Magnesium Borate Fiber Coating Separators with High Lithium-Ion Transference Number for Lithium-Ion Batteries

In this work, magnesium borate fiber (MBO) is used as a functional ceramic to coat onto a polypropylene (PP) separator (MBO@PP). This MBO coating layer increases the lithium-ion transference number (t(Li+)) from 0.24 to 0.57 in the LiPF6-based electrolyte due to the MBO acting as Lewis acid sites interacts with Lewis base PF6- . The increase in the t(Li+) reduces the concentration polarization and promotes the migration of lithium ions. Besides, the prepared MBO@PP separator has better wettability with liquid electrolyte, the electrolyte uptake as well as thermal stability. The LiFePO4 half-coin with MBO@PP separator not only had better cycle stability, but also had a higher capacity retention rate at high current.