Metallic Tin Nanoparticle-Reinforced Tin-Doped Porous Silicon Microspheres with Superior Electrochemical Lithium Storage Properties

Abstract

Improving the electronic conductivity and drastic volume expansion is attractive and challenging for constructing high-performance Si-based anode materials for lithium-ion batteries. Herein, tin-doped porous silicon microspheres embedded with tin nanoparticles (Sn–PSi@Sn) are fabricated from easily available low-cost silicon–aluminum alloy precursors through a simple and scalable strategy with a chemical replacement/etching and a low-temperature annealing process. The 3D porous framework structure of Sn–PSi@Sn microspheres may buffer severe volume expansion during the electrochemical cycling and shorten the transport paths of Li+ ions. The doping of Sn atoms in the Si crystal lattice can lead to a lattice expansion in silicon, reinforce the electronic and ionic conductivities, and minimize the effect of Li trapping, which is advantageous for enhancing the rate performance and improving the initial Coulombic efficiency. The Sn nanoparticles anchoring in porous silicon microspheres may further improve the conductivity and structure stability of Sn–PSi@Sn composites. Based on the density functional theory calculation results, the effects of partial substitution of Sn into the Si lattice mentioned above have been successfully confirmed. As a consequence, the as-prepared tin-doped porous silicon microspheres embedded with tin nanoparticles show a high reversible capacity (1165.6 mA h g–1 at the 400th cycle at 1 A g–1), excellent rate properties (1433.4 mA h g–1 at a high rate of 2.5 A g–1), and superior cycling performance at an ultrahigh rate (910.9 mA h g–1 at the 500th cycle even at a high current density of 4 A g–1). This work provides a promising strategy to design high-performance anode composites.