Synergistic Integration of Hierarchical Secondary Si/C Microrod Architecture and Fluorinated Ether Electrolyte for Stable Lithium-Ion Batteries

Abstract Increasing the energy density of lithium-ion batteries is a central challenge for next-generation electrified technologies. Silicon (Si) is a premier anode candidate due to its high theoretical capacity; yet, its practical use is hindered by extreme volume expansion and subsequent mechanical failure. To address these chronic issues, we demonstrate a comprehensive electrode-electrolyte engineering strategy by synergistically pairing a hierarchical secondary Si/C microrod (μ-rod) architecture with a customized ether-based electrolyte. This approach targets to bridge the gap between nanoscale reaction kinetics and microscale electrode stability without relying on complex, nonscalable particle synthesis. Multiscale structural characterizations confirmed the robust, anisotropic geometry of the secondary micrometer-sized rods consisting of the nanocrystalline Si primary particles. Electrochemical evaluations demonstrate that the integrated μ-rod architecture exhibits superior electromechanical stability when paired with the fluorinated ether electrolyte, outperforming conventional carbonate systems. Consequently, the Li||Si half-cell achieved 76.4% capacity retention after 300 cycles, while practical validation in a Si||NMC622 full cell revealed 71.4% capacity after 100 cycles. Operando strain measurements demonstrate mechanically resilient response of the μ-rod architecture in fluorinated ether electrolyte. These results highlight the synergy between a commercially viable mesoscale structured electrode and a compatible electrolyte in enabling structurally durable and electrochemically stable Si-based anodes.