A Spectroscopic Investigation of Lithium Dithionite and the Discharge Products of a Li /  SO 2 Cell

Abstract

This work was funded by Naval Sea Systems Command (NAVSEA 63R-32) and constitutes a fraction of a program to establish a technology base for high discharge-rate Li/SOC12 batteries. We thank Mr. F. Romano (NAVSEA 63R-32) for his interest and support. ABSTRACTInfrared, x-ray, and electron spin resonance spectroscopic studies of laboratory-synthesized Li2S204 are reported. Spectra of cathode samples from Li/SO2 cells discharged at -30 ~ 25 ~ and 70~ are compared with the spectra of the laboratory-prepared Li2S204. The principal discharge material is confirmed to be Li~S~O4. The 70~ discharge is shown to produce a different set of products from the discharges at the lower temperatures.* Electrochemical Society Active Member.

Ambient Lithium–SO2 Batteries with Ionic Liquids as Electrolytes

“…Figure 4 a shows the IR spectra of the cathode products from the Li‐SO 2 cell with [Bmim][TFSI] as the electrolyte that discharged at 296.3 K for 10 days. The strong IR peaks at 1080, 1015, and 896 cm −1 are attributed to the absorption of dithionite (Li 2 S 2 O 4 ),19 indicating that the main component of the discharge product was Li 2 S 2 O 4 . Furthermore, three moderate peaks at 1248, 1166, and 954 cm −1 appeared in Figure 4 a; the first two peaks were assigned to polythionates Li 2 S n O 6 ( n >3) and the peak of 954 cm −1 belongs to the OS stretching of sulfite SO 3 19.…”

A New Perspective on Li–SO2 Batteries for Rechargeable Systems

“…[13,14] It operates based on the reaction between lithium ions and sulfur dioxide,w hich produces Li 2 S 2 O 4 (lithium dithionite) as ad ischarge product, delivering an energy density of about 330 Wh kg À1 . [15][16][17] Thes ulfur dioxide is initially dissolved or liquefied in the electrolyte of asealed cell with lithium metal as the anode and porous carbon as the cathode.E arlier Li-SO 2 systems needed to use apressurized cell;h owever, recent works have successfully demonstrated that an ambient pressure cell is also achievable with the proper selection of an electrolyte that can dissolve as ufficiently large amount of sulfur dioxide. [16] Although the Li-SO 2 cell has never been demonstrated in rechargeable conditions with agas inlet and outlet, the chemistry resembles that of the Li-O 2 system in many ways.D uring discharging, the gas phase receives electrons from the electrode surface, which subsequently combine with lithium ions to finally form lithium-containing solid discharge products.T he porous electrode accommodates alarge amount of solid products to achieve ah igh capacity and gradually fill the pores,w hich results in an increase in the impedance of the cell and finally the end of the discharge.H erein, we demonstrate that the charging reaction is also feasible in Li-SO 2 batteries,s imilar to Li-O 2 ,w hich can be reversibly operated using an organic electrolyte through the formation/decomposition of Li 2 S 2 O 4 .…”

High-efficiency and high-power rechargeable lithium–sulfur dioxide batteries exploiting conventional carbonate-based electrolytes

“…The ex situ X-ray diffraction spectra in Fig. 2d reveal that characteristic peaks of Li 2 S 2 O 4 appear and grow during discharge without any notable by-products, followed by the reduction of these peaks during the charge and their complete disappearance after the end of the charge 31 48 . These results evidently confirm that the reversible formation and decomposition of Li 2 S 2 O 4 is the major electrochemical reaction occurring in the Li-SO 2 system using an EC/DMC electrolyte, which is consistent with the DFT calculations.…”

“…Consequently, the accumulation of inactive and insulating by-products on the pores of the gas electrode would restrict the active reaction sites and the transport of reactants, including lithium ions and SO 2 gas, finally resulting in the cell failures. In previous studies on primary Li-SO 2 batteries, the formation of such by-products has generally been attributed to the self-decomposition of Li 2 S 2 O 4 due to its thermodynamic instability 11 48 60 . According to the XPS analysis of the surface of the cycled cathodes in Fig.…”