Durable silicon-carbon composites self-assembled from double-protected heterostructure for lithium-ion batteries

Silicon-carbon composites have been faced with the contact issues between silicon and carbon in the form of material aggregation and inferior dispersion, leading to electrode cracking or kinetic degradation during cycling. In addition to dispersion improvement from interfacial linkage between self-assembled Si nanoparticles (SiNPs) and carbon fibers (CNFs), the positive influences of high-content carboxymethyl cellulose(CMC) (25 wt%) and amorphous carbon are also expected, respectively after the second-step self-assembly and subsequently sintering.

A novel composite (i.e. Si-CNF@C) with the decoration of entire SiNPs in the framework of both CNFs and amorphous carbon was prepared via two-step electrostatic self-assembly followed by sintering. Such a composite with heterogeneous nanostructure was used as a lithium-ion battery anode without additional binders or conductive agents.

SiNPs can be well protected with CNFs and amorphous carbon against the dispersion and contact problems under both effects of electrostatic attraction and chemical bonding. With the double-protected heterostructure, such a novel Si-CNF@C electrode exhibits highly reversible capacities of 1200 mAh g^-1, 982 mAh g^-1, and 849 mAh g^-1 after 100, 500, and 1000 cycles at 0.5 A g^-1, respectively. The long-term cycling stability with a capacity loss of 0.036% per cycle over 1000 cycles is comparable.