Vertically Aligned Hollow Mesoporous Silica Rods Enabling Composite Polymer Electrolytes with Fast Ionic Conduction for Lithium Metal Batteries

Incorporation of inorganic fillers into polymer matrices to design composite polymer electrolytes is considered as a promising strategy for high performance lithium metal batteries. However, the randomly dispersed fillers in the polymer matrices can cause tortuous ionic channels and increase the transport distance, resulting in the decrease of ion transport capacity. Herein, composite polymer electrolytes with vertically aligned channels are fabricated under the assistance of a magnetic field during the UV-induced polymerization. The vertically aligned rods are formed through controlling the direction of the magnetic field. The construction of the aligned ionic pathways can effectively reduce the transport distance of Li ions in the electrolytes, while the hollow mesoporous silica rods can provide space for absorbing electrolyte, consequently enhancing the electrochemical kinetics. The aligned interfaces provide Lewis acid sites for trapping the anions of Li salt to facilitate the enhancement of Li ion transference number. More significantly, the Li/Li symmetrical cells based on the composite electrolyte exhibit a stable voltage plateau over 1500 h due to the uniform distribution of Li-ion flux in the unique low-tortuosity structure, and the assembled LiFePO₄/Li cells show outstanding rate capability and cycling stability.