cycle.

A New High-Performance Porous Carbon-Coated Mn3O4/Na2CO3 Cathode for Suppressing Mn2+Dissolution in Aqueous Zinc Ion Batteries

Manganous-manganic oxide (Mn3O4), akin to other manganese-based oxides, faces several critical challenges such as substantial capacity fading and limited rate performance due to its inferior electrical conductivity, in addition to the inevitable dissociation of Mn2+. To address these issues, we introduce for the first time a novel carbon-coated Mn3O4/Na2CO3 (Mn3O4/Na2CO3/C) composite material. Comprehensive characterizations indicate that Na2CO3 effectively curtails Mn2+dissolution, enhances carbon encapsulation throughout charging/discharging cycles, and exposes additional active sites on the Mn3O4/Na2CO3/C composite. Electrochemical assessments confirm that the Mn3O4/Na2CO3/C-2 cathode exhibits exceptional electrochemical performance, outperforming other cathodes in the ZnSO4 system. Moreover, the Mn3O4/Na2CO3/C-2 cathode delivers a high specific capacity of ~550 mAh gM-1 at 0.1 A g-1 and maintains a significant capacity of ~230 mAh g-1 after 360 cycles at 1.0 A g-1 within the 2.0 M ZnSO4+0.2 M MnSO4 electrolyte system, demonstrating its potential as a high-performance cathode material for aqueous zinc-ion batteries.

In situ growth of Mn3O4 nanoparticles on accordion-like Ti3C2Tx MXene for advanced aqueous Zn-Ion batteries

Manganese-based cathodes are competitive candidates for state-of-the-art aqueous zinc-ion batteries (AZIBs) because of their easy preparation method, sufficient nature reserve, and environmental friendliness. However, their poor cycle stability and low rate performance have prevented them from practical applications. In this study, Mn3O4 nanoparticles were formed in situ on the surface and between the interlayers of Ti3C2Tx MXene, which was pretreated by the intercalation of K+ ions. Ti3C2Tx MXene not only provides abundant active sites and high conductivity but also hinders the structural damage of Mn3O4 during charging and discharging. Benefiting from the well-designed K-Ti3C2@Mn3O4 structure, the battery equipped with the K-Ti3C2@Mn3O4 cathode achieved a maximum specific capacity of 312 mAh/g at a current density of 0.3 A/g and carried a specific capacity of approximately 120 mAh/g at a current density of 1 A/g, which remained stable for approximately 500 cycles. The performance surpasses that of most reported Mn3O4-based cathodes. This study pioneers a new approach for building better cathode materials for AZIBs.

Deciphering the storage mechanism of biochar anchored with different morphology Mn3O4 as advanced anode material for lithium-ion batteries

Biochar is regarded as a promising lithium-ion batteries anode material, owing to its high cost-effectiveness. However, the poor specific capacity and cycling stability have limited its practical applications. A straightforward and cost-efficient solvothermal method is presented for synthesizing Mn3O4/biochar composites in this study. By adjusting solvothermal temperatures, Mn3O4 with different morphology is prepared and anchored on the biochar surface (MKAC-T) to improve the electrochemical performance. Due to the morphological effect of nanospherical Mn3O4 on the biochar surface, the MKAC-180 anode material demonstrates outstanding reversible capacity (992.5 mAh/g at 0.2 A/g), significant initial coulombic efficiency (61.1 %), stable cycling life (605.3 mAh/g at 1.0 A/g after 1000 cycles), and excellent rate performance (385.8 mAh/g at 1.6 A/g). Moreover, electro-kinetic analysis and ex-situ physicochemical characterizations are employed to illustrate the charge storage mechanisms of MKAC-180 anode. This study provides valuable insights into the "structure-activity relationship" between Mn3O4 microstructure and electrochemical performance for the Mn3O4/biochar composites, illuminating the industrial utilization of biomass carbon anode materials.

Butterfly-tie like MnCO3@Mn3O4 heterostructure enhanced the electrochemical performances of aqueous zinc ion batteries

Due to the limited exploitation and utilization of fossil energy resources in recent years, it is imperative to explore and develop new energy materials. As an electrode material for batteries, MnCO3 has the advantages of safety, non-toxicity, and wide availability of raw materials. But it also has some disadvantages, such as short cycle period and low conductivity. In order to improve these deficiencies, we designed a MnCO3@Mn3O4 heterostructure material by a simple solvothermal method, which possessed a microstructure of "butterfly-tie". Owing to the introduction of Mn3O4 and the layered structure of "butterfly-tie", MnCO3@Mn3O4 possessed a discharge capacity of 165 mAh/g when the current density was 0.2 A/g and exhibited satisfactory rate performance. The MnCO3@Mn3O4 heterostructure was optimized by density functional theory (DFT), and the deformation charge density was calculated. It was found that the MnCO3@Mn3O4 heterostructure is stable owing to the molecular interaction between the O atoms from MnCO3 and the Mn atoms from Mn3O4 at the interface of heterojunction. Therefore, the MnCO3@Mn3O4 heterostructure material has promising applications as safe and efficient cathode material for energy batteries.