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Abstract:A new type of high-temperature stable and self-supporting composite separator for lithium-ion batteries was developed consisting of custom-made ultrathin micrometer-sized glass platelets embedded in a glass fiber nonwoven together with a water-based sodium alginate binder. The physical and electrochemical properties were investigated and compared to commercial polymer-based separators. Full-cell configuration cycling tests at different current rates were performed using graphite and lithium iron phosphate as electrode materials. The glass separator was high-temperature tested and showed a stability up to at least 600 • C without significant shrinking. Furthermore, it showed an exceptional wettability for non-aqueous electrolytes. The electrochemical performance was excellent compared to commercially available polymer-based separators. The results clearly show that glass platelets integrated into a glass fiber nonwoven performs remarkably well as a separator material in lithium-ion batteries and show high-temperature stability.

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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 LiPF 6 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.

A new type of separator for lithium-ion batteries (LIBs) has been developed using ultrathin micrometer-sized sodium borosilicate glass platelets coated directly on a battery electrode with a water-based binder. The coating process is described in detail, demonstrating coating thicknesses of the glass separator of less than 50 µm. The high-temperature stability has been investigated and it has been shown that the separator is dimensionally stable to at least 600 °C. With regard to the electrochemical performance, full-cell tests on graphite || lithium iron phosphate cells showed a very good behavior, according to which comparable properties of the electrode/separator compound to a commercial polymer-based separator were achieved. This glass separator/electrode composite shows an interesting property profile and is a temperature-stable alternative to conventional polymer-based separators.