Aqueous Cathode Research Articles

Modeling of Lithium-Flow Batteries with Aqueous Electrolyte

Flow batteries with aqueous electrolyte at the cathode are safe, low-cost and ecofriendly energy storage systems. When the aqueous cathode is coupled with a Li-metal anode with organic electrolyte, these batteries have extremely high energy densities (over 4,000 Wh/Kg), which makes them attractive not only for grid applications (where flow batteries are often used) but also in maritime applications such long endurance surface vessel systems and wave gliders [1-4]. In this presentation, we derive the mathematical model for lithium-flow batteries and use this model to predict the performance of the batteries under different discharge conditions, cathode microstructures, water flow velocities, etc. The results are then compared to experimental data already available in the literature. The mathematical model is based on coupling the flow equations (Navier-Stokes) with electrochemical equations for reaction rates and using average microscopic models for the cathode. For instance, Fig. 1 shows the voltage of a flow battery as a function of time for different water velocities in a flow battery simulated by solving the above model. For low water velocities, the water is not able to provide enough oxygen in the cathode and the voltage of the battery collapses after a few seconds. However, as long as the water velocity is above approx. 1.2 cm/s, the battery will have enough oxygen to operate continuously; in this case, the higher the flow of the water, the higher the voltage of the battery in the stationary state will be because of lower overpotential losses. In these simulations, the anode contained Li-metal. The cathode had a length of 1 cm (measured in the direction of water flow) and a thickness of 100 μm. The cell was discharged at a small rate of 0.01 mA/cm2. The incoming water had an oxygen concentration of 5 mg/l (which is equal to the oxygen concentration in seawater) and was pumped through the cathode at different velocities. A detailed derivation of the mathematical model and more simulation results and predictions will be presented at the meeting.

Revisiting the Charging Mechanism of α-MnO2 in Mildly Acidic Aqueous Zinc Electrolytes.

In recent years, there have been extensive debates regarding the charging mechanism of MnO2 cathodes in aqueous Zn electrolytes. The discussion centered on several key aspects including the identity of the charge carriers contributing to the overall capacity, the nature of the electrochemical process, and the role of the zinc hydroxy films that are reversibly formed during the charging/discharging. Intense studies are also devoted to understanding the effect of the Mn2+ additive on the performance of the cathodes. Nevertheless, it seems that a consistent explanation of the α-MnO2 charging mechanism is still lacking. To address this, a step-by-step analysis of the MnO2 cathodes is conducted. Valuable information is obtained by using in situ electrochemical quartz crystal microbalance with dissipation (EQCM-D) monitoring, supplemented by solid-state nuclear magnetic resonance (NMR), X-ray diffraction (XRD) in Characterization of Materials, and pH measurements. The findings indicate that the charging mechanism is dominated by the insertion of H3O+ ions, while no evidence of Zn2+ intercalation is found. The role of the Mn2+ additive in promoting the generation of protons by forming MnOOH, enhancing the stability of Zn/α-MnO2 batteries is thoroughly investigated. This work provides a comprehensive overview on the electrochemical and the chemical reactions associated with the α-MnO2 electrodes, and will pave the way for further development of aqueous cathodes for Zn-ion batteries.

Influence of Phosphate Surface Coating on Performance of Aqueous‐Processed NMC811 Cathodes in 3 Ah Lithium‐Ion Cells

AbstractAqueous processing of state‐of‐the‐art cathode materials for lithium‐ion batteries like LiNi0.8Mn0.1Co0.1O2 (NMC811) has evolved as a more sustainable and cost‐effective alternative to the conventional 1‐methyl‐2‐pyrrolidone‐based process. However, the implementation of aqueous processing is challenging due to the water sensitivity of nickel‐rich layered oxides. This study investigates the influence of a phosphate‐based NMC811 surface coating on the performance of aqueous‐processed NMC811 cathodes in 3 Ah cells. The results show that the cells with phosphate‐coated NMC811 outperform those with uncoated NMC811, i. e., they exhibited higher initial capacity and improved capacity retention during cycling. Post‐mortem characterization techniques reveal that the phosphate coating limits the lithium loss during aqueous cathode manufacturing and further reduces side reactions during cycling, resulting in a smaller increase of cell impedance.

Aqueous Processing of Ni-Rich NMC Electrodes with High Areal Capacity and Excellent Long-Term Cycling Stability

Research efforts in the last three decades have resulted in a steady increase in the energy density of Li-ion batteries (LIBs), leading to their integration into electric vehicles (EVs). Therefore, car manufacturers have increased the number of EVs in their fleets and successfully introduced them to the mass market, with 200M of EVs expected to be sold by 2025 [1] . In such a fast-growing market, the cost and environmental impact of LIB production play major roles. A crucial step in battery manufacturing is the processing of active materials to produce electrode coatings. Commercial cathode electrodes (i.e. LiNixMnxCoxO2 (NMC), LiNi0.5Mn1.5O4 (LNMO) etc.) are still largely processed using organic solvents, specifically N-methyl-2-pyrrolidone (NMP), with poly(vinylidene difluoride) (PVDF) as a binder. However, the NMP-PVDF combination has many disadvantages [2]. Firstly, the binder is considerably more expensive than water-soluble binders and not easy to dispose of at the end of the battery life. Secondly, NMP is costly and toxic, and being a volatile organic compound (VOC), needs solvent recovery at commercial scale. On the other hand, water-soluble binders such as Na-carboxymethylcellulose (Na-CMC) and styrene butadiene rubber (SBR) are not only cheaper but also easier-to-recycle [3]. Additionally, the use of water as a solvent would remove the need for solvent recovery. It is then clear that switching to water-based processing for cathode materials would decrease cost and improve the environmental sustainability of LIB production. Nevertheless, aqueous cathode processing has many challenges [2], the major one being the instability of the active material in water. The leaching of Li+ ions gives rise to very high pH (~ 12) values which, in turn, leads to the corrosion of the current collector (aluminium) and gas evolution during coating. Consequently, electrodes usually show cracks and pinhole defects and exhibit poor flexibility. These issues are even more enhanced for thick coatings, which are needed to achieve high energy density cells. Therefore, the electrochemical performance of water-based cathode electrodes is generally poorer than that for NMP-based electrodes.In this work, the effect of additions of phosphoric acid (H3PO4) on slurry rheology, adhesion strength, electrode morphology and the electrochemical performance of Ni-rich NMC cathodes prepared via water-based processing was investigated. To effectively bridge the gap between lab-scale investigations and industrially applicable procedures, pH control of the slurries and roll-to-roll electrode coating were performed at the pilot scale, and only electrodes exhibiting commercially relevant areal capacities (~ 4-4.5 mAh cm-2), high active material contents (> 90%) and low binder amounts (3 wt.%) were investigated. Phosphoric acid was added in amounts between 1.5 and 3 wt.%, and a fast-mixing procedure was developed to minimize the contact time between the NMC particles and water. The pH evolution over time showed that at least 2 wt.% of H3PO4 is required to keep the pH below the corrosion threshold of aluminium (pH < 9) for 6-8 hours, which is a usual time scale for industrial electrode processing. All slurries showed shear thinning behaviour with the viscosity of the water-based slurries being slightly lower than that for NMP-based slurries at the shear rate used for coating. Optical micrographs of coated electrodes showed no evidence of defects or agglomerates and good homogeneity. The adhesion to the current collector decreased with increasing amount of acid, e.g., electrodes prepared using 3 wt.% H3PO4 showed cracks at the edges of the coating and delamination.The long-term performance and rate capability of the electrodes were investigated in full-cell configuration vs graphite (coin-cell setup). NMC cathodes prepared with 1.5 wt.% acid showed a specific capacity of around 180 mAh g-1 at C/10 and 165 mAh g-1 at C/3. The specific capacity of the cells decreased with increasing amount of acid. The water-based and NMP electrodes retained around 50% and 60% of the initial capacity at 1C, respectively. Furthermore, electrodes prepared with 1.5 wt.% and 2.25 wt.% acid achieved a capacity retention above 90% after 500 cycles, which is comparable to NMP-based electrodes. In a further step, the production of the electrodes was upscaled in order to manufacture NMC/graphite pouch cells of 10 Ah capacity. These cells showed excellent cycling stability, reaching 80% SoH after 1500 cycles.

High Areal Capacity Ni-Rich NMC Water-Based Electrodes with Excellent Long-Term Cycling Stability

Research efforts in the last three decades have resulted in a steady increase in the energy density of Li-ion batteries (LIBs), leading to their integration into electric vehicles (EVs). Therefore, car manufacturers have increased the number of EVs in their fleets and successfully introduced them to the mass market, with 200M of EVs expected to be sold by 2025 [1] . In such a fast-growing market, the cost and the environmental impact of LIB production play major roles. A crucial step in battery manufacturing is the processing of anode and cathode active materials to produce electrode coatings. While commercial anode electrodes (i.e. graphite, silicon-graphite) are already water-based, cathode electrodes (i.e. LiNixMnxCoxO2 (NMC), LiNi0.5Mn1.5O4 (LNMO) etc.) are still largely processed using organic solvents, specifically N-methyl-2-pyrrolidone (NMP), with poly(vinylidene difluoride) (PVDF) as a binder. However, the NMP-PVDF combination has many disadvantages [2]. Firstly, the binder is considerably more expensive than water-soluble binders and not easy to dispose of at the end of the battery life. Secondly, NMP is also costly and toxic, and being a volatile organic compound (VOC), needs solvent recovery at commercial scale. On the other hand, water-soluble binders such as Na-carboxymethylcellulose (Na-CMC) and styrene butadiene rubber (SBR) are not only cheaper but also easier-to-recycle [3]. Additionally, the use of water as a solvent would remove the need for solvent recovery. It is then clear that switching to water-based processing for cathode materials would decrease cost and improve the environmental sustainability of LIB production. Nevertheless, aqueous cathode processing has many challenges [2], the major one being the instability of the active material in water. The leaching of Li+ ions gives rise to very high pH (~ 12) values which, in turn, leads to the corrosion of the current collector (aluminium) and gas evolution during coating. Consequently, electrodes usually show cracks and pinhole defects and exhibit poor flexibility. These issues are even more enhanced for thick coatings, which are needed to achieve high energy density cells. Therefore, the electrochemical performance of water-based cathode electrodes is generally poorer than that for NMP-based electrodes.In this work, the effect of additions of phosphoric acid (H3PO4) on slurry rheology, adhesion strength, electrode morphology and the electrochemical performance of Ni-rich NMC cathodes prepared via water-based processing was investigated. To effectively bridge the gap between lab-scale investigations and industrially applicable procedures, pH control of the slurries and roll-to-roll electrode coating were performed at the pilot scale, and only electrodes exhibiting commercially relevant areal capacities (~ 4 mAh cm-2), high active material contents (> 90%) and low binder amounts (3 wt.%) were investigated. Phosphoric acid was added in amounts between 1.5 and 3 wt.%, and a fast-mixing procedure was developed to minimize the contact time between the NMC particles and water. The pH evolution over time showed that at least 2 wt.% of H3PO4 is required to keep the pH below the corrosion threshold of aluminium (pH < 9) for 6-8 hours, which is a usual time scale for industrial electrode processing. All slurries showed shear thinning behaviour with the viscosity of the water-based slurries being slightly lower than that for NMP-based slurries at the shear rate used for coating. Optical micrographs of coated electrodes showed no evidence of defects or agglomerates and good homogeneity. The adhesion to the current collector decreased with increasing amount of acid, e.g., electrodes prepared using 3 wt.% H3PO4 showed cracks at the edges of the coating and delamination.The electrochemical performance of the electrodes was studied in full-cell configuration vs graphite. NMC cathodes prepared with 1.5 wt.% acid showed a specific capacity of around 180 mAh g-1 at C/10 and 165 mAh g-1 at C/3. The specific capacity of the cells decreased with increasing the acid amount. However, electrodes prepared with 1.5 wt.% and 2.25 wt.% acid showed excellent cycling stability, achieving a capacity retention above 90% after 500 cycles, which is comparable to NMP-based electrodes.

Manipulating chaotropic anion enables lacked H-bond aqueous electrolyte for lithium-ion hybrid capacitor

Aqueous electrochemical energy storages have multiple advantages especially safety performance in the energy storage process. The high concentration aqueous electrolytes with a wide electrochemical stable voltage window (ESW) solves the key problems of aqueous electrochemical energy storages. It effectively breaks the limitation of H2O molecule decomposition to realize aqueous electrochemical energy storage with high operating voltage. However, the slow ion transport and high cost limit their application in power-type storages. Here, the lacked H-bond aqueous electrolyte (LHE) is proposed by investigating the structures and properties of aqueous electrolytes with various chaotropic anions. The LHE achieves high conductivity, low viscosity, and low cost while ensuring a wide ESW. These excellent properties originate from the OTf− effect on the solvation structure of cations and the number of H-bonds. An aqueous Li-ion hybrid capacitor (LHC) with the LHE exhibits high operating voltage of 2.5 V and high ESW utilization of 92.6 %. The aqueous cathode electrolyte interphase formed by anions on the cathode surface also achieved a long cycle life for the LHC. It has guided the development of novel electrolytes for electrochemical energy storage.

Progressive activation of porous vanadium nitride microspheres with intercalation-conversion reactions toward high performance over a wide temperature range for zinc-ion batteries

Rechargeable aqueous zinc-ion batteries have great promise for becoming next-generation storage systems, although the irreversible intercalation of Zn2+ and sluggish reaction kinetics impede their wide application. Therefore, it is urgent to develop highly reversible zinc-ion batteries. In this work, we modulate the morphology of vanadium nitride (VN) with different molar amounts of cetyltrimethylammonium bromide (CTAB). The optimal electrode has porous architecture and excellent electrical conductivity, which can alleviate volume expansion/contraction and allow for fast ion transmission during the Zn2+ storage process. Furthermore, the CTAB-modified VN cathode undergoes a phase transition that provides a better framework for vanadium oxide (VOx). With the same mass of VN and VOx, VN provides more active material after phase conversion due to the molar mass of the N atom being less than that of the O atom, thus increasing the capacity. As expected, the cathode displays an excellent electrochemical performance of 272 mAh g−1 at 5 A g−1, high cycling stability up to 7000 cycles, and excellent performance over a wide temperature range. This discovery creates new possibilities for the development of high-performance multivalent ion aqueous cathodes with rapid reaction mechanisms.

Advances in the Aqueous Processing of Ni-Rich Positive Electrodes

A sustainable and environmental friendly production process of the battery components is a crucial factor for a successful contribution of Li-ion batteries to a more sustainable energy supply. For carbon-based anodes the eco-friendly, water-based processing is already widely established, whereas the same procedure still poses several challenges for cathode materials, especially those with high Nickel content. One major challenge is the detrimental side-reaction of Ni-rich cathode active materials (CAM) with water, creating hydroxide and carbonate species which increase the pH of the paste to above 12. Consequently, the Al foil is corroded during the coating process. Therefore, it is essential to control the paste’s pH before casting the paste on the substrate Al foil. This step becomes more challenging the longer the electrode mixing and coating procedure takes. On top of this, a promising way of improving the aqueous-based processing is to identify a suitable water-based binder system to improve the electrochemical cycling stability.We present the application of a variety of different water-based binders, all used in combination with carboxymethyl cellulose (CMC) as thickening agent. The paste pH is controlled by adding H3PO4. Electrodes with industry relevant areal capacities of up to 3 mAh/cm2 are electrochemically evaluated in full pouch cells. The long-term cycling stability determined with 1 C charge/discharge was highly dependent on the binder system. The best electrodes reached an excellent capacity retention of up to 88% after 1000 cycles. The NMP-based reference electrode reached 91%.The investigation of the aged cells via post mortem analysis suggests that the main source of cell aging is the cathode electrode. According to scanning electron microscopy data, no stronger cracking of the secondary CAM particles and no enhanced dissolution of transition metals were observed for the aqueous cathodes. However, a stronger rise in charge-transfer impedance was observed for the aged, water-based cathodes. This suggests that the formation of a blocking surface layer is the major reason for a stronger performance decay with increasing cycle number.AcknowledgmentThe presented work was financially supported by the project DigiBattPro4.0 BW (3–4332.62-IPA/69) by the Ministry of Economic Affairs, Labour and Housing Baden-Württemberg and by the project DigiBattPro4.0 BMBF funded by the German federal ministry of education and research Baden-Württemberg (03XP0374D).

Medium-Temperature Sodium-Iodine Battery System

A medium-temperature sodium-iodine battery system is presented. The rechargeable molten-sodium system works at approx. 100 °C with high efficiency, and potentially lower cost than existing high-temperature sodium-batteries (which are usually operating at a temperature of around 300 °C). Our battery system uses an aqueous iodine/iodide solution as catholyte and sodium-ion conductive Zr-based NaSICON ceramic material as solid electrolyte. The free halogen, which is formed upon charge, is complexed as highly soluble triiodide. Long-term stability of sodium-ion conductive material in contact with aqueous electrolytes, generally, is a concern. NaSICON-based ceramic material has shown not only an enhanced stability [1] against these electrolytes but also an increased sodium-ion conductivity [2], compared to sodium β″-alumina used in sodium-sulfur batteries. The sodium-iodine system has shown to operate in a stable manner with a catholyte allowing for a high total iodine concentration (>3.0 mol/L) [1]. Substitution in the NaSICON composition allows for increased ionic conductivity and enhanced stability against the aqueous cathode. In the case of fissuring of the NaSICON ceramic separator, only solid products are formed. This stops the direct reaction of active materials.[1] M. Holzapfel, D. Wilde, C. Hupbauer, K. Ahlbrecht, T. Berger, Electrochim. Acta 237 (2017), 12-21.[2] S. Naqash, Q. Ma, F. Tietz, O. Guillon, Solid State Ionics 302 (2017), 83-91.This work is funded by the German Federal Ministry of Education and Research in the project „MiTemp – Mitteltemperatur-Natriumbatterien mit flüssiger Natriumanode und wässriger Iodkathode“ (03XP0183A). Figure 1

Performance of Different Water-Based Binder Formulations for Ni-Rich Cathodes Evaluated in LiNi0.8Mn0.1Co0.1O2//Graphite Pouch Cells

Water-based processing for lithium-ion battery electrodes is attractive due to its lower manufacturing cost and smaller environmental impact. However, multiple challenges associated with aqueous cathode processing have hindered commercial adoption. Polymer binders are an important component of the electrode, and thus the choice of binders can alter electrode cycling performance significantly. In this work, four different water-based binder combinations are investigated for Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC811)-based cathodes, with a focus on the long-term electrochemical performance in practical-format full pouch cells. No additional pH-modulating additives were added to the aqueous cathode slurries, and no protective coatings were present on the cathode or aluminum current collector. Results are compared with the standard PVDF/NMP-based binder/solvent combination, used as a baseline. The influence of water-based binder type on slurry rheology and electrode microstructure are also discussed. All cells made by water-processing had worse rate performance compared to the baseline. However, the cell discharge capacity after 1000 U.S. Advanced Battery Consortium (USABC) cycles at C/3 charge/discharge rate was comparable to the baseline for two of the water-based cathode formulations (CMC & JSR, and LiPAA), demonstrating the potential viability of aqueous-processed Ni-rich cathodes at a commercial scale.

Effects of Extended Aqueous Processing on Structure, Chemistry, and Performance of Polycrystalline LiNixMnyCozO2 Cathode Powders.

The prospect of aqueous processing of LiNixMnyCozO2 (NMC) cathodes has significant appeal to battery manufacturers for the reduction in materials cost, toxicological risk, and environmental impact compared to conventional N-methyl-2-pyrrolidone (NMP)-based processing. However, the effects of aqueous processing of NMC powders at industrial timescales are not well studied, with prior studies mostly focusing on relatively brief water washing processes. In this work, we investigate the bulk and surface impacts of extended aqueous processing of polycrystalline NMC powders with different compositions. We demonstrate that at timescales of several hours, polycrystalline NMC is susceptible to intergranular fracture, with the severity of fracture scaling with the NMC nickel content. While bulk crystallinity and composition are unchanged, surface sensitive techniques such as X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) indicate that the exposure of water leads to a level of delithiation, nickel reduction, and reconstruction from the layered to rock-salt structure at the surface of individual grains. Dynamic single NMC microparticle compression testing suggests that the resulting mechanical stresses weaken the integrity of the polycrystalline particle and increases susceptibility of intergranular fracture. The initially degraded surfaces along with the increased surface area lead to faster capacity fade and impedance growth during electrochemical cycling. From this work, it is demonstrated that NMC powders require surface or grain boundary modifications to make industrial-scale aqueous cathode processing viable, especially for next-generation nickel-rich NMC chemistries.

Equilibrium Properties of a Bromine-Bromide Electrolyte for Flow Batteries

The bromine-bromide redox couple is a promising solution for aqueous cathodes of several flow batteries. In this work, we present an experimental characterization of the system Br2-HBr-H2O at chemical equilibrium, featuring isothermal measurements of Open Circuit Voltage (OCV), density and conductivity in solutions with concentrations up to 2 M Br2 and 4 M HBr. An equilibrium model considering polybromides formation that fits experimental data with an accuracy of 1.8 mV is presented. Information on activity coefficients and equilibrium constants of polybromides can be extrapolated from the model. Furthermore, alternative approaches are considered to effectively fit the measured voltage using algebraic equations, that provide a convenient tool for flow battery modeling at system-level.

Electrochemical Monitoring and Microbial Characterization of a Domestic Wastewater-Fed Microbial Fuel Cell Inoculated with Anaerobic Sludge

A dual-chambered microbial fuel cell with aqueous cathode was operated with domestic wastewater to investigate the electrogenic ability of anaerobic bacteria from a municipal wastewater treatment plant. Curves of cell potential vs. current density, power density vs. current density and current at a fixed load of 100 Ω, were obtained daily to monitor the electrochemical evolution of the system as a function of substrate use in several batch cycles. A maximum power density of 1.11 µWcm-2 was obtained after 65 days of continuous operation and a coulombic efficiency of 7% and a chemical oxygen demand removal of 76% were found in the last batch cycle. Anaerobic culture of the bacteria from the anode biofilm resulted in the isolation of two Gram-positive and two Gram-negative bacteria with divergent sugar fermentation capabilities, while analysis of 16S rRNA gene fragments showed three clones from the phyla Firmicutes, δ-Proteobacteria and α-Proteobacteria. Scanning electron imaging analysis revealed an increase in cell diversity and proliferation of methanogenic archaea when changing from synthetic to real wastewater. These results reveal the influence of substrate concentration and presence of methanogenic microorganisms on the production of power in microbial fuel cells, suggesting that future developments could be a contribution for the use of this technology to decontaminate domestic wastewater in small communities.

Improved performance of microbial fuel cell by using conductive ink printed cathode containing Co3O4 or Fe3O4

Microbial fuel cell (MFC) technology has been widely experimented nowadays, as it is a promising clean energy technology, which can harvest bioelectricity while simultaneously treating wastewater. Platinum (Pt), a precious transition metal, has long been regarded as a superior catalyst material for oxygen reduction reaction (ORR) at the cathode of the MFCs, however the high cost associated with it clutch it back for field scale applications. In this study, Co3O4 or Fe3O4 was blended with synthetically prepared conductive ink to act as microporous layer to explore its efficacy as an ORR catalyst. Applicability of these catalysts on cathode was investigated in dual chambered aqueous cathode MFCs and the performance was compared with MFC without any cathode catalyst, MFC with only conductive ink and another MFC with Pt as benchmark ORR catalyst. X-Ray diffraction, Fourier transform infrared spectra, Raman and field emission scanning electron microscope analysis were done to characterize the prepared catalysts. Cathode containing Co3O4 with conductive ink demonstrated higher reduction current (- 30 mA) than cathode having Pt and conductive ink with Fe3O4 (- 9 mA each) during cyclic voltammetry analysis. MFCs having cathodes printed with conductive ink containing Co3O4 and Fe3O4 exhibited a maximum volumetric power density of 6.62 W m−3 and 5.06 W m−3, respectively, which were much higher than the one without any catalyst (2.95 W m−3). Similarly, coulombic efficiency (CE) of 22.3%, 17.1% and 11.2% was observed in MFCs having cathode with conductive ink containing Co3O4 or Fe3O4 and without any catalysts, respectively. Moreover, more than 90% chemical oxygen demand removal efficiency was observed for MFCs having cathode with conductive ink containing Co3O4 or Fe3O4. Importantly, the performance obtained from MFC with conductive ink blended Co3O4 was found superior compared to MFC having Pt as cathode catalyst, where later produced power density of 6.13 W m−3 and CE of 21.1%. Hence, it can be concluded that Co3O4 can be used as an alternative to expensive platinum for efficient ORR in MFCs to make this technology effective for field scale application.

SiOC-based polymer derived-ceramic porous anodes for microbial fuel cells

The applicability of a new class of ceramic materials in Microbial Fuel Cells (MFCs) was investigated, targeting the development of cost-effective anode materials with long-term durability. In this work, silicon oxycarbide (SiOC)-based porous anodes were prepared by the polymer-derived ceramics (PDCs) route, using poly(methyl silsesquioxane) and poly(methyl phenyl silsesquioxane) as precursors while incorporating carbonaceous fillers (graphite and carbon black) and metal precursor (NiCl2). Tape casting was used in the manufacturing followed by pyrolysis at 1000 °C under nitrogen atmosphere. The interior structure and surface morphology were characterized with scanning electron microscopy (SEM), nitrogen adsorption, vapor adsorption, and contact angle measurements. The developed anodes were tested in MFC with aqueous cathode configuration using a low-cost clayware cylinder as the anodic chamber. The performance of MFC using PDC-based anodes was compared with MFC having carbon felt as anode material, which showed a two-fold increase in power density (211 and 111 mW m−2, respectively) and normalized energy recovery in former and also demonstrated chemical oxygen demand (COD) removal efficiency of about 85%. The improved performance of the PDC-based anodes is attributed to its porous structure, hydrophilic surface, and high specific surface area (39.89 m² g−1). The biocompatibility was confirmed by biofilm growth on the surfaces, while a sufficient electrical conductivity (0.10–0.18 S cm−1) makes it superior electrode material for application in MFCs.

Aqueous Lithium Rechargeable Battery with a Tin(II) Chloride Aqueous Cathode and a Water-Stable Lithium-Ion Conducting Solid Electrolyte

Electrical vehicles (EVs) have enjoyed extensive focus this decade as next-generation vehicles. However, high specific energy, high power density and low-cost batteries are essential for EVs to replace vehicles with internal combustion engines. Here, we propose a novel high specific energy and power density rechargeable aqueous lithium battery with an aqueous SnCl2 cathode and a lithium metal anode, where the lithium anode and the aqueous cathode are separated by a water-stable high lithium-ion conductivity solid electrolyte of Li1.4Al0.4Ge0.2Ti1.4(PO4)3. The theoretical specific energy density of this battery was 681 Wh kg−1, which is around 1.8 times higher than that of conventional lithium-ion batteries. The cell was successfully cycled at 1.5 mA cm−2 and 25°C for a specific areal capacity of 15 mAh cm−2.

High-Energy-Density Rechargeable Lithium-Nickel Chloride Aqueous Solution Batteries.

High-energy-density rechargeable batteries with performance beyond that of lithium-ion batteries are required for next-generation electric vehicles. We propose a novel rechargeable battery with a lithium anode and a NiCl2 aqueous cathode that is separated Li1.4Al0.4Ge0.2Ti1.4(PO4)3 as a water-stable lithium-ion-conducting solid electrolyte. The cell was discharged up to 93% of the theoretical cathode capacity at 0.5 mA cm–2 and 25 °C. The calculated energy density, based on the weights of NiCl2 and Li, and the average discharge voltage of 2.4 V at 0.5 mA cm–2, was 852 Wh kg–1, which is more than twice as high as that of conventional lithium-ion batteries. The cell was successfully cycled for 50 cycles without any degradation of the charge and discharge voltages at 0.5 mA cm–2 and 25 °C for 5 h charge and 5 h discharge, where the utilization of NiCl2 was 80%.

Assessment of expanded polystyrene as a separator in microbial fuel cell

ABSTRACTSeparators are considered as an important component in microbial fuel cells (MFCs) to facilitate ion transport and to prevent electrode short circuiting. In the present study, expanded polystyrene (EPS) was evaluated for the first time as a separator in a single-chamber air cathode and dual chamber aqueous cathode MFCs. The characteristics and performance of EPS were analyzed and compared with other conventionally used separators used in MFCs and was found to be competitive. Initially, the EPS was less impermeable to protons, resulting in delayed process startup (17 days) and stabilization (57 days), but gradually exhibited improved and stable performance. In the air cathode MFC with the EPS as the separator and domestic wastewater as the substrate, power production was 391 mW/m2, while power output of the aqueous cathode MFC was 328 mW/m2. The characteristics and cost analysis of EPS indicate that it can be a potential candidate as a separator in scaled-up MFC applications.

A BRIEF REVIEW ON RECENT ADVANCES IN AIR-CATHODE MICROBIAL FUEL CELLS

The performance of cathode affects the overall performance of a microbial fuel cell (MFC), and cathode configuration affects the fabrication cost of this bioelectrochemical system in a large way. Various modifications in cathode structures have been observed in MFCs. Among them air-cathode MFCs are considered to be the most efficient and sustainable option due to elimination of aeration, as required in aqueous cathodes which consumes energy and increases operating cost of MFCs. An air cathode usually consists of (a) a conductive base material, (b) current collectors, (c) catalyst layer, (d) binder layer, and (e) diffusion layer. In this article the recent advances made in fabrication of air-cathode MFC are reviewed. The advantages and disadvantages of different materials used for preparation of an air-cathode are analyzed. On-field application of MFC is limited even after a decade of extensive research. This article also presents the challenges incurred in scaling-up of an MFC for real field application. In addition, this review will assist to realize the advantages and disadvantages of different materials used in construction of air-cathodes. This knowledge will help in intelligent selection of materials for fabrication of air-cathode MFC in future and will further aid to achieve a competitive technology for electricity harvesting while treating wastewater.

High Specific Energy Density Aqueous Lithium-Metal Chloride Rechargeable Batteries

Here we show the feasibility of a novel high energy density battery with a Li anode and a MCl2 (M = Fe, Co, Ni, Cu, and Zn) aqueous cathode separated by a water-stable NASICON-type lithium-ion conducting solid electrolyte of Li1.4Al0.4Ge0.2Ti1.4(PO4)3 (LAGTP). The Li/MCl2 (M = Co, Ni, and Zn) aqueous solution with LiCl cells were successfully charged and discharged. In contrast, the Li/MCl2 (M = Fe and Cu) cells were discharged, but they could not be charged, because FeCl2 and CuCl2 reacted with lithium-ions to produce an insoluble compound. The Li/CoCl2 and Li/NiCl2 cells showed discharge cathode capacities of 326 and 412 mAh g−1 at 60°C and 4.0 m A cm−2, respectively, which correspond to 78 and 100% to the theoretical capacity, respectively. The estimated specific energy densities calculated using the mass of cell components with a 0.1 mm thick LAGTP separator (except the packaging) were 617 and 670 Wh kg−1 for the Li/CoCl2 and Li/NiCl2 cells, respectively, which are approximately two times higher than those for conventional lithium-ion batteries.