(Invited) Design of Specific Polymer Binders for Stabilization of Si Based Anode in Lib

In recent years, intense efforts have been focused on stabilization of silicon-based anode in Li ion secondary batteries due to their remarkably high theoretical capacity. At the same time, strategy has not yet been established on how to stabilize the silicon based anode sufficiently during long cycles so that it will be feasible for practical use. In this talk, several different approaches on stabilization of silicon-based anode will be introduced both in terms of polymer binders design and active materials design. Our group synthesized several self-healing polymer binder and polymer coating material which are efficient for the use in silicon-based anode. Poly(borosiloxane) (PBS) 1 was prepared by dehydrocoupling polymerization between mesitylborane and diphenylsilanediol in the presence of transition metal catalyst. PBS was found to show self-healing property at 45 o C when coated onto Si electrode. When PBS coated Si electrode was employed for anodic half cell (Si/EC:DEC (1/1=v/v)/Li), it showed much improved durability when compared with PVDF coated Si based cell or bare Si based cell. We also reported a design of BIAN (bis-imino-acenaphthene) based conjugated polymer (P-BIAN) /Poly(acrylic acid) (PAA) composite binder for Si based anode 2,3 . Due to combination of n-type imine-based conjugated polymer (H-bonding acceptor) and PAA (H-bonding donor), synergistic effect in stabilization of Si/C composite anode was observed due to both of desirable electronic structure of P-BIAN and H-bonding based self-healing properties. In this system, anodic half cell delivered specific discharging capacity of above 2000 mAhg -1 for 600 cycles. As alternative approaches, we are also working on preparation of specific Si based anodic active materials which showed extremely high durability. b-SiC/N-doped carbon 4 was found to show excellent durability even in the presence of conventional binder materials due to restricted volumetric changes of b-SiC during lithiation/delithiation. We also report coating of mechanically highly robust silicon oxycarbide on micro silicon 5 , which was also found to be quite effective. References 1) Patnaik, S. G.; Jayakumar, T. P.; Sawamura, Y. Matsumi, N. ACS Appl. Ener. Mater. 2021 , 4, 2241. 2) Gupta, A.; Badam, R.; Matsumi, N. ACS Appl. Ener. Mater. 2022 , 5, 7977. 3) Gupta, A.; Badam, R.; Nag, A.; Kaneko, T.; Matsumi, N. ACS Appl. Ener. Mater. 2021 , 4, 2231 4) Nandan, R.; Takamori, N.; Higashimine, K.; Badam, R.; Matsumi, N. J. Mater. Chem. A. 2022 , 10, 5230. 5) Nandan, R.; Takamori, N.; Higashimine, K.; Badam, R.; Matsumi, N. J. Mater. Chem. A. 2022 , 10, 15960.