A novel study on COF-based semi-solid electrolyte for spinel LiNi_0.5Mn_1.5O₄ targeting transition metals migration

Cobalt-free battery is one of the development trends of lithium-ion batteries. High-voltage LiNi_0.5Mn_1.5O₄ (LNMO) with high theoretical energy density is one of the most promising Co-free cathode materials in the further. However, the side reaction between the LNMO electrode and electrolyte at high voltage or high temperature and the corresponding by-products (e.g. Mn²⁺/Mn³⁺ and Ni²⁺) severely deteriorate the battery performance. In this work, an anionic covalent organic framework (COF)–based semi-solid electrolyte was constructed by synthesizing a free-standing COF film with a small amount of liquid electrolyte. Further, the experimental results proved that the cycling and C-rate performance of LNMO battery is improved by using the semi-solid electrolyte. This can be proposed that the anionic COF is capable of absorbing strongly the Mn³⁺/Mn²⁺ and Ni²⁺ through Coulomb interaction, restraining their destructive migration to the anode. Therefore, this work will be beneficial to the commercialization of LNMO cathode material.