An improved 9 micron thick separator for a 350 Wh/kg lithium metal rechargeable pouch cell

The use of separators that are thinner than conventional separators (> 20 mu m) would improve the energy densities and specific energies of lithium batteries. However, thinner separators increase the risk of internal short circuits from lithium dendrites formed in both lithium-ion and lithium metal batteries. Herein, we grow metal-organic frameworks (MOFs) inside the channels of a polypropylene separator (8 mu m thick) using current-driven electrosynthesis, which aggregates the electrolyte in the MOF channels. Compared to unmodified polypropylene separators, the MOF-modified separator (9 mu m thick) vastly improves the cycling stability and dendrite resistance of cells assembled with Li metal anodes and carbonate-based electrolytes. As a demonstration, a 354 Wh kg(-1) pouch cell with a lithium metal anode and LiNi0.8Co0.15Al0.05O2 (NCA)-based cathode (N/P = 3.96) is assembled with 9 mu m layer of the MOF-modified separator and retains 80% of its capacity after 200 cycles (charged at 75 mA g(-1), discharged at 100 mA g(-1)) at 25 degrees C. Thin separators can improve batteries' energy densities but increase cell shortcircuit risks. Here, the authors report an improved thin metal-organic frameworks separator to improve the dendrite formation resistance and cycling stability of high-voltage lithium battery in carbonate electrolytes.

Automated summary

Thin separators can improve the energy densities of batteries but also increase the risk of short circuits. In this study, an improved thin metal-organic frameworks separator is reported to enhance the resistance to dendrite formation and cycling stability of high-voltage lithium batteries in carbonate electrolytes.