Smart Binders for Silicon Based Composite Electrode in Li-Ion Batteries

Abstract

Silicon is one of the most promising alloying anode materials for Li-ion batteries thanks to its high specific and volumetric capacity. In comparison with the commercially available graphite, silicon delivers 10 times higher specific capacity (up to 3600 mA.h.g-1) and 3 times higher volumetric capacity ( up to 2200 mA.h.cm-3) [1]. However, silicon suffers from high volumic expansion upon lithiation (up to 280 %). It induces the pulverization of the micrometric silicon particle, the perpetual solid electrolyte interface renewal and decohesion between constitutive elements of the electrode, drastically reducing its lifespan [2].To tackle those issues we propose the formulation of composite electrode with improved binder. It is composed of carboxymethyl cellulose sodium salt (NaCMC, as a binding network) and zinc sulfate dissolved in a pH 3 buffer solution (composed of citric acid and potassium hydroxide). The originality and improvement comes from the use Zn2+ ions as coordination agents, binding to carboxylate groups from the CMC and citric acid. Among benefits, we believe that the coordination helps to mitigate the stress inside the electrode because of the improved reticulation of the network, thus improving its resilience [3]. To support this hypothesis, we provide physico-chemical characterizations of the binder as well as the electrochemical performances of our electrodes. [1] M.N. Obrovac, V.L. Chevrier, Alloy Negative Electrodes for Li-Ion Batteries. Chem. Rev. 2014, 114, 11444-11502. [2] A. Etiemble, A. Tranchot, T. Douillard, H. Idrissi, E. Maire, L. Roué., Evolution of the 3D Microstructure of a Si-Based Electrode for Li-Ion Batteries Investigated by FIB/SEM Tomography, J. Electrochem. Soc. 2016,163, A1550-A1559 [3] D. Mazouzi, R. Grissa, M. Paris, Z. Karkar, L. Huet, D. Guyomard, L. Roué, T. Devic, B. Lestriez, CMC-citric acid Cu(II) cross-linked binder approach to improve the electrochemical performance of Si-based electrodes. Electrochim. Acta 2019, 304, 495-504.