Improved electrochemical performance of Li-ion pouch cells with boron nitride nanotube-coated separators

The performance of the Li-ion pouch cells can be greatly enhanced by using boron nitride nanotubes (BNNT) coated on the polyethylene (PE) separators. BNNT coated on the PE separators (BNNT-PE) apparently boost the ionic conductivity (IC) as high as ∼40.7 % at various temperature ranges (−10 °C–60 °C) as compared to Neat-PE due to faster Li-ion transport and wettability offered by BNNT coating on PE. As a result, Li-ion transport can be enhanced at the interface as well as on the entire surface of the separator. For the NCM523//graphite pouch cells designed with the reversible capacity of 464.0 mAh, at 10.0 C, Neat-PE shows capacity of only 27.1 mAh, while BNNT-PE shows 4.3 times higher capacity of 143.2 mAh at room temperature. As a result, the BNNT-PE pouch cells present superior C-rate performance and cycle retention at both room and the low temperature (−10 °C). In addition, the excellent thermal conductivity of BNNT and higher IC of the BNNT-PE can effectively reduce the surface temperature of a single pouch cell about 3–4% during cycling. Upon these properties, BNNT may provide explicit solutions, in a material aspect, for fast charging-discharging, and enhanced safety with fast heat dissipation for advanced LIBs.