High energy density in ultra-thick and flexible electrodes enabled by designed conductive agent/binder composite

Thick electrodes can increase incorporation of active electrode materials by diminishing the proportion of inactive constituents,improving the overall energy density of batteries.However,thick electrodes fabricated using the conventional slurry casting approach frequently exhibit an exacerbated accumulation of carbon additives and binders on their surfaces,invariably leading to compromised electrochemical properties.In this study,we introduce a designed conductive agent/binder composite synthesized from carbon nanotube and polytetrafluoroethylene.This agent/binder composite facilitates production of dry-process-prepared ultra-thick electrodes endowed with a three-dimensional and uniformly distributed percolative architecture,ensuring superior electronic conductivity and remarkable mechanical resilience.Using this approach,ultra-thick LiCoO_(2)(LCO) electrodes demonstrated superior cycling performance and rate capabilities,registering an impressive loading capacity of up to 101.4 mg/cm^(2),signifying a 242% increase in battery energy density.In another analytical endeavor,time-of-flight secondary ion mass spectroscopy was used to clarify the distribution of cathode electrolyte interphase(CEI) in cycled LCO electrodes.The results provide unprecedented evidence explaining the intricate correlation between CEI generation and carbon distribution,highlighting the intrinsic advantages of the proposed dry-process approach in fine-tu ning the CEI,with excellent cycling performance in batteries equipped with ultra-thick electrodes.

柴达木盆地西部坳陷古近系全油气系统特征与油气成藏模式

基于柴达木盆地西部坳陷油气勘探实践,结合地震、钻井、测井及地球化学等资料,对柴西坳陷古近系全油气系统基本地质条件、油气分布特征、成藏运聚动力与成藏模式开展研究。研究表明:柴西坳陷发育全球独具特色的“巨厚山地式”全油气系统,围绕古近系下干柴沟组上段烃源岩层系,从盆缘向湖盆中心,平面上构造油气藏、岩性油气藏、页岩油与页岩气有序分布、纵向上叠置连片。柴西坳陷古近系全油气系统具有3方面独特性:(1)低有机质丰度烃源岩“低碳富氢”,单位有机碳生烃能力强;(2)咸化湖盆沉积巨厚,坳陷中心沉积以混源为主,岩相与储集空间纵横向变化快;(3)喜马拉雅期走滑挤压强改造,山地式全油气系统油气差异富集。柴西坳陷古近系全油气系统是源储盖与输导体系协调演化的结果,具有低碳富氢烃源岩全过程生烃、巨厚储集体全坳陷沉积、挤压走滑断裂体促进油气全方位调整、常规-非常规油气全系列分布的特征。受控于喜马拉雅期强构造运动影响,柴西坳陷经历了先拗后隆的演化过程,在湖盆中心发育广义页岩油,在超过2 000 m厚度的沉积体系中,油气连续分布于烃源岩层系内的薄层状灰云岩与紧邻生烃灶的藻灰岩中,白云石晶间孔、纹层缝与断溶体是有效储集空间。相关认识可进一步丰富和发展中国陆相湖盆全油气系统理论,并为柴达木盆地油气综合勘探提供理论指导与技术支持。

Key technologies and equipment for a fully mechanized top-coal caving operation with a large mining height at ultra-thick coal seams

Thick and ultra-thick coal seams are main coal seams for high production rate and high efficiency in Chinese coal mines, which accounts for 44 % of the total minable coal reserve. A fully mechanized top-coal caving mining method is a main underground coal extraction method for ultra-thick coal seams. The coal extraction technologies for coal seams less than 14 m thick were extensively used in China. However, for coal seams with thickness greater than 14 m, there have been no reported cases in the world for underground mechanical extraction with safe performance, high efficiency and high coal recovery ratio. To deal with this case, China Coal Technology ＆ Engineering Group, Datong Coal Mine Group, and other 15 organizations in China launched a fundamental and big project to develop coal mining technologies and equipment for coal seams with thicknesses greater than 14 m. After the completion of the project, a coal extraction method was developed for top-coal caving with a large mining height, as well as a ground control theory for ultra-thick coal seams. In addition, the mining technology for top-coal caving with a large mining height, the ground support technology for roadway in coal seams with a large cross-section, and the prevention and control technology for gas and fire hazards were developed and applied. Furthermore, a hydraulic support with a mining height of 5.2 m, a shearer with high reliability, and auxiliary equipment were developed and manufactured. Practical implication on the technologies and equipment developed was successfully completed at the No. 8105 coal face in the Tashan coal mine, Datong, China. The major achievements of the project are summarized as follows： 1. A top-coal caving method for ultra-thick coal seams is proposed with a cutting height of 5 m and a top-coal caving height of 15 m. A structural mechanical model of overlying strata called cantilever beam-articulated rock beam is established. Based on the model, the load resistance of the hydraulic support with a large mining height for top-coal caving method is determined. With the analysis, the movement characteristics of the top coal and above strata are evaluated during top-coal caving operation at the coal face with a large mining height. Furthermore, there is successful development of comprehensive technologies for preventing and controlling spalling of the coal wall, and the top-coal caving technology with high efficiency and high recovery at the top-coal caving face with a large mining height. This means that the technologies developed have overcome the difficulties in strata control, top-coal caving with high efficiency and high coal recovery, and enabled to achieve a production rate of more than 10 Mtpa at a single top-coal caving face with a large mining height in ultra-thick coal seams; 2. A hydraulic support with 5.2 m supporting height and anti-rockburst capacity, a shearer with high reliability, a scraper conveyor with a large power at the back of face, and a large load and long distance headgate belt conveyor have been successfully developed for a top-coal caving face with large mining height. The study has developed the key technologies for improving the reliability of equipment at the coal face and has overcome the challenges in equipping the top-coal caving face with a large mining height in ultra-thick coal seams; 3. The deformation characteristics of a large cross-section roadway in ultra-thick coal seams are discovered. Based on the findings above, a series of bolt materials with a high yielding strength of 500-830 MPa and a high extension ratio, and cable bolt material with a 1 × 19 structure, large tonnage and high extension ratio are developed. In addition, in order to achieve a safe roadway and a fast face advance, installation equipment for high pre-tension bolt is developed to solve the problems with the support of roadway in coal seams for top-coal caving operation with a large mining height; 4. The characteristics of gas distribution and uneven emission at top-coal caving face with large mining height in ultra-thick coal seams are evaluated. With the application of the technologies of gas drainage in the roof, the difficulties in gas control for high intensive top-coal caving mining operations, known as ＂low gas content, high gas emission＂, are solved. In addition, large flow-rate underground mobile equipment for making nitrogen are developed to solve the problems with fire prevention and safe mining at a top-coal caving face with large mining height and production rate of more than 10 Mtpa. A case study to apply the developed technologies has been conducted at the No. 8105 face, the Tashan coal mine in Datong, China. The case study demonstrates that the three units of equipment, i.e., the support, shearer and scraper conveyor, are rationally equipped. Average equipment usage at the coal face is 92.1%. The coal recovery ratio at the coal face is up to 88.9 %. In 2011, the coal production at the No. 8105 face reached 10.849 Mtpa, exceeding the target of 10 Mtpa for a topcoal caving operation with large mining height performed by Chinese-made mining equipment. The technologies and equipment developed provide a way for extracting ultra-thick coal seams. Currently, the technologies and equipment are used in 13 mining areas in China including Datong, Pingshuo, Shendong and Xinjiang. With the exploitation of coal resources in Western China, there is great potential for the application of the technologies and equipment developed.

Subsidence control method by inversely-inclined slicing and upward mining for ultra-thick steep seams

Ultra-thick steep coal seam mining will inevitably lead to the increase of greater and violent ground subsidence and deformation.A subsidence control method by inversely-inclined slicing and upward mining is proposed in this paper.By this method,the sequence of collapse of overlying strata and the direction of propagation of strata movement are changed,the extent of roof-side deformation thereby is lessened,and boundary angle of roof-side subsidence is reduced by 5°-10°.The mechanism of this mining method for control of strata movement has been evidenced by numerical simulation and experiments with similarity materials.A subsidence prediction model based on the variation of mining influence propagation angle can be used to evaluate the surface movement and deformation of the mining method.The application of the method in No.3 Mine in Yaojie mining area has yielded the expected result.

Comparative study of mining methods for reserves beneath end slope in flat surface mines with ultra-thick coal seams

The paper aims to identify a reasonable method for mining ultra-thick coal seams in an end-slope in surface mine, With a case study of Heidaigou surface coal mine(HSCM), the paper conducted a comparative research on three mining methods, namely Underground Mining Method(UMM), Highwall Mining System(HMS) and Local Steep Slope Mining Method(LSSMM). A model was firstly established to simulate the impact that UMM and HMS exert on monitoring points and surface deformation. The way that stripping and excavation amount varies with different slope angle, and the corresponding end slope stability were analyzed in the mode of LSSMM. Then a TOPSIS model was established by taking into account six indicators such as recovery ratio, technical complexity and adaptability, the impact on surface mining production, production safety and economic benefits. Finally, LSSMM was determined as the best mining method for mining ultra-thick coal seams in end slope in HSCM.

Suitable layout of gate roads related to slice mining in an ultra-thick unstable coal seam

We determi：ned a suitable gate road layout in slice mining in an ultra-thick unstable coal seam, using theoretical anallysis and numerical calculations. Based on plasticity theory in terms of limiting equilibrium, the width of chain pillar in the upper slice was calculated to be 18 m. The stress distribution in the chain pillar after the upper slice was mined out was described with numerical simulation. The extent of the effect of stress on the upper chain pillar on the lower solid coal was obtained on the basis of an elastic solution of a distributed force loaded on a half-plane. Three layout designs for lower gate roads were pro- posed and a stability factor was introduced to analyze the stability of the lower pillar with numerical calculation. Gate road translation was determined as the most suitable layout method, which maximizes the extraction rate on the basis of the pillar stability.

An empirical model for high energy density lithium-(ion)batteries with ultra-thick electrodes

Increasing the electrode thickness is a significant method to decrease the weight and volume ratio of the inactive components for high energy density of the devices.In this contribution,we extracted a repeating unit in the configurations and establish the empirical energy density model based on some assumptions.In this model,the effects of the electrode thickness on the energy density for lithium-ion batteries(LIBs),lithium metal batteries(LMBs),and anode-free lithium batteries(ALBs)are evaluated quantitively with the current parameters of the batteries.The results demonstrate that the structure evolutions from LIBs,LMBs to ALBs with the reduction of the anode weight contribution,the energy density can be well improved exactly.While the increase of the thickness of the electrode provide another route to furthe r enhance the energydensity by decreasing the weight contribution of inactive materials;meanwhile the effects for ALBs are higher than LMBs and LIBs due to the higher weight ratio of inactive materials.This empirical energy density model is also applied into the practical system and provide intuitional results to guide the battery design for higher energy density.

Effect of Post-weld Heat Treatment on the Microstructure and Mechanical Properties of 2.25Cr-1Mo-0.25V Ultra-Thick Steel Plate

Ensuring the homogeneous and excellent mechanical properties of 2.25Cr-1Mo-0.25V ultra-thick steel plate is the key to the production of hydrogenation reactor equipment.Thus,it is required to understand the heterogeneity of microstructures and properties of ultra-thick plate after heat treatment.In this work,the effect of post-weld heat treatment(PWHT)on the strength,plasticity,toughness and microstructures of the 193-mm-thick steel plate was investigated,and the formation mechanism of heterogeneity was elucidated.The PWHT decreased the room-and high-temperature yield strength(YS)and ultimate tensile strength(UTS)of the steel plate after normalizing and tempering(NT),while the room-and high-temperature YS and UTS decreased from the surface to the center of 193-mm-thick steel plate.It was attributed to the enhanced decomposition of martensite-austenite(M-A)constituents and coarsening of grains and precipitated carbides.

Study on the mechanism of rapid formation ofu ultra-thick tribofilm by CeO_(2)nano additive and ZDDP

CeO_(2)nanoparticles are potential anti-wear additives because of their outstanding anti-wear and load-bearing capacity.However,the shear-sintering tribo-film formation mechanism of oxide nanoparticles limits the tribo-film formation rate and thickness greatly.In this study,by compounding with zinc dioctyl dithiophosphate(ZDDP),ultra-fine CeO_(2)nanoparticles modified with oleylamine(OM)can quickly form 2μm ultra-thick tribo-film,which is 10-15 times thicker than that of ZDDP and CeO_(2),respectively.The ultra-thick tribo-film presents a nanocomposite structure with amorphous phosphate as binder and nano-CeO_(2)as filling phase,which leads to the highest loading capacity of composite additives.The results of adsorption experiments tested by dissipative quartz crystal microbalance(QCM-D)showed that the Ps value of additive has nothing to do with its equilibrium adsorption mass,but is directly proportional to its adsorption rate in 10 s.The compound additive of CeO_(2)and ZDDP presented the co-deposition mode of ZDDP monolayer rigid adsorption and CeO_(2)viscoelastic adsorption on the metal surface,which showed the highest adsorption rate in 10 s.It is found that the tribo-film must have high film forming rate and wear resistance at the same time in order to achieve super thickness.Cerium phosphate was formed from ZDDP and CeO,through tribochemistry reaction,which promotes the formation of an ultra-thick tribo-film with nanocomposite structure,which not only maintains the low friction characteristics of CeO,but also realizes high Pg and high load-carrying capacity.

Activation and self-repairing effectiveness of lubrication with nano-tin as additives

Micron grade Sn powder, VG32 oil and active pharmaceutical were mixed and the Nanometer Sn lubricant additives were prepared. Nanometer additives with different Sn concentrations were used in Steel-brass Tribo-pair for friction and wear test. The activating method to nano-Sn and surface of brass samples was investigated, and the method to form relatively thick friction coating on samples was discussed. Surface elemental distribution, coating thickness and its surface appearance were analyzed with X-ray photoelectron spectrum （XPS）, auger electron spectrum （AES） and scanning electron microscope （SEM） respectively. The result shows that the ultra-thick friction coating （approx 20 μm）, with abundant tin and well combined with substrate, has formed on the brass sample. The friction coating revealed superior performance of friction reducing and antiwear properties. Therefore, the results possess practical significance to self-repair usage on steel-brass tribo-pair in mechanical systems.

Microstructure and mechanical properties of double-side friction stir welded 6082Al ultra-thick plates

In the present work,80 mm thick 6082Al alloy plates were successfully double-side welded by friction stir welding(FSW).The relationship between the microstructures and mechanical properties was built for the double-side FSW butt joint with more attention paid to the local characteristic zones.It was shown that a phenomenon of microstructural inhomogeneity existed in the nugget zone(NZ)through the thickness direction.The grain size presented an obvious gradient distribution from the top to the bottom for each single-pass weld,and the microhardness values decreased from both surfaces to the middle of the NZ.The lowest hardness zone(LHZ)exhibited a"hyperbolical"-shaped distribution extending to the middle of the NZ.Similar tensile properties were obtained in the three sliced specimens of the FSW joint,and the joint coefficient reached about 70%which achieved the same level as the conventional FSW Al alloy joints.Finite element modeling proved that the"hyperbolical"-shaped heat affected zone(HAZ)was beneficial to resisting the strain concentration in the middle layer specimen which helped to increase the tensile strength.Based on the analysis of the hardness contour map,tensile property and microstructural evolution of the joints,an Isothermal Softening Layer(ISL)model was proposed and established,which may have a helpful guidance for the optimization on the FSW of ultra-thick Al alloy plates.

Application and Numerical Simulation of Electromagnetic Stirring in Secondary Cooling Zone During Continuous Casting of Ultra-Thick Slab

The segregation of solute elements at solidification front could be greatly improved by application of electromagnetic stirring(SEM)in secondary cooling zone.The location of SEM in secondary cooling zone affects the operational effect.In the present study,based on the application of SEM in Ultra-thick slab continuous casting,the shell thickness was calculated by self-programming code and the results were verified by nail-shooting test.A numerical model was established to calculate the fluid flow of molten steel under shell to determine the suitable SEM location in secondary cooling zone.The results shows that the velocity of molten steel increases with increase of stirring current which enhance the circulatory flow of unset steel at solidification front.Whereas,in order to fully develop ability of SEM it is necessary to select suitable stirring current and mode for ultra-thick slab casting.This calculation provides theoretical base for application of SEM in secondary cooling zone during ultra-thick slab casting process.