A Promising Anchoring Material for Lithium-sulfur Batteries

20 May 2022

 

Further advances in rechargeable batteries are essential to meet the demand for electric vehicles and energy storage. A novel two-dimensional (2D) material may be the solution to mitigating the so-called ‘shuttle effect’ in lithium-sulfur battery technology. 

 

As renewable energy production technologies improve and shrink, and electric vehicles become more popular, the demand for portable energy storage is increasing.

 

Currently, lithium-ion batteries are the standard, but energy density and cost must continually improve to achieve the levels of deployment needed for the most ambitious sustainability targets. Alkali metal-sulfur batteries, a type of lithium-ion battery, have emerged as a promising option, especially in applications requiring high energy storage capacity. However, one issue with metal-sulfur batteries is the so-called ‘shuttle effect’: metal particles called polysulphides dissolve into the battery’s electrolyte and are transported from the sulfur cathode to the metal anode. This reduces capacity and charging performance of the battery.

 

Finding a way to suppress the shuttle effect is crucial to metal-sulfur battery performance and lifetime. Khalifa University’s Hiba Al-Jayyousi, Master’s student, Department of Mechanical Engineering, Dr. Nirpendra Singh, and Dr. Muhammad Sajjad, both Department of Physics, and Prof. Kin Liao, Department of Aerospace Engineering investigated the use of 2D biphenylene sheet as a material to ‘anchor’ the metal particles and prevent them from shuttling. Their results were published in Scientific Reports.

 

“Over the last three decades, lithium-ion rechargeable batteries have gained vast popularity due to their low self-discharge, ample energy storage, stable cycling performance, higher theoretical capacity and specific energy density, which directly affects the development of energy storage technologies,” Dr. Singh said. “Li-ion batteries are environmentally-friendly and suitable for portable electronics, as they offer much higher energy density than other rechargeable systems.”

 

Although lithium sulfur batteries have high theoretical capacity and energy density, the shuttle effect seriously hinders this technology’s development. The research team found that trapping lithium polysulfides on a biphenylene sheet effectively suppresses the shuttle effect and enhances the cycling stability of Li-S batteries. The biphenylene is a newly synthesized two-dimensional material, where the carbon atoms are arranged in a square, hexagonal, and octagonal rings. Compared with other reported two-dimensional materials such as graphene and phosphorene, the biphenylene sheet used by the research team exhibited higher binding energies with the polysulfides.

 

A suitable anchoring material should have excellent conductivity, high surface area, porous structure, and high binding energy with the polysulfides to prevent them from dissolving into electrolytes. Several 2D materials have been proposed and investigated, including holey graphene and nonpolar polyaniline previously investigated by Dr. Singh.

 

“Our study shows that the biphenylene sheet is an excellent anchoring material for lithium-sulfur batteries for suppressing the shuttle effect because of its superior conductivity, porosity, and strong anchoring ability,” Al-Jayyousi said.

 

As energy consumption continues to rise, finding new materials that can make renewable energy generation and storage cleaner and more efficient will be key to meeting the world’s growing energy demands sustainably. 

 

Jade Sterling
Science Writer
20 May 2022