Bi-Dimensional PTFE Fibrillation Process Implemented in Solvent-Free Manufacturing of Ultra Thick Electrodes for Lithium-Ion Batteries

A method for manufacturing electrodes via a solvent-free dry process can dramatically increase the energy density of lithium-ion batteries (LIBs) without the use of toxic organic solvents. This innovative approach is a strong candidate for advanced battery technologies due to its environmental benefits and cost savings. However, ultra thick electrode required to achieve high energy density significantly intensifies the migration resistance (Rion) and charge transfer resistance (Rct) by longer diffusion length of lithium ions and electrons. The fundamental solution proposed to solve this problem is to increase the conductive additives content to form the enhanced electronic conductivity networks. However, the higher the content of conductive additives in the electrode composition, the more binder is required. If the binder content is insufficient, the increased contact area and excessive agglomeration due to the high specific surface area of the conductive additives will result in reduced interparticle cohesion and uneven packing density. This hinders the formation of a continuous fiber matrix in the PTFE fibrillation process and consequently weakens the mechanical properties of the electrode. In this study, the proposed bi-dimensional PTFE fibrillation process can be effectively utilized to form a uniform and efficient fiber matrix within electrodes, even at high conductive additives content (≥5 wt%) and low binder content (≤1 wt%). This process enables the electrodes to be stored and transported in roll form and preserves the structural integrity of the electrodes during mass production. Moreover, the high and uniform conductivity of the manufactured electrodes prevents significant increases in resistance, even with increased electrode thickness, thus enhancing the electrochemical performance of high energy density LIBs.