High-Performance Ionogels from Dynamic Polyrotaxane-Based Networks

The swelling of a polymer matrix by ionic liquids and additional lithium salts may lead to the formation of ionogel electrolytes. However, the introduction of additional ions usually results in a decreased lithium-ion transference number, because of the trapping of the lithium ions in clusters and polymer-ion complexes. Achieving highly efficient lithium-ion migration and increasing lithium-ion transference number (tLi+) are however crucial for the successful application of ionogel electrolytes. Herein, we design a crosslinked polyrotaxane network and then introduce ionic liquid and a lithium salt to obtain an ionogel electrolyte based on the principle of competitive coordination with the lowest binding energy for lithium ions coordinated with both the polymer network and ionic liquid clusters. This facilitates their migration within the ionogel and their release from the coordination environment, thereby improving lithium-ion transport efficiency (ionic conductivity of 2.2x10-3 S cm-1 and tLi+=0.45 at 20 degrees C). As proof of concept, the lithium-lithium symmetrical cells achieve stable cycling for 2000 hours, while the NMC622||Li battery demonstrates good rate performance and excellent cycling stability at 20 degrees C (theoretical initial capacity, 300 cycles with a single cycle capacity loss of 0.03 %). This work provides new insights for the design and synthesis of ionogel electrolytes, facilitating lithium ion migration within the electrolytes.