Partial electronic conductivity of nanocrystalline Na₂O₂

Abstract

was prepared from the coarse-grained material (97%, Sigma Aldrich, No. 223417) using a high-energy planetary mill (Fritsch Pulverisette 7 (premium line)) operated at a rotation speed of 500 rpm.

The Electronic Conductivity of Single Crystalline Ga‐Stabilized Cubic Li7La3Zr2O12: A Technologically Relevant Parameter for All‐Solid‐State Batteries

“…[ 35 ] Hence, also by considering results in literature presented so far, it is very likely that electron transport is not coupled with ion transport, as it may happen in some other materials with poor ion conducting properties. [ 36 ] The low activation energy associated with electronic conductivity is very likely the key reason for this decoupling. Having a low activation energy, the electron mobility is significantly less influenced by the temperature than the ionic mobility.…”

In Situ Electrochemical Study of Na–O2/CO2 Batteries in an Environmental Transmission Electron Microscope

“…In both R-4 and R-7, the diffusion rate of Na + is the critical factor to affect the decomposition of the discharge products. It is reported that Na 2 CO 3 possesses much higher Na + ionic conductivity (∼10 −12 S cm −1 ) 50,51 than Na 2 O 2 (∼10 −13 S cm −1 ), 52 which may offer faster kinetics for the decomposition of Na transformation advanced from the surface toward the core until complete decomposition (Figure 1c,e,g), while the latter remained its crystalline state almost unchanged (Figure 7b). The small grain size and poor crystallinity might be another probable reason for the complete decomposition of Na 2 CO 3 in the Na−O 2 /CO 2 −CNT nanobattery during the charging process.…”

“…In both R- and R-, the diffusion rate of Na + is the critical factor to affect the decomposition of the discharge products. It is reported that Na 2 CO 3 possesses much higher Na + ionic conductivity (∼10 –12 S cm –1 ) , than Na 2 O 2 (∼10 –13 S cm –1 ), which may offer faster kinetics for the decomposition of Na 2 CO 3 than Na 2 O 2 in the in situ experiments. In addition, the main charge products of the Na–O 2 /CO 2 –CNT battery and the Na–O 2 –CNT battery were Na 2 CO 3 and Na 2 O 2 , respectively, and the morphology and crystallinity of which are obviously different.…”

“…When analyzing the Na substrate, we found that the surface of the Na substrate in an O 2 atmosphere was composed of Na 2 O and Na 2 O 2 , while that in a CO 2 /O 2 atmosphere was composed of Na 2 O 2 and Na 2 CO 3 , which were essentially the solid electrolyte in our experiments (Figure S1). The ionic conductivity of Na + in Na 2 O and Na 2 O 2 is lower than that in Na 2 O 2 and Na 2 CO 3 , − so some Na + might experience difficulty in diffusing from the surface of the Na 2 O and Na 2 O 2 layer to the bulk Na during charge, which was then electroplated as Na nanoparticles at the surface of the Na substrate. This explains why the discharge products in the Na–O 2 –CNT battery collapsed to several nanoparticles.…”

Structure Evolution of Na2O2 from Room Temperature to 500 °C

“…Araujo et al also used DFT to investigate charge migration in α-Na 2 O 2 and found that the conductivity is dominated by the diffusion of hole polarons. These results are consistent with the experimental studies of Dunst et al and Philipp et al who independently investigated the temperature-dependent conductivity of α-Na 2 O 2 . Dunst et al observed an electronic conductivity around 10 –14 S/cm at room temperature and an activation energy from 193 to 373 K of ∼1.06 eV.…”