A novel β -sic nanoparticle based anode material can be used for lithium ion batteries

Lithium ion batteries (LIB) have become the cornerstone of portable electronics, electric vehicles and alternative energy economy due to their long life, good storage performance, high energy density and high operating voltage.  Improving the electrode material is the most important and feasible method to improve the electrochemical performance of LIB.  At present, the research of electrode materials has gone beyond the traditional carbon - based ink anode to transition metal oxides, tin and silicon - based materials.  Silicon is the second most abundant element in the earth's crust after oxygen.  Due to its electronic properties, especially its high capacity, this promising cathode material has attracted much attention.  However, the volume of this material changes greatly during operation, which affects its stability, structural integrity and electrical properties, resulting in particle breakage or collector spalling during charging and discharging.  These problems have prevented silicon-based materials from entering the commercial lithium-ion battery industry.  

Silicon carbide nanoparticles' study  

According to foreign media reports, in order to solve these problems,  Ravi Nandan, a researcher at the Japan Advanced Institute of Science and Technology, Noriyuki Takamori, a doctoral student, and Koichi, a technologist  Higashimine, senior lecturer Rajashekar Badam and Professor Noriyoshi Matsumi, looked to sphalerite for inspiration.  The team came up with a complex, instrumentless and novel strategy to produce unique sphalerite silicon carbide nanoparticles at relatively low temperatures.  

Three-dimensional intermetallic compound structures in sphalerite systems can easily accommodate lithium ions in their interstitial positions.  As lithium ions travel between the main materials, the structure changes in volume very little, resulting in better life and reversibility.  The silicon based counterpart of sphalerite type materials is β -silicon carbide (SiC).  Some previous studies have reported techniques for synthesizing β -sic composites as anode materials, but most of them involved complex procedures and instruments.  

The team designed a two-step synthesis process to produce β -sic based anode materials for use in lithium-ion batteries.  The first step is to form silicon nanoparticles in the polydopamine matrix.  The second step is to convert nitrogen-doped carbon substrates into special variants of β -sic nanoparticles.  Interestingly, this conversion process requires a much lower temperature than traditional methods, as low as 600 degrees Celsius.  

The obtained materials are then used in the negative half cell configuration and electrochemical screening is performed.  The results show that the battery has high current density, rated capacity and good reversible lithium ion storage compatibility.  In addition, it also shows a high capacity retention rate, maintaining about 94% of its capacity after 300 charge-discharge cycles and maintaining a discharge capacity of 1195 MahG-1.  

This synthetic material can be used successfully as a negative electrode, and when combined with the commercial LiCoO2 positive electrode, the full cell formed in this way demonstrates the great potential for β -sic applications in commercial LiB systems.  The simple preparation technique proposed in this study opens the door to many β -sic and LiB studies.  Professor Matsumi concluded: "Global carbon emissions are increasing due to the use of fossil fuels in transportation.  The β -sic anode material is manufactured in a low-cost way that could be used to develop high energy density batteries to drive a cleaner, greener electric vehicle industry.  In fact, its application is expected to expand to other delivery vehicles such as trains, planes and ships."