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Selection, testing and validation of electrolyte candidates for Li-ion cells are discussed, based on a 10-minute target for extreme fast charge (XFC). A combination of modeling and laboratory measurements create a timely and synergistic approach to identifying candidate electrolyte formulations. Multi-solvent systems provide a balanced set of properties, wherein lower molecular-weight solvents offer reduced viscosity, increased species diffusivity, and mitigation of concentration polarization at high charge rates. Carefully selected formulations can exhibit peak conductivity and usable conductivity range of two to three times that of the baseline EC-EMC (3:7, wt.) + LiPF6. Candidates are also chosen based on stability and longevity within the cell environment. Lab testing coincides with property predictions from the Advanced Electrolyte Model (AEM) and a macro-scale cell model. Cell testing utilized coin and pouch cells having NMC532 or NMC811 cathodes with graphite electrodes. Results indicate combinations of low-molecular weight solvents are key for fast-charge electrolytes as they extend the useful conductivity range to both low and higher salt concentrations, and possess higher self-diffusivities compared to conventional solvents. This reduces impacts from concentration polarization. The choice of electrolyte also influences the tendency for lithium metal deposition at the anode, as showcased by experimental and modeling results herein.

Air-cathode fabrication is currently a key factor that hinders the scaling up of microbial fuel cell (MFC) technology. A new type of cathode material that contains porous polyethylene (PE) sheet and a blended activated carbon (AC) and highly conductive carbon back (CB) layer was developed for the first time. The PE sheet functions as both gas diffusion layer (GDL) and cathode supporting material. The blended AC and CB layer eliminates expensive current collector. Among different types of PE sheets and AC and CB blending ratios, the cathode with Type I PE sheet (75–110 μm pore size) and a CB/AC ratio of 1: 0.5 demonstrated the best performance (8.4 A m−2 at 0 V) in electrochemical cells. MFCs with this cathode generated more stable and higher power densities compared with those using PTFE cathodes. Simulation of ohmic potential drops across this cathode material suggests that using a two-parallel terminal connection design would result in only 0.04 V potential drop at 1 m2 scale. This study suggests that this new PE cathode material has great potential for use in scaled up MFC systems due to its decent performance, simple fabrication process, and use of low-cost material.

An operational advantage that enables the deployment of technologies for the valorization of CO2 can be achieved through the integration of the capture and conversion technologies. In that perspective, switchable polarity solvents (SPS) were assessed as re-usable capture-electrolyte media for the electrochemical production of syngas at low temperatures and pressures. A polymer electrolyte membrane cell was used to liberate captured CO2 gas in proximity to the cathode without the addition of CO2 gas. Due to the proximate location of release, the produced syngas had minimal CO2 dilution with H2 : CO ratios between 2 to 4. For the first time captured CO2 has been reduced to CO with conversions and yields over 70% and at current densities over 100 mA cm−2.

High concentration of total ammonia nitrogen (TAN) in the form of urea is known to inhibit the performance of many biological wastewater treatment processes. Microbial fuel cells (MFCs) have great potential for TAN removal due to its unique oxic/anoxic environment. In this study, we demonstrated that increased urea (TAN) concentration up to 3940 mg/L did not inhibit power output of single-chambered MFCs, but enhanced power generation by 67% and improved coulombic efficiency by 78% compared to those obtained at 80 mg/L of TAN. Over 80% of nitrogen removal was achieved at TAN concentration of 2630 mg/L. The increased nitrogen removal coupled with significantly enhanced coulombic efficiency, which was observed for the first time, indicates the possibility of a new electricity generation mechanism in MFCs: direct oxidation of ammonia for power generation. This study also demonstrates the great potential of using one MFC reactor to achieve simultaneous electricity generation and urea removal from wastewater.

We have synthesized a porous graphite with a high degree of local crystallinity by adding copper powder as a catalyst into the magnesiothermic reduction of CO2. Furthermore, we revealed that the enhanced crystallinity of the carbon cathode catalyst promotes the electrochemical performance of microbial fuel cells under neutral pH conditions, which provides future guidance on the selection of carbon catalysts for microbial fuel cells.

Air-cathode stability is a key factor affecting the feasibility of microbial fuel cells (MFCs) in applications. However, there is no quick and effective method to evaluate the robustness and durability of the MFC air cathodes. In this study, a three-phase decrease of power density was observed in multiple MFCs that have been operated for about a year. Quantification of the contributions of cathode biofilm and salt accumulation to the current decrease suggested that the biofouling was the major contributor to the cathode aging during the first 200 days, and salt accumulation gradually outpaced biofouling afterward. An accelerated test method was then developed using fast-growing Escherichia coli, simulated soluble microbial products (SMPs), and a concentrated medium solution. Using this method, the cathode aging can be evaluated quickly within hours/days compared to over a year of operation, benefiting the development of high-performing and durable cathode materials.

There are two main challenges associated with the scale-up of air-cathode microbial fuel cells (MFCs): performance reduction and cathode leakage/flooding. In this study, a novel 13.4 L reactor that contains 4 tubular MFCs was designed and operated in a trickling mode for 65 days under different conditions. The trickling water flow through the horizontally aligned MFCs alleviated the hydraulic pressure applied to the air-cathodes. With a total cathode working area of over 1700 cm2, this reactor generated power densities up to 1 W/m2 with coulombic efficiencies over 50% using acetate. Using a brewery waste stream as carbon source, an average power density of 0.27 W/m2 was generated with ∼60% COD removal at hydraulic retention time of 1.6 h. The decent performance of this reactor compared with other air-cathode MFCs at the similar scale and the alleviated hydraulic pressure on air-cathodes demonstrate the great potential of this design and operation for future MFC optimization and scaling up.

CO2 reduction to syngas provides a way of ameliorating carbon footprint and storing energy in high-energy-density and versatile feedstock. This current work explores the isothermal integration of CO2 capture with an intensified unit operation for the reduction of CO2 and capture media regeneration. Intensified captured CO2 co-electrolysis (ICC) to syngas (H2:CO ratio of 2) with low CO2 content ( 65 % were observed. Performance of the capture unit becomes critical to maintain syngas ratios (SR). Technology feasibility was assessed through comparative techno-economic and life cycle analysis showing that process intensification enables competitive performance, even at the higher energy consumption featured at the current state of the technology. This because several unit operations can be avoided. LCA also showed that based on the current US electricity mix the reduction of life cycle CO2 emissions is possible at scenarios observed with 0.15 A/cm2 to accomplish a carbon-negative technology.

Lithium (Li) metal serving as an anode has the potential to double or triple stored energies in rechargeable Li batteries. However, they typically have short cycling lifetimes due to parasitic reactions between the Li metal and electrolyte. It is critically required to develop early fault-detection methods for different failure mechanisms and quick lifetime-prediction methods to ensure rapid development. Prior efforts to determine the dominant failure mechanisms have typically required destructive cell disassembly. In this study, non-destructive diagnostic method based on rest voltages and coulombic efficiency are used to easily distinguish the different failure mechanisms-from loss of Li inventory, electrolyte depletion, and increased cell impedance-which are deeply understood and well validated by experiments and modeling. Using this new diagnostic method, the maximum lifetime of a Li metal cell can be quickly predicted from tests of corresponding anode-free cells, which is important for the screenings of electrolytes, anode stabilization, optimization of operating conditions, and rational battery design.

Replacing precious metal catalysts by inexpensive activated carbon (AC) is a breakthrough in microbial fuel cell (MFC) cathode fabrication. In this study, AC powders made from bamboo, peat, coal, coconut, and hardwood sources are evaluated in terms of their electrochemical performance with carbon cloth as the base material. These ACs are characterized in terms of their conductivity, surface chemistry, surface area, and pore size distribution. The bamboo-based AC demonstrates the highest potential for use as a catalyst for carbon cloth based cathode, reaching 10.6 A m−2 at 0V vs. Ag/AgCl and a loading of 25 mg cm−2. The maximum power density reached 3.3 W m−2 in CEA–MFCs. The high performance of the bamboo-based AC cathode was possible due to the good conductivity and suitable surface chemistry of the bamboo AC and the high surface area of the base material. The hydrostatic pressure tolerance of the AC carbon cloth cathode is greater than 1.8 m, allowing for a more versatile cathode, suitable for use in many different reactor configurations.

To enhance the performance of activated carbon air cathodes for microbial fuel cells (MFCs), scattered and dense air-cathodes are fabricated by the rolling-press method with the gas diffusion layer or the catalyst layer (CL) invaded to stainless steel meshes (SSM). The maximum power density with scattered cathodes (2503 ± 61 mW m−2) is 29% higher than those of dense cathodes because of the decreased internal resistance and increased oxygen reduction reaction activity. The decrease in the electrode volume density and invasion of CL into SSM has been demonstrated to be an optimal structure, with the highest exchange current density up to 1.26 A m−2 and the lowest charge transfer resistance as low as 1.5 Ω. The increase in performance is believed to result from the enhanced mass transport through extra pores and the contact of activated carbon to the current collector. This novel structure of an air-cathode has a promising future as an application in MFCs.

The fast growth of the electric vehicle (EV) market is generating increasing anxiety regarding the sources and availability of minerals required to meet with a growing demand for lithium ion batteries (LIBs). Critical elements (lithium, cobalt, and graphite) are crucial to sustain the manufacturing of a growing EV market as well as thriving wireless demand. However, the geographical concentration of mining and refining of cobalt and graphite constitute a supply chain risk for the global production of LIBs. This is driving technical development, which in turn, is leading to a dynamic change in battery chemistry. Lithium sources are more diverse in nature and geographical distribution, and current lithium reserves are enough to cover projected scenarios within the next twenty years. Nevertheless, the main question is whether the extraction technologies can keep up with the pace of market growth for EV. Interest in LIBs recycling is surging as a path to a circular battery economy and supply chain stabilization for critical materials on LIBs. Industrial processes for the recycling of LIBs are already operating around the world. However, these processes are almost exclusively focused on the recovery of Co, Ni and Mn from battery cathodes as the most valuable metals in the LIBs. Hydrometallurgical processes have been proposed for a comprehensive recovery that includes lithium and graphite, but the high operating costs and intensive chemical consumption do not support a cost-effective recovery of Li at industrial level. To target this issue, an electro-assisted reduction technology, based on the use of electrons as green reagent, has been proposed for the extraction and recovery of critical materials from LIBs. Through this process, high extraction efficiencies (>98%) can be achieved at solid to liquid ratios up to 120 g/L and in a peroxide free environment. The process is suitable to different battery chemistries and allows for the recovery of graphite as bi-product. A description of the process, as well as a flowsheet, that describes a comprehensive recovery for different value streams will be discussed.

The Pt and Nafion free air-cathode is urgently needed for large scale membrane-less single chambered microbial fuel cells (MFCs). The activated carbon air-cathode (ACAC) consisted of a sintered catalyst layer (CL) and a gas diffusion layer (GDL) made by rolling method is such a promising cathode with a high performance. However, the microstructure of the CL in terms of three phase interface (TPI) needs to be further investigated. The maximum power density increases by 35% from 802 � 20 mW m � 2

Bioelectrochemical systems (BESs) provide an opportunity to detect biological toxicity of water samples. However, the concentration responses of toxins had not been investigated in detail. Using formaldehyde as a toxic substance, the current responses were analyzed over a concentration range from 0.01% to 0.10% in a single chambered BES with 0mV (versus saturated calomel electrode) applied on the anode. The decay percentages of currents increased in proportion with the concentration of formaldehyde after 10000s (∼2.8h), with the peak R(2) of 0.9361 observed at 35,000s (∼9.7h). Fitting results of exponential decay equation showed that the magnification factor (a) closely related with baseline currents and the toxicity factor (b) was in direct proportion to formaldehyde concentration (from 0% to 0.08%) except over the high concentration of 0.10%. These results provide preliminary information about toxin concentration responses in BESs.

Nano goethite with contents of 0, 2.5%, 5.0% and 7.5% (mass percentage) were added into activate carbon powder (AC) and rolled onto stainless steel mesh to fabricate new anodes for microbial fuel cells (MFCs). The maximum power density of MFC with 5.0% α-FeOOH (693 ± 20 mW m −2 ) is 36% higher than that of the AC control (508 ± 40 mW m −2 ). Based on the decrease of charge transfer resistance and the increases of both exchange current density and anodic peak current in electrochemical impedance and polarization tests, the addition of nano α-FeOOH kinetically promotes the extracellular electron transfer between bacteria and the electrode. The increase of constant-phase element and the decrease of Warburg element show that α-FeOOH enhances both the capacitance and diffusion condition on the surface of anode. However, the excess α-FeOOH of 7.5% incurs a negative effect on surface conductivity, capacitance and diffusion, probably due to the adsorption of biogenic Fe(II) on the anodic surface.

Activated carbon (AC) is a high performing and cost effective catalyst for oxygen reduction reactions (ORRs) of air-cathodes in microbial fuel cells (MFCs). Acidic (HNO3) and alkaline (KOH) pretreatments on AC at low temperature (85°C) are conducted to enhance the performance of MFCs. The alkaline pretreatment increased the power density by 16% from 804±70 to 957±31 mW m(-2), possibly due to the decrease of ohmic resistance (from 20.58 to 19.20 Ω) and the increase of ORR activities provided by the adsorbed hydroxide ion and extra micropore area/volume after alkaline pretreatment. However, acidic pretreatment decreased the power output to 537±36 mW m(-2), which can be mainly attributed to the corrosion by adsorbed proton at the interface of AC powder and stainless steel mesh and the decreased pore area.