Fast Li-Ion Conduction in Spinel-Structured Solids

Jan L Allen; Bria A Crear; Rishav Choudhury; Michael J Wang; Dat T Tran; Lin Ma; Philip M Piccoli; Jeff Sakamoto; Jeff Wolfenstine

doi:10.3390/molecules26092625

Fast Li-Ion Conduction in Spinel-Structured Solids

Molecules. 2021 Apr 30;26(9):2625. doi: 10.3390/molecules26092625.

Authors

Jan L Allen¹, Bria A Crear², Rishav Choudhury³, Michael J Wang³, Dat T Tran¹, Lin Ma¹, Philip M Piccoli⁴, Jeff Sakamoto³, Jeff Wolfenstine⁵

Affiliations

¹ Energy Sciences Division, Sensors & Electron Devices Directorate, US Army Research Laboratory, Adelphi, MD 20783, USA.
² Department of Chemistry, Howard University, Washington, DC 20059, USA.
³ Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
⁴ Department of Geology, University of Maryland, College Park, MD 20742, USA.
⁵ Solid Ionic Consulting, 9223 Matthews Ave, Seattle, WA 98115, USA.

Abstract

Spinel-structured solids were studied to understand if fast Li⁺ ion conduction can be achieved with Li occupying multiple crystallographic sites of the structure to form a "Li-stuffed" spinel, and if the concept is applicable to prepare a high mixed electronic-ionic conductive, electrochemically active solid solution of the Li⁺ stuffed spinel with spinel-structured Li-ion battery electrodes. This could enable a single-phase fully solid electrode eliminating multi-phase interface incompatibility and impedance commonly observed in multi-phase solid electrolyte-cathode composites. Materials of composition Li_1.25M(III)_0.25TiO₄, M(III) = Cr or Al were prepared through solid-state methods. The room-temperature bulk Li⁺-ion conductivity is 1.63 × 10^-4 S cm^-1 for the composition Li_1.25Cr_0.25Ti_1.5O₄. Addition of Li₃BO₃ (LBO) increases ionic and electronic conductivity reaching a bulk Li⁺ ion conductivity averaging 6.8 × 10^-4 S cm^-1, a total Li-ion conductivity averaging 4.2 × 10^-4 S cm^-1, and electronic conductivity averaging 3.8 × 10^-4 S cm^-1 for the composition Li_1.25Cr_0.25Ti_1.5O₄ with 1 wt. % LBO. An electrochemically active solid solution of Li_1.25Cr_0.25Mn_1.5O₄ and LiNi_0.5Mn_1.5O₄ was prepared. This work proves that Li-stuffed spinels can achieve fast Li-ion conduction and that the concept is potentially useful to enable a single-phase fully solid electrode without interphase impedance.

Keywords: Li-ion battery; cathode-electrolyte interface; fast Li+ ion conductor; solid electrolyte; solid-state battery; spinel.