Dual-Functional Additive Bipyridine Cobalt Complex for Highly Efficient Kinetics and Lithium Regulation in Lithium–Sulfur Batteries

Le résumé fourni par la source

The efficiency and stability of lithium–sulfur (Li–S) batteries are mainly limited by slow reaction kinetics and lithium dendrite growth. To deal with these issues, in this study, Co(bpy) 3 (PF 6 ) 2 was employed as a dual-functional additive to improve the performance of Li–S batteries. In the case of sulfur cathodes, as evidenced by electrochemical measurements and density functional theory calculations, Co(bpy) 3 (PF 6 ) 2 exhibits a strong affinity toward lithium polysulfides (LiPSs), accelerating the LiPS conversion process. Conversely, in the case of Li anodes, due to LiF-rich solid electrolyte interphases formed by PF 6 – anions, Co(bpy) 3 (PF 6 ) 2 can react with the Li metal anode to reduce Li dendrite growth. Batteries incorporating Co(bpy) 3 (PF 6 ) 2 were prepared and subjected to charging and discharging cycles. These batteries achieved a first-cycle discharge capacity of 1228 mAh g –1 at 0.2 C and a capacity of 914.4 mAh g –1 at 2 C. They retained 99.7% of their initial capacity when returning to 0.2 C. Co(bpy) 3 (PF 6 ) 2 was commonly used in dye-sensitized solar cell electrolytes and responsible for charge transport. This study demonstrates that Co(bpy) 3 (PF 6 ) 2 can be used as a dual-functional additive, and it offers avenues for advancing practical Li–S batteries and fresh perspectives for integrated optical energy storage devices.

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