Complexation-assisted polymerization for the synthesis of functional silicon oxycarbonitride with well-dispersed ultrafine CoS as high- performance anode for lithium-ion batteries

The silicon oxycarbonitride with ultrafine CoS (CoS@SiOCN) spherical composite as anode material for li-thium-ion batteries is synthesized through the pyrolysis of the polymerized product of Co(II) with Schiff-base ligand of aminoethyl-aminopropyl-trimethoxy silane and salicylaldehyde and the simultaneous in-situ formation of CoS. Owing to the molecular level complexation of Co(II) and the subsequent in-situ sulfida-tion, the generated ultrafine CoS is well-dispersed in SiOCN sphere. Compared with the Co@SiOCN and SiOCN anodes, the CoS@SiOCN anode displays the highest initial reversible capacity of 834 mAh g-1 with an initial Coulombic efficiency of 68.5% at 200 mA g-1. At 1000 mA g-1, the CoS@SiOCN anode still exhibits outstanding cycling performance, delivering a reversible capacity of 536 mAh g-1 after 800 cycles with a retention of 80.4%. The full cell with pre-lithiated CoS@SiOCN anode and LiFePO4 cathode delivers an initial discharge capacity of 146 mAh g-1 at 0.2 C and maintains 115 mAh g-1 at 0.5 C after 50 cycles. The out-standing electrochemical performances can be attributed to the structure of SiOCN with the active SiOxC4-x (0 <= x <= 4) nanodomain and free carbon conductive network, and well-dispersed CoS. The electrochemical analysis indicates both CoS and in-situ formed Co nanoparticles at the high redox voltage can contribute to the electrochemical properties.(c) 2023 Published by Elsevier B.V.

Automated summary

A spherical composite of silicon oxycarbonitride with ultrafine CoS (CoS@SiOCN) is synthesized as an anode material for lithium-ion batteries. The in-situ formation of well-dispersed CoS particles is achieved through the pyrolysis of a polymerized product of Co(II) with a Schiff-base ligand. Compared to other anodes, the CoS@SiOCN anode exhibits superior cyclic performance and a high initial reversible capacity, attributed to its unique structure and well-dispersed CoS particles. The electrochemical analysis indicates that both CoS and in-situ formed Co nanoparticles contribute to the electrochemical properties.