Polydopamine-Coated Current Collector: Improving the Electrochemical Performance of Si Anode By Raising the Interfacial Adhesion Strength

Abstract

The high theoretical capacity of Si has made it a promising candidate for high energy density and large-scale lithium ion battery (LIB) anode. However, this system exhibits rapid capacity decay and hence poor cycling performance due to huge volume expansion of about 300% when Li-ion inserts into the Si particle during charging. Experimental observations suggest the formation of cracks at the early stages of cycling due to this volume expansion. The continuous mechanical stressing and fracturing of Si particles lead to the pulverization of the electrode and formation of dead Si particles. In particular, dead particles detached from current collector can mainly occur decay of electrochemical performance of lithium ion batteries.[1,2] Hence, we tried to improve the interfacial adhesion between the Si electrode layer and the current collector by making a hydrophilic layer on the current collector through polydopamine coating and induce cross-linking of polydopamine (PD) and polyacrylic acid (PAA) binder. The contact angle and the interfacial adhesion between the electrode and the PD coated and bare current collector were analyzed using Phoenix 300 Touch and the Surface And Interfacial Cutting Analysis System(SAICAS), respectively. From the SAICAS analysis, the adhesion strength between PD-coated current collector and Si electrode layer was improved comparing to the bare system. (Bare current collector: 0.2455 kN m-1 and PD-coated current collector: 0.3532kN m-1). The PD-coated current collector showed a higher hydrophilicity to the electrolyte than the bare current collector. The cycle performance of the cell was greatly enhanced by the PD coating on the anode current collector. The present studies suggest that, the coating of PD and induced cross-linking of PD and PAA improves the electrochemical performance of the Si anode. Acknowledgement This work was supported by the Human Resource Training Program for Regional Innovation and Creativity through the Ministry of Education and National Research Foundation of Korea(NRF-2014H1C1A1066977)