Multifunctional Ni-doped CoSe2 nanoparticles decorated bilayer carbon structures for polysulfide conversion and dendrite-free lithium toward high-performance Li-S full cell

The commercial application of lithium-sulfur batteries is severely hampered by polysulfide shuttle effects, sluggish redox kinetics, and uncontrollable lithium dendrite growth. Herein, a unique Ni-doped CoSe2 nanoparticle decorated bilayer carbon (Ni-CoSe2/BC) structure is synthesized for both the sulfur cathode and lithium anode, which introduces bi-functionalities including Ⅰ) the internal carbon conductive network skeleton of carbon nanotubes is capable of physically confining, storing, and alleviating volume expansion of sulfur; and Ⅱ) Ni-CoSe2 nanoparticles decorated on the external carbon nanoarrays contribute to efficient chemical anchoring and accelerated polysulfide conversion for the cathode, and serve as lithiophilic sites to induce homogeneous lithium deposition for the anode. As a result, Ni-CoSe2/BC effectively inhibits the shuttle effect and induces dendrite-free lithium deposition. The Ni-CoSe2/BC-S delivers a high discharge specific capacity of 806 mAh g−1 after 400 cycles at 1 C, with a low capacity decay rate of 0.07% per cycle. Moreover, the Ni-CoSe2/BC-Li exhibits an impressively long cycle life of 2000 h at 10 mA cm−2/10 mAh cm−2. Notably, the lithium-sulfur full cell assembled with Ni-CoSe2/BC as universal hosts for both anode and cathode possesses an average discharge capacity of 6.07 mAh cm−2 in 50 cycles (Sulfur loading=12.8 mg cm−2, Electrolyte/Sulfur=7.8 μL mg−1, and Negative/Positive=1.56). This work provides novel structural design and mechanism insights for the practical application of lithium-sulfur batteries.