The chemical environments of the interlayer Na sites of layered titanate are finely controlled by the intercalation of n-alkylamine with various alkyl chain lengths to explore an effective way to improve its electrode functionality for sodium-ion batteries (SIBs). The n-alkylamine intercalation via ion-exchange and exfoliation-restacking routes allows the modification of in-plane structures of layered titanate to be tuned. Among the present n-alkylamine-intercalates, the n-pentylamine-intercalated titanate shows the largest discharge capacity with the best rate characteristics, underscoring the critical role of optimized intracrystalline structure in improving the SIB electrode performance of layered titanate. The creation of turbostratic in-plane structure degrades the SIB electrode performance of layered titanate, indicating the detrimental effect of in-plane structural disorder on electrode activity. 23Na magic-angle spinning nuclear magnetic resonance spectroscopy demonstrates that the n-alkylamine-intercalated titanates possess two different interlayer Na+ sites near ammonium head groups/titanate layers and near alkyl chains. The intercalation of long-chain molecules increases the population of the latter site and the overall mobility of Na+ ions, which is responsible for the improvement of electrode activity upon n-alkylamine intercalation. The present study highlights that the increased population of interlayer metal sites remote from the host layers is effective in improving the electrode functionality of layered metal oxide for SIBs and multivalent ion batteries.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. NRF-2017R1A2A1A17069463), by the Korea government (MSIP) (No. NRF-2017R1A5A1015365), and by the National Research Council of Science & Tehcnology in Korea (DRC-14-1-KBSI). The experiments at PAL were supported in part by MOST and POSTECH.
All Science Journal Classification (ASJC) codes
- Materials Science(all)