A Novel Electrolyte Pyridine Additive for Enhancing Cycle Life of Lithium-Ion Batteries

Lithium-ion (Li-ion) battery using a graphite (Gr.) anode and a lithium iron phosphate (LiFePO4, LFP) cathode (Gr.||LFP) has been widespread in energy storage. To match the warranty period of energy storage systems, the lifespan of this kind of Li-ion battery, not only under room temperature but also under relatively high temperature, is critical. Exploration of functional electrolyte additive provides an efficient approach to address this issue. This study reports the usage of pyridine (Py) as a new electrolyte functional additive for Gr.||LFP. In the first cycle, it was found that Py can be reduced before ethylene carbonate and vinylene carbonate, forming a dense and homogeneous solid electrolyte interface (SEI) layer containing rich nitrogen and fluorine elements. Owing to the merits of the SEI layer, the parasitic reactions which occur at the graphite anode and consume the active lithium ion during cycling were suppressed. With the amount of 0.5wt% Py additive in the electrolyte, the Gr.||LFP pouch cell achieved a capacity of 3.2 Ah, exhibiting remarkablly enhanced cycling stability and high-temperature storage capability. Under the experimental conditions of 25 °C and 0.5 P, the capacity retention of the pouch cell reached 95.64% after 500 cycles, while still maintained 82.75% of the initial capacity after 1000 cycles under 45 °C and 1 P. After the 30-day storage at 45 °C and 60 °C, the capacity retention rates were 87.38% and 80.56%, respectively, which are significantly higher than those of the pouch cells with the blank control electrolyte. This work identifies Py as a highly promising electrolyte additive in stabilizing the graphite-based anode of Li-ion battery under both room temperature and high temperature.