Butylene carbonate as a cosolvent to suppress aluminum corrosion in LiFSI electrolytes for long-life lithium-ion batteries

Lithium hexafluorophosphate (LiPF 6 ) is currently the dominant lithium salt electrolyte in lithium-ion batteries (LIBs), while lithium bis(fluorosulfonyl)imide (LiFSI) is a promising alternative due to its superior stability and higher capacity retention. However, under high-voltage operating conditions, aluminum current collectors exhibit an inherent tendency toward electrochemical dissolution. This study introduces using 1,2-butylene carbonate (BC) to partially replace ethylene carbonate (EC) in the electrolyte to inhibit Al corrosion. The results reveal that the introduction of BC reduces the activity of FSI − through strong coordination with FSI − , and it weakens the interaction between EC and Li + by forming strong hydrogen bond analogue with EC. This promotes the pairing of FSI − with Li + to form an anion-cation aggregate (AGG), further reducing the activity of free FSI − with corrosion potential and an AlF 3 /LiF passivation layer can be formed on the aluminum collector surface. Furthermore, the LiFSI + BC system can form a thin and uniform cathode electrolyte interface (CEI) film over LiFePO 4 (LFP). The LFP||Li battery assembled based on this electrolyte achieved a capacity retention rate of 99.58% after 500 stable cycles at a cut-off voltage of 3.8 V and a rate of 0.5C. This work provides an effective strategy toward developing of lithium-ion batteries with long cycle life.