Auxetic materials
possess special applications due to their unique
negative Poisson’s ratios (NPRs). As a classic 2D carbon material,
the NPR of graphene is still deliberated. Introducing the NPR in graphene
would increase its extraordinary properties, and the NPR together
with other properties would bring more significant applications for
graphene. In this Letter, on the basis of first-principles calculations,
we reconfigure the structure of graphene, and, as an example, we propose
a new 2D planar carbon allotrope, xgraphene, which is constructed
by 5–6–7 carbon rings. Our theoretical calculations
indicate that xgraphene has an NPR and constitutes a broad spectrum
of metal ion battery anodes with high performance. Its maximum storage
capacities are 930/1302/744/1488 mAh/g for Li/Na/K/Ca-ion batteries.
It has low metal-ion diffusion energy barriers (≤0.49 eV) and
low average open-circuit voltages (≤0.53 V). Our density functional
theory results also showed that it is intrinsically metallic and possesses
dynamic, thermal, and mechanical stabilities. Its intrinsic NPR, which
stems from the weakness of coupling of carbon–carbon bonds,
is found upon loading the uniaxial strain along the armchair direction.
This work not only opens up a new direction for the design of the
next-generation broad-spectrum energy-storage materials with low cost
and high performance but also offers a class application for auxetic
materials.
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