Quasi-solid-state electrolyte for ultra-high safety and cycle stability battery

Abstract

All-solid-state lithium batteries (ASSLB) have been regarded as the most promising candidate to achieve the next generation energy storage with high energy and high safety. However, some bottlenecks, including high interfacial resistance, bad electrochemical stability, and low conductivity, have hindered its further development. Here, we developed a Pyr13FSI/LiFSI-based gel electrolyte and used it in the LFP/LTO full battery system to achieve a lithium-ion battery with high safety and cycle stability. The presence of ionic liquid in the electrolyte reduces the crystallinity of PVDF-HFP polymer matrix, increases the ion conductivity of the electrolyte, and greatly improves the electrode-electrolyte interface contact. These advantages enable the battery to work at room temperature and reach a specific capacity of 123mAh/g at the current of 1C. The slightly change in interfacial resistances between the gel electrolyte and electrodes with the increase of the cycle numbers is confirmed through electrochemical impedance spectroscopy. The high electrochemical stability of the electrolyte in the LFP/LTO system makes the battery exhibit good cycle stability, and the battery maintains 80% of its initial capacity after 2000 cycles at the current of 1C. In addition, benefitting from the excellent properties of ionic liquids, such as non-flammability, negligible vapour pressure, and high conductivity, the obtained gel electrolyte based LFP/LTO pouch battery exhibits high safety and cycle stability.