Facile synthesis of multi-phase (Si+SiO2)@C anode materials for lithium-ion batteries.

To bring about a revolution in energy storage through Li-ion batteries, it is crucial to develop a scalable preparation method for Si-based composite anodes. However, the severe volume expansion and poor ionic transport properties of Si-based composites present significant challenges. Previous research focused on SiO and nano Si/C composites to address these issues. In this study, mechanical milling was used to introduce a SiOx layer onto the surface of Si by mixing Si and SiO2 in a 1 : 1 mass ratio. The resulting Si+SiO2 composites (denoted as SS50) exhibited an initial coulombic efficiency (ICE) of 73.5% and high rate performance. To further stabilize the overall structure, kerosene was introduced as a carbon source precursor to generate a coating layer. The resulting multiphase composite structure (SiOx+SiO2+C), designated as SS50-900C, demonstrated a capacity retention of 79.5% over 280 cycles at its capacity of 487 mA h g-1. These results suggest that a cost-effective mechanical ball milling refinement of Si+SiO2 and a gas-phase encapsulation process can significantly improve the electrochemical performance of Si-based composites.

Improvement of stability and capacity of Co-free, Li-rich layered oxide Li1.2Ni0.2Mn0.6O2 cathode material through defect control.

Layered oxides based on manganese (Mn), rich in lithium (Li), and free of cobalt (Co) are the most promising cathode candidates used for lithium-ion batteries due to their high capacity, high voltage and low cost. These types of material can be written as xLi2MnO3·(1 - x) LiTMO2 (TM = Ni,Mn,etc.). Though, Li2MnO3 is known to have poor cycling stability and low capacity, which hinder its industrial application commercially. In this work, Li1.2Ni0.2Mn0.6O2 materials with different amounts of structural defects was successfully synthesized using powder metallurgy followed by different cooling processes in order to improve its electrochemical properties. Microstructural analyses and electrochemical measurements were carried out on the study samples synthesized by a combination of X-ray diffraction, transmission electron microscopy, and cyclic voltammetry. It is found that the disorder of the transition metal layer in Li2MnO3 promotes its electrochemical activity, whereas the Li/Ni antisites of the Li layer maintain the stability of its local structure. The material with optimal amount of structural defects had an initial capacity of 188.2 mAh g-1, while maintaining an excellent specific capacity of 144.2 mAh g-1 after 500 cycles at 1C. In comparison, Li1.2Ni0.2Mn0.6O2 without structural defect only gives a capacity of 40.8 mAh g-1 after cycling. This microstructural control strategy provides a simple and effective route to develop high-performance Co-free, Li-rich Mn-based cathode materials and scale-up manufacturing.