Flexible, binder-free, freestanding silicon/oxidized carbon nanotubes composite anode for lithium-ion batteries with enhanced electrochemical performance through chemical reduction

Abstract

Multi-walled carbon nanotubes (MWCNTs) can mitigate the issues of volume expansion and low electrical conductivity in silicon (Si) anodes, enabling the fabrication of binder-free, freestanding electrodes. However, MWCNTs tend to aggregate due to π-π interactions associated with sp2 orbitals, necessitating the use of dispersants or acid treatment to improve dispersion. To enhance dispersion, we applied an acid treatment; however, this led to a reduction in electrical conductivity due to a decrease in pz orbitals. To overcome this issue, we introduced an additional chemical reduction step after fabricating the Si/oxidized MWCNT (OCNT) composite anode, which preserved the dispersion of MWCNTs while restoring electrical conductivity. The chemically reduced Si/OCNT composite anode exhibited significantly decreased charge transfer resistance before and after cycling, along with excellent bending resistance. As a result, it maintained a stable discharge specific capacity of 768 mAh g−1 even after 150 cycles. Collectively, our findings highlight the critical role of chemical reduction in enhancing the electrochemical performance of Si/OCNT composite anodes, presenting a promising approach for next-generation lithium-ion batteries. © 2024 Elsevier B.V.