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

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 (11 0)/(1 0 0)/(1 1 1), CeO2 nanocubes with (100) and CeO2 nanoctahedra with (1 1 1)) 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 CeS and Li-O bonds formed on the exposed (11 0)/(1 0 0) 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 (1 1 1) 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.