Toward Li-ion Graphite Anodes with Enhanced Mechanical and Electrochemical Properties Using Binders from Chemically Modified Cellulose Fibers

Abstract

Cellulose nanofibers (CNFs) are bio-sourced nanomaterials, which, after proper chemical modification, exhibit a unique ability to disperse carbon-rich micro- and nanomaterials and can be used in the design of mechanically strong functional nanocomposites. When used in the preparation of graphite anodes for Li-ion batteries, they have the potential to outperform conventional binders such as carboxymethyl cellulose (CMC) and styrene–butadiene rubber (SBR) both electrochemically and mechanically. In this study, cellulose-rich fibers were subjected to three different chemical modifications (including carbonyl-, carboxyl-, and aldehyde-functionalization) to facilitate their fibrillation into CNFs during the preparation of aqueous slurries of graphite and carbon black. Using these binders, graphite anodes were prepared through conventional blade coating. Compared to CMC/SBR reference anodes, all anodes prepared with modified cellulosic fibers as binders performed better in the galvanostatic cycling experiments and in the mechanical cohesion tests they were subjected to. Among them, the aldehyde- and carboxyl-rich fibers performed the best and resulted in a 10% increase in specific capacity with a simultaneous two- and three-fold increase of the electrode material’s stress-at-failure and strain-at-break, respectively. In-depth characterizations attributed these results to the distinctive nanostructure and surface chemistry of the composites formed between graphite and these fiber-based binders.

Polymeric Binders Used in Lithium Ion Batteries: Actualities, Strategies and Trends

“…In addition, the rejection of the use of Carbon black (CB) which has high surface area additives, reduces the specific surface area of graphite electrode, while the use of PEDOT : PSS has low wettability, these two highlights determine the number of unstable SEI film on the anode surface will be reduced, so that the heat generated by the decomposition of the SEI film will be reduced, thereby reducing the probability of thermal runaway (Figure 7(e-h)). Francon et al [66] prepared a variety of cellulose-rich fibers (Figure 8(a-b)) modified by different functional groups (À C=O, À COOH, À CHO). The experimental results show that all fibers have better adhesion than SBR/ CMC.…”

Bio-Based Binder Development for Lithium-Ion Batteries

“…Modified cellulosic fibers, particularly those with aldehyde and carboxyl functionalities [ 75 ], hold promise as effective binders for graphite anodes in LIBs, offering both improved electrochemical performance and mechanical strength. In particular, TEMPO–periodate-oxidized cellulose electrodes showed higher specific capacities at high cycling rates (10% increase at 400 mA/g), because of the enhanced chemical compatibility with both graphite and the electrolyte, as well as an ability to form a strong fibrillar network that prevents structural damage upon graphite expansion [ 76 ]. Additionally, a sustainable approach was reported to produce freestanding CNF–graphite hybrids (90 wt% graphite) exhibiting energy storage performance (330 mAh/g) and processing speed on par with commercial graphite anodes [ 77 ].…”