Ultrafine Sn nanoparticles embedded in shell of N-doped hollow carbon spheres as high rate anode for lithium-ion batteries

Highlights: • Dynamic covalent bond in polymeric nanoparticles is used to induce hollow Sn⁴⁺-MOPs. • Ultrafine Sn nanoparticles uniformly embedded in shell of N-doped hollow carbon spheres is successfully synthesized by pyrolysis of the Sn⁴⁺-MOPs precursor. • The composite exhibits superior cycle stability and rate capacity. - Abstract: A novel reversible interaction in polymeric nanoparticles is used to induce hollow Sn⁴⁺-MOPs. Then ultrafine Sn nanoparticles uniformly embedded in shell of N-doped hollow carbon spheres is successfully synthesized by pyrolysis of the Sn⁴⁺-MOPs precursor. In this architecture, the N-doped carbon shells can effectively avoid the direct exposure of embedded Sn nanoparticles to the electrolyte and efficiently accommodate the volume change of Sn nanoparticles. Furthermore, the hollow structure of carbon sphere can prevent Sn nanoparticles aggregation over repeated cycling and shorten the diffusion path of both electrons and ions. As a consequence, this N-doped hollow Sn/C anode delivers a reversible capacity of 606 mA h g⁻¹ at a current density of 0.2 A g⁻¹ after 250 cycles and a reversible capacity of 221 mA h g⁻¹ even at a much higher current density of 10 A g⁻¹, which are much better than those of pure Sn nanoparticles. The desirable cyclic stability and rate capability were attributed to the unique architecture that provided fast pathway for electron transport and simultaneously solved the major issues of Sn-based anodes, such as pulverization, aggregation and loss of electrical contact.