3D printing PEDOT-CMC-based high areal capacity electrodes for Li-ion batteries

Abstract

Lithium-ion micro-batteries (LIMBs) with higher energy density have drawn extensive attention. 3D printing technique based on direct ink writing (DIW) is a low-cost and simple approach to fabricate LIMBs especially with higher areal capacity. Herein, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) nanofibrils are first combined with carbon methyl cellulose (CMC) to achieve the 3D printing of thick LFP (LiFePO4)-PEDOT-CMC electrodes at room temperature by DIW. 3D-printed PEDOT-CMC-based composite thick electrodes demonstrate high conductivity because of the interconnected 3D network including hierarchical macro-micro porous criss-crossing filaments which can provide effective transport paths for Li ions and electrons. Further, LFP-PEDOT-CMC electrodes of different thicknesses are 3D-printed to study the effect of thicknesses on the electrochemical performances. The 3D-printed ultra-thick LFP-CMC-PEDOT electrode of 1.43 mm thickness at lower rate exhibits a highly improved areal capacity (5.63 mAh cm−2, 0.2 C) and high capacity retention (after 100 cycles, 0.2 C, 92%). The rate capability decreases steadily with the increasing thickness. However, for the extra-thick electrodes greater than 1.43 mm thickness, the discharge capacity, rate, and cycle capability decline dramatically. Electrochemical impedance spectroscopy measurements are used to explain the kinetic mechanism. For 3D-printed LFP-CMC-PEDOT electrodes blow 1.43 mm thickness, the 3D network plays the dominant role to maintain the effective transmission dynamics regardless of electrode thickness. But for the extra-thick electrodes, the greater transport distance becomes the major limiting factor resulting in the degradation of electrochemical performances. This work will offer guidance on how to apply 3D-printed ultra-thick electrodes with high energy density to LIMBs.