Ultrasmall metal (Fe, Co, Ni) nanoparticles strengthen silicon oxide embedded nitrogen-doped carbon superstructures for long-cycle-life Li-ion-battery anodes

For silicon oxides (SiOx) as a prospective Li-ion-battery anode material, the low inherent conductivity and huge volume fluctuation during cycling immensely limit their electrochemical performance. Herein, a universal electrospray-carbonization approach to prepare ternary metal/SiOx/nitrogen-doped carbon (NC) superstructures is proposed. Accordingly, metal (Fe, Co, Ni, CoNi, FeNi, FeCo and FeCoNi) nanoparticles (NPs) and small SiOx NPs derived from rice husks (RHs) are homogeneously distributed in the NC matrix. Metal (Fe, Co, Ni) NP-embedded NC frameworks avoid the accumulation, increase the conductivity and accommodate adequent volume expansion of SiOx NPs. This results in an enhanced rate capability and excellent cycle stability upon cycling. Besides, Ni/SiOx/NC (NSC) superstructures with ultra-small Ni NPs can exhibit better electrochemical kinetics for fast diffusion of ions and charge transfer and cyclability than Co/SiOx/NC (CSC) and Fe/SiOx/NC (FSC) composites. When NSC superstructures are employed as lithium-ion battery (LIB) anodes, superior specific capacities of 757.5 mA h g−1 at the 200th cycle, as well as superb long cyclability with discharge capacities of 665.0 mA h g−1 for 500 cycles at 500 mA g−1 and 116.3 mA h g−1 at the 5000th cycle, even at 10 A g−1, are achieved. Furthermore, the easy and general approach for preparing multiple SiOx-, metal- or alloy-based superstructures paves the way for designing high-performance rechargeable batteries and electrocatalysts.