Mechanism and thermal effects of phytic acid-assisted porous carbon sheets for high-performance lithium–sulfur batteries

Abstract

High energy density, stable, and inexpensive electrode materials have the potential to improve the performance of lithium–sulfur (Li–S) batteries. Developing high porosity, high conductivity, and a network framework for multidirectional ion transfer in Li–S batteries, on the other hand, remains a significant challenge. Nitrogen and phosphorus co-doped porous carbon sheets (PCS900) are designed and synthesized here with high porosity and abundant active sites. PCS900 can withstand high sulphur loading while also providing multidirectional ion transport channels. Density functional theory (DFT) calculations indicate that nitrogen and phosphorus co-dopants play an important role in suppressing the shuttle effect via the chemical interaction between sulfur and the carbon framework. At a current density of 1 C, the PCS900/S electrode has an initial specific capacity of 737 mA h g⁻¹, and the average capacity decay rate per 500 cycles is as low as 0.079%. Furthermore, the heat released during the discharging process is greater than the heat released during the charging process due to the combination of in situ XRD and microcalorimetry techniques.