A novel design for humidifying an open-cathode proton exchange membrane fuel cell using anode purge

The low performance of open-cathode proton-exchange-membrane fuel cells (OCPEMFCs) is attributed to the low-humidity ambient air supplied to the cathode using electric fans. To improve the OCPEMFC performance, this paper proposes a novel humidification method by collecting water purged from the anode and supplying it to the open cathode. The OCPEMFC performance is evaluated at various humidifier distances from the cathode inlet, and it is compared with that where no humidifier is used when the OCPEMFC operates under three different current levels of 1, 5, and 8 A. The results show that the novel design improves the stack power, and optimal performance is achieved at a humidifier distance of 2 cm. The energy efficiency achieves an improvement between 1.4% and 1.8% when a humidifier is used.     

Dual functions of three-dimensional hierarchical architecture on improving the rate capability and cycle performance of LiNi0.8Co0.1Mn0.1O2 cathode material for lithium-ion battery

The main obstacles in lithium-ion battery are limited by rate performance and the rapid capacity fading of LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811). Herein, a novel three-dimensional (3D) hierarchical coating material has been fabricated by in situ growing carbon nanotubes (CNTs) on the surfaces of Ni–Al double oxide (Ni–Al-LDO) sheets (named as LDO&CNT) with Ni–Al double hydroxide (Ni–Al-LDH) as both the substrate and catalyst precursor. The resultant LDO&CNT nanocomposites are uniformly coated on the surfaces of NCM811 by the physical mixing method. The rate capability of the resultant cathode material retains to 78.80% at a current rate of 3C. Its capacity retention increases by 6.7–14.42% compared with pristine NCM811 after 100 cycles within a potential range of 2.75–4.3 V at 0.5C. The improved rate capability and cycle performance of NCM811 are assigned to the synergistic effects between Ni–Al-LDO and CNTs. The hierarchical LDO&CNT nanocomposites coating on the surface of NCM811 avoids the aggregation of conductive CNTs and the stacking of Ni–Al-LDO nanosheets. Furthermore, it accelerates Li⁺ and electrons shuttle and reduces the reaction of Li₂O with H₂O and CO₂ in air, which results in Li₂CO₃ and LiOH alkali formation on the NCM811 surface.     

铝业废阴极炭块资源化利用技术研究

为实现铝业废阴极炭块在钢铁冶金流程中资源化利用，通过深入研究废阴极炭块的相关物性，结合炼钢工艺对炭素及氟化物的物质需求，明确了废阴极炭块的无害化资源利用原理，工业试验结果表明废阴极炭块在炼钢转炉内可较好地实现无害化资源利用。     

Corrosion of Li-ion battery cathode materials on mullite insulation materials during calcination

A specially designed experimental device was used in laboratory to investigate the corrosion of mullite during the calcination of Li(Ni_xCo_yMn_z)O₂ (LNCM) materials. The anti-corrosion tests were carried out at 1000, 1100, 1200 and 1300 °C, and characterized with X-ray diffraction and scanning electron microscopy. The influence of temperature on the interactions between mullite insulation materials and LNCM materials was determined. In addition, the high-temperature creep properties of the mullite insulation materials before and after corrosion were tested. The laboratory scale tests, thermodynamic and kinetic calculations allowed a more comprehensive understanding of the evolution of the mullite insulation materials during serving for the roasting process of LNCM materials. Through this research, it is suggested that the upgrading of the kiln lining in the lithium battery industry should select materials with excellent resistance to alkali corrosion, especially excellent resistance to Li⁺ corrosion.     

Pure CuBi2O4 Photoelectrodes with Increased Stability by Rapid Thermal Processing of Bi2O3/CuO Grown by Pulsed Laser Deposition

A new method for enhancing the charge separation and photo‐electrochemical stability of CuBi₂O₄ photoelectrodes by sequentially depositing Bi₂O₃ and CuO layers on fluorine‐doped tin oxide substrates with pulsed laser deposition (PLD), followed by rapid thermal processing (RTP), resulting in phase‐pure, highly crystalline films after 10 min at 650 °C, is reported. Conventional furnace annealing of similar films for 72 h at 500 °C do not result in phase‐pure CuBi₂O₄. The combined PLD and RTP approach allow excellent control of the Bi:Cu stoichiometry and results in photoelectrodes with superior electronic properties compared to photoelectrodes fabricated through spray pyrolysis. The low photocurrents of the CuBi₂O₄ photocathodes fabricated through PLD/RTP in this study are primarily attributed to their low specific surface area, lack of CuO impurities, and limited, slow charge transport in the undoped films. Bare (without protection layers) CuBi₂O₄ photoelectrodes made with PLD/RTP shows a photocurrent decrease of only 26% after 5 h, which represents the highest stability reported to date for this material. The PLD/RTP fabrication approach offers new possibilities of fabricating complex metal oxides photoelectrodes with a high degree of crystallinity and good electronic properties at higher temperatures than the thermal stability of glass‐based transparent conductive substrates would allow.     

Microstructure of mayenite 12CaO·7Al2O3 and electron emission characteristics

Electron emission characteristic, electrical conductivity of polycrystalline mayenite (12CaO·7Al₂O₃) electride, formation of [Ca₂₄Al₂₈O₆₄]⁴⁺(e⁻)₄ framework as a function of phase content, and microstructure have been investigated. The mayenite microstructure was investigated using high-resolution transmission microscopy which revealed the type cage structure of 12CaO·7Al₂O₃ partially filled by extra-framework oxygen ions. Incorporation of electrons by means of carbon ion template 12CaO·7Al₂O₃ produces complex structure, and an incomplete ion template 12CaO·7Al₂O₃ structure consisting of mixture of a [Ca₂₄Al₂₈O₆₄]⁴⁺(e⁻)₄ and [Ca₂₄Al₂₈O₆₄]⁴⁺(O²⁻)₂ framework had a direct effect on the electron emission. Surface chemistry and stability of the 12CaO·7Al₂O₃ electride have been studied using x-ray photoelectron spectroscopy. The work function of phase pure 12CaO·7Al₂O₃ electride was determined from direct thermionic emission data and compared to the measurement from ultraviolet photoelectron spectroscopy (UPS). Depending on the extent of ion template of 12CaO·7Al₂O₃ structure, a work function of 0.9–1.2 eV and 2.1–2.4 eV has been measured and thermionic emission initiating at 600°C.     

Interactions of Li2O volatilized from ternary lithium-ion battery cathode materials with mullite saggar materials during calcination

In recent years, the rapid development of Li(Ni_xCo_yMn_1-x-y)O₂ (LNCM) materials for application in ternary lithium-ion batteries has led to an increased demand for refractory kiln saggars in industries. However, saggars used for firing ternary Li-ion battery cathode materials are often subjected to severe corrosion and spalling. To investigate the damage mechanism of the saggar materials, non-contact corrosion experiments were designed to study the effects of the precursor additions, calcination temperature, and number of calcinations during the interaction between mullite saggar and LNCM materials. The phase composition and microstructure of the mullite saggar specimens before and after corrosion were characterized using X-ray diffraction and scanning electron microscopy, respectively, to obtain a comprehensive understanding of the causes of the deterioration of mullite saggar materials during corrosion.     

Investigation of Ce0.9Gd0.1O2-δ dispersed Sm1.5Sr0.5NiO4+δ: Cathode for intermediate temperature solid oxide fuel cell applications

Dispersion of nanocrystalline (94–350 nm) Ce_0.9Gd_0.1O_2-δ in superfine (260–312 nm) Sm_1.5Sr_0.5NiO_4+δ using modified precipitation technique is established using X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. Presence of Ce_0.9Gd_0.1O_2-δ grains inhibits grain growth of Sm_1.5Sr_0.5NiO_4+δ, which provides morphological stability (up to 1100 °C). Ce_0.9Gd_0.1O_2-δ concentration dependent behaviours of ionic conductivity, surface exchange rate and electrode polarization resistance (R_p) of composites (determined using electrochemical impedance spectroscopy) are comprehended using percolation model. Three oxygen reduction reaction mechanisms are considered to understand electrochemical performance. Minimum R_p (0.81 Ω cm² at 700 °C) for 70Sm_1.5Sr_0.5NiO_4+δ:30Ce_0.9Gd_0.1O_2-δ is correlated to percolation threshold (optimum (i) electrochemically active sites (ii) oxygen reduction reaction kinetics, (iii) O^2- conductivity and (iv) charge transfer rate). Nano crystallite size of Ce_0.9Gd_0.1O_2-δ is crucial for enhancement in electrochemical performance. Oxygen partial pressure dependent electrochemical impedance spectroscopy studies reveal dominance of coexisting non-charge transfer oxygen adsorption/desorption and bulk O^2- diffusion.     

Synergistic effect of bulk phase doping and layered-spinel structure formation on improving electrochemical performance of Li-Rich cathode material

In this study, La was doped into the lithium layer of Li-rich cathode material and formed a layered-spinel hetero-structure. The morphology, crystal structure, element valence and kinetics of lithium ion migration were studied by field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The La doped lithium-rich cathode material exhibited similar initial discharge capacity of 262.8 mAh g^?1 at 0.1 C compared with the undoped material, but the discharge capacity retention rate can be obviously improved to 90% after 50 cycles at 1.0 C. Besides that, much better rate capability and Li⁺ diffusion coefficient were observed. The results revealed that La doping not only stabilized the material structure and reduced the Li/Ni mixing degree, but also induced the generation of spinel phase to provide three-dimensional diffusion channels for lithium ion migration. Moreover, the porous structure of the doped samples also contributed to the remarkable excellent electrochemical performance. All of these factors combined to significantly improve the electrochemical performance of the material.     

An experimental study for optimizing the energy efficiency of a proton exchange membrane fuel cell with an open-cathode

To develop an operating strategy for maximizing the energy efficiency of open-cathode proton exchange membrane fuel cells (OCPEMFCs), the present study investigates the effect of the fan speed on the stack performance and energy efficiency using a commercially available OCPEMFC system. The temperature, voltage, and current of the stack are monitored, and the energy efficiency is calculated at various stack power levels. The results of the system with a lab-developed controller are compared with the commercial system with a built-in controller. It is found that the fan speed should be minimum to reduce the auxiliary power consumption and that the stack should be efficiently heated to enhance the electrochemical reaction. In addition, it is noticed that the stack performance dramatically drops when the stack temperature is above 75 °C, due to the membrane dehydration. Overall, the results show that the stack temperature is an important indicator for controlling the fan speed for optimization of energy efficiency, and for stack powers of 50, 60, 70, and 80 W, the peak values of energy efficiencies are 38.0%, 38.3%, 38.5%, and 38.3% at the duty cycles of 0.2, 0.2, 0.25, and 0.3, respectively, which are 28–38% higher than the commercially available OCPEMFC system.