Electrolytic Manganese Dioxide Research Articles

Unveiling electrochemical insights of lithium manganese oxide cathodes from manganese ore for enhanced lithium-ion battery performance

Implementing manganese-based electrode materials in lithium-ion batteries (LIBs) faces several challenges due to the low grade of manganese ore, which necessitates multiple purification and transformation steps before acquiring battery-grade electrode materials, increasing costs. At present, most Lithium Manganese Oxide (LMO) materials are synthesized using electrolytic manganese dioxide, and the development of new processes, such as hydrometallurgical processes is important for achieving a cost-effective synthesis of LMO materials. In this work, we develop a full synthesis process of LMO materials from manganese ore, through acid leaching, forming manganese sulfate monohydrate (MnSO4·H2O), an optimized thermal decomposition (at 900, 950 or 1000 °C) producing different Mn3O4 materials and a solid-state reaction, achieving the synthesis of LMO. The latter was used as a cathode material for LIB exhibiting a specific capacity comparable to the state-of-the-art LMO cathode with a remarkable cycling stability of 800 cycles with <20 % in capacity loss. These performances were attributed to the excellent redox reversibility of the LMO cathode, characterized by voltammetry and in operando and in situ characterization by Raman and XRD.

Lithium extraction from geothermal brine using γ-MnO2: A case study for Tuzla geothermal power plant

Geothermal brines contain high concentrations of ions and form a source of various valuable elements. The isolation of the elements from their water systems is a great challenge when the gradual depletion of ores in mining is considered. Attempts have been made for a long time to isolate valuable elements from aqueous mixtures prepared in the laboratory. However, those studies might not reflect the complexity of natural systems and might yield results that deviate significantly from the performance in real field systems. In this study, sorption is used to extract lithium ions from a representative field, Tuzla Geothermal Power Plant (TGPP) Turkey, using a mini-pilot reactor introduced to the reinjection well of the plant. Electrolytic manganese dioxide (γ-MnO2), a relatively inexpensive material widely used as the cathode material in lithium-ion batteries, was employed as a sorbent material for lithium. The sorption/desorption performance of the novel γ-MnO2 was investigated under various conditions. Sorption is performed at 360K and 2 bars. The maximum sorption performance was obtained at 1 h in Tuzla GPP. The desorption experiments were performed in acidic solutions. The concentration of Li+ in the desorption solution was found to be 25 mg/L on average when 10 g of γ-MnO2 was dispersed into 30 mL of the acidic aqueous solution. The first desorption solution was used consecutively for collecting more Li+ ions through the desorption of fresh brine-treated powder samples (cumulative desorption). By repeating this process four times consecutively, 230 mg/L of Li+ was obtained in the desorption solution. Moreover, the reusability of the γ-MnO2 sorbent was examined. The sorbent powder showed almost 40% performance efficiency compared to virgin powder under the conditions employed in this study. The use of electrolytic γ-MnO2 sorbent for lithium adsorption was found to be a promising process for practical use in the separation of lithium from geothermal brines.

Synthesis of Porous Carbon Honeycomb Structures Derived from Hemp for Hybrid Supercapacitors with Improved Electrochemistry.

Energy storage in electrochemical hybrid capacitors involves fast faradaic reactions such as an intercalation, or redox process occurring at a solid electrode surface at an appropriate potential. Hybrid sodium-ion electrochemical capacitors bring the advantages of both the high specific power of capacitors and the high specific energy of batteries, where activated carbon serves as a critical electrode material. Herein, we have demonstrated that a porous honeycomb structure activated carbon derived from Australian hemp hurd (Cannabis sativa L.) in aqueous Na2SO4 electrolyte showed a specific capacitance of 240 F/g at 1 A/g.The hybrid sodium-ion device employing hemp-derived activated carbon (HAC) coupled with electrolytic manganese dioxide (EMD) in an aqueous Na2SO4 electrolyte showed a specific capacitance of 95 F/g at 1 A/g having a capacitance retention of 90%. The hybrid device (HAC||EMD) can possess excellent electrochemical performance metrics, having a high energy density of 38 Wh/kg at a power density of 761 W/kg. Overall, this study provides insights into the influence of the activation temperature and the KOH impregnation ratio on morphology, porosity distribution, and the activated carbon's electrochemical properties with faster kinetics. The high cell voltage for the device is devoted to the EMD electrode.

Exploration of TiMn/Ti anode for optimizing the structure and performance of electrolytic manganese dioxide

With the deepening application of manganese based cathode materials in new energy vehicle power batteries and wind solar energy storage batteries, diversified application scenarios also demand higher and more diverse performance of manganese based cathodes. This work adopts a new type of TiMn/Ti anode to replace traditional Ti anode preparing electrolytic manganese dioxide (EMD), to meet the requirements of manganese based batteries. Results show that the electrolysis process based on TiMn/Ti anode successfully achieves controllable adjustment of EMD structure by changing process parameters. Besides, the relationship between EMD structure and battery performance was studied. Meanwhile, density functional theory (DFT) calculation reveals that the existence of Mn (III) in EMD is the key to prepare a optimized non-stoichiometry Li1+yMn2-yO4. This work improves the performance of the cathodes of manganese based batteries by optimizing the quality of raw materials, providing a new perspective for the development of high-quality manganese based batteries.

New Electrocatalyst with the Content of Ir

Introduction Proton exchange membrane (PEM) water electrolysis (WE) is a promising technology for hydrogen production. However, the local environment of the anode in PEMWE is highly acidic and high potential due to the oxygen evolution reaction (OER; 2H2O → O2 + 4H+ + 4e-), and the available anode materials are limited to precious metal elements such as Pt, Ru and Ir. In the current technology, Ir-based materials are the mainstream anode catalysts, and Ir loading of 1-2 mg/cm2 is necessary to achieve both activity and durability. On the other hand, the annual production of Ir is said to be only 5-7 tons. The demand for hydrogen is expected to increase to the GW scale in the future. For example, if water electrolysis is operated at 2 A/cm2 and 2 V with Ir loading of 2 mg/cm2 (0.5 mgIr/W), it is difficult to meet the demand with the existing Ir resources. Tosoh have been engaged in the electrolytic manganese dioxide (EMD) business. EMD is synthesized thorough anodic oxidation of Mn2+ ion (Mn2+ + 2H2O → MnO2 + 4H+ + 2e-) under acidic conditions, therefore it is potentially suitable for the anode environment of PEMWE. In this study, a very small amount of Ir (<0.1 mg/cm2) was successfully composited with EMD. The resulting composite consisting of Ir and EMD showed more active than commercial Ir oxide with the same Ir content, and operated stably for at least 1000 h. Experiment EMD thin film was electrodeposited anodically on Pt-coated Ti fibers (Pt/Ti) thorough electrolyzing a mixed solution of MnSO4 and H2SO4. The obtained EMD-coated Pt/Ti were immersed in an Ir-containing solution, and then annealed to obtain Ir-containing EMD (hereinafter referred to as "Ir-EMD"). The Pt-coated Ti fibers are used as a porous transport layer (PTL) in PEMWE cells, and our developed material serves as both an OER catalyst and a PTL. OER property was evaluated using a PEMWE cell at 80°C in a two-electrode system. Pt-supported carbon was used as the cathode catalyst and Nafion®-115 as the PEM. See Fig. 1 for PEMWE cell construction flow. Result and discussion The Ir content in Ir-EMD was determined to be 0.1 mg/cm2 by ICP-AES. This Ir content is 10-20 times lower than that used in current PEMWE electrolyzers. The OER activity of Ir-EMD was evaluated by linear sweep voltammetry (LSV) (Fig. 2). For comparison, EMD (with no Ir) and Ir oxide (commercial product) with an Ir content of 0.1 mg/cm2 were evaluated in the same way. The slow OER property of EMD was improved dramatically by introducing Ir into EMD. Also, at the same amount of Ir, Ir-EMD exhibited higher OER activity than that of Ir oxide. The inset in Fig. 2 shows Tafel plots corresponding to LSVs, and the slope of the linear region (Tafel slope) can be used to predict which elementary reaction is the rate-limiting step in the OER. The Tafel slope of Ir-EMD is 58 mV/dec., which is close to the Tafel slope of Ir oxide, 50 mV/dec. This suggests that OER on Ir-EMD proceeds by the same mechanism as Ir oxide. The durability of Ir-EMD and Ir oxide was tested at a current density of 2 A/cm2 (Fig. 3). Ir oxide was deactivated within only 8 days, and it is confirmed that Ir have disappeared after electrolysis. On the other hand, Ir-EMD has operated stably for more than 42 days (≈1000 h), with a degradation rate of only 13 μV/h. In other words, Ir-EMD has practical durability while reducing the amount of Ir by more than 10 times compared to current technology.Acknowledgements : This presentation is based on results obtained from a project, JPNP20003, subsidized by the New Energy and Industrial Technology Development Organization (NEDO). Figure 1

Synthesis of Nano-electrolytic Manganese Dioxide for Alkaline Batteries Mediated by Organic Additives

This article discusses the impact of adding organic additives like glycine (GLY), sucrose (SUC), and saccharine (SACCH) on the electrical characteristics and microstructure of electrolytic manganese dioxide (EMD), which is made from an acidic aqueous sulphate solution. The structure and chemistry of EMD were ascertained by means of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). To assess the material's potential for use in alkaline batteries, its charge-discharge properties were ascertained. It was found that the majority of MnO2 in all the EMD samples was in the γ-phase, which is electrochemically active and useful for energy storage applications. When glycine, sucrose, and saccharine were added to the solution as organic additives, the electrochemical deposition of manganese dioxide (MnO2) resulted in an increase in current efficiency and a decrease in energy consumption. The SEM images demonstrated that when EMD was deposited with an additive, small grain sizes and discrete particles free of agglomeration were formed, but large grain sizes were obtained in the absence of additives. Charge-discharge characteristics suggested that the additions improve the ability of MnO2 structure to store energy. This suggested that the additions may have an impact on the morphology and size of the particles, and consequently, the electrochemical activities of the material that was electrodeposited. In the case of the additives examined in this paper, the outcome was the creation of a material with possible use in battery technology.

Enhanced electrochemical energy storage devices utilizing a one-dimensional (1D) α-MnO2 nanocomposite encased in onion-like carbon

AbstractThis work describes the fabrication of a novel one-dimensional (1D) α-MnO2 nanorods encased in onion-like carbon (or) carbon nano-onions (OLC) via microwave irradiation techniques employing electrolytic manganese dioxide (EMD), which is especially beneficial for rapid ion and electron transfer, and great structural stability. The composite of α-MnO2 and OLC demonstrates exceptional performance as an electrode across various electrochemical energy storage systems, including zinc-ion batteries (ZIB), sodium-ion batteries (SIB), and supercapacitors (SC) than the pristine α-MnO2. In SIB systems, the composite exhibits a specific capacity of 266 mAh g−1 at initial cycle with 50% capacity retention over 500 cycles, whereas the pristine electrode delivers only 39% capacity retention. The rapid yet controlled charge transfer kinetics facilitated by OLC addition in the α-MnO2 matrix outperforms as the ZIB cathode with an excellent specific capacity of 476 mAh g−1 with 100% capacity retention, while the pristine sample exhibits 77.5% capacity retention. As a SC electrode, the α-MnO2/OLC composite exhibits better electrochemical properties such as rectangular behavior, increased specific capacitance (792 F g−1), excellent capacity retention at high current densities, and others. The higher surface area that could be offered by the OLC to the α-MnO2 matrix facilitates the improved electrochemistry in the pristine sample and this kind of modification can be a viable solution to overcome the limitations of α-MnO2 for electrochemical energy storage applications. It is important to note that the performance outputs of α-MnO2/OLC composite are far better than the regular carbon (graphite, graphene) in α-MnO2 electrodes. Further, OLC provided with high surface area and ordered morphology can play the role of conductivity booster, structural stabilizer, and electrochemical active material in all the energy storage applications which may give a significant research attention in near future.

Rechargeable Manganese Dioxide||Hard Carbon Lithium Batteries in an Ether Electrolyte

Earth-abundant, cost-effective electrode materials are essential for sustainable rechargeable batteries and global decarbonization. Manganese dioxide (MnO2) and hard carbon both exhibit high structural and chemical tunability, making them excellent electrode candidates for batteries. Herein, we elucidate the impact of electrolytes on the cycling performance of commercial electrolytic manganese dioxide in Li chemistry. We leverage synchrotron X-ray analysis to discern the chemical state and local structural characteristics of Mn during cycling, as well as to quantify the Mn deposition on the counter electrode. By using an ether-based electrolyte instead of conventional carbonate electrolytes, we circumvent the formation of a surface Mn(II)-layer and Mn dissolution from LixMnO2. Consequently, we achieved an impressive ∼100% capacity retention for MnO2 after 300 cycles at C/3. To create a lithium metal-lean full cell, we introduce hard carbon as the anode which is compatible with ether-based electrolytes. Commercial hard carbon delivers a specific capacity of ∼230 mAh g−1 at 0.1 A g−1 without plateau, indicating a surface-adsorption mechanism. The resulting manganese dioxide||hard carbon full cell exhibits stable cycling and high Coulombic efficiency. Our research provides a promising solution to develop cost-effective, scalable, and safe energy storage solutions using widely available manganese oxide and hard carbon materials.

Regeneration of waste Zn-MnO2 batteries: Value-added transformation to regenerate essential materials for sustainable battery manufacturing

Zn-MnO2 batteries have a 3–5 year shelf life and make up 75 % of portable batteries. Disposing of spent batteries is a global issue and demand for MnO2 cathode material is growing 9.6 % annually, causing increased resource use and potential toxic metal leaching risk. Eco-efficient practices are needed to reduce environmental impact through recycling and reusing end-of-life products. Herein, electrolytic manganese dioxide (EMD) of spent Zn-MnO2 batteries was recycled using a thermochemical process where the structure of EMD was upgraded resulting in improving its electrochemical performance. The applicability of the recycled EMD as cathode into a new battery was explored by examining the discharge behaviour of the Zn-MnO2 cell made in KOH electrolyte and the results were compared with the performance of an original battery/EMD. In the recycled EMD cell, γ-MnO2 transformed to Zn2Mn7O8.H2O upon discharge (with a capacity of 213 mAh.g−1) and no Mn3O4 was observed, whereas in the original EMD, discharge resulted in the formation of mainly ZnMn5O4 and Mn3O4 (with a capacity of 175 mAh.g−1). The reversibility of the intercalation of cations into the structure of γ-MnO2 and their rechargeability was further examined via charge-discharge cycles using LiOH electrolyte where the recycled EMD exhibited enhanced behaviour. This indicates that in the recycled EMD, ZnMnO2 was able to revert to the original γ-MnO2, whereas in the original EMD, the formed Mn3O4 seemed to be irreversible resulting in the poor rechargeability behaviour of such batteries. Conclusively, the proposed method is a more efficient solution for reducing environmental impacts in value-added manufacturing due to its fewer steps compared to conventional techniques.

Spinel LiMn2O4 as Electrocatalyst toward Solid-State Zinc–Air Batteries

Efficient oxygen reduction reaction (ORR) electrocatalysts are the key to advancement of solid-state alkaline zinc–air batteries (ZAB). We demonstrate an electrocatalyst, spinel lithium-manganese oxide LiMn2O4 (LMO) by a simple hydrothermal method. Scanning electron microscope (SEM), X-ray diffraction (XRD), and Raman spectra indicate that the as-synthesized LiMn2O4 presents nanoscale irregular-shaped particles with the well-known spinel structure. The polarization curve, chronoamperometery curve, and linear scanning voltammograms of rotating disk electrode (RDE) results reveal that the as-synthesized LiMn2O4 possesses a higher electrocatalytic activity than that of electrolytic manganese dioxide for the ORR. A solid-state zinc–air cell with LiMn2O4 as the air electrode catalyst has a long voltage plateau of discharge and a discharge capacity of 188.4 mAh at a constant discharge current density of 10 mA·cm−2. In summary, spinel LiMn2O4 in which the JT effect enables electron hoping between Mn3+ and Mn4+ can be regarded as an effective robust oxygen reduction catalyst.

Impact of high volume E.M.D. residue on the corrosion resistance and mechanical properties of construction materials in sulfate environment

This study examines the potential use of Electrolytic Manganese Dioxide (EMD) residue as a replacement of cement (20%wt by cement weight) in construction materials to provide anticorrosion protection on reinforcing steel and improve the strength of cementitious materials under sulfate attack. To assess the corrosion parameters, the constructed building materials were immersed in a 5%wt sulfate salt (Na2SO4), while concrete samples incorporating 20%wt EMD were prepared and subjected to mechanical, porosity and thermal tests. Moreover, SEM images were obtained in order to examine the microstructure of concrete and the extent of damage caused by sulfate ions. The results demonstrate that the inclusion of EMD caused a notable rise in the corrosion of steel bars within cement mortars, as well as a decrease in the mechanical strength of the building materials. Overall, the experimental outcomes of the study suggest that the incorporation of high volume (20%wt) EMD residue leads to the degradation of all measured properties.

The effect of chaos circuits on the polymorphs of electrolytic manganese dioxide

Electrolytic manganese dioxide (EMD) is the critical component of the cathode material in modern alkaline, lithium, and sodium batteries. Aimed at the remediation of EMD crystalline structures, this research explored the effect of external power-supplying models on EMD structure regulation. The chaos electro circuit was found to impact the characteristics of EMD such as the crystalline structure, also the nanostructure morphology, and the hysteresis behavior.

Increasing the efficiency of secondary resources in the mining and metallurgical industry

An improved methodology is presented for assessing the economic feasibility and effectiveness of recycling industrial waste. The methodology is based on the break-even control mechanism, but at the same time provides for the introduction of new evaluation criteria such as the threshold of conditionality and the degree of ore substitution. Based on an improved analysis, it becomes possible to more precisely predict recycling efficiency. A more refined determination of the lower limit of concentration of recoverable metals, at which technogenic waste can be assigned the status of secondary raw materials and processed profitably, leads to a significant expansion of the secondary raw material base suitable for recycling. The potential for recycling manganese-containing dust from the production of ferrosilicomanganese, dehydrated sludge from the hydro separation of slags, and cake from the production of electrolytic manganese dioxide at the Chiatura mining enterprise is used as an example. It is shown that with a threshold of -24% Mn content, the highest recycling efficiency can be achieved by the production of low-phosphorus manganese slag and conversion to ferrosilicomanganese using the above waste to replace 40-60% grade III and IV manganese concentrates in the feed.

Synergetic control of hydrogen evolution and ion-transport kinetics enabling Zn anodes with high-areal-capacity

Intrinsic uneven Zn deposition-dissolution and hydrogen evolution reaction (HER) induce poor reversibility and limited cycle life of Zn anodes, which thus restrict the practical application of rechargeable aqueous Zn batteries. In this work, a synergistic strategy of porous indium (In) coating layer combined with a polyacrylamide (PAM) polymer layer for Zn anodes is proposed to provide large HER overpotential while facilitating fast and homogeneous Zn2+ transport at the electrode-electrolyte interface. The corrosion reaction and Zn dendrite growth are simultaneously prevented at high utilization of Zn anodes. The optimal ZnIn-PAM electrodes demonstrate outstanding cycling stability at ultra-high current density and areal capacity (10 mA cm−2, 10 mAh cm−2, Zn utilization: 57%) for over 400 h, and long-term lifespan for over 1700 h at 5 mA cm−2 and 5 mAh cm−2 (Zn utilization: 28.5%) with only ∼50 mV overpotential. Coupled with electrolytic manganese dioxide cathode, the full cell delivers ultra-long lifespan of 10000 cycles with capacity decay rate of 0.006% per cycle at 5 C. This work provides useful perspective for exploring synergetic strategies to address the limited cycling stability of Zn metal-based aqueous batteries for practical use.

The Effects of the Carbon Materials and the Electrolyte Content on the Second-Electron Reaction of Electrolytic MnO2 in Alkaline Systems

A low-cost battery with high energy density, high safety, and made with low scarcity material is needed for stationary storage applications. Electrolytic manganese dioxide (EMD), which is non-toxic, abundant, and low cost, is suitable for such applications. EMD has a high theoretical energy density (617 mAh g-1) for its two-electron reaction. However, most previous works focused on the first-electron reaction of EMD, which only provides an energy density of 308 mAh g-1. The dissolution-precipitation process during the second electron reaction of MnO2 based cathode was regarded as the main reason for the formation of Mn3O4 and will greatly affect the cycling stability of the electrode.1Recent works found that additives like Bi2O3 and Cu could help form a stable birnessite phase and suppress the dissolution of manganese during cycling, resulting in a very stable cycling performance.2However, the mass loading of the active material in these studies was still low and required additives like carbon nanotubes, which are not commercially favorable.In our work, we investigated the EMD second-electron reaction in an electrolyte-lean T-cell system, with very little excess electrolyte. We compared EMD performance in the T-cell with its performance in the electrolyte-flooded beaker cell system at different cycling rates in both KOH and NaOH electrolytes. We found a huge improvement in the stability of EMD when cycled in the electrolyte-lean T-cells especially with NaOH electrolyte (Fig. 1a). We also explored the influence of different carbon materials, including multi-walled carbon nanotube (MWCNT), graphite and Super P carbon blacks in the electrolyte-lean system (Fig. 1b). Different carbon materials were found to have a great impact on both capacity and cycling stability performance of the EMD cathode, possibly due to differences in the specific surface area and the pore sizes of the carbon materials. Electrodes with higher EMD loading and chemically synthesized Bi-doped birnessite material were also tested in the T-cell system to find a more economically favorable electrode composition. Scanning electron microscopy, X-ray diffractions, and other techniques were used to evaluate the phase change and morphology difference during the cycling process.Figure 1. (a) Comparison between T-cells with 37 wt.% KOH with 21 wt.% NaOH as electrolyte with a normal beaker cell with 37 wt.% KOH electrolytes. The electrodes composed of 60 wt.% EMD, 12 wt.% Bi2O3, 14 wt.% Cu, 10 wt.% MWCNT and 4 wt.% PTFE, NiOOH were used as anodes. The C-rate of all tests is C/3. (b) Comparison between different carbon material materials that used in the electrode in T-cells. The electrodes composed of 60 wt.% EMD, 12 wt.% Bi2O3, 14 wt.% Cu, 10 wt.% carbon material and 4 wt.% PTFE, NiOOH were used as anodes and 30 wt.% NaOH was used as electrolyte. The C-rate of all tests is C/3. G. S. Bell and R. Huber, Electrochim. Acta, 10, 509–512 (1965).G. G. Yadav, J. W. Gallaway, D. E. Turney, M. Nyce, J. Huang, X. Wei, and S. Banerjee, Nat. Commun., 8, 1–9 (2017). Figure 1

Statistical Approach to Design Zn Particle Size, Shape, and Crystallinity for Alkaline Batteries

The modern alkaline primary battery is composed of a highly alkaline, gelled electrolyte-zinc powder anode dispersion (slurry), a cellulose-based separator, and an electrolytic manganese dioxide (EMD) cathode pellet – typically arranged in a cylindrical cell geometry. This battery system has its origins in the 1950s and thus has had decades to be researched and matured and it is known that the limiting performance of this battery system is concentrated at the slurried zinc anode. This had led many researchers to focus on the anode for improvement with most previous engineering efforts targeting enhanced performance, capacity, and stability of this material. Due to the various material fabrication processes involved with manufacturing industrial zinc powder, there exists an array of unique zinc particle size, shape, and crystallinity combinations that distinguish industrial zinc powders from one another. These industrial zinc powders are typically produced through trial-and-error processes using existing “rules of thumb”. Consequentially, it is possible that something has been missed and a data-driven approach could elucidate the optimum combination of zinc particle properties.In this study, we investigate the effect of Zn particle size, shape, and degree of crystallinity on the achievable capacity and corrosion current. Various types of zinc powders were sieved into size fraction ranges and chemically and thermo-chemically treated to control their crystallinity. The procedure for producing zinc powders of various sizes, shapes, and crystallinities led to a 64-powder Zn matrix that was then electrochemically analyzed by linear sweep voltammetry to determine the corrosion current and galvanostatically discharged to determine the achievable capacity. These experiments were done in a newly-designed, custom-built electroanalytical cell that will be described in the talk. Following the data collection, a 4k factorial statistical analysis was performed. This analysis identified which of the controlling variables have a statistically significant influence on the achievable capacity and corrosion. The statistical model was also able to provide guidance regarding the preferred particle shape. This information can be used to develop actionable procedures for battery manufacturers to create cells that are more stable, longer lasting, and have higher energy densities.

An Investigation on the Factors Affecting Self-Discharge in Li/CFx-MnO2 Hybrid Primary Batteries

Lithium/Carbon fluoride (Li/CFx) primary batteries have been used in commercial applications, for example implantable cardiac pacemakers, due to their high energy density, long shelf life, and wide operation temperature range (-40oC to 85oC). However, the low electrical conductivity of CFx leads to a serious initial voltage delay at the beginning of discharge and the low rate capability of Li/CFx primary batteries. To overcome these issues, CFx materials are mixed with manganese dioxide (MnO2) to form hybrid cathodes due to a good rate capability of MnO2. Generally, the electrolytic manganese dioxide (EMD) used as cathode materials in Li/MnO2 primary batteries contains about 5% of water before heat treatment. The pristine EMD materials were heat-treated to reduce the water contents. However, water can be reabsorbed by cathode materials during processing and cathode formation. In this study, we investigated the effects of residual water contents in the pristine heat-treated EMD materials and as-fabricated CFx-MnO2 cathode electrodes on the self-discharge characteristics in Li/CFx-MnO2 primary batteries. Moreover, we investigated the effect of protective film on Li anode surface on the self-discharge characteristics in Li/CFx-MnO2 primary batteries. A protective film on Li anode surface was formed by immersing it in the electrolyte or carbon dioxide treatment. We believe that this study will provide useful guidance in the enhanced electrochemical properties and fabrication process of Li/CFx-MnO2 primary batteries.

Surfactant-mediated electrodeposition of a pseudocapacitive manganese dioxide a twofer

Electrochemical energy storage is one of the most promising ways of storing energy from intermittent, renewable sources. To meet the needs, the development of scalable, earth-abundant, chemically stable, and environmentally friendly electrode materials is crucial. This work presents four cationic surfactant-mediated manganese sulfate electrolytic solutions used for the synthesis of electrolytic manganese dioxide (EMD) to produce scalable material that satisfies the pre-requisites desired for supercapacitor applications. The influence of the surfactant molecular structure, its concentration, and its interaction in the electrolytic sulfate bath was studied, which opens up new possibilities for the fabrication of the supercapacitor electrode. The performance of three surfactants (Tetradecyltrimethylammonium bromide, Didodecyldimethylammonium bromide, Benzyldodecyldimethylammonium bromide) was benchmarked against the widely used Cetyltrimethylammonium bromide under identical conditions. The surfactants were chosen based on their different head groups and hydrocarbon chains. Benzyldodecyldimethylammonium bromide-assisted EMD (EMD/B-AB) in a single-electrode device showed improved capacitance of 602 F g−1 (at 1 mA cm−2) over the other surfactant-mediated samples. The molecular dynamics simulations indicated that the electrodeposition of manganese dioxide is highly influenced by B-AB, as it adsorbs with the aryl group planar to the Pb surface. The appropriate concentration of B-AB surfactant in the bulk solution appears to be incorporated into the EMD deposit due to their hydrophobic nature and controlled nucleation and established improved pseudocapacitive performance to score a twofer. The asymmetric capacitor of EMD/B-AB30 vs. porous activated carbon exhibited a high specific capacitance of 91 F g−1, with an energy density of 32.4 Wh kg−1 for a corresponding power density of 971 W kg−1.

Facile Electrode Additive Stabilizes Structure of Electrolytic MnO2 for Mild Aqueous Rechargeable Zinc-Ion Battery

Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted much attention recently due to the high abundance, low cost, high theoretical capacity up to 820 mAh g-1 with multi-valent charge carrier, and compatibility with aqueous electrolyte of the zinc anode.[1] Especially, the introduction of neutral or mild acidic electrolyte greatly improves the reversibility of zinc anode compared to conventional alkaline ZIBs.[2] Among all the cathode candidates, MnO2 is most attractive due to its relatively high energy density, low toxicity and low cost.[3] However, MnO2 electrode suffers from capacity fading during cycling mainly due to Mn dissolution and structural change. The addition of Mn2+ into the mild acidic electrolyte is a common method to suppress Mn dissolution.[4] Other strategies like structural design and surface coatings are also developed to suppress Mn dissolution.[5, 6] Though the cycle performance still cannot meet the demand of application, as the irreversible formation of inactive ZnMn2O4 during cycles still requires to be tackled.Here, we proposed Bi2O3 as a facile electrode additive in the electrode to suppress ZnMn2O4 formation and improve the cyclability of commercial electrolytic manganese dioxide (EMD). XRD, in-situ pH measurements and ICP tests suggest that inactive ZnMn2O4 is formed upon cycling due to the interaction between MnO2 and zincate ions in the electrolyte from localized increase in pH, and Bi2O3 dissolves into the electrolyte in the presence of zincate ions and forms a complex with the zincate ions to suppress the reaction pathway. A high capacity of 269 mAh g-1 is maintained at 100 mA g-1 after 50 cycles with a capacity retention of 91.5% when EMD with 10 wt% of Bi2O3 is tested in ZnSO4 electrolyte without Mn2+ additive. Combining both Bi2O3 electrode additive and Mn2+ electrolyte additive, EMD can maintain a stable capacity of 190 mAh g-1 for 1000 cycles at 1000 mA g-1 (about 3.3C). More characterizations are underway to further understand the role of Bi2O3 and the results will be shown during the meeting.Reference:[1] B. Tang, L. Shan, S. Liang, J. Zhou, Issues and opportunities facing aqueous zinc-ion batteries, Energy & Environmental Science, 12 (2019) 3288-3304.[2] J. Hao, X. Li, X. Zeng, D. Li, J. Mao, Z. Guo, Deeply understanding the Zn anode behaviour and corresponding improvement strategies in different aqueous Zn-based batteries, Energy & Environmental Science, 13 (2020) 3917-3949.[3] N. Zhang, X. Chen, M. Yu, Z. Niu, F. Cheng, J. Chen, Materials chemistry for rechargeable zinc-ion batteries, Chemical Society Reviews, 49 (2020) 4203-4219.[4] H. Pan, Y. Shao, P. Yan, Y. Cheng, K.S. Han, Z. Nie, C. Wang, J. Yang, X. Li, P. Bhattacharya, Reversible aqueous zinc/manganese oxide energy storage from conversion reactions, Nature Energy, 1 (2016) 1-7.[5] J. Huang, Z. Wang, M. Hou, X. Dong, Y. Liu, Y. Wang, Y. Xia, Polyaniline-intercalated manganese dioxide nanolayers as a high-performance cathode material for an aqueous zinc-ion battery, Nature communications, 9 (2018) 1-8.[6] B. Wu, G. Zhang, M. Yan, T. Xiong, P. He, L. He, X. Xu, L. Mai, Graphene scroll‐coated α‐MnO2 nanowires as high‐performance cathode materials for aqueous Zn‐ion battery, Small, 14 (2018) 1703850. Figure 1

Electrochemical Stability of ZnMn2O4: Understanding Zn-Ion Rechargeable Battery Capacity and Degradation

We present a refined Mn-Zn-H$_2$O Pourbaix diagram with the emphasis on parameters relevant for the Zn/MnO$_2$ rechargeable cells. It maps out boundaries of electrochemical stability for MnO$_2$, ZnMn$_2$O$_4$, ZnMn$_3$O$_7$, and MnOOH. The diagram helps to rationalize experimental observation on processes and phases occurring during charge/discharge, including the position of charge/discharge redox peaks and capacity fade observed in rechargeable aqueous Zn-ion batteries for stationary storage. The proposed Pourbaix diagram is validated by observing the pH-dependent transformation of electrolytic manganese dioxide to hetaerolite and chalcophanite during discharge and charge, respectively. Our results can guide the selection of operating conditions (the potential range and pH) for existing aqueous Zn/MnO$_2$ rechargeable cells to maximise their longevity. In addition, the relation between electrochemical stability boundaries and operating conditions can be used as an additional design criterion in exploration of future cathode materials for aqueous rechargeable batteries.