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

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).