Chitosan as Enabling Polymeric Binder Material for Silicon‐Graphite‐Based Anodes in Lithium‐Ion Batteries

Massive volume change during (de‐)lithiation and subsequent challenges, such as pulverization of active materials, delamination of electrode from the current collector, and fragile solid electrolyte interphase, are among the main impediments hindering the large‐scale commercialization of silicon‐containing anode materials in lithium‐ion batteries. In this regard, designer polymeric binders with unique chemistries are considered as enabling solutions. Polymeric materials endowed with functional groups such as –OH, –COOH/COO − , and –NH 2 /NH 3 + , capable of building strong H bonds, are hailed as effective binders for Si‐containing anode materials. Herein, chitosan biopolymers are investigated as a green and environmentally friendly binder in a silicon/graphite (Si/Gr) anode and compared to lithium poly(acrylic acid)/sodium carboxymethyl cellulose binders. The effect of degree of acetylation (DA) and degree of polymerization of chitosan on the electrochemical performance of Si/Gr anode‐based cells is investigated. Anodes with chitosan binder with DA of 50% show the most promising electrochemical performance in Si/Gr||lithium metal and lithium nickel manganese cobalt oxide (NMC622)||Si/Gr cells. Crosslinking of chitosan binder with citric acid monohydrate in combination with free‐standing electrodes results in improved electrochemical performance in full cells. The surface chemistry of electrochemically cycled Si/Gr anodes with/without chitosan binder is investigated by X‐ray photoelectron spectroscopy.