Polymer Precursor Derived LiPON Electrolytes: Toward Li-S Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• All solid-state batteries (ASBs) require stable electrolytes with high ionic conductivity.
• Lithium phosphorus oxynitride (LiPON) glasses are a benchmark for solid electrolytes but can be challenging to process.
• Developing polymer precursors for LiPON-like coatings is crucial for scalable ASB fabrication.

Purpose of the Study:

• To synthesize polymer precursor electrolytes with properties comparable or superior to LiPON glasses.
• To enable the processing of LiPON-like thin glass/ceramic coatings for ASBs.
• To investigate the relationship between lithiation, polymer structure, and ionic conductivity.

Main Methods:

• Synthesis of oligomers/polymers via lithiation of phosphorus-nitrogen compounds.
• Tuning Li+ content through treatment with lithium amide (LiNH2).
• Characterization of ionic conductivity and thermal stability of polymer electrolytes.
• Fabrication and testing of a lithium-sulfur (Li-S) battery using the developed polymer electrolyte.

Main Results:

• Synthesized polymer electrolytes with degrees of polymerization from 5 to 20.
• Achieved Li+ conductivities up to ~1 × 10^-5 S cm^-1 at room temperature.
• Demonstrated thermal stability up to ~150 °C.
• Li-S battery showed an initial reversible capacity of 1500 mAh g^-1 and excellent cycling stability over 120 cycles.

Conclusions:

• Developed polymer electrolytes offer a promising alternative to LiPON for ASB applications.
• The synthesized materials exhibit good ionic conductivity, thermal stability, and electrochemical performance in Li-S batteries.
• These polymer precursors facilitate the creation of LiPON-like coatings for advanced solid-state battery technologies.