A microscopically heterogeneous colloid electrolyte of covalent organic nanosheets for ultrahigh-voltage and low-temperature lithium metal batteries

Abstract

Current electrolytes often struggle to meet the demands of rechargeable batteries under various working conditions. A general electrolyte design strategy that can cater to battery application scenarios is needed. Herein, we report a microscopically heterogeneous electrolyte, viz., a covalent organic nanosheet (CON) colloid, with the hope that it can adapt to various conditions. A typical CON colloid electrolyte is investigated as a proof of concept for working under harsh operating conditions of high working voltage and low temperatures. Both computational and experimental results reveal that the presence of mesoscopic CONs can tune the microscopic Li⁺ solvation structure through the host–guest interaction at the meso–micro multiscale. As a result, the CON colloid electrolyte enables a more stable Li|LiNi_0.8Mn_0.1Co_0.1O₂ cell cycling at an ultrahigh upper cut-off voltage of 4.7 volt than the commercial one at room temperature. More to the point, the colloid electrolyte endows the 4.6-volt-class Li|LiNi_0.8Mn_0.1Co_0.1O₂ cell with a high capacity retention of 80.7% after 700 cycles at −20 °C. Thanks to the designable structure of CONs, we believe that the colloid electrolyte featuring a multiscale structure paves a way to develop electrolytes for lithium metal batteries (LMBs) and other alkali-ion/metal batteries.