Electronic and Ionic Conductivities of LiNi_1/3Mn_1/3Co_1/3O₂-Li₃PS₄Positive Composite Electrodes for All-Solid-State Lithium Batteries

Abstract

Electronic and ionic conductivities of positive composite electrodes composed of LiNi 1/3 Mn 1/3 Co 1/3 O 2 and Li 3 PS 4 were measured by both DC and AC techniques. Two cell configurations of (a) electron-blocking cells and (b) ion-blocking cells were applied for the measurements. The conductivities determined by the DC technique showed a good agreement with those measured by the AC technique, which suggests that both the DC and AC techniques are useful for the measurements of the electronic and ionic conductivities. The electronic conductivities for the composite electrodes at the state of charge (SOC) 0% were lower than the ionic conductivities. The electronic conductivities drastically increased at SOC 50% and became higher than or equal to the ionic conductivities. Cell capacities were evaluated based on the electronic and ionic conductivities. At a high current density of 1.3 mA cm -2 , cell capacities seemed to be associated with the ionic conductivities of the composite electrodes.

Visualizing Local Electrical Properties of Composite Electrodes in Sulfide All-Solid-State Batteries by Scanning Probe Microscopy

“…The resistance of most of the NMC particles decreased to ~10 7 -10 8 Ω, indicating an increase in their electronic conductivity. This behavior corresponded with our previous observations that the electronic conductivity of composite positive electrodes increased by 1-2 orders of magnitude after charging 5 . However, the resistances of three NMC particles, numbered 03, 08, and 10, were 10 9 Ω even after charging.…”

“…At high current densities, it is likely that inhomogeneous electronic conduction degrades battery performance due to current concentration. Increasing the amount of electrode active materials 5 and tailoring their sizes 23,24 can improve the electronic conductivity of carbon-free composite electrodes. However, electrode utilization is limited in the case of no or insu cient quantity of conductive additives.…”

“…To investigate the ionic and electronic conductivity of composite electrodes, Siroma et al designed an AC impedance technique based on the transmission-line model 4 . Our group prepared ion-blocking and electron-blocking cells and used both AC and DC techniques for composite positive electrodes consisting of LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC) positive electrode active materials and Li 3 PS 4 glass SEs of various compositions at 0% and 50% state-of-charge (SOC) 5 . At SOC 0%, the observed ionic conductivity was higher than the electronic conductivity.…”

“…The distribution of local resistance in the composite electrodes was examined by SSRM. We evaluated changes in the local conductivity before and after charging from the results of resistance changes and compared them with previously reported ndings on the variation in electronic conductivity 5 . Current distribution maps and I-V curves of different NMC particles and the SE were obtained via C-AFM.…”

Favorable composite electrodes for all-solid-state batteries

“…For example, electronic conductivity can drastically increase (LiNi 1/3 Co 1/3 Mn 1/3 O 2 ; NCM) after charging. 58) Thus, the investigation of conductivity changes during charging and discharging is important to determine the ideal electrode morphology with effective conducting pathways. The ideal electrode morphology varies according to the properties to be prioritized, i.e., power density, energy density, or cyclability.…”