Electrolyte Volume Effects on Electrochemical Performance and Solid Electrolyte Interphase in Si-Graphite/NMC...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Silicon-graphite composite anodes are promising for high-energy lithium-ion batteries.
• Electrolyte volume significantly influences battery performance and degradation mechanisms.
• Understanding the solid electrolyte interphase (SEI) is key to improving battery longevity.

Purpose of the Study:

• To investigate the relationship between electrolyte volume, electrochemical performance, and SEI properties in pouch cells.
• To determine the optimal electrolyte volume for enhanced cycling stability.
• To analyze the impact of electrolyte deficiency on cell resistances and dendrite formation.

Main Methods:

• Fabrication of single-layer pouch cells (100 mA h) with Si-graphite anodes and LiNi0.5Mn0.3Co0.2O2 cathodes.
• Use of 1.2 M LiPF6 in EC:EMC with 10 wt% FEC electrolyte.
• Systematic variation of electrolyte volume factor and electrochemical testing.

Main Results:

• A minimum electrolyte volume factor of 3.1 is required for optimal cycling stability.
• Lower electrolyte volumes increase ohmic and charge transfer resistances, particularly from the anode.
• Lithium dendrites form at low electrolyte volumes; SEI thickness increases with electrolyte volume but remains nonuniform.

Conclusions:

• Electrolyte volume is a critical parameter for achieving stable cycling in Si-graphite pouch cells.
• Electrolyte deficiency accelerates degradation through increased resistance and lithium dendrite growth.
• Optimizing electrolyte volume is essential for reliable solid electrolyte interphase formation and battery lifespan.