Multifunctional Electrocatalytic Cathodes Derived from Metal Organic Frameworks for Advanced Lithium‐Sulfur Batteries

The rechargeable lithium-sulfur (Li-S) battery is a promising candidate for the next-generation of energy storage technology, owing to the high theoretical capacity, high specific energy density, and low cost of electrode materials. The main drawbacks of developing long-life Li-S batteries are capacity fading and the kinetic sluggishness at the cathode caused by the polysulfides shuttle. To address these limitations, we have designed novel nanocages containing cobalt phosphide (CoP) nanoparticles embedded in highly porous nitrogen-doped carbon (CoP-N-GC) by thermal annealing of ZIF-67 in a reductive atmosphere followed by a phosphidation step using sodium hypophosphite. The large surface area and the uniform homogeneous distribution of CoP nanoparticles within the N-doped nanocages graphitic carbon act as electrocatalysts to suppress the shuttle of soluble polysulfides through strong chemical interactions, while catalyzing the sulfur redox. As a result, the S@CoP-N-GC electrode delivers an extremely high specific capacity of 1410 mA h g -1 at 0.1 C (1C = 1675 mA g -1 ) with an excellent coulombic efficiency of 99.7%. Moreover, capacity retention from 864 to 678 mA h g -1 was obtained after 460 cycles with a very low decay rate of 0.046% per cycle at 0.5 C. Therefore, the combination of CoP catalyst and polar conductive porous carbon effectively stabilizes the sulfur cathode, enhancing the electrochemical performance and stability of the battery.