Interconnected Multifunctional Waterborne Polyurethane Binder for Structural Robustness of Si Anodes in Lithium-Ion Batteries
Eun Young Lim, J.K. Kim, Eunsol Lee, Taekyun Kwon, Jae Bin Park, Jae-Wang Ko, Kie Yong Cho, Jin Hong Lee
Abstract
Silicon (Si) is garnering attention as a promising anode material for realizing high-energy-density lithium-ion batteries because of its high theoretical capacity (∼3579 mAh g –1 ). Nevertheless, Si undergoes huge volumetric changes during the repeated lithiation/delithiation processes, resulting in the pulverization of Si particles and impaired structural integrity of the electrode, consequently decreasing the electrochemical performance of Si anodes. To address these challenges, we propose a cross-linked MDI-based waterborne polyurethane (TMPU) binder for Si anodes. The TMPU binder has environmental advantages dispersing in water due to the ionic moiety in polymer chains and exhibits excellent mechanical properties and adhesion properties attributed to the network structure. In addition, the oxygen-rich ether group in the PTMG segments of the TMPU binder facilitated Li + transport, resulting in superior specific capacity and cycling performance. Furthermore, the robust TMPU binder provides high structural stability to Si anodes attributed to the formed chemical interaction between TMPU binder and Si particles. This work offers robust strategies for designing environmentally friendly functional binders, advancing the development of high-performance lithium-ion batteries.