Electronic Conductivity of Lithium Solid Electrolytes

Abstract

While significant efforts are being devoted to improving the ionic conductivity of lithium solid electrolytes (SEs), electronic transport, which has an important role in the calendar life, energy density, and cycling stability of solid‐state batteries (SSBs), is rarely studied. Here, the electronic conductivities of three representative SEs, including Li3PS4, Li7La3Zr2O12, and Li3YCl6, are reported. It is reported that the electronic conductivities of SEs are overestimated from the conventional measurements. By revisiting direct current polarizations using two‐blocking‐electrode cells and the Hebb‐Wagner approach, their sources of inaccuracy are provided and the anodic decomposition of SE is highlighted as the key source for the overestimated result. Modifications in the electrode selection and data interpretation are also proposed to approach the intrinsic electronic conductivity of SEs. A two‐step polarization method is also proposed to estimate the electronic conductivity of sulfides that decompose during measurement. Measured by the modified approach, the electronic conductivities of all SEs are one or two orders of magnitude lower than the reported value. Despite that, the electronic conductivity of sulfides seems to be still quite high to enable SSBs with a long calendar life of >10 years, highlighting the critical need for a more careful study of electronic transport in lithium SEs.

Electrochemically and Thermally Stable Inorganics–Rich Solid Electrolyte Interphase for Robust Lithium Metal Batteries

“…[15] However, solid-state electrolytes are usually with low ionic conductivity and poor interface contact, leading to short life span during electrochemical cycles. [16] Strategies to obtain electrochemically and thermally stable SEI are of great importance for the long-life-span and enhanced-safety Li metal batteries. [10d,17] For the electrochemically stable SEI, it must be strong enough to suppress dendrite growth and dense to inhibit the side reactions between the nonaqueous electrolyte and lithium metal.…”

Ultrafast Synthesis of NASICON Solid Electrolytes for Sodium‐Metal Batteries

“…[10][11][12][13][14][15] Among all types of SSEs, inorganic solid oxide electrolytes have been reported with attractive advantages such as high ionic conductivity, low electronic conductivity, high mechanical strength, and high Na + transference number. [16][17][18][19] Among them, NASICON structure SSEs, first discovered by Goodenough and Hong et al in 1976, [20,21] are known for their stability in moist environments, safety, and 3D diffusion pathways, considered ideal sodium ion solid electrolyte materials. [22][23][24] The general formula of NASICON-type SSE is Na 1+x Zr 2 Si x P 3-x O 12 (0 ≤ x ≤ 3).…”

Synthesis, Structure and Physical Properties of the Sodium‐Rich Phosphidogermanate Na8GeP4

“…Lastly, a low electronic conductivity is needed to prevent electronic leakage leading to reduced efficiency of the battery. [4] These attributes can be found in phosphate materials like the NASICON family [5] or in sulfide based materials like Na 3 PS 4 [6] which already achieves an ionic conductivity of up to 0.46 mS/ cm À 1 . Optimization attempts on these materials have led to the finding of compounds like Na 11 Sn 2 PS 12 [7] where the ionic conductivity can reach up to 3.7 mS/cm À 1 .…”