One of the key requirements of large-scale grid-storage systems is development of inexpensive and safe batteries. Sodium-ion batteries using earth-abundant Fe or Ti based cathodes and anodes would be ideal candidates for such storage systems. Herein, a new phase of Na-rich and all Fe Prussian Blue Analogue, monoclinic Na2Fe2(CN)6.2H2O, is reported as a potential cathode for such grid-storage sodium-ion batteries. This water-insoluble and air-stable cathode can deliver 85 mAh g−1 at an average discharge voltage of 3 V vs Na/Na+ with excellent cycle life (3,000 cycles). Many facets about its sodium storage characteristics are discussed with particular emphasis on the role of interstitial water on the sodium storage performance and its conversion to the dehydrated rhombohedral phase. Its compatibility with a newly developed non-flammable glyme-based liquid electrolyte, 1M NaBF4 in tetraglyme, is also disclosed along with general electrochemical and thermal characterization of this electrolyte for sodium-ion battery application. Finally, three different types of full cells are revealed with either monoclinic or rhombohedral phase as cathode and graphite or the recently reported Na2Ti3O7 ⇋ Na3-xTi3O7 pathway of Na2Ti3O7 as anode. Full cell energy densities of 70–90 Wh kg−1 (using cumulative cathode and anode weights) could be obtained without any pre-cycling steps. This new cathode and safe electrolyte may hold great promise toward development of inexpensive, non-flammable and highly stable grid-storage sodium-ion batteries.
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...
In order to become commercially viable,
sodium-ion batteries need
to deliver long cycle life with good capacity and energy density while
still ensuring safety. Electrolyte plays a key role forming solid
electrolyte interphase (SEI) layers at low potential, which affects
the thermal stability and cycle life of the anode materials under
consideration. In this study, an ether-based non-flammable electrolyte,
1 M NaBF4 in tetraglyme, is tested for sodium storage using
a non-carbonaceous anode material Na2Ti3O7/C, and the results are compared with those obtained with
the popularly used carbonate-based electrolyte, 1 M NaClO4 in ethylene carbonate (EC) and propylene carbonate (PC) (v/v = 1:1).
The Na2Ti3O7/C versus Na cells using 1 M NaBF4 in tetraglyme show a much higher
first cycle Coulombic efficiency (73%) than those using 1 M NaClO4 in EC/PC (33%). Thermal stability studies using differential
scanning calorimetry (DSC) conclusively show that Na2Ti3O7/C electrodes cycled with 1 M NaBF4 in tetraglyme are more thermally stable than the one cycled with
1 M NaClO4 in EC/PC. Further investigations on the formation
of SEI layers were performed using attenuated total reflection–Fourier
transform infrared spectroscopy, field-emission scanning electron
microscopy, transmission electron microscopy, energy-dispersive X-ray
spectroscopy, electrochemical impedance spectroscopy, and DSC studies.
These studies unambiguously demonstrate that the SEI formed on Na2Ti3O7/C using 1 M NaBF4 in
tetraglyme is not only less resistive but also more stable than the
SEI formed using 1 M NaClO4 in EC/PC.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.