involved, and affordable cost. [1][2][3] However, the commercial application of the sulfur cathode for the Li-S batteries is restrained by several technical barriers [4][5][6] compared with Li-ion battery. [7] First, the poor conductivity of sulfur and its reaction intermediates limit the sulfur utilization, [8] which leads to decreased energy density and power density. Second, during the charge/discharge process, there is a large volume change, resulting in rapid deterioration of the electrode structure. Various strategies have been investigated to increase electrode conductivity and to accommodate the volume expansion. [9][10][11] Last but not least, the dissolution and transport of lithium polysulfides (LiPSs) in the electrolyte result in the fatal "shuttle effect" that causes the deposition of Li 2 S on Li anode and then degrades the cycle performance. This shuttle effect could be mitigated by 1) trapping/confining the soluble LiPSs in the cathode by physical and chemical adsorption, [12][13][14][15] which prevents the transport of soluble LiPSs in the electrolyte, and 2) enhancing the kinetics of LiPS conversion reactions so that the soluble long-chain LiPS could transform to insoluble short-chain LiPS quickly, limiting the lifetime of soluble LiPS. [16,17] Therefore, a superior Li-S battery could be achieved by designing a cathode with high electricalThe lithium-sulfur (Li-S) battery is widely regarded as a promising energy storage device due to its low price and the high earth-abundance of the materials employed. However, the shuttle effect of lithium polysulfides (LiPSs) and sluggish redox conversion result in inefficient sulfur utilization, low power density, and rapid electrode deterioration. Herein, these challenges are addressed with two strategies 1) increasing LiPS conversion kinetics through catalysis, and 2) alleviating the shuttle effect by enhanced trapping and adsorption of LiPSs. These improvements are achieved by constructing double-shelled hollow nanocages decorated with a cobalt nitride catalyst. The N-doped hollow inner carbon shell not only serves as a physiochemical absorber for LiPSs, but also improves the electrical conductivity of the electrode; significantly suppressing shuttle effect. Cobalt nitride (Co 4 N) nanoparticles, embedded in nitrogen-doped carbon in the outer shell, catalyze the conversion of LiPSs, leading to decreased polarization and fast kinetics during cycling. Theoretical study of the Li intercalation energetics confirms the improved catalytic activity of the Co 4 N compared to metallic Co catalyst. Altogether, the electrode shows large reversible capacity (1242 mAh g −1 at 0.1 C), robust stability (capacity retention of 658 mAh g −1 at 5 C after 400 cycles), and superior cycling stability at high sulfur loading (4.5 mg cm −2 ).

Wide bandgap (E g ) mixed-halide perovskite has attracted much attention for applications in photovoltaic devices. However, devices featuring this type of perovskite are often subject to a large voltage deficit due to the occurrence of phase segregation, which limits the relevant devices' access to high performances. Here, the correlation of the phase segregation and voltage losses for wide-E g mixed-halide perovskite solar cells (PSCs) is clarified by experiments and simulations. Taking 1.67 eV E g mixed-halide perovskite as an example, it is confirmed experimentally that the control devices produce a poor physical morphology, a locally widened E g , and an inferior electrical response. By suppressing the phase segregation, the open-circuit voltage (V oc ) can be boosted from 1.15 to 1.20 V, which is a high value for the 1.67 eV E g mixed-halide PSCs. An electrical simulation of phase segregation reveals that the performance degeneration can be attributed to the bulk recombination due to the energy level mismatch of the varied E g s. Moreover, a theoretical perspective is produced to expatiate on the strategies for the high V oc of wide-E g PSCs. This study brings deep guidance to unlock the potential for high-performance mix-halide PSCs.