Optimized crystal orientation for enhanced reaction kinetics and reversibility of SnSe/NC hollow nanospheres towards high-rate and long-term lithium/sodium storage

The development of anode materials with high theoretical capacity and cycling stability is very important for the electrochemical performance of lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Herein, SnSe/NC hollow nanospheres with different crystal orientations were prepared by regulating the high-temperature selenization of the PDA@SnO2 precursor for lithium/sodium storage. In SnSe/NC hollow nanospheres, the physical buffering and chemical bonding of the nitrogen carbon matrix and SnSe nanoparticles could inhibit volume expansion and polyselenide loss, thus maintaining long-term structural stability. More importantly, electrochemical tests and DFT calculations show that the diffusion energy barrier of Li+/Na+ is significantly reduced at the SnSe (400) rather than the usual (111) facet, which is conducive to the uniformity of ion insertion into SnSe, thus effectively enhancing the reaction kinetics and reversibility of lithium/sodium storage. Therefore, SnSe/NC hollow nanospheres with rich SnSe (400) and good dispersion formed at 550 °C delivered the best reversible specific capacity and rate performance. After a long period of 900 cycles, the capacity retention of lithium/sodium ion batteries is close to 84.88% and 77.05%, respectively. Our findings provide valuable insights into the design of metal selenides for advanced LIBs/SIBs.