Seminar - Complex hydride solid-state electrolytes for Li, Na and Mg batteries by Dr. Ruben-Simon Kühnel
日期：2017 年 04 月 25 日 ( 星期二)
Time：4:00 pm – 5:00 pm
The identification of a solid-state electrolyte that fulfills all the requirements to enable a competitive bulk-type all-solid-state battery remains a challenging task. The electrolyte should display high ionic conductivity, high thermal stability, good processability and importantly a large electrochemical stability window that ideally allows reversible plating of the conducted ion. Several electrolytes within the class of complex hydrides display such a favorable combination of battery relevant properties. Here, we will discuss our recent results for Li-, Na- and Mg-ion conductors. We identified several compositions within the lithium-amide borohydride (Li(BH4)1-x(NH2)x) system that display near room temperature conductivities of >6 mS/cm, comparable to the ones of typical carbonate-based liquid electrolytes used in commercial lithium-ion batteries. An Li4Ti5O12 half-cell based on such an electrolyte displays >60% capacity retention at 3.5 mA/cm2 (5C) and stable cycling for 400 cycles. The mixed closo-borate Na2(B12H12)0.5(B10H10)0.5 displays a conductivity of 0.9 mS/cm at 20 °C, excellent thermal stability of up to 300 °C and an electrochemical stability window of 3 V that enables reversible plating of sodium. We will also report on the preparation and characterization of magnesium ethylenediamine borohydride (Mg(en)1(BH4)2), which displays a very high conductivity of 6×10-5 S/cm at 70 °C for a magnesium-ion solid-state electrolyte.
Bio-sketch: Dr. Kühnel is a postdoctoral researcher and project leader at Empa – Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland, where he is working on solid-state and aqueous electrolytes and their device integration. He joined the MEET Battery Research Center at Münster University, Germany in 2010 and received his PhD degree in 2014, supervised by Prof. Martin Winter. His PhD thesis is related to ionic liquid-based electrolytes and their application in supercapacitors and lithium-ion batteries.