Application of high-strength, high-density, isotropic Si/C composites in commercial lithium-ion batteries

Abstract

Although nanostructured Si can overcome the huge volume expansion during lithiation without breakage, in practical applications, it is Si/C composites that are used as anode in lithium batteries, in which volume expansion of Si can easily transmit to Si/C leading to rupture of composites, therefore, electrical contact loss and poor cyclability. So far, few reported Si/C composites can meet real application requirements. High structural strength of Si/C is a prerequisite for applications and, although it cannot inhibit the expansion when Si becomes Li15Si4, it can inhibit the irreversible expansion caused by the randomly increase of defect during the repeated phase transition of Si, and can prevent the rupture of composite particles during the compaction and cycling. In this work, a high-strength, high-density, isotropic Si/C composite was applied in commercial cylindrical cells with NCM811, and it exhibited a capacity retention of 83.8% over 1000 cycles at 2.5–4.2 V and 89.0% at 2.75–4.15 V, where charge/discharge rate was 0.5C/1C.