Borate-containing triblock copolymer electrolytes for improved lithium-ion transference number and interface...

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• High lithium-ion transference number (t_Li+) is crucial for improving lithium-ion battery (LIB) performance by reducing concentration polarization.
• Developing stable and efficient solid-state electrolytes is key for safer and high-performance LIBs.

Purpose of the Study:

• To synthesize and characterize novel triblock copolymer electrolytes (PBOEE) containing borate groups for LIBs.
• To investigate the effect of sp² hybridized boron atoms on anion anchoring and lithium-ion transference.
• To evaluate the electrochemical performance, ionic conductivity, and stability of the developed electrolytes.

Main Methods:

• Synthesis of triblock copolymer electrolytes (PBOEE) incorporating borate groups.
• Measurement of lithium-ion transference number (t_Li+) and ionic conductivity.
• Electrochemical testing of Li symmetric cells and LiFePO₄/PBOEE/Li full cells.
• Analysis of solid electrolyte interphase (SEI) formation and electrochemical stability.

Main Results:

• PBOEE electrolytes achieved a high t_Li+ of up to 0.53 due to borate groups anchoring anions.
• Borate groups promoted stable, organic-rich SEI film formation, enabling Li symmetric cell cycling for over 3100 hours.
• Optimized PBOEE_24 demonstrated ionic conductivity of 1.41 × 10^-4 S cm^-1 and electrochemical stability window of 4.8 V.
• LiFePO₄/PBOEE_24/Li cells showed excellent capacity retention (85% after 600 cycles at 0.5C) at 50 °C.

Conclusions:

• Triblock copolymers containing sp² hybridized boron atoms are effective in enhancing lithium-ion transference and battery performance.
• The developed PBOEE electrolytes show promise as stable, high-performance all-solid-state polymer electrolytes for advanced LIBs.
• Borate functionalization is a viable strategy for designing next-generation solid-state electrolytes.