Lithium borate polymers, ionic conductivity

Figure 7 Temperature dependence of ionic conductivity for lithium borate polymer electrolytes prepared via polymer reactions.

Table 4 Ionic Conductivity of Lithium Borate Polymers Prepared via Polymer Reactions...

Before treatment with alcohol, the ionic conductivity of lithium borate polymers was 6.23 X 10-5 to 2.07 X 10-7 Scm-1 at 50°C. The maximum ionic conductivity was observed for the polymer with a PE040o spacer unit. After the polymer reaction with alcohols, glass-transition temperatures of these polymers were found to be -52 to 39°C, which was higher than that of poly(lithium mesitylhydroborate) ( 69°C). 

The ionic conductivity of this lithium borate polymer bearing the methoxybo-rate unit (9a) was 8.77 X 10 6Scm 1 at 50°C (Fig. 8). This value was lower than that observed before the polymer reacted with methanol. However, it was still greater... 

To immobilize such anions as borate, organoboron polymers were reacted with aryllithium reagents.31,32 The reaction of alkylborane polymers with n-BuLi was examined first however, the ionic conductivity of the resulting material was very low. Moreover, complicated peaks were observed in the H-NMR spectrum. Conversely, selective lithium borate formation was observed in the nB-NMR spectrum when PhLi was employed (scheme 6). An ionic conductivity of 9.45 X 10 7Scm 1 was observed at 50°C. The observed ionic conductivity was relatively low because of the decreased number of carrier ions compared with dissolved salt systems. However, the lithium transference number of this polymer was markedly high (0.82 at 30°C). 

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