Superior ionic and electronic properties of ReN₂ monolayers for Na-ion battery electrodes

Abstract

Excellent monolayer electrode materials can be used to design high-performance alkali-metal-ion batteries. Here, we propose two-dimensional ReN monolayers as superior sodium-ion battery materials. Our total energy optimization results in a buckled tetragonal structure for the ReN monolayer, and our phonon spectrum and elastic moduli prove that it is dynamically and mechanically stable. Further investigations show that it is metallic and still keeps its metallic feature after the adsorption of Na or K atoms, and the adsorption of Na (or K) atoms changes the lattice parameters by 3.2% (or 3.8%) at most. Its maximum capacity reaches 751 mA h g for Na-ion batteries or 250 mA h g for K-ion batteries, and the diffusion barrier is only 0.027 eV for the Na atom or 0.127 eV for the K atom. The small lattice changes, high storage capacity, metallic feature, and extremely low ion diffusion barriers make the ReN monolayers a superior electrode material for Na-ion rechargeable batteries with ultrafast charging/discharging processes.

Large-Gap Quantum Spin Hall States in the Bilayer Hexagonal Structure of Rhenium and Technetium Dinitrides: A First-Principles Study

“…The lattice constant of this BHS-ReN 2 nanosheet is 6.28 Å, and its thickness is 4.32 Å. Following the previous work, the cohesive energy ( E coh ) of the ReN 2 nanosheet is calculated as E coh = E ReN 2 – E Re – E N 2 , where E ReN 2 , E Re , and E N 2 are the total energies of the ReN 2 nanosheet, isolated Re atom, and N 2 molecule, respectively. For the tetra-ReN 2 nanosheet, which is a low-energy structure reported in literature, the obtained E coh is −6.447 eV/f.u.…”

“…corresponds to one Re and two N atoms), consistent with previous results. 5 However, the E coh of the BHS-ReN 2 nanosheet is as low as −7.120 eV/f.u., which is much smaller than those of H-ReN 2 (−6.076 eV/f.u. ), T-ReN 2 (−5.608 eV/ f.u.…”

“…Layered transition-metal dinitrides (TMDNs) are the recently discovered two-dimensional (2D) nanosheets, which have been regarded as the cousins of transition-metal dichalcogenides (TMDs). − Because of the lesser valence electrons of N atoms than the S ones, the transition metals will adopt a higher oxidation state in the TMDN system, which leads to different electronic properties from the TMD ones. , In addition to the common MoS 2 -like prismatic and trigonal prismatic (H- and T-phase) structures, the non-MoS 2 -like geometries are also reported in the TMDN nanosheets. − For example, a tetragonal structure (tetra-phase) is proposed for the MoN 2 and ReN 2 nanosheets, which is more stable than the H- and T-phase. , A mixed H- and T-phase structure, that is the M-phase, exists in the group-V TMDNs, which accounts for the semiconducting behavior of the TaN 2 system . These diverse geometrical structures bring versatile electronic and magnetic properties into the TMDN nanosheets, which exhibit a strain-modulated magnetism, , doping-induced half-metallicity, , high capacities for alkali metals, , as well as other peculiar behaviors and applications.…”

“…4−9 For example, a tetragonal structure (tetra-phase) is proposed for the MoN 2 and ReN 2 nanosheets, which is more stable than the H-and Tphase. 4,5 A mixed H-and T-phase structure, that is the Mphase, exists in the group-V TMDNs, which accounts for the semiconducting behavior of the TaN 2 system. 6 These diverse geometrical structures bring versatile electronic and magnetic properties into the TMDN nanosheets, which exhibit a strainmodulated magnetism, 10,11 doping-induced half-metallicity, 4,7 high capacities for alkali metals, 8,12 as well as other peculiar behaviors and applications.…”

“…Following the previous work,5 the cohesive energy (E coh ) of the ReN 2 nanosheet is calculated asE coh = E ReN 2 − E Re − E N 2 ,where E ReN 2 , E Re , and E N 2 are the total energies of the ReN 2 nanosheet, isolated Re atom, and N 2 molecule, respectively.…”