Influence of Degree of Substitution of Carboxymethyl Cellulose on High Performance Silicon Anode in Lithium-Ion Batteries

Binder is one of the key materials which affect the electrochemical performance of the Li-ion batteries. As a promising binder, carboxylmethyl cellulose (CMC) is a derivative of cellulose, in which the hydroxyl (3 per unit) is replaced by the carboxymethyl group. It attaches more and more attention. However, few studies have been carried out on CMC with the degree of substitution (DS). In this study, CMC with different DS was synthesized by a specially designed method. The raw materials and products were characterized with FT-IR, H-1-NMR, C-13-NMR and XRD. A series of CMC with different DS were prepared as silicon-based binder of anode of lithium-ion batteries. Electrical tests, including galvanostatic charge-discharge, cyclic voltammetry, AC impedance and rate capability were performed to evaluate the silicon-based anode. Results showed that the discharging specific capacity of silicon-based anode using CMC of DS = 0.55 in the first and 50th cycle were 2917.0 mAh/g and 1607.6 mAh/g, and the electrochemical performance was superior to those using CMC with lower (0.23 and 0.43) or higher (0.72 and 0.86) DS. The current study confirms that DS of CMC has strongly affected battery performance parameters such as deliverable capacity, power, cycle-life and storage performance etc. The working mechanism is also investigated on why the CMC with the best DS is compatible with the silicon-based anode. (C) The Electrochemical Society of Japan, All rights reserved.