Long-Life Lithium Metal Batteries Enabled by In Situ Solidified Polyphosphoester-Based Electrolyte

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Lithium metal batteries (LMBs) face challenges with dendrite formation and poor electrochemical stability due to liquid electrolytes (LEs) and unstable solid electrolyte interphase (SEI).
• Imbalanced ion distribution in LEs leads to mechanically weak SEI, exacerbating dendrite growth and limiting LMB practical applications.

Purpose of the Study:

• To design a novel electrolyte system for LMBs that overcomes limitations of current liquid electrolytes.
• To improve lithium-ion transference and the stability of the solid electrolyte interphase (SEI) for enhanced battery performance and safety.

Main Methods:

• A polyphosphoester electrolyte (PPUM-PE) was synthesized using a dual-ion regulation strategy.
• The electrolyte's ability to anchor anions and reconstruct Li+ solvation architecture was investigated.
• The properties of the bilayer SEI formed on lithium anodes were analyzed, including its composition and mechanical strength.

Main Results:

• The PPUM-PE electrolyte achieved a high Li+ transference number of 0.82 and improved reductive stability.
• A robust bilayer SEI, composed of an outer polymer layer and an inner LiF-enriched inorganic phase, effectively suppressed Li dendrite propagation.
• LMBs with LiFePO4 cathodes demonstrated 91.28% capacity retention after 1000 cycles at 1C, showing excellent cycling stability.

Conclusions:

• The dual-ion synergistic regulation strategy in PPUM-PE effectively addresses key challenges in LMBs, including dendrite formation and electrochemical instability.
• The developed electrolyte shows promise for high-energy-density LMBs, with good compatibility with high-voltage cathodes and improved thermal safety.
• This work presents a scalable pathway for advancing the practical application of high-performance lithium metal batteries.