Electrochemical performance enhancement mechanism of CTMS modulating on LLZTO/PEO composite solid electrolyte interface

With the rapid development of solid state battery technology, composite electrolytes, as a key material for enhancing battery performance, face poor interfacial compatibility issues between inorganic fillers and the polymer matrix , which becomes a bottleneck restricting the improvement of electrochemical properties of the electrolyte. To address the issues of low ionic transport efficiency and the growth of lithium dendrites , which are triggered by the poor interfacial compatibility, this paper introduces the silane coupling agent (3-chloropropyl) trimethoxysilane (CTMS) into the PEO-LLZTO composite solid electrolytes to bridge the inorganic filler and polymer matrix through an in-situ coupling reaction, thereby enhancing the performance of the composite electrolyte. Its ionic conductivity is 1.84 × 10 −3 S/cm at 60°C, and the stability to lithium anode is improved, with a polarization voltage of only 0.017 V and ultra-long lithium symmetrical battery constant current cycle exceeding 1670 h. The assembled full battery exhibited excellent rate performance and cycle stability at 60°C under 0.2 C, its specific capacity remains 138.52 mAh/g after 135 cycles. The mechanism of CTMS enhancing electrolyte properties was investigated by density functional theory (DFT). The adsorption energy , differential charge density, and ELF are calculated to analyze the interaction between the electrolyte components. DFT calculation results suggest that O-Si-O bonds are readily formed at the LLZTO/PEO interface upon the addition of CTMS. More importantly, CTMS modifies the charge distribution of the space charge layer at this interface, effectively facilitating the migration of lithium ions , thereby optimizing the ionic transport properties at the interface. Both experimental and DFT results indicate that CTMS forms a strong chemical bond between the inorganic and polymer segments , which creates a rapid transport channel for lithium ions and reduces the migration of the lithium salt anion group, thereby improving the electrochemical performance of the electrolyte.