Vertical channels enable excellent lithium storage kinetics and cycling stability in silicon/carbon thick electrode

Abstract

Constructing silicon (Si)-based composite electrodes that possess high energy density, long cycle life, and fast charging capability simultaneously is critical for the development of high performance lithium-ion batteries for mitigating range anxiety and slow charging issues in new energy vehicles. Herein, a thick silicon/carbon composite electrode with vertically aligned channels in the thickness direction (VC-SC) is constructed by employing a bubble formation method. Both experimental characterizations and theoretical simulations confirm that the obtained vertical channel structure can effectively address the problem of sluggish ion transport caused by high tortuosity in conventional thick electrodes, conspicuously enhance reaction kinetics, reduce polarization and side reactions, mitigate stress, increase the utilization of active materials, and promote cycling stability of the thick electrode. Consequently, when paired with LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622), the VC-SC||NCM622 pouch type full cell (∼6.0 mAh cm^–2) exhibits significantly improved rate performance and capacity retention compared with the SC||NCM622 full cell with the conventional silicon/carbon composite electrode without channels (SC) as the anode. The assembled VC-SC||NCM622 pouch full cell with a high energy density of 490.3 Wh kg^–1 also reveals a remarkable fast charging capability at a high current density of 2.0 mA cm^–2, with a capacity retention of 72.0% after 500 cycles.

Keywords

high transport kinetics / silicon/carbon anode / structural stability / thick electrode / vertical channels

Author summay

Wen Zhang and Zihan Zhang contributed equally to this study.