Strategic synthesis of sponge-like structured SiOx@C@CoO multifunctional composites for high-performance and stable lithium-ion batteries

Abstract

Sub-stoichiometric silicon oxide (SiO_x) is regarded as one of the most promising alternatives to silicon for use in lithium-ion batteries because of its high theoretical capacity, low cost, and abundant reserves. However, the practical application of a SiO_x anode is largely limited by the inferior Li⁺ kinetic characteristics and slow electron transport. Herein, we strategically synthesize sponge-structured SiO_x@C@CoO multifunctional composites via spray drying and an electrostatic self-assembly strategy. Ultrathin CoO nanosheets are self-assembled on the surfaces of carbon coated SiO_x particles (SiO_x@C). The novel design can effectively improve the conductivity of SiO_x, shorten the diffusion length and increase surface areas to enhance Li⁺ diffusion; more importantly the sponge-like structure is capable of accommodating the volume change, contributing to an improved and stable electrochemical performance during the charging/discharging processes. Based on theoretical simulations, it was confirmed that SiO_x@C@CoO composites can increase the adsorption energy and reduce the diffusion barrier of Li⁺ compared with SiO_x@C, which enhance the storage capacity and facilitate the Li⁺ diffusion during cycling processes. Consequently, sponge-like structured SiO_x@C@CoO multifunctional composites achieve a reversible specific capacity of up to 1287 mA h g⁻¹ at a current density of 0.1 A g⁻¹, and retain 714 mA h g⁻¹ after 750 cycles at 1 A g⁻¹ with a capacity retention of 98.9%. Remarkably, SiO_x@C@CoO composites show great potential in full lithium-ion batteries. Employing LiNi_0.8Co_0.1Mn_0.1O₂ (NCM 811) as the cathode, the pouch-type cell exhibits an excellent reversible capacity of 206 mA h g⁻¹ and a long-term cycling stability with a capacity retention of 85.9% after 200 cycles.