Towards N-rich solid polymer electrolytes for Li-ion batteries?

Abstract

Solid polymer electrolytes (SPEs) are faced with many specifications to replace today's liquid organic electrolyte in Li-ion batteries. In this paper, a branched polyethyleneimine (BPEI) is proposed as a new SPE. Infrared and ¹³C NMR spectroscopy and DFT modelling were combined to clarify the ionic conduction mechanisms and performance of this new kind of polymer electrolyte. To improve its mechanical properties, the BPEI was semi-interpenetrated in a PEO-based network. Afterwards to provide mechanical integrity and efficient ionic transport, inorganic fillers of different natures were added into the membranes: Al₂O₃, SiO₂, ZrO₂ and LAGP. For instance, the addition of 10 wt% SiO₂ resulted in an enhancement in ionic conductivity, reaching 2.2 × 10⁻⁴ S cm⁻¹ at 80 °C. Furthermore, in a symmetric cell, improved cycling facing lithium metal, with a stable response over hundreds of hours without polarization, regardless of filler nature was observed.