Lithiation potential

The electrochemical impedance analysis carried out in the same study by Zhang et al. seemed to confirm the above speculation with the change in the resistance of the SEI film as a function of the lithiation potential and corresponded well with the irreversible capacity analysis. Figure 19 shows the potential-dependence of the resistance for lithium ions in the... 

Zhnang et aL compared the FUR spectra of pure LEDC on Ni surface after cyclic voltarmnetry inl.2 M LiPFe EC/EMC electrolyte, and metallic lithium cleaved the same electrolyte, as shown in Fig. 5.8 [39]. By comparison of IR spectra, they established that LEDC is the predominant surface species on a Ni electrode after lithium deposition in LiPFg/ECdiMC electrolyte, confirming that at the lithiation potential the... 

FIGURE 4.1 (a) Rate capability of nanocrystalline and bulk UC0O2 at various discharge rates (1C-100C rate). Solid lines are fitted results, (b) Crystallite size dependence of the second lithiation potential curves for UC0O2. Adapted with permission from Ref. [13]. Copyright 2007 American Chemical Society. 

One material system that makes the importance of nanostructuring abundantly clear is the spinel Li4TisOi2. Its lithiation potential (1.55 V versus Li°) and... 

In the case of the Sng2Ni3g electrode, the potential profile shows a slope that starts from 0.80 V vs. Li/Li and a plateau from 0.24 V vs. Li/Li. From the potential profile of the Sn electrode, the latter plateau can be assumed to be the formation of Li-rich Sn-Li alloy phases. 0.24 V vs. L /L is lower than the corresponding lithiation potential of the Sn electrode, which could indicate the higher overpotential associated with the electrochemical reaction to form Li-rich Sn-Li alloy phases in the Sn62Ni3g electrodes. The deflection profile shows only one flexion point of tensile stress increase which starts at 0.24 V vs. Unlike Sn, flexion points of the... 

Whereas the electrochemical decomposition of propylene carbonate (PC) on graphite electrodes at potentials between 1 and 0.8 V vs. Li/Li was already reported in 1970 [140], it took about four years to find out that this reaction is accompanied by a partially reversible electrochemical intercalation of solvated lithium ions, Li (solv)y, into the graphite host [64], In general, the intercalation of Li (and other alkali-metal) ions from electrolytes with organic donor solvents into fairly crystalline graphitic carbons quite often yields solvated (ternary) lithiated graphites, Li r(solv)yC 1 (Fig. 8) [7,24,26,65,66,141-146],... 

The silicon analogue 74 u5) also appears to be a potentially useful conjunctive reagent in this sequence even though silicon appears to retard the rearrangement71 It is generated by silylation of 37a followed by reductive lithiation (Eq. 90). The... 

Because of the similar potentials between fully lithiated graphite and lithium metal, it has been suggested that the chemical nature of the SEIs in both cases should be similar. On the other hand, it has also been realized that for carbonaceous anodes this formation process is not expected to start until the potential of this anode is cathodically polarized (the discharge process in Figure 11) to a certain level, because the intrinsic potentials of such anode materials are much higher than the reduction potential for most of the solvents and salts. Indeed, this potential polarization process causes one of the most fundamental differences between the SEI on lithium metal and that on a carbonaceous anode. For lithium metal, the SEI forms instantaneously upon its contact with electrolytes, and the reduction of electrolyte components should be indiscriminate to all species possible,while, on a carbonaceous anode, the formation of the SEI should be stepwise and preferential reduction of certain electrolyte components is possible. 

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