Decoding Lithium-ion Conductivity In Solids | Chemical & Engineering News
Volume 93 Issue 28 | p. 24 | Concentrates
Issue Date: July 13, 2015

Decoding Lithium-ion Conductivity In Solids

Electrochemistry: Understanding ion diffusion in mixed lithium phases may lead to solid electrolytes and safer batteries
Department: Science & Technology
News Channels: Analytical SCENE, Materials SCENE
Keywords: lithium-ion battery, solid state battery, solid electrolyte, battery safety

Rechargeable lithium-ion batteries power nearly all of today’s electricity-hungry portable gadgets and tools. Although they boast extreme reliability, the cells’ flammable liquid organic electrolyte solution poses a minute but potentially serious hazard. Nonflammable solid electrolytes would be ideal substitutes for the liquids. But suitable replacements have remained elusive because most solids are weak Li-ion conductors. Mixtures of Li4SiO4 and Li3PO4 are the exception. Compared with the pure components, some mixed compositions exhibit a jump of three orders of magnitude in ionic conductivity. But until now, the phases and their compositions have not been examined in detail, and the conductivity mechanism has not been understood. So a team led by materials chemist M. Saiful Islam of England’s University of Bath applied NMR, electrochemistry, and computational techniques to address those issues, a key step toward making new types of batteries (J. Am. Chem. Soc. DOI: 10.1021/jacs.5b04444). The team found that mixed lithium phases with silicate-to-phosphate ratios of 0.25:0.75 and 0.5:0.5 are among the top solid Li-ion conductors. They also found that Li-ion diffusion proceeds via a concerted hopping motion of interstitial and lattice Li ions through three-dimensional networks, suggesting that increasing lithium disorder may further increase ion conductivity.

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