钛酸锂电池胀气程度与循环性能的关系研究

尖晶石型钛酸锂电池以其优良的倍率性能和循环性能受到广泛应用，但是其胀气问题严重制约着电池的发展，尤其在高温下胀气更加严重。为解决该问题，选取3种商用的钛酸锂软包电池为实验对象，在高温条件下进行充放电循环，并用自行设计的电池胀气体积测试装置测试电池的胀气体积，结果表明当电池容量保持率为80％时，1号和2号电池循环至1500次、而3号电池循环至1000次，且对应的电池胀气率分别为43．05％、13．46％、46．55％。在整个充放电循环过程中，对电池胀气率散点进行拟合，1号和2号电池的胀气率均呈线性增长，且1号电池增长速率大于2号电池，而3号电池胀气率呈二次函数增长。通过对电池的容量衰减率和胀气率的分析，发现电池的容量衰减率随着胀气率的增大而增大。交流阻抗测试对循环前后的钛酸锂电池测试分析表明，电池的胀气率越高，则电池的欧姆阻抗越大，2者呈线性规律；而只有当电池胀气率达到一定程度时电池的电化学阻抗才会有较大变化；胀气率对扩散阻抗的影响存在一个上限。

Effects of MgO additive on metallurgical properties of fluxed-pellet

As a main charging burden of blast furnace(BF)ironmaking process,pellets play an important role in ironmaking process.However,compared with sinters,there are some inevitable disadvantages for traditional acid pellets,e.g.,reduction swell,low melting temperature.Therefore,the fluxed-pellets have been applied in BF,especially MgO-fluxed pellets.In the present study,the effects of category and content of MgO bearing additive on the compressive strength(CS),reduction swelling index(RSI),reduction disintegration index(RDI)and melting-dripping properties of the pellets were investigated.Minerals composition,pore distribution and microstructure of MgO-flux pellets were studied by X-ray powder diffraction(XRD),mercury intrusion method and scanning electron microscopy(SEM),respectively.The results show that the light burned magnesite(LBM)is more suitable MgO bearing additive for fluxed-pellets.With increasing LBM content from 0 to 2.0%,the CS decreases from 3066 to 2689 N,RSI decreases from 16.43%to 9.97%and RDI decreases from 19.2%to 12.99%.The most appropriate MgO bearing additive content in the fluxed-pellets is 2.0%according to principal component analysis(PCA).

Coal matrix deformation characteristics in the process of carbon dioxide displacing different gas saturation coal-bed methane

It is fundamental that changes in coal reservoir permeability are researched, in particular, the accurate determination of variations in the coal matrix caused by CO2 replacing CH4 at different gas saturation conditions. Based on the surface free energy, the extended Langmuir isothermal adsorption model, combined with CO2 replacing CH4 in experimental trials, and calling on the more general principles and characteristics of the field, mathematical models describing the coal matrix as it undergoes different processes such as CO2 injection and desorption were established. Combined with laboratory data about CO2 replacement under different methane saturation conditions, a law governing the variations in coal matrix CO2 replacement under different methane gas saturation conditions was obtained. The results showed that： in the injection process, the coal matrix expansion rate caused by CO2 or CH4 was exponentially increased with the CO2 pressure increase, the expansion caused by CO2 was far greater than the expansion caused by CH4 in the desorption process, the coal matrix shrinkage caused by CO2 or CH4 was exponentially increased with the pressure decrease, the shrinkage caused by CO2 was larger than the shrinkage caused by CH4 under the same pressure and different gas saturation, the total shrinkage in the desorption process in the coal matrix was greater than the total expansion in the injection process. At higher gas saturations, the total coal matrix shrinkage volume exceeded the total expansion corresponding to pressure points higher in the desorption process.

A Novel Technology for Generation of Electricity and Cold by Using Energy Potential of Transmission Line＇s High Pressure Gas

The main objective of this paper is to develop a novel technology for combined generation of electricity and cold by using energy potential of transmission line＇s high pressure gas. For this purpose, the reduction of high pressure of the gas in gas distribution station instead of useless expansion throttling process is suggested to realize by adiabatic expansion, which is executed in a gas expanding turbine. Herewith, the gas distribution station is turned into energy and cold generating plant. Simultaneous operation of energy and cold generating plant is described. A method and appropriate formulas for determination of design characteristics of considered plant are suggested. A new method for reveres order of calculation and design of the cold store based on the use of expanded cold gas as cooling agent is developed. Calculations and analysis prove high energy efficiency of suggested technology, the wide use of which will provide significant production of cheap electricity and cold and as well as reduction of fossil fuel consumption.

Methane adsorption-induced coal swelling measured with an optical method

In order to quantify the effect of matrix shrinkage on reservoir permeability during coalbed methane production, coal samples from Huozhou, Changzhi and Jincheng areas in Shanxi province （classified as high-volatile bituminous coal, low-volatile bituminous coal and anthracite, respectively） were collected, and adsorption-induced coal swelling in methane were determined by an optical method at 40 ℃ and pressure up to 12 MPa. All three coals showed similar behavior-that swelling increased as a function of pressure up to about 10 MPa but thereafter no further increase in swelling was observed. Swelling in the direction perpendicular to the bedding plane is greater than that parallel to the bedding plane, and the differences are about 7.77-8.33%. The maximum volumetric swelling ranges from 2.73% to 3.21 %-increasing with increasing coal rank. The swelling data can be described by a modified DR model. In addition, swelling increases with the amount of adsorption. However, the increase shows a relatively slower stage followed by a relatively faster stage instead of a linear increase. Based on the assumption that sorption-induced swelling/shrinkage of coal in methane is reversible, the permeability increases induced by coal shrinkage during methane desorption was analyzed, and the results indicate that the permeability change is larger for higher rank coal in the same unit of pressure depletion.

Origin of symmetry breaking in the seed-mediated growth of bi-metal nano-heterostructures

Seed-mediated growth is the most general way to controllably synthesize bimetal nano-heterostructures. Despite successful instances through trial and error were reported, the way for second metal depositing on the seed. namely whether the symmetry of resulted nano-heterostructure follows the original crystal symmetry of seed metal, remains an unpredictable issue to date. In this work, we propose that the ther- modynamic factor, i.e., the difference of equilibrium electrochemical potentials （corresponding to their Fermi levels） of two metals in the growth solution, plays a key role for the symmetry breaking of bimetal nano-heterostructures during the seed-mediated growth. As a proof-of-principle experiment, by revers- ing the relative position of Fermi levels of the Pd nanocube seeds and the second metal Au with changing the concentration of reductant （L-ascorbic acid） in the growth solution, the structure of as-prepared prod- ucts successfully evolved from centrosymmetric Pd@Au core-shell trisoctabedra to asymmetric Pd-Au hetero-dimers. The idea was further demonstrated by the growth of Ag on the Pd seeds. The present work intends to reveal the origin of symmetry breaking in the seed-mediated growth of nano-heterostructures from the viewpoint of thermodynamics, and these new insights will in turn help to achieve rational con- struction of bimetal nano-heterostructures with soecific functions.