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

Abstract

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 –NH2/NH3+, 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.

Bio‐Inspired Electrodes with Rational Spatiotemporal Management for Lithium‐Ion Batteries

“…[38] Traditional binders like polyvinylidene fluoride (PVDF), prevalent in the battery industry, suffer from recognized limitations, including limited binding strength owing to inadequate mechanical properties, lack of chemical bonds with electroactive materials, and low electronic and lithium-ion conductivities. [157] Emerging binders, comprised of developed molecules and polymers possessing intrinsic self-healing capabilities based the dynamic supramolecular assembly, [54] such as hydrogen bonds, electrostatic crosslinking, and host-guest or van der Waals interactions, [57,133,156] offer promising solutions. These self-healing binders maintain electrode integrity through mechanical properties and interactions with electrode surfaces.…”

“…[ 52 , 53 , 56 ] This can lead to electrode delamination from the current collector. [ 133 ] Consequently, side reactions with the electrolyte occur, causing severe structural pulverization and rapid capacity fading of the electrode. [ 38 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 ] Therein, the Si anode forms SEI and achieves prelithiation during the first cycle, resulting in excess lithium‐ion consumption and large irreversible capacity losses.…”