Polymer nanofibers framework composite solid electrolyte with lithium dendrite suppression for long life all-solid-state lithium metal battery

The widespread deployment of lithium metal battery is limited by inhomogeneous electrodeposition of lithium metal (the growth of lithium dendrite), leading to pulverization, “dead” lithium and the unrestricted volume expansion of lithium metal anode. Owing to the high elastic modulus, thermal stability and electrochemical stability of polyimide, we design a novel composite solid polymer electrolyte blending with polyimide fibers framework paper. Polyimide fibers scaffold improves elastic modulus and tensile strength of composite electrolyte film. Effective ion transport network layers in electrolyte system are formed by adding polyimide fibers due to strong interaction between electron-withdrawing atoms and groups in the lithium salt for accelerating the dissociation of the lithium salt. Thus, polyimide composite electrolyte shows higher Li⁺ transfer number (∼2 times) than pure polyethylene oxide electrolyte, which is beneficial to regulate Li deposition for lithium dendrites inhibition. The electrochemical window of polyimide composite electrolyte is widened to 4.87 V after introducing stable physicochemical fibers framework, leading to high compatibility and stability with lithium metal anode. Therefore, the Li symmetrical battery with polyimide fibers framework composite electrolyte delivers low overpotential and long cycling life at different current densities. And the all-solid-state Li/LiFePO₄ battery using this composite electrolyte reveals long cycling life (418 cycles), high Coulomb efficiency (99.97%), high capacity retention of 89.5% at 0.3 C, and good rate performance at 60 °C.