Data for an Advanced Microstructural and Electrochemical Datasheet on 18650 Li-ion Batteries with Nickel-Rich NMC811 Cathodes and Graphite-Silicon Anodes

Mapping internal temperatures during high-rate battery applications

Electric vehicles demand high charge and discharge rates creating potentially dangerous temperature rises. Lithium-ion cells are sealed during their manufacture, making internal temperatures challenging to probe1. Tracking current collector expansion using X-ray diffraction (XRD) permits non-destructive internal temperature measurements2; however, cylindrical cells are known to experience complex internal strain3,4. Here, we characterize the state of charge, mechanical strain and temperature within lithium-ion 18650 cells operated at high rates (above 3C) by means of two advanced synchrotron XRD methods: first, as entire cross-sectional temperature maps during open-circuit cooling and second, single-point temperatures during charge-discharge cycling. We observed that a 20-minute discharge on an energy-optimized cell (3.5 Ah) resulted in internal temperatures above 70 °C, whereas a faster 12-minute discharge on a power-optimized cell (1.5 Ah) resulted in substantially lower temperatures (below 50 °C). However, when comparing the two cells under the same electrical current, the peak temperatures were similar, for example, a 6 A discharge resulted in 40 °C peak temperatures for both cell types. We observe that the operando temperature rise is due to heat accumulation, strongly influenced by the charging protocol, for example, constant current and/or constant voltage; mechanisms that worsen with cycling because degradation increases the cell resistance. Design mitigations for temperature-related battery issues should now be explored using this new methodology to provide opportunities for improved thermal management during high-rate electric vehicle applications.

Process ‐ Structure ‐ Formulation Interactions for enhanced Sodium Ion Battery Development ‐ a Review

Before the viability of a cell formulation can be assessed for implementation in commercial sodium ion batteries, processes applied in cell production should be validated and optimized. This review summarizes the steps performed in constructing sodium ion (Na‐ion) cells at research scale, highlighting parameters and techniques that are likely to impact measured cycling performance. Consistent process‐structure‐performance links have been established for typical lithium‐ion (Li‐ion) cells, which can guide hypotheses to test in Na‐ion cells. Liquid electrolyte viscosity, sequence of mixing electrode slurries, rate of drying electrodes and cycling characteristics of formation were found critical to the reported capacity of laboratory cells. Based on the observed importance of processing to battery performance outcomes, the current focus on novel materials in Na‐ion research should be balanced with deeper investigation into mechanistic changes of cell components during and after production, to better inform future designs of these promising batteries.