BN (boron nitride) nanosheets exhibit a number of advantageous properties in the context of a lithium ion polysulfide battery. These include favorable chemical stability, high specific capacity, adsorption of polysulfide species, and ability to act as an insulator. It is therefore expected that a BN-modified separator can improve the performance of the overall system.
One such application is the use of a BN-modified separator to prevent crossover to metallic lithium. The polar nature of BN nanosheets can reduce the likelihood of soluble polysulfides diffusing across the membrane. Additionally, the BN-modified separator allows for strong adsorption of polysulfide molecules. In addition, its large surface area allows for effective adsorption of polysulfide molecular weights. This makes the BN-modified separator a promising solution for improving the electrochemical performance of a LiPS battery.
To achieve this, a commercial grade boron nitride was synthesized, subjected to liquid phase exfoliation, and then re-exfoliated. This produced a large scale of nanosheets. A surfactant was added to disperse the nanosheets within a liquid medium. This allowed for a systematic study of the effect of the BN-modified separator on the adsorption of the polysulfide.
As a result, a two-compartment H-cell was constructed to visualize the interaction between the BN nanosheets and the corresponding polysulfide species. Furthermore, a XAS was used to measure the x-ray absorption spectroscopy of the corresponding boron nitride nanosheets. Interestingly, the XAS study indicated that the adsorption of a boron nitride nanosheet had a large effect on the spectral analysis.