One-step growth of ultrathin CoSe nanobelts on N-doped MXene nanosheets for dendrite-inhibited and kinetic-accelerated lithium-sulfur chemistry.

The practical application of lithium-sulfur (Li-S) batteries is inhibited by the shuttle effect of lithium polysulfides (LiPSs) and slow polysulfide redox kinetics on the S cathode as well as the uncontrollable growth of dendrites on the Li metal anode. Therefore, both cathode and anode sides must be considered when modifying Li-S batteries. Herein, two-dimensional (2D) ultrathin CoSe nanobelts are in situ grown on 2D N-doped MXene nanosheets (CoSe@N-MXene) via one-step solvothermal process for the first time. Owing to its unique 2D/2D structure, CoSe@N-MXene can be processed to crumpled nanosheets by freeze-drying and flexible and freestanding films by vacuum filtration. These crumpled CoSe@N-MXene nanosheets with abundant active sites and inner spaces can act as S hosts to accelerate polysulfide redox kinetics and suppress the shuttle effect of LiPSs owing to their strong adsorption ability and catalytic conversion effect with LiPSs. Meanwhile, the CoSe@N-MXene film (CoSe@NMF) can act as a current collector to promote uniform Li deposition because it contains lithiophilic CoSe and N sites. Under the systematic effect of CoSe@N-MXene on S cathode and Li metal anode, the electrochemical and safety performance of Li-S batteries are improved. CoSe@NMF also shows excellent storage performances in flexible energy storage devices.