A cycling robust network binder for high performance Si–based negative electrodes for lithium-ion batteries

Abstract

Silicon has been a pivotal negative electrode material for the next generation lithium-ion batteries due to its superior theoretical capacity. However, commercial application of Si negative electrodes is seriously restricted by its fast capacity fading as a result of severe volume changes during the process of charge and discharge. A novel functional binder is essential to resolve this conflict. In this work, we have proposed a composite of carboxymethyl cellulose (CMC) and cationic polyacrylamides (CPAM) as an effective network binder to improve the electrochemical performance of Si–based negative electrodes in lithium-ion batteries. The CMC–CPAM composite binder is cross-linked physically through reversible electrostatic interaction. Unlike common covalent cross-linked binders, the network structure of it forms spontaneously at room temperature, which makes it self-healing. Besides, benefits from the use of high molecular CPAM, the CMC–CPAM network binder exhibits excellent mechanical and adhesive strength, which makes it robust enough to tolerate the volume change of Si. As a result, the Si electrode with the self-healing CMC–CPAM composite binder shows an excellent cycling stability than the covalent cross-linked CMC−polyacrylic acid (PAA) and linear CMC binders, with a capacity of 1906.4 mAh·g−1 remaining after 100 cycles. Moreover, the cycling performance of retaining 78% of the initial capacity after 350 cycles is achieved based on the commercial Si@C/graphite negative electrode using the self-healing CMC–CPAM network binder with a very high mass loading (~4 mg·cm−2).