Application of a Modified Porphyrin in a Polymer Electrolyte with Superior Properties for All-Solid-State Lithium Batteries

Porphyrins and their derivatives are a unique class of multifunctional and modifiable π-conjugated heterocyclic organic molecules, which have been widely applied in the fields of optoelectronic devices and catalysis. However, the application of porphyrins in polymer electrolytes for all-solid-state lithium-ion batteries (ASSLIBs) has rarely been reported. Herein, porphyrin molecules modified by polyether chains are used for composite solid-state polymer electrolytes (CSPEs) for the first time. The introduction of a modified porphyrin in an electrolyte can not only promote the electrochemical properties by constructing ordered ion channels via the intermolecular interaction between π-conjugated heterocyclic porphyrins, but also significantly improve the mechanical strength and interface contact between the electrolyte membrane and the lithium metal anode. Consequently, the all-solid-state batteries assembled by the modified porphyrin composite polymer electrolyte, LiFePO4 cathodes, and Li anodes deliver a higher discharge capacity of 158.2 mA h g-1 at 60 °C, 0.2 C, which remains at 153.6 mA h g-1 after 120 cycles with an average coulombic efficiency of ∼99.60%. Furthermore, the flexible porphyrin-based composite polymer electrolyte can also enable a Li || LiCoO2 battery to exhibit a maximum discharge capacity of 108.6 mA h g-1 at 60 °C, 0.1 C with an active material loading of 2-3 mg cm-2, which is unable to realize for the corresponding batteries with a pure PEO-based polymer electrolyte. This work not only broadens the application scope of porphyrins, but also proposes a novel method to fabricate CSPEs with improved electrochemical and mechanical properties, which may shed new light on the development of CSPEs for next-generation high-energy-density lithium-ion batteries.