Lithium Demand and Cyclability Trade-Off in Conductive Nanostructure Scaffolds in Terms of Different Tortuosity Parameters

Abstract

Through alteration of the polarity of DC plasma during the growth of carbon nanotubes in a PECVD reactor, significantly different morphologies of such species have been achieved. By using this approach, for the first time, both Half-aligned and Entangled structures were synthesized, along with Full-aligned carbon nanotubes, introducing three binder-free electrodes with various levels of tortuosity. The crucial parameter and influential effect of tortuosity in these three-dimensional nanostructure scaffolds for application in lithium-ion batteries were investigated. Previous research findings suggested that increasing the tortuosity of the conductive scaffolds leads to preferential accumulation of lithium at the top surface and causes the loss of capacity in subsequent charge-discharge cycles. Our finding reveals that there exists a trade-off between lithium-demand, capacity, and preferential accumulation of lithium at the top surface. Among the presented scaffolds, the Half-aligned MWCNTs was able to maintain a high capacity of 876.9 mAh/g over more than 300 cycles, and demonstrate capacity improvement during this period and excellent rate capability, even at a rate of 5 C. This capacity is almost three times that can be achieved with graphite, showcasing promising and outstanding results for carbon nanotubes.