Organic Polymer Framework Enhanced PEO-Based Electrolyte for Fast Li+ Migration in All-Solid-State Lithium-ion Batteries†

Abstract

With the rapid development of solid-state batteries, solid-state polymer electrolytes (SPEs) have attracted widespread attention due to their excellent environmental friendliness, designability, and forming film ability. However, due to the limited conductive path of polymers, lithium-ion diffusion kinetics are limited, and low ion conductivity is a huge challenge for SPEs in practical applications. This work provides a polyethylene oxide (PEO) based polymer electrolyte, which has multiple paths of ion diffusion caused by organic polymer framework of poly(hexaazatrinaphthalene) (PHATN). The unique porous channel, the specific surface characteristics, the coordination of -C=N- groups in PHATN with Li⁺, combined with the mobility of PEO segments, make the SPEs have a good ability to conduct Li⁺. Interestingly, the PHATN-PEO/lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) composite electrolytes exhibit excellent electrochemical properties. At room temperature, the conductivity of PHATN-PEO electrolyte can reach 1.03 × 10^–4 S·cm^–1, which is greatly improved compared with 3.9 × 10^–6 S·cm^–1 of PEO. Delightedly, the lithium-ion transference number of PHATN-PEO electrolyte achieves 0.61, and the electrochemical window increases to 4.82 V. The LFP/1%PH-PEO/Li solid-state batteries show good electrochemical cycles. This work reveals an efficient stratagem for the design of polymer solid-state electrolytes.