Thermo-Mechano-Electrochemical Coupling Effect on Mechanical Evolution and Lithium Deposition in Gel Electrolyte...

The development of high-safety and high-energy-density energy storage technologies is crucial for advancing the transition to a cleaner energy system. The inherent safety hazards of traditional lithium-ion batteries with liquid electrolytes, such as flammability and leakage, limit their further application. Gel electrolytes show promise in enhancing battery safety, while the complex internal mechanical behavior during actual operation and its coupling mechanism with electrochemical performance remain unclear. For gel electrolyte batteries, this study innovatively employs in situ digital image correlation and optical microscopy, which enables a systematic investigation into the synergistic regulation of current density, temperature, external pressure, and cycle number on the evolution of the internal strain field and lithium deposition. The results demonstrate that the prepared gel electrolyte exhibits good compatibility: the Coulombic efficiencies of LiFePO₄||Li full cell remain stable at approximately 99% after 216 cycles at 0.2C, and the symmetric cell achieves cycling lifespan of 3115 h with low potential polarization under 0.3 mA·cm^-2. It is found that employing a low current density, moderate heating, and applying an external pressure can significantly improve the uniformity of the strain field in both the electrolyte and electrodes while effectively inhibiting dendrite growth. In contrast, an increased number of cycles exacerbates strain accumulation in the cathode, leading to a performance degradation. This study elucidates the mechanical behavior and performance degradation mechanism of gel electrolyte batteries and clarifies viable pathways for actively improving next-generation high-safety, long-life solid-state batteries through optimized charge-discharge strategies, thermal management, and the application of external mechanical constraints.