Researchers at Tsinghua University (China) report in a paper in ChemSusChem on their use of both lithium anode passivation and polysulfide anion diffusion suppression strategies to reduce self-discharge of the lithium–sulfur cell. The self-discharge of a lithium–sulfur cell decreases the shelf-life of the battery and is one of the bottlenecks that hinders its practical applications.
For their investigation, the researchers used a lithium–sulfur cell with a carbon nanotube/sulfur cathode and lithium-metal anode in lithium bis(trifluoromethanesulfonyl)imide/1,3-dioxolane/dimethyl ether electrolyte was selected as the model system to investigate the self-discharge behavior.
LiNO3 used as an additive induced a high density passivation layer on the Li metal anode, resulting in a very low shuttle constant of 0.017 h−1. The diffusion of the polysulfides was retarded by an ion-selective separator, and the shuttle constants decreased.
The cell with LiNO3 additive maintained a discharge capacity of 97 % (961 mAh g−1) of the initial capacity after 120 days at open circuit, which was around three times higher than the routine cell (32 % of initial capacity, corresponding to 320 mAh g−1). It is expected that lithium–sulfur batteries with ultralow self-discharge rates may be fabricated through a combination of anode passivation and polysulfide shuttle control, as well as optimization of the lithium–sulfur cell configuration.—Xu et al.
Xu, W.-T., Peng, H.-J., Huang, J.-Q., Zhao, C.-Z., Cheng, X.-B. and Zhang, Q. (2015) “Towards Stable Lithium–Sulfur Batteries with a Low Self-Discharge Rate: Ion Diffusion Modulation and Anode Protection,” ChemSusChem doi: 10.1002/cssc.201500428