Silicon is considered as an ideal anode material for the next generation of lithium-ion batteries (LIBs) owing to its high specific capacity, low lithiation potential, and high natural abundance. However, its potential application is greatly restricted by poor electrical conductivity and large volume expansion during lithiation/delithiation processes. Herein, a novel solid-state reaction route is developed to synthesize a silicon/carbon nanotubes/carbon (Si/CNTs/C) composite by directly reacting magnesium silicide (Mg 2 Si) with lithium carbonate (Li 2 CO 3 ). This method realizes synchronous formation of Si, CNTs, and amorphous carbon with a good interfacial configuration. Transmission electron microscopy (TEM) reveals that MgO may be responsible for the in situ growth of CNTs during the chemical reaction process. The crystalline Si particles are encapsulated by CNTs and the amorphous carbon matrix, which not only accommodates the volume expansion of Si but also enhances the integral electronic conductivity. Consequently, the Si/CNTs/C composite exhibits a high reversible capacity (702 mA h g −1 at 0.2 A g −1 ), excellent rate performance (420 mA h g −1 at 5 A g −1 ), and long cycling life (over 1500 cycles) when used as an anode for LIBs. Notably, this research might provide a new strategy for large-scale synthesis and utilization of Si/C composites in high-performance LIBs.

Replacing lithium with a Si anode is a very promising route for the development of all-solid-state batteries (ASSBs) to eliminate the uncontrolled growth of Li dendrites. However, the Si anode still undergoes low electric conductivity and severe volume changes during cycling leading to poor interfacial stability against solid electrolytes. Herein, we report an integrated anode of silicon/ carbon-nanotubes/carbon (Si/CNTs/C) for the stable operation of sulfide-based ASSBs. The in situ synthesized Si/CNTs/C from Mg 2 Si reacting with CaCO 3 in the presence of a ferrocene catalyst for CNT growth exhibits a similar ″reinforced concrete″ structure, where CNTs provide a mechanical stable scaffold for Si particle embedding. In this composite, CNTs act as a ″reinforcing bar″ fixing Si active particles tightly, which not only maintain good interfacial contact between Si and Li 6 PS 5 Cl components but also alleviate the volume expansion of Si and prevent the lithium-ion channel of Li 6 PS 5 Cl from being destroyed. As the anode for ASSBs, the reversible capacity of Si/CNTs/C was 1226 mA h g −1 after 50 cycles at 50 mA g −1 . This study provides an idea for the application of Si-based materials in ASSBs.

The Si/C anode is one of the most promising candidate materials for the next-generation lithium-ion batteries (LIBs). Herein, a silicon/carbon nanotubes/carbon (Si/CNTs/C) composite is in situ synthesized by a one-step reaction of magnesium silicide, calcium carbonate, and ferrocene. Transmission electron microscopy reveals that the growth of CNTs is attributed to the catalysis of iron atoms derived from the decomposition of ferrocene. In comparison to a Si/C composite, the cycle stability of the Si/CNTs/C composite can obviously be improved as an anode for LIBs. The enhanced performance is mainly attributed to the following factors: (i) the perfect combination of Si nanoparticles and in situ grown CNTs achieves high mechanical integrity and good electrical contact; (ii) Si nanoparticles are entangled in the CNT cage, effectively reducing the volume expansion upon cycling; and (iii) in situ grown CNTs can improve the conductivity of composites and provide lithium ion transport channels. Moreover, the full cell constructed by a LiFePO4 cathode and Si/CNTs/C anode exhibits excellent cycling stability (137 mAh g–1 after 300 cycles at 0.5 C with a capacity retention rate of 91.2%). This work provides a new way for the synthesis of a Si/C anode for high-performance LIBs.