How graphene material improve the Li-ion performance
Organic compound materials are more and more widely used, and are also widely used in lithium batteries middle. The positive electrode material of lithium battery is generally metal oxide, and the negative electrode adopts organic compound material, which can greatly affect the performance of lithium battery. Carbon is one of the elements with the most compound forms in nature, and the hybrid forms of carbon atoms are various, which can form different carbon materials. The negative electrode material of lithium battery is generally dominated by graphite material, and graphene is a material composed of carbon atoms, and its performance is very outstanding. The interior of the graphene material is composed of multi-layer graphite single atomic layers, and each atomic layer forms a compound structure in the form of a hybrid orbital, that is, each carbon atom has an electron in the orbital that has not reached a saturated bond, so as to interact with the adjacent orbital. Unsaturated electrons combine. Graphene is not only a currently known material with high strength, but also the electron carrier in it conforms to the Hall effective, which can change the chemical potential energy through the action of an electric field. Therefore, graphene plays an important role in improving the performance of lithium batteries.
Fig 1. Schematic diagram of the structure of grapheme
Fig 2. SEM of graphene
Application of Graphene in Anode Materials
The negative electrode of lithium-ion battery is mainly used as the main body of lithium storage, which plays a decisive role in the performance of the battery. Usually, the advantages and disadvantages of negative electrode materials are judged by judging whether they have good lithium ion transport channels and electron transport channels. Graphene has both the ability to provide good ability of good electron transport channels and excellent lithium ion transport properties. Graphene not only has excellent electrical conductivity, but also the interlayer spacing of graphene is extremely small, only in the order of micro and nanometers, which makes the diffusion path of lithium ions short; the combination of graphene and lithium ions is in the entire outer surface of graphene. Surface simultaneously, thus improving transfer performance.
Application of Graphene in cathode materials
The energy density of a lithium-ion battery is determined by the energy density of the positive electrode material, so the positive electrode material is a very critical part of each component unit of a lithium-ion battery. The current research shows that the composite cathode material formed by graphene and LiFePO4, LiNi1/3Co1/3Mn1/3O2 and LiMn2O4 can improve the electrochemical performance of the material. Olivine-type LiFePO4 is a widely used cathode material for lithium-ion batteries with a theoretical specific capacity of 170mAh/g, but its application at high rates is limited due to low electronic conductivity and lithium ion diffusion. After compounding it with graphene, graphene fully wraps the surface of LiFePO4, and uses the tough network conductive structure in graphene to maintain the conductivity, thereby improving the conductivity of the entire material.