One-step growth of ultrathin CoSe2 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 2 nanobelts are in situ grown on 2D N-doped MXene nanosheets (CoSe 2 @N-MXene) via one-step solvothermal process for the first time. Owing to its unique 2D/2D structure, CoSe 2 @N-MXene can be processed to crumpled nanosheets by freeze-drying and flexible and freestanding films by vacuum filtration. These crumpled CoSe 2 @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 2 @N-MXene film (CoSe 2 @NMF) can act as a current collector to promote uniform Li deposition because it contains lithiophilic CoSe 2 and N sites. Under the systematic effect of CoSe 2 @N-MXene on S cathode and Li metal anode, the electrochemical and safety performance of Li–S batteries are improved. CoSe 2 @NMF also shows excellent storage performances in flexible energy storage devices.