A compact overview on solid-state/ hybrid-solid-state battery research
In the solid-state battery design the conventionally used liquid electrolyte is substituted by a solid electrolyte, enabling the use of high performance anode materials such as lithium metal. The solid electrolyte is typically a glass, halide, chloride, ceramic, or polymer and serves both as a separator between cathode and anode as well as the ionic conductor in the cathode composite. Currently solid-state batteries can only be operated at low charging and discharging rates and fail after a few hundred cycles. The low performance and limited lifetime of these batteries are due to degradation mechanisms occurring during the battery operation. These can be summarized as electrochemical and mechanical degradation as well as short-circuit due to dendrites.
The mechanical degradation takes place in the cathode composite where stiff solid electrolytes are unable to compensate the volumetric changes of the active material upon battery operation leading to cracking along the grain boundaries and thus a capacity decrease. Therefore, in hybrid cell design, the cathode consists of a porous ceramic solid electrolyte skeleton structure, which ensures sufficiently high mechanical stability, into which polymer solid electrolyte and active material are infiltrated. The polymer is intended to compensate for the active materials volumetric changes upon cell operation and thus prevent a loss of capacity.
A ceramic solid electrolyte is usually used as a separator, as its high mechanical strength should make it difficult for dendrites to penetrate. However, ceramic-based solid-state batteries also suffer from premature failure due to short circuits caused by dendrites. In recent studies it was proposed that near-surface defects in the separator (pores, cracks) at the separator-anode interface enable the formation of dendrites, which propagate further into the separator by wedge cracking. This ultimately leads to fracture of the ceramic and a short circuit within the battery.
Our main research objectives in the battery research are the following:
Frontiers of material characterization: How can the properties of thin, porous, brittle, and air-sensitive ceramic tapes be reliably measured?
Prevention of battery failure: What properties should the solid electrolyte exhibit to prevent degradation and battery failure?
Linking the material processing to the microstructural and mechanical properties: How can material with predefined properties be achieved?
Dr. Jürgen Malzbender
Group Leader Ceramic Materials
- Institute of Energy Materials and Devices (IMD)
- Structure and Function of Materials (IMD-1)
Room 165
- Institute of Energy Materials and Devices (IMD)
- Structure and Function of Materials (IMD-1)
Room 169