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库仑效率接近90%.金属锡电极的不可逆容量一般是由固体/电解质相界面膜(SEI)的形成和电解液的分解引起的[17-19].由不同电沉积层的SEM像(见图1)可知,锡电极S1为具有高比表面积的网状多孔结构,这会引起大面积SEI膜的形成和较大量电解液的分解,从而导致S1电极在初始电化学循环过程中高的不可逆容量.而活性物质锡较低的结晶度,不同颗粒之间以及颗粒与基体之间较差的电接触[17],则导致S1电极...第一次放电(嵌锂)容量为950 mA?h/g,接近理论容量,第一次充电(脱锂)容量为500 mA?h/g,库仑效率为53%;在第二次循环放电(嵌锂)曲线中出现了1.20~1.10 V,0.50~0.35 V和0.30~0.20 V 3个电压平台,对应于金属锡的不同嵌锂阶段,在1.4 V附近不太明显的电压平台可能起源于SEI膜的形成[19].S2电极第二次循环的库仑效率为82%,之后库仑效率保持在......
/deintercalation process depend strongly on the carbon morphology. The irreversible capacity loss associated with the formation of the protective solid-electrolyte interface (SEI) layer varies... react with electrolytes and Li+ ions to produce compact and stable SEI film, the electrochemical performance of anode is related closely to the fractions of ECA and SCA in graphite. So it is necessary......
voltammograms of Sn film electrode Sn oxide formed in air. The solid electrolyte interface (SEI) layer cannot be formed on the oxide. The insertion of lithium ions takes place quickly after the reduction of Sn oxide and large current appears at the potential lower than 0.5 V. In the second cycle, the current for the SEI formation can be observed from 1.7 V to 1.1 V in negative sweep. Several......
in the inset of Fig. 2(a), where Re represents the ohmic resistance of the cell, Rsf is the SEI film resistance and CPE1 is the corresponding capacitance to Rsf, Rct is the charge-transfer resistance, CPEdl... is mainly generated from the resistance and capacitance of the SEI. In the middle-frequency range, the semicircle resembles the charge-transfer resistance, and the linear section in the low-frequency......
the first charge process, which forms a thin passive film on the surface of carbon anode of Li-ion battery called solid electrolyte interphase (SEI) or SEI layer[1]. A stable and dense SEI layer can prevent further reaction between electrolyte and carbon anode, while an unstable and loose SEI layer cannot prevent solvation Li+ or organic solutions from passing through, finally leading......
structure carbon anode used in Li ion battery and the LiB compound. In the Li ion battery, there is a SEI (solid electrolyte interface) film forming on the surface of the anode, which can prevent the co-intercalation of the solvent molecule into the crystal of the graphite with the Li ion[15]. For the experiment here, the electrochemical reactions also takes place at the potential below 0.8 V, the SEI......
表面积而引起的. 2.2 复合材料,CMS和AC的电化学性能 图3 所示为复合材料,CMS和活性炭的首次充放电曲线.从图3可以看出:活性炭的首次放电容量为911 mA?h/g,而CMS 和复合材料的首次放电容量分别为336和549 mA?h/g.CMS的首次充放电曲线如图3所示,放电容量主要由在0.7 V附近形成固体电解质中间相(SEI)的容量以及0.2 V左右的嵌锂容量组成.活性炭的首次放电容量主要由形成SEI膜的容量和双电层的容量2个部分组成. 活性炭具有很大比表面积,所以,形成SEI膜会产生较大的容量[12].同时双电层的形成也会产生放电容量.活性炭不具有石墨的层状结构,因此,放电过程中没有嵌锂容量,主要表现为曲线上没有明显的嵌锂平台.另外,在活性炭充电曲线上明显存在由内阻引起的压降,表明此时活性炭容量主要由电化学双电层引起.由图3中曲线2可见:复合材料在0.2 V附......
A?h/g以上,但仍低于其理论容量4.20 A?h/g,并且其容量衰减很快;在第3次循环结束时,容量衰减为原来的52.8%;在充放电循环中,纯硅电极中的硅体积在嵌锂和脱锂的过程中会发生很大变化,破坏电极表面形成的SEI膜(Solid electrolyte interface,固体电解质界面膜)[19].为此,循环过程中将不断有新的表面裸露,重新生成SEI膜,造成不可逆容量的损  ...~0.2 V范围内出现1个表征电极表面与电解液发生还原反应,生成SEI膜[19]的电位平台.这是由于经过球磨的材料的比表面积较大,且产生了高点化学活性的结构缺陷[20],在首次充电时需要消耗更多的锂离子在电极表面生成SEI膜,这一不可逆过程将导致较大的不可逆容量.而B电极进行首次充放电且电位为0.7~0.2 V时,出现了1个更加平缓的还原反应平台.这是由于B物料中含有除了Si和Fe元素以外的Al等其他......
composite ceramics with different annealing processes 3.2 Microstructure The SEI micrographs of the Si3N4-AlN composite ceramics with different annealing times at 1 850 °C and 1 450 °C are shown..., the increase of bending strength could be explained by the crystallization of glassy phase to La2Si6N8O3, which was promoted by extended annealing time. Figure 5 shows the SEI micrograph......
练序列,可提高传输效率,在水声通信中得到广泛应用.恒模算法(CMA)因其性能稳健和易于实现,成为研究热点.但是,CMA算法只利用信号的幅度信息,对于相位信息而言是盲的,当信道对信息产生固定相移,均衡器的输出端会造成误判.而修正的恒模算法(MCMA)隐含地使用锁相环,可以同时完成盲均衡和载波相位恢复,但收敛速度较慢,稳态均方误差也较大.超指数盲均衡迭代(SEI)算法具有较快的收敛速度,但稳态误差较大...声序列;,为前馈均衡器输入递归向量,经判决器Qu后,得到原发射信号s(k)的估计值;,为反馈均衡器输入递归向量;为无记忆非线性函数;e(k)为盲均衡误差项.前馈滤波器输出 ,反馈滤波器输出,判决器输入. 1.2 快速收敛载波恢复修正的超指数迭代算法 与CMA算法相比,SEI算法在权向量每次迭代时计算均衡器输入信号自相关矩阵的逆矩阵Q,通过该矩阵来优化步长因子对数据起到白化作用,从而使得......