| dc.description.abstract | Many countries are actively developing green energy sources to reduce reliance on fossil fuels and decrease greenhouse gas emissions. Developing large-scale energy storage devices and technologies is essential to utilize these energy sources efficiently. High-energy-density lithium-ion batteries are widely used for this purpose. To further improve the performance of lithium-ion batteries, developing new anode materials is crucial. ZnMn2O4 (ZMO), as a typical ternary transition metal oxide, is known for its abundant and low-cost zinc and manganese resources, non-toxicity, and excellent theoretical capacity (~784 mAh/g). However, its practical application faces challenges due to poor conductivity and significant volume changes during charge-discharge cycles, which can easily lead to particle breakage, resulting in poor rate performance and rapid capacity decay.
In this experiment, we first prepared ZMO nanoparticles through a simple co-precipitation method followed by calcination. Next, we used the sol-gel method to coat titanium dioxide on the ZMO nanoparticles, forming a core-shell structured composite material. The experimental results showed that coating the ZMO particles with an appropriate thickness of titanium dioxide, specifically under the optimal parameter ZMO@TiO2-0.052, successfully mitigated the volumetric expansion effect and provided a rapid diffusion channel for lithium ions. This resulted in a specific capacity of 985.46 mAh/g after 100 charge-discharge cycles at a current density of 100 mA/g. Additionally, the increased oxidation state of Mn enhanced the capacity. The coated ZMO particles exhibited a more significant capacity increase due to the nanometer-sized titanium dioxide with short diffusion paths promoting lithiation, and the improved valence and conduction band structure of titanium dioxide facilitated charge transfer and reduced impedance. Furthermore, the material′s surface formed a reversible organic polymeric/gel-like layer, exhibiting pseudo-capacitance-type behavior. As a result, ZMO@TiO2-0.052 maintained a specific capacity of 500.88 mAh/g at a current density of 1000 mA/g, with a capacity retention rate of 74.0%, showing higher capacity and stability compared to ZMO nanoparticles.
To further enhance the material′s conductivity, we prepared soft carbon anode material from refinery waste pitch through calcination. The core-shell material was then composited with the soft carbon using ball milling. The results indicated that the optimal soft carbon composite ratio, ZMO@TiO2/SC 1:0.25, exhibited a specific capacity of 1171.83 mAh/g after 100 charge-discharge cycles at a current density of 100 mA/g. This suggests that a small amount of soft carbon can effectively provide conductive pathways and further suppress volumetric expansion effects. The porous structure of the soft carbon provided better ion channel conditions and additional lithium storage sites. Additionally, the bond between interfacial oxygen atoms in the carbon material and titanium dioxide enhanced lithium-ion stability, further contributing to pseudo-capacitance-type behavior. Consequently, the optimal parameter maintained a specific capacity of 620.97 mAh/g at a current density of 1000 mA/g, with a capacity retention rate of 79.4%. Compared with other studies using ZMO anode materials, the composite material prepared in this study demonstrated outstanding performance. | en_US |