Synthesis of hybrid layered electrode materials via chemical pre-intercalation of linear organic molecules

Abstract

Chemical pre-intercalation is a low-temperature, scalable synthesis method that utilizes a sol-gel process to form layered oxides with positively-charged species inserted between the layers. We have shown that this approach can be used to successfully intercalate Li+ , Na+ , K+ , Mg2+, and Ca2+ ions into the crystal structure of bilayered vanadium oxide (δV2O5).1 Through this ion-intercalation, the interlayer spacing of the δ-MgxV2O5 (M=Li, Na, K, Mg, and Ca) structure can be controlled between 9.6 A (δ-KxV2O5) and 13.4 A (δ-MgxV2O5).1 Moreover, the expanded spacing achieved for the δ-MgxV2O5 phase corresponded to increased electrochemical stability in both Li- and Na-ion cells.[1] While this study identified a correlation between expanded interlayer spacing and improved electrochemical stability over cycling, chemical pre-intercalation of ions does not allow for expansion beyond that exhibited by the δ-MgxV2O5 structure. In this work, we show that further expansion of the interlayer spacing can be achieved via pre-intercalation of positivelycharged linear, organic cations. We report synthesis of hybrid inorganic/organic materials with a 1D nanobelt morphology. The layered structure of the hybrids is confirmed by both XRD and TEM analysis. δ-V2O5 preintercalated with cetyltrimethylammonia ions, CTA+ , demonstrated the interlayer spacings of all samples (31 A), more than twice larger than the largest interlayer spacing achieved via pre-intercalation of inorganic ions. The effects of carbon chainlength and positively charged nitrogen termini on the interlayer spacing and electrochemical stability is investigated, with two N-termini on the cation (DMO+) resulting in increased electrochemical stability of the preintercalated phase.