New highly conductive solid electrolyte with improved electrode contact for solid-state Li-ion batteries
A joint research team from Ulsan National Institute of Science and Technology (UNIST) and Seoul National University in Korea, with colleagues at Lawrence Berkeley National Lab and Brookhaven National Lab in the US, has developed a new highly conductive (4.1 × 10−4 S cm−1 at 30 °C), highly deformable, and dry-air-stable glass 0.4LiI-0.6Li4SnS4 electrolyte for solid-state Li-ion batteries.
The electrolyte is prepared using a homogeneous methanol solution. The process enables the wetting of any exposed surface of the electrode active materials with the highly conductive solidified electrolyte, resulting in considerable improvements in electrochemical performances. A paper on the work is published in the journal Advanced Materials.
Most efforts on the development of SEs [solid electrolytes] thus far have placed a strong emphasis on the high ionic conductivity of the SEs. However, there is a huge discrepancy between the high ionic conductivities of sulphide SEs and the below-par performance of bulk type ALSBs [all-solid-state lithium batteries], which originates from the limited ionic contact between the active materials and SEs.
For example, cold-pressed composite electrodes have exhibited porosities as high as 20%-30%, reflecting poor surface coverage of SEs on the active materials. Therefore, the fabrication of composite electrodes with more intimate ionic contacts should be a prime objective for future development. However, this development has been inhibited by the drawbacks associated with the conventional protocols of synthesizing sulphide SEs, such as solid-state reactions and mechanochemical methods.—park et al.
The research team’s new solid electrolyte is prepared by adding iodized lithium (LiI) to the compound Li4SnS4 in methanol. The compound’s original ionic conductivity was low, but was enhanced with the addition of LiI. The combination of the two materials delivers a solid electrolyte with high ion conductivity and air stability.
The coating process entails the diffusing of the active material powder in the liquid from melted solid electrolyte and vaporizing the methanol solvent.
|Coating of electrode active materials, with the results of the new process shown at right. Source: UNIST. Click to enlarge.|
A newly developed solid electrolyte has the high ion conductivity and no toxicity problem. In addition, the prices of a raw material and a solvent (methanol) are comparatively low. With this technology, commercialization of solid lithium battery will be available sooner than we thought.—Prof. Yoon Seok Jung (UNIST)
This research was sponsored by Korea’s Ministry of Science, ICT and Future Planning and Ministry of Trade, Industry and Energy.
Park, K. H., Oh, D. Y., Choi, Y. E., Nam, Y. J., Han, L., Kim, J.-Y., Xin, H., Lin, F., Oh, S. M. and Jung, Y. S. (2015) “Solution-Processable Glass LiI-Li4SnS4 Superionic Conductors for All-Solid-State Li-Ion Batteries” Adv. Mater. doi: 10.1002/adma.201505008