High performance screen printable lithium-ion battery cathode ink based on C-LiFePO4

Abstract

Lithium-ion battery cathodes have been fabricated by screen-printing through the development of C-LiFePO4 inks. It is shown that shear thinning polymer solutions in N-methyl-2-pyrrolidone (NMP) with Newtonian viscosity above 0.4Pas are the best binders for formulating a cathode paste with satisfactory film forming properties. The paste shows an elasticity of the order of 500Pa and, after shear yielding, shows an apparent viscosity of the order of 3Pas for shear rates corresponding to those used during screen-printing. The screen-printed cathode produced with a thickness of 26μm shows a homogeneous distribution of the active material, conductive additive and polymer binder. The total resistance and diffusion coefficient of the cathode are ∼450Ω and 2.5×10−16cm2s−1, respectively.The developed cathodes show an initial discharge capacity of 48.2mAhg−1at 5C and a discharge value of 39.8mAhg−1 after 50 cycles. The capacity retention of 83% represents 23% of the theoretical value (charge and/or discharge process in twenty minutes), demonstrating the good performance of the battery. Thus, the developed C-LiFePO4 based inks allow to fabricate screen-printed cathodes suitable for printed lithium-ion batteries.