Compatibilities of Conducting Polymer-Based Electrode Matrices for Lithium-Ion Batteries

Abstract

Aqueous electrode processing has been considered an important movement to make the overall battery fabrication process less toxic and more environmental-friendly1. The traditional approach focuses on mixing common aqueous binders such as carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and styrene-butadiene rubber (SBR) with carbon additives to form conductive, water-processable electrode matrices2. This design, however, is unlikely to improve electrode interconnection, where carbon additives still loosely adhere to active materials3. Utilizing a better electrode matrix is believed to enhance both mechanical and electrical connections of electrode architecture, thus improving battery capacity and stability. Our recent work has demonstrated the design concept of conducting polymer composites as self-conductive and water-processable electrode matrices for Li-ion batteries4. By using in situ chemical polymerization method, polypyrrole:carboxymethyl-cellulose (PPy:CMC) composites, as a representative, were synthesized facilely and at low cost. The molecular structure of PPy:CMC composites composes of carboxyl groups from CMC as main anionic dopants for the positively charged PPy polymer chain. Their unique adhesion enables PPy:CMC composites to sufficiently connect active materials electrically and mechanically despite their low intrinsic electrical conductivity. As a result, cathodes with PPy:CMC composites and LiCoO2 or LiNi1/3Mn1/3Co1/3O2 showed promising cycling performance even at a 1-C rate, which is rarely reported for carbon-additive-free electrodes. Also, aqueous electrode casting is feasible for PPy:CMC-based electrodes, thus addressing toxicity and intensive-energy consumption associated with the current NMP-based electrode processing. Furthermore, their compatibility in Li-ion battery chemistry has also been tested employing SEM, EIS and XPS. This work shows initial efforts in designing a new kind of electrode matrix that enables a greener fabrication of Li-ion batteries.References J. Zhao, X. Yang, Y. Yao, Y. Gao, Y. Sui, B. Zou, H. Ehrenberg, G. Chen, and F. Du, Adv. Sci., 5, 1700768 (2018).D. Bresser, D. Buchholz, A. Moretti, A. Varzi, and S. Passerini, Energy Environ. Sci., 11, 3096–3127 (2018).V. A. Nguyen and C. Kuss, J. Electrochem. Soc., 167, 065501 (2020).V. A. Nguyen, J. Wang, and C. Kuss, J. Power Sources Adv., 6, 100033 (2020).