Sodium Borosilicate Glass Separators as an Electrolyte Additive Donor for Improving the Electrochemical Performance of Lithium-Ion Batteries

Abstract

In order to replace today's used electrochemical passive polymer-based lithium-ion battery separators, custom-made ultrathin micrometer-sized glass platelets are being tested as separators. Ions are leached from the glass by hydrofluoric acid (HF), which is typically present in LiPF6 containing electrolytes. The ions act as an electrolyte additive and show an effect on electrochemical cell parameters with progressing battery cycling. For comparability, different glass compositions are investigated and are compared to a commercial polymer-based separator. The separators are tested in a graphite || lithium iron phosphate full-cell configuration. Charge/discharge tests at different C-rates up to 10C, post-mortem analyses, impedance spectroscopy measurements, and distribution of relaxation times analyses are conducted to analyze the specific influence of the glass composition on cell aging. It is shown that in addition to the positive side effect of HF gettering, the ions from a sodium borosilicate glass cause a modification of the solid electrolyte interphase (SEI) with regard to its conductivity, thus improving the fast-charging capability and cycling stability of the battery cell.