No abstract

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.

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.

Here we present a perspective on in-situ studies of high temperature batteries. We focus on a primary battery technology-the thermal battery-which possesses a molten salt electrolyte. We discuss aspects of sample environment design, data collection and will briefly look at some case studies. We aim to highlight the importance of using in-situ techniques in studying electrochemical devices such as high temperature batteries.

Recently we have undertaken a preliminary study on the introduction of concept mapping into a physical chemistry module being delivered to non-chemistry specialist students. Previously this module was known for being conceptually challenging and more unpopular amongst biological sciences students than other biological modules of similar difficulty. Here, we discuss the introduction of concept maps at certain points in the module to assist with student’s ability to connect ideas and therefore answer questions they have not previously been able answer reliably. These are combined with additional large group workshops and in-lecture examples to help the students to connect the questions with the course content. Also included are the experiences of the staff delivering the module before and after this introduction and some qualitative feedback from the students involved. This study has since lead to a change in the way introductory physical chemistry is taught to non-chemistry students at Surrey and has informed teaching methods for subsequent years.