Electrolyte for lithium secondary batteries containing N-(4-fluorophenyl)maleimide and lithium secondary batteries comprising the same

Electrolyte for simultaneous stabilization of cathode and anode interfaces using a dual-functional FPMI additive

This technology introduces N-(4-fluorophenyl)maleimide (FPMI), a dual-functional additive, into lithium secondary battery electrolytes. It enhances interface stability by forming an N-C=O functional group-based CEI on the cathode via oxidation and an LiF and N-C=O functional group-based SEI on the anode via reduction.

In high-energy-density secondary batteries using Ni-rich NMC cathodes and SiOx anodes, unstable electrode interfaces lead to continuous electrolyte decomposition, metal dissolution, anode volume expansion, and pulverization, which degrade cycle life.

This technology involves adding 0.5–5.0 wt% of FPMI to the electrolyte. Upon reduction, it forms an SEI layer on the anode containing high-mechanical-strength LiF and N-C=O functional groups, and upon oxidation, it forms a CEI layer on the cathode containing N-C=O functional groups. This suppresses both anode pulverization and cathode-electrolyte parasitic reactions. It can be applied to long-range EV cells combining high-nickel cathodes and silicon-based anodes, offering process advantages by managing degradation at both electrodes with a single additive.

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Key Features:

• Electrolyte for lithium secondary batteries comprising an N-(4-fluorophenyl)maleimide (FPMI) additive, a solvent, and a lithium salt
• FPMI additive that forms LiF and N-C=O functional groups via electrochemical reduction and N-C=O functional groups via oxidation
• Additive containing fluoro and maleimide functional groups, present at 0.5 wt% to 5.0 wt% of the total electrolyte weight
• Solid electrolyte interphase (SEI) layer formed between the anode and electrolyte layer, containing N-C=O and LiF functional groups

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