High performance screen-printed electrodes prepared by a green solvent approach for lithium-ion batteries

Abstract

New inks based on lithium iron phosphate and graphite for cathode and anode, respectively, were developed for printable lithium-ion batteries using the “green solvent” N,N′-dimethylpropyleneurea (DMPU) and poly(vinylidene fluoride), PVDF, as a binder. The results were compared with the ones from inks developed with the conventionally used solvent N-methyl-2-pyrrolidone, NMP.

The rheological properties of the PVDF/DMPU binder solution shows a more pronounced shear thinning behavior than the PVDF/NMP solution. Cathode inks prepared with 2.25 mL and 2.50 mL of DMPU for 1 g of electrode mass show an apparent viscosity of 3 Pa s and 2 Pa s for a shear rate of 100 s−1, respectively, being therefore processable by screen-printing or doctor blade techniques. The electrodes prepared with DMPU and processed by screen-printing show a capacity of 52 mAh g−1 at 2C for the cathode and 349 mAh g−1 at C/5 for the anode, after 45 charge-discharge cycles. The electrochemical performance of both electrodes was evaluated in a full-cell and after 9 cycles, the discharge capacity value is 81 mAh g−1, showing a discharge capacity retention of 64%. The new inks presented in this work are thus suitable for the development of printed batteries and represent a step forward towards more environmental friendly processes.