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Journal of the Electrochemical Society, Vol.162, No.11, D3013-D3018, 2015
Enabling Green Fabrication of Li-Ion Battery. Electrodes by Electrophoretic Deposition: Growth of Thick Binder-Free Mesoporous TiO2-Carbon Anode Films
In this work the potential of employing electrophoretic deposition (EPD) for fabricating Li-ion battery electrodes without using binders and in particular eliminating volatile and toxic organic solvents such as n-methyl 2-pyrrolidone (NMP) is demonstrated. The paper in particular describes the successful application of the EPD method to fabrication of thick (>20 mu m) nano-TiO2/carbon Li-ion intercalation anodes. The EPD system involves deposition of commercial P25 TiO2 nanoparticles and carbon black on aluminum foil from an isopropanol bath without making use of charging agents or other additives. Hetero-coagulation of TiO2 and C particles in the isopropanol medium enabled their 80 V DC cathodic deposition into a well-adhered film with effective intermixing of active and conductive components. Electrochemical testing of the newly binder-free EPD-built electrodes revealed comparable film conductivity, polarization and charge storage capacity properties with the standard binder-based PVDF/NMP electrodes. Most importantly, the charge storage, cycling, and rate properties of the EPD-built electrodes were greatly enhanced by post-EPD sintering of the film at 450 degrees C. The combined EPD-sintering route resulted in a superior conductive percolating network by promoting nanoscale film composition uniformity, inter-particle necking, and favorable porous structure for enhanced interfacing with the liquid electrolyte. The sintered EPD-built electrode exhibited almost 50% higher capacity retention than that of the standard binder-based electrode upon cycling. EPD with its inherent self-assembling functionality and its overall operational simplicity provides an advantageous and green Li-ion electrode fabrication alternative. (C) 2015 The Electrochemical Society. All rights reserved.