Boosting lithium storage performance of Co-Sn double hydroxide nanocubes in-situ grown in mesoporous hollow carbon nanospheres

Herein, facile in-situ synthesis of double hydroxide CoSn(OH)₆ nanocubes within mesoporous hollow carbon nanospheres (MHCSs) has been successfully developed through solution impregnation and solid-phase molten reaction, using MHCSs as nanoreactors. Several CoSn(OH)₆ nanocubes with side length of 50∼80 nm are encapsulated in every MHCS with a diameter of 300–400 nm. When CoSn(OH)₆@MHCS is evaluated as an anode material for lithium-ion batteries, it achieves exceptional rate capability (1684 and 626 mAh g⁻¹ at 0.1 and 10 A g⁻¹) and excellent cycle performance (1512 mAh g⁻¹ at 0.2 A g⁻¹ after 140 cycles, 1023 mAh g⁻¹ at 1 A g⁻¹ after 400 cycles, 512 mAh g⁻¹ at 5 A g⁻¹ after 500 cycles). The outstanding electrochemical performance is mainly attributed to the unique “ship-in-a-bottle” encapsulation structure. The mesoporous carbon shells of MHCSs facilitate electrolyte penetration and electron transfer. The large inner cavity of MHCSs promotes full contact between CoSn(OH)₆ with electrolyte, and accommodates free expansion/contraction of CoSn(OH)₆. The semi-enclosed carbon shell prevents the detachment and aggregation of the inner CoSn(OH)₆. These structure merits can remarkably enhance reaction kinetics and structure stability of CoSn(OH)₆. The stable and high-capacity output of the full cell demonstrates the great potential of CoSn(OH)₆@MHCS in practical applications.