Jeong Beom Lee

Poly(phenanthrenequinone) as a conductive binder for nano-sized silicon negative electrodes

3,6-Poly(phenanthrenequinone) (PPQ) is synthesized and tested as a conductive binder. The PPQ binder, formulated with nano-sized Si powder without conductive carbon, is n-doped by accepting electrons and Li+ ions to become a mixed conductor in the first charging period. The resulting n-doped PPQ binder remains conductive thereafter within the working potential of Si (0.0–0.5 V vs. Li/Li+). Within the composite electrode, the PPQ binder is uniformly dispersed to effectively convey electrons from the current collector to the Si particles. Namely, the PPQ binder by itself plays the roles of conductive carbon and a polymer binder that are loaded in the conventional composite electrodes. Due to the highly conductive nature, the loading of the PPQ binder can be minimized down to 10 wt%, which is close to that used for practical electrode formulation, with reasonable rate and cycle performances of the nano-Si electrode.

Poly(phenanthrenequinone)-Poly(acrylic acid) Composite as a Conductive Polymer Binder for Submicrometer-Sized Silicon Negative Electrodes

In order to improve performances of submicrometer-sized Si negative electrode which shows larger volumetric change than nano-sized Si, composite binders are introduced by blending between poly(phenanthrenequinone) (PPQ) conductive polymer binder and poly(acrylic acid) (PAA) having good adhesion strength due to its carboxyl functional group. Blending between PPQ and PAA shows an effect that the adhesion strength of the Si electrode with the composite conductive binder is greatly improved after blending and this makes its better stable cycle performance. Blending ratios between PPQ and PAA in this work are 2:1, 1:1, 1:2 (by weight) and the best capacity retention at 50th cycle is observed in the electrode with the blending ratio 2:1 (named QA21). This is because that PPQ plays a role of conductive carbon among the Si particles or between Si particles and Cu current collector and PAA binds effectively the particles and the current collector. According to this synergetic effect, the internal resistance of the Si electrode with the blending ratio 2:1 is the smallest value. In addition, the Si electrode with PPQ-PAA composite binder shows the better stable cycle performance than the electrode with conventional super-P conductive carbon (20 wt.%).