Effect of Carboxymethyl Cellulose on Aqueous Processing of Natural Graphite Negative Electrodes and their Electrochemical Performance for Lithium Batteries

Abstract

Suspensions of natural graphite particles were prepared in an aqueous medium using carboxymethyl cellulose ͑CMC͒ and emulsified styrene-butadiene copolymer latex as part of an environmentally friendly fabrication process for graphite anodes ͑negative electrodes͒ intended for application in Li-ion batteries. Suspensions were characterized by adsorption isotherms, electroacoustic measurements, rheology and sedimentation tests, at two different degrees of carboxymethyl substitution ͑DS͒ on CMC. A lower DS value ͑0.7͒ resulted in greater uptake of CMC on graphite compared with a higher DS value ͑1.28͒. This was attributed to attractive hydrophobic interactions associated with the lower carboxymethyl substitution. The greater adsorption for DS = 0.7 correlates with lower relative viscosity in concentrated graphite suspensions, a higher adhesion strength with a copper substrate, and a greater retention of discharge capacity after cycling. The effect of DS is attributed to differences in the aqueous dispersion properties and stability of graphite suspensions. Based on these results, we fabricated high-capacity graphite negative electrodes characterized by gravimetric and volumetric energy densities of greater than 340 mAh/g and 560 mAh/cm 3 , respectively. This formulation also led to improved adhesion strength, giving the as-fabricated cell an attractive cycle life greater than 90% of initial discharge capacity after 200 cycles.

Recent Progress on Polymeric Binders for Silicon Anodes in Lithium-Ion Batteries

“…It was reported that by varying levels of carboxymethyl (-OCH 2 COO -Na + ) substitution, the adhesion of active materials to a copper current collector and the dispersion of the electrode slurry can be controlled [28]. Munao et al demonstrated that the aggregation of PVDF binder and Si particles was more severe compared to a CMC-Si electrode; thus, the PVDF-Si electrode loses its electrical conduction network [29].…”

Water-soluble binders for MCMB carbon anodes for lithium-ion batteries

“…The DS indicates the average number of carboxymethyl groups attached to the glucose unit. A low DS usually provides better performance because of additional interactions between NaCMC and graphite [40]. For this study, it has been decided to use NaCMCs with a low degree of substitution, ranging from 0.7 to 0.8.…”

Sodium Alginate: A Water-Processable Binder in High-Voltage Cathode Formulations

“…Many studies have indicated that water processable cellulose-like materials may be suitable binders for both anode and cathode. 10,19,21,22 The use of carboxymethylcellulose (CMC) as binder for a graphitebased anode material was first described by Lee et al 23 CMC binder has been proposed also for Si-based electrodes. It can promote the formation of a stable solid electrolyte interface (SEI) layer by acting as a surface modifier and can facilitate networking between the conductive carbon and the Si particles because of its extended structure.…”