Cobalt-doped tin disulfide catalysts for high-capacity lithium-air batteries with high lifetime.

Dual electrolyte lithium-air batteries have received widespread attention for their ultra-high energy density. However, the low internal redox efficiency of these batteries results in a relatively short operating life. SnS2 is widely used in Li-S batteries, Li-ion batteries, photocatalysis, and other fields due to the high discharge capacity in batteries. However, SnS2 suffers from low electrical conductivity and slow redox kinetics. In this study, Co-doped SnS2 is prepared by hydrothermal method for application in dual-electrolyte lithium-air batteries to study its electrochemical performance and its catalytic reaction process by DFT theory. Conductivity tests show that the Co doping enhances the electrical conductivity of the material and high transmission electron microscopy (HRTEM) results demonstrate that the Co doping of SnS2 increases the grain plane spacing and the material indicates that defects are created on the surface of the material, which is more beneficial to the electrochemical performance of the cell. Co-doped SnS2 exhibits excellent good cycling stability and high discharge capacity in a dual electrolyte lithium-air battery, maintaining a 0.7 V overpotential for 120 h at a current density of 0.1 mA cm-2, with a cell life of over 500 h and an initial discharge capacity showing excellent results up to 16 065 mA h g-1. In addition, this study explores the catalytic activity of Co-doped SnS2 based on density flooding theory (DFT). The results show that Co atoms have a synergistic effect with Sn atoms to perturb the lattice parameters. The calculations show that the catalytic activity is enhanced with the increasing of Co doping content and 3Co-Sn exhibits minimal overpotential.

Analysis of the Discharge Termination Mechanism of a Nonaqueous Li-O2 Battery Based on a Digital Reconstruction Model.

The service life of the lithium-oxygen (Li-O2) battery is an essential factor in measuring the performance of the battery, and it is also imperative to clarify the reason for battery termination. In this work, the positive electrode of a nonaqueous Li-O2 battery was selected after cutoff under different discharge conditions, and the digital reconstruction model of the positive electrode was carried out by X-CT technology. The reconstructed positive electrode's structural characteristics, material transport characteristics, and electrical conductivity were analyzed. It is found that the positive electrode has an apparent expansion phenomenon after constant capacity cyclic charge and discharge, but this situation is not evident after deep discharge. After the constant capacity test is cut off, the product distribution range in the positive electrode is more comprehensive and the material transport efficiency is higher. However, after deep discharge, the product distribution in the positive electrode is more concentrated and the material transport efficiency is lower. There are apparent differences in the termination mechanism between constant capacity cycle discharge and deep discharge. This paper provides a compelling theoretical basis for revealing the discharge termination mechanism of nonaqueous Li-O2 batteries.