We design new architectures for energy storage devices with enhanced energy density while maintaining long service life.The cycle and calendar life of energy storage systems is often governed by the stability window of the electrolyte. The drive of high cell voltage (which translates to high specific energy) leads to the use of redox couples outside the stability window. However, side reactions on electrode surfaces coupled with volume changes of electrode materials result in capacity loss. Further, undesirable chemical communications between the two electrodes lead to additional side reactions. A solid electrolyte can stop such communication by allowing only the working ions to pass through.

We have been developing multiple approaches to realize the effect of a single ion conductor.

1. Supported pseudo-ion conductor

In the first approach, we employ a thin film metal oxide mixed-ion conductor on a porous polymer support to serve effectively as a solid-state ion conductor. Using mixed-ion conductor as a supported electrolyte greatly expands the materials choices for solid electrolyte layers. We have used this approach to enable long-life lithium-sulfur batteries by stopping soluble polysulfides from crossing over to the negative electrode. We are exploring a broad range of architectures that can enable the next generation cell chemistries.

Lithiated vanadium oxide, a mixed ion and electron conductor, coated on a porous separator serves effectively as a solid-state ion conductor and greatly enhances cycling stability of Li-S batteries.

V2O5 polysulfide anion barrier for long-lived Li–S batteries, W. Li, J. Hicks-Garner, J. Wang, J. Liu, A. F. Gross, E. Sherman, J. Graetz, J. J. Vajo, and P. Liu, Chemistry of Materials, (2014), 26, 3403–3410

2. Solution processed solid electrolytes

In a second approach, we have developed sulfide solid electrolyte coatings from solutions precursors. These coatings form directly on lithium metal surface without the need for high temperature sintering. Such processes naturally lend them selves to efficient integration of all solid state batteries.

A Li2S3/P2S5 solution is used to coating a solid state electrolyte layer Li3PS4 directly on lithium metal.

Solid Electrolyte Layers by Solution Deposition, H.-D. Lim, H.-K. Lim, X. Xing, B.-S. Lee, H. Liu, C. Coaty, H. Kim, P. Liu, Advanced Materials Interfaces, (2018), DOI: 10.1002/admi.201701328.