No abstract

No abstract

A modified spherically-shaped natural graphite (M-SNG) material is prepared, and its physical and electrochemical properties for use as an anode material in lithium-ion batteries are reported. M-SNG is obtained by ultrasonication in a carbon precursor solution, followed by heat-treatment at 1,200°C under argon atmosphere. A gap between the flaky NG fragments forms on the surface and inside the M-SNG particles; amorphous carbon is present in this gap and on the M-SNG particle surface. The M-SNG anode exhibits superior electrochemical performance compared to a commercial carbon-coated SNG (C-SNG) anode, with high charge/discharge rate capability and stable capacity retention. The enhanced charge/discharge rate capability is attributed to the good soaking ability of the M-SNG anode, which allows the electrode to maintain low polarization even at high current density. The amorphous carbon coating on the surface and inside of the M-SNG suppresses side reactions with the electrolyte during charge–discharge cycles, facilitating excellent cycling stability, good thermal stability, and adequate dimensional stability.

The assembly of the micron-sized Si/CNT/carbon composite wrapped with graphene (SCG composite) is designed and synthesized via a spray drying process. The spherical SCG composite exhibits a high discharge capacity of 1789 mAh g -1 with an initial coulombic efficiency of 84 %. Moreover, the porous architecture of SCG composite is beneficial for enhancing cycling stability and rate capability. In practice, a blended electrode consisting of spherical SCG composite and natural graphite with a reversible capacity of ~500 mAh g -1 , shows a stable cycle performance with high cycling efficiencies (> 99.5%) during 100 cycles. These superior electrochemical performance are mainly attributed to the robust design and structural stability of the SCG composite during charge and discharge process. It appears that despite the fracture of micro-sized Si particles during repeated cycling, the electrical contact of Si particles can be maintained within the SCG composite by suppressing the direct contact of Si particles with electrolytes.

No abstract