Impact of Graphite Materials on the Lifetime of NMC811/Graphite Pouch Cells: Part II. Long-Term Cycling, Stack Pressure Growth, Isothermal Microcalorimetry, and Lifetime Projection

Part II of this 2-part series examines the impact competitive graphite materials on NMC811 pouch cell performance using Ultra-High Precision Coulometry (UHPC), isothermal microcalorimetry, and in-situ stack growth. A simple lifetime projection best NMC811/graphite cells as a function operating temperature is made. We show that choice greatly impacts fractional fade, while charge endpoint capacity slippage was largely unchanged due to identical cathodes. an increase in 1st cycle efficiency limited redox-active sites—favourable for minimizing Li inventory loss—is concomitant with negative electrode transfer resistance. Further, we demonstrate artificial graphites (AG) have lower parasitic heat flow (∼0.060 mW −1 h at 40 o C) compared natural (NG), AGs had minimal thickness change cycling. Finally, model SEI growth 4.06 V square-root time model, project here can decades-long lifetimes 20 –30 °C when plating avoided. Such are excellent candidates grid storage applications where energy density less important long lifetime.