Thermoconformable, Flexible Lithium-Ion Batteries

This work introduces a scalable method for fabrication of flexible, thermoconformable lithium-ion batteries, suitable for the interior of vehicles. Electrodes with a composite structure are fabricated by combining conventional granular slurries with a porous carbon nanotube fabric current collector and a solid gel polymer electrolyte. The composite structure reduces polarization at high current densities, for example, with 50% and 17% higher charge capacity at 1C in LTO/Li half cells than control samples and commercial electrodes, respectively. Introducing a gel-polymer electrolyte increases cell durability, safety, and thermal stability. Cyclability test at of 1C shows a capacity retention as high as 91% after almost 400 cycles (average capacity fade of 0.025% cycle(-1)). Full cells operate from 0 to 60 degrees C without any additives. Cells stored for 30 min up to 90 degrees C suffer minor capacity degradation. The possibility to withstand high temperatures and significant flexural deformation enable subjecting these pouch cells to thermoconformable processes. A roof panel with four 25 cm(2) pouch cells is demonstrated. Flammability test shows that the carbon nanotube fibers (CNTF)-LFP/CNTF-LTO cells have a 50% lower peak of heat release rate and a much smaller total heat released than control cells with metallic current collector and liquid electrolyte.