Understanding the Superior Energy Density of Solid State Batteries

Why do solid state batteries seem to have an impressive energy density, often reaching up to 1200 Wh/liter, compared to traditional lithium-ion (Li-ion) batteries? This article delves into the reasons behind this significant difference and the potential of solid state batteries in the future of energy storage. The discussion will focus on the unique cell chemistries, the challenges associated with liquid electrolytes, and the advantages of solid state materials.

Advantages of Solid State Battery Chemistries

Different cell chemistries are the key to unlocking higher energy densities in solid state batteries. Specifically, a combination of a lithium metal anode and a high voltage cathode such as LMNO spinel can achieve energy densities ranging from 1000 to 1500 Whr/L and 300 to 600 Whr/kg, depending on the electrode loading. These impressive figures are not contingent upon the type of electrolyte, as long as the electrolyte and separator have a wide electrochemical stability window. However, there are additional challenges that need to be addressed for solid state batteries to reach their full potential.

Challenges with Liquid Electrolytes and Potential Solutions

The use of lithium metal as an anode in solid state batteries presents a significant issue: chemical reactions with organic liquids and the limited oxidative stability of these liquids. To overcome these problems, researchers are actively exploring additives that can address both issues. Moreover, liquid electrolytes cannot prevent the dendritic growth of lithium metal during cycling, a phenomenon that can lead to unstable battery operation and reduced lifespan.

Advantages of Solid State Materials

A material that possesses a wide electrochemical stability window and sufficient mechanical properties to prevent dendrite penetration represents a promising solution for solid state batteries. Certain oxide materials have been identified, which not only offer these properties but also facilitate the transport of ions and are stable in air. Consequently, these materials represent a significant advancement in the field of solid state batteries, overcoming the limitations posed by liquid electrolytes.

Addressing the Challenges of Thin Film Batteries

While the energy density of thin film solid state batteries is lower due to the small fraction of active materials compared to current collectors, there are practical advantages to this approach. Thin film batteries also face challenges due to the difficulties in building up layer thickness using vapor deposition techniques, which often require multiple depositions. As a result, low film thickness (and correspondingly low loading) results in small capacities on the order of micro-watt hours and a significant hit to the energy densities.

Applications and Future Prospects

Despite these challenges, thin film solid state batteries are more mature and well-aligned with existing semiconductor processing technologies. Their applications include on-board power for integrated circuits, where they offer a more reliable and stable energy source. On the other hand, bulk solid state batteries have the potential to be used Everywhere that lithium-ion batteries are currently used, offering a more robust and efficient energy storage solution.

Exciting Developments and Panel Discussion

The wave of innovation in solid state batteries continues, with my professor chairing a discussion panel at the upcoming Battery Show. This event, scheduled for [date], is an ideal platform to explore the latest advancements and potential applications. If you are interested in learning more about solid state batteries, I highly recommend visiting Michigan (MI) to join this exciting discussion.