Tuesday, 31 May 2016
Exhibit Hall H (San Diego Convention Center)
A soluble polyimide (PI) for lithium-ion battery polymeric binder is newly synthesized by a two-step reaction. Two monomers, bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA) and 4,4-oxydianiline (ODA), are reacted to form polyamic acid through ring opening, and followed by condensation reaction for PI. Although the molecular weight of PI is low around 10,945, the electrode slurry consisting of Si/carbon black/PI (6/2/2 by weight) in N-methyl- 2-pyrrolidone (NMP) shows proper viscosity for coating, and the physical state of cast and dried Si electrode is quite good enough to be adhered the current collector. As a control case, a Si electrode having the conventional polyvinylidene fluoride(PVdF) binder of a molecular weight of 350,000 is also prepared under the same condition, and then both are evaluated with 2032-type coin half cells. Although the initial Coulombic efficiency of PI binder is similar to that of PVdF binder, it delivers much higher discharge capacity (2167 mAh/g vs. 1740 mAh/g). In addition, its cycle life also outperforms than the PVdF binder. This enhancement is closely related to the better adhesion strength of Si electrode with PI binder (0.217 kN/m vs. 0.185 kN/m), which is confirmed by Surface And Interfacial Cutting Analysis System (SAICAS).
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).