Low pressure preparation of spherical Si@C@CNT@C anode material for lithium-ion batteries

• Si@C@CNT@C is prepared by forming precursors under vacuum condition.
• Si@C@CNT@C reveals spherical shape as lithium storage material.
• Si@C@CNT@C delivers a reversible capacity of 563.5 mA h g−1 after 60 cycles.

Si@C@CNT@C composite is prepared by preliminary low-pressure forming Si@C and Si@C@CNT precursors from Si powder. After pyrolysis from glucose, acetylene and pitch, Si@C@CNT@C shows a spherical multi-phase composite structure. By using as lithium storage material, Si@C@CNT@C shows an initial discharge capacity of 620.5 mA h g−1 with an initial coulombic efficiency of 82.2%. After 60 cycles, this spherical sample can maintain a reversible capacity of 563.5 mA h g−1 at 100 mA g−1, corresponding to a capacity retention of 90.8%. For comparison, the reversible capacities for Si powder, Si@C and Si@C@CNT are 10.9, 380.3 and 494.6 mA h g−1, respectively. Even cycled at 400 mA g−1, Si@C@CNT@C can deliver a reversible lithium storage capacity of 389.2 mA h g−1. It indicates that spherical Si@C@CNT@C can be used as a high performance anode material for lithium-ion batteries.

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