Revealing and reconstructing the 3D Li-ion transportation network for superionic poly(ethylene) oxide conductor
Chengdong Fang, Ying Huang, Yifan Sun, Pengfei Sun, Ke Li, Shuyang Yao, Minyi Zhang, Wei‐Hui Fang, Jiajia Chen
Abstract
Understanding the Li-ions conduction network and transport dynamics in polymer electrolyte is crucial for developing reliable all-solid-state batteries. In this work, advanced nano- X-ray computed tomography combined with Raman spectroscopy and solid state nuclear magnetic resonance are used to multi-scale qualitatively and quantitatively reveal ion conduction network of poly(ethylene) oxide (PEO)-based electrolyte (from atomic, nano to macroscopic level). With the clear mapping of the microstructural heterogeneities of the polymer segments, aluminium-oxo molecular clusters (AlOC) are used to reconstruct a high-efficient conducting network with high available Li-ions (76.7%) and continuous amorphous domains via the strong supramolecular interactions. Such superionic PEO conductor (PEO-LiTFSI-AlOC) exhibites a molten-like Li-ion conduction behaviour among the whole temperature range and delivers an ionic conductivity of 1.87 × 10−4 S cm−1 at 35 °Ϲ. This further endows Li electrochemical plating/stripping stability under 50 μA cm−2 and 50 μAh cm−2 over 2000 h. The as-built Li|PEO-LiTFSI-AlOC|LiFePO4 full batteries show a high rate performance and a capacity retention more than 90% over 200 cycling at 250 μA cm−2, even enabling a high-loading LiFePO4 cathode of 16.8 mg cm−2 with a specific capacity of 150 mAh g−1 at 50 °Ϲ. The sluggish ionic conductivity of polymer electrolytes has been a long-standing concern. Here, authors present a multiscale study of the lithium ion conduction network of poly(ethylene) oxide-based electrolytes and elucidate how aluminium-oxo molecular clusters improve the transport properties.