A 2D Si@GC nanosheet composite is synthesized through a facile ball-milling method using NaCl as a bifunctional template, which can achieve a high reversible capacity and long-term cycling performance when evaluated as an anode material for LIBs.
Electrochemical
exfoliation starting with graphite powder
as the
raw material for graphene production shows superiority in cost effectiveness
over the popular bulk graphite. However, the crucial conductive network
inside the graphite powder electrode along with its formation and
influence mechanisms remains blank. Here, an adjustable-pressure graphite
powder electrode with a sandwich structure was designed for this.
Appropriate encapsulation pressure is necessary and conducive to constructing
a continuous and stable conductive network, but overloaded encapsulation
pressure is detrimental to the exfoliation and graphene quality. With
an initial encapsulation pressure (IEP) of 4 kPa, the graphite powders
expand rapidly to a final stable expansion pressure of 49 kPa with
a final graphene yield of 46.3%, where 84% of the graphene sheets
are less than 4 layers with I
D/I
G values between 0.22 and 1.24. Increasing the
IEP to 52 kPa, the expansion pressure increases to 73 kPa, but the
graphene yield decreases to 39.3% with a worse graphene quality including
higher layers and I
D/I
G values of 1.68–2.13. In addition, small-size
graphite powders are not suitable for the electrochemical exfoliation.
With the particle size decreasing from 50 to 325 mesh, the graphene
yield decreases almost linearly from 46.3% to 5.5%. Conductive network
and electrolyte migration synergize and constrain each other, codetermining
the electrochemical exfoliation. Within an encapsulated structure,
the electrochemical exfoliation of the graphite powder electrode
proceeds from the outside to the inside. The insights revealed here
will provide direction for further development of electrochemical
exfoliation of graphite powder to produce graphene.
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