CD Laboratory for Solid-State Batteries

Solid-state batteries are regarded as the energy storage system of the future. However, high resistances currently form at interfaces within the battery. This CD Laboratory is researching these interfaces in order to derive an optimised battery design.

A key challenge in the near future will be to reduce our dependence on fossil fuels and to make transport efficient and low-emission in the future and the energy industry sustainable. This will require new energy storage systems to efficiently store the electricity generated from renewable energy sources (e.g. solar, wind and water). There are therefore major endeavours to develop new lithium-ion battery storage systems with high energy and power densities that meet the increasing requirements of new technologies.

To achieve this, it is necessary to increase the battery voltage, for example. This can be achieved by using lithium metal (Li) and nickel-rich cathode materials.

Unfortunately, conventional liquid electrolytes are not stable in the required extreme potential ranges. Furthermore, rapid charging of the battery can lead to preferential Li deposition and thus to the formation of so-called dendrites. These dendrites can lead to a short circuit and trigger a cascade of chemical reactions which, in the worst case, can cause the lithium-ion battery to ignite. The use of Li has therefore been one of the major challenges in the field of battery research for decades.

Solid-state electrolytes represent a promising solution here, which would enable lithium-ion batteries with gravimetric and volumetric energy densities of around 500 Wh/kg and 1000 Wh/kg. These energy densities could enable a continuous journey of 700 kilometres in an electric car. For this reason, intensive research has been carried out in recent years on solid-state electrolytes and materials have been developed that have conductivities similar to those of liquid electrolytes.

However, when solid-state electrolytes were implemented in lithium-ion batteries, a significant increase in internal resistance was observed. The increase in internal resistance can be attributed to the high interfacial resistances between (a) the solid electrolyte and the electrode materials, (b) grains of the electrolyte (grain boundaries), and (c) ceramic particles and the polymer in composite electrolytes.

The CD Laboratory for Solid State Batteries is dedicated to precisely these interfaces. In the first phase of the laboratory, the various interfaces are analysed in detail in order to identify the factors that lead to good or poor interfaces. Optimisation strategies are then derived from this, which are used in the second phase of the laboratory to assemble and test new cell architectures. Due to the great relevance of interfaces in batteries, the CD Laboratory will make a significant contribution to the development of solid-state batteries as the next generation of energy storage systems.