Carbon-Coated Silicon Material: an Ideal Anode Material for Lithium Batteries

Problems Facing Silicon Carbon Material System

Silicon possesses an ultra-high theoretical capacity for lithium insertion, which is about ten times greater than carbon materials. It has many advantages, including a low price, abundant sources, and a platform that charges and discharges similar to graphite. Silicon will, however, produce volume changes of >400% during deintercalation. This will lead to pulverization, loss of contact between the current collector, conductive agent and silicon, as well as rapid capacity degradation. The SEI membrane on the silicon surface is also a major factor in limiting its cycle life.
The lithium ions diffuse into the silicon particle, reducing the lithium insertion capability of the active materials. Selecting nano-scale silicon particle can also reduce material powdering. This will improve capacity. Nanoparticles, however, are easily agglomerated, and they have little effect on the thickening SEI films. As of now, silicon anode technologies are primarily focused on solving two key problems: “volume expansion”, and “conductivity”, in the charge and discharge processes. As far as anodes are concerned, the carbon materials used in silicon anodes to form conductive and buffer layer are crucial.

The nanometerization process can enhance the performance of silicon material. To reduce the cost of manufacturing nano-silicon material and to stabilize the SEI film on the surface of silicon materials, a variety of materials with good intrinsic conductivity are used to combine with silicon. Carbon materials, among these materials, can not only increase the conductivity on silicon-based anodes but also stabilize SEI film at the anode’s surface.

Neither silicon nor carbon can satisfy the demands of modern electronics for energy density or cycle life. The fact that carbon is a member of the same chemical group as silicon, and has similar properties to both, makes it easy to recombine them. The composite silicon-carbon can be used to complement both the benefits and shortcomings of each material. It also allows for a material with a significantly increased gram capacity and cycle weight.

Moreover, by reducing the size of the particles in the electrode material it is possible to increase the electronic conductivity rather than the ionic. As the particle size is reduced, the diffusion path of lithium ions is also shortened. This allows the lithium ion to quickly participate in electrochemical reactions, during charge and discharge. For the enhancement of electronic conductivity there are two methods. One involves coatings of conductive material and the second is doping. This is done by producing mixed valence states to improve the intrinsic conductivity.

Carbon-Coated Silicone Material

Scientists developed a plan for using carbon to wrap silicone as a negative electrolyte material in lithium batteries. They did this by synthesizing the electrochemical characteristics of carbon and silica. In experiments, scientists found that silicon coated with carbon can boost the material’s performance. Preparation methods for this material include hydrothermal method CVD, and coating carbon precursors to silicon particles. The array of nanowires were prepared by metal catalytically etching the silicon plate. They then coated the surface with carbon using carbon aerogels. The initial discharge capacity of this nanocomposite was 3,344mAh/g. After 40 cycles, the capacity reversible is 1,326mAh/g. The material’s excellent electrochemical performance is due to its good electronic conductivity, contact between silicon and carbon materials, and effective inhibition of volume expansion by the silicon materials.

The Development Prospects

Carbon-coated Silicon material combines high conductivity, stability and silicon’s advantages with high capacity. It is an ideal material for lithium batteries anodes.

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