Configuration entropy effect on temperature coefficient of redox potential of P2-Na _x CoO₂

Abstract

The temperature coefficient (α) of redox potential (V) is a significant material parameter that coverts thermal energy into electric energy. In this paper, we determined α of P 2-type Na x CoO 2 against the Na + concentration (x). The solid component (α solid) of α scatters from −0.18 mV/K to 0.64 mV/K. The phase separation (PS) model cannot reproduce the x-dependence even qualitatively. We interpreted the unexpected disagreement in terms of the residual configuration entropy in the pseudo-disordered region between the Na + ordered phases.

Energy harvesting thermocell with use of phase transition

“…For example, the NMF83/NCF90 cell (α cathode −α anode = 1.7 mV/K) 6 shows a thermal voltage of V cell ~ 40 mV between T L (=286 K) and T H (=313 K). So far, α of wide range of battery materials were reported; α = −0.3-1.4 mV/K in Prussian blue analogues 8 , α = 0.2-1.1 mV/K in several conjugated polymers 9 , α = 0.0−0.9 mV/K in Na x CoO 2 10 and α = 0.9 mV/K in Li x FePO 4…”

Temperature switch of electrochemical Seebeck coefficient of Fe2+/Fe3+via formation of [FeCl4]2−/[FeCl4]−

“…The thermal potential ( V T ) at temperature difference (Δ T = T H − T L ; T H and T L are the temperatures of hot and cold electrodes, respectively) was evaluated with use of a specially-designed thermocell. 16 The electrolyte was filled in a 0.73 mm ϕ polytetrafluoroethylene (PTFE) cylinder. Both ends were sealed with Pt disks with an area of 0.42 cm 2 .…”

Concentration gradient effect in liquid thermoelectric device composed of organic-solvent-added aqueous solution containing K4[Fe(CN)6]/K3[Fe(CN)6]

“…The measurements were performed in a specially designed thermocell. 30) The electrolyte was filled in a 0.73 mmf polytetrafluoroethylen (PTFE) cylinder. Both ends were sealed with the Pt disks on the Al pedestals.…”