Preparation of Low-Defect Manganese-Based Prussian Blue Cathode Materials with Cubic Structure for Sodium-Ion Batteries via Coprecipitation Method.

Sodium-ion batteries have important application prospects in large-scale energy storage due to their advantages, such as safety, affordability, and abundant resources. Prussian blue analogs (PBAs) have a stable and open framework structure, making them a very promising cathode material. However, high-performance manganese-based Prussian blue cathode materials for sodium-ion batteries still suffer from significant challenges due to several key issues, such as a high number of vacancy defects and a high crystal water content. This article investigates the effects of the Fe-Mn molar ratio, Mn ion concentration, and reaction time on the electrochemical performance of MnHCF during the coprecipitation process. When Fe:Mn = 1:2, c(Mn2+) = 0.02 mol/L, and the reaction time is 12 h, the content of interstitial water molecules in the sample is low, and the Fe(CN)6 defects are few. At 0.1 C, the prepared electrode has a high initial discharge specific capacity (121.9 mAh g-1), and after 100 cycles at 0.2 C, the capacity retention rate is 65% (~76.2 mAh g-1). Meanwhile, the sample electrode exhibits excellent reversibility. The discharge capacity can still be maintained at around 75% when the magnification is restored from 5 C to 0.1 C. The improvement in performance is mainly attributed to two aspects: On the one hand, reducing the Fe(CN)6 defects and crystal water content is conducive to the diffusion and stable structure of N. On the other hand, reducing the reaction rate can significantly delay the crystallization of materials and optimize the nucleation process.

The effects of calcination on the electrochemical properties of manganese oxides.

Three different crystalline forms of Mn3O4 were successfully prepared by a liquid phase method with different additives. Using XRD, SEM, EDS, BET, compacted density and electrochemical analysis, the effects of different additives on the morphology, phase composition, surface characteristics, specific surface area, electrochemical and other physical and chemical properties of manganese oxides were investigated. The results showed that the rod type Mn3O4 was prepared by mixing ammonia water and anhydrous ethanol in a 1 : 1 ratio and an appropriate amount of cetylmethyl ammonium bromide as the additive. The rod-type Mn3O4 showed a maximum specific surface area of 63.87 m2 g-1 and has the advantages of low compaction density, no introduction of other impurities, and high adsorption potential. It also has excellent electrochemical performance and an impedance of 240 Ω. The specific capacity was as high as 666.5 mA h g-1 at 1C current density and 382.2 mA h g-1 after 200 cycles. The results also showed that the electrochemical performance of Mn2O3 prepared at 700 °C from the rod-type Mn3O4 was the best. When it was used as the anode material of a lithium-ion battery, it showed a high specific capacity of 712.1 mA h g-1 after 200 cycles. Therefore, the rod-type Mn2O3 material has the characteristics of high capacity, low cost and environmental friendliness and is a promising candidate anode material for lithium-ion batteries.

In-situ remediation of acid mine drainage from abandoned coal mine by filed pilot-scale passive treatment system: Performance and response of microbial communities to low pH and elevated Fe.

A field pilot-scale passive treatment system was developed for in-situ bioremediation of acid mine drainage (AMD). The microbial community and its variation were analyzed. The data proved that 93.7% of total soluble Fe and 99% of soluble Fe(II) could be removed by the system. Principal coordinates analysis (PCoA) showed that a low pH and an elevated Fe concentration within the system created a unique microbial community that was dominated by acidophilic iron-oxidizing bacteria and iron-reducing bacteria. Canonical correlation analysis (CCA) indicated that the pH, iron content and total sulfur jointly determined the composition of the microbial communities. Species of Ferrovum, Delftia, Acinetobacter, Metallibacterium, Acidibacter and Acidiphilium were highly enriched, which promoted the removal of iron. Furthermore, the results revealed important data for the biogeochemical coupling of microbial communities and environmental parameters. These findings are beneficial for further application of in-situ field bioreactors to remediate AMD.