• Energy Research

Lithium-ion batteries are being increasingly used and deployed commercially. Cell-level improvements that address flammability characteristics and thermal runaway are currently being intensively tested and explored. In this study, three additives—namely, lithium oxalate, sodium fumarate and sodium malonate—which exhibit fire-retardant properties are investigated with respect to their incorporation into graphite anodes and their electro/chemical interactions within the anode and the cell material studied. It has been shown that flame-retardant concentrations of up to approximately 20 wt.% within the anode coating do not cause significant capacity degradation but can provide a flame-retardant effect due to their inherent, fire-retardant release of CO2 gas. The flame-retardant-containing layers exhibit good adhesion to the current collector. Their suitability in lithium-ion cells was tested in pouch cells and, when compared to pure graphite anodes, showed almost no deterioration regarding cell capacity when used in moderate (≤20 wt.%) concentrations.

AbstractThe rising demand for high‐performing batteries requires new technological concepts. To facilitate fast charge and discharge, hierarchically structured electrodes offer short diffusion paths in the active material. However, there are still gaps in understanding the influences on the cell performance of such electrodes. Here, we employed a cell model to demonstrate that the morphology of the hierarchically structured electrode determines which electrochemical processes dictate the cell performance. The potentially limiting processes include electronic conductivity within the porous secondary particles, solid diffusion within the primary particles, and ionic transport in the electrolyte surrounding the secondary particles. Mitigating these limits requires an electronic conductivity in the active material of at least 10−4 S m−1 and a primary particle radius below 100 nm. Our insights enable a goal‐oriented tailoring of hierarchically structured electrodes for high‐power applications.

AbstractSodium‐ion batteries are an emerging technology that is still at an early stage of development. The electrode processing for anode and cathode is expected to be similar to lithium‐ion batteries (drop‐in technology), yet a detailed comparison is not published. There are ongoing questions about the influence of the active materials on processing parameters such as slurry viscosity, coating thicknesses, drying times, and behavior during fast drying. Herein, the expected drying time for the same areal capacity of anodes (graphite vs. hard carbon) and cathodes (lithium iron phosphate vs. Prussian blue analogs) are compared based on respective specific capacities reported in the literature. Estimates are made for the materials’ impact on production speed or dryer length. Within the experimental part, water‐based slurries of the same composition are mixed using different active materials according to identical procedure and the viscosity is compared. When drying at a constant drying rate (0.75 g m−2 s−1), lithium iron phosphate electrodes with different areal capacities (1–3 mAh cm−2) are shown to have the highest adhesion. For high drying rates (3 g m−2 s−1) at constant areal capacity, especially the investigated electrodes based on hard carbon show that no binder migration occurs.