MECHANOCHEMICAL SYNTHESIS OF TASK-SPECIFIC CONJUGATED POROUS NETWORKS TOWARDS ENHANCED ENERGY STORAGE

Conjugated scaffolds with high electronic conductivity, high surface area, etc. are promising materials for diverse technological applications, especially in the electrochemical field. However, the current synthesis methods are still limited to the traditional solution-based method or the ionothermal method, which always require an inert atmosphere shield, large amounts of organic solvents, noble catalysts, long reaction time up to days, and high temperatures, etc. Therefore, there is a common goal of developing conjugated scaffolds through facile, green, straightforward pathways. Mechanochemistry, which is an efficient, sustainable, solvent-free methodology, could provide a unique reaction environment to synthesize this kind of functionalized materials, resulting in materials that exhibit different properties from those produced by traditional methods. However, the current conjugated scaffolds derived from mechanochemistry are limited to the oxidative polymerization from the electron-rich building blocks. Herein, we extended the building blocks to the electron-deficient monomers (aromatic halides, aromatic nitriles) with various catalysts (magnesium, aluminum, zinc, calcium carbide) and achieved different conjugated porous scaffolds such as the poly(phthalocyanine), nitrogen-doped graphyne scaffolds for the enhanced energy storage including supercapacitor and alkali-ion batteries. Additionally, the mechanochemistry-driven method is not only suitable for the direct synthesis of conjugated scaffolds from small molecules but also capable of being used for the post-treatment of conjugated scaffolds for their desirable properties. For instance, the trimerization reaction of terephthalonitrile to form covalent triazine frameworks (CTF) catalyzed by triflic acid could be achieved at low temperature (250 °C) for a short time, without the undesirable carbonization reaction. However, the CTF obtained by this method tends to form the staggered stacking with low surface area due to the residual triflic acid, which is hard to remove. Mechanochemistry treatment with the alkaline molten salt composed of lithium hydroxide and potassium hydroxide at ambient temperature was proposed in this dissertation to achieve the phase transformation from the staggered stacking to eclipsed stacking with high surface area. Overall, our approach on the scenario of conjugated scaffold construction can not only expand the boundaries of conventional conjugated scaffold synthesis, but also provide new opportunities to their scalable application

The effect of hydration on pores of shale oil reservoirs in the third submember of the Triassic Chang 7 Member in Southern Ordos Basin

ABSTRACT: Shale oil is an unconventional kind of oil and gas resource with great potential. China has huge reserves of shale oil, and shale oil resources are abundant in the third submember of the Triassic Chang 7 member in the southern Ordos Basin. At present, this area is in the initial stage of shale oil exploration and development. The reservoir pore is one of the key factors affecting oil accumulation, drilling safety, and oil production. It is also an important reservoir parameter that must be defined in the exploration stage. In general, the clay content in the shale section is high, and is prone to hydration. In order to study the effect of fluid on the pore type, structure, and distribution of shale oil reservoirs, experiments using X-ray diffraction, a porosity-permeability test, mercury porosimetry, rock casting thin section, and scanning electron microscopy were carried out. The experimental results show that the content of clay and quartz is very high in the studied formation. The pore porosity and permeability of the rock is highly heterogeneous because of the obvious stratigraphic bedding and interbeds. Microstructural observation of rocks shows that the main pore types are intergranular pores, intragranular pores, intercrystalline pores, and organic pores. Crack types are dissolution cracks, contraction cracks of organic matter, and abnormal pressure structural cracks. After hydration, the porosity of rock will increase in varying degrees, and pore size, pore content in different sizes, and pore structure will also change. The results show that the pores of tuff mainly changes at the initial stage of hydration, and the pore change of tuff is the most obvious within 6 hours of soaking in clear water. The influence of hydration on the pore of shale is greater than that of tuff, but the main change stage is later than tuff, and the pore change of shale is the most obvious within 12 to 24 hours of soaking in clear water. The soaking experiment of water-based drilling fluid (WBM-SL) shows that it can plug a certain size of holes and cracks and form a protective layer on the rock surface, thus effectively reducing hydration. In actual construction, multisized solid particles should be allocated in drilling fluid according to the formation pore's characteristics, and the stability of the protective layer should be guaranteed. This can reduce the accident of well leakage and collapse and is conducive to the efficient and safe development of shale oil

Progress and future prospects of high-voltage and high-safety electrolytes in advanced lithium batteries: From liquid to solid electrolytes

Developing the next-generation high-energy density and safe batteries is of prime importance to meet the emerging demands in electronics, automobile industries and various energy storage systems. High-voltage lithium-ion batteries (LIBs) and solid-state batteries (SSBs) are two main directions attracting increasing interest in recent years, due to their potential applications in the near future. In both kinds of batteries, the electrolytes play a pivotal role but also create several bottleneck problems. In this review, recent progress in designing electrolytes for high-voltage LIBs and SSBs is summarized. First, the solvents, additives, ionic liquids and superconcentrated salts strategies for constructing high-voltage liquid electrolytes are reviewed, and then the applications of inorganic solids, solid polymers, gels and ionic liquids in solid-state electrolytes are presented. Finally, the general design rules of the electrolytes and their current limitations and future prospects are briefly discussed

2D Magnetic Manipulation of a Micro-Robot in Glycerin Using Six Pairs of Magnetic Coils

This paper demonstrates the control system of a single magnetic micro-robot driven by combined coils. The combined coils consist of three pairs of Helmholtz coils and three pairs of Maxwell coils. The rotating magnetic field, gradient magnetic field, and combined magnetic field model of the combined coils were analyzed. To make the output magnetic field quickly converge to the reference point without steady-state error, the discrete-time optimal controller was designed based on the auto disturbance rejection technology. We have designed a closed-loop controller based on a position servo. The control system includes the position control and direction control of the micro-robot. To address problems with slow sampling frequency in visual feedback and inability to feed real-time position back to the control system, a Kalman filter algorithm was used to predict the position of the micro-robot in two-dimensional space. Simulations and experiments were carried out based on the proposed structure of combined coils and control scheme. The experimental results demonstrated the uniformity and excellent dynamic performance of the generated magnetic field

Seawater carbonate chemistry and photosynthesis and dark respiration of Thalassiosira weissflogii (diatom)

Increasing atmospheric pCO2 leads to seawater acidification, which has attracted considerable attention due to its potential impact on the marine biological carbon pump and function of marine ecosystems. Alternatively, phytoplankton cells living in coastal waters might experience increased pH/decreased pCO2 (seawater alkalization) caused by metabolic activities of other photoautotrophs, or after microalgal blooms. Here we grew Thalassiosira weissflogii (diatom) at seven pCO2 levels, including habitat-related lowered levels (25, 50, 100, and 200 µatm) as well as present-day (400 µatm) and elevated (800 and 1600 µatm) levels. Effects of seawater acidification and alkalization on growth, photosynthesis, dark respiration, cell geometry, and biogenic silica content of T. weissflogii were investigated. Elevated pCO2 and associated seawater acidification had no detectable effects. However, the lowered pCO2 levels (25-100 µatm), which might be experienced by coastal diatoms in post-bloom scenarios, significantly limited growth and photosynthesis of this species. In addition, seawater alkalization resulted in more silicified cells with higher dark respiration rates. Thus, a negative correlation of biogenic silica content and growth rate was evident over the pCO2 range tested here. Taken together, seawater alkalization, rather than acidification, could have stronger effects on the ballasting efficiency and carbon export of T. weissflogii

Progress and future prospects of high-voltage and high-safety electrolytes in advanced lithium batteries: from liquid to solid electrolytes

Developing the next-generation high-energy density and safe batteries is of prime importance to meet the emerging demands in electronics, automobile industries and various energy storage systems. High-voltage lithium-ion batteries (LIBs) and solid-state batteries (SSBs) are two main directions attracting increasing interest in recent years, due to their potential applications in the near future. In both kinds of batteries, the electrolytes play a pivotal role but also create several bottleneck problems. In this review, recent progress in designing electrolytes for high-voltage LIBs and SSBs is summarized. First, the solvents, additives, ionic liquids and superconcentrated salts strategies for constructing high-voltage liquid electrolytes are reviewed, and then the applications of inorganic solids, solid polymers, gels and ionic liquids in solid-state electrolytes are presented. Finally, the general design rules of the electrolytes and their current limitations and future prospects are briefly discussed.</p

Double-Confined Sulfur Inside Compressed Nickel Foam and Pencil-Plating Graphite for Lithium-Sulfur Battery

The sulfur confined inside the interpenetrating network of compressed nickel foam we prepared and its application as a high-performance S cathode for lithium-sulfur batteries was investigated. The double confine by Ni foam and pencil-plating graphite makes the cathode high performance. The mechanical physical method was applied to prepare the S cathode at room temperature without using binder and conductive additives. The sulfur mass loading was controlled between 0.42 and 3.32 mg/cm(2) in the cathode piece. The optimized cathode of 0.42 mg/cm(2) S on Ni foam displayed high initial discharge capacity (1412 mAh/g at 1C), long cycle stability (1014 mAh/g after 100 cycles at 1C, S 1.05 mg/m(2) ), and high rate capability (495 mAh/g at 2C, S 1.15 mg/cm(2) ). This rapid, simple, one-step cathode preparation method may pave a new practical way for mass production of high-performances S cathode materials in lithium-sulfur battery technology.</p

Fluoroethylene carbonate as an electrolyte additive for improving interfacial stability of high-voltage LiNi0.6Co0.2Mn0.2O2 cathode

In this work, fluoroethylene carbonate (FEC) is used as an additive to improve the interface stability between LiNi0.6Co0.2Mn0.2O2 (NCM622) electrode and electrolyte under high voltage (4.6V vs Li/Li+). The improved cycle stability and electrochemical impedance spectroscopy (EIS) studies imply the formation of robust, uniform and less-resistive film on the surface of NCM622. The results from TEM, SEM and XPS demonstrate that FEC facilitates the formation of CEI layer, and the FEC-derived CEI protects against not only the decomposition of the electrolyte solvent but also oxidation of the NCM622 electrode