Primary and Secondary Lithium Passivation Characteristics and Effects in the Li /  SO 2 Couple

Abstract

The characteristics and effects of the lithium passivation layer in the lithium sulfur dioxide false(normalLi/SO2false) cell have been studied. Four aspects have been investigated: (i) passivation layer‐induced polarization; (ii) effects of long‐term, low discharge rates; (iii) chemistry of the lithium passivation layer; and (iv) kinetics of the passivation layer growth. Polarization studies showed that an initial polarization (voltage delay) was in some cases followed by a secondary polarization. Studies of the effects of long‐term, low discharge rates indicated that low discharge rates modified the lithium passivation layer, which resulted in increased lithium corrosion and decreased cell capacity. The degradation was greater at higher temperature. Results of studies of the chemistry and formation kinetics of the lithium passivation layer were interpreted in terms of a primary layer, which was responsible for the passivation, and a thicker, porous secondary layer. Formation of the secondary layer is exacerbated by partial discharge. The secondary layer results from precipitation of the Li corrosion products, and was found to contain Li2S2O4 , Li2S2O5 , and Li2SnormalnO6 , where normaln>2 . The primary layer is responsible for the initial polarization (voltage delay) under load, whereas the secondary layer induces a second polarization that inhibits high‐rate discharge.

Dendrite-Free Li Metal Anode for Rechargeable Li–SO2 Batteries Employing Surface Modification with a NaAlCl4–2SO2 Electrolyte

“…On the other hand, the unmodified Li/Li symmetric cell showed a drastic voltage drop to 0.0 V (vs Li/Li + ) after 20 h. The short-circuit of the unmodified Li electrodes might result from filamentary growth of Li deposits. , As schematically illustrated (Figure b–d), for the expected phenomena of Li growth during the above short-circuit tests, we speculate that the surface layer of the NaAlCl 4 –2SO 2 -modified Li electrode provides a stable chemical and mechanical environment during repeated Li deposition/dissolution, thereby suppressing filamentary growth of Li. We also found another positive effect of the surface modification, in concerning the voltage-delay issue that is normally observed in the Li–SO 2 primary battery system. , Although the relatively large polarization of potential was observed at the start in the unmodified Li/Li cell, the surface-modified Li/Li cell exhibits less polarization after the storage, which is strongly related to the improved physicochemical nature of the surface film achieved by the surface modification.…”

“…We also found another positive effect of the surface modification, in concerning the voltage-delay issue that is normally observed in the Li−SO 2 primary battery system. 28,29 Although the relatively large polarization of potential was observed at the start in the unmodified Li/Li cell, the surface-modified Li/Li cell exhibits less polarization after the storage, which is strongly related to the improved physicochemical nature of the surface film achieved by the surface modification. We also performed charge/discharge cycling tests using symmetric Li/Li cells for a given condition of 300 cycles for 1000 h, and the results are shown in Figure 2e.…”

Lithium‐Ion Conducting Electrolyte Salts for Lithium Batteries

“…The CF bonds in the CF 3 groups strongly react with Li + and formed LiF species. Similarly SO 2 reacts with Li + and to form compounds like Li 2 S 2 O 4 and Li 2 S 115. The mechanism shown in Equations (27)–(29) gives information about the reduction process79 of LiTFSM. …”