Designing of hierarchical mesoporous/macroporous silicon-based composite anode material for low-cost high-performance lithium-ion batteries

Abstract

Despite the fact that the silicon-based anode has attracted immense attention with extremely high theoretical capacity, practical applications have been impeded by severe capacity fading during cycling processes and high preparation cost. In this work, a mass-produced and low-cost hierarchical mesoporous/macroporous silicon-based composite material with an ample porous structure and dual carbon protective layers has been rationally designed and constructed. Through adjusting the phase ratio of intermediate products (Mg₂Si and MgO), the traditional magnesiothermic reduction method based on the low cost silicon source of diatomaceous earth (DE) has been precisely optimized to fabricate a controlled mesoporous structure on the original macroporous structure of DE. Furthermore, dual carbon protective layers on the hierarchical mesoporous/macroporous structure silicon-based composite material have also been constructed using the vacuum adsorption technique, showing that both the porous channel and the composite material surface are wrapped with carbon. Electrochemical performance tests show that both the controlled mesoporous/macroporous structure and dual carbon protective layers have enhanced the cycle stability of the Si/SiO₂@C composite anode material for lithium-ion batteries. The capacity retention of the hierarchical mesoporous/macroporous Si/SiO₂@C composite material with 13% carbon can reach 99.5% after 200 electrochemical cycles, and the reversible capacity can reach 534.3 mA h g⁻¹ even at 500 mA g⁻¹. This paper not only provides a low-cost and high electrochemical property silicon-based composite anode material for lithium-ion batteries, which possesses important significance in both academic and industrial worlds, but also opens up a way on how to design the hierarchical mesoporous/macroporous structure with precision control on the phase ratio.