Reversible (bi-functional) ORR/OER electrocatalysts identified with the creation of mixed valent Mn perovskites and the Mn3+/Mn4+ surface redox couple.

NiS2 is a cathode material found in primary batteries which operate at high temperature. Herein we report the in situ battery discharge study of a thermal battery cell which uses NiS2 as a cathode, using simultaneous collection of powder neutron diffraction data and electrochemical data. Five different regions were observed upon battery discharge and the evolution of nickel sulfide phases has been studied. Four different nickel‐containing phases are observed during discharge (NiS2, NiS, Ni3S2 and Ni). A new discharge mechanism has been proposed which does not include Ni7S6. Multiphase quantitative Rietveld refinement has allowed the percentages of the phases to be monitored during discharge. High intensity synchrotron powder X‐ray diffraction has been used to study the resulting phases present in the cathode after battery discharge.

In this work ZrS3 has been synthesized by solid state reaction in a sealed quartz tube and investigated as a candidate cathode material in Li thermal batteries. The structure of ZrS3 before and after cell testing has been studied using powder X-ray diffraction. A new spinel related material, LiZr2S4, has been identified as the product of the electrochemical process, which can be indexed to a = 10.452(8) Å cubic unit cell. The electrochemical properties of the batteries were investigated at 500°C against Li13Si4 by galvanostatic discharge and galvanostatic intermittent titration technique (GITT). In a thermal Li cell at 500°C a single voltage plateau of 1.70 V at a current density of 11 mA/cm2 was achieved with capacity of 357 mA h g−1. Therefore ZrS3 material has some promise as a cathode for Li thermal batteries.

Thermal batteries are an established primary battery technology and the most commonly used cathodes in these batteries are transition metal disulfides MS 2 (where M = Co, Ni and Fe). However, understanding the evolution of crystalline phases upon battery discharge has been hindered due to the high temperature operation of these batteries. Here we report an experiment that simultaneously collects powder neutron diffraction and electrochemical data as the battery is discharged. Four regions are observed in the diffraction data and four different cobalt containing phases are observed. Multi-phase Rietveld refinement has been used to monitor the evolution of phases during discharge and this is linked to the battery discharge profile. A new discharge mechanism has been proposed which involves hexagonal CoS instead of Co 3 S 4 , and the increase in unit cell parameters on discharge suggests the formation of a sulfur deficient solid solution before transformation to Co 9 S 8. This behavior seems reminiscent of that of NiS 2 suggesting that the discharge mechanisms of transition metal disulfides may have more similarities than originally thought.

In this work CoNi 2 S 4 was investigated as a candidate cathode material for Li thermal batteries. The CoNi 2 S 4 was synthesized by a solid state reaction at 550 • C in a sealed quartz tube. Neutron powder diffraction was utilized to confirm normal spinel structure up to 200 • C, however, there was cation disorder above this temperature. The electrochemical properties of the batteries were investigated at 500 • C by galvanostatic discharge to elucidate the mechanism and the products NiS, Co 3 S 4 and Co 9 S 8 of the discharge mechanism were confirmed using powder X-ray diffraction. CoNi 2 S 4 exhibits two voltage plateaus vs Li 13 Si 4 at 500 • C, one at 1.75 V and the second at 1.50 V. CoNi 2 S 4 has an overall capacity of 318 mA h g −1 from OCV 2.58 V to 1.25 V vs Li 13 Si 4 which is comparable to that of the well-known metal disulfides. Today the human society and technology progress in electric vehicles, medical equipments, military applications and space technology require power systems with high energy, safety and long shelf -life characteristics. There are different kind of power systems such as supercapacitors, fuel cells and thermal batteries for this goal. Thermal batteries are electrochemical devices that offer a direct conversion of chemical energy to electrical energy by an electrochemical oxidationreduction reaction at high temperature (>300• C) utilizing a molten salt electrolyte. Thermal batteries are primary batteries which find use in a number of applications as they are known for their long shelf life and ability to be discharged at particularly high rates when compared to other types of batteries.1 A key component of thermal batteries is the halide salt electrolyte that is a solid at ambient temperatures which gives the cells their long life but melts in the 300-500• C region. 2 This solid -liquid phase transition leads to the electrolyte becoming ionically conductive and allowing the ions to transfer between the anode and the cathode. Thermal batteries typically use a lithium alloy as the anode, a halide salt eutectic as the electrolyte, an insulating porous material as the separator and a transition metal sulfide as the cathode. The Li 13 Si 4 alloy is often used as the anode as the lithium diffusion in silicon (10 −8 cm −2 s −1 ) is greater than in other alloys 3 and has moisture stability as well as it staying solid at the operating temperature. The discharge reaction of Li 13 Si 4 to Li 7 Si 3 at a potential of 0.157 V against Li metal at 415• C corresponds to a capacity of 485 mA h g −1 .4The electrolyte that has been used in this work is the lithium chloride -potassium chloride eutectic which has a melting point of around 354• C and requires a minimum of 35 wt% MgO as a separator. 5 The most common transition metal disulfides to be used as cathodes are FeS 2 , NiS 2 or CoS 2 and all of these materials exhibit a potential of ∼ 1.70 V vs Li 13 Si 4 at the beginning of their discharge but also have further electrochemical transitions to complete the reduction to the transition metal. 6 T...