An entanglement association polymer electrolyte for Li-metal batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Improving interface stability between Li-rich Mn-based oxide cathodes and electrolytes is crucial for advanced battery technologies.
• Current polymer electrolytes face challenges in maintaining stability and preventing dendrite growth during battery cycling.

Purpose of the Study:

• To develop a novel entanglement association polymer electrolyte (PVFH-PVCA) for enhanced interface stability in Li-rich cathode applications.
• To investigate the structural and electrochemical properties of the PVFH-PVCA electrolyte and its impact on battery performance.

Main Methods:

• Synthesis of a PVFH-PVCA polymer electrolyte using poly(vinylidene fluoride-co-hexafluoropropylene) (PVFH) and a copolymer stabilizer (PVCA).
• Characterization of the electrolyte's mechanical properties, interface layer formation, and electrochemical stability.
• Testing of Li//Li symmetric cells and Li-rich cathode full cells (Li$_{1.2}$Mn$_{0.56}$Ni$_{0.16}$Co$_{0.08}$O$_{2}$) using the developed electrolyte.

Main Results:

• The entangled structure of PVFH-PVCA provides excellent mechanical properties and suppresses dendrite growth, enabling stable cycling of Li//Li cells for over 4500 hours.
• The PVCA component promotes a robust cathode-electrolyte interphase, leading to high specific capacity and 84.7% capacity retention after 400 cycles.
• A full cell achieved 125 cycles at 1 C with a stable discharge capacity of ~2.5 mAh cm$^{-2}$ at a 4.8 V cut-off.

Conclusions:

• The PVFH-PVCA entanglement association polymer electrolyte offers a promising solution for improving the interface stability and cycling performance of Li-rich cathode batteries.
• The unique entangled structure and stabilizing effect of PVCA contribute significantly to the enhanced electrochemical properties and long-term stability.
• This development paves the way for more durable and efficient next-generation lithium-ion batteries.