Abstract
Water-based inks were formulated using cellulose nanofibers as a binder in order to directly front/reverse print lithium ion cells on a paper separator. Moreover, the high cohesion of electrodes as provided by cellulose nanofibers allowed for the embedding metallic current collectors in the electrodes during the printing stage, in order to develop a one-step printing and assembling process. Positive and negative inks based on LiFePO4, or graphite, respectively, and cellulose nanofibers, displayed rheological properties complying with a variety of printing processes, as well as with screen printing. Printed cells exhibited high electrical conductivity and adhesion between current collectors and inks, i.e., up to 64 ± 1 J/m2. Electrochemical cycling tests at C/10 showed a reversible capacity during the first cycle of about 80 mAh/g, which slightly decayed upon cycling. Preliminary results and assembling strategies can be considered as promising, and they represent a quick solution for the manufacturing of lithium ion batteries. Work is in progress to improve these processing issues and the cycling performances of Li-ion cells.
Highlights
Because of its large availability and excellent mechanical properties, over the last 10 years, cellulose and its derivatives have been widely used for the fabrication of composite materials with widespread applications ranging from structural materials, where fibers are used as reinforcing elements in both synthetic and bio-sourced polymeric matrices [1], to semi-permeable membranes [2,3] and functional substrates/binders for printed electronics [4]
This work demonstrates that cellulose nanofibers can be used as a binder to formulate screenInprsiunmtinmgairnyk,stfhoirs thweofrakbrdiceamtionsotrfahteigshtlhyactohcelsliuvleobseattnearnyoefliebcetrsodceasn, abned uenseadbleasa naewbinbdaettrertyo afossremmublalitnegscdreesingpnrbinatsiendg ionnksthfoeretlheectfraobdreicsaftrionto/frhevigehrslye cporhinetsiinvge boanttaerpyaeplecrtrsoedpeasr,aatonrd, aenadbtlehea new battery assembling design based on the electrodes front/reverse printing on a paper separator, and the integration of current collectors during the printing stage, leading to the fabrication of a fully printed battery in a single unit operation
Results showed how inks exhibit tailored rheological properties for a screen printing process, and how they can be used to integration of current collectors during the printing stage, leading to the fabrication of a fully printed battery in a single unit operation
Summary
Because of its large availability and excellent mechanical properties, over the last 10 years, cellulose and its derivatives have been widely used for the fabrication of composite materials with widespread applications ranging from structural materials, where fibers are used as reinforcing elements in both synthetic and bio-sourced polymeric matrices [1], to semi-permeable membranes [2,3] and functional substrates/binders for printed electronics [4]. Despite the production of thin-flexible, bendable, origami foldable batteries, the assembly of the base electrochemical cell relies on its sequential deposition on a mechanically stable substrate of: (i) a metallic current collector; (ii) the electrode material, a separator/electrolyte. This work shows preliminary promising results for an LIB where positive and negative electrodes are formulated by replacing conventional fluorine based binder (PVdF) with bio-sourced cellulose derivatives as nanocellulose, and carboxymethyl cellulose (CMC) and are screen-printed onto the front/reverse sides of a paper separator. The high electrode cohesion provided by cellulose nanofibers allows for the embedding of metallic current collectors within the electrode material during the printing process, reducing the whole Li-ion cell assembly to a two-stage recto/verso printing sequence
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