The introduction of metallic Cu onto mixed-phase TiO2 to realize in-situ capture, conversion, and reuse of lithium polysulfides for Li-S batteries

The Li-S batteries possessing high theoretical energy density are promising for next-generation energy storage. However, the shuttle effect and slow conversion of lithium polysulfides seriously hinder the practical application. In this contribution, introducing metallic Cu to modify dual-phase TiO2 (rutile/anatase) grown on N-doped carbon nanosheets (denoted as Cu/mTiO2-NC) can act as a buffer layer to confine the active S species in the cathode region effectively. The corresponding systematic experiments show that the Cu/mTiO2-NC provides sufficient surface affinity to adsorb and capture polysulfides and has a highly conductive C/N skeleton to achieve rapid electron migration. Moreover, the metallic Cu can react with polysulfides to further immobilize poly-sulfides. Thus, the Li-S batteries, with the aid of optimal Cu/mTiO2-NC, exhibit a desirable discharge capacity of 811 mA h g-1 after 100 cycles at 0.2 C, which is 50 % higher than that without Cu/mTiO2-NC. Moreover, the optimum Li-S batteries deliver a discharge capacity of 435.45 mA h g-1 after 600 cycles at 0.5 C, corresponding to attenuation per cycle of only 0.09 %.