PEO-LiClO

One easily verifies, the ratio equals unity for w = 1 and n decreases with descending ratio. Results for the system PEO + LiClO are Usted in Table 5. We add also data referring to ENR-25 + salt. The data in the Table confirm that we observe in PEO Debye relaxation to a good approximation at low salt content. At high salt content interactions between dipoles cannot be neglected anymore. 

A second type of soHd ionic conductors based around polyether compounds such as poly(ethylene oxide) [25322-68-3] (PEO) has been discovered (24) and characterized. These materials foUow equations 23—31 as opposed to the electronically conducting polyacetylene [26571-64-2] and polyaniline type materials. The polyethers can complex and stabilize lithium ions in organic media. They also dissolve salts such as LiClO to produce conducting soHd solutions. The use of these materials in rechargeable lithium batteries has been proposed (25). 

FIGURE 18 Glass transition temperature as a function of (a) LiClO content and (b) nanotube content, a) PEO - solid squares, ENR-25 - open squares and b) PMMA+ nanotubes. 

FIGURE 22 Equivalent conductivity of PEO with addition of LiClO, concentration range corresponds to 0.005 < 7 < 0.1... 

FIGURE 23 The DC conductivity of PEO (solid squares) and ENR-25 versus mass fraction of LiClO. at 300 K. 

FIGURE 24 The DC conductivity after Equation (54) and ion diffusion coefficient in PEO after Equation (58) in dependence on mass fraction of LiClO. ... 

Chan and Kammer, (2008) and Sim et al., (2011) studied on the immiscible PEO/ENR/LiClO and PEO/PAc/LiClO systems reported that the two Ts of the immiscible blends estimated under constant salt content were observed to be higher than their respective values in the pristine salt-free systems. Figure 24 depicts the variations of T as a function of weight fraction of PEO (IFp ) for the salt-free and salt-added PEO/ENR and PEO/PAc systems. The salt content in the PEO/ENR/LiClO and PEO/PAc/LiClO blends are 12 and 15 wt%, respectively. A close examination of the plots in Figure 24 concludes that the difference in the T value of PEO between the salt-free and salt-added PEO/ENR blends (Ar/ °) is... 

FIGURE 24 Glass transition temperatures as funetions of weight fractions of PEO in salt-free and salt-added PEO/ENR and PEO/PAc blends. Solid markers denote the salt-free polymer components—(A) PEO, ( ) ENR, and ( ) PAc. The salt-added components are represented by the open markers—(0, o) PEO and ENR added with 12 wt% LiClO, (A, ) PEO and PAc added with 15 wt% LiC10 . The doubled headed arrow shows the difference in T values between each salt-free and salt-added polymer component for the two blends. 

PEO/ENR/LiClO and PEO/PAc/LiClO blend systems are depicted in Figure 25. The difference in the and values of the two amorphous polymers, ENR and PAc, are reflected in the conductivity results of the two immiscible blend systems to be discussed later. 

FIGURE 25 of LiClO/orthe ( ) PEO/ENR/LiClO and ( ) PEO/PAc/LiClO blends. 

The microstractrrre of PEO sphenrhtes growing rmder the influence of a salt encounters dramatic changes especially at high salt concentrations. Rocco et al., (2002, 2004) in their work on the miscible blends of PEO/PMVE-MAc/LiC10, with 60 PEO arrd PEO/PBE/LiClO have reported an increase in the size and perfection of the crystallites at salt content < 1 and 7.5 wt%, respectively, which... 

The addition of LiClO to PEO/ENR and PEO/PAc blends causes the PEO sphemlites to grow anisotropically, thus, forming nonspherical spherulites (Chan and Kammer, 2008). Similar amorphous regions which appear as dark spots within the spherulites are also observed in both the electrolyte systems at salt content < 12 wt% (see Figure 27) ... 

The ion conductivity of the three PEO/PMMA blend compositions, 25/75, 50/50, and 75/25 studied by us increases with ascending LiClO content due to increasing number of free mobile ions as shown in Figure 28. In addition, blend composition with 75 wt% PEO doped with 0 to 12 wt% LiClO displays comparatively higher a values in the order of 10 S cm than the other two blends. Nevertheless, Tan and Johan, (2011) studied the ion conductivity of PEO/PMMA blend polymer electrolyte found that the composition 20 wt% PEO and 80 wt% PMMA is the most miscible proportion for the blend. Figure 28 depicts that the PEO/PMMA 20/80 blend achieves a maximum ion conductivity of 7 x 10 S cm at 10 wt% LiClO, further enhancement in conductivity can be achieved by the addition of a low molecular weight, low viscosity, and high dielectric constant plasticizer, EC. The incorporation of EC facilitates the dissociation of the... 

Additionally, the a value of PEO declines when blended with PAc, contrary to an increase in a value when ENR is added to PEO in the absence or presence of LiClO,. The T values, as discussed earlier, show diat die salt is more soluble in PAc as compared to ENR. Therefore, with a fixed salt content, the amount of salt dissociated in the PEO amorphous phase is definitely higher for the PEO/ ENR blend compared to the PEO/PAc blend. Besides, the T values of PAc in the presence of salt is raised to a range of 29-37 °C which means the PAc is in its glassy state when ion conductivity of the blend is measured leading to restricted ion mobility in the PEO amorphous phase which forms the predominant percolating pathway of the blend electrolyte. It can be concluded that the ion conductivity of miscible or immiscible PEO-based blend electrolyte is governed by the charge... 

FIGURE 29 Variations of ion conductivity as a function of weight fractions of PEO. ( ,V) denote blends of PEO/ENR and PEO/ENR with 12wt%LiC10. ( , )correspond to blends of PEO/PAc and PEO/PAc added with 15 wt% LiClO, respectively. The two headed arrows indicate the difference in a values between the two blends at blend composition PEO/ENR and PEO/PAc 60/40. 

Figure 2 depicts temperature dependent conductivity plots for a series of LiClO -containing networks with increased PEG chain length. For networks with MW of PEG > 2000 a distinct break in the plot is found around 60 °C, close to the PEO melting point. As expected, the conductivity rapidly increases with the EO unit content of the network, a at 25°C being only 10" S cm" for the PEG 3P0 network and rising to 5 x 10 ° S cm for the PEG 2000 network. A value of 10" S cm" is reached for the PEG 5750 network at 90°C where the polymer electrolyte is completely amorphous. 

Table V. Glass transition temperatures and relative dielectric constants as a function of voltage for bieiids of PEO/TEG/PZVP/LiClO. ...

Unlike most crystalline solid electrolytes, the PEO-based electrolytes, such as LiClO. (PEO)g, conduct both anions and cations. While many high-conductivity solid electrolytes for cations are known, there are relatively few good conductors of anions. This work began as an exploration of the possibility of preparing PEO electrolytes in which the anion transport number is essentially one. The initial strategy was to prepare solid solutions of divalent cations and monovalent anions in PEO, with the expectations that the divalent cations would be trapped and their diffusion impeded by their double charge. 

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