Organic electrodes represent an important direction in the implementation of new generation batteries. Their properties – such as low cost, environmental friendliness, sustainability, excellent structural versatility and flexibility – represent advantages that make them more desirable and useful compared to other active materials. An example of such a material is poly(hydroquinonyl-benzoquinonyl sulfide)/CNT or PHBQS/CNT, which is also the topic of the study of this master's thesis. Polymer nanocomposite PHBQS/CNT is an interesting organic cathode material mainly due to its high theoretical capacity (382 mAh/g). It consists of hydroquinone and benzoquinone units which are linked by the thioether bonds. The addition of the carbon nanotubes (CNTs) improves the electrical conductivity of this material and brings its capacity closer to the theoretical value. In the study, we optimized the required amount of the additive. Adding too big amount of the CNTs reduces the material's energy density, whereas insufficient addition does not give us the desired properties. The incorporation of the CNTs into the polymer matrix took place in the polymerization phase. Seven PHBQS/CNT polymer nanocomposites with different amount of added CNTs (0, 0.5, 0.75, 1, 5, 10 and 15 wt%) were successfully synthesized by the solvothermal in situ polymerization technique. We used the electrochemical impedance spectroscopy method for measuring the impedances and determining the conductivity of each polymer nanocomposite. Percolation behaviour was observed, which allowed us to determine the concentration at which a non-conductive polymer nanocomposite becomes electrically conductive. The critical concentration (percolation threshold) at which there was an increase in electrical conductivity by several orders of magnitude was observed at 1% addition of CNTs. This means that at least 1% of CNTs must be added to form a conductive network within the polymer matrix. The electrochemical performance of nanocomposites was analysed at, below and above the percolation threshold by galvanostatic measurements versus Li half-cell. At 0% of CNTs content, the maximum capacity was 301 mAh/g. At the percolation threshold, the nanocomposite reached the maximum capacity of 320 mAh/g, whereas above the percolation threshold (at 5% CNTs content) the maximum capacity was 342 mAh/g, which represents 89,5% of the theoretical capacity of the PHBQS polymer. As a result, at least 1% of the carbon nanotubes needs to be added for good electrochemical properties. For the most optimal electrochemical performance, it is necessary to add them a few percent above the percolation threshold.
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