Transition metal chlorides NiCl₂, KNiCl₃, Li₆VCl₈ and Li₂MnCl₄ as alternative cathode materials in primary Li thermal batteries

Transition metal chlorides KNiCl₃, Li₆VCl₈ and Li₂MnCl₄ were synthesized by solid state reaction in sealed quartz tubes and investigated as candidate cathode materials along with NiCl₂ in Li thermal batteries. The structure and morphology were studied and electrochemical properties probed at high temperatures (400°C–500°C) against Li₁₃Si₄ by galvanostatic discharge and galvanostatic intermittent titration technique (GITT). All the transition metal chlorides reduced to metal and the products of the discharge mechanism were confirmed by powder X-ray diffraction. NiCl₂ was tested at 500°C and a capacity of 360 mAhg⁻¹ was achieved. KNiCl₃ was tested at different current densities from 15 mA/cm² to 75 mA/cm² and a high voltage profile 2.30V was achieved at 425°C with a capacity of 262 mAhg⁻¹. Li₆VCl₈ was tested at 500°C and a 1.80V voltage plateau at a current density of 7.5 mA/cm² was achieved with a capacity of 145 mAhg⁻¹. Li₂MnCl₄ was tested at the same current density at 400°C and a capacity of 254 mAhg⁻¹ was achieved. These transition metal chlorides exhibit higher voltage against Li₁₃Si₄ and, hence, provide more specific power compared to the well-known metal disulfides MS₂ (M = Fe, Co, Ni) and may be promising cathode materials for Li thermal batteries.