Advanced Binders for High Performance Lithium-ion Battery Applications

The selection of polymer binders is highly crucial for the electrode fabrication process, providing mechanical strength while maintaining the electronic and ionic transfer during cycling. The current state of art for binders are mostly based on polyvinylidene fluoride (PVDF) for positive electrodes in toxic organic solvent N-methyl-2-pyrrolidone (NMP). In addition to the hazardous environment, these types of binders are not suggested for high voltage battery applications due to their low adhesiveness, weak mechanical strength, and poor functionality [1]. Especially for generation 3b cathode materials, namely lithium nickel manganese oxide (LiNi0.5Mn1.5O4, LNMO) spinel high voltage cathode or lithium nickel manganese cobalt oxide (NMC) high capacity cathode, building a stable cathode electrolyte interphase (CEI) plays an important role for the overall cell performance and cycle life. In the first formation cycles, active Li is lost due to the side film formation on the anode. To counterbalance the Li loss, an ionic binder in which covalently bonded Li is incorporated with the polymer can be a promising solution. The requirements of high energy density batteries make essential the exploration of advanced polymeric binders, which possess particular functions. For instance, the ionic polymer is blended with the active material which ameliorate the electrochemical polarization of interfacial resistance. There are excellent examples for specifically on lithium iron phosphate (LiFePO4) [2] cathodes whereas, only limited number of studies for LNMO and NMC cathodes [3]. In this work, we aim to synthesis a polymer binder by using a widely known polyacrylic acid (PAA) backbone with covalently bonded Li cations. One of the main advantages of the LiPAA binder is that is soluble in water, thus, this application does not contain volatile organic solvents. Both NMC and LNMO cathodes are processed water-based and contain an active binder. That way we produce environmentally friendly high capacity and voltage cathodes while improving the overall battery performance. References: [1] Zou, F., & Manthiram, A. (2020). A review of the design of advanced binders for high‐performance batteries. Advanced Energy Materials, 10(45), 2002508. [2] Wu, C. Y., & Duh, J. G. (2019). Ionic network for aqueous-polymer binders to enhance the electrochemical performance of Li-Ion batteries. Electrochimica Acta, 294, 22-27. [3] Pieczonka, N. P., Borgel, V., Ziv, B., Leifer, N., Dargel, V., Aurbach, D., ... & Manthiram, A. (2015). Lithium Polyacrylate (LiPAA) as an Advanced Binder and a Passivating Agent for High‐Voltage Li‐Ion Batteries. Advanced Energy Materials, 5(23), 1501008.