Distribution Uniformity of Water-Based Binders in Si Anodes and the Distribution Effects on Cell Performance

The concentration distributions of binders, carboxymethyl cellulose (CMC) and a composite of styrene-butadiene rubber (SBR) and CMC, in dried silicon anodes are studied, and the effects of their distributions on the electrochemical properties of the constructed cells are discussed. When a silicon electrode is prepared with a single binder of CMC, the binder is uniformly distributed in the drying/thickness direction of the electrode sheet. However, the binder distribution becomes less uniform when CMC is composited with SBR; this is because the contained SBR tends to migrate with the solvent during the drying process and finally accumulates on the top surface of the electrode. The nonuniform distribution of SBR weakens the adhesion strength of the electrode sheet on the current collector, thereby increasing the impedance of the fabricated anode and decreasing the capacity, rate capability, and cycle life of the constructed lithium-ion cell.