Single‐Ion Polymer Electrolyte Based on Lithium‐Rich Imidazole Anionic Porous Aromatic Framework for High Performance Lithium‐Ion Batteries

Abstract

The low ionic conductivity and Li⁺ transference number ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>t</mml:mi> <mml:mrow><mml:mi>L</mml:mi> <mml:msup><mml:mi>i</mml:mi> <mml:mo>+</mml:mo></mml:msup> </mml:mrow> </mml:msub> <mml:annotation>${t}_{L{i}^ + }$</mml:annotation></mml:semantics> </mml:math> ) of solid polymer electrolytes (SPEs) seriously hinder their application in lithium-ion batteries (LIBs). In this study, a novel single-ion lithium-rich imidazole anionic porous aromatic framework (PAF-220-Li) is designed. The abundant pores in PAF-220-Li are conducive to the Li⁺ transfer. Imidazole anion has low binding force with Li⁺ . The conjugation of imidazole and benzene ring can further reduce the binding energy between Li⁺ and anions. Thus, only Li⁺ moved freely in the SPEs, remarkably reducing the concentration polarization and inhibiting lithium dendrite growth. PAF-220-quasi-solid polymer electrolyte (PAF-220-QSPE) is prepared through solution casting of Bis(trifluoromethane)sulfonimide lithium (LiTFSI) infused PAF-220-Li and Poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP), and possessed excellent electrochemical performance. The electrochemical property are further improved by preparing all-solid polymer electrolyte (PAF-220-ASPE) via pressing-disc method, which has a high Li⁺ conductivity of 0.501 mS cm^-1 and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>t</mml:mi> <mml:mrow><mml:mi>L</mml:mi> <mml:msup><mml:mi>i</mml:mi> <mml:mo>+</mml:mo></mml:msup> </mml:mrow> </mml:msub> <mml:annotation>${t}_{L{i}^ + }$</mml:annotation></mml:semantics> </mml:math> of 0.93. The discharge specific capacity at 0.2 C of Li//PAF-220-ASPE//LFP reached 164 mAh g^-1 , and the capacity retention rate is 90% after 180 cycles. This study provided a promising strategy for SPE with single-ion PAFs to achieve high-performance solid-state LIBs.