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(SEI) is formed according to the previous studies[7-8]. As the potential becomes more negative, another peak appeared at 0.6 V, which is attributed to the formation of lithium-poor alloying phase... the second sweeping, the peak at 1.35 V is higher than that of the first cycle. This indicates that the SEI film formed on electrode at the first cycle is not enough, because the electrode cracks during......
LiMn2O4 and LLTO coated LiMn2O4 at different rates 未包覆LiMn2O4和LLTO包覆的LiMn2O4循环10次后的交流阻抗(EIS)如图9所示.从图9可以看出:2种材料的交流阻抗图都是由高频区域1个拉长压扁半圆,中频区域1个圆弧和低频区域的1条斜线三部分组成.Liu等[23-25]认为,高频区域的半圆反映了锂离子在SEI膜中迁移的阻抗,中频区域的半圆则与电荷转移有关,低频区域的斜线反映锂离子扩散过程的Warburg阻抗.从图9中的放大图可以看出:LLTO包覆的LiMn2O4材料的SEI膜阻抗比LiMn2O4的小,这说明包覆层LLTO有利于减少活性物质和电解液直接接触,使SEI膜的形成受阻,导致SEI膜阻抗降低.从图9还可以看出:LLTO包覆的LiMn2O4的电荷转移阻抗明显比未包覆的LiMn2O4的小,使得材料的极化减小,与循环伏安的结果一致,也证......
temperatures. The products generated from the side reactions corrode the solid electrolyte interphase (SEI) layers on anodes and react with EC-containing solvents. The series reactions generated from... reaction between solvent and PF5; 3) Increasing cell resistance that may be due to the precipitation of polymer and insoluble salt on battery component surfaces; 4) Solid electrolyte interphase (SEI......
理想材料[2-3].值得注意的是,与其搭配的正极材料不再限于LiMO2(M=Ni,Co,Mn)和LiFePO4,还包括O2和S等,使得电池的能量密度再次提升(Li-O2和Li-S的能量密度分别为3 505 W·h/kg和2 600 W·h/kg)[4].尽管锂金属电池(LMB)拥有以上优点,但电池充放过程中,体积变化,SEI膜的脆弱性和枝晶生长[5]会导致很多安全(短路,爆炸)和性能(库仑效率低,循环寿命短)问题,使LMB还不能被实际应用.研究人员从LMB的失效机制出发,总结出多种锂枝晶的形核生长的理论模型和负极的优化方法,包括电解质的改良,如有机溶剂的组合[6],锂盐的选择[7],调节SEI膜的功能性添加剂[8]以及选取较高弹性模量的固态电解质[9],通过控制锂金属负极与电解液之间的界面层反应达到抑制锂枝晶生长的目的,然而LMB负极体积膨胀依然无法避免[10],由此负极结构设计对于提高电......
,其峰电势在0.51~0.69 V范围,这是首次循环过程中在电极表面上形成SEI膜所导致.纳米粉体A即在无碳气氛制备的Al-Fe纳米粒子,其主相和活性组元为单质Al,其嵌/脱锂电位分别出现在0.14 V和0.53 V处(见图4(a)),但在首次循环中没有出现相应的还原峰,这是由于Al相表面氧化膜需要经过首次循环破裂后才可以进行Li+嵌入[32],其他粉体样品中也同样出现类似现象.活性Al相嵌锂后形...氧化物与Li+发生不可逆反应,生成Li的氧化物(Li2O)[36],造成Li+的损失;电解液和活性物质之间形成SEI膜,也造成Li+的损失;活性物质在充放电过程中产生的体积膨胀可使其失去部分电接触,导致循环性能较差[37]. 2.2.3 合金Al-Fe/C纳米复合电极的阻抗谱 为了进一步了解Al-Fe,Al-Fe-C纳米复合材料的电化学特性,分别测试了4种复合材料电极在循环前(见图6......
to the charge transfer resistance (Rct), and the low frequency region represents the lithium ions diffusion (Wdif) [24-26]. Rsei comes from the resistance to lithium ion migration in SEI, while Rct mainly... the initial five cycles, the cell using LiFSI0.6-LiBOB0.4-based electrolyte shows higher Rsei than the other. This is because Rsei is determined by the SEI characteristics on the working electrode surface......
to the irreversible Li-insertion. The formation of solid electrolyte interphase (SEI) film and the decomposition of electrolyte are responsible to the second peak. The 0.01 V peak is ascribed to the reversible... from that of the subsequent curves and no significant shift was observed after the 3rd cycle, which implied the stable SEI films and the good cycling performance of the obtained one-dimensional......
+ 2Fe+4Li2O[15-16].电压从0.8 V降至0.01 V,这可能是因为得到的金属单质与电解质形成了凝胶膜和SEI膜[17].在首次充电过程中,在1.4 V左右有一个平滑的充电平台,平台区间对应的比容量为200~700 mA·h/g,可能发生的反应是 M+2Fe+Li2O= Li++MFe2O4 图4 碳包覆后ZnFe2O4和CoFe2O4的拉曼光谱图 Fig. 4  ...率分别为66.7%,57.3%,68.0%和73.1 %.首次充放电比容量有所差别可能是因为Li离子的嵌入和脱嵌不可逆引起的.不可逆的原因可能是电解液被还原形成固态电解液界面层(SEI),电解液在材料表面和残余的氢氧根发生反应生成氧化锂以及界面Li存储等[18-19].通过对比发现CoFe2O4和MgFe2O4具有相对较高的首次可逆容量及库仑效率. 图6所示为所制备的材料在0.05C电流密度下的循......
to the formation of solid electrolyte interphase (SEI) film, and the oxidation current peaks from 0.001 to 1.5 V correspond to the lithium de-intercalation. The peak at around 1.3 V can be observed in every... that the current peak for SEI layer formation still exists in the initial cycles, which accounts for the initial capacity loss of these anodes. These current peaks would be hardly observed gradually......
curves of Li3V2(PO4)3/C at 10C(c) 对不同面密度极片所装配的扣式电池进行交流阻抗测试,其复平面阻抗图和等效电路图如图4所示.阻抗图谱由5个部分组成:1区为电池本征电阻,2区为 SEI 膜阻抗,3区为界面反应阻抗,4区为电荷转移阻抗,5区为锂离子的扩散引起的 Warburg 阻抗.图 4(c)所示为用ZView 2软件对图4(a)模拟的等效电路图,各元件拟合结果见图4(b).从图4(b) 中拟合数据结果可知,电池的本征阻抗基本相似,为3.1~4.2 Ω.SEI膜阻抗呈现波动现象,最小值7.32 Ω,最大值15.79 Ω,与面密度大小没有明显的对应关系,SEI膜阻抗较大说明SEI膜形成不够好,对电子的转移阻力增大.界面反应阻抗和电荷转移阻抗随着极片面密度的增加呈现上升趋势,说明面密度增加使电极反应的阻抗增加,电荷转移变得困难,不利于高倍率下的放电. 图4 ......