First-principles Studies On Adsorption Of Long-chain Lithium Sulfide Li₂S₆ And Li₂S₈ On ZrO₂ Surface

Lithium-sulfur battery is a better energy storage device,mainly because of its higher material specific capacity and battery theoretical specific energy.And sulfur is an environmentally friendly element,with low cost and non-toxic characteristics.Despite its good potential,the separator in the structure of Li-S batteries cannot well suppress the shuttle of lithium polysulfide in Li-S batteries.In order to solve this problem,modifying the diaphragm is a simple and effective strategy.By modifying the diaphragm,it can not only effectively suppress the shuttle effect,but also the diaphragm material should have electrical conductivity and catalytic activity.Because ZrO₂ system is rich in oxygen vacancies,it is a good solid ion conductor,and it has a strong catalytic effect.Therefore,it is explored to apply it to Li-S battery separators.The catalytic reaction on the surface is relatively complicated.Research from the theoretical calculation point can improve the efficiency of predicting the adsorption and catalysis of ZrO₂ as a Li-S battery separator for lithium polysulfide.Therefore,in this paper,the first-principles calculation method is used to study the lithium polysulfide Li₂S₆ and Li₂S₈ on the surface of the tetragonal t-ZrO₂?010?,the surface of the cubic c-ZrO₂?110?,and the monoclinic m-ZrO₂?-111?The evolution of adsorption configuration,adsorption energy,and electronic structure on the surface to investigate the adsorption strength and catalytic performance of the corresponding surface.The transition metal oxide ZrO₂ with good catalytic performance has obvious adsorption behavior for long lithium sulfur rings?Li₂S₆ and Li₂S₈?.In the process of reducing the shuttle effect,the adsorption strength and dissociation ability are derived from the surface oxygen atom to Li atom bonding and the S-Zr bonding Fermi level between the conduction band and the valence band.From calculating the differential charge density and charge transfer amount Bader to analyzing the PDOS of S-Zr bonding,the Fermi energy level is the influencing factor of adsorption and catalytic strength.The first-principles method was used to calculate the partial wave state density PDOS of the key atom S-Zr in the adsorption configuration.The relationship between the adsorption strength of the long lithium sulfur ring and the Fermi level in PDOS was studied for the three surfaces formed by the three crystal forms of ZrO₂.The results show that the ZrO₂ crystal form can regulate the Fermi level position of the PDOS of S-Zr adsorbed on the surface of the lithium sulfur ring.From the change of Fermi level position,the evolution behavior of Li₂S₆ and Li₂S₈ P-type catalysis on t-ZrO₂ surface to N-type catalysis model on m-ZrO₂ surface was found.The cubic ZrO₂ whose Fermi energy level is between the valence band and the conduction band is a strong adsorption catalytic model.In the stable adsorption configuration,the long lithium sulfur ring adsorbed with single lithium cannot be opened by the ZrO₂ surface.Improper adsorption of O-O bridges in the dimer row of the reconstructed surface with double Li atoms can open the ring,and the long chain is broken to achieve degradation of the lithium sulfur ring.The dimer row O-O bridge dislocations adsorb S and tend to desorb after ring opening and chain breaking.Based on this,a physical model to improve the catalytic performance of lithium-sulfur long rings by adjusting the Fermi energy level was built.