A Proof-of-Concept Interdigitated 3D Lithium-Ion Battery Cell Architecture Using Patterned Carbon Nanotube Forests

Planar lithium-ion cells with thick electrodes are often subject to an inherent tradeoff between energy and power density due to tortuous lithium-ion diffusion distances through the porous electrodes. Interdigitated 3D cell architectures circumvent this problem by incorporating thick electrode designs while also keeping lithium-ion diffusion distances short, thereby enabling cells with high energy and power densities. However, attempts to fabricate interdigitated cells have been hindered by difficulty in producing conformally coated electrolytes and incorporating the second electrode. Previously, we demonstrated that patterned vertically aligned carbon nanotubes (VA-CNTs) grown directly on Cu foil and coated with Si thin films could serve as a versatile template for high energy density 3D electrodes. Here, we investigate these Si-CNT composites as a template for 3D full cell design. Initiated chemical vapor deposition (iCVD) is used to deposit conformal poly(hydroxyethyl methacrylate-co-ethylene glycol diacrylate) thin film electrolytes onto patterned Si-CNT composites structures. To complete the full cell, a slurry-based cathode is infiltrated into the patterned iCVD coated Si-CNT composite. This cell stack is then soaked in a liquid electrolyte and cycled, making this work the first demonstration of a 3D full cell fabricated using VA-CNTs and an iCVD electrolyte.