A fire-retarding electrolyte using triethyl phosphate as a solvent for sodium-ion batteries

Abstract

We introduce a fire-retarding phosphate-based electrolyte, 1 M NaBF4 in triethyl phosphate with 3% vinylene carbonate as an SEI-forming additive for sodium-ion battery. With this electrolyte formulation, we achieved a...

Na–K Alloy Anode for High-Performance Solid-State Sodium Metal Batteries

“…This combination of cryo-HRTEM and FFT patterns of the crystalline areas confirm the presence of inorganic Na oxides (Na 2 O and NaO 2 ), Na phosphates (NaPO 3 and Na 4 P 2 O 7 ), and Na 2 ZrSi 3 O 10 (Figure f–j and Figure S6), derived from redox reactions between the Na–K alloy and SSE. We especially note that the highly chemical/electrochemically stable Na 2 O is primarily distributed in the outer parts of SEI, which inhibits direct interaction between the Na–K alloy and SSE, and may explain the notable decrease in unwanted side reactions. − We further note that Na phosphates, which enhance ion conductivity through the SEI, are mingled with Na oxides and amorphous phase. − Although SEI has been a major contributor to NASSB failure, the SEI formed in reaction to the Na–K alloy enhances both battery longevity and CCD.…”

Solvent Reorganization and Additives Synergistically Enable High-Performance Na-Ion Batteries

“…Enabling high safety is one of the most important goals for energy storage batteries. − In recent years, batteries based on fire-retardant liquid phosphate electrolytes have been widely investigated. − Phosphate solvents are intrinsically nonflammable for Na-ion batteries and exhibit advantages of the high solubility of Na salts, low viscosity, and compatibility with high-voltage cathode materials. , However, at the conventional electrolyte salt concentration (∼1 M), phosphate-based electrolytes have difficulty in forming a stable solid electrolyte interphase (SEI) film on the surface of the carbonaceous anodes, resulting in poor compatibility with carbonaceous electrodes. , SEI-forming additives such as vinylene carbonate (VC) and fluoroethylene carbonate (FEC) have been reported to improve the electrochemical stability of phosphate-based electrolyte but are still far from being satisfactory. , Consequently, it is necessary to develop novel phosphate-based electrolyte systems with high safety and excellent compatibility with electrodes for Na-ion batteries.…”

“…Law et al introduced a dilute triethyl phosphate (TEP) based flame-retardant electrolyte with VC as an additive and enabled improved cycling performance in an Na 3.2 V 1.8 Zn 0.2 (PO 4 ) 3 ||HC full cell . Nevertheless, the electrochemical performance achieved by Na-ion batteries with dilute nonflammable electrolytes is still far from satisfactory. ,, The underlying principles for designing high-performance and low-cost dilute nonflammable electrolytes and the fundamental stabilization mechanisms have not been clearly illustrated. Besides, the development of functional electrolytes principally focuses on the electrolyte salts and the local solvation structure of cations. , It is paramount to explore alternative electrolyte design strategies for high-performance Na-ion batteries.…”

“…10,11 SEI-forming additives such as vinylene carbonate (VC) and fluoroethylene carbonate (FEC) have been reported to improve the electrochemical stability of phosphate-based electrolyte but are still far from being satisfactory. 12,13 Consequently, it is necessary to develop novel phosphate-based electrolyte systems with high safety and excellent compatibility with electrodes for Na-ion batteries.…”

“…13 Nevertheless, the electrochemical performance achieved by Na-ion batteries with dilute nonflammable electrolytes is still far from satisfactory. 8,13,26 The underlying principles for designing high-performance and low-cost dilute nonflammable electrolytes and the fundamental stabilization mechanisms have not been clearly illustrated. Besides, the development of functional electrolytes principally focuses on the electrolyte salts and the local solvation structure of cations.…”