Polymer adhesive binders are important components of modern lithium-ion electrodes. Small amounts of polymer binders along with electrode particles and conductive additive particles form a unique polymer composite electrode. The polymer binder ensures mechanical integrity and a stable microstructure of the electrode, and maintains ion and electron pathways within the composite.
Electrode Binder Fundamentals
Proper electrode design is critical to meeting both the energy and power performance requirements for any battery application. Polymer binders used in Li-ion batteries, although not electrochemically active, are essential components in the electrodes, along with acetylene black (AB) conductive additives and the active materials (AM) that store lithium ions.
Conductive Polymer Binders
A functional conductive polymer binder implements the conceptual idea of combining adhesion and conductive additive into one elastic polymer material, solving the volume change problem of high-volume change alloy anode electrodes. A functional conductive polymer binder maintains both electric conductivity and mechanical integrity of the electrode during battery operation. This conductive polymer matrix is also compatible with the lithium-ion slurry manufacturing process.
Figure 1. Conductive polymer with dual functionality, as a conductor and binder, could keep both electric and mechanical integrity of the electrode during the battery cycles.
- Use Si particles
- Fully compatible with conventional lithium-ion technologies
Zhao, H.; Zhou, X.; Park, S. J.; Shi, F. F.; Fu, Y. B.; Ling, M.; Yuca, N.; Battaglia, V.; Liu, G., A polymerized vinylene carbonate anode binder enhances performance of lithium-ion batteries. Journal of Power Sources 2014, 263, 288-295.
We investigated the use of polymerized vinylene carbonate (polyVC) as a binder for graphite anodes in lithium-ion cells. PolyVC has been shown to be a major component of the solid-electrolyte-interphase (SEI) in VC-containing electrolytes. It functions not only as a traditional binder, but also plays an important role in surface stabilization of graphite in propylene carbonate (PC)-based electrolytes. In an electrolyte with PC content as high as 30 wt%, the polyVC binder enhanced battery performance, with a reversible capacity of ~170 mAh/g at a discharge rate of 1C ; whereas a comparable graphite cell fabricated with a PVDF binder failed to cycle.
Aqueous Functional Binders
Water-soluble poly(amic acid)-based binder can withstand high temperature for industrial pre-lithiation process and effectively hold active materials together during repeated charge and discharge cycles. This lithium substituted poly(amic acid) binder (denoted as Li-Pa) can serve as a drop-in replacement for environmentally friendly electrode fabrication in large scale by providing aqueous solubility, exceptional thermal stability and mechanical flexibility.
Zhu, T. Y.; Tran, T. N.; Fang, C.; Liu, D. Y.; Herle, S. P.; Guan, J.; Gopal, G.; Joshi, A.; Cushing, J.; Minor, A. M.; Liu, G., Lithium substituted poly(amic acid) as a water-soluble anode binder for high-temperature pre-lithiation. Journal of Power Sources 2022, 521, 7.
Chen, H.; Ling, M.; Hencz, L.; Ling, H. Y.; Li, G. R.; Lin, Z.; Liu, G.; Zhang, S. Q., Exploring Chemical, Mechanical, and Electrical Functionalities of Binders for Advanced Energy-Storage Devices. Chem. Rev. 2018, 118 (18), 8936-8982.