In this study, lithium-sulfur (Li-S) cells, employing various electrolytes, were manufactures to investigate the impact of the electronic conductivity of S-carbon composite cathode layer, the Li_6.25Al_0.25La₃Zr₂O₁₃ (Al-LLZO) solid electrolyte separator, and highly-concentrated liquid electrolytes on the electrochemical reaction of S-cathodes. Firstly, the composite particles comprising nanocarbon and S were optimized by using various nanocarbon materials. Then, the highly-concentrated electrolytes, containing sulfolane solvents, proved effective in suppressing the dissolution of discharge intermediates, such as Li₂S₈ and Li₂S₆. However, some irreversible behavior of S-cathode was still observed, attributed to the dissolution of discharge intermediates, and S itself, even within the highly concentrated electrolytes. To address this issue, an Al-LLZO solid electrolyte pellet was introduced as a separator in the Li-S cell. This separator served to prevent contact between discharge intermediates and Li-metal anode, thus minimizing chemical self-discharge of intermediates resulting from S-discharge. The use of the Al-LLZO solid electrolyte separator led to improved reversibility of the S-cathode. In fact, the discharge capacity retention was enhanced employing this cell configuration, combining the highly-concentrated electrolyte and the Al-LLZO separator. However, the cell impedance increased during the extended cycle testing, leading to degradation of the discharge capacity. This can be attributed to the loss of electronic conductivity within the cathode layer, caused by the volume change in S, and the formation of a resistive layer on the Al-LLZO solid electrolyte, stemming from chemical reactions with the discharge intermediates.

The precise and rapid detection of ammonia nitrogen is of paramount importance in safeguarding water environments. In this study, we introduce a novel approach for electrochemical ammonia sensing using nanocubic copper electrodes, fabricated through a straightforward electrodeposition technique. A comprehensive characterization of the copper electrode sheds light on the pivotal role of deposition in shaping the morphology of copper particles, subsequently impacting the ammonia sensing capabilities. Through an in-depth investigation of the electrochemical behavior of nanocubic copper electrodes, we unveil how ammonia enhances electron transfer during copper oxidation by forming robust coordination with Cu(II) and simultaneously disrupting the oxide layer on the copper surface. This synergistic effect process has been effectively harnessed for the rapid electrochemical quantification of ammonia nitrogen. Linear scan voltammetry results reveal a direct relationship between peak currents and ammonia nitrogen concentrations spanning the broad range of 0.1–100 ppm. Notably, the nanocubic copper electrode exhibits a low detection limit, exceptional resistance to interference and impressive repeatability. Moreover, our practical testing in real water samples show the nanocubic copper electrode’s superior performance over the spectrometric method in determining ammonia nitrogen concentrations. These findings underscore the potential of the nanocubic copper electrode for high-performance ammonia sensing applications.

The local pH values in the close vicinity of the cathode/anode were experimentally determined to be strongly acidic/weakly basic, respectively, during the operation of a high-voltage aqueous sodium-ion battery with Prussian blue-type electrodes and a concentrated aqueous electrolyte. The observed pH gradient was ascribed to O₂/H₂ evolution at the cathode/anode in aqueous cells, which should contribute to the expansion of the electrochemical window if the pH gradient is maintained. An increase in the distance between the cathode and anode proved to be one of possible solution to suppress the undesired pH neutralization. On the other hand, the reduction of water as well as the dissolved O₂ in the electrolyte may diminish the capacity of the anode by a self-discharge. This became more pronounced if the full cell was left to stand for a longer time after charging.

It is essential in the production of the next generation of rechargeable batteries to elucidate the reaction phases formed after co-sintering in all-solid-state batteries with oxide solid electrolytes and silicon materials and their electrochemical behavior. Herein, we explore the presence or absence of reaction phases and the charge/discharge behavior after co-sintering with the solid electrolyte Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) and various silicon active anode materials. In the co-sintering investigation of LAGP and silicon active anode materials, α-FeSi₂ do not react with LAGP and the electronic conductivity of α-FeSi₂ is maintained even after sintering. In addition, using a mixed sintered sheet consisting of α-FeSi₂, solid electrolyte LAGP, and carbon additive vapor-grown carbon fiber, a charge/discharge test is performed at 105 °C for the cell with a Li metal counter electrode and polymer electrolyte. The results of X-ray diffraction measurements of the disassembled test cell after charging/discharging confirm that the reduction decomposition reaction proceeding and disappearing of LAGP phase completely when Li is inserted into the active anode material for the first time. However, when Li is further inserted, Li alloy phases, Li₂₂Si₅, and Li₂₂Ge₅ appear, and they show reversible charge/discharge behavior of 400 mA h g⁻¹. This is presumed to be owing to the partial reduction of α-FeSi₂ to Si and the reduction decomposition of LAGP to produce Ge during the Li insertion process, followed by the formation of Li alloy phases with Li and Si or Ge. Furthermore, while the solid electrolyte LAGP disappear during the first Li insertion, the formation of a Li₄SiO₄ phase with a broad peak is observed, suggesting that the Li₄SiO₄ phase might function as a Li conductor.

The hydration condition of an anion exchange membrane (AEM) in an operating fuel cell significantly affects its performance as well as its lifespan. In this paper, an in-house build coherent anti-Stokes Raman scattering (CARS) vibrational spectroscopy is used to establish the hydration of an AEM in an anion exchange membrane fuel cell (AEMFC) while it generates power. During steady-state operation, water on the anode side increased with current density. On the cathode side and at the center of the membrane, water initially decreased with current density and then started increasing at a slower pace than on the anode side. A deconvolution of the OH peak in the recorded CARS spectra into nine species revealed that only the H-bonded water species underwent variation. The rest of the species experienced a negligible change. A transient study revealed that maximum disturbance to the water distribution was achieved after 5 s of applying a current jump. The distribution of water became stable within 20 s after applying the current jump. The response to the current jump on the anode side was opposite to that on the cathode. These results open the way for a widespread dynamic study of water distribution in different AEMFCs. The technique could also be directly used to evaluate the dynamic degradation of AEMs.

Carbon-coated SiO (SiO-C) pelletized electrode without binder materials and solid electrolytes worked as negative electrode materials for sulfide-based all-solid-state batteries. The SiO-C pelletized electrode exhibited the high capacity (ca. 1340 mAh g⁻¹) for all-solid-state batteries using lithium-ion conducting sulfide-based solid electrolyte at room temperature. The SiO-C pelletized electrode containing sulfide solid electrolyte exhibited superior cycle stability compared to the SiO-C pelletized electrode. Their SiO-C pelletized electrodes are promising as high-performance negative electrodes for all-solid-state batteries.