Lightweight Electrolyte Design for Li/Sulfurized Polyacrylonitrile (SPAN) Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Sulfurized polyacrylonitrile (SPAN) is a promising cathode material for high-energy lithium (Li) metal batteries, offering high capacity and long cycle life without transition metals.
• Li/SPAN batteries are sensitive to electrolyte weight, impacting specific energy density due to low electrode weights.
• Volume changes in Li metal anodes and SPAN cathodes necessitate robust inorganic interphases for stability.

Purpose of the Study:

• To design a low-density electrolyte to enhance the specific energy density of Li/SPAN batteries.
• To improve the stability and cyclability of Li/SPAN batteries through optimized electrolyte composition.
• To ensure the safety and protective capabilities of the electrolyte for both anode and cathode.

Main Methods:

• Formulation of a concentrated lithium bis(fluorosulfonyl)imide (LiFSI)-triethyl phosphate (TEP) solution with dibutyl ether (DBE) as a lightweight diluent.
• Characterization of the electrolyte's density, solvation structure, and performance in Li/SPAN battery cells.
• Evaluation of interphase formation, electrolyte consumption, cell cyclability, and thermal abuse protection.

Main Results:

• The designed electrolyte has a density of 1.04 g mL⁻¹, which is 40%-50% lighter than conventional localized high-concentration electrolytes (LHCEs).
• This reduction in electrolyte weight leads to a 12%-20% increase in specific energy density at the cell level.
• The electrolyte promotes the formation of favorable anion-derived inorganic interphases, minimizes electrolyte consumption, and enhances cell cyclability and thermal stability.

Conclusions:

• The lightweight DBE-diluted electrolyte significantly boosts the energy density of Li/SPAN batteries.
• The electrolyte's unique solvation structure enhances interphase formation and protects battery components, improving cycle life.
• This electrolyte design offers a viable strategy for developing high-performance and safer lithium metal batteries.