Structure and electrochemical characteristics of silver-doped composites based on multi-walled carbon nanotubes and K$_x$MnO$_2$ oxide

The mechanisms of composites formation based on multi-walled carbon nanotubes (MWCNTs) and silver-doped K$_x$MnO$_2$ oxide obtained by treating MWCNTs in an aqueous solution of KMnO$_4$ with the addition of AgNO$_3$ were studied. The crystal structure and chemical state of the composites obtained with different synthesis times were analyzed. It was shown that with a short synthesis time, defective MnO$_{2-x}$ oxide is predominantly formed on the MWCNT surface, which, in the case of doping, additionally contains double oxides Ag$_x$MnO$_2$. With an increase in the synthesis time, composites are formed containing predominantly layered K$_x$MnO$_2$ oxide, which, in the case of doping, contains Ag$_x$MnO$_2$ oxides and Ag$_{2-x}$O oxide nanoparticles. Analysis of electrochemical characteristics showed that doping of the composite provides a noticeable increase in specific capacity up to $\sim$201F/g at a discharge current density of 0.1A/g versus 148F/g for the undoped composite.