Effects of pre-carbonization on the structure and performance of hard carbon in lithium cells

Abstract

The amount of lithium reversibly incorporated in the hard carbon (the reversible capacity), the faradic losses during the first charge–discharge cycle (the irreversible capacity), and the profile of the voltage curves all depend on the structure, the texture, and the heteroatom content which are affected significantly by fabrication method of hard carbon material. We demonstrate herein a simple mass production routine to prepare hard carbon with advanced electrochemistry performance by pyrolysing resin precursors. Pre-carbonization before high temperature pyrolysis (1000 °C) by controlled process conditions, such as temperature and ramp rates, has an important effect on the structure and performance of hard carbon as anode material. Hard carbon material was characterized by X-ray diffraction (XRD), Raman spectroscopy, Brunauer–Emmett–Teller (BET) surface area, and scanning electron microscope (SEM). The hard carbon treated by pre-carbonization process resulted in increasing Raman I G/I D ratio, BET specific surface area, and micropore volume, which can serve as high reversible capacity anode material for Li-ion batteries. The 500-1 sample performed a first discharge capacity and reversible capacity of 540 and 390 mAh g−1, respectively, which was much higher than that of non-pretreatment (NP) (without pre-carbonization) sample (290 and 210 mAh g−1, respectively).