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Xiang Ming He Jian Jun Li Yan Cai Yaowu Wang Jierong Ying Changyin Jiang Chunrong Wan 《Journal of Solid State Electrochemistry》2005,9(6):438-444
A novel process is proposed for synthesis of spinel LiMn2O4 with spherical particles from the inexpensive materials MnSO4, NH4HCO3, and NH3H2O. The successful preparation started with carefully controlled crystallization of MnCO3, leading to particles of spherical shape and high tap density. Thermal decomposition of MnCO3 was investigated by both DTA and TG analysis and XRD analysis of products. A precursor of product, spherical Mn2O3, was then obtained by heating MnCO3. A mixture of Mn2O3 and Li2CO3 was then sintered to produce LiMn2O4 with retention of spherical particle shape. It was found that if lithium was in stoichiometric excess of 5% in the calcination of spinel LiMn2O4, the product had the largest initial specific capacity. In this way spherical particles of spinel LiMn2O4 were of excellent fluidity and dispersivity, and had a tap density as high as 1.9 g cm–3 and an initial discharge capacity reaching 125 mAh g–1. When surface-doped with cobalt in a 0.01 Co/Mn mole ratio, although the initial discharge capacity decreased to 118 mAh g–1, the 100th cycle capacity retention reached 92.4% at 25°C. Even at 55°C the initial discharge capacity reached 113 mAh g–1 and the 50th cycle capacity retention was in excess of 83.8%. 相似文献
23.
A theory is developed for the potential distribution around a charged spherical colloidal particle carrying ionized groups on the particle surface in a medium containing its counterions (i.e., counterions produced from dissociation of the particle surface groups) and a small amount of added salts on the basis of the theory of Imai and Oosawa. Numerical solutions to the Poisson–Boltzmann equation for the potential distribution are obtained for the case of dilute (but not infinitely dilute) particle suspensions of volume fraction 1 for
a1 (where is the Debye–Hückel parameter and a is the particle radius). Here we have taken into account the effects of (i) counterions from the particle surface groups, and (ii) the finite particle volume fraction. These effects, which are usually neglected in the conventional Poisson–Boltzmann equation, are found to be important. It is found that, as in the case of completely salt-free media, there is a certain critical value of the particle charge (which is the same as that for the completely salt-free case). When the particle charge is lower than the critical value, the potential is given by a Coulomb potential. If the particle charge is higher than the critical value, then counterions are accumulated in the vicinity of the particle surface (counterion condensation) and the potential becomes less dependent on the particle charge. The above behaviors can be observed even for the case where the electrolyte concentration is higher than the concentration of counterions from the particle surface groups, if the conditions
1 and a1are both satisfied. 相似文献
24.
利用软嵌式粉末电极技术研究了Y(OH)3包覆对球形Ni(OH)2电化学性能的影响. 循环伏安结果表明, 在球形Ni(OH)2的氧化过程中存在Ni(Ⅲ)和Ni(Ⅳ)的两步氧化反应, 产生的Ni(Ⅳ)不稳定, 能分解产生NiOOH和氧气, 所以可将Ni(Ⅲ)→Ni(Ⅳ)看作副反应. Y(OH)3包覆层对Ni(OH)2氧化过程后期的副反应, 特别是Ni(Ⅲ)→Ni(Ⅳ)具有较好的抑制作用. 由包覆后的Ni(OH)2制成的模拟电池表现出很好的高温性能, 在1C充放电条件下, 当Y的摩尔分数为1.61%时, 在60 ℃时所对应的容量保持率可达到25 ℃的92.7%; 当Y的摩尔分数仅为0.55 %时, 在60 ℃时所对应的质量比容量也可达到241.3 mA·h/g. 相似文献
25.
《Electroanalysis》2004,16(11):938-948
The theory for an EC mechanism in chronopotentiometric techniques – reversal chronopotentiometry, cyclic chronopotentiometry and reciprocal derivative chronopotentiometry – is developed. The equations of this article are valid for spherical electrodes of any size and present a compact and easy‐to‐manage form. Methods for determining kinetic parameters of the chemical reaction are proposed and the influence of the electrode radius is discussed. We conclude that large errors in the determination of these parameters are committed if electrode sphericity is neglected. Reciprocal derivative chronopotentiometry has been applied in its traditional form (dt/dE vs. E), and in a more recently proposed modality consisting of plotting dt1/2/dE vs. E. These techniques are very convenient for studying an EC mechanism since the response is obtained in the form of peaks which are quantitatively related to the kinetic parameters of the chemical reaction. A comparison of the chronopotentiometric methods analyzed leads us to conclude that working curves based on the dt1/2/dE vs. E curves are more suitable to obtain accurate values of the rate constants of the chemical reaction. 相似文献
26.
In this paper we investigate two-point algebraic-geometry codes (AG codes) coming from the Beelen-Montanucci (BM) maximal curve. We study properties of certain two-point Weierstrass semigroups of the curve and use them for determining a lower bound on the minimum distance of such codes. AG codes with better parameters with respect to comparable two-point codes from the Garcia-Güneri-Stichtenoth (GGS) curve are discovered. 相似文献
27.
We prove two new upper bounds on the size of binary codes with a minimum distance of three, namelyA(10, 3)76 andA(11, 3)152. 相似文献
28.
It is shown how to represent algebraically all functions that have a zero sum on all -dimensional subspaces ofPG(n,q) or ofAG(n,q). In this way one can calculate the dimensions of related codes, or one can represent interesting sets of points by functions. 相似文献
29.
反相液相色谱用球形共聚物柱填料 总被引:2,自引:0,他引:2
采用新颖聚合工艺制备用于反相高效液相色谱柱填料的乙基苯乙烯-二乙烯苯球形共聚物,不需使用备有高速搅拌的混匀器和特殊的筛析设备,聚合物粒径的95%在3~7μm之间,测算了渗透性、柱效和峰不对称性等柱参数,并通过分离实例说明该填料对胺类、酚类和芳烃类具有优良分离性能。 相似文献
30.