Directly grown carbon nanotube networks on SiOx for preserving conductivity under extreme volume change for high-silicon-content anodes

This work presents a promising strategy to increase silicon content in lithium-ion battery (LIB) anodes while preserving a robust conductive network. By directly growing carbon nanotubes (CNTs) on silicon suboxide (SiO x ) particles, a high concentration of CNTs protruding from the surface of SiO x surface were localized near the SiO x particles, where electrical isolation caused by severe volume change during cycling leads to rapid degradation. Scanning electron microscopy and operando imaging revealed that the directly grown CNT–SiO x composite (G-SC) electrode exhibited reduced thickness swelling and better-preserved conductive networks during cycling, compared to the conventionally mixed CNT–SiO x composite (M-SC). Full-cell tests paired with LiNi₀.₈Mn₀.₁Co₀.₁O₂ (NMC811) cathodes under static pressure confirmed lower dimensional changes in the NMC811|G-SC cell than in NMC811|M-SC. Electrochemical analyses—including cyclic voltammetry, galvanostatic titration, electrochemical impedance spectroscopy, and galvanostatic cycling—demonstrated enhanced redox kinetics and stable reversibility for the G-SC anode. dQdV −1 analysis revealed that maintaining the conductive network is essential for suppressing capacity facing arising not only from silicon degradation but also graphite isolation. A high-loading NMC811|G-SC coin cell retained 77% of its capacity after 1000 cycles, while a single-layer pouch cell delivered high energy densities of 309 Wh kg −1 and 865 Wh L −1 with 90% capacity retention after 220 cycles. These results underscore the practicality and scalability of the G-SC architecture for next-generation high-energy LIBs with high‑silicon-content anodes. • Direct CNT growth on SiOx preserves conductive networks under extreme volume changes in LIB anodes. • G-SC electrode reduces thickness swelling by ∼50% vs. mixed CNT-SiOx during cycling. • Achieves 77% capacity retention after 1000 cycles in NMC811|G-SC coin full cells. • Single-layer pouch cell delivers 309 Wh kg −1 with 90% retention after 220 cycles. • Enhances Li + diffusion and forms stable LiF-rich SEI, suppressing Si/graphite isolation.