Abstract: The development trend of lithium-ion batteries is outlined, the current status of theoretical research on the charging and discharging mechanism of lithium-ion batteries is briefly introduced, and the existing preparation theory and the latest development trend of positive and negative electrodes are summarized. Various preparation methods and development prospects of positive and negative electrode materials with lithium battery materials as the core technology are introduced, and the current problems and improvements in this field are highlighted.
Key words: lithium-ion batteries; electrode materials, electric cycling capacity, lithium embedded compounds.
Introduction The electronic information age has rapidly increased the demand for mobile power. Lithium-ion batteries offer the important advantages of high voltage and high capacity, as well as long cycle life and good safety performance.
They have promising applications in portable electronic devices, electric vehicles, aerospace technology, defense industry, etc. It is a research hotspot that has received wide attention this year. The general analysis of the mechanism of lithium-ion battery considers that lithium-ion battery as a chemical power source is a secondary battery consisting of two compounds that reversibly embed and de-embed lithium ions as the positive and negative electrodes.
When the battery is charged, lithium ions are de-embedded from the positive electrode and inserted into the negative electrode, and vice versa. Lithium-ion batteries are a product of physics, materials science and chemistry. The physical mechanisms involved in lithium-ion batteries are currently explained by the physics of embedding in solid state physics. Intercalation is the reversible embedding of a mobile guest particle (molecule, atom, ion) into a host lattice of appropriate size. Click on the space in the network.
The positive and negative materials for electron transport lithium-ion batteries are a mixture of ion- and electron-embedded compounds. Electrons can only move through the positive and negative materials [4] [5] [6]. There are many different known intercalation compounds and the guest particles can be molecules, atoms or ions. When inserting ions, charge compensation from the host structure is required to maintain electrical neutrality. Charge compensation can be achieved by changing the energy band structure of the host material, and the conductivity will change before and after embedding. Whether the electrode material of Li-ion battery can be stable in air is closely related to this property. If the embedded compounds satisfy reversible structural changes and can compensate for the change of charge in the structure, they can only be used as electrode materials for lithium-ion batteries.
The key materials that control the performance of lithium-ion batteries - the cathode and anode active materials in the battery - are the key to this technology, and this is the consensus of researchers at home and abroad. 1 The properties of cathode materials and general preparation methods An important parameter characterizing the ion transport performance in the cathode is the chemical diffusion coefficient. Usually, the diffusion coefficient of lithium ions in the cathode active material is low. Lithium is inserted into or de-embedded from the cathode material together with the crystal phase transition.
Therefore, very thin electrode films, typically tens of microns, are required for lithium-ion batteries. The lithium embedding compound of the cathode material is a temporary holding container for the lithium ions in the lithium ion battery. In order to obtain higher cell voltages, lithium-embedded compounds with high potentials are preferably selected. The cathode material should meet.
1) Electrochemical compatibility with the electrolyte in the desired range of charging and discharging potentials.
2) mild electrode process kinetics.
3) highly reversible.
4) fully lithiated stability in air.
Research hotspots have focused on layered LiMO2 and spinel LiM2O4 compounds and similar electrode materials with two M (M for Co, Ni, Mn, V and other transition metal ions). As the cathode material for lithium-ion batteries, the extent and reversibility of structural changes during the deembedding and embedding of Li + ions determine the stable and repeated charging and discharging of the battery. In the preparation of cathode materials, the raw material properties and synthesis process conditions will have an impact on the final structure. Various promising cathode materials decay in capacity during use, which is a major issue in research.
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