STUDIES OF ANODES AND THEIR INTERACTIONS WITH ELECTROLYTES IN SODIUM-ION BATTERIES

Abstract

In this thesis, we focused on the anode materials for NIB and investigated in detail the interaction between anodes and electrolytes. More specifically, Na2Ti3O7/C, graphite, and hard carbon were tested in a non-flammable ether-based electrolyte, 1M NaBF4 in tetraglyme and carbonate-based electrolyte, 1M NaClO4 in EC:PC. Cycling performance in half-cell and full-cell are illustrated and more importantly, thermal stability and investigations on solid electrolyte interphase (SEI) are discussed. Optimization study on the non-flammable electrolyte, 1M NaBF4 in tetraglyme was carried out with two types of borate compounds (triethyl borate (TEB) and tris(trimethylsilyl) borate (TMSB)) as electrolyte additives, which results in significantly improved rate performance. Furthermore, a newly-designed fire-retarding phosphate-based electrolyte is discussed in this contribution. With vinylene carbonate (VC) as the electrolyte additive, 1M NaBF4 in triethyl phosphate (TEP) shows stable electrochemical performance in NIB full-cell with both coin-cell and 18650-type cell configuration.