Surface engineered polar CeO2-based cathode host materials for immobilizing lithium polysulfides in High-performance Li-S batteries

Abstract

The particle morphology of CeO2 nanocrystals with different exposed crystal facets is a crucial factor influencing the surface-related materials performance. In this report, shape-controlled synthesis of CeO2 nanocrystals with various preferentially exposed crystal facets (CeO2 nanorods with (110)/(100)/(111), CeO2 nanocubes with (100) and CeO2 nanoctahedra with (111)) was conducted aiming to investigate the crystal plane effect of polar CeO2 as a cathode host on the immobilization of lithium polysulfides and electrochemical performance of the assembled Li-S batteries. The strong chemical bonding between lithium polysulfides and CeO2 host, including Ce-S and Li-O bonds formed on the exposed (110)/(100) and defected (111) crystal facets of CeO2 nanorods during reversible electrochemical conversion from soluble long-chain polysulfides to insoluble short-chain Li2S/Li2S2, results in superb diffusion restriction of lithium polysulfides towards Li anode and endows CeO2 nanorods@CC electrode with a superior electrochemical property among three tested electrodes of CeO2 nanorods@carbon cloth (CC), CeO2 nanocubes@CC, and CeO2 nanoctahedra@CC. However, such strong chemical interaction against polysulfides was not observed by CeO2 nanocubes with preferentially exposed (100) crystal planes and CeO2 nanoctahedra with preferentially exposed (111) crystal planes. In addition to the factor of the exposed crystal planes, CeO2 nanorods possess defect-rich surfaces (i.e., oxygen vacancies and Ce3+) also serving as possible polysulfides anchoring sites, which can contribute to effective immobilization of lithium polysulfides. Benefiting from the above-mentioned advantages, CeO2 nanorods are considered as an outstanding candidate of cathode host materials for long life and high-performance Li-S batteries.