New highly conductive solid electrolyte with improved electrode contact for solid-state Li-ion batteries
31 December 2015
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.
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| 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.
Resources
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
Could be an important step towards next generation lower cost solid state lithium batteries?
What would be the potential energy and power density performance?
Posted by: HarveyD | 31 December 2015 at 08:13 AM
A 1 μm thick coating would have a conductivity of 4.1 S/cm² at 30°C... but I can't find a definition of "S", or even its units.
Posted by: Engineer-Poet | 31 December 2015 at 04:29 PM
E-P,
The 'S' is for siemens and it tells you what kind of power rating the cell will have. It's not a very useful measurement because it's like giving mA/h without the Voltage when talking about storage capacity.
Posted by: DaveD | 31 December 2015 at 05:29 PM
S is used for Siemens, a measurement of conductance which the reciprocal of resistance. Therefore, 1 Siemen equals 1 Ohm or 1000 Siemens equals 0.001 Ohms.
Posted by: sd | 31 December 2015 at 05:37 PM
@EP, it is not cm sq.
24390ohm/mm or 24.39ohm/um. Not sure of other materials in these applications, but compared to industrial conductors and insulators, this is much closer to a poor insulator.
Beyond text book properites, creating lower contact resistance, seems to advance the art in practice.
Posted by: Tim Duncan | 04 January 2016 at 08:17 AM
Conductance is mhos, inverse ohms. Renaming it is confusing and ridiculous.
@Tim Duncan, if you divide 4.1e-4 mho/cm¹ by 1e-4 cm you get 4.1 mho/cm². Achieving anything like a reasonable internal resistance for a cell requires a hell of a lot of interface area.
Posted by: Engineer-Poet | 04 January 2016 at 11:04 PM