"Magnetic Levitation" for Ions: Fuzhou University Team Enables Near-Frictionless Li+ Transport in Polymer Electrolytes via "Mechanical Balance" DesignIntroduction: The "Sticky" Problem of Solid Poly
- Technical Research
- Jan 7
- 3 min read
Solid Polymer Electrolytes (SPEs) are considered the ideal "blood" for solid-state batteries due to their flexibility and ease of processing. However, in the microscopic world, Lithium ions (Li⁺) struggle to move through the polymer matrix.
This is because of the strong attractive interaction between Li⁺ and polymer chains (like ether-oxygen groups). Li⁺ moves as if on a "sticky mud track," requiring significant energy (decoupling energy barrier) to break free and hop to the next site. Combined with the tortuous, disordered polymer chains, this results in extremely low room-temperature ionic conductivity (10^{-5} S/cm range) for traditional SPEs.
Recently, a team led by Prof. Yun Zheng and Academician Jiujun Zhang from Fuzhou University published a breakthrough in JACS. Inspired by the "Mechanical Balance" principle in physics (similar to maglev trains), they designed a novel electrolyte strategy that enables near-"frictionless," ultra-fast Li⁺ transport.
Core Mechanism: Suspending Ions via Mechanical Balance
To make Li⁺ move faster, traditional methods try to modify the "track" (the polymer), with limited success. This team proposed a physical approach: Instead of just reducing the track's stickiness, apply an opposing pulling force to Li⁺.
Introducing Anchors: The team introduced ZIF-8 (a MOF) anchored with anion clusters (TFSI⁻) into the electrolyte.
Creating a Balance Zone: While the polymer chain attracts Li⁺ ($F_{polymer}$), the anchored anion cluster exerts an opposing electrostatic attraction ($F_{anion}$). When these two forces reach a dynamic balance ($F_1 \approx F_2$), the Li⁺ is effectively "suspended" in the middle—neither stuck to the polymer nor trapped by the anion.
Near-Zero Barrier: This balanced state drastically lowers the decoupling energy barrier, placing Li⁺ in a highly free metastable state where it can easily "slide" to the next site.
Structural Innovation: From Winding Roads to Straight Highways
Solving the "stickiness" isn't enough; the "tortuous path" issue also needs addressing. Traditional ion channels are chaotic and winding.
Directional Alignment: The researchers used Fluorinated Graphene (FG) and ZIF-8 to build a directionally aligned scaffold.
In-Situ Polymerization: 1,3-dioxolane (DOL) was polymerized in-situ within this scaffold to form the Directionally Aligned Mechanical Balance Polymer Electrolyte (DAMB-PE).
This constructs microscopic straight highways, allowing Li⁺ to sprint along a direct path rather than taking detours.
Performance Breakthrough: High Conductivity & Long Life
Powered by "Mechanical Balance" and "Directional Alignment," DAMB-PE exhibits stunning performance, validated in Li||LFP and Li||NCM523 batteries:
Ultra-High Conductivity: 1.2 mS/cm at room temperature (1-2 orders of magnitude higher than traditional polymers).
High Transference Number: 0.71 (vs. <0.4 traditionally), meaning Li⁺ contributes the majority of the current, reducing polarization.
Long Cycle Life: Li||LFP quasi-solid-state batteries retained 81% capacity after 3500 cycles at 4C; Li||Li symmetric cells ran stably for over 2400 hours.
High Voltage Compatibility: Electrochemical window expanded to 5.17 V.
Conclusion
This work not only develops a high-performance electrolyte but also establishes a new paradigm of "Physics-Assisted Chemical Design." By engineering a mechanical balance zone at the microscopic level, ions can move through solids as freely as in liquids. This offers a promising solution for high-energy, fast-charging, and long-life solid-state batteries.
Literature Information
Song Duan, et al., Directionally Aligned “Mechanical Balance” Design Enables Near-Frictionless Li+ Transport in Polymer Electrolytes, J. Am. Chem. Soc. (2025). DOI: 10.1021/jacs.5c13961
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