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

Development of bixbyite microdice fabricated cathode for aqueous rechargeable zinc ion batteries

In this study, an ultrasonic-aided reverse micelle formation, followed by the calcination route, was developed for the synthesis of bixbyite microdice aimed at the fabrication of a cathode for ARZIBs. The prepared product was Mn2O3 having crystallinity and grain size of 65.12% and 25.61 nm, respectively, with a small percentage of other Mn-based oxides within it. The FESEM image showed dice like microsized Mn2O3, revealing the possible formation of a reverse micelle core of approximately 500 nm. XPS narrow spectra revealed the presence of Mn3+ in a mixture of Mn with +2 and +4 oxidation states. The crystal planes from the TEM images matched with XRD results and strengthened the formation of bixbyite Mn2O3 nanoparticles. The optical band gap of 3.21 eV specified the semiconducting property of the prepared Mn2O3, and therefore, the prepared Mn2O3 was used as a cathode material in a CR-2032 coin cell of ARZIBs. CV showed a reversible reaction within the cell, indicating the (de)intercalation of Zn2+ ions between the anode and cathode. The fresh cell showed high conductivity and low resistance compared with the used cell after BCD testing, confirmed by EIS. The cell delivered high specific discharge capacities of 293.59 ± 4.75 and 252.10 ± 4.66 mA h g-1 at applied current densities of 0.1 and 0.3 A g-1, respectively. Consequently, BCD was performed for 1000 cycles at a current density of 0.3 A g-1. Throughout the cycling, the capacity retention and coulombic efficiency were maintained at 90.35 ± 0.30% and 98.44 ± 0.27%, respectively, suggesting the resilient reversibility of charging and discharging.

Multiple Regulation of Electrolyte with Trace Amounts of Sodium Dehydroacetate Additives Enables High-Performance Aqueous Zinc-Ion Batteries

Rechargeable aqueous zinc-ion batteries (AZIBs) draw much attention for low cost and high safety. However, hydrogen evolution reaction (HER) and uneven Zn2+ deposition shorten lifespan, hampering commercial use. In this study, sodium dehydroacetate (SD) containing carbonyl and keto-carbonyl is introduced as multifunctional electrolyte additives, which effectively modifies the solvent shell structure, achieving a Zn2+ transference number of up to 0.72. Acting as a hydrogen bond acceptor, SD disrupts the water network structure, thereby increasing the HER overpotential by 22 mV and the corrosion potential by 9 mV. The polar functional groups in SD can reversibly capture H⁺ ions and dynamically neutralize OH⁻ ions, maintaining interfacial pH balance on the zinc anode and suppressing HER. Notably, SD not only alters the electrolyte's kinetic but also induces uniform Zn2+ deposition along the (002) plane, inhibiting dendrite growth and minimizing side reactions. This phenomenon is demonstrated in both symmetric and full-cell configurations. The Zn//Zn symmetric cell achieves an ultra-long cycling lifespan of 2800 hours at 5 mA cm⁻2, and the Zn//VO2 full battery maintains a capacity retention rate of 73.09% after 2000 cycles with a high average coulombic efficiency of 99.98%, underscoring the effectiveness of this electrolyte additive in enhancing battery performance.

Deciphering the energy storage mechanism of CoS2 nanowire arrays for High-Energy aqueous copper-ion batteries

Transition metal sulfide (TMs) offers ultra-high specific capacity through multi-electron transfer, showing promise for aqueous batteries. However, the poor cycling performance and the uncleared energy storage mechanism are restricted from further development. Herein, CoS2 nanowire arrays grown on carbon cloth (CoS2/CC) are proposed as binder-free and self-supporting electrodes for aqueous copper-ion batteries. The energy storage mechanism is clarified by a series of ex-situ tests: a multi-electron electrode reaction through a three-step reaction of CoS2 → CuS → Cu7S4 → Cu2S. Electrochemical results suggest that the CoS2/CC cathode exhibits excellent long cycle stability (capacity retention of 99.7 % after 1000 cycles at 10 A/g) along with high specific capacity (762.3 mAh g-1 at 1 A/g). The carbon cloth with stable three-dimensional (3D) conductive structure can not only offer high-speed pathways to promote the transfer of electrons but also inhibit the volume change. Meanwhile, CoS2 nanowire arrays with high surface-to-volume ratios can improve wettability of electrolyte and promote redox reactions. Furthermore, an advanced Zn-CoS2/CC hybrid ion aqueous battery reveals an energy density of 724 Wh kg-1 and an output voltage of 1.24 V, providing a promising strategy for the establishment of transition metal sulfide cathode in high-energy aqueous batteries.

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.

Triple-shelled Ni@MnO/C hollow spheres with enhanced performance for rechargeable zinc-ion capacitors

Electrochemical activation techniques and the use of multi-shell structured materials are effective strategies to enhance the electrochemical performance of rechargeable aqueous zinc-ion capacitors (ZICs). In this study, we successfully synthesized spherical Ni3Mn-MOFs via a solvothermal method and used them as templates to prepare Ni/MnO@C nanospheres with different core-shell structures by adjusting the heating rate under an Ar atmosphere. The multi-shelled structure provides more active sites and alleviates structural strain associated with repeated Zn2+ insertion/extraction processes. During the initial charge process, the Ni/MnO@C cathode undergoes electrochemical activation and generates oxygen vacancies, which can facilitate Zn2+ adsorption and promote ion diffusion, significantly enhancing its initial capacity and cycling stability. The activated Ni/MnO@C electrode exhibits an excellent capacity of 500 mA h g-1 at a current density of 0.3 A g-1, and the capacity retention rate remains as high as 90.9% even after 5200 cycles at 3 A g-1. The assembled AC//Ni/MnO@C (AC: active carbon) ZIC demonstrates an energy density of 90.14 W h kg-1 at a power density of 2750.17 W kg-1. At 3 A g-1, the capacity retention rate remains as high as 80.3% after 6000 cycles, indicating excellent long-term durability. This work provides a promising strategy for designing high-performance cathodes for the next generation of ZICs.

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.

Rice powder template for hausmannite Mn3O4 nanoparticles and its application to aqueous zinc ion battery

In this study, a simple calcination route was adopted to prepare hausmannite Mn3O4 nanoparticles using rice powder as soft bio-template. Prepared Mn3O4 was characterized by Fourier Transform Infra-Red Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray microanalysis (EDX), Powder X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET) and Solid state UV-Vis spectroscopic techniques. Mn-O stretching in tetrahedral site was confirmed by FTIR and Raman spectra. % of Mn and O content supported Mn3O4 formation. The crystallinity and grain size was found to be 68.76% and 16.43 nm, respectively; tetragonal crystal system was also cleared by XRD. TEM clarified the planes of crystal formed which supported the XRD results and BET demonstrated mesoporous nature of prepared Mn3O4 having low pore volume. Low optical band gap of 3.24 eV of prepared Mn3O4 nanoparticles indicated semiconductor property and was used as cathode material to fabricate CR-2032 coin cell of Aqueous Rechargeable Zinc Ion Battery (ARZIB). A reversible cyclic voltammogram (CV) showed good zinc ion storage performance. Low cell resistance was confirmed by Electrochemical Impedance Spectroscopy (EIS). The coin cell delivered high specific discharge capacity of 240.75 mAhg-1 at 0.1 Ag-1 current density. The coulombic efficiency was found to be 99.98%. It also delivered excellent capacity retention 94.45% and 64.81% after 300 and 1000 charge-discharge cycles, respectively. This work offers a facile and cost effective approach for preparing cathode material of ARZIBs.

Construction of MnO2Mn3O4 heterostructures to facilitate high-performance aqueous magnesium ion energy storage

MnO2-Mn3O4 heterostructure materials are applied in aqueous magnesium ion energy storage for the first time. The heterostructure yields an exceptionally high pseudocapacitance contribution, resulting in a specific capacitance of 313.5 F g-1 at 1 A g-1, which contrasts with that of MnO2 (108.8 F g-1) and Mn3O4 (123.5 F g-1). Additionally, it shows potential for practical applications as a cathode for magnesium ion hybrid supercapacitors (MHS).