An Imidazole-Based Electrolyte Additive for Enhancing the Cyclability of Graphite||LiFePO₄ Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Graphite||LiFePO4 (Gr||LFP) lithium-ion batteries (LIBs) are crucial for stationary energy storage.
• Current Gr||LFP batteries have limited lifespans, hindering long-term energy storage applications.
• Developing strategies to enhance the stability and longevity of LIBs is essential.

Purpose of the Study:

• To design and implement a novel solid electrolyte interphase (SEI)-forming additive for Gr||LFP batteries.
• To improve the chemical stability and density of the SEI layer on the graphite anode.
• To enhance the overall cycle life and capacity retention of Gr||LFP LIBs.

Main Methods:

• Molecular structure design of an imidazole-based additive, N,N '-carbonyldiimidazole (CDI).
• Electrochemical characterization of CDI as an SEI-forming additive in Gr||LFP pouch cells.
• Analysis of SEI composition and interfacial properties.

Main Results:

• CDI preferentially reduces at 1.58 V vs Li/Li+, forming a nitrogen-rich SEI layer.
• CDI promotes PF6- anion decomposition, increasing LiF production and interfacial stability.
• Gr||LFP pouch cells with CDI additive showed an 18% improvement in capacity retention after 1000 cycles at 45 °C.

Conclusions:

• Molecular design of electrolyte additives can effectively control SEI composition and robustness.
• CDI is a promising additive for creating stable SEI layers in Gr||LFP LIBs.
• This approach offers a pathway to formulating electrolytes for long-lifespan lithium-ion batteries.