Calendar of Events

Speaker: G.G. Amatucci (ESRG, Rutgers University)

Chemical and electrochemical interactions between positive electrode materials and electrolyte solutions and the evolution of the transport properties of subsequent products represent some of the most studied but still least understood lifetime determining phenomena occurring in batteries. This stems from a combination of characterization difficulty, inhomogeneity of products, and the real world deviation from ideal surfaces. The latter presents a further degree of challenge to theoretical modelling of such interactions. Despite the lack of a comprehensive understanding, experimental data from many groups over the past 20 years have consistently shown that the control of the positive electrode surface chemistry and the management of deleterious reactions through the chemistry of the electrolyte have resulted in truly extraordinary stabilization of the electrochemical performance. This talk will explore some of the relevant examples in contrasting electrochemical systems we have explored in our group and collaborators over the past two decades. The intent is to extract some of the common performance defining motifs and address some of the distinct differences observed. Examples from metal fluoride conversion, 4.7V LiNi_0.5Mn_1.5O₄, and especially R?3m layered positive electrodes will be presented. Specific attention will be given to establishing the relative importance of addressing surface reactions vs other failure modes.

Metal fluoride conversion electrodes have been of fundamental interest as high energy density electrodes for lithium batteries for over 40 years, however, the theoretical electrochemical activity of such materials remained elusive as a result of their high bandgap and poor ionic and electronic charge transport characteristics. Over 15 years ago, electronically and mixed conducting matrices to form metal fluoride nanocomposites resulted in the revelation of the theoretical voltages, high energy densities, and minimal reversibility of some of the most promising fluorides and oxyfluorides which operate over 2V. Since this time many in our community have investigated these materials and advanced the state of the related science significantly. This presentation will discuss a sampling of the scientific, technological, and practical advances and also the challenges which remain as supported by examples of research
from the community and our laboratories.