A Case Study: Li/S Battery Characterization in Argonne National Laboratories Post-Test Facility and Center for Nanoscale Materials

Lithium ion batteries are an important energy source with wide scale applications due to their high energy and power densities. As the application of Li-ion batteries has advanced to their use in electric vehicles and grid energy storage, the demand for increased performance has led to research into higher capacity anodes and cathodes. Recent effort has focused on the development of Li₂S cathodes because of the low cost and high theoretical capacity (1675 mAh/g) of sulfur. One of the advantages of a Li₂S cathode is the ability to pair with safer anode materials rather than Li metal, however, a major limitation to practical application is the formation of soluble lithium polysulfides which leads to rapid capacity fade and high self-discharge. In order to circumvent these problems, attempts at encapsulating Li₂S particles with conductive carbon have been made with some success.

In this study, to understand the effect of the carbon shell, a Li/S battery consisting of a Li₂S cathode with particles encapsulated with nitrogen-doped carbon, and a Li-metal anode was characterized at Argonne’s battery Post-Test Facility and the Center for Nanoscale Materials.              The coated particles were prepared by ball milling carbon black with Li₂S particles followed by stirring with pyrrole and subsequent carbonization in an autoclave.  Cells made with the coated Li₂S particles exhibited higher capacity with prolonged cycling than uncoated cells. The improved performance is attributed to the presence of the N-doped carbon coating on the Li₂S particles.

The cycled cells were subsequently opened in the Post-Test Facility glovebox. The anode and cathode were analyzed using HPLC, optical microscopy, and SEM/EDS. TEM and EFTEM of the Li₂S particles was performed at the Center for Nanoscale Materials using a special air-tight sample holder.  The sample was placed in the holder that was in an Ar-filled glovebox and then transferred into the TEM.

Argonne’s unique Post-test Facility has two large connected argon-filled glove boxes with water and oxygen concentrations held below 1 ppm.  One glove box is used for the dismantling of cells, both large and small, and the subsequent sample preparation for analysis. Samples are transferred to the second customized glove box (via an air-lock) for XPS, Raman, FTIR and TGA-MS analysis. Samples for HPLC-MS, GCMS, SEM and optical microscopy are removed from the glove box in containment and analyzed in appropriately modified instrumentation. Argonne’s Center for Nanoscale Materials user facility was used for EFTEM imaging, using an air-tight sample holder and Raman with multiple laser sources. Through these facilities we were able to systematically characterize cells at a multi-scale level.

This work was performed under the auspices of the DOE Office of Vehicle Technologies, Hybrid and Electric Systems, under Contract No. DE-AC02-06CH11357. 

 

Use of the Center for Nanoscale Materials was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory ("Argonne"). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.

 

 

* Argonne National Laboratory, Argonne, IL

** Illinois Institute of Technology, Chicago, IL