Evolution of Discharge Products on Carbon Nanotube Cathodes in Li–O₂ Batteries Unraveled by Molecular Dynamics and Density Functional Theory

Abstract

The performance of Li–O2 batteries (LOBs), such as capacity and overpotential, is closely related to the morphology of the discharge product. Here, the relationship between the growth behavior of Li2O2 on the surface of the carbon nanotube (CNT) cathodes and the cycle performance of LOBs was innovatively revealed based on molecular dynamics (MD) and density functional theory (DFT). Our results demonstrated that the growth of (Li2O2) n on the CNT surface mainly undergoes three stages: adhesion, branching, and connection. The stable gap between (Li2O2) n and the CNT surface was determined to be approximately 2.47 Å. Interestingly, the dense deposition thickness is positively correlated with the number of Li2O2 monomers. In addition, the formation of free Li2O2 directly induces the instability of (Li2O2) n and capacity loss. Moreover, armchair-type CNTs with larger diameters, especially single-walled CNTs and multi-walled CNTs with an odd number of tube walls were found to be more conducive to the stable growth of discharge products. Notably, (Li2O2) n is mainly composed of internal stable parts with low conductivity and amorphous components distributed on the surface with p-type semiconductor characteristics. Therefore, the regulation of the CNT structure and the preparation of catalysts to promote the conversion of Li2O2 from an ordered state to an amorphous structure play a vital role in breaking the technical bottleneck of LOBs. Our results identify the long-term controversial evolution mechanism of the product morphology, and the unique calculation ideas are also applicable to the intuitive exploration of the microscopic growth behavior of discharge products in other metal–air batteries.

Defect‐Engineered ZIF‐Derived Non‐Pt Cathode Catalyst at 1.5 mg cm−2 Loading for Proton Exchange Membrane Fuel Cells

“…[ 22 ] The radial distribution function (RDF) of O 2 C and H 3 O + C were utilized to analyze the probability of an object surrounding a target object in a specific space, reflecting the distance and interaction between atoms. [ 32 ] For O 2 C (Figure 4i), a weak peak emerges at 4.07 Å for a 4 nm pore, which can be attributed to Coulomb forces and van der Waals interactions between oxygen and carbon atoms. With the decrease of pore diameter, the RDF peak positions gradually shift left and with higher intensity.…”

“…With the decrease of pore diameter, the RDF peak positions gradually shift left and with higher intensity. It is noteworthy that when the pore diameter decreases to 0.5 nm, another peak at 3.17 Å can be observed, indicating the strong interaction between molecular oxygen and carbon pore surface, [ 32 ] which may be the main reason for the attenuation of oxygen mass transport rate. This tendency is apparent for H 3 O + ‒C RDF curves in Figure 4j.…”

Fascinating Bifunctional Electrocatalytic Activity via a Mesoporous Structured FeMnO3@ZrO2 Matrix as an Efficient Cathode for Li–O2 Batteries

“…Notably, the comparative area and intensity of the signal for the OH − ions were greater than those of the perovskite lattice, potentially advantageous for enhancing the catalytic performance for the ORR/OER. 41,42 Two distinct peaks for Zr 3d 5/2 at 181.4 eV and Zr 3d 3/2 at 183.5 eV, derived from Zr 4+ in an oxide form, were present in the Zr 3d spectrum (Figure 3f). The C 1s spectrum (Figure S6b) featured three resolved peaks, with C−C bonds being responsible for the single peak at 282.7 eV and C�O and C− O bonds being represented by two minor peaks (at 284.4 and 283.5 eV, respectively) that were deconvoluted.…”

Metal sulfide heterojunction with tunable interfacial electronic structure as an efficient catalyst for lithium-oxygen batteries

“…This result is due to the large adsorption energy of CuCo 2 S 4 /CoS 1.097 toward the reaction intermediates. The formation of membrane-like products is beneficial to charge conduction and reaction kinetics [58,59]. The porous structure of the CuCo 2 S 4 /CoS 1.097 electrode was retained after discharging, and it had a positive effect on the transport of electrolytes and oxygen for further reactions [60].…”