β-cyclodextrin and adamantane polyacrylic acid copolymers as supramolecular binder for silicon anodes: N-methylpyrrolidone or water for preparing the slurries?

Abstract

Silicon is a promising material for anodes in future generations of LIBs. However, itsvolume changes during the lithiation/delithiation process that degrades batteryperformance, making it an impractical alternative. To mitigate this issue, we have found aviable alternate solution, which is the preparation of adamantane-polyacrylic acid (AdENAA) and β-cyclodextrin-polyacrylic acid (βCD6A-AA) polymers as supramolecular binders.The advantage of these binders is that polymers leverage host-guest interactions. To carryout this research, we prepared the anode materials in water and in NMP, and then westudied their capacity to crosslink and gel. Additionally, we examined the extent of thesupramolecular interaction vs. hydrogen bond. Thermogravimetric analysis showed thatthe thermal stability of the mixture of complementary polymer increased in the followingorder: AdEN-AA/βCD6A-AA in NMP < βCD6A-AA/PAA < AdEN-AA/βCD6A-AA, with the latter two in water. Accordingly, the anode material prepared in water shows the higheststability, retaining capacities of over 1000 mAhg-1 after 90 cycles vs. 279 mAhg-1 of theelectrode prepared in NMP. The results agreed with the SEM micrographs of the anodematerial, in which the slurry prepared in water showed better integrity of the siliconnanoparticles and of solid electrolyte interphase than the slurry prepared in NMP.