Hard carbon/graphite/nano-silicon ternary composite anode for high-performance Li-ion capacitors

Previously, a hard carbon (HC)/graphite (Gr) composite carbon (CC) anode for Li-ion capacitors (LICs) was noted to demonstrate outstanding cycling and rate performances. In this study, nano-Si was integrated into the CC matrices to develop a high-energy-density ternary composite anode for LICs. A twice-repeated prelithiation method was applied to stabilize the solid electrolyte interphase and eliminate the irreversible capacity of the composite anodes. This approach leveraged the high specific capacity of Si to enhance energy density, the amorphous carbon in HC to buffer the volume expansion of Si during charging, and the high electrical conductivity of Gr to improve rate performance. The ternary composite anodes were subjected to electrochemical characterization across a wider voltage range to maximize their energy density and assess durability under extreme conditions. The optimal CC:nano-Si mass ratio for the composite anode was determined through comparative studies. The composite anode with a CC:nano-Si mass ratio of 80:20 achieved a maximum energy density of 129.3 Wh kg⁻¹ and an outstanding energy density retention rate of 88.4 % after 10,000 cycles at 2.0–4.0 V. The retention rate was 90.1 % after an accelerated aging test involving additional 5000 cycles at 1.5–4.2 V.