Search for: All records

Chemical redox reactions between redox shuttles and lithium-ion battery particles have applications in electrochemical systems including redox-mediated flow batteries, photo-assisted lithium-ion batteries, and lithium-ion battery overcharge protection. These previous studies, combined with interest in chemical redox of battery materials in general, has resulted in previous reports of the chemical oxidation and/or reduction of solid lithium-ion materials. However, in many of these reports, a single redox shuttle is the focus and/or the experimental conditions are relatively limited. Herein, a study of chemical redox for a series of redox shuttles reacted with a lithium-ion battery cathode material will be reported. Both oxidation and reduction of the solid material with redox shuttles as a function of time will be probed using ferrocene derivatives with different half-wave potentials. The progression of the chemical redox was tracked by using electrochemical analysis of the redox shuttles in a custom electrochemical cell, and rate constants for chemical redox were extracted from using two different models. This study provides evidence that redox shuttle-particle interactions play a role in the overall reaction rate, and more broadly support that this experimental method dependent on electrochemical analysis can be applied for comparison of redox shuttles reacting with solid electroactive materials.

 

In efforts to increase the energy density of lithium-ion batteries, researchers have attempted to both increase the thickness of battery electrodes and increase the relative fractions of active material. One system that has both of these attributes are sintered thick electrodes comprised of only active material. Such electrodes have high areal capacities, however, detailed understanding is needed of their transport properties, both electronic and ionic, to better quantify their limitations to cycling at higher current densities. In this report, efforts to improve models of the electrochemical cycling of sintered electrodes are described, in particular incorporation of matrix electronic conductivity which is dependent on the extent of lithiation of the active material and accounting for initial gradients in lithiation of active material in the electrode that develop as a consequence of transport limitations during charging cycles. Adding in these additional considerations to a model of sintered electrode discharge resulted in improved matching of experimental cell measurements.

 

Recently publications have suggested best practices with regards to techniques and reporting for battery research. One area gaining attention is the need for battery cell replicates. In this perspective, the need for replicates is put into the context of the uncertainty in gravimetric capacity resulting from a component typically assumed as a constant—the current collector mass. The expected variation in reported gravimetric capacity just due to this factor for representative current collectors and battery materials will be discussed, and the additional importance of electrode loading to minimize the impact of this factor will be described.

 

Interest in developing high performance lithium-ion rechargeable batteries has motivated research in precise control over the composition, phase, and morphology during materials synthesis of battery active material particles for decades. Coprecipitation, as one of the most reported methods in the literature to produce precursors for lithium-ion battery active materials, has drawn attention due to its simplicity, scalability, homogeneous mixing at the atomic scale, and tunability over particle morphology. This highlight summarizes the advancements that have been made in producing crystalline particles of tunable and complex morphologies via coprecipitation for use as lithium-ion battery precursor materials. Comparison among different crystallization reagents, solution conditions that influence the properties of crystal particles, and the fundamental knowledge from equilibrium and/or kinetic study of the coprecipitation processes, are systematically discussed. The research reports and guiding principles summarized in this highlight are meant to improve selections made by researchers to efficiently determine synthesis conditions. In addition, it is desired that the methods applied from the study of crystallization will inspire researchers to pursue further investigation of the nucleation and growth mechanisms of these coprecipitation processes, which will be necessary to achieve truly predictive particle synthesis.