A lithium-ion battery with cycling stability promoted by the progressive activation of a silicon oxide anode in graphene-amorphous carbon matrix

A composite anode including silicon oxide, amorphous carbon and few-layer graphene (FLG) is investigated for Li-ion battery. The material reflects both the amorphous structure of the silicon oxide and the crystalline one of the FLG, with a morphology consisting of micrometric FLG flakes and carbon surrounded by nanometric particles of silicon oxide. The electrode shows reversible Li-alloying and Li-insertion processes between 0.01 and 0.30 V vs. Li+/Li, as well as an interphase progressively improving and activating upon cell operation, with a decrease of the resistance. Galvanostatic cycling shows maximum capacity of about 400 mAh g−1, rate capability extended to 240 mA g−1, and cell life of 200 cycles with capacity retention of 94%. The anode is chemically pre-lithiated to remove the initial irreversible capacity using direct contact with lithium metal, and combined with a LiNi0.33Mn0.33Co0.33O2 (NCM) layered oxide cathode in a Li-ion battery. The full-cell shows an electrochemical process centered at 3.5 V with a capacity of 158 mAh g−1 retained for 90% over 120 cycles, a coulombic efficiency exceeding 98%, and rate capability extended up to 3C. Ex-situ studies of the electrodes evidence the full retention of the morphology and structure over cycling.