Inkjet-Printed Graphene-Modified Aluminum Current Collector for High-Voltage Lithium-Ion Battery

Abstract

One of the problems plaguing the development of Li-ion batteries that can operate at high cell voltages (i.e., beyond 4.2 V; vs Li/Li+) is the corrosion of the cathode current collector, which causes electrochemical instability and impedance build-up. In this regard, here, we demonstrate the benefits of using inkjet printing technology to uniformly coat the Al current collector (AlCC) with a graphene layer to suppress the corrosion degradation of the current collector at the cathode side. The graphene ink is prepared via solvent exfoliation, and then a thin layer of graphene is coated (∼268 nm in thickness) via inkjet printing on AlCC, which is further annealed in Ar at 350 °C to enhance the electrical conductivity. The thickness and mass loading of the graphene film on Al foil is controlled by the number of printing cycles. The corrosion properties of the bare and printed graphene-coated AlCCs (Gr-AlCC) were evaluated by cyclic voltammetry within 1–5 V (vs Li/Li+) using a Li-ion battery electrolyte. This clearly showed the extensive corrosion degradation of the bare AlCC, which was, however, nearly completely suppressed in the presence of the printed graphene coating. Upon usage of these AlCCs for the galvanostatic cycling of homemade Li-NMC-based cathodes in Li “half” cells, the Gr-AlCC resulted in excellent cyclic stability pertaining to ∼90% capacity retention after 100 cycles (@C/5) despite the usage of 4.5 V as the upper cut-off. By contrast, the bare AlCC resulted in only ∼68% capacity retention under the same conditions. Furthermore, the usage of Gr-AlCC facilitated considerably superior rate capability and lower electrode impedance as compared to the bare AlCC counterpart. This highlights the importance of such passivation/protection of current collectors with conducting coatings and the utility of the scalable-cum-versatile inkjet printing technology for the same.