Investigation of silicon pore structure by metal-assisted chemical etching on the electrochemical performance of silicon-based anode

Abstract

Silicon, as a promising next-generation anode material, has the problems such as volume expansion and low electrical conductivity to limit its large-scale practical application. Herein, a porous Si/C composite (M-NpSi@C) is prepared from Mg₂Si and pitch, by tuning the pore structure of Si with metal-assisted chemical etching and carbonizing M-NpSi@pitch composite. The prepared porous silicon, M-NpSi-1.0, is of rich pores and high specific surface area with proper particle size and suitable pore distribution, attributed to the appropriate ratio of etchant to MpSi. Such pore characteristics promote effective penetration of the electrolyte to allow Li + diffusion onto Si surface, shorten Li + diffusion distance to expedite the kinetics, accommodate volume expansion to prevent Si cracking and even pulverization. Thus the obtained M-NpSi@C electrode presents not only a high reversible specific capacity of 1077 mAh g -1 after 550 cycles (capacity retention of 85.1%) at 1 A g -1 , but also excellent rate capability. At 5 A g -1 , the M-NpSi@C electrode can deliver a specific capacity of 527 mAh g -1 . This work provides an effective approach for the preparation of porous Si/C composite anode for high-energy batteries.