Thermo-transport properties of Zn-substituted layered Li-nickel oxide, $\hbox {LiNiO}_{2}$

Abstract

The layered Li-TM-$\hbox {O}_{2}$ materials have been investigated extensively due to their application as cathodes in Li batteries. The electrical properties of these oxides can be tuned or controlled either by non-stoichiometry or substitution. Hence the thermo-transport properties of Zn-substituted $\hbox {LiNi}_{1-x}\hbox {Zn}_{x}\hbox {O}_{2}$ for $0 \le x \le 0.16$ have been investigated in the temperature range of 300–900 K for potential application as a high-temperature thermoelectric material. For $x < 0.08$, the compounds were of single phase belonging to the space group R-3mH while for $x > 0.08$ an additional minority phase, ZnO forms together with the main layered phase. All the compounds exhibit a semiconducting behaviour with electrical resistivity, varying in the range of  $\sim 10^{-4}$ to $10^{-2}\,\,\Omega \hbox {m}$ between 300 and 900 K. The electrical resistivity is found to increase with increasing Zn-substitution predominantly due to a decrease in the charge carrier hole mobility. The activation energy remains constant, $\sim$10  meV, with Zn-substitution. The Seebeck coefficient of the compounds is found to decrease with increasing temperature and increase with increasing Zn-substitution. The Seebeck coefficient decreases from $\sim$95 to $35\ \upmu \hbox {V K}^{-1}$ and the corresponding power factor is $\sim$12$\ \upmu \hbox {W m}^{-1}\ {\hbox {K}}^{-2}$ for the $x = 0.16$ compound.