Research & development - Leuven | About a week ago
Lithium-ion is the technology of choice for rechargeable battery applications as the Li-ion electrode chemistries provide the highest volumetric and gravimetric energy density known. Since its first introduction on the market by Sony in 1991, it took more than 20 years to double its energy density from 250Wh/L to 500Wh/L mainly by improvements in the electrode formulations. This evolution was primarily driven by the advent of portable electronics such as the smart phone. In the last few years, we have seen a push in energy density with the introduction of new electrode materials with higher intrinsic Li-ion storage capacity. State-of-the art cells today reach nearly 700Wh/L. This second wave in Li-ion technology developments is driven by the emerging electrical vehicle market. It is expected that further improvements can bring us to 800Wh/L in the first part of the 2020’s. For the next generation batteries, targeting 1000Wh/L, it is generally agreed that Li-metal anodes in combination with all-solid-state concepts will be needed. At imec, we are developing high conductivity solid nanocomposite electrolytes for solid-state Li-ion batteries. For the integration, we are using similar cathode and anode materials as currently used in wet batteries. Focus lays on interface control and mechanical stability. In a next step, lithium metal anodes will be considered. The integration of lithium has many technological issues. The potential formation of dendrites during recharging of the battery is, for example, a serious safety concern. Also, the planar geometry of a simple lithium foil poses issues towards rate performance as the current density is much larger than for the current graphite electrodes which have a large effective surface area. The fact that several microns of lithium are plated (appear) and de-plated (disappear) at the anode side is obviously not straightforward in the case of all solid-state architectures. Therefore, alloys with lithium and surface area enlargement by, for example, patterning are considered as potential solutions.
In this job, you will investigate and optimize the lithium plating and de-plating characteristics at the current collector/lithium (alloy)/ solid electrolyte interfaces. This learning will then lead to the development of conditions for control of lithium thickness, current density, electrical contact and morphology.