Improving the Electrochemical Stability of a Polyester-Polycarbonate Solid Polymer Electrolyte by Zwitterionic...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Rechargeable batteries utilizing solid polymer electrolytes (SPEs), lithium-metal anodes, and high-voltage cathodes such as LiNiMnCoO2 (NMC) are key for next-generation high-energy-density storage.
• These advanced battery systems often suffer from rapid degradation during cycling, characterized by voltage fluctuations.
• The interface between the polymer electrolyte and the high-voltage cathode is a critical area for stability issues.

Purpose of the Study:

• To investigate the impact of two imidazolium-based zwitterions as additives on the electrochemical stability and cycling performance of SPEs.
• To evaluate the effectiveness of these additives in mitigating degradation pathways in NMC-based half-cells.
• To understand the role of additive chain length in enhancing electrolyte and battery performance.

Main Methods:

• Electrochemical stability was assessed using cyclic voltammetry and staircase voltammetry on inert electrodes.
• Cutoff increase cell cycling (CICC) was employed to study the specific interactions between the NMC cathode and the SPE.
• X-ray photoelectron spectroscopy (XPS) was utilized to analyze the chemical composition at the polymer-cathode interface.

Main Results:

• The zwitterionic additives demonstrated enhanced oxidative stability of the poly(ε-caprolactone-co-trimethylene carbonate):LiTFSI electrolyte.
• Improved galvanostatic cycling stability was observed in NMC half-cells when these additives were incorporated.
• XPS analysis indicated that the additives prevent the decomposition of LiTFSI at the polymer-cathode interface.

Conclusions:

• Imidazolium-based zwitterions are effective cycling-enhancing additives for solid polymer electrolytes in high-energy-density batteries.
• These additives improve the electrochemical stability of the electrolyte and the cycling performance of NMC cathodes.
• The findings suggest a viable strategy to enhance the durability of advanced rechargeable battery systems.