Quantum-confined ultramicropores in nodal-line semimetal C32 for high-efficiency lithium/sodium-ion battery anodes

Carbon-based materials integrating ultramicroporous architectures with topological quantum characteristics have recently gained prominence as next-generation ion battery anodes due to their exceptional electron/ion transport synergies. Through first-principles calculations, we propose a kind of two-dimensional (2D) tetragonal carbon allotrope (C32) possessing robust structural stability across mechanical, dynamical, and thermal domains. This material's unique sp2/sp3-hybridized bonding network simultaneously establishes uniformly distributed ultramicroporous channels (5.43 Å pore diameter, effectively preventing solvent co-intercalation) and manifests highly conductive nodal-line semimetallic properties. Theoretical simulations reveal exceptional Li/Na storage characteristics in bulk C32, including high theoretical capacities (837 mAh/g for Li, 558 mAh/g for Na), low diffusion barriers (0.22 eV for Li, 0.60 eV for Na), and moderate open-circuit voltages (0.26 V for Li, 0.33 V for Na). Notably, it has significantly lower volumetric expansion compared to conventional graphite during Li+/Na+ intercalation. Our work proposes a kind of optimization strategy combining topological electronic state modulation with precise pore structure design, suggesting an effective method for developing high-energy-density and long-cycle-life Li/Na-ion battery anodes.