Si-based active materials started to be used for small lithium-ion batteries (LIBs) such as 18650 cells with 3.5Ah (INR18650MJ1) in 2015 by LG Chem. However, its relative amount is known to be much smaller than graphitic materials due to the continuous pulverization caused by large volume change during cycling. The gas generation originated from electrolyte decomposition could lead to fast capacity decay of LIB cells. However, regardless of lots of trials such as how to construct nanostructured Si particles and design new adhesive binders, more efficient methods still have to be devised extensively. In this study, we are interested in modifying the surface property of conductive carbon materials, because they have relatively high volume ratio within the electrode and lots of contact points with Si particles. In addition, if there are some crosslinkable moieties upon the conductive carbons, all the Si particles will be well maintained electrochemically active within the electrode.

Based on these strategies, we tried to coat the polydopamine (PD) upon conductive carbons, Super-P, as thin as possible not to impede their electrical conduction. The prepared PD-coated Super-P (PD-SP) was well dispersed even within the aqueous medium. In particular, when polyacrylic acid (PAA) as a polymeric binder is introduced into aqueous anode slurry, the amine group in PD-SP and the hydroxyl group in PAA can react to form the crosslinking bonds. From the adhesion strength measurements by the surface and interfacial cutting analysis system (SAICAS) tool, we could find the increased adhesion properties. As a result, the cycle performance of Si anode was greatly improved to deliver about 1000 mAh/g after 1000 cycles even at 1.2 A/g.

Acknowledges

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) and the Energy Efficiency & Resources Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning(KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20142010102980).