Plasma-Modified Cellulose-Based Li-Ion Electrodes for Rechargeable Aqueous Li-Ion Batteries

The composite electrodes of most aqueous electrolyte rechargeable lithium-ion batteries (ARLB) are usually fabricated using noxious fluoritinated binders (PTFE and PVDF) that are dissolved or dispersed in solvents. The use of water-soluble biobased binders reduces the environmental footprint of ARLB, thereby promoting their application. Carboxymethyl cellulose (CMC) is an efficient and environmentally friendly binder that can be used in organic electrolyte lithium batteries. However, the application of this material is limited by its dissolution in an aqueous electrolyte. In a recent study, it was shown that the efficiency of the CMC binder in the ARLB may be enhanced by depositing an organosilicon polymer thin film onto the surface of the electrode using plasma. Herein, in this work, the plasma-modified CMC-based electrode is further characterized, and the mechanism underlying its operation in a dilute aqueous electrolyte is divulged. It is found that the water repellency and porosity of the organosilicon thin film protect the topmost surface of the composite electrode against dissolution in electrolytic solution without compromising the Li+ transport from the electrolyte to the electrode active material. The high electrochemical capacity and stability (over more than 100 cycles) of the cell further indicate that this plasma-deposited layer can withstand the mechanical stress associated with electrochemical cycling.