Preparation of Highly Porous Silicon As an Anode for Lithium Ion Batteries

Abstract

The mobile world depends on lithium ion batteries (LIBs), which provide portable power for variety of applications, ranging from personal electronic devices such as laptops, mobile phones, digital cameras to electric vehicles due to the high energy density, low self-discharge and long cycle life of LIBs. Nevertheless, current LIBs cannot still meet recent increased needs for higher energy density batteries from industries. Nowadays, LIBs can store more than double (200 Wh kg-1) energy density compared with the first commercial LIB. However, this value is still far from the goal in energy density of battery (400 Wh kg-1). Basically, this limitation of LIBs originates from their electrode materials; graphite as an anode and LiCoO2 as a cathode. Accordingly, to improve the energy and power densities of the LIBs, one of the easiest ways is to replace the conventional anode and cathode materials by other advanced materials with better capacity, rate capability, etc. In this context, Li alloys have emerged as a promising alternative candidate to replace graphite anode for LIBs due to the high specific capacity of the Li alloys. Although issues related to poor capacity retention of Li alloys caused by the large volume change during the lithiation/delithiation process have been addressed using new binders and electrolyte additives, the practical application of Li alloys as an anode is still a challenge, especially due to the limited rate capability of the Li alloys. Among the Li alloy based materials, silicon (Si) is considered the most suitable anode for LIBs due to the high theoretical capacity of 4200 mAh g-1 and low cost of Si. In this work, we report the synthesis of highly monodisperse porous Si using a simple and scalable method. The porous nature of the Si enabled the homogeneous stress distribution within the structure during lithiation and delithiation, leading to the dramatic improvement in electrochemical stability. In particular, the high porosity offered the large electrolyte accessible surface area, the short Li-ion diffusion path, and the void spaces necessary for volume expansion. The porous silicon demonstrated the excellent reversible capacity and the minimal capacity fading for longer than 100 cycles at the high rate of C/10 (80% capacity retention with ~100% Coulombic efficiency). Further, this material exhibited the potential as an anode material for lithium-sulfur analogous battery.